®
Design Idea DI-30
®
TOPSwitch-GX
180 W PC Main SFX Supply
Application Device Power Output Input Voltage Output Voltage Topology
PC Main 180 W 90-130 VAC / 180-265 VAC 3.3 V / 5 V / 12 V / -12 V Forward
TOP249Y
C3) balancing circuit, operating only as needed to minimize
Design Highlights
zero-load power consumption.
" 180 W cont. (200 W peak) in PC SFX form factor
" Includes passive power factor correction (PFC) Resistors R3, R5 and R6 implement start-up undervoltage
" TOPSwitch-GX integrated features enable extremely low lockout, which prevents the supply from starting below
component count 180 VDC. Components R4, R14, Q1 and R30 implement an
" Meets 1 W standby spec (0.91 W input, 0.5 W output) independent undervoltage using the X pin, which allows the
" High efficiency (71% minimum) supply to continue delivering power all the way down to
" Integrated line undervoltage and overvoltage detection 140 VDC (increasing holdup time). Resistor R7 provides
" Low EMI due to frequency jitter additional hysteresis.
" SOURCE referenced TO-220 tab lowers conducted EMI
" Maximum duty cycle reduction (DCMAX) prevents transformer The primary side components D1, VR3-5 and C4, along with
saturation for fault and transient loads secondary side C9 and R30, implement the Zener/capacitor
" Uses conventional magamp for 3.3 V output reset/clamp circuit. This circuit provides reset voltage for the
" Meets CISPR22B/EN55022B conducted EMI transformer and clamps the DRAIN pin voltage to a safe level
(<~600 V) under all conditions.
Operation
The reset circuit works in conjunction with the DCMAX
TOPSwitch-GX integrates many features designed for use with
reduction circuit (R8, R36, C22, VR19 and D18) to limit the
forward converters. Passive power factor correction (PFC) is
maximum duty cycle and prevent transformer saturation
implemented using inductors LPFC1 and LPFC2. Transistors
under fault and transient conditions.
Q4, Q6, R1, R2, R3, R5, and R6 form an active capacitor (C2,
C10
1 nF
Coupled
50 V
choke
L1
13 µH
5 4
+12 V
2 14
C11
C4 7, 8 1, 2
D7
R3
R1 1000 µF
2.2 nF
MBR3045
2.2 M&! C9
330 k&! 16 V L2
1 kV
R4 47 nF
0.5 µH
13 50 V
2.2 M&! 6 3
+5 V
R5
D1 R30
180 k&!
1N5407
BR1 1 &!
Q4
1
KBL06 1 W
C13
C2 MPSA42
220 µF
470 µF C12
R21
8, 9, 10
63 V
200 V D8 2200 µF
270 &!
LPFC1
CY3
MBR6045 6.3 V
C20
R6 TO
2.2 nF
330 pF
2.2 M&! MAGAMP OUT
(Safety)
50 V
(3.3 V)
LPFC2 11,12
RTN
CY4 C24
JP9 TOPSwitch-GX C27
2.2 nF 3 D6
330 µF
330 pF
U1 R13
C5
(Safety) BAV20 C25
25 V
50 V
TOP249 10 &!
1 µF R18 1 µF
CX1 D18
100 V R11
Q6 4.74 k&! 50 V
R8 R36
0.047 µF 4 BAV20
330 &!
MPSA92 1%
LM
130 k&! 43.2 k&!
250 VAC - 12 V
R15 320
To AC Selector 1% 1%
D20
1.8 k&!
L7 Switch
UF4002
R7 VR19
8.2 mH
D L C22
VR3 560 k&! 1N5229
C17
R20
CX2 100 pF
BZY97C-
100 nF
CONTROL
270 k&!
0.33 µF 50 V
C3 200
50 V
C
250V
470 µF
R16
VR4 U2
200 V
R11
1 k&!
R10 BZY97C- SFH615A-2
300 &!
RT1
560 K 180 S X F C8 C16
R9
10 &!
0.033 µF 100 nF R17
1/2 W 47 &! Q1
VR5 50 V 50 V 15 k&!
2N3908
RV1 BZY97C-
R2
D105
275 V, 14 mm 180
330 k&! R30
C6 1N4148
R14 U5
3.3 k&!
47 µF R19
75 k&! TL431
16 V 4.12 k&!
1%
PI-3384-120902
+12 V STBY
R12
R106
R38
12 k&!
27 k&!
5.1 k&!
Remote
U3
LTV817 ON/OFF
F1 C7
Q7
4 A 100 nF
2N3904
C23
50 V R37
33 nF
10 k&!
50 V
L G N
Figure 1. 180 W (200 W pk.) PC Main Power Supply Schematic (Note: Schematic does not include transformer Y-capacitor).
DI-30 December 2002
www.powerint.com
DI-30
The components R12, C7, R38, Q7, C23, R37, U3, R106 and clamp/reset circuit to maintain drain voltage < 600 V and
D105 implement the remote ON/OFF drive circuit. During DCMAX reduction to prevent transformer saturation.
the ON state, U3 and hence Q7 conduct, pulling the X pin to " Maintain maximum flux density on transformer (T1)
SOURCE via resistor R12 (which sets the current limit). < 2500 gauss.
" Check for balanced currents on coupled inductor (L1) for
During the OFF state, U3 and Q7 are off, allowing the X pin all load combinations.
to be pulled high by the +15 V standby supply via R38 and R12 " Use PI Expert (PIXls) Design Spreadsheet and refer to
and putting the TOPSwitch-GX into the OFF state. Components Application Note AN-30 for details on designing forward
R38 and D105 reduce device consumption to around 2mW by converters with TOPSwitch-GX.
supplying external current to the CONTROL pin from the
+15 V standby supply. Resistor R11 is required to allow This particular PC SFX 12 specification delivers a larger
external bias feed. proportion of power on the 12 V winding; efficiency would be
lower if that power were drawn from the 3.3 V output.
Key Design Points
Due to the complexity of this design it is not possible to include
" The passive PFC inductors (LPFC1 and LPFC2) are
all details in this Design Idea. An Engineering Prototype Report
constrained by both thermal and efficiency requirements.
(EPR) will be available for this design Dec. 2000. For updates
Design of these inductors is not covered in this Design Idea.
and all other information please refer to Power Integrations'
" Transformer reset: Use recommended Zener/capacitor
Web site.
D9
L4 L5
MBR2045
20 µH 0.5 µH
FROM MAIN
3.3 V
CONVERTER
L3
R22
5 V WINDING
Mag Amp
3 &!
R23 R25 R24
6 Turns
1 k&! 2.7 k&! 3.84 k&!
Q2
1%
C14 C15
TIP32
1200 µF 1200 µF
R27
C18
R34
10 V 10 V
390 &!
0.1 µF
33 &!
50 V
D11
C21
UF4002
D10 R26
1 µF U8
UF4002 10 k&!
50 V TL431
1%
RTN RTN
PI-3385-093002
Figure 2. Magamp for Independent 3.3 V Secondary Regulation.
For the latest updates, visit our Web site: www.powerint.com
Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability.
Power Integrations does not assume any liability arising from the use of any device or circuit described herein, nor does it convey any
license under its patent rights or the rights of others. The products and applications illustrated herein (including circuits external to the
products and transformer construction) may be covered by one or more U.S. and foreign patents or potentially by pending U.S. and foreign
patent applications assigned to Power Integrations. A complete list of Power Integrations patents may be found at www.powerint.com.
The PI Logo, TOPSwitch, TinySwitch, LinkSwitch and EcoSmart are registered trademarks of Power Integrations, Inc.
PI Expert is a trademark of Power Integrations, Inc. ©Copyright 2002, Power Integrations, Inc.
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