Design Idea DI-43
®
TOPSwitch-GX
30 W, Universal Input,
12 V Supply with <250 mW No-load
Application
Adapter
Device
TOP244Y
Power Output
30 W
Input Voltage
85-265 VAC
Output Voltage
12 V
Flyback
®
Topology
Design Highlights
• High efficiency (79% minimum)
• Low component count
• Excellent input no-load consumption <200 mW at 115 VAC
and <250 mW at 230 VAC input
• Rugged supply includes UV/OV shutdown, thermal and
short circuit protection with auto-recovery
• Comfortably meets EN55022B and CISPR22B conducted
EMI standards
• Overload power delivery at 265 VAC limited to 160% of
rated load
limiting the maximum overload power of the supply. The
reduced current limit allows continuous conduction mode
operation with a small transformer, reducing primary and
secondary peak currents, optimizing efficiency, and reducing
component stress.
Diode D1 and VR1 form a clamp circuit that absorbs leakage
inductance energy during normal operation, with Zener VR1
clamping the voltage to a safe level. Capacitor C2 diverts
some of the leakage energy from VR1, reducing its temperature
and increasing overall efficiency. After clamping, reverse
current flows through D1, recovering some of the clamp
energy. R3 limits the reverse current in D1 and improves
EMI by limiting drain voltage ringing.
Resistors R9 and R10 set the output voltage. Components
C10 and R8 provide compensation with R6 setting DC loop
gain. Using a TL431 error amplifier gives better regulation
and output voltage tolerance than a Zener reference and also
provides better no-load performance due to lower (1 mA)
bias current.
C12
R11
470 pF 33
Ω
100 V 1/4 W
D3
MBR10100
6,7
C6
680
µF
35 V
9,10
D2
1N4148
C7
680
µF
35 V
C8
100
µF
35 V
RTN
L2
3.3
µH
Operation
The
TOPSwitch-GX
integrates many features to implement low
cost, switched mode power supplies.
A single resistor (R1) implements input UV/OV protection
using the L pin (UV typ. 100 VDC; OV typ. 450 VDC). Resistor
R4 programs the U1 current limit to 85% of nominal, and
resistor R2 reduces this current limit as input voltage increases,
C7
2.2 nF
Y1
T1
C2
4.7 nF
1 kV
R3
47
Ω
1/2 W
D1
UF4005
L1
22 mH
C1
100
µF
400 V
CX1
220 nF
250 VAC
F1
3.15 A
L
R2
8.2 MΩ
1/2 W
D
12 V, 2.5 A
1
VR1
P6KE
200
BR1
2 A, 600 V
3
R1
2 MΩ
1/2 W
L
CONTROL
C
5
C3
1
µF
50 V
U2
ISP817C
D4
1N4148
C11
10
µF
35 V
R6
1 kΩ
R7
15 kΩ
R9
38.3 kΩ
1%
R8
4.7 kΩ
4
TOPSwitch-GX
U1
TOP244Y
S
X
F
85-265 VAC
N
R4
8.25 kΩ
1%
C4
100 nF
R5
6.8
Ω
C5
47
µF
10 V
C10
47 nF
U3
TL431
R10
10 kΩ
1%
Figure 1. TOPSwitch-GX 12 V, 30 W Universal Power Supply.
DI-43
PI-3405-112702
www.powerint.com
November 2002
DI-43
Optional components D4, C11, and R7 implement soft finish
to limit startup overshoot. Resistor R7 discharges this soft-
finish capacitor at power down.
TRANSFORMER PARAMETERS
Core Material
EF25 Nippon Ceramic NC-2H
A
LG
of 264 nH/T
2
EF25 10 pin
(Miles Platts FE0100 with TBS-601)
Primary: 58T x 26 AWG
Bias: 2T x 26 AWG
12 V: 6T 4 x 25 AWG T.I.W.
(T.I.W. = Triple Insulated Wire)
1/2 Primary, tape, 1/2 primary (1-3),
tape, Bias (5-4), tape,
12 V (9-10, 6-7), tape
Primary: 876
µH ±
10% at 132 kHz,
Leakage: 28
µH
(maximum)
570 kHz (minimum)
Key Design Points
• Use reflected voltage from 90 V to 120 V
• Compact layout for components D3, C6 and C7 will
improve efficiency. Make sure the both capacitors C6 and
C7 have equal secondary loop areas to balance the ripple
currents in each.
• Clamp: for lowest cost use an RCD clamp replacing Zener
VR1 with a power resistor. For best no-load performance,
use the Zener clamp as shown.
• Reference voltage: Use low current Zener secondary
reference with 5 mA bias current for lowest cost. Use
TL431 as shown for both better regulation accuracy and
no-load consumption (due to lower bias current 1 mA).
Bobbin
Winding Details
Winding Order
(Pin Numbers)
Inductance
Primary Resonant Frequency
Table 1. Transformer Construction Information.
PI-3422-112602
.35
.30
Input Power (W)
.25
.20
.15
.10
.05
0
80
120
160
200
240
280
AC Input Voltage
Figure 2. P
IN
vs V
IN
Curve.
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
A
11/02
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
www.powerint.com
京公网安备 11010802033920号
EEWORLD
