www.powerint.com

September 2002

DI-13

Design Idea DI-13

TinySwitch-II

3 W Universal Adapter

Design Highlights

• No-load consumption less than 250 mW at 230 VAC

• Compact design: 2.0” x 1.2” x 0.75”

• Minimum parts count and single sided PC board ensures

cost-effective solution

• High frequency operation allows compact EF12.6

transformer

• Enhanced ON/OFF control allows simple Zener reference

and eliminates the need for loop compensation

• Built-in circuitry practically eliminates audible noise with

standard varnished transformer

• No-load regulation achieved without pre-load resistor

• Well defined frequency jitter feature reduces EMI–simple

input

π filter meets CISPR22 Class B/EN55022B

• Self-protecting hysteretic thermal shutdown: power supply

automatically recovers when fault is removed

This 3 W single output, universal input power supply is

available as a Design Accelerator Kit (DAK-14) including

samples and documentation. With 71% minimum efficiency at

full load, compliance to CISPR22 Class B, small size, and low

parts count, the DAK-14 showcases the significant advantages

of TinySwitch-II in low power adapter applications.

Operation

The digital ON/OFF control scheme of TinySwitch-II allows

tight regulation using a low cost secondary Zener reference and

eliminates the need for loop compensation. In addition, no pre-

load is required to maintain regulation at light load, helping to

reduce measured no-load consumption to <250 mW at

265 VAC – see Figure 3. TinySwitch-II also provides auto-

restart to reduce output overload current during fault conditions.

Figure 1. TinySwitch-II 3 W Universal Adapter.

Application

3 W Adapter

TNY264

9 V

Power Output

3 W

Input Voltage

Output Voltage

Topology

Device

85-265 VAC

Flyback

®

PI-3074-091402

D1 & D3

1N4007

D1 & D4

1N4007

C1 & C2

4.7

µF

400 V

C3

2.2 nF

1 kV

N

L

RF1

8.2

Ω

C4

0.1

µF

85-265 VAC

9 V, 330 mA

L1

1 mH

D6

11DQ06

C9

220

µF

25 V

L2

Bead

U1

TNY264P

U2

LTV817A

VR2

BZX79-B8V2

R4

330 k

Ω

1/2 W

D5

1N4937

R2

4.7 k

Ω

1/8 W

8

3

5

C5 2200 pF Y1

TinySwitch-II

D

S

BP

EN/UV

2

1

RTN

C6

330

µF

16 V

96T

33 AWG

10T

28 AWG

10T

x2

®