ONSEMI NCP1910

NCP1910
High Performance Combo
Controller for ATX Power
Supplies
Housed in a SO−24WB package, the NCP1910 combines a
state−of−the−art circuitry aimed to powering next generation of ATX
or flat TVs converters. With a 65 kHz Continuous Conduction Mode
Power Factor Controller and a LLC controller hosting a high−voltage
driver, the NCP1910 is ready to power 85+ types of offline power
supplies. To satisfy stringent efficiency considerations, the PFC circuit
implements an adjustable frequency fold back to reduce switching
losses as the load is going light. To cope with all the signal sequencing
required by the ATX and flat TVs specifications, the controller
includes several dedicated pins enabling handshake between the
secondary and the primary sides. These signals include a power−good
line but also a control pin which turns the controller on and off via an
opto coupler. Safety−wise, a second OVP input offers the necessary
redundancy in case the main feedback network would drift away.
Finally, a fast fault input immediately reacts in presence of an over
current condition by triggering an auto−recovery soft−start sequence.
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SO−24WB Less Pin 21
DW SUFFIX
CASE 752AB
MARKING DIAGRAM
NCP1910XXX
AWLYYWWG
1
XXXXX
A
WL
YY
WW
G
Features
•
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•
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= Specific Device Code
= Assembly Location
= Wafer Lot
= Year
= Work Week
= Pb−Free Package
Fixed−Frequency 65 kHz CCM Power Factor Controller
Average Current−Mode Control for Low Line Distortion
Dynamic Response Enhancer Reduces Bulk Undershoot
ORDERING INFORMATION
See detailed ordering and shipping information in the package
Independent Over Voltage Protection Sensing Pin with Latch−off
dimensions section on page 36 of this data sheet.
Capability
Adjustable Frequency Fold Back Improves Light Load Efficiency
Adjustable Line Brown−out Protection with 50 ms
• on/off Control Pin for Secondary−Based Remote
Delay to Help Meeting Hold−up Time Specifications
Control
Programmable Over current Threshold Leads to an
• On−Board 5 V Reference Voltage for Precise
Optimized Sensing Resistor
Thresholds/Hysteresis Adjustments
±1 A peak Current Drive Capability
• Power Good Output Management Signal
LLC Controller Operates from 25 kHz to 500 kHz
• A Version with Dual Ground Pinout (No Skip),
B Version with Single Ground and Skip Operation for
On Board 600 V High−Voltage Drivers
the LLC Controller
1 A/0.5 A Sink/Source Capability
•
20 V Operation
Minimum Frequency Precision Down to ±3% Over
• These are Pb−Free Devices
Temperature Range
• Internally Fixed Dead−Time Value of 300 ns
• Adjustable Soft−Start Sequence
• Fast Fault Input with Soft−Start Trigger for Immediate
Typical Applications
• Multi Output ATX Power Supplies (A version)
• Flat TVs Power Supplies (B version)
Auto−Recovery Protection
© Semiconductor Components Industries, LLC, 2012
December, 2012 − Rev. 1
1
Publication Order Number:
NCP1910/D
NCP1910
SS
Rt
PG out
ON/OFF
BO adj.
Vref
PG adj.
OVP2
FB
VCTRL
VM
LBO
1
24
Vboot
MU
Bridge
ML
VCC
DRV
GND/PGND
Skip/AGND
CS/FF
CS
Fold
Figure 1. Pin Connections
PIN DESCRIPTION
Pin N5
Pin Name
Function
Pin Description
1
SS
Soft−start
2
Rt
The LLC feedback pin
A resistive arrangement sets the maximum and minimum
switching frequencies with opto coupler−based feedback
capabilities.
3
PG out
The open−collector power good signal
This pin is low when Vbulk is ok, opens when Vbulk passes
below a level adjusted by PGadj pin.
4
on/off
Remote control
5
BO adj.
Brown−out adjustment
This pin sets the on and off levels for the PFC powering the
LLC converter
6
Vref
The 5 V reference pin
This pin delivers a stable voltage for threshold adjustments
7
PG adj.
The power good trip level
From the Vref pin, a dc level sets the trip point for the PFC
bulk voltage at which the PG out signal is down.
8
OVP2
Redundant OVP
A fully latched OVP monitoring the PFC bulk independently
from FB pin.
9
FB
PFC feedback
10
VCTRL
PFC Error amplifier output
11
VM
PFC current amplifier output
12
LBO
PFC line input voltage sensing
13
Fold
PFC fold back
14
CS
PFC current sense
15
CS/FF
Fast−fault input
When pulled above 1 V, the LLC stops and re−starts via a full
soft−start sequence.
16
Skip/AGND
Skip (B)/AGND (A)
This pin is either used as the analog GND for the signal circuit
(A) or for skip operation (B).
17
GND/PGND
GND (B)/PGND (A)
The controller ground for the driving loop (A) or the lump
ground pin for all circuits (B)
18
DRV
PFC drive signal
19
VCC
The controller supply
The power supply pin for the controller, 20 V max.
20
ML
Lower−side MOSFET
Drive signal for the lower side half−bridge MOSFET
22
Bridge
Half−bridge
23
MU
Upper−side MOSFET
24
Vboot
Bootstrapped Vcc
A capacitor to ground sets the LLC soft−start duration
When pulled low, the circuit operates: the PFC starts first and
once FB is in regulation, the LLC is authorized to work. When
left open, the controller is in idle mode.
Monitors the boost bulk voltage and regulates it. It also serves
as a quick auto−recovery OVP
PFC error amplifier compensation pin
A resistor to ground sets the maximum power level
Line feed forward and PFC brown−out
This pin selects the power level at which the frequency starts
to reduce gradually.
This pin senses the inductor current and also programs the
maximum sense voltage excursion
The driving signal to the PFC power MOSFET
This pin connects to the LLC half−bridge
Drive signal for the upper side half−bridge MOSFET
The bootstrapped VCC for the floating driver
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2
3
Input
Line
V32
V33
D7
D3
D8
D4
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(*)
(*)
R20
10k
X3
R19
10
Q1
D10
D2
C1
FB
U2A
Bulk
C18
1n
R12
R22
on/off
Power
Good
U3A
C9
1u
R13
R15
BO level
C16
0.1u
R21
Vref
R5
3.5M
C17
1n
0.1u
C6
Vref
C8
R23
0.22u 120k
R25
24k
PG adj.
R14
R6
C2
R1
3.5M
R32
3.6k
R24
24k
22
3
19
12
R27
39k
C11
1n
R33
1.2k
13 R34
8.4k
14
16
15
9
10
11
17
18
8
7
6
5
20
23
4
24
1
C10
0.1u
U100
2
R7
2.2M
R3
1.5M
R26
24k
R4
2.2M
R2
1.5M
D5
Vcc
C12
C3
R28
C13
Over Current
12 V aux.
R8
R16
R17
D11
R9
M2
M1
D12
C15
R29
L2
T1
.
.
C14
.
D9
D6
C4
Figure 2. Typical Application Schematic in A Version
R10
U1
U2B
*It is recommended to separate the traces of power ground and analog ground. The power ground (pin 17) for driving loop (PFC DRV and LLC ML) is connected to the PFC MOSFET directly. The analog ground for adjustment components is routed together first and then connected to the analog ground pin (pin
16) and the PFC sense resistor directly.
R35
300
R31
0.1
C5
L1
D1
C7
R18
R30
R11
Vout
X2
PAD2
NCP1910
4
Input
Line
V32
V33
D7
D3
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R35
300
R31
0.1
C5
(*)
(*)
R20
10k
X3
Q1
D10
D2
R19
10
FB
U2A
C1
Bulk
R36
C19
C18
1n
R12
on/off
R22
Power
Good
U3A
C9
1u
R13
R15
BO level
C16
0.1u
R21
Vref
C8
R23
0.22u 120k
R25
24k
PG adj.
R5
3.5M
C17
1n
C6
0.1u
R14 Vref
R6
C2
R1
3.5M
R32
3.6k
R24
24k
R4
2.2M
R2
1.5M
R26
24k
15
C10
0.1u
12
R27
39k
13
14
10
11
16
17
18
19
20
9
8
7
6
5
21
4
23
24
22
U100
3
2
1
R7
2.2M
R3
1.5M
C11
1n
R33
1.2k
R34
8.4k
skip
D5
Vcc
C12
C3
R28
C13
Over Current
12 V aux.
R8
R16
R9
D11
R17
M2
M1
D12
C15
R29
L2
C14
T1
.
. .
D9
D6
C4
U1
U2B
R10
C7
R18
Figure 3. Typical Application Schematic in B Version
*It is recommended to separate the traces of power ground and analog ground. The analog ground traces for adjustment components are routed together first and then
connected to the ground pin (pin 17). The power ground for driving loop (PFC DRV and LLC ML) is connected from ground pin (pin 17) to the PFC sense resistor directly
and as short as possible.
D8
D4
L1
D1
R30
R11
X2
PAD2
Vout
NCP1910
NCP1910
Grand Reset
PFC_BO
107% Vpref
+
“1” OVP2, “0” = ok
Latched adjustable OVP2
−
PFC_OVP2
latched
VOVP2
PFC_OVP
Auto−recovery internal OVP
+
“1” = UVP, “0” ok
Vctrl
PFC_UVP
VDD
−
+
−
Grand
Reset
+
FB
8% Vpref
−
Vctrl(min) − 0.1 V
PFC_BO
IVLD
PFC_OPL
Q
Q
1 sec
delay
PFCflag
−
RFB
pull down
VOVP
VUVP
PFC_abnormal
latched
S
Vctrl(max)
“1” OVP, “0” = ok
+
+
105% Vpref
R
−
OVP2
20 us filter
PFC_BO
Latch
Grand Reset
If PFC issues an abnormal
situation, then latch off
PFC_OK
Dynamic
Response
Enhancer
“1” = below 5% reg
“0” ok
−
S
Grand Reset
PFC_BO
Closed
if “1”
−
OTA
PFC drive signal
−
“1” = FB > Vpref
+
Vfold
“1” open
“0” close
Vfold(max)
Ict(fold)
Grand Reset
PFC_BO
VCTRL
VLBO
“1” BO NOTOK,
Vctrl(min)
“0” BOK
PFC_BO
BO delay
VLBOT
+
−
LBO
S
Q
Q
S
R
ILBO
Q
Q
R
PFC_OK
A
Latch
Onoff
UVLO
TSD
PFC_SKIP
PFC_OL
PFC_OVP
PFC_BO
VLBO^2
B
VDD Multiplier
−
ICt(min)
ICt
A/B
B
ICS x VLBO^2
VLBO2
4(Vctrl * Vctrl(min))
+
ICS
ICS
K1
Vctrl−Vctrl(min)
Vdd
−
B
A
Vpref
SUM 2 K2
CS
+
VLBO^2
ICS
foldback
ICS
PFC_OK
Vctrl
+
Vpref
Q
Q
+
VLD
95% Vpref
R
PFC_SKIP
(0.6 V clamp
voltage is
activated.)
A
ICS x VLBO > 275 uA
+
“1” = OPL
−
ICS > 200 uA
+
−
“0” / “1”
Vpref / 10%Vpref
PFC_OPL
Oscillator section
PFC_OL
“1” = OCP
PFC_OCP
VM
Vcc
DRV
Figure 4. Internal PFC Block Diagram
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5
The “PFC_OK” toggles high when:
− VLD is low
− PFC issues a driving pulse
The “PFC_OK” toggles low when:
− Vctrl stays out of window [Vctrl,min to
Vctrl,max] > 1 sec
− at this point, the latch is reset and the
“PFC_OK” output goes low.
NCP1910
Vrt
Vboot
Q
S
D
+
Q
Clk Q
-
Rt
S
CLK
R
QN
B
Mupper
A
R
UVLO
Hi side
Level
shifter
Latch
Vref
Vref
Bridge
Pulse
Trigger
Latch
Grand
Reset
Dead time
B
Vcc
UVLO
Grand
Reset
Vdd
Vcc
management
A
BO adj
"1" BONOT OK
+
-
Mlower
delay
LLC_BO
tBOK
tBONOTOK
Prop. delay
matching
PFC_FB
GND_LLC
PFC_OK
"1" is ok
"0" notok
"1" PGNOT OK
"1" enables LLC
"0" LLC is locked
+
PG adj
Skip: B version only
LLC_BO
Skip/GND_PFC
+
LLC_PG
20 ms delay
tdel1
Grand
Reset
R
Vskip
LLC_BO
PG out
R
5 ms delay
tdel2
GND
Grand Reset
Grand
Reset
"1" after reset
"0" when PG out
drops after 5 ms
PFC_OVP2
SS
+
S
-
S
Q
Q
Q
Latch
Q
S
VCS2
R
CS/FF
+
Q
R
Grand Reset
Q
PFC_BO
R
LLC_PG
-
Grand Reset
VCS1
+
SS_RST
Vdd
Rpull up
on_off
UVLO
on/off
"1" controller is off
"0" controller is on
Grand Reset
PFC_UVP
on/off
Onoff
Thermal
Shut Down
TSD
"1" TSD is on
"0" TSD is off
TSD
Figure 5. Internal LLC Block Diagram
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6
NCP1910
MAXIMUM RATINGS TABLE
Symbol
VBridge
Rating
Value
Unit
−1 to 600
V
−0.3 to 20
V
High side output voltage, pin 23
VBRIDGE − 0.3 to
VBOOT + 0.3
V
Low side output voltage, pin 18, 20
−0.3 to VCC + 0.3
V
Allowable output slew rate on the Bridge pin, pin 22
50
V/ns
Power Supply voltage, pin 19
20
V
−0.3 to 10
V
Continuous High Voltage bridge pin, pin 22
VBOOT–VBridge Floating supply voltage, pin 24−22
VMU, VDRV
VML
dVBridge/dt
VCC
Pin voltage, all pins (except pin 2, 6, 18 − 24, GND)
RθJA
Thermal Resistance Junction−to−Air
50 mm2, 1 oz
650 mm2, 1 oz
Storage Temperature Range
−60 to + 150
°C
2
kV
200
V
ESD Capability, Human Body Model (All pins except VCC and HV)
ESD Capability, Machine Model
VCC
°C/W
80
65
Power Supply voltage, pin 19
20
V
Pin voltage, all pins (except pin 2, 6, 18 ~ 24, GND)
−0.3 to 10
V
VRt
Rt pin voltage
−0.3 to 5
V
Vref_out
Vref pin voltage
−0.3 to 7
V
0.5
mA
5
mA
IMAX
Pin current on pin 10, 12, and 13
IPGout
Pin current on pin 3
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
1. This device(s) contains ESD protection and exceeds the following tests:
Human Body Model 2000 V per JEDEC Standard JESD22−A114E
Machine Model 200 V per JEDEC Standard JESD22−A115−A
2. This device contains latch−up protection and exceeds 100 mA per JEDEC Standard JESD78.
ELECTRICAL CHARACTERISTICS (For typical values TJ = 25°C, for min/max values TJ = −40°C to +125°C, Max TJ = 150°C,
VCC = 12 V unless otherwise noted)
Rating
Pin
Min
Typ
Max
Unit
VCC(on)
Turn−on threshold level, VCC going up
19
9.4
10.4
11.4
V
VCC(min)
Minimum operating voltage after turn−on
19
8
9
10
V
VCC(Hys)
Hysteresis between VCC(on) and VCC(min)
19
1.2
−
−
V
VBoot(on)
Startup voltage on the floating section
24,22
7.8
8.8
9.8
V
VBoot(min)
Cutoff voltage on the floating section
Symbol
COMMON TO BOTH CONTROLLERS
SUPPLY SECTION
24,22
7
8
9
V
Startup current, VCC < VCC(on)
19
−
−
100
mA
ICC1
PFC consumption alone, DRV pin unloaded, on/off pin grounded,
LLC off (PFC is 65 kHz)
19
−
5.1
6.4
mA
ICC2
PFC consumption, DRV pin loaded by 1 nF, on/off pin grounded, LLC
off (PFC is 65 kHz)
19
−
5.9
7.4
mA
Istartup
3. In normal operation, when the power supply is un−plugged, the bulk voltage goes down. At a first crossed level, the PG pin opens. Later,
when the bulk crosses a second level, the LLC turns off. There is no timing link between these events, except the bulk capacitor discharge
slope. However, if for an unknown reason the PFC is disabled (fault, short−circuit), the PG pin immediately opens and if sufficient voltage
is still present on the bulk (e.g. in high line condition), the LLC will be disabled after a typical time of 5 ms.
4. Guaranteed by design.
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NCP1910
ELECTRICAL CHARACTERISTICS (For typical values TJ = 25°C, for min/max values TJ = −40°C to +125°C, Max TJ = 150°C,
VCC = 12 V unless otherwise noted)
Symbol
Rating
Pin
Min
Typ
Max
Unit
COMMON TO BOTH CONTROLLERS
SUPPLY SECTION
ICC4
IC consumption, both PFC and LLC loaded in no load conditions
(PFC is 65 kHz and Rt = 70 kW (LLC is 25 kHz))
19
−
5.9
7.2
mA
ICC5
IC consumption, both PFC and LLC loaded 1 nF load conditions
(PFC is 65 kHz and Rt = 70 kW (LLC is 25 kHz))
19
−
6.9
8.6
mA
ICC6
IC consumption in fault mode from Vboot (drivers disabled, Vboot >
Vboot(min))
19
−
64
300
mA
ICC7
IC consumption in OFF mode from VCC (on/off pin is open)
19
−
−
950
mA
REFERENCE VOLTAGE
Vref−out
Reference voltage for external threshold setting @ Iout = 5 mA
6
4.75
5
5.25
V
Vref−out
Reference voltage for external threshold setting @ Iout = 5 mA – TJ =
25°C
6
4.9
5
5.1
V
VrefLineReg
Vcc rejection capability, Iout = 5 mA − DVCC = 1 V – TJ = 25°C
6
−
0.01
5
mV
VrefLoadReg
Reference variation with load changes, 1 mA < Iref < 5 mA – TJ =
25°C
6
−
1.6
7
mV
Maximum output current capability
6
5
−
−
mA
Iref−out
NOTE:
Maximum capacitance directly connected to VREF pin must be under 100 nF.
DELAY
tDEL1
Turn−on LLC delay after PFC OK signal is asserted
−
10
20
30
ms
tDEL2
Turn−off LLC after power good pin goes low (Note 3)
−
2
5
8
ms
on/off pin pull−up resistor
4
−
5
−
kW
ton/off
Propagation delay from on to off (ML & MU are off) (Note 4)
4
−
−
1
ms
Von
Low level input voltage on on/off pin (NCP1910 is enabled)
4
−
−
1
V
Voff
High level input voltage on on/off pin (NCP1910 is disabled)
4
3
−
−
V
Vop
Open voltage on on/off pin
4
−
7
−
V
IPG
Maximum Power good pin sink current capability
3
5
−
−
mA
VPG
Power good saturation voltage for IPG = 5 mA
3
−
−
350
mV
Input bias current, PGadj pin
7
−
10
−
nA
PG comparator hysteresis
7
−
100
−
mV
Temperature shutdown (Note 4)
−
140
−
−
°C
Temperature Hysteresis Shutdown
−
−
30
−
°C
PROTECTIONS
RPull−up
IPGadj
VPGadjH
TSD
TSDhyste
POWER FACTOR CORRECTION
GATE DRIVE SECTION
RPOH
Source Resistance @ IDRV = −100 mA
18
−
9
20
W
RPOL
Sink Resistance @ IDRV = 100 mA
18
−
6.6
18
W
tPr
Gate Drive Voltage Rise Time from 1.5 V to 10.5 V (CL = 1 nF)
18
−
60
−
ns
tPf
Gate Drive Voltage Fall Time from 10.5 V to 1.5 V (CL = 1 nF)
18
−
40
−
ns
3. In normal operation, when the power supply is un−plugged, the bulk voltage goes down. At a first crossed level, the PG pin opens. Later,
when the bulk crosses a second level, the LLC turns off. There is no timing link between these events, except the bulk capacitor discharge
slope. However, if for an unknown reason the PFC is disabled (fault, short−circuit), the PG pin immediately opens and if sufficient voltage
is still present on the bulk (e.g. in high line condition), the LLC will be disabled after a typical time of 5 ms.
4. Guaranteed by design.
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8
NCP1910
ELECTRICAL CHARACTERISTICS (For typical values TJ = 25°C, for min/max values TJ = −40°C to +125°C, Max TJ = 150°C,
VCC = 12 V unless otherwise noted)
Symbol
Rating
Pin
Min
Typ
Max
Unit
PFC Voltage reference
−
2.425
2.5
2.575
V
IEA
Error Amplifier Current Capability
10
−
$30
−
mA
GEA
Error Amplifier Gain
−
100
200
300
mS
Bias Current @ VFB = VPREF
9
0
−
0.3
mA
Maximum Control Voltage @ VFB = 2 V
Minimum Control Voltage @ VFB = 3 V
DVCTRL = VCTRL(max)−VCTRL(min)
10
10
10
−
−
2.7
3.6
0.6
3
−
−
3.3
VOUTL / VPREF
Ratio (VOUT Low Detect Threshold / VPREF) (Note 4)
−
94
95
96
%
HOUTL / VPREF
Ratio (VOUT Low Detect Hysteresis / VPREF)
−
−
0.5
−
%
Source Current when (VOUT Low Detect) is activated
10
190
230
260
mA
Current Sense Pin Offset Voltage, (ICS = 100 mA)
14
−
10
−
mV
Over−Current Protection Threshold
14
185
200
215
mA
ICSx VLBO
Over Power Limitation Threshold
−
215
275
335
mVA
ICS(OPL1)
ICS(OPL2)
Over−Power Current Threshold (VLBO = 1.8 V, VM = 0 V)
Over−Power Current Threshold (VLBO = 3.6 V, VM = 0 V)
−
119
56
153
75
187
99
mA
PFC Switching Frequency
18
58
65
72
kHz
Minimum Switching Frequency (Vfold = 1.5 V, VCTRL = VCTRL(min) +
0.1 V)
18
34
39
43
kHz
DCPmax
Maximum PFC Duty Cycle
18
−
97
−
%
DCPmin
Minimum PFC Duty Cycle
18
−
−
0
%
VCTRL pin voltage to start frequency foldback (Vfold = 1.5 V)
10
1.8
2
2.2
V
VCTRL pin voltage as frequency foldback reducing to the minimum
(FPSW = FPSW(fold), Vfold = 1.5 V)
10
1.4
1.6
1.8
V
Maximum internal fold voltage (Note 4)
−
1.97
2
2.03
V
POWER FACTOR CORRECTION
REGULATION BLOCK
VPREF
IB
VCTRL
VCTRL(max)
VCTRL(min)
DVCTRL
IVLD + IEA
V
CURRENT SENSE
VS
ICS(OCP)
POWER LIMIT
PULSE WIDTH MODULATION
FPSW
FPSW(fold)
VCTRL(fold)
VCTRL(foldend)
Vfold(max)
LINE BROWN−OUT DETECTION
VLBOT
Line Brown−Out Voltage Threshold
12
0.96
1.00
1.04
V
ILBOH
Line Brown−Out Hysteresis Current Source
12
6
7
8
mA
Line Brown−Out Blanking Time
−
25
50
75
ms
tLBO(window)
tLBO(blank)
Line Brown−Out Monitoring Window (Note 4)
−
25
50
75
ms
VLBO(clamp)
LBO Pin clamped voltage if VBO < VLBOT during tLBO(BLANK) (ILBO =
100 mA)
12
−
980
−
mV
Hysteresis (VLBOT – VLBO(clamp)) (Note 4)
12
10
35
60
mV
ILBO(clamp)
Current Capability of LBO
12
100
−
−
mA
VLBO(PNP)
LBO pin voltage when clamped by the PNP Transistor (ILBO =
100 mA)
12
0.4
0.7
0.9
V
VLBOH
3. In normal operation, when the power supply is un−plugged, the bulk voltage goes down. At a first crossed level, the PG pin opens. Later,
when the bulk crosses a second level, the LLC turns off. There is no timing link between these events, except the bulk capacitor discharge
slope. However, if for an unknown reason the PFC is disabled (fault, short−circuit), the PG pin immediately opens and if sufficient voltage
is still present on the bulk (e.g. in high line condition), the LLC will be disabled after a typical time of 5 ms.
4. Guaranteed by design.
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NCP1910
ELECTRICAL CHARACTERISTICS (For typical values TJ = 25°C, for min/max values TJ = −40°C to +125°C, Max TJ = 150°C,
VCC = 12 V unless otherwise noted)
Symbol
Rating
Pin
Min
Typ
Max
Unit
Pull Down VLBO Threshold
12
1.8
2
2.2
V
Pull Down VLBO Time Limitation
−
4.5
5
6.1
ms
Time Delay to Confirm that VCTRL is the maximum to Pull down VLBO
−
2.5
5
7.5
ms
Pull Down VLBO Blanking Time
−
55
77
90
ms
11
46
58
72
mA
11
15
19
24.5
POWER FACTOR CORRECTION
LINE BROWN−OUT DETECTION
VLBO(PD)
tLBO(Pdlimit)
tPFCflag
tLBO(Pdblank)
CURRENT MODULATION
IM1
IM2
Multiplier Output Current (VCTRL =VCTRL(max) – 0.2 V , VLBO = 3.6 V,
ICS = 50 mA)
Multiplier Output Current (VCTRL =VCTRL(max) – 0.2 V , VLBO = 1.2 V,
ICS = 150 mA)
OVER−VOLTAGE PROTECTION
VOVP1
Internal Auto Recovery Over Voltage Threshold
9
2.536
2.615
2.694
V
VOVP1H
Hysteresis of Internal Auto Recovery Over Voltage Threshold
(Note 4)
9
−
44
60
mV
9, 18
−
500
−
ns
tOVP1
Propagation Delay (VFB = 108% VPREF) to Drive Low
VOVP2
External Latched Over Voltage Threshold
8
2.595
2.675
2.755
V
KOVPH
The difference between VOVP2 and VOVP1 over VPREF ((VOVP2 −
VOVP1)/VPREF)
−
−
2
−
%
External Latched OVP Integrating Filter Time Constant
−
−
20
−
ms
Input bias current, OVP2
8
−
10
−
nA
VUVP(on)/VPREF UVP Activate Threshold Ratio
9
4
8
12
%
VUVP(off)/VPREF UVP Deactivate Threshold Ratio
9
6
12
18
%
9
−
4
−
%
9 − 18
−
7
−
ms
−
1
1.5
2.1
sec
Minimum switching frequency, Rt = 70 kW on Rt pin
2
24.25
25
25.75
kHz
switching frequency, DTL = 300 ns, Rt = 7 kW on Rt pin
2
208
245
282
kHz
tDELOVP2
Ib,OVP2
UNDER−VOLTAGE PROTECTION
VUVP(H)
tUVP
UVP Lockout Hysteresis
Propagation Delay (VFB < 8 % VPREF) to Drive Low
PFC ABNORMAL
tPFCabnormal
PFC Abnormal Delay Time (VCTRL = VCTRL(max) or VCTRL =
VCTRL(min) – 0.1 V)
LLC CONTROL SECTION
OSCILLATOR
FLsw,min
FLsw
FLsw,max
2
424
500
575
kHz
23, 20
48
50
52
%
Reference voltage for oscillator charging current generation
2
3.33
3.5
3.67
V
Discharge switch resistance
1
−
70
−
W
Soft−start reset voltage
1
−
200
−
mV
Skip cycle threshold, B version only
16
350
400
450
mV
Hysteresis level on skip cycle comparator, B version only
16
−
50
−
mV
Maximum switching frequency, DTL = 300 ns, Rt = 3.5 kW on Rt pin
DCL
Operating Duty−Cycle symmetry
VrefRt
RSS
SSRST
VSkip
Vskip,hyste
3. In normal operation, when the power supply is un−plugged, the bulk voltage goes down. At a first crossed level, the PG pin opens. Later,
when the bulk crosses a second level, the LLC turns off. There is no timing link between these events, except the bulk capacitor discharge
slope. However, if for an unknown reason the PFC is disabled (fault, short−circuit), the PG pin immediately opens and if sufficient voltage
is still present on the bulk (e.g. in high line condition), the LLC will be disabled after a typical time of 5 ms.
4. Guaranteed by design.
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NCP1910
ELECTRICAL CHARACTERISTICS (For typical values TJ = 25°C, for min/max values TJ = −40°C to +125°C, Max TJ = 150°C,
VCC = 12 V unless otherwise noted)
Symbol
Rating
Pin
Min
Typ
Max
Unit
−
ns
LLC CONTROL SECTION
DRIVE OUTPUT
TLr
Output voltage rise−time @ CL = 1 nF, 10−90% of output signal
23, 20
−
40
TLf
Output voltage fall−time @ CL = 1 nF, 10−90% of output signal
23, 20
−
20
−
ns
RLOH
Source resistance
23, 20
−
12
26
W
RLOL
Sink resistance
23, 20
−
5
11
W
DTL
Dead time, measured between 50% of the rise and fall edge
23, 20
268
327
386
ns
22, 23, 24
−
−
5
mA
Input bias current, BOadj pin
5
−
15
−
nA
BO comparator hysteresis
5
−
100
−
mV
tBOK
BO comparator Integrating Filter Time Constant from High to Low
5
−
150
−
ms
tBONOTOK
BO comparator Integrating Filter Time Constant from Low to High
5
−
20
−
ms
VCS1
Current−sense pin level that resets the soft−start capacitor
15
0.95
1
1.05
V
VCS2
Current−sense pin level that permanently latches off the circuit
15
1.42
1.5
1.58
V
tCS
Propagation delay from VCS1/2 activation to respective action
15
−
−
500
ns
IHV,leak
Leakage current on high voltage pins to GND (600 Vdc)
PROTECTIONS
IBOadj
VBOadjH
3. In normal operation, when the power supply is un−plugged, the bulk voltage goes down. At a first crossed level, the PG pin opens. Later,
when the bulk crosses a second level, the LLC turns off. There is no timing link between these events, except the bulk capacitor discharge
slope. However, if for an unknown reason the PFC is disabled (fault, short−circuit), the PG pin immediately opens and if sufficient voltage
is still present on the bulk (e.g. in high line condition), the LLC will be disabled after a typical time of 5 ms.
4. Guaranteed by design.
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NCP1910
TYPICAL CHARACTERISTICS
10
10
9.5
VCC(min)
9
8.5
8
−50
Istartup (mA)
Vboot(on) AND Vboot(min) (V)
VCC(on)
10.5
−25
0
25
50
75
100
9.5
Vboot(on)
9
8.5
Vboot(min)
8
7.5
7
−50
125
−25
0
25
50
75
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 6. VCC(on) and VCC(min) vs. Temperature
Figure 7. Vboot(on) and Vboot(min) vs.
Temperature
100
950
75
850
ICC7 (mA)
VCC(on) AND VCC(min) (V)
11
50
750
650
25
0
−50
125
−25
0
25
50
75
100
550
−50
125
−25
0
25
50
75
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 8. Istartup vs. Temperature
Figure 9. ICC7 vs. Temperature
5.25
100
125
4.99
Vref−out @ 25°C (V)
Vref−out (V)
5.15
5.05
4.95
4.989
4.988
4.85
4.75
−50
−25
0
25
50
75
100
4.987
125
0
1
2
3
4
5
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 10. Vref-out vs. Temperature
Figure 11. Vref-out @ 255C vs. Iref-out
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6
NCP1910
TYPICAL CHARACTERISTICS
10
Voff
2.5
RPOH AND RPOL (W)
Von AND Voff (V)
3
2
Von
1.5
1
−50
−25
0
25
50
75
TEMPERATURE (°C)
100
8
RPOL
4
2
−50
125
0
75
100
125
−25
IEA(source) (mA)
VOVP2
VOVP1
2.6
VPREF
2.5
−25
0
25
50
−30
−35
75
100
−40
−50
125
−25
0
TEMPERATURE (°C)
25
50
75
100
125
TEMPERATURE (°C)
Figure 14. VPREF, VOVP1, and VOVP2 vs.
Temperature
Figure 15. IEA(source) vs. Temperature
40
300
35
250
GEA (mS)
IEA(sink) (mA)
50
−20
2.7
30
25
20
−50
25
Figure 13. RPOH and RPOL vs. Temperature
2.8
VPREF, VOVP1, AND VOVP2 (V)
−25
TEMPERATURE (°C)
Figure 12. Von and Voff vs. Temperature
2.4
−50
RPOH
6
200
150
−25
0
25
50
75
100
100
−50
125
−25
0
25
50
75
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 16. IEA(sink) vs. Temperature
Figure 17. GEA vs. Temperature
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13
100
125
NCP1910
3.9
3.3
3.8
3.2
3.7
3.1
DVCTR (V)
VCTR(max) (V)
TYPICAL CHARACTERISTICS
3.6
3.5
2.9
2.8
3.4
3.3
−50
3
−25
0
25
50
75
100
2.7
−50
125
0
25
50
75
100
TEMPERATURE (°C)
Figure 18. VCTRL(max) vs. Temperature
Figure 19. DVCTRL vs. Temperature
260
215
250
210
ICS(OCP) (mA)
IVLD + IEA (mA)
240
230
220
210
125
205
200
195
190
200
190
−50
−25
TEMPERATURE (°C)
−25
0
25
50
75
100
185
−50
125
−25
0
25
50
75
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 20. IVLD+IEA vs. Temperature
Figure 21. ICS(OCP) vs. Temperature
190
125
95
180
85
ICS(OPL2) (mA)
ICS(OPL1) (mA)
170
160
150
140
75
65
130
120
−50
−25
0
25
50
75
100
55
−50
125
TEMPERATURE (°C)
−25
0
25
50
75
100
TEMPERATURE (°C)
Figure 22. ICS(OPL1) vs. Temperature
Figure 23. ICS(OPL2) vs. Temperature
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14
125
NCP1910
TYPICAL CHARACTERISTICS
72
44
70
42
FPSW(fold) (kHz)
FPSW (kHz)
68
66
64
62
40
38
36
60
58
−50
−25
0
25
50
75
100
34
−50
125
−25
0
50
75
100
125
Figure 25. FPSW(fold) vs. Temperature
1.04
8
1.02
7.5
ILBOH (mA)
VLBOT (V)
Figure 24. FPSW vs. Temperature
1
0.98
7
6.5
0.96
−50
−25
0
25
50
75
100
125
6
−50
−25
0
TEMPERATURE (°C)
25
50
75
100
125
100
125
TEMPERATURE (°C)
Figure 26. VLBOT vs. Temperature
Figure 27. ILBOH vs. Temperature
18
26
16
25.5
14
VUVP(off) / VPREF
FLSW,min (kHz)
VUV(on) / VPREF AND VUP(off) / VPREF (%)
25
TEMPERATURE (°C)
TEMPERATURE (°C)
12
10
VUVP(on) / VPREF
8
25
24.5
6
4
−50
−25
0
25
50
75
100
125
24
−50
−25
0
25
50
75
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 28. VUVP(on)/VPREF and VUVP(off)/VPREF
vs. Temperature
Figure 29. FLsw,min vs. Temperature
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NCP1910
TYPICAL CHARACTERISTICS
280
525
270
500
FLSW,max (kHz)
FLSW (kHz)
260
250
240
230
475
450
220
210
−50
−25
0
25
50
75
100
425
−50
125
−25
0
TEMPERATURE (°C)
50
75
100
125
Figure 31. FLsw,max vs. Temperature
3.7
300
3.6
250
SSRST (mV)
VrefRT (V)
Figure 30. FLsw vs. Temperature
3.5
3.4
3.3
−50
25
TEMPERATURE (°C)
200
150
−25
0
25
50
75
100
100
−50
125
−25
0
TEMPERATURE (°C)
25
50
75
100
125
TEMPERATURE (°C)
Figure 33. SSRST vs. Temperature
Figure 32. VrefRt vs. Temperature
24
450
RLOH,ML AND RLOL,ML (W)
22
Vskip (mV)
425
400
375
20
18
RLOH,ML
16
14
12
10
8
RLOL,ML
6
4
350
−50
−25
0
25
50
75
TEMPERATURE (°C)
100
125
2
−50
Figure 34. Vskip vs. Temperature
−25
0
25
50
75
TEMPERATURE (°C)
100
Figure 35. RLOH,ML and RLOL,ML vs.
Temperature
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16
125
NCP1910
TYPICAL CHARACTERISTICS
340
24
20
330
18
RLOH,MU
16
DTL (ns)
RLOH,MU AND RLOL,MU (W)
22
14
12
10
8
310
RLOL,MU
6
320
4
2
−50
−25
0
25
50
75
100
300
−50
125
−25
0
TEMPERATURE (°C)
Figure 36. RLOH,MU and RLOL,MU vs.
Temperature
1.025
1.55
VCS2 (V)
1.6
VCS1 (V)
50
75
100
125
100
125
Figure 37. DTL vs. Temperature
1.05
1
0.975
1.5
1.45
−25
0
25
50
75
TEMPERATURE (°C)
100
125
1.4
−50
−25
Figure 38. VCS1 vs. Temperature
0
25
50
75
TEMPERATURE (°C)
Figure 39. VCS2 vs. Temperature
140
120
100
tCS (ns)
0.95
−50
25
TEMPERATURE (°C)
80
60
40
20
−50
−25
0
25
50
75
TEMPERATURE (°C)
Figure 40. tCS vs. Temperature
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100
125
NCP1910
APPLICATION INFORMATION
The NCP1910 represents a new generation of control
circuit, associating two individual cores performing the
functions of Continuous Conduction Mode (CCM) Power
Factor Correction (PFC) and LLC resonant control. These
cores interact together and implement handshake functions
in normal operating conditions but also when a fault appears.
Based on the ON Semiconductor proprietary high−voltage
technology, the LLC section can drive the high−side
MOSFET of the LLC half−bridge without the need of a
gate−drive transformer.
•
Power Factor Correction
• Compactness and Flexibility: the NCP1910 requires a
•
•
•
•
minimum of external components to perform a CCM
PFC operation. In particular, the circuit scheme
simplifies the PFC stage design. In addition, the circuit
offers some functions like the line brown−out detection
or true power limiting capability that enable the
optimization of the PFC design.
Low Consumption and Shutdown Capability: the
NCP1910 is optimized to consume a small current in all
operation modes. The consumed current is particularly
reduced during the start−up phase and in shutdown
mode so that the power losses are minimized when the
circuit is disabled. This feature helps meet stringent
stand−by low power specifications. Grounding the
Feed−back pin can force the circuit to enter standby but
the on/off pin can also serve this purpose.
Maximum Current Limit: the circuit permanently
senses the inductor current and immediately turns off
the power switch if it is higher than the set current
limit. The NCP1910 also prevents any turn on of the
power switch as long as the inductor current is not
below its maximum permissible level. This feature
protects the MOSFET from possible excessive stress
that could result from the switching of a current higher
than the one the power switch is dimensioned for. In
particular, this scheme effectively protects the PFC
stage during the start−up phase when large in−rush
currents charge the bulk capacitor.
Under−Voltage Protection for Open Loop
Protection: the circuit detects when the feed−back
voltage goes below than about 8% of the regulation
level. In this case, the circuit turns off and its
consumption drops to a very low value. This feature
protects the PFC stage from starting operation in case
of low ac line conditions or in case of a failure in the
feed−back network (i.e. bad connection). In case the
UVP circuitry is activated, the Power Good signal is
disabled and the LLC circuit stops immediately.
Fast Transient Response: given the low bandwidth of
the regulation block, the output voltage of PFC stages
may exhibit excessive over or under−shoots because of
•
•
•
•
•
•
abrupt load or input voltage variations (e.g. at start up).
If the bulk voltage is too far from the regulation level:
♦ Over−Voltage Protection: NCP1910 turns off the
power switch as soon as Vbulk exceeds the OVP
threshold (105% of the regulation level). This is an
auto−recovery function.
♦ Dynamic Response Enhancer: NCP1910
drastically speeds up the regulation loop by its
internal 200 mA current source, activated when the
bulk voltage drops below 95% of its regulation level.
Line Brown−Out Detection: the circuit detects low ac
line conditions and disables the PFC stage in this case.
This protection mainly protects the power switch from
the excessive stress that could damage it in such
conditions.
Over−Power Limitation: the NCP1910 computes the
maximum permissible current in dependence of the
average input voltage measured by the brown−out
block. It is the second OCP with a threshold that is line
dependent. When the circuit detects an excessive power
transfer, it resets the driver output immediately.
Redundant Over−Voltage Protection: As a redundant
safety feature, the NCP1910 offers a second latched
OVP whose input is available on OVP2 pin. If the
voltage on this pin is above the maximum allowable
voltage, the PFC and the LCC are latched off.
PFC Abnormal Protection: When PFC faces an
abnormal situation so that the bulk voltage is under
regulation longer than the allowable timing, the PFC
and LLC are latched off.
Frequency Foldback: in light output loading
conditions, the user has the ability to program a point
on the VCTRL pin where the oscillator frequency is
gradually reduced. This helps to maintain an adequate
efficiency on the PFC power stage alone.
Soft−Start: to offer a clean start−up sequence and limit
both the stress on the power MOSFET and the bulk
voltage overshoot, a 30 mA current source charges the
compensation network installed on VCTRL pin and
makes VCTRL raise gradually.
Output Stage Totem Pole: the NCP1910 incorporates
a ±1.0 A gate driver to efficiently drive TO220 or
TO247 power MOSFETs.
LLC Controller
• Wide frequency operation: the part can operate to a
frequency up to 500 kHz by connecting a resistive
network from Rt pin to ground. One resistor sets the
maximum switching frequency whereas a second
resistor set the minimum frequency.
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18
NCP1910
• On board dead time: to eliminate the shoot−through
•
•
•
•
on the half−bridge leg, a dead time is included in the
controller (see DTL parameter).
Soft−start: a dedicated pin discharges a capacitor to
ground upon start−up to offer a smooth output voltage
ramp up. The start−up frequency is the maximum set by
the resistor connected between Rt pin and SS pin. The
capacitor connected from Rt pin to ground fixes the soft
start duration. In fault mode, when the voltage on
CS/FF pin exceeds a typical value of 1 V, the soft−start
pin is immediately discharged and a re−start at high
frequency occurs.
Skip cycle operation: to avoid any frequency runaway
in light conditions but also to improve the standby
power consumption, the NCP1910B welcomes a skip
input (Skip pin) which permanently observes the
opto−coupler collector. If this pin senses a low voltage,
it cuts the LLC output pulses until the collector goes up
again. The NCP1910A does not offer the skip
capability and routes the analog ground on pin 16
instead.
High−voltage drivers: capitalizing on
ON Semiconductor technology, the LLC controller
includes a high−voltage section allowing a direct
connection to the high−voltage rail. The MOSFET leg
can therefore be directly driven without using a
gate−drive transformer.
Fault protection: as explained in the above lines, the
CS/FF pin combines a two−level protection circuit. If
the level crosses the first level (1 V), the LLC converter
immediately increases its switching frequency to the
maximum set by the external resistive divider
connected on Rt pin. This is an auto−recovery
protection mode. In case the fault is more severe, the
signal on the CS/FF pin crosses the second threshold
(1.5 V) and latches off the whole combo controller.
Reset occurs via an UVLO detection on VCC, a reset on
the on/off pin or a brown−out detection on the PFC
stage. This latter confirms that the user has unplugged
and re−plugged the power supply.
•
•
•
is asserted. This delay is always reset when the combo
is started from a Vcc ULVO, line brown−out condition
or via the on/off pin.
Power good signal: the power good signal (PG) is
intended to instruct the downstream circuitry installed
on the isolated secondary side that the combo is
working. Once the PFC has started, an internal
“PFC_OK” signal is asserted. 20 ms later, the PG pin is
brought low. This signal can now disappear in two
cases: the bulk voltage decreases to an abnormal level,
programmed by a reference voltage imposed on PGadj
pin. This level is usually above the LLC turn−off
voltage, programmed by BOadj pin. Therefore, in a
normal turn−off sequence, PG first drops and signals
the secondary side that it must be prepared for
shutdown. The second event that can drop the PG
signal is when the PFC experiences a fault: broken
feedback path, severe overload. In this case, the PG
signal is immediately asserted high and a 5 ms timer
starts. Once this timer is elapsed, the LLC converter can
be safely halted.
Latched event: in the event of a severe operating
condition, the PFC can be latched (OVP2 pin) and/or
the LLC controller also (CS/FF pin). In either case, the
whole combo controller is locked and can only be reset
via a VCC UVLO, line brown−out or a level transition
on pin on/off.
Thermal Shutdown: an internal thermal circuitry
disables the circuit gate drive and then keeps the power
switch off when the junction temperature exceeds
140°C typically. The circuit resumes operation once the
temperature drops below about 110°C (30°C
hysteresis).
Principle of NCP1910 Scheme
PFC Section
A CCM PFC boost converter is shown in Figure 41. The
input voltage is a rectified 50 Hz or 60 Hz sinusoidal signal.
The MOSFET is switching at a high frequency (typically
65 kHz in NCP1910) so that the inductor current IL basically
consists of high and low−frequency components.
Filter capacitor Cin is an essential and very small value
capacitor in order to eliminate the high−frequency
component of the inductor IL. This filter capacitor cannot be
too bulky because it can pollute the power factor by
distorting the rectified sinusoidal input voltage.
Combo Management
• Start−up delay: the PFC start−up sequence often
generates an output overshoot followed by damped
oscillations. To make sure the PFC output voltage is
fully stabilized before starting the LLC converter, a
20 ms delay is inserted after the internal PFC_ok signal
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NCP1910
I in
L
Bulk voltage (Vbulk)
IL
V in
C bulk
C in
R SENSE
Figure 41. CCM PFC Boost Converter
PFC Methodology
Vin is the rectified input voltage,
T is the switching period,
♦ t1 is the MOSFET on time, and
♦ t2 is the MOSFET off time.
The input filter capacitor Cin and the front−ended EMI
filter absorbs the high−frequency component of inductor
current IL. It makes the input current Iin a low−frequency
signal only of the inductor current.
♦
The NCP1910 uses a proprietary PFC methodology
particularly designed for CCM operation. The PFC
methodology is described in this section.
♦
I in + I L−50
(eq. 2)
Where:
Iin is the input AC current.
IL is the inductor current.
♦ IL−50 supposes a 50 Hz operation. The suffix 50
means it is with a 50 Hz bandwidth of the original
IL.
From Equations 1 and 2, the input impedance Zin is
formulated.
♦
♦
Figure 42. Inductor Current in CCM
As shown in Figure 42, the inductor current IL in a
switching period T includes a charging phase for duration t1
and a discharging phase for duration t2. The voltage
conversion ratio is obtained in Equation 1.
V bulk
V in
+
V in +
t1 ) t2
t2
T * t1
T
+
T
T * t1
Z in +
(eq. 1)
V in
I in
+
T * t 1 V bulk
T
I L*50
(eq. 3)
where: Zin is input impedance.
Power factor is corrected when the input impedance Zin in
Equation 3 is constant or varies slowly in the 50 or 60 Hz
bandwidth.
V bulk
Where:
♦ Vbulk is the output voltage of PFC stage,
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NCP1910
VPREF
VPREF
Figure 43. PFC Duty Modulation and Timing Diagram
The PFC modulation and timing diagram is shown in
Figure 43. The MOSFET on time t1 is generated by the
intersection of reference voltage VPREF and ramp voltage
Vramp. A relationship in Equation 4 is obtained.
V ramp + V M )
I cht 1
C ramp
+ V PREF
Z in +
I ch +
(eq. 4)
V M + V PREF *
t1
C rampV PREF
C ramp
T
+ V PREF
(eq. 7)
Figure 44. Multiplier Voltage Timing Diagram
(eq. 5)
T
V PREF I L−50
Because VPREF and Vbulk are roughly constant versus
time, the multiplier voltage VM is designed to be
proportional to the IL−50 in order to have a constant Zin for
PFC purpose. It is illustrated in Figure 44.
Where:
♦ Vramp is the internal ramp voltage, the positive input
of the PFC modulation comparator,
♦ VM is the multiplier voltage appearing on VM pin,
♦ Ich is the internal charging current,
♦ Cramp is the internal ramp capacitor, and
♦ VPREF is the internal reference voltage, the negative
input of the PFC modulation comparator.
Ich, Cramp, and VPREF also act as the ramp signal of
switching frequency. Hence the charging current Ich is
specially designed as in Equation 5. The multiplier voltage
VM is therefore expressed in terms of t1 in Equation 6.
C rampV PREF
V M V bulk
It can be seen in the timing diagram in Figure 43 that VM
originally consists of a switching frequency ripple coming
from the inductor current IL. The duty ratio can be
inaccurately generated due to this ripple. This modulation is
the so−called “peak current mode”. Hence, an external
capacitor CM connected to the multiplier voltage VM pin is
essential to bypass the high−frequency component of VM.
The modulation becomes the so−called “average current
mode” with a better accuracy for PFC.
T * t1
T (eq. 6)
From Equation 3 and Equation 6, the input impedance Zin
is re−formulated in Equation 7.
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NCP1910
R MI CSǒV LBOǓ 2
VM +
VM
ǒ
4 V CTRL * V CTRLǒminǓ
Ǔ
IM
11
CM
RM
PFC Duty
Modulation
Figure 45. The Multiplier Voltage Pin Configuration
The multiplier voltage VM is generated according to
Equation 8.
VM +
R MI CSǒV LBOǓ
VCTRL is the control voltage signal, the output
voltage of Operational Trans−conductance Amplifier
(OTA), as described in Equation 17.
♦ VCTRL(min) is not only the minimum operating
voltage of VCTRL but also the offset voltage for the
PFC current modulation.
RM directly limits the maximum input power capability.
Also, due to the Vin2 feed−forward feature, where the VLBO
is squared, the transfer function and the power delivery is
independent from the ac line level. The relationship between
VCTRL and power delivery will be depicted later on.
♦
2
(eq. 8)
4ǒV CTRL * V CTRL(min)Ǔ
Where:
♦ RM is the external multiplier resistor connected to
VM pin, which is constant.
♦ VLBO is the input voltage signal appearing on the
LBO pin, which is proportional to the rms input
voltage,
♦ ICS is the sense current proportional to the inductor
current IL as described in Equation 13.
Line Brown−Out Protection
Vin
Ac line
EMI
Filter
RSENSE
LBO comp.
RLBOU
Cin
LBO
CLBO
VLBOcomp
VLBOT
RLBOL
PFC_BO
S
Vdd
LBO Q
R
VLBO(clamp)
tLBO(blank)
reset
reset
tLBO(window)
reset
ILBOH
Figure 46. The Line Brown−Out Configuration
LBO pin voltage when a brown−out condition is detected.
This is for hysteresis purpose as required by this function.
In nominal operation, the voltage applied to LBO pin must
be above the internal reference voltage, VLBOT (1 V
typically). In this case, the output of the LBO comparator
VLBOcomp is low.
As shown in Figure 46, the Line Brown−Out pin
(represented LBO pin) as receives a portion of the input
voltage (Vin). As Vin is a rectified sinusoid, a capacitor must
integrate the ac line ripple so that a voltage proportional to
the average value of Vin is applied to the brown−out pin.
The main function of the LBO block is to detect too low
input voltage conditions. A 7 mA current source lowers the
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NCP1910
Conversely, if VLBO goes below 1 V, VLBOcomp turns high
and a 980 mV voltage source, VLBO(clamp), is connected to
the LBO pin to maintain the pin level near 1 V. Then a 50 ms
blanking delay, tLBO(blank), is activated during which no
fault is detected. The main goal of the 50 ms lag is to help
meet the hold−up requirements. In case of a short mains
interruption, no fault is detected and hence, both PFC and
LLC keep operating. In addition, LBO pin being kept at
980 mV, there is almost no extra delay between the line
recovery and the occurrence of a proper voltage applied to
LBO pin, that otherwise would exist because of the large
capacitor typically placed between LBO pin and ground to
filter the input voltage ripple. As a result, the NCP1910
effectively “blanks” any mains interruption that is shorter
than 25 ms (minimum guaranteed value of the 50 ms timer).
At the end of this blanking delay (tLBO(blank)), another
timer is activated that sets a 50 ms window during which a
fault can be detected. This is the role of the tLBO(window) in
Figure 46:
• If VLBOcomp is high during the second 50 ms delay
(tLBO(window)), a line brown−out condition is confirmed
and PFC_BO signal is asserted high.
• If VLBOcomp remains low for the duration of the
tLBO(window), no fault is detected.
R LBOL
V LBO + Ǹ2 V ac,rms
@
R LBOU ) R LBOL
R LBOU @ R LBOL
* I LBOH
R LBOU ) R LBOL
If RLBOL << RLBOU,
V LBO ] Ǹ2 V ac,rms
(eq. 9)
R LBOL
R LBOU ) R LBOL
* I LBOHR LBOL
• After the PFC stage has started operation, the input
voltage becomes a rectified sinusoid and the average
voltage becomes <Vin> = (2/p) √2 Vac,rms, which
decays 2/π of the peak value of rms input voltage.
Hence, the average voltage applied to LBO pin is:
<VLBO> = (2/p) √2 Vac,rms RLBOL/(RLBOU + RLBOL).
And because of the ripple on the LBO pin, the
minimum value of VLBO is around:
V LBO +
2Ǹ
2 V ac,rms
p
R
ǒ
R LBOL
LBOU ) R LBOL
f LBO
1*
(eq. 10)
Ǔ
3f line
Where:
♦ fLBO is the sensing network pole frequency.
When the PFC_BO signal is high:
• The PFC driver is disabled, and the VCTRL pin is
grounded to recover operation with a soft−start when
the fault has gone.
• The VLBO(clamp) voltage source is removed from LBO
pin.
• The ILBOH current source (7 mA typically) is enabled
that lowers the LBO pin voltage for hysteresis purpose.
At startup, a pnp transistor ensures that the LBO pin
voltage remains below when: VCC < UVLO or ON/OFF pin
is released open or UVP or Thermal Shutdown. This is to
guarantee that the circuit starts operation in the right state,
which is “PFC_BO” high. When the NCP1910 is ready to
work, the pnp transistor turns off and the circuit enables the
ILBOH.
Also, ILBOH is enabled whenever the part is in off mode,
but at startup, ILBOH is disabled until VCC reaches VCC(on).
f LBO +
R LBOU ) R LBOL
2pR LBOUR LBOLC LBO
♦ fline is the line frequency.
♦ RLBOL is low side resistor
of the dividing resistors
between LBO pin and ground.
♦ RLBOU is upper side resistor of the dividing resistors
between Vin and LBO pin.
f LBO of Equation 10 enables to take into
The term
1*
3f line
account the LBO pin voltage ripple (first approximation).
If as a rule of the thumb, we will assume that
f line .
f LBO +
10
Re−arranging the Equation 9 and 10, the network connected
to LBO pin can be calculated with the following equations:
ȡ 1
ȧ
Ȣ1 *
Line Brown−Out Network Calculation
R LBOL +
If the line brown−out network is connected to the voltage
after bridge diode, the monitored voltage can be very
different depending on the phase:
• Before operation, the PFC stage is off and the input
bridge acts as a peak detector. As a consequence, the
input voltage is approximately flat and nearly equates
the ac line amplitude: <Vin> = √2 Vac,rms, where Vac,rms
is the rms voltage of the line. As depicted in previous
section, the ILBOH turns on before PFC operates for the
purpose of adjustable line brown−out hysteresis; hence,
the average voltage applied to LBO pin is:
f
LBO
3f
^
ǒ
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ȣ
ȧ
Ȥ
V LBOT
p V ac,on
@
*1 @
2 V ac,off
I LBOH
line
(eq. 11)
Ǔ
V LBOT
p V ac,on
1
@ @
*1 @
0.967 2 V ac,off
I LBOH
R LBOU +
Where:
@
ǒ
Ǹ2 @ V
ac,on
I LBOHR LBOL ) V LBOT
Ǔ
(eq. 12)
* 1 R LBOL
NCP1910
♦
♦
PFC Over−Power Limitation (OPL)
Vac,on is the rms ac voltage to starts PFC operating.
Vac,off the rms ac voltage for line brown−out
detection.
This is a second OCP with a threshold that is line
dependent. Sense current ICS represents the inductor current
IL and hence represents the input current approximately.
Input voltage signal VLBO represents the rms input voltage.
The product (ICS x VLBO) represents an approximated input
power (IL x Vac). It is illustrated in Figure 48.
PFC Current Sense
IL
RCS
ICS CS
+
RSENSE
IL
Vin
NCP1910
IL
GND
VCS
−
RSENSE
Figure 47. PFC Current Sensing Configuration
RCS
The device senses the inductor current IL by the current
sense scheme in Figure 47. The device maintains the voltage
at CS pin to be zero voltage, i.e. VCS = 0 V, so that
I CS +
R SENSE
R CS
IL
RLBOU
R SENSE
+
R SENSE
CLBO
RLBOL
Figure 48. PFC Over−Power Limitation Configuration
When the product (ICS x VLBO) is greater than a
permissible level 275 mVA, the device turns off the PFC
driver so that the input power is limited. The OPL is
automatically deactivated when the product (ICS x VLBO) is
lower than the 275 mVA level. This 275 mVA level
corresponds to the approximated input power (IL x Vac) to
be smaller than the particular expression in Equation 15.
I CSV LBO t 275 mVA
PFC Over−Current Protection is reached when ICS is
larger than IS(OCP) (200 mA typical). The offset voltage of
the CS pin is typical 10 mV and it is neglected in the
calculation. Hence, the maximum OCP inductor current
threshold IL(OCP) is obtained in Equation 14.
I LǒOCPǓ +
OPL
> 275 mVA?
PFC Over−Current Protection (OCP)
R CS
Current
mirror
LBO
(eq. 13)
Where:
♦ RSENSE is the sense resistor to sense IL.
♦ RCS is the offset resistor between CS pin and
RSENSE.
This scheme has the advantage of the minimum number
of components for current sensing. The sense current ICS
represents the inductor current IL and will be used in the PFC
duty modulation to generate the multiplier voltage VM,
Over−Power Limitation (OPL), and Over−Current
Protection. Equation 13 would insist in the fact that it
provides the flexibility in the RSENSE choice and that it
allows to detect in−rush currents.
R CSI SǒOCPǓ
CS
ICS
ǒ
IL
Ǔ ǒ
R SENSE
2 Ǹ2 K LBO
R CS
p
I L @ V ac t
200 mA (eq. 14)
R CS @ p
R SENSE @ K LBO
@ V ac
Ǔ
(eq. 15)
t 275 mVA
@ 97 mVA
Where
When over−current protection threshold is reached, the
PFC drive goes low. The device automatically resumes
operation when the inductor current goes below the
threshold.
K LBO +
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R LBOL
R LBOU ) R LBOL
NCP1910
PFC Reference Section
V CTRL
The internal reference voltage (VPREF) is trimmed to be
±2% accurate over the temperature range (the typical value
is 2.5 V). VPREF is the reference used for the regulation of
PFC section.
V bulk
R FBL @ G EAR Z
R FBL ) R FBU
1 ) sR ZC Z
@
(eq. 17)
sR ZC Zǒ1 ) sR ZC PǓ
PFC Power Analysis and Vin2 Feed−Forward
From Equation 7 through 13, the input impedance Zin is
re−formulated in Equation 18.
PFC Feedback and Compensation
Z in +
Vbulk
Vin
+
2R MR SENSE @ K LBO 2 @ V ac 2 @ V bulkI L
ǒ
Ǔ
p 2R CS @ V CTRL * V CTRLǒminǓ @ V PREFI L−50
(eq. 18)
When IL is equal to IL−50, Equation 18 is re−formulated in
Equation 19.
RFBU
Z in +
FB
VPREF
OTA
VCTRL
RFBL
RZ
CP
To Multiplier of VM pin
Figure 49. VCTRL Type−2 Compensation
The output voltage Vbulk of the PFC circuits is sensed at
FB pin via the resistor divider (RFBL and RFBU) as shown in
Figure 49. Vbulk is regulated as described in Equation 16.
R FBU ) R FBL
R FBL
ǒ
Ǔ
p 2R CS @ V CTRL * V CTRLǒminǓ @ V PREF
(eq. 19)
The multiplier capacitor CM is the one to filter the
high−frequency component of the multiplier voltage VM.
The high−frequency component is basically coming from
the inductor current IL. On the other hand, the input filter
capacitor Cin similarly removes the high−frequency
component of inductor current IL. If the capacitors CM and
Cin match with each other in terms of filtering capability, IL
becomes IL−50. Input impedance Zin is roughly constant over
the bandwidth of 50 or 60 Hz and power factor is corrected.
Input and output power (Pin and Pout) are derived in
Equations 20 and 21 when the circuit efficiency η is
obtained or assumed. The variable Vac stands for the rms
input voltage.
VCTRL(min)
CZ
V bulk + V PREF
2R MR SENSE @ K LBO 2 @ V ac 2 @ V bulk
(eq. 16)
P in +
The feedback signal VFB represents the output voltage
Vbulk and will be used in the output voltage regulation,
Over−voltage protection (OVP), fast transient response, and
under−voltage protection (UVP)
The Operational Trans−conductance Amplifier (OTA)
constructs a control voltage, VCTRL, depending on the
output power and hence Vbulk. The operating range of
VCTRL is from VCTRL(min) to VCTRL(max). The signal used
for PFC duty modulation is after decreasing a offset voltage,
VCTRL(min), i.e. VCTRL−VCTRL(min).
This control voltage VCTRL is a roughly constant voltage
that comes from the PFC output voltage Vbulk that is a slowly
varying signal. The bandwidth of VCTRL can be additionally
limited by inserting the external type−2 compensation
components (that are RZ, CZ, and CP as shown in Figure 49).
It is recommended to limit cross over frequency of open loop
system below 20 Hz typically if the input ac voltage is 50 Hz
to achieve power factor correction purpose.
The transformer of Vbulk to VCTRL is as described in
Equation 16 if CZ >> CP. GEA is the error amplifier gain.
V ac 2
Z in
ǒV
T
ǒ
Ǔ
p 2 @ R CS @ V CTRL * V CTRLǒminǓ @ V PREF
+
2R MR SENSEK LBO 2 @ V bulk
CTRL * V CTRLǒminǓ
Ǔ
(eq. 20)
V bulk
ǒ
Ǔ
p 2 @ R CS @ V CTRL * V CTRLǒminǓ @ V PREF
P in + hP in + h
ǒV
T
2R MR SENSEK LBO 2 @ V bulk
CTRL * V CTRLǒminǓ
V bulk
Ǔ
(eq. 21)
Because of the Vin2 feed−forward, the power delivery is
independent from input voltage. Hence the transfer function
of power stage is independent from input voltage, which
easies the compensation loop design.
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NCP1910
PFC Frequency Foldback
is hence done by comparing (VCTRL − VCTRL(min)) with
Vfold, the voltage on Fold pin.
The simplified block diagram of PFC frequency foldback
feature is depicted in Figure 50.
NCP1910 implements frequency foldback feature on PFC
section to improve the efficiency at light load. Thanks to
Vin2 feed−forward feature, the output power is proportional
to the (VCTRL − VCTRL(min)). The PFC frequency foldback
PFCOSC
Vref
Vdd
Ict(min)
Ict
−
+
Vfold
Vfold(max)
Ict(fold)
“0” / ”1”
VPREF / 10%VPREF
Oscillator section
Vctrl
Grand Reset
PFC BO
Vctrl(min)
S
Q
Q
R
PFC OK
Figure 50. The PFC Frequency Foldback Block
Where:
♦ ICt(min) limits the minimum operating frequency.
♦ ICt and ICt(min) provide the charging current for
oscillator and hence control the nominal operating
frequency.
♦ Vfold determines the power level at which the
frequency foldback starts.
♦ ICt(fold) steals the ICt and hence reduces the
operating frequency according to the error
information between Vfold and (VCTRL −
VCTRL(min)).
The transient slope of frequency foldback vs. VCTRL
is fixed inside.
♦ Vfold(max) is to limit the maximum power level of
frequency foldback, which is around 2 V typically.
The frequency foldback is disabled at startup, i.e. before
the PFCok signal in Figure 50 is asserted high.
The user can adjust the power level at which the frequency
foldback starts by adjust the resistor divider between VREF
pin and fold pin. Also, the frequency foldback can be
disabled by grounding fold pin.
The relationship between operating frequency and VCTRL
is depicted in Figure 51.
♦
FREQUENCY
Fsw
The slope is fixed internally.
The power level at which frequency starts reducing is adjustable by modifying Vfold.
Fsw(fold)
Vfold – 0.4
Vfold
VCTRL−VCTRL(min) T Power
Figure 51. The Relationship between Frequency and VCTRL
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NCP1910
PFC Power Boost
As depicted in previous section, thanks to the Vin2
feed-forward, the power delivery is independent from input
voltage. It brings benefit of good power factor and a direct
control on the frequency foldback. However, in some special
case such as when the ac input voltage drops sharply from
high line to low line, the power will be limited because the
filter on LBO pin slows down the reaction speed to follow
up the change on input voltage. In the end, the bulk voltage
might drop too low and stop the LLC converter.
Hence, NCP1910 builds a so-called PFC power boost
function inside. The idea is to pull down LBO pin to 2 V
typically, VLBO(PD), when
• VLBO is above 2 V, VLBO(PD), i.e. the input is at high
line, and
• VCTRL is at maximum for more than timer defined by
tPFCflag, and,
• Vbulk is under 95% of nominal output, i.e. VLD is
triggered.
The maximum pulling-down duration is defined by
tLBO(PDlimit), which is 5 ms typically. A blanking timer,
tLBO(PDblank), is to avoid this power boost function reacting
too soon, which is about 77 ms typically. The PFC power
boost function is inhibited at start-up until bulk voltage is
above 95% of nominal output.
PFC Skip Mode
In order to ensure a proper regulation in no load
conditions, the circuit skips cycles when VCTRL is at its
minimum level. VCTRL is maintained between about 0.6 V
and 3.6 V due to the internal active clamps. A skip sequence
occurs as long as the 0.6 V clamp circuitry is triggered and
switching operations is recovered when the clamp is
inactive.
Fast Transient Response
Given the low bandwidth of the regulation block, the
output voltage of PFC stages may exhibit excessive over or
under−shoots because of abrupt load or input voltage
variations (such as start−up duration). As shown in
Figure 52, if the output voltage is out of regulation,
NCP1910 has 2 functions to maintain the output voltage
regulation.
Vbulk
PFC_OK
105% VPREF
Vdd
IVLD
200 mA
PFC_OVP
+
RFBU
PFC_OPL
−
FB
VLD
95% VPREF
CFB
RFBL
$30 mA
OTA
VCTRL
VPREF
Figure 52. PFC OVP and VLD
• Over−Voltage Protection (OVP): When VFB is higher
than 105% of VPREF (i.e. Vbulk > 105% of nominal
bulk voltage), the PFC driver output goes low for
protection. The circuit automatically resumes operation
when VFB becomes lower than 103.2% of VPREF, i.e.
around 44 mV hysteresis in the OVP comparator. If the
nominal Vbulk is set at 390 V, then the maximum bulk
•
voltage is 105% of 390 V = 410 V. Hence a cost and
size effective bulk capacitor of lower voltage rating is
suitable for this application,
Voltage−Low Detection (VLD): NCP1910 drastically
speeds up the regulation loop by its internal 200 mA
enhanced current source when the bulk voltage is below
95% of its regulation level. Under normal condition, the
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NCP1910
VCTRL pin current ( mA)
maximum sink and source of output current capability
of OTA is around 30 mA. Due to the “Vout Low Detect”
block (VLD), when the VFB is below 95% VPREF, an
extra 200 mA current source (IVLD in Figure 52) will
raise VCTRL rapidly. Hence prevent the PFC output
from dropping too low and improve the transient
response performance. The relationship between
current flowing in/out VCTRL pin and VFB is as shown
in Figure 53.
It is recommended to add a typical 100 pF capacitor CFB
decoupling capacitor next to feedback pin to prevent from
noise impact.
50
0
−50 2
2.2
2.4
2.6
2.8
3
−100
−150
No DRV when VFB is
above 105% VPREF
−200
−250
230 mA raises VCTRL rapidly
when VFB is below 95%
VPREF
VFB
Figure 53. VFB vs. Current Flowing in/out From VCTRL Pin
PFCok Signal
Refer to Figure 54. “PFCok” signal is low when
• the PFC stage start−up, or
• any latch off signal arrives, or
• line brown−out activates.
The PFC provides a “PFCok” signal to:
• enable the dynamic response enhancer (IVLD) if Vbulk is
below 95%, finish of the PFC soft−start,
• enable the PFC frequency foldback,
• enable the timer (tDEL1), which is to start the LLC−HB
converter,
• enable the timer (tDEL2), which is to stop LLC−HB
converter once “PFCok” is asserted low or Vbulk is
lower than PG level after LLC−HB has started.
This “PFCok” signal is high when the PFC stage is in
normal operation, i.e. its output is above 95% of normal
output, and low otherwise.
“PFCok” signal is high when
• DRV starts operating and the PFC stage is above 95%
•
of target, i.e. the VLD comparator output is high, or
the PFC stage is above 100% target, i.e. PFCREG
comparator output is high.
PFC_BO
Latch
Grand Reset
R
Q
Q
95% VPREF
+
DRV
S
−
VLD
FB
+
VPREF
−
PFCREG
Figure 54. PFCok Signal Block Diagram
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PFC_OK
NCP1910
PFC Soft−Start
As shown in Figure 55, when VFB is less than 8% of
VPREF, the device is shut down. The device automatically
starts operation when the output voltage goes above 12% of
VPREF. In normal situation of boost converter configuration,
the bulk voltage Vbulk is always greater than the input
voltage Vin and the feedback signal VFB has to be always
greater than 8% and 12% of VPREF to enable NCP1910 to
operate.
The main purpose of this Under−Voltage Protection
function is to protect the power stage from damage at
feedback loop abnormal, such as VFB is grounded or the
feedback resistor RFBU is open.
Refer to Figure 52 and 54. The device provides no PFC
driver output when the VCTRL is lower than VCTRL(min).
VCTRL is pulled low by:
• VCC Under−Voltage Lockout, or
• Off signal from on/off pin, or
• Thermal Shut−down (TSD), or
• Line Brown−out, or
• PFC Under−Voltage Protection
At one of these situations, NCP1910 grounds the VCTRL
pin and turns off the 200 mA current source in regulation
block.
When the IC turns on again:
• VCTRL will be pulled low and PFC DRV output keeps
off until VCTRL is below VCTRL(min) to make PFC
starts with lowest duty cycle.
• The 200 mA current source block keeps off. Only the
Operating Transconductance Amplifier (OTA) raises
the VCTRL slowly.
This is to obtain a slow increasing duty cycle and hence
reduce the voltage and current stress on the MOSFET. A
soft−start operation is obtained.
Redundant Over−Voltage Protection (OVP2 pin)
Except the Over−Voltage Protection in FB pin, NCP1910
also reserve one dedicated pin, OVP2 pin, for the redundant
over voltage protection on bulk voltage. The purpose of this
feature is to protect the power components from damage in
case of any drift on the feedback resistor. As shown in
Figure 56, the OVP2 has 3 differences compared to the OVP
in FB pin:
• The protection mode provided by OVP2 pin is
latch−off. When OVP2 is triggered, the NCP1910 stays
at latch off mode, i.e. both PFC and LLC stop.
• A 20 ms filter is built−in after the OVP2 comparator for
better noise immunity.
• The reference voltage for this OVP2 comparator is
107% of VPREF.
The resistance value of ROVPU and ROVPL could be the
same as RFBU and RFBL depending on the requirement of
OVP2 level. In this case, the level of the OVP in FB pin
would be 105% of normal bulk voltage and OVP2 will be
107% of normal bulk voltage. Or if one would need a higher
level for the OVP2, then it is flexible to change the value.
If someone doesn’t need this OVP2 feature, then OVP2
function could be disable by grounding the OVP2 pin.
PFC Under−Voltage Protection (UVP) for Open Loop
Protection
ICC2
Operating
Shutdown
ICC7
8% VPREF
12% VPREF
VFB
Figure 55. PFC Under−Voltage Protection
Vbulk
ROVPU
OVP2
20 ms filter
PFC_OVP2
to SR-latch
107% VPREF
COVP
ROVPL
Figure 56. PFC 2nd Over−Voltage Protection
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NCP1910
PFC Abnormal
However, as a D−flip−flop that creates division−by−two
internally provides two outputs (A and B in Figure 57), the
final effective signal on LLC driver outputs (ML and MU)
switches between 25 kHz and 500 kHz. The CCO is
configured in such a way that if the current that flows out
from the Rt pin increases, the switching frequency also goes
up.
The PFC abnormal is detected by sensing VCTRL level.
When VCTRL stays at VCTRL(max), or lower than VCTRL(min)
– 0.1 V, for more than tPFCabnormal, PFC turns off first. After
tDEL2, LLC shuts down. It is latches off protection.
The main purpose of this feature is to avoid LLC from
operating without correct operation of PFC stage.
LLC Section
Current Controlled Oscillator (CCO)
The current controlled oscillator features a high−speed
circuitry allowing operation from 50 kHz up to 1 MHz.
VDD
+
VRt
Rt
RSS
Q
Q
B
for ML
A
VCtmax
SS
Feedback
opto-coupler
for MU
R
Ct
Rmin
S
Clk
-
IDT
Rmax
D
LLCenable
Grand Reset
CSS
Grand Reset
Latch
LLC_BO
CS/FF > VCS1
tDEL2 elapsed
Q
S
S
Q
Q
Q
R
Grand Reset
Disable LLC ML and MU
R
Grand Reset
LLC_PG
+
VSS_RST
Figure 57. The Current Controlled Oscillator Architecture and Configuration
For the resonant applications, it is necessary to adjust
minimum operating frequency with high accuracy. The
designer also needs to limit maximum operating and startup
frequency. All these parameters can be adjusted by using
external components connected to the Rt pin as shown in
Figure 57.
The following approximate relationships hold for the
minimum, maximum and startup frequency respectively:
The internal timing capacitor Ct is charged by current
which is proportional to the current flowing out from the
Rt pin. The discharging current iDT is applied when voltage
on this capacitor reaches VCtmax. The output drivers are
disabled during discharge period so the dead time length is
given by the discharge current sink capability. Discharge
sink is disabled when voltage on the timing capacitor
reaches zero and charging cycle starts again. Ct is grounded
to disable the oscillator when either of “turn−off LLC”
signals arrives.
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NCP1910
• The minimum switching frequency is given by the Rmin
The definition of start−up, shut−off and these 2 delay
timers (tDEL1 and tDEL2) will be depicted later in “combo
management section”.
There are the other 2 delay timers are built−in after the
brown−out comparator:
• tBOK is the delay timer after Vbulk is rising above the
BO level.
• tBONOTOK is the delay timer after Vbulk is falling down
the BO level.
NCP1910 gets the information of Vbulk from the PFC FB
pin, which minimizes the losses of the high voltage sensing
circuit. As depicted in Figure 22, 3 resistors (R1, R2, and R3)
among VREF, PGadj, BOadj pin, and ground determine the
levels of PGout signal and LLC brown−out as the following
formulas:
resistor value. This frequency is reached if there is no
feedback action and soft start period has already
elapsed.
R min +
10 6V Rt
490
F min
(eq. 22)
• The maximum switching frequency excursion is limited
by the Rmax selection. Note that the maximum
frequency is influenced by the opto−coupler saturation
voltage value.
R max +
490
10 6V Rt
F max * F min
(eq. 23)
• Resistor RSS together with capacitor CSS prepares the
V PG +
soft start period for the resonant converter.
R SS +
490
10 6V Rt
F SS * F min
R2 ) R3
R1 ) R2 ) R3
(eq. 24)
+ V bulk,PG @
Where:
♦ VRt = 3.5 V
♦ Fmin is the minimal frequency
♦ Fmax is the maximal frequency
♦ FSS is the maximal soft start switching frequency
V BO +
(eq. 25)
R FBL
R FBU ) R FBL
R3
R1 ) R2 ) R3
+ V bulk,BO @
LLC Power Good Signal and Brown−out (PGadj, PGout
and BOadj Pin)
@ V REF
+ V bulk,PG @
V PREF
V bulk,nom
@ V REF
(eq. 26)
R FBL
R FBU ) R FBL
+ V bulk,BO @
V PREF
V bulk,nom
Where:
♦ VPG is the voltage on PGadj pin
♦ VBO is the voltage on BOadj pin
♦ VREF is the reference voltage (5 V typically).
♦ VPREF is the internal reference voltage for PFC
feedback OTA (2.5 V typically)
♦ Vbulk,PG is the bulk voltage when PGout pin is
released open.
♦ Vbulk,BO is the bulk voltage when brown−out
function of LLC activates.
♦ Vbulk,nom is the normal bulk voltage, e.g. 390 V.
Divide Equation 25 by 26, we can get the relationship
between R2 and R3 in Equation 27:
As shown in Figure 22, the NCP1910 provides the
Brown−Out circuitry (BO) that offer a way to protect the
resonant converter from operating at too low Vbulk. In the
mean time, NCP1910 provides a Power Good signal (PGout)
to inform the isolated secondary side that the NCP1910 is in
order of match.
Once the PFC has started and raises Vbulk above 95% of
its regulated voltage, an internal “PFC_OK” signal is
asserted. 20 ms later (tDEL1), the PGout pin is brought low.
The PGout signal can now disappear, which will release
PGout pin open, in two cases:
• Vbulk decreases to the level, programmed by a reference
voltage imposed on PGadj pin. This level is usually
above the LLC turn−off voltage, programmed by BOadj
pin. Therefore, in a normal turn−off sequence, PG first
drops and informs the secondary side that it must be
prepared for shutdown.
• The second event that can drop the PG signal is when
the PFC experiences a fault: broken feedback path
(PFC UVP), PFC abnormal, or input line brown−out. In
either case, the internal PFCok signal will drop and
then assert the PGout signal high, and starts a 5 ms timer
(tDEL2). Once this timer is elapsed, the LLC converter
can be safely halted.
R2
R3
+
V bulk,PG
V bulk,BO
*1
(eq. 27)
Hence, by given Vbulk,PG and Vbulk,BO, and choose the
value R3 as the 1st step, we can get the R2 by Equation 27 and
R1 by Equation 26.
For example, Vbulk,nom is 390 V, Vbulk,PG is 340 V, and
Vbulk,BO is 330 V. Choose 10 kW resistor as R3. Then R2 is
303 W. Choose 300 W as it is the closet standard resistor.
Then we can get the R1 is 13.3 kW.
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NCP1910
VREF
R3
BOadj
+
”1” BONOTOK
R1
R2
tBONOTOK
PFC_FB
LLCenable
PFC_OK
”1” is ok
”0” notok
”1” PGNOTOK
”1” enables LLC
”0” LLC is locked
−
PGadj
LLC_BO
tBOK
−
+
LLC_BO
LLC_PG
VCC
SS is reset
Grand
Reset
VSB
R
tDEL1
20 ms
R
tDEL2
PGout
5 ms
”1” after reset
”0” when PG out
drops after 5 ms
PGI for
supervisory
To close switch
at SS pin
Figure 58. The PG and BO Block Diagram for LLC
LLC Fast Fault Input (CS/FF Pin)
(ML and MU) is shifted up to keep the primary current under
acceptable level.
In case of heavy overload, like transformer short circuit,
the primary current grows very fast and thus could reach
danger level. The NCP1910 therefore features additional
comparator VCS2 (1.5 V typically) at the CS/FF pin to
permanently latch the device (both PFC and LLC) and
protect against destruction.
As shown in Figure 59, the NCP1910 offers a dedicated
input (CS/FF pin) to detect the primary over−current
conditions and protect the power stage from damage.
Once the voltage on the CS/FF pin exceeds the threshold
of VCS1 (1 V typically), the internal switch at SS pin will be
closed to discharge CSS until VSS is below VSS_RST
(150 mV typically). Hence the switching frequency of LLC
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NCP1910
PFC_OVP2
CS/FF
+
−
S
Q
Q
VCS2
Latch
”1” to disable LLC and PFC driver,
and pull down PFCok
R
+
PFC_BO
Grand Reset
”1” to set the SR−latch to
pull low SS pin
−
VCS1
Figure 59. The Fast Fault Input at CS/FF pin
LLC Soft−Start (SS Pin)
Once the LLC part starts operation, the internal switch at
SS pin is released open and the empty soft−start capacitor
withdraws current from Rt pin through soft−start resistor,
RSS. This current charges up and soft−start capacitor and
increases the operating frequency of LLC. As the soft−start
capacitor is charged, the LLC driver output frequency
smoothly decreases down to Fmin. Of course, practically, the
feedback loop is supposed to take over the CCO lead as soon
as the output voltage has reached the target.
In resonant converter, a soft−start is needed to avoid
suddenly applying the full current into the resonating circuit.
NCP1910 reserves SS pin to fully discharge soft−start
capacitor before re−start and in case of fault conditions:
• LLC brown−out actives,
• tDEL2 is elapsed, where tDEL2 timer could be activated
by line brown−out or power good comparator,
• CS/FF pin is above VCS1, the fast fault input for LLC,
• VCC UVLO,
• PFC UVP,
• Off signal from on/off pin, or
• Thermal Shut−Down (TSD)
When the switch inside SS pin is activated to discharge the
soft−start capacitor, it keeps close until VSS is below
VSS_RST (150 mV typically). It ensures the full discharge of
soft−start capacitor before re−start, and hence the fresh
soft−start is confirmed.
LLC Skip (Skip Pin, B Version Only)
To avoid any frequency runaway in light conditions but
also to improve the standby power consumption, the
NCP1910B welcomes a skip mode operation (Skip pin)
which permanently observes the opto−coupler collector as
depicted in Figure 60. If skip pin senses a low voltage, it cuts
the LLC output pulses (ML and MU pins) until the collector
goes up again.
Rt
Rmax
RSS
Rmin
SS
CSS
Skip
−
VSkip
+
Feedback
opto−coupler
Disable ML and
MU
Figure 60. The LLC Skip Mode Configuration
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NCP1910
LLC High−Voltage Driver
another timer (tDEL2) starts. Once the tDEL2 is elapsed, LLC
stops its drivers (ML and MU pins).
Figure 61 depicts the start−up and stop delay of LLC and
PGout.
Once the PFC is ready (PFCok is asserted high), tDEL1
(20 ms typically) is started. Once this delay is elapsed:
• PGout pin is asserted low
• LLC drivers (ML and MU pins) can start to operate.
The NCP1910 includes a high−voltage driver allowing a
direct connection to the upper side MOSFET of LLC
converter. This device also incorporates an upper UVLO
circuitry that makes sure enough gate voltage is available for
the upper side MOSFET. The bias of the floating driver
section is provided by Cboot capacitor between Vboot pin and
HB pin that is refilled by external booststrap diode. The
floating portion can go up to 600 Vdc and makes the IC
perfectly suitable for offline applications featuring a 400 V
PFC front−end stage.
As shutdown by unplug ac input, Vbulk decreases:
• When it reaches the PG signal, which is adjusted by
PGadj pin, PGout pin is released open.
• If Vbulk reaches the LLC stop level (BO level adjusted
by BOadj pin), the LLC stops; or if Vbulk drops slowly,
e.g. light load, LLC drivers (ML and MU pins) will
stop 5 ms after PGout pin is released (tDEL2).
Combo Management Section
Start−up and Stop Delay of LLC and Pgout signal
(tDEL1 and tDEL2)
To ensure the proper operation of LLC, LLC cannot start
if the PFC is not ready.
As depicted in the “PFCok signal” section, the internal
PFCok signal is asserted high when Vbulk is above 95% of
normal bulk voltage. After PFCok signal is high, a timer
(tDEL1) starts to ensure PFC stage is fully stable before LLC
starts. When tDEL1 is elapsed, PGout pin is grounded and
LLC starts its driver outputs (ML and MU pins).
In case of shutdown by unplugging ac input or line brown
out situation, PGout signal is released open. And then
As shutdown by line brown−out situation, PFCok signal will
be pulled down:
• PGout pin is released open once this internal PFCok
signal is low.
• LLC drivers (ML and MU pins) will stop 5 ms after
PGout pin is released open (tDEL2).
Vbulk
95%
PG level
BO level
tDEL1
20 ms
PGout
tDEL2
LLC works
off
5 ms
off
Figure 61. The Timing for tDEL1 and tDEL2
time
• When the on/off pin is above 3 V, the device stops both
Remote on/off (on/off pin)
NCP1910 reserves one dedicated pin for remote control
feature at on/off pin:
• When the on/off pin is pulled below 1 V, the PFC starts
operation. 20 ms after Vbulk is above 95% of target
level, LLC starts.
PFC and LLC immediately and keeps low
consumption. Figure 62 depicts the relationship
between the operation mode and on/off pin.
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NCP1910
State
ON
OFF
On/off pin
TBD
ICC
< 600 mA
Voff
Von
On/off pin
Figure 62. Remote on/off (on/off Pin)
VCC Under−Voltage LockOut (UVLO)
some hysteresis (VCC(Hys)) to prevent erratic operation as
the VCC crosses the threshold. When VCC goes below the
UVLO comparator lower threshold (VCC(min)), the circuit
turns off. It is illustrated in Figure 63. After startup, the
operating range is between 9 V and 20 V.
The device incorporates an Under−Voltage Lockout block
to prevent the circuit from operating when VCC is too low in
order to ensure a proper operation. An UVLO comparator
monitors VCC pin voltage to allow the NCP1910 to operate
when VCC exceeds VCC(on). The comparator incorporates
State
ON
OFF
TBD
ICC
VCC
< 100mA
VCC(on)
VCC(min)
VCC
Figure 63. VCC Under−Voltage LockOut (UVLO)
Bias the Controller
temperature exceeds TSD level. The output stage is then
enabled once the temperature drops below typically 110°C
(i.e. TSD − TSDhyste). The thermal shutdown is provided to
prevent possible device failures that could result from an
accidental over−heating.
It is recommended to add a typical 1 nF to 100 nF
decoupling capacitor next to the VCC pin for proper
operation. The hysteresis between VCC(on) and VCC(min) is
small because the NCP1910 is supposed to be biased by
external power source. Therefore it is recommended to
make a low−voltage source to bias NCP1910, e.g. the
standby power supply.
5 V Reference
The VREF pin provides an accurate (±2% typically) 5 V
reference voltage. The Power−Good and Brown−Out of
LLC converter, and the frequency foldback level (fold pin)
of PFC can hence can get an accurate reference voltage by
resistor dividers.
Thermal Shutdown
An internal thermal circuitry disables the circuit gate drive
and then keeps the power switch off when the junction
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NCP1910
• Recycle VCC so that VCC is below VCC(min) and back
Latched Protections and Reset
As depicated in the above sections, there are 3 fault modes
that latch off both PFC and LLC:
• PFC abnormal
• PFC OVP2
• LLC CS/FF pin is above VCS2
To release from the latch−off mode, NCP1910 offers 3
ways:
•
•
to above VCC(on) again.
Recycle the remote on/off function, which toggles
on/off pin high and low again.
Recycle the line brown−out function, which could be
done by unplug and re−plug the ac input.
ORDERING INFORMATION
Device
Version
Marking
Package
Shipping†
NCP1910A65DWR2G
65 kHz − A
NCP1910A65
SOIC 24WB Less Pin 21
(Pb−Free)
1000 / Tape & Reel
NCP1910B65DWR2G
65 kHz − B
NCP1910B65
SOIC 24WB Less Pin 21
(Pb−Free)
1000 / Tape & Reel
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
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NCP1910
PACKAGE DIMENSIONS
SOIC−24 WB LESS PIN 21
CASE 752AB−01
ISSUE O
0.20 C A-B
2X
D
D
A
H
NOTE 7
24
E
2X
13
E1
1
NOTES 5 & 6
L2
12
0.33 C
0.10 C D
B
PIN 1
INDICATOR
0.25
TOP VIEW
C
DETAIL A
2X
24X b
NOTE 7
L
C A-B D
M
NOTES 3 & 4
NOTE 9
h
x 45 _
0.10 C
0.10 C
A
e
A1
NOTE 8
C
c
SEATING
PLANE
DETAIL A
END VIEW
SIDE VIEW
M
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME
Y14.5M, 1994.
2. CONTROLLING DIMENSION: MILLIMETERS.
3. DIMENSION B DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE PROTRUSION SHALL
BE 0.10 mm TOTAL IN EXCESS OF ’b’ AT MAXIMUM MATERIAL CONDITION.
4. DIMENSIONS b AND c APPLY TO THE FLAT SECTION OF THE LEAD AND ARE MEASURED
BETWEEN 0.10 AND 0.25 FROM THE LEAD TIP.
5. DIMENSIONS D AND E1 DO NOT INCLUDE MOLD
FLASH, PROTRUSIONS OR GATE BURRS. MOLD
FLASH, PROTRUSIONS OR GATE BURRS SHALL
NOT EXCEED 0.15 mm PER SIDE. INTERLEAD
FLASH OR PROTRUSION SHALL NOT EXCEED
0.25 PER SIDE. DIMENSIONS D AND E1 ARE
DETERMINED AT DATUM H.
6. DIMENSIONS D AND E1 ARE DETERMINED AT
THE OUTERMOST EXTREMES OF THE PLASTIC
BODY EXCLUSIVE OF MOLD FLASH,
PROTRUSIONS, TIE BAR BURRS, OR GATE
BURRS BUT INCLUSIVE OF ANY MOLD
MISMATCH BETWEEN THE TOP AND BOTTOM OF
THE PLASTIC BODY.
7. DIMENSIONS A AND B ARE TO BE DETERMINED
AT DATUM H.
8. A1 IS DEFINED AS THE VERTICAL DISTANCE
FROM THE SEATING PLANE TO THE LOWEST
POINT ON THE PACKAGE BODY.
9. THIS CHAMFER IS OPTIONAL. IF IT IS NOT
PRESENT, THEN A PIN 1 IDENTIFIER MUST BE
LOCATED IN THE INDICATED AREA.
RECOMMENDED
SOLDERING FOOTPRINT*
23X
23X
1.62
0.52
DIM
A
A1
b
J
D
E
E1
e
h
L
L2
M
MILLIMETERS
MIN
MAX
2.35
2.65
0.10
0.29
0.31
0.51
0.20
0.33
15.40 BSC
10.30 BSC
7.50 BSC
1.27 BSC
0.25
0.75
0.40
1.27
0.25 BSC
0_
8 _
11.00
1
1.27
PITCH
DIMENSIONS: MILLIMETERS
*For additional information on our Pb−Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a number of patents, trademarks,
copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. SCILLC
reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any
particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without
limitation special, consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications
and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC
does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for
surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where
personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and
its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly,
any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture
of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
LITERATURE FULFILLMENT:
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For additional information, please contact your local
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NCP1910/D