Wide Mains, 19V, 8A Power Supply Including Power Factor Correction

AND8292
Wide Mains, 19 V / 8 A
Power Supply Including
Power Factor Correction
Prepared by: Joël Turchi,
ON Semiconductor
http://onsemi.com
Introduction
• AC line range: 90 V up to 265 V
• Output Voltage: 19 V/8 A
• IEC61000-3-2 Class D compliant
When associated to forward or half-bridge converters
taking advantage of a narrow input voltage range, the PFC
stage should be designed to start first and to remain active as
long as the power supply is plugged in. More specifically,
the downstream converter turns on and operates while the
output of the PFC stage is nominal. In other words, the PFC
must be the master.
The goal of this application note is to give more
information on the practical implementation of this
application and to present the performance of the solution.
The power supply consists of two stages:
• A PFC pre-converter that provides the main converter
with a stable 390 Vdc input voltage
• The main conversion stage that is a 2-switch forward
operating at 133 kHz
The 2-switch forward is driven by the NCP1217A.
Housed in a SOIC-7 or PDIP-7 package, the NCP1217A
eases the design of modern ac-dc adapters and offers a true
alternative to UC384X-based designs. This circuit is ideal
for 2-switch forward converters. It limits the duty-cycle
below 50% and its current mode control topology provides
an excellent input audio susceptibility and inherent
pulse-by-pulse control.
In addition, when the current set point falls below a given
value; e.g., when the output power demand diminishes, the
IC automatically enters the so-called skip cycle mode and
provides high efficiency at light loads. Because this occurs
at a user adjustable low peak current, no acoustic noise takes
place. For more information, please refer to
http://www.onsemi.com/PowerSolutions/product.do?id=N
CP1217A.
The NCP1605 is a Power Factor Controller especially
designed to meet these requirements.
This driver features a “pfcOK” pin to enable the
downstream converter when the PFC stage is ready for
operation. Practically, it is in high state when the output
voltage of the PFC stage is within regulation and low
otherwise (fault or startup condition). In addition, the PFC
stage having to remain active in light load conditions, the
NCP1605 integrates the skip cycle capability to lower the
standby losses to a minimum. For more information on this
device,
please
refer
to
the
datasheet
at
(http://www.onsemi.com/PowerSolutions/product.do?id=
NCP1605).
Application
Note
AND8281
available
at:
(http://www.onsemi.com/pub/Collateral/AND8281- D.PDF)
gives the main dimensioning criteria/equations for a
NCP1605 driven application. For the sake of clarity, this
process is illustrated in the following practical application:
© Semiconductor Components Industries, LLC, 2007
June, 2007 - Rev. 0
1
Publication Order Number:
AND8292/D
AND8292
Figure 1. The Board
http://onsemi.com
2
http://onsemi.com
3
Figure 2. Application Schematic - PFC Stage
F1
N
C13
2.2 nF
Type = Y2
Earth
90-265 Vrms
L
C11
330nF
Type = X2
CM2
150mH
CM1
IN
C12
2.2 nF
Type = Y2
C15
330nF
Type = X2
U1
KBU6K
-
+
Vramp
R1
1800k
C1
330nF
Type = X2
Vin
pin6
C8
220nF
R58
22k
DRV1
R8
4.7k
R52
6.8k
R15
62k
R3
1800k
R4
1800k
R16
1800k
R6
2.4 k
R7
0.1
C3
4.7 nF
pin6
C37
1 nF
Vramp
R2
150
C22
680 nF
C6
220 μF
Vcc
T1x
150μH (np/ns=9)
9
10
11
12
13
14
15
16
R17
27k
NCP1605
8
7
6
5
4
3
2
1
C14
1 nF
C4
390 pF
STBY
Vcc
DRV1
C17
220 nF
pfcOK
R21
27k
R23
820k
R24
560k
C30
1 nF
R12
47
R22
1800k
R14
1800k
Q2
BC369
R11
1k
C5
10 nF
D3
16 V
R42
100
Vcc
R13
2.2
Vbulk
D2
1N4148
R20
1800k
R9
1800k
R10
10k
Vbulk
M1x
SPP20N60S
C2
100 uF / 450 V
D1
MUR460
AND8292
R46
22k
C33
1 nF
C34
1 nF
D14
1N5817
R45
0R
Figure 3. Application Schematic - 2 Switch Forward Converter
http://onsemi.com
4
C31
220μF
5
6
3
4
7
8
2
1
Vcc
Vz
C20
1 μF
R51
10k
R39
47
D8
1N4148
Q7
BC368
SGND
Vbulk
D9
16V
R31
10 k
NCP1217A
C25
2.2 nF
Type = Y2
Q1
BC369
C32
100 nF
Q5
BC368
R50
10
Vcc
C28
100μF / 50V
D15
1N4934
D17
1N4148
R44
2.2
X25
Vaux
STBY
R40
10
R36
10
D10
100nF
R37
10k
Vaux
D12
MUR160E
D18
16 V
FB
D20
16 V
R38
10k
T2
800 μH
K = Np/Ns=7; Np/Naux=14
R18
22k
R28
47k
R25
0.33 / 3 W
X24
SPP11N60
X31
SPP11N60
R1x
43k
D16
3V0
C26
1 μF
3
1
D6
D7
SGND
X30
TL431
FB
2
MBR20100CT
R55
1k
R56
0R
OVL detection
D13
MUR160E
Q1x
BC846B
Vcc
Note: the board is designed to also give the possibility to have the two MOSFETs of the 2­switch forward
converter driven through a transformer. Some components (diodes D11, D19 and D21) that are necessary
for this option, are useless in the presented version where only the high­side one is controlled through a
transformer. They are short circuited in the board and, hence, they are not visible in this schematic.
R43
1k
C35
1nF
FB
R49
6.8 k
pfcOK
C21
2.2 nF
Type = Y2
FB
R29
3.3k
X29
SFH615A-4
19 V / 8 A
C23
10nF
R57
1k
R30
3.3k
C29
470 μF / 25 V
C18
470 μF / 25 V
C19
1 μF
Vbulk
SGND
R35
100 / 2 W
C27
470 pF
L1
26 μH
Q6
BC368
FB
R27
22k
AND8292
AND8292
Figure 4. PCB Layout - Silkscreen Top
Figure 5. PCB Layout - Silkscreen Bottom
http://onsemi.com
5
AND8292
Figure 6. PCB Layout - Bottom Layer
http://onsemi.com
6
AND8292
IIN: AC Line Current (5 A/div)
VBULK (CH1)
19 V Output
Voltage (CH2)
VIN,RMS = 120 V, Pin = 183 W, IOUT = 8 A, PF = 0.992, THD = 10%
IIN: AC Line Current (5 A/div)
VBULK (CH1)
VBULK (CH3)
19 V Output
Voltage (CH2)
VIN,RMS = 230 V, Pin = 177 W, IOUT = 8 A, PF = 0.976, THD = 17%
Figure 7. General Behavior - Typical Waveforms
http://onsemi.com
7
AND8292
Table 1. Power Factor and Efficiency
VIN, RMS
PIN, AVG
PF
THD
VBULK
VOUT (19 V)
VOUT (19 V)
Efficiency
(V)
(W)
(-)
(%)
(V)
(V)
(A)
(%)
90
28.2
0.966
24
381
19.23
1.00
68.2
90
70.5
0.991
13
381
19.23
3.00
81.8
90
114.5
0.995
9
381
19.23
5.00
84.0
90
183.2
0.990
13
363
19.23
8.00
83.9
120
27.7
0.961
20
381
19.23
1.00
69.4
120
70.3
0.987
13
381
19.23
3.00
81.1
120
113.2
0.992
11
381
19.23
5.00
83.9
120
180.3
0.997
10
381
19.23
8.00
85.3
230
28.0
0.806
28
381
19.23
1.00
68.7
230
69.2
0.940
20
381
19.23
3.00
83.4
230
112.0
0.966
18
381
19.23
5.00
85.8
230
177.4
0.976
17
381
19.23
8.00
86.7
265
27.8
0.696
52
389
19.23
1.00
69.2
265
68.6
0.901
26
381
19.23
3.00
84.1
265
111.9
0.950
21
381
19.23
5.00
85.9
265
176.9
0.950
28
381
19.23
8.00
86.9
*At full load, the efficiency remains above 83.9%.
http://onsemi.com
8
AND8292
Startup Sequencing at 120 Vrms and IOUT = 8 A
Load Current (5 A/div)
VBULK (100 V/div)
pfcOK Signal
VIN Rectified Line Voltage (100 V/div)
Figure 8. Startup Phase at 120 Vrms and IOUT = 8 A
When the PFC output voltage (VBULK) reaches its
nominal voltage (about 382 V), the circuit detects the end of
the startup phase. The «pfcOK» pin turns high allowing the
downstream converter operation.
http://onsemi.com
9
AND8292
Load Current (5 A/div)
VBULK (100 V/div)
pfcOK Signal
VIN Rectified Line Voltage (100 V/div)
Figure 9. Zoom of the Precedent Plot
as soon as VBULK has dropped below 95.5% of its nominal
level. This behavior avoids any overshoot during the startup
sequence from occurring.
We can note some skipping sequence that takes place after
«pfcOK» has turned high. This is because the NCP1605
standby management block is controlled by the feedback
signal of the main converter. The PFC stage recovers activity
http://onsemi.com
10
AND8292
Load Current (5 A/div)
VBULK (100 V/div)
pfcOK Signal
19 V Output Voltage (10 V/div)
Figure 10. Startup Phase at 120 Vrms
Compared to the precedent one, Figure 10 further shows the 19 V output.
Overload / Short Circuit Protections
This circuitry protects the circuit in case of short circuit on
the 19 V output. In this situation, the power supply enters a
low duty-cycle, safe hiccup mode as shown by Figure 11.
Figure 12 that zooms Figure 11 shows that the circuit
operates over about 130 ms on a 3 s hiccup period (4%
duty-cycle).
The application embeds a circuitry (see Figure 13) to
detect overload conditions. A buffer (Q1x) builds a low
impedance signal that is linearly dependent of the feedback
pin of the forward controller. The OVL circuitry monitors
this voltage and if it exceeds 3 V, the npn transistor Q3 turns
on and disables the discrete regulator that powers the two
controllers.
http://onsemi.com
11
AND8292
AC Line Current (2 A/div)
VBULK (100 V/div)
VIN (100 V/div)
Figure 11. The Circuit Enters a Safe Low Duty-Cycle Hiccup Mode if the 19 V Output is Short Circuited
(Test Made at 120 VRMS)
http://onsemi.com
12
AND8292
AC Line Current (2 A/div)
VBULK (100 V/div)
VIN (100 V/div)
Figure 12. Zoom of the Precedent Plot
More generally, this protection triggers when the load current (IOUT) is excessive. The following thresholds were measured:
Table 2.
VIN, RMS
(V)
90
110
180
230
265
IOUT
(A)
10.0
11.3
11.2
11.2
11.2
D15
1N4934
2
R44
2.2
Vaux2
1
C28
100mF / 50V
R31
10 k
Vz
Auxiliary voltage from the forward
transformer
Q7
BC368
D9
16V
D8
1N4148
Vcc
3
When Q3 is on, VZ goes low and VCC
cannot be generated any more. The
application enters hiccup mode.
Q1x
BC846B
FB
5
R1x
43k
D16
3V0
Q3
BC368
4
R26
1k
C9
1mF
Figure 13. Circuit for Overload Protection
http://onsemi.com
13
(NCP1217A
Feedback Voltage)
AND8292
Protection of the PFC Stages
The NCP1605 protection features allow the design of very
rugged PFC stages:
• The following brownout detection levels were
measured (the 19 V output being loaded by a 5 A
current):
- Minimum line RMS voltage to start operation:
83 V.
- RMS line voltage being which the system stops
operation: 74 V.
• As shown by Figure 14, the line current is limited to
3.2 A. This corresponds to proper expected level with
ROCP = 2.4 kW:
•
ǒILINE,MAXǓ + R OCP @ IREF + 2.4k @ 250mA + 3A
2 @ R SENSE
2 @ 0.1
• Pin 14 monitors a portion of the output voltage and
•
stops the circuit switching as long as the pin14 voltage
exceeds 2.5 V. This overvoltage protection (OVP)
guarantees that the bulk voltage cannot exceed the set
OVP level (about 410 V here).
The undervoltage that is also attached to pin 14, detects
if the OVP pin is accidentally grounded or if one of the
upper resistors is not correctly connected and prevents
the circuit operation in case of such a fault. Ultimately,
this protection avoids the power supply destruction if
there is a failure in the OVP sensing network.
Shut-down: if more than 2.5 V are applied to pin 13,
the circuit latches off and cannot recover operation until
the SMPS is unplugged (to enable the NCP1605 VCC
voltage to drop below its 4 V reset voltage). This
latchoff capability is supposed to trigger in case of a
major fault like any overheating of the SMPS. In this
application, it is used to disable the power supply in
case of a severe runaway of the VCC voltage. This is
simply made by applying the VCC voltage through a
16 V zener diode (D3) so that if (VCC-16 V) exceeds
2.5 V, the circuit latches off (see Figure 2). R11 adjusts
the biasing current through D3 and together with R42
and C5, this resistor avoids that the protection falsely
triggers due to some noise. R42 is chosen small
compared to R11 not to modify the threshold since the
actual voltage applied to pin 13 is:
R11
@ (V CC * V D3),
R11 ) R42
which is closed to
(V CC * 16V)
if R42 is small compared to R11 and if D3 is properly
biased.
AC Line Current (2 A/div)
VBULK (100 V/div)
VIN (100 V/div)
Figure 14. Action of the Overcurrent Limitation
(This Test was Made by Creating an Overload Condition at 90 Vrms).
http://onsemi.com
14
AND8292
Dynamic Performance
The following plots were obtained by varying IOUT from
2 A to 8 A (slope 2 A/ms) at 120 Vrms.
One can note that thanks to the NCP1605 dynamic
response enhancer, the bulk voltage stays largely above
350 V while the load current suddenly increases from 25%
to full load (see Figure 16).
IOUT (2 A/div)
8A
VBULK (100 V/div)
2A
350 V
19 V (AC Component - 1 V/div)
VIN (100 V/div)
Figure 15. Abrupt Load Increase at 120 Vrms
to a level that is low enough, the PFC stage skips cycles until
the bulk voltage reaches 95.5% of its nominal value. This
skipping period (see the VBULK decay period from 381 V
down to 360 V in Figure 11) avoids any overshoot and helps
provide the 2-switch forward with a narrow input voltage.
Another interesting behavior is the absence of overshoot
on VBULK when the load current suddenly drops. The PFC
stage takes benefit from the fast response of the 2-switch
forward feedback voltage (FB). More specifically, an abrupt
load decrease results in a rapid drop of the FB voltage. If this
signal that controls the NCP1605 skip mode activity drops
http://onsemi.com
15
AND8292
IOUT (2 A/div)
2A
VBULK (100 V/div)
360 V
19 V (AC Component - 1 V/div)
VIN (100 V/div)
Figure 16. Abrupt Load Decrease at 120 Vrms
Standby Performance
In light load conditions, the circuit enters skip mode to
reduce the losses (the PFC stage remaining on in stand-by
to keep on providing the 2-switch forward with its nominal
input voltage).
Table 3.
Vac
(V)
90
110
PIN, AVG
(No Load)
(mW)
425
450
*These values were obtained by measuring Wh during 2 mn with a power meter YOKOGAWA WT210 at IOUT = 0.
The following figures show the VBULK voltage in standby
mode at low and high line. We can see that as explained in
the data sheet, the NCP1605 skips operation until VBULK
reaches 95.5% of its nominal level and then recovers
operation. Practically, VBULK oscillates between about 380
and 360 V.
One can note that among the measured losses, about
80 mW are due to the two VBULK sensing networks (one for
feedback, another one for OVP). We could then improve
these results if only one sensing network was used and/or if
the leakage current of these sensing networks was lowered
by using higher impedance resistors dividers.
The PFC stage enters skip mode when the load current
drops below 0.5 A.
http://onsemi.com
16
AND8292
IOUT (5 A/div)
VBULK (100 V/div)
19 V (5 V/div)
VIN (100 V/div)
Figure 17. Skip Mode Operation of the PFC Stage at 120 Vrms, No Load.
The Skip Mode Period is About 1.5 s.
IOUT (5 A/div)
382 V
VBULK (100 V/div)
19 V (5 V/div)
VIN (100 V/div)
Figure 18. Zoom of the Precedent Plot
http://onsemi.com
17
360 V
AND8292
IOUT (5 A/div)
VBULK (100 V/div)
19 V (5 V/div)
VIN (100 V/div)
Figure 19. Skip Mode Operation of the PFC Stage at 230 Vrms, No Load
IOUT (5 A/div)
VBULK (100 V/div)
382 V
360 V
19 V (5 V/div)
VIN (100 V/div)
Figure 20. Zoom of the Precedent Plot
http://onsemi.com
18
AND8292
Thermal Measurements
The following results were obtained using a thermal camera, after a 2.5 h operation at 25°C ambient temperature. These data
are indicative.
Table 4.
PFC Stage
Power MOSFET
Bulk Capacitor
Current Sense
Resistor
Coil
Input Bridge
85°C
65°C
85°C
75°C
110°C
Power MOSFETs
Transformer
Output Capacitor
Output Coil
Output Diodes
(MBR20100)
90°C (Low-Side)
85°C (High-Side)
75°C
55°C
100°C
110°C
2-Switch Forward Stage
*Measurement Conditions: Low line (90 Vrms), full load (IOUT = 8 A).
BILL OF MATERIALS
CM1
CM CHOKE
B82734-R2322-B30
EPCOS
CM2
DM CHOKE
WI-FI series - 150 mH
Wurth Electronik
C1, C11, C15
330 nF X2 Capacitor
PHE840MY6330M
RIFA
C2
Bulk Cap. 100 mF / 450 V
222,215,937,101
BC Components
C3
CMS Cap
4.7 nF
various
C4
CMS Cap
390 pF
various
C8, C17
CMS Cap
220 nF
various
C6, C31
Electrolytic Capacitor
220 mF / 25 V
various
C14, C33, C34, C35, C30, C37
CMS Cap
1 nF
various
C27
Through Hole
470 pF / 100 V
various
C21, C25, C12, C13
2.2 nF Y2 Capacitor
DE2E3KH222MA3B
muRata
C18, C29
Electrolytic Capacitor
UPM1E471MPD
Nichicon
C19, C20, C26
CMS Cap
1 mF
various
C22
CMS Cap
680 nF
various
C5, C23
CMS Cap
10 nF
various
C28
Electrolytic Capacitor
100 mF / 50 V
various
C32
Through Hole
100 nF
various
C39
CMS Cap
100 nF
various
D1
PFC Diode
MUR460RLG
ON Semiconductor
D2, D8, D17
DO-35 Diode
1N4148
various
D14
Schottky Diode
1N5817
ON Semiconductor
D3, D9
16 V Zener Diode
1N5930
ON Semiconductor
D18, D20
16 V Zener Diode
1SMA5930BT3G
ON Semiconductor
D16
3V0 Zener Diode
BZX79-C3V0
ON Semiconductor
D6, D7
Dual Schottky Diode
MBR20100CT
ON Semiconductor
D12, D13
Demagnetization Diodes
MUR160RLG
ON Semiconductor
D15
Rectifier
1N4934RLG
ON Semiconductor
HS1_M1, HS3_D6
Heatsink
KL195/25.4SW
Schaffner
HS1_X31, HS2_X24
Heatsink
KL194/25.4SW
Schaffner
L1
DMT2-26-1 1L
26 mH power choke
CoilCraft
M1
PFC MOSFET
SPP20N60S5
Infineon
Q1, Q2
PNP TO92 Transistor
BC369
ON Semiconductor
D19, D21, D11, R45, R56 are replaced by straps (short circuit)
http://onsemi.com
19
AND8292
BILL OF MATERIALS
Q1x
SOT23 NPN Transitor
BC846B
ON Semiconductor
Q5, Q6, Q7
NPN TO92 Transistor
BC368
ON Semiconductor
R1, R3, R4, R9, R14, R16, R20, R22
1%, 1/4 W Resistors
1.8 MW
various
R2
1%, 1/4 W Resistors
150 W
various
R12, R39
1%, 1/4 W Resistors
47 W
various
R6
1%, 1/4 W Resistors
2.4 kW
various
R7
3 W PFC CS Resistor
RLP3 0R1 1%
Vishay
R8
1%, 1/4 W Resistors
4.7 kW
various
R10, R31, R37, R38, R51
1%, 1/4 W Resistors
10 kW
various
R13, R44
1%, 1/4 W Resistors
2.2 W
various
R15
1%, 1/4 W Resistors
62 kW
various
R17, R21
1%, 1/4 W Resistors
27 kW
various
R49
1%, 1/4 W Resistors
6.8 kW
various
R18, R27, R46, R58
1%, 1/4 W Resistors
22 kW
various
R23
1%, 1/4 W Resistors
820 kW
various
R24
1%, 1/4 W Resistors
560 kW
various
R25
3 W 0.27 W Forward CS Resistor
W31-R27 JI
WELWYN
R40, R50, R36
1%, 1/4 W Resistors
10 W
various
R28
1%, 1/4 W Resistors
47 kW
various
R29, R30
1%, 1/4 W Resistors
3.3 kW
various
R35
100 W / 4 W Resistor
SBCHE4
Meggitt CGS
R11, R43, R55, R57
1%, 1/4 W Resistors
1 kW
various
R42
1%, 1/4 W Resistors
100 W
various
R52
1%, 1/4 W Resistors
6.8 kW
various
R1x
1%, 1/4 W Resistors
43 kW
various
T1
PFC Coil
SICO 977
Sicoenergie
T2
Forward Transformer
SICO 978
Sicoenergie
U1
Diodes Bridge
KBU6K
General Semiconductor
U2
Forward Controller
NCP1217AD133R2G
ON Semiconductor
U3
PFC Controller
NCP1605
ON Semiconductor
X25
01:01 Pulse Transformer
Q3903-A
CoilCraft
X29
Opto-Coupler
SFH6156-2
Infineon
X30
TO92 Voltage Reference
TL431CLPG
ON Semiconductor
X24, X31
Forward MOSFET
SPP11N60S5
Infineon
F1
4 A Fuse
various
various
D19, D21, D11, R45, R56 are replaced by straps (short circuit)
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). 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:
Literature Distribution Center for ON Semiconductor
P.O. Box 5163, Denver, Colorado 80217 USA
Phone: 303-675-2175 or 800-344-3860 Toll Free USA/Canada
Fax: 303-675-2176 or 800-344-3867 Toll Free USA/Canada
Email: [email protected]
N. American Technical Support: 800-282-9855 Toll Free
USA/Canada
Europe, Middle East and Africa Technical Support:
Phone: 421 33 790 2910
Japan Customer Focus Center
Phone: 81-3-5773-3850
http://onsemi.com
20
ON Semiconductor Website: www.onsemi.com
Order Literature: http://www.onsemi.com/orderlit
For additional information, please contact your local
Sales Representative
AND8292/D