Design Idea DI-30
®
TOPSwitch-GX
180 W PC Main SFX Supply
Application
PC Main
Device
TOP249Y
Power Output
180 W
Input Voltage
Output Voltage
Topology
Forward
90-130 VAC / 180-265 VAC 3.3 V / 5 V / 12 V / -12 V
®
Design Highlights
• 180 W cont. (200 W peak) in PC SFX form factor
• Includes passive power factor correction (PFC)
•
TOPSwitch-GX
integrated features enable extremely low
component count
• Meets 1 W standby spec (0.91 W input, 0.5 W output)
• High efficiency (71% minimum)
• Integrated line undervoltage and overvoltage detection
• Low EMI due to frequency jitter
• SOURCE referenced TO-220 tab lowers conducted EMI
• Maximum duty cycle reduction (DC
MAX
) prevents transformer
saturation for fault and transient loads
• Uses conventional magamp for 3.3 V output
• Meets CISPR22B/EN55022B conducted EMI
C3) balancing circuit, operating only as needed to minimize
zero-load power consumption.
Resistors R3, R5 and R6 implement start-up undervoltage
lockout, which prevents the supply from starting below
180 VDC. Components R4, R14, Q1 and R30 implement an
independent undervoltage using the X pin, which allows the
supply to continue delivering power all the way down to
140 VDC (increasing holdup time). Resistor R7 provides
additional hysteresis.
The primary side components D1, VR3-5 and C4, along with
secondary side C9 and R30, implement the Zener/capacitor
reset/clamp circuit. This circuit provides reset voltage for the
transformer and clamps the DRAIN pin voltage to a safe level
(<~600 V) under all conditions.
The reset circuit works in conjunction with the DC
MAX
reduction circuit (R8, R36, C22, VR19 and D18) to limit the
maximum duty cycle and prevent transformer saturation
under fault and transient conditions.
C10
1 nF
50 V
5
R1
330 kΩ
C4
2.2 nF
1 kV
D1
1N5407
2
R3
2.2 MΩ
R4
2.2 MΩ
R5
180 kΩ
1
14
D7
MBR3045
13
R30
1
Ω
1W
8, 9, 10
R6
2.2 MΩ
C20
330 pF
50 V
11,12
3
R13
10
Ω
D8
MBR6045
C12
2200
µF
6.3 V
R21
270
Ω
C9
47 nF
50 V
7, 8
Coupled
choke
L1
13
µH
Operation
TOPSwitch-GX
integrates many features designed for use with
forward converters. Passive power factor correction (PFC) is
implemented using inductors LPFC1 and LPFC2. Transistors
Q4, Q6, R1, R2, R3, R5, and R6 form an active capacitor (C2,
4
1, 2
C11
1000
µF
16 V
L2
0.5
µH
+12 V
6
3
+5 V
C13
220
µF
63 V
TO
MAGAMP OUT
(3.3 V)
RTN
C25
1
µF
50 V
LM
320
- 12 V
BR1
KBL06
CY3
2.2 nF
(Safety)
JP9
CX1
0.047
µF
250 VAC
L7
8.2 mH
CX2
0.33
µF
250V
RT1
10
Ω
R10
560 K
1/2 W
LPFC1
C2
470
µF
200 V
Q4
MPSA42
LPFC2
CY4
2.2 nF
(Safety)
Q6
MPSA92
To AC Selector
Switch
VR3
BZY97C-
200
VR4
BZY97C-
180
VR5
BZY97C-
R2
180
330 kΩ
D
L
CONTROL
C
TOPSwitch-GX
U1
TOP249
R8
130 kΩ
1%
R36
43.2 kΩ
1%
C22
100 pF
50 V
R7
560 kΩ
D6
BAV20
D18
BAV20
4
C5
1
µF
100 V
C27
330 pF
50 V
R11
330
Ω
D20
UF4002
C24
330
µF
25 V
R18
4.74 kΩ
1%
R15
1.8 kΩ
C17
100 nF
50 V
R16
1 kΩ
C16
100 nF
R17
50 V
15 kΩ
VR19
1N5229
C3
470
µF
200 V
R20
270 kΩ
S
X
F
C8
0.033
µF
50 V
R9
47
Ω
C6
47
µF
16 V
R11
300
Ω
Q1
2N3908
R14
75 kΩ
D105
1N4148
U2
SFH615A-2
RV1
275 V, 14 mm
R30
3.3 kΩ
U5
TL431
R19
4.12 kΩ
1%
PI-3384-120902
R12
12 kΩ
+12 V STBY
R38
5.1 kΩ
U3
LTV817
R106
27 kΩ
Remote
ON/OFF
R37
10 kΩ
F1
4A
L
G
N
C7
100 nF
50 V
Q7
2N3904
C23
33 nF
50 V
Figure 1.
180 W (200 W pk.) PC Main Power Supply Schematic (Note: Schematic does not include transformer Y-capacitor)
.
DI-30
www.powerint.com
December 2002
DI-30
The components R12, C7, R38, Q7, C23, R37, U3, R106 and
D105 implement the remote ON/OFF drive circuit. During
the ON state, U3 and hence Q7 conduct, pulling the X pin to
SOURCE via resistor R12 (which sets the current limit).
During the OFF state, U3 and Q7 are off, allowing the X pin
to be pulled high by the +15 V standby supply via R38 and R12
and putting the
TOPSwitch-GX
into the OFF state. Components
R38 and D105 reduce device consumption to around 2mW by
supplying external current to the CONTROL pin from the
+15 V standby supply. Resistor R11 is required to allow
external bias feed.
clamp/reset circuit to maintain drain voltage < 600 V and
DC
MAX
reduction to prevent transformer saturation.
• Maintain maximum flux density on transformer (T1)
< 2500 gauss.
• Check for balanced currents on coupled inductor (L1) for
all load combinations.
• Use
PI Expert
(PIXls) Design Spreadsheet and refer to
Application Note AN-30 for details on designing forward
converters with
TOPSwitch-GX.
This particular PC SFX 12 specification delivers a larger
proportion of power on the 12 V winding; efficiency would be
lower if that power were drawn from the 3.3 V output.
Due to the complexity of this design it is not possible to include
all details in this Design Idea. An Engineering Prototype Report
(EPR) will be available for this design Dec. 2000. For updates
and all other information please refer to Power Integrations'
Web site.
L5
0.5
µH
3.3 V
L3
Mag Amp
6 Turns
Q2
TIP32
R34
33
Ω
D11
UF4002
RTN
D10
UF4002
R22
3
Ω
Key Design Points
• The passive PFC inductors (LPFC1 and LPFC2) are
constrained by both thermal and efficiency requirements.
Design of these inductors is not covered in this Design Idea.
• Transformer reset: Use recommended Zener/capacitor
D9
MBR2045
FROM MAIN
CONVERTER
5 V WINDING
L4
20
µH
R23
1 kΩ
R27
390
Ω
C21
1
µF
50 V
C18
0.1
µF
50 V
U8
TL431
R25
2.7 kΩ
R24
3.84 kΩ
1%
C14
1200
µF
10 V
C15
1200
µF
10 V
R26
10 kΩ
1%
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.
WORLD HEADQUARTERS
AMERICAS
Power Integrations, Inc.
San Jose, CA 95138 USA
Customer Service:
Phone:
+1 408-414-9665
Fax:
+1 408-414-9765
e-mail: usasales@powerint.com
CHINA
Power Integrations International
Holdings, Inc.
China
Phone:
+86-755-8367-5143
Fax:
+86-755-8377-9610
e-mail: chinasales@powerint.com
EUROPE & AFRICA
Power Integrations (Europe) Ltd.
United Kingdom
Phone:
+44-1344-462-300
Fax:
+44-1344-311-732
e-mail: eurosales@powerint.com
KOREA
Power Integrations
International Holdings, Inc.
Seoul, Korea
Phone:
+82-2-782-2840
Fax:
+82-2-782-4427
e-mail: koreasales@powerint.com
SINGAPORE
Power Integrations, Singapore
Republic of Singapore 308900
Phone:
+65-6358-2160
Fax:
+65-6358-2015
e-mail: singaporesales@powerint.com
JAPAN
Power Integrations, K.K.
Keihin-Tatemono 1st Bldg.
Japan
Phone:
+81-45-471-1021
Fax:
+81-45-471-3717
e-mail: japansales@powerint.com
APPLICATIONS HOTLINE
World Wide +1-408-414-9660
TAIWAN
Power Integrations
International Holdings, Inc.
Taipei, Taiwan
Phone:
+886-2-2727-1221
Fax:
+886-2-2727-1223
e-mail: taiwansales@powerint.com
INDIA (Technical Support)
Innovatech
Bangalore, India
Phone:
+91-80-226-6023
Fax:
+91-80-228-9727
e-mail: indiasales@powerint.com
APPLICATIONS FAX
World Wide +1-408-414-9760
B
12/02
www.powerint.com
京公网安备 11010802033920号
EEWORLD
