DI-23 Datasheet, PDF (1/2 Pages) Power Integrations, Inc. – 10 W, Multi-output, High Speed Modem Power Supply

Design Idea DI-23
TOPSwitch^®-GX 10 W, Multi-output,
High Speed Modem Power Supply
Application
Device
High Speed Modem TOP243P
Power Output
10 W
Input Voltage
85-264 VAC
Output Voltage
3.3 V / 5 V / 30 V
Topology
Flyback
Design Highlights
• Compact low cost design (113 mm × 39 mm × 25 mm) with
only 46 parts
• Meets Blue Angel no-load power consumption
• Line undervoltage protection prevents turn-off output
glitches and overvoltage protection provides extended line
surge protection
• Hysteretic thermal shutdown provides automatic fault
recovery
• Frequency jittering dramatically reduces EMI and meets
EN550022 Class B without Y1 capacitor
• Ultra low leakage current (<1 µA at 265 VAC) eliminates
audio hum in voice applications
• Surge immunity to 4 kV (EN61000-4-5)
• High efficiency >70%
Typical applications are wall mount adapters, set-top box, high-
speed modem, standby power supplies, and other applications
requiring very low cost, small size, and low
no-load input power consumption.
The example discussed here passes EMI conducted and radiated
emissions tests without using a Y1 capacitor between primary
and secondary. This is possible with the frequency jittering
feature of TOPSwitch-GX and careful transformer construction.
Shield windings are used in the transformer to reduce common
mode EMI currents. Transformer specifications are given in
Table 1.
Good cross-regulation of output voltages is achieved by careful
transformer construction and using a TL431 voltage regulator
instead of a Zener regulator.
Operation
TOP243P (DIP package) is shown in Figure 1. The power
supply utilizes many TOPSwitch-GX features such as frequency
jittering, input voltage sense, thermal shutdown, internal current
limit, soft-start, etc. without adding any extra components.
The power supply uses a low cost RCD clamp with a slow
1N4007GP diode, which reduces EMI emissions and recycles
leakage energy, increasing efficiency. Input line sensing prevents
reverse conduction of current in TOPSwitch-GX at very low
input voltages due to the 1N4007GP in the RCD clamp.
D1-D4
1N4007
1 A, 1000 V
C2
1 nF
1 kV
R1
150 kΩ
0.5 W
R6
100 Ω
L1
20 mH
0.8 A
C15
0.1 µF
250 VAC
X2
C1
33 µF
400V
D5
1N4007GP
D
F1
3.15 A
U1
TOP243P
S
L
85 - 265
VAC
N
1
10
9
D7
UF4003
D8
SB360
2
R8
D9
10 Ω SB540
6
C13
2.2 nF
7
4
D6
1N4148
5
T1
EE25
R2
2 MΩ
M ^TOPSwitch-GX
CONTROL
C
R4
6.8 Ω
C3
47 µF
10 V
R5
10 Ω
C4
47 µF
50 V
C5
820 µF
16 V
C6
820 µF
16 V
C7
820 µF
16 V
C11
0.1 µF
U2
LTV817A
C14
1 µF
50 V
L4
10 µH
L2
3.3 µH
C10
10 µF
50 V
L3
3.3 µH
C8
100 µF
10 V
R13
12 kΩ
C9
150 µF
6.3 V
R6
75 Ω
0.03 A, 30 V
0.9 A, 5 V
1.5 A, 3.3 V
RTN
R7
1 kΩ
R10
15.4 kΩ
1%
C10
0.1 µF
R11
10 kΩ
1%
U3
LM431BCZ
1%
R12
10 kΩ
1%
PI-3366-120704
Figure 1. TOP243P – 10 W, 3.3 V at 1.5 A, 5 V at 0.9 A, 30 V at 0.03 A, High Speed Modem Power Supply.
DI-23
www.powerint.com
December 2004