Design Idea DI-129

33 W (60 W Peak) PVR Power Supply

Figure 1. Circuit Diagram of a 33 W Continuous, 60 W Peak, PVR Power Supply.

DI-129

November 2006

Application

Device

Power Output

Input Voltage

Output Voltage

Topology

PVR

PKS606P

33 W (60 W Pk)

195-265 VAC

3.3 V, 5 V, 17.5 V, 22 V

Flyback

Design Highlights

• Small, low-cost EF25 core size delivers 60 W peak

• Low component count: only 47 parts

• High efficiency: ≥76% at 33 W

• No-load power consumption <140 mW

• Meets EN55022 B conducted EMI limits

Operation

The flyback converter shown in Figure 1 uses a member of

the PeakSwitch family (U6, a PKS606P) to supply 33 W

continuously and peak power pulses of up to 60 W.

The controller in U6 receives feedback from the secondary

through U5, and based on that feedback, enables or disables

theswitchingofitsintegratedMOSFETtomaintainregulation.

A portion of both the 3.3 V and the 5 V outputs are fed into

the TL431 (U2), which controls the current through the LED

in U5. As the 3.3 V or the 5 V output voltages rise above

theirset-pointthresholds,U2pullsadditionalcurrentthrough

the LED in U5. This in turn increases the base drive to

Q1, increasing the current pulled out of the EN/UV pin of

U6. Switching cycles are skipped once the EN/UV disable

threshold current is exceeded. When the current out of the

EN/UV pin falls below the disable threshold, switching

cycles are re-enabled.

A bias winding (T1, pins 4 and 5) on the transformer is

rectified and filtered by D15 and C21, and supplies operating

current to U6, through R14. The frequency jitter function

within U6 and a Y-type capacitor (C10) across T1 reduce the

generation of conducted EMI so that a single common mode

choke (L5) and a small X-capacitor (C13) allow the supply

meet EN55022B limits with 6 dBµV or more of margin. A

combination RCD-Zener clamp (R2, R15 C9, D10 and VR2)

limits the peak drain-node voltage to below the 700 V rating

of the MOSFET integrated within U6.

D8

STPS3150

D9

STPS3150

D2

SB530

D7

SB520

D15

1N4148

VR2

1N4764A

100 V

D10

FR106

D13

1N4148

D16

1N4148

R2

22

Ω

1/2 W

R15

10 k

Ω

1/2 W

R14

4.7 k

Ω

R17

22

Ω

R13

15

Ω

1 W

Q1 2N3904

C21

47

µF

35 V

C10

2.2 nF

1 kV

C9

2.2 nF

1 kV

C13

100 nF

275 VAC

U5B

PC817D

+22 V

360 mA

+17.5 V

670 mA

+5 V

1.6 A

+3.3 V

1.74 A

RTN

VR1

1N4733A

5.1 V

U6

PKS606P

EF25

T1

1

6

7

8

10

9

2

3

5

4

L4

3.3

µH

-5 V

28 mA

L3

3.3

µH

U2

LM431A

2%

R16

1 k

Ω

R9

3.3 k

Ω

R12

56.2 k

Ω

1%

R11

3.92 k

Ω

1%

R10

150

Ω

R8

10 k

Ω

1%

C2

10

µF

50 V

C11

100 nF

50 V

C22

100 nF

50 V

C18

100

µF

50 V

C17

2200

µF

16 V

C16

2200

µF

16 V

C6

220

µF

10 V

C8

220

µF

10 V

C14

150

µF

35 V

C15

220

µF

35 V

U5A

PC817D

PI-4522-110906

PeakSwitch

C12

220 nF

50 V

L5

19 mH

D5

1N4007

D6

1N4007

C20

33

µF

400 V

D4

1N4007

D3

1N4007

F1

2 A

RV1

275 VAC

D

S

EN/UV

BP