www.powerint.com

November 2002

DI-39

Figure 1. TOPSwitch-GX DVD Player Schematic.

.

®

Application

DVD

TOP244P

3.3 V / 5 V / 12 V / -12 V

Power Output

13 W (17 W pk)

Input Voltage

Output Voltage

Topology

Device

85-265 VAC

Flyback

Design Highlights

• High efficiency multi-ouptut flyback (77% minimum)

• Topology scalable to higher powers

• Excellent cross-regulation

• Excellent input no-load consumption <70 mW input

• 132 kHz switching frequency allows smaller transformer

• Frequency jitter eliminates common-mode EMI choke

• >10 dB margin against CISPR22-B conducted EMI with

artificial hand grounding

Operation

The TOPSwitch-GX uses current mode feedback to achieve

excellent no-load standby. Components C16, R1 and Q2 provide

a constant current powering the TOPSwitch-GX CONTROL

pin. Resistor R2 feeds the remainder of Q2 current to the M pin,

reducing TOPSwitch-GX current limit with increased current.

Resistor R11 sets the maximum current limit of the device.

Components R6, Q1 and C13 implement slope compensation.

®

Design Idea DI-39

Input DVD Supply with 70 mW No-load

The supply operates at full frequency at high and medium

power and reduces frequency at light loads. Components D9

and C10 rectify and filter the bias voltage.

TOPSwitch-GX frequency jitter allows conducted EMI

compliance without a common-mode choke, using only

capacitors C1, C4 and inductor L1 as an EMI filter.

Components D5 and C2 form a capacitor clamp circuit

absorbing leakage inductance energy during normal operation.

Zener VR1 clamps the voltage to a safe level during abnormal

and transient conditions. After clamping, reverse current

flows through D5, recovering some of the energy. Resistor

R5 limits the reverse current and, with R7, improves EMI by

limiting the ringing on the drain. Continuous mode operation

allows reduced primary and secondary peak currents,

optimizing cross regulation and load regulation by

minimizing leakage inductance induced voltage shifts.

Resistors R15 and R16 share the feedback from the 3.3 V

and 5 V outputs for good cross-regulation.

PI-3321-111902

C3

0.047 µF

x2

F1

3.15 A

250 VAC

C1

33 µF

400V

L1

1.4 µH

0.5 A

C4

33 µF

400V

VR1

P6KE180

R5

47 Ω

D5

1N4007

R7

100 Ω

D

S

C

CONTROL

M

D7

UF4003

D11

1N5822

D8

UF4003

C8

1 nF

Y1

C9

220 µF

25 V

C12

1000 µF

10 V

C11

1800 µF

25 V

C15

470 µF

25 V

L2

3.3 µH

L3

3.3 µH

L4

3.3 µH

R12

1 1/2 W

C6

220 µF

25 V

R9

200 Ω

C7

10 µF

50 V

R8

1 kΩ

U3

TL431CLP

C14

0.1 µF

R10

3.3 kΩ

R13

10 kΩ

R16

6.34 kΩ

R15

20 kΩ

C20

150 µF

25 V

C17

470 µF

10 V

C18

470 µF

10 V

12 V, 400 mA

5 V, 1.6 A

3.3 V, 700 mA

RTN

85 - 265

VAC

R11

7.5 kΩ

R2

20 kΩ

C16

0.33 µF

R1

270 Ω

R6

20 kΩ

Q1

2N3906

Q2

2N3906

D9

1N4148

C10

47 µF

50 V

C13

47 pF

U1

TOP244P

C19

0.1 µF

R14

6.8 Ω

C5

47 µF

10 V

- 12 V, 100 mA

U2B

PC817

PC817

U2A

D10

1N5822

TOPSwitch-GX

D1-D4

1N4005

C2

0.01 µF

1 KV