ON NCP1076ABP100G Enhanced off-line switcher Datasheet

NCP1075A/B, NCP1076A/B,
NCP1077A/B, NCP1079A/B
Enhanced Off-line Switcher
for Robust and Highly
Efficient Power Supplies
The NCP107xuz products integrate a fixed frequency current mode
controller with a 700 V MOSFET. Available in a two different pin−out
of the very common PDIP−7 package, the NCP107xuz offers a high
level of integration, including soft−start, frequency−jittering,
short−circuit protection, skip−cycle, a maximum peak current
set−point, ramp compensation, and a dynamic self−supply (DSS,
eliminating the need for an auxiliary winding).
Unlike other monolithic solutions, the NCP107xuz is quiet by
nature: during nominal load operation, the part switches at one of the
available frequencies (65, 100 or 130 kHz). When the output power
demand diminishes, the IC automatically enters frequency foldback
mode and provides excellent efficiency at light loads. When the power
demand reduces further, it enters into a skip mode to reduce the
standby consumption down to a no load condition.
Protection features include: a timer to detect an overload or a
short−circuit event, Over−voltage Protection with auto−recovery. Ac
input line voltage detection prevents lethal runaway in low input
voltage conditions (Brown−out) as well as too high an input line (Ac
line Over−voltage Protection). This also allows an Over−power
Protection to compensate all internal delays in high input voltage
conditions and optimize the maximum output current capability.
For improved standby performance, the connection of an auxiliary
winding stops the DSS operation and helps to reduce input power
consumption below 50 mW at high line.
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MARKING
DIAGRAMS
PDIP−7
(PDIP−8 LESS PIN 6)
CASE 626A
PDIP−7
(PDIP−8 LESS PIN 3)
CASE 626AS
x
u
z
y
A
WL
Y, YY
W, WW
G
P107xPuzy
AWL
YYWWG
P107xPuzy
AWL
YYWWG
= Power Version (5, 6, 7, 9)
= Pin Connections (A, B)
= 2nd level OCP enabled/disabled (A, B)
= Oscillator Frequency 65, 100, 130 (A, B, C)
= Assembly Location
= Wafer Lot
= Year
= Work Week
= Pb−Free Package
ORDERING INFORMATION
See detailed ordering and shipping information on page 31 of
this data sheet.
Features
• Built−in 700 V MOSFET with RDS(ON) of 13.5 W
•
•
•
•
•
•
•
•
•
• Adjustable Brown−out Protection and OVP
• 2nd Leading Edge Blanking – Current Protection
(NCP1075uz), 4.8 W (NCP1076uz/77uz) and 2.9 W
(NCP1079uz)
Large Creepage Distance Between High Voltage Pins
Current−mode Fixed Frequency Operation –
65 / 100 / 130 kHz
Various Options for Maximum Peak Current: see below
table
Fixed Slope Compensation
Skip−cycle Operation at Low Peak Currents Only
Dynamic Self−supply: No Need for an Auxiliary
Winding
Internal 10 ms Soft−start
Auto−recovery Output Short−circuit Protection with
Timer−based Detection
Auto−recovery Over−voltage Protection with Auxiliary
Winding Operation
© Semiconductor Components Industries, LLC, 2017
November, 2017 − Rev. 2
•
•
•
•
•
(NCP107xuA version only)
Over Power Protection
Frequency Jittering for Better EMI Signature
No Load Input Consumption < 50 mW
Frequency Foldback to Improve Efficiency at Light
Load
These are Pb−free Devices
Typical Applications
•
•
•
•
1
Auxiliary / Standby Isolated Power Supplies
Major Home Appliances Power Supplies
Power Meter SMPS
Wide Input Industrial SMPS
Publication Order Number:
NCP1076A/D
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
PIN CONNECTIONS
VCC
GND
FB
BO/AC_OVP
GND
VCC
BO/AC_OVP
GND
GND
GND
FB
DRAIN
DRAIN
GND
(Top View)
PDIP−7
NCP107xB
(Top View)
PDIP−7
NCP107xA
PIN FUNCTION DESCRIPTION
Pin No
PDIP 7 A
PDIP 7 B
Pin Name
Function
1
2
VCC
IC supply pin
This pin is connected to an external capacitor.
The VCC management includes an auto−recovery over−voltage protection.
2
8
BO/AC_OVP
Brown−out / Ac Line
Over−voltage protection
Detects both input voltage conditions (Brown−
out) and too high an input voltage (Ac line OVP).
Do not leave this pin floating – if this pin is not
used it should be directly connected do GND.
3
5
GND
The IC Ground
4
1
FB
Feedback signal input
5
4
DRAIN
Drain connection
6
3
NC
7
6
GND
The IC Ground
8
7
GND
The IC Ground
Pin Description
By connecting an opto−coupler to this pin, the
peak current set−point is adjusted accordingly to
the output power demand.
The internal drain MOSFET connection
This un−connected pin ensures adequate creepage distance
PRODUCTS INFOS & INDICATIVE MAXIMUM OUTPUT POWER
230 Vrms +15%
85−265 Vrms
Product
RDS(ON)
IPK
Adapter
Open Frame
Adapter
Open Frame
NCP1075uz
13.5 W
400 mA
8.5 W
14 W
6W
10 W
NCP1076uz / NCP1077uz
4.8 W
800 mA
19 W
31 W
14 W
23 W
NCP1079uz
2.9 W
1050 mA
25 W
41 W
18 W
30 W
NOTE:
Informative values only, with Tamb = 25°C, Tcase = 100°C, PDIP−7 package, Self−supply via Auxiliary winding and circuit mounted
on minimum copper area as recommended.
QUICK SELECTION TABLE
Device
Frequency [kHz]
RDS(ON) [W]
IPK [mA]
NCP1075uz
65, 100, 130*
13.5
400
NCP1076uz
65, 100, 130*
4.8
650
NCP1077uz
65, 100, 130*
4.8
800
NCP1079uz
65, 100, 130*
2.9
1050
*NOTE: 130 kHz option available in pin connection B only
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2
Package type
PDIP−7
(Pb−Free)
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
Figure 1. Typical Isolated Application (Flyback Converter), Enable Brown−out, Ac Line OVP and OPP Functions
Figure 2. Typical Isolated Application (Flyback Converter), Disabled Brown−out Function –
Against Line Detection
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3
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
DRAIN
VCC
Management
VCC
VCC OVP
Line
detection
enable
ISTOP
Line
detection
enable
TSD
Line Detection
S
BO enable
Q
AC OVP
VFB(REF)
DRV
R
Feedback control
Slope
compensation
Sawtooth
RFB(UP)
LEB 1
FB
Current set−point
BO/AC_OVP
OPP
Soft−Start
Ifreeze IPK(0)
Brown−out
BO enable
AC OVP
ISTOP
Figure 3. Simplified Internal Circuit Architecture
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4
Peak current
protection
GND
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
MAXIMUM RATINGS TABLE (All voltages related to GND terminal)
Rating
Power supply voltage, VCC pin, continuous voltage
Symbol
Value
Unit
VCC
−0.3 to 20
V
Voltage on all pins, except DRAIN and VCC pin
Vinmax
−0.3 to 10
V
DRAIN voltage
BVDSS
−0.3 to 700
V
ICC
15
mA
Maximum Current into VCC pin
Drain Current Peak during Transformer Saturation (TJ = 150°C):
NCP1075uz
NCP1076uz/77uz
NCP1079uz
IDS(PK)
A
0.9
2.2
3.6
Drain Current Peak during Transformer Saturation (TJ = 25°C):
NCP1075uz
NCP1076uz/77uz
NCP1079uz
1.5
3.9
6.4
Thermal Resistance Junction−to−Air – PDIP7
0.36 Sq. Inch
RθJ−A
1.0 Sq. Inch
Maximum Junction Temperature
77
°C/W
68
TJMAX
Storage Temperature Range
150
°C
−60 to +150
°C
Human Body Model ESD Capability (All pins except HV pin) per JEDEC JESD22−A114F
HBM
2
kV
Human Body Model ESD Capability (Drain pin) per JEDEC JESD22−A114F
HBM
1
kV
Charged−Device Model ESD Capability per JEDEC JESD22−C101E
CDM
1
kV
MM
200
V
Machine Model ESD Capability per JEDEC JESD22−A115−A
Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality
should not be assumed, damage may occur and reliability may be affected.
1. This device contains latch−up protection and exceeds 100 mA per JEDEC Standard JESD78.
2. Maximum drain current IDS(PK) is obtained when the transformer saturates. It should not be mixed with short pulses that can be seen at turn
on. Figure 4 below provides spike limits the device can tolerate.
iD(t)
< 1.5 x IDS(PK)
< tLEB
IDS(PK)
Transformer
Saturation
t
Figure 4. Spike Limits
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NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
ELECTRICAL CHARACTERISTICS
(For typical values TJ = 25°C, for min/max values TJ = −40°C to +125°C, VCC = 12 V unless otherwise noted)
Symbol
Rating
Pin
Min
Typ
Max
Unit
SUPPLY SECTION AND VCC MANAGEMENT
VCC(ON)
VCC increasing level at which the switcher starts operation
1 (2)
8.0
8.4
8.9
V
VCC(MIN)
VCC decreasing level at which the HV current source restarts
1 (2)
6.5
6.9
7.3
V
VCC(OFF)
VCC decreasing level at which the switcher stops operation (UVLO)
1 (2)
6.1
6.5
6.9
V
VCC(reset)
VCC voltage at which the internal latch is reset (Guaranteed by design)
1 (2)
Internal IC consumption, MOSFET switching (fSW = 65 kHz)
NCP1075uz
NCP1076uz/77uz
NCP1079uz
1 (2)
Internal IC consumption, VFB is 0 V (No switching on MOSFET)
1 (2)
ICC1
ICC(skip)
4
V
mA
−
−
−
1.10
1.26
1.40
−
−
−
−
400
−
mA
POWER SWITCH CIRCUIT
RDS(ON)
BVDSS
IDSS(OFF)
tR
tF
Power Switch Circuit on−state resistance (IDRAIN = 50 mA)
NCP1075uz
TJ = 25°C
TJ = 125°C
NCP1076uz/77uz
TJ = 25°C
TJ = 125°C
NCP1079uz
TJ = 25°C
TJ = 125°C
5 (4)
Power Switch Circuit & Start−up breakdown voltage
(IDRAIN(OFF) = 120 mA, TJ = 25°C)
W
−
−
13.5
26.0
16.8
31.6
−
−
4.8
9.3
6.8
11.6
−
−
2.9
5.3
3.9
7.5
5 (4)
700
−
−
V
Power Switch & Start−up breakdown voltage off−state leakage current
TJ = 125°C (VDS = 700 V)
5 (4)
−
85
−
mA
Switching characteristics (RL = 50 W, VDS set for IDRAIN = 0.7 x Ilim)
Turn−on time (90% − 10%)
Turn−off time (10% − 90%)
5 (4)
−
−
20
10
−
−
ns
INTERNAL START−UP CURRENT SOURCE
Istart1
High−voltage current source, VCC = VCC(ON) – 200 mV
5 (4)
4.0
9.0
12.0
mA
Istart2
High−voltage current source, VCC = 0 V
5 (4)
−
0.5
−
mA
VHV(MIN)
Minimum start−up voltage, VCC = 0 V
5 (4)
−
21
−
V
VCC(TH)
VCC Transient level for Istart1 to Istart2 toggling point
1 (2)
−
1.6
−
V
CURRENT COMPARATOR
IPK
IPK(0)
Maximum internal current set−point at 50% duty−cycle
FB pin open, TJ = 25°C
NCP1075uz
NCP1076uz
NCP1077uz
NCP1079uz
Maximum internal current set−point at beginning of switching cycle
FB pin open, BO/AC_OVP pin voltage v 0.8 V, TJ = 25°C
NCP1075uz
NCP1076uz
NCP1077uz
NCP1079uz
mA
−
−
−
−
−
−
−
−
400
650
800
1050
−
−
−
−
mA
−
−
−
−
420
690
850
1110
470
765
940
1230
520
840
1030
1350
3. The final switch current is: IPK(0) / (Vin/LP + Sa) x Vin/LP + Vin/LP x tprop, with Sa the built−in slope compensation, Vin the input voltage, LP
the primary inductor in a flyback, and tprop the propagation delay.
4. Oscillator frequency is measured with disabled jittering.
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NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
ELECTRICAL CHARACTERISTICS
(For typical values TJ = 25°C, for min/max values TJ = −40°C to +125°C, VCC = 12 V unless otherwise noted)
Symbol
Rating
Pin
Min
Typ
Max
Unit
CURRENT COMPARATOR
IPKSW(65)
IPKSW(100)
IPKSW(130)
IPK(OPP)
Final switch current with a primary slope of 200 mA/ms,
fSW = 65 kHz (Note 3)
NCP1075uz
NCP1076uz
NCP1077uz
NCP1079uz
Final switch current with a primary slope of 200 mA/ms,
fSW =100 kHz (Note 3)
NCP1075uz
NCP1076uz
NCP1077uz
NCP1079uz
Final switch current with a primary slope of 200 mA/ms,
fSW =130 kHz (Note 3)
NCP1075uz
NCP1076uz
NCP1077uz
NCP1079uz
mA
−
−
−
−
−
−
−
−
450
710
860
1100
−
−
−
−
mA
−
−
−
−
−
−
−
−
440
685
825
1040
−
−
−
−
mA
−
−
−
−
−
−
−
−
450
685
820
1020
−
−
−
−
Maximum internal current set−point at beginning of switching cycle
FB pin open, BO/AC_OVP pin voltage = 2.65 V, TJ = 25°C
NCP1075uz
NCP1076uz
NCP1077uz
NCP1079uz
mA
−
−
−
−
−
−
−
−
375
610
750
985
−
−
−
−
tSS
Soft−start duration (Guaranteed by design)
−
−
10
−
ms
tprop
Propagation delay from current detection to drain OFF state
−
−
100
−
ns
tLEB1
Leading Edge Blanking Duration 1
−
−
300
−
ns
tLEB2
Leading Edge Blanking Duration 2 (NCP107xuA version only)
−
−
100
−
ns
59
65
71
kHz
INTERNAL OSCILLATOR
fOSC(65)
Oscillation frequency, 65 kHz version, TJ = 25°C (Note 4)
−
fOSC(100)
Oscillation frequency, 100 kHz version, TJ = 25°C (Note 4)
−
90
100
110
kHz
fOSC(130)
Oscillation frequency, 130 kHz version, TJ = 25°C (Note 4)
−
117
130
143
kHz
fjitter
Frequency jittering in percentage of fOSC
−
−
±6
−
%
fswing
Jittering modulation frequency
−
−
300
−
Hz
DMAX
Maximum duty−cycle
−
64
68
72
%
FEEDBACK SECTION
IFB(fault)
FB current for which Fault is detected
4 (1)
−
−35
−
mA
IFB100%
FB current for which internal current set−point is 100% (IPK(0))
4 (1)
−
−44
−
mA
IFB(freeze)
FB current for which internal current set-point is Ifreeze
4 (1)
−
−90
−
mA
VFB(REF)
Equivalent pull−up voltage in linear regulation range
(Guaranteed by design)
4 (1)
−
3.3
−
V
RFB(UP)
Equivalent feedback resistor in linear regulation range
(Guaranteed by design)
4 (1)
−
19.5
−
kΩ
Start of frequency foldback FB pin current level
4 (1)
−
−68
−
mA
End of frequency foldback FB pin current level, fSW = fMIN
4 (1)
−
−100
−
mA
FREQUENCY FOLDBACK & SKIP
IFBfold
IFBfold(END)
3. The final switch current is: IPK(0) / (Vin/LP + Sa) x Vin/LP + Vin/LP x tprop, with Sa the built−in slope compensation, Vin the input voltage, LP
the primary inductor in a flyback, and tprop the propagation delay.
4. Oscillator frequency is measured with disabled jittering.
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NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
ELECTRICAL CHARACTERISTICS
(For typical values TJ = 25°C, for min/max values TJ = −40°C to +125°C, VCC = 12 V unless otherwise noted)
Symbol
Rating
Pin
Min
Typ
Max
Unit
−
4 (1)
23
27
31
kHz
−
−120
−
FREQUENCY FOLDBACK & SKIP
fMIN
IFB(skip)
Ifreeze
The frequency below which skip−cycle occurs, TJ = 25°C (Note 4)
The FB pin current level to enter skip mode
Internal minimum current set−point (IFB = IFB(freeze))
NCP1075uz
NCP1076uz
NCP1077uz
NCP1079uz
mA
mA
−
−
−
−
−
−
−
−
165
270
330
430
−
−
−
−
The internal slope compensation @ 65 kHz:
NCP1075uz
NCP1076uz
NCP1077uz
NCP1079uz
−
−
−
−
−
−
−
−
9
15
18
23
−
−
−
−
The internal slope compensation @ 100 kHz:
NCP1075uz
NCP1076uz
NCP1077uz
NCP1079uz
−
−
−
−
−
−
−
−
14
23
28
36
−
−
−
−
The internal slope compensation @ 130 kHz:
NCP1075uz
NCP1076uz
NCP1077uz
NCP1079uz
−
−
−
−
−
−
−
−
18
30
36
46
−
−
−
−
Fault validation further to error flag assertion
−
35
48
−
ms
OFF phase in fault mode
−
−
420
−
ms
1 (5)
17.0
18.0
18.8
V
SLOPE COMPENSATION
Sa(65)
Sa(100)
Sa(130)
mA/ms
mA/ms
mA/ms
PROTECTIONS
tSCP
trecovery
VOVP
VCC voltage at which the switcher stops pulsing
tOVP
The filter of VCC OVP comparator
−
−
80
−
ms
VBO(EN)
Brown−out level detection
2 (8)
−
50
−
mV
VBO(ON)
Brown−out level, the switcher starts pulsing, OPP starts to decrease IPK
2 (8)
0.76
0.80
0.84
V
Brown−out hysteresis (Guaranteed by design)
2 (8)
−
100
−
mV
OVP level when the switcher stops pulsing
2 (8)
2.755
2.900
3.045
V
VACOVP(OFF) OVP level when the switcher starts pulsing
2 (8)
2.3
2.6
2.9
V
−
−
20
−
ms
VBO(HYST)
VACOVP(ON)
tBOfilter
tBO
VBO filter
Brown−out timer
VHV(EN)
The drain pin voltage above which the MOSFET operates. Checked after one
of the following events: TSD, UVLO, SCP, or VCC OVP mode, BO/AC_OVP
pin = 0 V
IPK(150)
High current protection, percent of max limit IPK (NCP107xuA version only)
−
−
50
−
ms
5 (4)
72
91
110
V
−
−
150
−
%
TEMPERATURE MANAGEMENT
TSD
Temperature shutdown (Guaranteed by design)
−
150
−
−
°C
TSDHYST
Hysteresis in shutdown (Guaranteed by design)
−
−
20
−
°C
3. The final switch current is: IPK(0) / (Vin/LP + Sa) x Vin/LP + Vin/LP x tprop, with Sa the built−in slope compensation, Vin the input voltage, LP
the primary inductor in a flyback, and tprop the propagation delay.
4. Oscillator frequency is measured with disabled jittering.
Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product
performance may not be indicated by the Electrical Characteristics if operated under different conditions.
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NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
TYPICAL CHARACTERISTICS
6.98
8.50
6.96
8.45
6.94
VCC(min) (V)
VCC(on) (V)
6.92
8.40
8.35
6.90
6.88
6.86
6.84
8.30
6.82
8.25
−40
6.80
6.78
−40 −20
−20
0
20
40
60
80
100
120
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 5. VCC(on) vs. Temperature
Figure 6. VCC(min) vs. Temperature
120
130
6.49
120
6.48
110
100
IDSS(off) (mA)
VCC(off) (V)
6.47
6.46
6.45
90
80
70
60
6.44
50
6.43
6.42
−40
40
−20
0
20
40
60
80
100
30
−40
120
20
40
60
80
100
TEMPERATURE (°C)
Figure 7. VCC(off) vs. Temperature
Figure 8. IDSS(off) vs. Temperature
1.28
1.14
1.27
ICC1(1076uz/77uz) (mA)
1.12
ICC1(1075uz) (mA)
0
TEMPERATURE (°C)
1.16
1.10
1.08
1.06
1.04
120
1.26
1.25
1.24
1.23
1.22
1.21
1.20
1.02
1.00
−40
−20
1.19
−20
0
20
40
60
80
100
1.18
−40
120
−20
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 9. ICC1(1075uz) vs. Temperature
Figure 10. ICC1(1076uz/77uz) vs. Temperature
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9
120
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
TYPICAL CHARACTERISTICS
1.39
460
1.37
450
IPK(0)1075uz (mA)
ICC1(1079uz) (mA)
1.35
1.33
1.31
1.29
1.27
440
430
1.25
1.23
1.21
−40 −20
0
20
40
60
80
100
420
−40
120
40
60
80
100
Figure 11. ICC1(1079uz) vs. Temperature
Figure 12. IPK(0)1075uz vs. Temperature
120
960
940
IPK(0)1077uz (mA)
IPK(0)1076uz (mA)
20
TEMPERATURE (°C)
760
740
720
700
920
900
880
860
−20
0
20
40
60
80
100
840
−40 −20
120
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 13. IPK(0)1076uz vs. Temperature
Figure 14. IPK(0)1077uz vs. Temperature
120
12
1200
10
ISTART1 (mA)
1160
IPK(0)1079uz (mA)
0
TEMPERATURE (°C)
780
680
−40
−20
1120
1080
1040
8
6
4
2
1000
−40 −20
0
20
40
60
80
100
0
−40
120
−20
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 15. IPK(0)1079uz vs. Temperature
Figure 16. ISTART1 vs. Temperature
www.onsemi.com
10
120
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
TYPICAL CHARACTERISTICS
0.65
30
0.60
NCP1075uz
25
0.50
RDS(on) (W)
ISTART2 (mA)
0.55
0.45
0.40
20
15
10
NCP1076uz/77uz
5
NCP1079uz
0.35
0.30
0.25
−40 −20
0
20
40
60
80
100
0
−40
120
−20
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 17. ISTART2 vs. Temperature
Figure 18. RDS(on) vs. Temperature
66
120
99
98
65
fOSC100 (kHz)
fOSC65 (kHz)
97
64
63
62
96
95
94
93
61
92
60
−40 −20
0
20
40
60
80
100
91
−40 −20
120
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 19. fOSC65 vs. Temperature
Figure 20. fOSC100 vs. Temperature
131
120
67.5
129
DMAX (%)
fOSC130 (kHz)
67.4
127
125
67.3
123
67.2
121
119
−40 −20
0
20
40
60
80
100
67.1
−40 −20
120
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 21. fOSC130 vs. Temperature
Figure 22. DMAX vs. Temperature
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11
120
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
TYPICAL CHARACTERISTICS
28.0
380
375
tRECOVERY (ms)
fMIN (kHz)
27.5
27.0
370
365
360
26.5
355
−20
0
20
40
60
80
100
350
−40 −20
120
20
40
60
80
100
TEMPERATURE (°C)
Figure 23. fMIN vs. Temperature
Figure 24. tRECOVERY vs. Temperature
52
18.4
51
18.3
50
18.2
49
120
18.1
18.0
48
47
−40
0
TEMPERATURE (°C)
VOVP (V)
tSCP (ms)
26.0
−40
−20
0
20
40
60
80
100
17.9
−40
120
−20
0
20
40
60
80
100
120
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 26. VOVP vs. Temperature
Figure 25. tSCP vs. Temperature
92
0.810
91
0.805
VBO(on) (V)
VHV(en) (V)
90
89
0.800
0.795
88
0.790
87
86
−40 −20
0
20
40
60
80
100
0.785
−40 −20
120
TEMPERATURE (°C)
0
20
40
60
80
100
TEMPERATURE (°C)
Figure 27. VHV(en) vs. Temperature
Figure 28. VBO(on) vs. Temperature
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12
120
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
2.99
2.620
2.97
2.615
2.95
VACOVP(off) (V)
VACOVP(on) (V)
TYPICAL CHARACTERISTICS
2.93
2.91
2.89
2.610
2.605
2.600
2.595
2.87
2.85
−40 −20
0
20
40
60
80
100
2.590
−40 −20
120
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 29. VACOVP(on) vs. Temperature
Figure 30. VACOVP(off) vs. Temperature
120
10
1.100
NCP1079uz
8
IDS(pk) (A)
1.050
1.025
1.000
NCP1076uz/77uz
6
4
0.975
NCP1075uz
2
0.950
0.925
−40
−20
0
20
40
60
80
100
0
−40 −20
120
0
20
40
60
80
100
120
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 31. BVDSS/BVDSS(255C) vs.
Temperature
Figure 32. Drain Current Peak during
Transformer Saturation vs. Junction
Temperature
1.7
NCP1079uz
1.6
1.5
ICC1 (mA)
BVDSS/BVDSS(25°C) [−]
1.075
NCP1076uz/77uz
1.4
1.3
NCP1075uz
1.2
1.1
1.0
7
8
9
10
11
12
13
14
VCC (V)
Figure 33. ICC1 vs. VCC
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13
15
16
17
140
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
APPLICATION INFORMATION
Introduction
Thanks to ON Semiconductor Very High Voltage
Integrated Circuit technology, the circuit hosts a
high−voltage power MOSFET featuring a 13.5/4.8/2.9 W
RDS(ON) – TJ = 25°C. An internal current source delivers the
start−up current, necessary to crank the power supply.
• Current−mode operation: The controller uses
current−mode control architecture.
• 700 V Power MOSFET: Thanks to ON Semiconductor
Very High Voltage Integrated Circuit technology, the
circuit hosts a high−voltage power MOSFET featuring
a 4.8 and 2.9 W RDS(ON) – TJ = 25°C. This value lets
the designer build a power supply up to 28 W operated
on universal mains. An internal current source delivers
the start−up current, necessary to crank the power
supply.
• Dynamic Self−Supply: This device could be used in an
application without an auxiliary winding to provide
supply voltage via an internal high−voltage current
source.
• Short−circuit protection: By permanently monitoring
the feedback line activity, the IC is able to detect the
presence of a short−circuit, immediately reducing the
output power for a total system protection. A tSCP timer
is started as soon as the feedback current is below
threshold, IFB(fault), which indicates a maximum peak
current condition. If at the end of this timer the fault is
still present, then the device enters a safe,
auto−recovery burst mode, affected by a fixed timer
recurrence, trecovery. Once the short has disappeared, the
controller resumes and goes back to normal operation.
• Built−in VCC Over−Voltage Protection: When the
auxiliary winding is used to bias the VCC pin (no
DSS), an internal comparator is connected to VCC pin.
In case the voltage on the pin exceeds the VOVP level
(18 V typically), the controller immediately stops
switching and awaits a full timer period (trecovery)
before attempting to re−start. If the fault is gone, the
controller resumes operation. If the fault is still there,
e.g. in the case of a broken opto−coupler, the controller
protects the load through a safe burst mode.
• Line detection: An internal comparator monitors the
drain voltage. If the drain voltage is lower than the
internal threshold (VHV(EN)), the internal power switch
•
•
•
•
•
•
•
is inhibited. This avoids operating at too low an ac
input. Line detection is active, when BO/AC_OVP pin
is grounded.
Brown−out detection and AC line Over−Voltage
Protection: The BO/AC_OVP input monitors bulk
voltage level via resistive divider and thus assures that
the application is working only for designed bulk
voltage. When BO/AC_OVP pin is connected to
ground, Line detection is inhibited.
Internal OPP: An internal function using the bulk
voltage to program the maximum current reduction for
a given input voltage. Internal OPP is active when
BO/AC_OVP pin is connected via resistive divider to
the bulk voltage.
2nd LEB (NCP107xuA only): Second level of current
protection. If peak current is 150% max peak current
limit, then the controller stops switching after three
pulses and waits for an auto−recovery period (trecovery)
before attempting to re−start.
Frequency jittering: An internal low−frequency
modulation signal varies the pace at which the
oscillator frequency is modulated. This helps spreading
out energy in conducted noise analysis. To improve the
EMI signature at low power levels, the jittering remains
active in frequency foldback mode.
Soft−Start: A 10 ms soft−start ensures a smooth
start−up sequence, reducing output overshoots.
Frequency foldback capability: A continuous flow of
pulses is not compatible with no−load/light−load
standby power requirements. To excel in this domain,
the controller observes the feedback current
information and when it reaches a level of IFBfold, the
oscillator then starts to reduce its switching frequency
as the feedback current continues to increase (the power
demand continues to reduce). It can go down to 27 kHz
(typical) reached for a feedback level of IFBfold(END)
(100 mA roughly). At this point, if the power continues
to drop, the controller enters classical skip−cycle mode.
Skip: If SMPS naturally exhibits a good efficiency at
nominal load, they begin to be less efficient when the
output power demand diminishes. By skipping
un−needed switching cycles, the NCP107xuz
drastically reduces the power wasted during light load
conditions.
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14
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
Start−up Sequence
V BULK
When the power supply is first powered from the mains
outlet, the internal current source (typically 9.2 mA) is
biased and charges up the VCC capacitor from the drain pin.
Once the voltage on this VCC capacitor reaches the VCC(ON)
level (typically 8.4 V), the current source turns off and
pulses are delivered by the output stage: the circuit is awake
and activates the power MOSFET if the bulk voltage is
above VHV(EN) level (Brown−in protection) or voltage on
BO/AC_OVP pin is above VBO(ON) level (Brown−out
protection). Figure 34 details the simplified internal
circuitry.
Being loaded by the circuit consumption, the voltage on
the VCC capacitor goes down. When VCC is below VCC(MIN)
level (7 V typically), it activates the internal current source
to bring VCC toward VCC(ON) level and stops again: a cycle
takes place whose low frequency depends on the VCC
capacitor and the IC consumption. A 1.5 V ripple takes place
on the VCC pin whose average value equals (VCC(ON) +
VCC(MIN))/2. Figure 35 portrays a typical operation of the
DSS.
I1
R limit
Istart 1
VCC
DRAIN
ICC 1
I2
V CC (ON )
V CC (MIN )
C VCC
GND
V OVP
Figure 34. The Internal Arrangement of the
Start−up Circuitry
9
8.4 V
8
7
6.9 V
6
VCC
V [V]
5
Device
Internal
Pulses
4
3
VCC(TH)
2
1
0
0
1
2
3
Startup Duration
4
5
6
time [ms]
Figure 35. The Charge / Discharge Cycle Over a 1 mF VCC Capacitor
www.onsemi.com
15
7
8
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
controller includes a novel circuitry made of two start−up
levels, Istart1 and Istart2. At power−up, as long as VCC is
below a 1.6 V level, the source delivers Istart2 (around
500 mA typical), then, when VCC reaches 1.6 V, the source
smoothly transitions to Istart1 and delivers its nominal value.
As a result, in case of short−circuit between VCC and GND,
the power dissipation will drop to 370 x 500 x 10−6 =
185 mW. Figure 35 portrays this particular behavior.
The first start−up period is calculated by the formula
C x V = I x t,
which
implies
a 1 x 10−6 x 1.6
6
/ (500 x 10− ) = 3.2 ms start−up time for the first sequence.
The second sequence is obtained by toggling the source to
8.9 mA
with
a
ΔV
of
VCC(ON) − VCC(TH) =
8.4 V – 1.6 V = 6.8 V, which finally leads to a second
start−up time of 1 x 10−6 x 6.8 / (8.9 x 10−3) = 0.76 ms.
The total start−up time becomes 3.2 ms + 0.76 ms =
3.96 ms. Please note that this calculation is approximated by
the presence of the knee in the vicinity of the transition.
As one can see, even if there is auxiliary winding to
provide energy for VCC, it happens that the device is still
biased by DSS during start−up time or some fault mode
when the voltage on auxiliary winding is not ready yet. The
VCC capacitor shall be dimensioned to avoid VCC crosses
VCC(OFF) level, which stops operation. The ΔV between
VCC(MIN) and VCC(OFF) is 0.5 V. There is no current source
to charge VCC capacitor when driver is on, i.e. drain voltage
is close to zero. Hence the VCC capacitor can be calculated
using
C VCC w
I CC1 @ D MAX
f OSC @ DV
(eq. 1)
Take the 65 kHz device as an example. CVCC should be
above
−3
C VCC + 1.45 @ 10 3 @ 0.73 + 36 nF
59 @ 10 @ 0.5
A margin that covers the temperature drift and the voltage
drop due to switching inside FET should be considered, and
thus a capacitor above 0.1 mF is appropriate.
The VCC capacitor has only a supply role and its value
does not impact other parameters such as fault duration or
the frequency sweep period for instance. As one can see on
Figure 34, an internal OVP comparator protects the switcher
against lethal VCC runaways. This situation can occur if the
feedback loop opto−coupler fails, for instance, and you
would like to protect the converter against an over−voltage
event. In that case, the over−voltage protection (OVP)
circuit immediately stops the output pulses for trecovery
duration (420 ms typically). Then a new start−up attempt
takes place to check whether the fault has disappeared or not.
The OVP paragraph gives more design details on this
particular section.
Fault Condition – Output Short−circuit
As soon as VCC reaches VCC(ON), drive pulses are
internally enabled. If everything is correct, the auxiliary
winding increases the voltage on the VCC pin as the output
voltage rises. During the start−sequence, the controller
smoothly ramps up the peak drain current to maximum
setting, i.e. IPK, which is reached after a typical period of
10 ms. When the output voltage is not regulated, the current
coming through FB pin is below IFBfault level (35 mA
typically), which is not only during the start−up period but
also anytime an overload occurs, an internal error flag is
asserted, IpFlag, indicating that the system has reached its
maximum current limit set−point. The assertion of this flag
triggers a fault counter tSCP (48 ms typically). If at counter
completion, IpFlag remains asserted, all driving pulses are
stopped and the part stays off in trecovery duration (about
420 ms). A new attempt to re−start occurs and will last
48 ms providing the fault is still present. If the fault still
affects the output, a safe burst mode is entered, affected by
a low duty−cycle operation (11%). When the fault
disappears, the power supply quickly resumes operation.
Figure 36 depicts this particular mode:
Fault Condition – Short−circuit on VCC
In some fault situations, a short−circuit can purposely
occur between VCC and GND. In high line conditions
(VHV = 370 V dc) the current delivered by the start−up
device will seriously increase the junction temperature. For
instance, since Istart1 equals 4.9 mA (the min corresponds to
the highest TJ), the device would dissipate
370 x 4.9 x 10−3 = 1.81 W. To avoid this situation, the
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16
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
VCC(ON)
VCC(MIN)
VCC
IpFlag
Open loop FB
VFB
48 ms typ.
Fault level
Timer
420 ms typ.
DRV
internal
Figure 36. In Case of Short−circuit or Overload, the NCP107xuz Protects Itself and the Power Supply Via a Low
Frequency Burst Mode. The VCC is Maintained by the Current Source and Self−supplies the Controller.
Auto−recovery Over−voltage Protection
is also recommended to filter out the VCC line to avoid
undesired OVP activations. Rlimit should be carefully
selected to suppress false−triggers of the OVP as we
discussed, but also to avoid disturbing the VCC in low / light
load conditions.
Self−supplying controllers in extremely low−standby
applications often puzzles the designer. Actually, if a SMPS
operated at nominal load can deliver an auxiliary voltage of
an arbitrary 16 V (Vnom), this voltage can drop below 10 V
(Vstby) when entering standby. This is because the
recurrence of the switching pulses expands so much that the
low frequency re−fueling rate of the VCC capacitor is not
enough to keep a proper auxiliary voltage.
The particular NCP107xuz arrangement offers a simple
way to prevent output voltage runaway when the
opto−coupler fails. As Figure 37 shows, a comparator
monitors the VCC pin. If the auxiliary winding delivers too
much voltage to the CVCC capacitor, then the controller
considers an OVP situation and stops the internal drivers.
When an OVP occurs, all switching pulses are permanently
disabled. After trecovery delay, the circuit resumes
operations. If the failure symptom still exists, e.g. feedback
opto−coupler fails, the device keeps the auto−recovery OVP
mode. We recommend the insertion of a resistor (Rlimit)
between the auxiliary dc level and the VCC pin to protect the
IC against high voltage spikes, which can damage the IC. It
DRAIN
V CC (ON ) = 8.4 V
V CC (MIN ) = 6.9 V
Istart 1
VCC
Shut down
Internal DRV
CVCC
80 ms
filter
D1
Rlimit
CAUX
GND
V OVP
Figure 37. A More Detailed View of the NCP107xuz Offers
Better Insight on How to Properly Wire an Auxiliary Winding
www.onsemi.com
17
N AUX
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
VOVP
VCC(ON)
VCC(MIN)
VCC
I FB
48 ms typ.
Fault level
Timer
420 ms typ.
DRV
internal
Figure 38. Describes the Main Signal Variations When the Part Operates in Auto−recovery OVP
Soft−start
OVP, TSD, Brown−out, etc. Figure 39 shows a typical
operating waveform. The NCP107xuz features a novel
patented structure which offers a better soft−start ramp,
almost ignoring the start−up pedestal inherent to traditional
current−mode supplies:
The NCP107xuz features a 10 ms soft−start which
reduces the power−on stress but also contributes to lower
the output overshoot. Soft−start is running every time when
IC starts switching. It means a first start, a new start after
VCC
VCC(ON)
0V (fresh PON)
Max IPK
DRAIN current
10 ms
Figure 39. The 10 ms Soft−start Sequence
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18
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
Jittering
Frequency jittering is a method used to soften the EMI
signature by spreading the energy in the vicinity of the main
switching component. The NCP107xuz offers a ±6%
deviation of the nominal switching frequency. The sweeping
sawtooth is internally generated and modulates the clock up
and down with a fixed frequency of 300 Hz. Figure 40 shows
the relationship between the jitter ramp and the frequency
deviation. It is not possible to externally disable the jitter.
Jitter ramp
68.9 kHz
65 kHz
Internal
sawtooth
61.1 kHz
adjustable
Figure 40. Modulation Effects on the Clock Signal by the Jittering Sawtooth
Line Detection
If the drain voltage is lower than the internal threshold
VHV(EN) (91 V dc typically), the internal power switch is
inhibited. This avoids operating at too low ac input.
When BO/AC_OVP pin is grounded (voltage on this pin
is below VBO(EN)) Figure 2, then an internal comparator
monitors the drain voltage as recovering from one of the
following situations:
• Short−Circuit Protection,
• VCC OVP is Confirmed,
• UVLO
• TSD
Brown−out Function, Ac Line Over−voltage Protection
The Brown−out circuitry offers a way to protect the
application from operation under too low an input voltage.
Below a given level, the controller blocks the output pulses,
above it, it authorizes them. The internal circuitry, depicted
by Figure 41, offers a way to observe the high−voltage (HV)
rail.
VBULK
RUPPER
RLOWER
BO/AC_OVP
20μs
filter
CBO
Line
detection
disable
VBO(EN)
20μs
filter
tBO
VBO(ON)
20μs
filter
AC OVP
VAC(OVP)
Figure 41. The Internal Brown−out Configuration
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19
BO enable
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
higher than VBO(ON), switcher starts pulsing. If voltage falls
down under VBO(OFF) − level VBO(ON) minus VBO(HYST),
the switcher waits 50 ms and then stops pulsing, depicted by
Figure 42. Bulk voltage at which IC starts switching is set by
resistive divider.
A resistive divider made of RUPPER and RLOWER, brings
a portion of the HV rail on BO/AC_OVP pin. Below the
VBO(EN) = 50 mV is the Brown−out function disabled, over
the VBO(EN) Brown−out function is enable and against Line
detection is inhibited. If voltage on BO/AC_OVP pin is
VCC(ON)
VCC(MIN)
VCC
VBO(ON)
V BO(OFF)
V BO/AC_OVP
50 ms
Timer
DRV
internal
Figure 42. Brown−out Input Functionality with 50 ms Timer
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20
50 ms
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
The IC also includes over−voltage protection. If the voltage on BO/AC_OVP pin exceed VACOVP(ON), the switcher
immediately stops pulsing until the voltage on BO/AC_OVP pin drops under VACOVP(OFF), depicted by Figure 43.
VCC(ON)
VCC(MIN)
VCC
VACOVP(ON)
VAVOVP(OFF)
VBO(ON)
VBO(OFF)
VBO/AC_OVP
DRV
internal
Figure 43. Brown−out Input Functionality with Ac Line OVP Function
Calculation of the resistive divider:
V BO(ON)
R LOWER
+
R UPPER
V BULK * V BO(ON)
(eq. 2)
If we decide to start pulsing at VBULK(ON) = 113 V dc (80 V rms at ac mains):
V BO(ON)
R LOWER
0.8
+
+
[ 7.1 m
113 * 0.8
R UPPER
V BULK(ON) * V BO(ON)
We choose RLOWER = 100 kW
3
R UPPER + 100 @ 10−3 + 14 MW
7.1 @ 10
Then power losses on resistive divider for worst case (VBULK = 409 V dc)
2
U2
409 2
P+U@I+U +
+
+ 12 mW
R
R UPPER ) R LOWER
14 @ 10 6 ) 100 @ 10 3
(eq. 3)
For VBULK(ON) = 113 V dc will be over−voltage protection (voltage when the switcher stops pulsing):
V BULK(OVP) + V ACOVP(ON) @
V BULK(ON)
R LOWER ) R UPPER
+ V ACOVP(ON) @
+ 29 @ 113 + 409 Vdc + 290 Vrms (eq. 4)
0.8
R LOWER
V BO(ON)
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21
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
VCC(ON)
VCC(MIN)
VCC
VBO(ON)
VBO(OFF)
VBO/AC_OVP
50 ms
Timer
Soft−start
Soft−start
Drain
current
Figure 44. Brown−out Functionality in Soft−start
around 68 mA. At this point, the oscillator enters frequency
foldback and reduces its switching frequency.
The internal peak current set−point is following the
feedback current information until its level reaches the
minimal freezing level point of Ifreeze. Below this value, the
peak current set−point is frozen to 30% of the IPK(0). The
only way to further reduce the transmitted power is to
diminish the operating frequency down to fMIN (27 kHz
typically). This value is reached at a feedback current level
of IFBfold(END) (100 mA typically). Below this point, if the
output power continues to decrease, the part enters skip
cycle for the best noise−free performance in no−load
conditions. Figures 45 and 46 depict the adopted scheme for
the part.
If voltage on VCC pin is higher than VCC(ON) and voltage
on BO/AC_OVP pin is higher than VBO(ON) then IC starts
pulsing, drain current is increasing for 10 ms (Soft−start).
Brown−out is inhibited during Soft−start, when Soft−start
ended, Brown−out checked if is voltage on BO/AC_OVP
pin higher than VBO(OFF). If the voltage is lower, timer count
50 ms and if the voltage don’t increase over VBO(OFF) then
IC stops switching as one can see on Figure 44.
Frequency Foldback
The reduction of no−load standby power associated with
the need for improving the efficiency, requires to change the
traditional fixed−frequency type of operation. This device
implements a switching frequency folback when the
feedback current passes above a certain level, IFBfold, set
www.onsemi.com
22
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
140
130 kHz
Frequency [kHz]
120
100 kHz
100
65 kHz
80
60
40
20
0
50
60
70
80
90
100
IFB [mA]
Figure 45. By Observing the Current on the FB pin, the Controller Reduces its
Switching Frequency for an Improved Performance at Light Load
Current set point [mA]
1400
NCP1079uz
1200
NCP1077uz
1000
NCP1076uz
NCP1075uz
800
600
400
200
0
40
50
60
70
80
90
100
110
IFB [mA]
Figure 46. IPK Set−point is Frozen at Lower Power Demand
Feedback and Skip
The FB pin operates linearly as the absolute value of
feedback current (IFB) is above 40 mA. In this linear
operating range, the dynamic resistance is 19.5 kW typically
(RFB(UP)) and the effective pull up voltage is 3.3 V typically
(VFB(REF)). When IFB is decreased, the FB voltage will
increase to 3.3 V.
www.onsemi.com
23
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
Figure 47 depicts the skip mode block diagram. When the
FB current information reaches IFB(skip), the internal clock
to set the flip−flop is blanked and the internal consumption
of the controller is decreased. The hysteresis of internal skip
Jittering
comparator is minimized to lower the ripple of the auxiliary
voltage for VCC pin and VOUT of power supply during skip
mode. It easies the design of VCC overload range.
OSC
V FB (REF )
S
Foldback
Q
DRV stage
R
R FB (UP )
IFB (skip )
SKIP
CS comparator
FB
Figure 47. Skip Cycle Schematic
Over−power Protection
This function lets you limit the maximum dc output current regardless of the operating input voltage. For a correct operation,
the BO/AC_OVP pin must be connected via a resistive divider to observe the bulk voltage.
OSC
S
Q
MOSFET
R
Vramp + Vsense
VBULK
IFB
IFB to CS setpoint
RUPPER
Ifreeze
BO/AC_OVP
IPK(0)
IPK (0)
IPK (OPP )
VBO (ON )
2.65 V
RLOWER
Figure 48. The OPP Circuity Affects the Maximum Peak
Current Set−point in Relationship to the Input Voltage.
www.onsemi.com
24
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
1300
Max current set-point [mA]
1200
1100
1000
900
NCP1079uz
800
NCP1077uz
700
NCP1076uz
600
NCP1075uz
500
400
300
0
0.5
1.0
1.5
2.0
2.5
3.0
VBO/ACOVP [V]
Figure 49. Current Set−point Dependence on BO/AC_OVP Pin Voltage
There are several known ways to implement Over−power
Protection (OPP), all suffering from particular problems.
These problems range from the added consumption burden
on the converter or the skip−cycle disturbance brought by
the current−sense offset. In this case is added consumption
due to resistive divider (Equation 2).
Maximum peak current is reduced internally according to
bulk voltage. When VBO(OPP) is maximum, the peak current
set−point is reduced by 10%. Bulk voltage at which will be
maximum current peak reduced by 20% (10% in
NCP1075uz):
(eq. 5)
) R UPPER
R
3
6
V BULK(OPP) + V BO(OPP) @
+ V BO(OPP) @ LOWER
+ 2.65 @ 100 @ 10 ) 143 @ 10 + 375 Vdc + 265 Vrms
V BO(ON)
R LOWER
100 @ 10
V BULK(ON)
www.onsemi.com
25
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
Second LEB – Peak Current Protection (NCP107xuA
only)
Slope Compensation and IPK Set−point
In order to let the NCP107xuz operate in CCM with a
duty−cycle above 50%, a fixed slope compensation is
internally applied to the current−mode control.
Below appears a table of the slope compensation level, the
initial current set−point, and the final current set−point of
different versions of switcher.
There is a second level of current protection with 100 ns
propagation delay to prevent IC against high peak current.
If peak current is 150% max peak current limit, then the
controller stops switching after three pulses and waits for an
auto−recovery period (trecovery) before attempting to
re−start.
NCP1075uz
fSW [kHz]
65
Sa [mA/µs]
9
NCP1076uz
100
130
65
14
18
15
NCP1077uz
100
130
65
23
30
18
NCP1079uz
100
130
65
28
36
24
100
130
37
46
IPK (Duty−cycle = 50%) [mA]
400
600
800
1050
IPK(0) [mA]
470
765
940
1230
Figure 50 depicts the variation of IPK set−point vs. the power switcher duty ratio, which is caused by the internal ramp
compensation.
1400
IIPK set-point [mA]
1200
1000
800
NCP1079uz
600
NCP1077uz
NCP1076uz
400
NCP1075uz
200
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Duty Ratio [%]
Figure 50. IPK Set−point varies with Power Switch On Time, which is Caused by the Ramp Compensation
www.onsemi.com
26
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
Design Procedure
maximum voltage that can be reflected during tF
As a result, the flyback voltage which is reflected
on the drain at the switch opening cannot be larger
than the input voltage. When selecting
components, you thus must adopt a turn ratio
which adheres to the following equation:
The design of an SMPS around a monolithic device does
not differ from that of a standard circuit using a controller
and a MOSFET. However, one needs to be aware of certain
characteristics specific of monolithic devices. Let us follow
the steps:
VIN,MIN = 90 V rms or 127 V dc once rectified,
assuming a low bulk ripple
VIN,MAX = 265 V rms or 375 V dc
VOUT = 12 V
POUT = 10 W
Operating mode is CCM
η = 0.8
1. The lateral MOSFET body−diode shall never be
forward biased, either during start−up (because of
a large leakage inductance) or in normal operation,
depicted by Figure 51. This condition sets the
N @ ǒV OUT ) V FǓ t V IN,MIN
(eq. 6)
2. In our case, since we operate from a 127 V dc rail
while delivering 12 V, we can select a reflected
voltage of 120 V dc maximum. Therefore, the turn
ratio Np:Ns must be smaller than
V reflect
+ 120 + 9.6 or Np : Ns t 9.6
12 ) 0.5
V OUT ) V F
Here we choose N = 8 in this case. We will see later
on how it affects the calculation.
Figure 51. The Drain−Source Wave Shall Always be Positive
3. Lateral MOSFETs have a poorly doped
body−diode which naturally limits their ability to
sustain the avalanche. A traditional RCD clamping
network shall thus be installed to protect the
MOSFET. In some low power applications,
a simple capacitor can also be used since
IL
IPEAK
ILavg
DIL
IVALLEY
V DRAIN,MAX +
V IN ) N @ ǒV OUT ) V FǓ ) I PEAK @
L F (eq. 7)
C TOT
where LF is the leakage inductance, CTOT the total
capacitance at the drain node (which is increased by
the capacitor you will wire between drain and
source), N the NP:NS turn ratio, VOUT the output
voltage, VF the secondary diode forward drop and
finally, IPEAK the maximum peak current. Worse
case occurs when the SMPS is very close to
regulation, e.g. the VOUT target is almost reached
and IPEAK is still pushed to the maximum. For this
Iavg
t
DTsw
Ǹ
Tsw
Figure 52. Primary Inductance Current
Evolution in CCM
www.onsemi.com
27
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
design, we have selected our maximum voltage
around 650 V (at VIN = 375 V dc). This voltage is
given by the RCD clamp installed from the drain to
the bulk voltage. We will see how to calculate it later
on.
4. Calculate the maximum operating duty−cycle for
this flyback converter operated in CCM:
D MAX +
N @ ǒV OUT ) V FǓ
N @ ǒV OUT ) V FǓ ) V IN,MIN
1
VIN,MIN
1)
+
5. To obtain the primary inductance, we have the
choice between two equations:
L+
where
(eq. 8)
•
+ 0.44
N@(VOUT)VF)
•
ǒV IN @ DǓ
2
f SW @ K @ P IN
K+
DI L
I Lavg
(eq. 9)
(eq. 10)
and defines the amount of ripple we want in CCM,
depicted by Figure 51.
Small K: deep CCM, implying a large primary
inductance, a low bandwidth and a large leakage
inductance.
Large K: approaching DCM where the conduction
losses are worse, but smaller inductance, leading to a
better leakage inductance.
From Equation 9, a K factor of 1 (50% ripple), gives an inductance of:
2
L+
(127 @ 0.44)
+ 3.8 mH
65 k @ 1 @ 12.75
DI L +
V IN @ D
127 @ 0.44
+
+ 223 mA
L @ f SW
3.8 @ 10 −3 @ 65 @ 10 3
(eq. 11)
peak−to−peak
The peak current can be evaluated to be:
I PEAK +
I avg DI L
−3
−3
)
+ 98 @ 10 ) 223 @ 10 + 335 mA
2
0.44
2
D
(eq. 12)
On IL, ILavg can also be calculated
I Lavg + I PEAK *
DI L
−3
+ 335 @ 10 −3 * 223 @ 10 + 223 mA
2
2
(eq. 13)
6. Based on the above numbers, we can now evaluate the conduction losses:
I D,RMS +
Ǹǒ
D I PEAK 2 * I PEAK @ DI L )
Ǔ Ǹ
DI L 2
+
3
ǒ
0.44 0.335 2 * 0.335 @ 0.223 ) 0.223
3
2
Ǔ + 154 mA
(eq. 14)
If we take the maximum RDS(ON) for a 125°C junction temperature, i.e. 10.1 W, then conduction losses worse case are:
P COND + I D,RMS 2 @ R DS(ON) + ǒ154 @ 10 −3Ǔ @ 13.6 + 323 mW
2
(eq. 15)
7. Off−time and on−time switching losses can be estimated based on the following calculations:
P OFF +
I PEAK @ (V BULK ) V CLAMP) @ t F
0.335 @ (127 ) 120 @ 2) @ 10 @ 10 −9
+
+ 40 mW
2 @ T SW
2 @ 15.4 @ 10 −6
(eq. 16)
Where, assume the VCLAMP is equal to 2 times of reflected voltage.
P ON +
I VALLEY @ ǒV BULK ) N @ (V OUT ) V F)Ǔ @ t R
6 @ T SW
+
0.112 @ (127 ) 100) @ 20 @ 10 −9
+ 5.5 mW
6 @ 15.4 @ 10 −6
(eq. 17)
It is noted that the overlap of voltage and current seen on MOSFET during turning on and off duration is dependent on the
snubber and parasitic capacitance seen from drain pin. Therefore the tF and tR in Equations 16 and 17 have to be modified after
measuring on the bench.
8. The theoretical total power is then
P MOSFET + 323 ) 40 ) 5.5 + 368.5 mW
9. If the NCP107xuz operates at DSS mode, then the losses caused by DSS mode should be counted as losses of this
device on the following calculation:
P DSS + I CC1 @ V IN,MAX + 1.5 @ 10 −3 @ 375 + 563 mW
www.onsemi.com
28
(eq. 18)
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
MOSFET Protection
As in any flyback design, it is important to limit the drain excursion to a safe value, e.g. below the MOSFET BVDSS which
is 700 V. Figure 53 a−b−c present possible implementations:
Figure 53. Different Options to Clamp the Leakage Spike
Figure 53a: the simple capacitor limits the voltage
according to the lateral MOSFET body−diode shall never be
forward biased, either during start−up (because of a large
leakage inductance) or in normal operation as shown by
Figure 51. This condition sets the maximum voltage that can
be reflected during tF. As a result, the flyback voltage which
is reflected on the drain at the switch opening cannot be
larger than the input voltage. When selecting components,
you must adopt a turn ratio which adheres to the following
Equation 6. This option is only valid for low power
applications, e.g. below 5 W, otherwise chances exist to
destroy the MOSFET. After evaluating the leakage
inductance, you can compute C with (Equation 7). Typical
values are between 100 pF and up to 470 pF. Large
capacitors increase capacitive losses...
Figure 53b: the most standard circuitry is called the RCD
network. You calculate RCLAMP and CCLAMP using the
following formulae:
R CLAMP +
C CLAMP +
and a MUR160 represents a good choice. One major
drawback of the RCD network lies in its dependency upon
the peak current. Worse case occurs when IPEAK and VIN are
maximum and VOUT is close to reach the steady−state value.
Figure 53c: this option is probably the most expensive of
all three but it offers the best protection degree. If you need
a very precise clamping level, you must implement a Zener
diode or a TVS. There are little technology differences
behind a standard Zener diode and a TVS. However, the die
area is far bigger for a transient suppressor than that of Zener.
A 5 W Zener diode like the 1N5388B will accept 180 W
peak power if it lasts less than 8.3 ms. If the peak current in
the worse case (e.g. when the PWM circuit maximum
current limit works) multiplied by the nominal zener voltage
exceeds these 180 W, then the diode will be destroyed when
the supply experiences overloads. A transient suppressor
like the P6KE200 still dissipates 5 W of continuous power
but is able to accept surges up to 600 W @ 1 ms. Select the
Zener or TVS clamping level between 40 to 80 volts above
the reflected output voltage when the supply is heavily
loaded.
As a good design practice, it is recommended to
implement one of this protection to ensure a maximum drain
pin voltage below 650 V (to have some margin between
drain pin voltage and BVDSS) during most stringent
operating conditions (high VIN and peak power condition).
2 @ V CLAMP ǒV CLAMP ) (V OUT ) V F) @ NǓ
L LEAK @ I LEAK 2 @ f SW
V CLAMP
V RIPPLE @ f SW @ R CLAMP
(eq. 19)
(eq. 20)
VCLAMP is usually selected 50−80 V above the reflected
value N x (VOUT + VF ). The diode needs to be a fast one
www.onsemi.com
29
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
Power Dissipation and Heatsinking
The NCP107xuz welcomes two dissipating terms, the
DSS current−source (when active) and the MOSFET. Thus,
PTOT = PDSS + PMOSFET. It is mandatory to properly
manage the heat generated by losses. If no precaution is
taken, risks exist to trigger the internal thermal shutdown
(TSD). To help dissipating the heat, the PCB designer must
foresee large copper areas around the package. Take the
PDIP−7 package as an example, when surrounded by a
surface approximately 200 mm2 of 35 mm copper, the
maximum power the device can thus evacuate is:
P MAX +
T J(max) * T AMB(max)
R qJA
(eq. 21)
which gives around 1300 mW for an ambient of 50°C and
a maximum junction of 150°C. If the surface is not large
enough, the RqJA is growing and the maximum power the
device can evacuate decreases. Figure 54 gives a possible
layout to help drop the thermal resistance.
Figure 54. A Possible PCB Arrangement to Reduce
the Thermal Resistance Junction−to−Ambient
Bill of Material:
C1
C2, R1, D1
C3
OK1
www.onsemi.com
30
Bulk capacitor, input dc voltage is
connected to the capacitor
Clamping elements
VCC capacitor
Opto−coupler
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
ORDERING INFORMATION
Device
Frequency
[kHz]
RDS(ON)
[W]
IPK
[mA]
Soft−start
Package Type
NCP1075AAP065G
65
13.5
400
enabled
PDIP8 (Less pin#6)
NCP1075AAP100G
100
13.5
400
enabled
PDIP8 (Less pin#6)
NCP1075BAP065G
65
13.5
400
enabled
PDIP8 (Less pin#3)
NCP1075BAP100G
100
13.5
400
enabled
PDIP8 (Less pin#3)
NCP1075BAP130G
130
13.5
400
enabled
PDIP8 (Less pin#3)
NCP1076AAP065G
65
4.8
650
enabled
PDIP8 (Less pin#6)
NCP1076AAP100G
100
4.8
650
enabled
PDIP8 (Less pin#6)
NCP1076BAP065G
65
4.8
650
enabled
PDIP8 (Less pin#3)
NCP1076BAP100G
100
4.8
650
enabled
PDIP8 (Less pin#3)
NCP1076BAP130G
130
4.8
650
enabled
PDIP8 (Less pin#3)
NCP1077AAP065G
65
4.8
800
enabled
PDIP8 (Less pin#6)
NCP1077AAP100G
100
4.8
800
enabled
PDIP8 (Less pin#6)
NCP1077BAP065G
65
4.8
800
enabled
PDIP8 (Less pin#3)
NCP1077BAP100G
100
4.8
800
enabled
PDIP8 (Less pin#3)
NCP1077BAP130G
130
4.8
800
enabled
PDIP8 (Less pin#3)
NCP1079AAP065G
65
2.9
1050
enabled
PDIP8 (Less pin#6)
NCP1079AAP100G
100
2.9
1050
enabled
PDIP8 (Less pin#6)
NCP1079BAP065G
65
2.9
1050
enabled
PDIP8 (Less pin#3)
NCP1079BAP100G
100
2.9
1050
enabled
PDIP8 (Less pin#3)
NCP1079BAP130G
130
2.9
1050
enabled
PDIP8 (Less pin#3)
NCP1075ABP065G
65
13.5
400
disabled
PDIP8 (Less pin#6)
NCP1075ABP100G
100
13.5
400
disabled
PDIP8 (Less pin#6)
NCP1075BBP065G
65
13.5
400
disabled
PDIP8 (Less pin#3)
NCP1075BBP100G
100
13.5
400
disabled
PDIP8 (Less pin#3)
NCP1075BBP130G
130
13.5
400
disabled
PDIP8 (Less pin#3)
NCP1076ABP065G
65
4.8
650
disabled
PDIP8 (Less pin#6)
NCP1076ABP100G
100
4.8
650
disabled
PDIP8 (Less pin#6)
NCP1076BBP065G
65
4.8
650
disabled
PDIP8 (Less pin#3)
NCP1076BBP100G
100
4.8
650
disabled
PDIP8 (Less pin#3)
NCP1076BBP130G
130
4.8
650
disabled
PDIP8 (Less pin#3)
NCP1077ABP065G
65
4.8
800
disabled
PDIP8 (Less pin#6)
NCP1077ABP100G
100
4.8
800
disabled
PDIP8 (Less pin#6)
NCP1077BBP065G
65
4.8
800
disabled
PDIP8 (Less pin#3)
NCP1077BBP100G
100
4.8
800
disabled
PDIP8 (Less pin#3)
NCP1077BBP130G
130
4.8
800
disabled
PDIP8 (Less pin#3)
NCP1079ABP065G
65
2.9
1050
disabled
PDIP8 (Less pin#6)
NCP1079ABP100G
100
2.9
1050
disabled
PDIP8 (Less pin#6)
NCP1079BBP065G
65
2.9
1050
disabled
PDIP8 (Less pin#3)
NCP1079BBP100G
100
2.9
1050
disabled
PDIP8 (Less pin#3)
NCP1079BBP130G
130
2.9
1050
disabled
PDIP8 (Less pin#3)
www.onsemi.com
31
Shipping
50 Units /
Rail
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
PACKAGE DIMENSIONS
PDIP−7 (PDIP−8 LESS PIN 6)
CASE 626A
ISSUE C
D
A
E
H
8
5
1
4
E1
NOTE 8
c
b2
B
END VIEW
TOP VIEW
WITH LEADS CONSTRAINED
NOTE 5
A2
A
e/2
NOTE 3
L
SEATING
PLANE
A1
C
M
D1
e
8X
SIDE VIEW
b
0.010
eB
END VIEW
M
C A
M
B
M
NOTE 6
www.onsemi.com
32
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994.
2. CONTROLLING DIMENSION: INCHES.
3. DIMENSIONS A, A1 AND L ARE MEASURED WITH THE PACKAGE SEATED IN JEDEC SEATING PLANE GAUGE GS−3.
4. DIMENSIONS D, D1 AND E1 DO NOT INCLUDE MOLD FLASH
OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS ARE
NOT TO EXCEED 0.10 INCH.
5. DIMENSION E IS MEASURED AT A POINT 0.015 BELOW DATUM
PLANE H WITH THE LEADS CONSTRAINED PERPENDICULAR
TO DATUM C.
6. DIMENSION eB IS MEASURED AT THE LEAD TIPS WITH THE
LEADS UNCONSTRAINED.
7. DATUM PLANE H IS COINCIDENT WITH THE BOTTOM OF THE
LEADS, WHERE THE LEADS EXIT THE BODY.
8. PACKAGE CONTOUR IS OPTIONAL (ROUNDED OR SQUARE
CORNERS).
DIM
A
A1
A2
b
b2
C
D
D1
E
E1
e
eB
L
M
INCHES
MIN
MAX
−−−−
0.210
0.015
−−−−
0.115 0.195
0.014 0.022
0.060 TYP
0.008 0.014
0.355 0.400
0.005
−−−−
0.300 0.325
0.240 0.280
0.100 BSC
−−−−
0.430
0.115 0.150
−−−−
10 °
MILLIMETERS
MIN
MAX
−−−
5.33
0.38
−−−
2.92
4.95
0.35
0.56
1.52 TYP
0.20
0.36
9.02
10.16
0.13
−−−
7.62
8.26
6.10
7.11
2.54 BSC
−−−
10.92
2.92
3.81
−−−
10 °
NCP1075A/B, NCP1076A/B, NCP1077A/B, NCP1079A/B
PACKAGE DIMENSIONS
PDIP8 LESS PIN 3
CASE 626AS
ISSUE O
D
A
E
8
H
5
A3
E1
1
4
NOTE 6
c
b2
B
END VIEW
TOP VIEW
WITH LEADS CONSTRAINED
NOTE 5
e/2
A
NOTE 3
L
SEATING
PLANE
A1
C
M
D1
7X
e
b
0.010
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994.
2. CONTROLLING DIMENSION: INCHES.
3. DIMENSIONS A, A1 AND L ARE MEASURED WITH THE PACKAGE SEATED IN JEDEC SEATING PLANE GAUGE GS−3.
4. DIMENSIONS D, D1 AND E1 DO NOT INCLUDE MOLD FLASH
OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS ARE
NOT TO EXCEED 0.10 INCH.
5. DIMENSION E IS MEASURED AT A POINT 0.015 BELOW DATUM
PLANE H WITH THE LEADS CONSTRAINED PERPENDICULAR
TO DATUM C.
6. PACKAGE CONTOUR IS OPTIONAL (ROUNDED OR SQUARE
CORNERS).
DIM
A
A1
A3
b
b2
c
D
D1
E
E1
e
L
M
INCHES
MIN
MAX
0.155 0.175
0.020 0.040
0.015 BSC
0.015 0.020
0.056 0.064
0.008 0.012
0.365 0.369
0.005 0.080
0.300 0.325
0.244 0.260
0.100 BSC
0.115 0.135
−−−−
10 °
MILLIMETERS
MIN
MAX
3.94
4.45
0.51
1.02
0.38 BSC
0.38
0.50
1.42
1.63
0.20
0.30
9.27
9.37
0.13
2.03
7.62
8.25
6.20
6.60
2.54 BSC
2.92
3.43
−−−
10 °
END VIEW
M
C A
M
B
M
SIDE VIEW
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