Application

Device

Power Output

Input Voltage

Output Voltage

Topology

DVD

TOP245P

20 W (25 W pk)

85-265 VAC

3.3 V / 5 V / 12 V / -24 V

Flyback

www.powerint.com

Design Idea DI-55

TOPSwitch-GX

20 W (25 W peak) DVD Supply

July 2006

DI-55

Figure 1. 20 W Multiple Output DVD Supply.

®

Design Highlights

• Simple, low cost, low part count solution

• No heatsinks required

• Low EMI-frequency jitter allows EN55022B/FCC B

compliance with simple EMI filter

• High efficiency, >75% at 90 VAC

• Low zero load power consumption, <100 mW at

230 VAC

• Low standby power consumption, <1 W input at 0.5 W

output, 230 VAC

• Excellent cross-regulation

• Differential and common mode surge immunity to 3 kV

(EN 61000-4-5)

Operation

The TOP245P selected for the design in Figure 1 is ideal for

DVD and set-top box applications. The P package removes the

need for a heatsink while still delivering 20 W/25 W peak at

an ambient temperature of 50 °C.

TheexternalcurrentlimitprogrammingandremoteON/OFF

(inhibit) functions of the M pin allow current mode control

and reduced switching frequency at light and no-load condi-

tions. Current mode control is implemented by R2, Q3, R3,

C16, R4 and R6.

Feedback current above ~2 mA(U1 supply current) forward

biases Q3 and pulls up R6. This adjusts the sink current out

of the M pin, thereby allowing the output voltage feedback

loop to control the primary switch current.

Resistor R6 sets the maximum current limit, while R2 and

C16 provide slope compensation. The value of R4 is chosen

to ensure that current does not flow into the M pin, enabling

the line sensing features of the pin. The current out of the

M pin falls as the load is reduced until the M pin inhibit

threshold is reached. The supply then operates with a fixed

25% current limit, lowering the switching frequency to

maintain regulation. This greatly reduces switching losses,

maintaining high standby efficiency and low no-load power

consumption.

PI-3648-071106

RV1

275 VAC

C3

0.047

µF

X2

C1

33

µF

400 V

C8

2.2 nFY1

T1

EE25L

VR1

P6KE

130

C4

33

µF

400 V

D6

1N4148

D5

1N4007GP

R7

1 k

Ω

R1

68

Ω

L1

5 mH

CM Choke

1N4007 x 4

F1

3.15 A

250 VAC

RT1

t

°

+12 V, 500mA

OPTIONAL

+5 V, 2.5 A

J2-3

+3.3 V, 2 A

J2-6

RET

J2-2, 4, 5, 7

-24 V, 50 mA

J2-1

J1-2

LINE

J1-1

NTRL

U1

TOP245P

TOPSwitch-GX

D

S

C

CONTROL

M

Q3

1N3906

C13

47

µF

25 V

C5

47

µF

25 V

C14

0.1

µF

C9

150

µF

35 V

C6

150

µF

35 V

C12

1200

µF

10 V

C15

470

µF

25 V

C20

180

µF

25 V

L2

3.3

µH

L5

BEAD

L3

3.3

µH

L4

3.3

µH

C12

1200

µF

10 V

R17

200

Ω

D7

1N5819

1

4

8

12

13

9

10,11

14

7

5

D11

SB540CT

D10

SB540CT

R12

6.34 k

Ω

1%

R11

20.0 k

Ω

1%

C17

470

µF

10 V

D8

1N4005

Q1

2SA0885

D9

1N4005

R14

1.13 k

Ω

1%

R16

2.0 k

Ω

1%

R15

2.4 k

Ω

R13

2 k

Ω

1%

C18

470

µF

10 V

R8

1

Ω

1/2 W

D12

UF4003

R10

10 k

Ω

U3

TL431

U2

R9

10.0 k

Ω

1%

LTV817A

R4

10 k

Ω

R2

18 k

Ω

R3

270

Ω

C16

0.1

µF

C2

0.01

µF

1 kV

R6

5.1 k

Ω

Q4

2N3904

Q5

2N3906