®
Design Idea DI-13
Tin yS w it c h®-II
3 W Universal Adapter
Application
Power Output
Input Voltage
Topology
Device
Output Voltage
Flyback
3 W
85-265 VAC
9 V
3 W Adapter
TNY264
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.
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-protectinghystereticthermalshutdown:powersupply
automatically recovers when fault is removed
Operation
The digital ON/OFF control scheme of TinySwitch-II allows
tightregulationusingalowcostsecondaryZenerreferenceand
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-
restarttoreduceoutput overloadcurrentduringfaultconditions.
C5 2200 pF Y1
2
10T
x2
D6
L2
11DQ06
Bead
9 V, 330 mA
RTN
8
1
C9
C6
330 µF
16 V
220 µF
10T
28 AWG
D1 & D3
1N4007
96T
33 AWG
R4
330 kΩ
1/2 W
C3
2.2 nF
1 kV
25 V
5
3
RF1
8.2 Ω
L
C1 & C2
4.7 µF
400 V
VR2
BZX79-B8V2
D5
1N4937
85-265 VAC
N
D
EN/UV
BP
R2
4.7 kΩ
1/8 W
D1 & D4
1N4007
U2
LTV817A
U1
TNY264P
S
Tin yS w it c h -II
C4
0.1 µF
L1
1 mH
PI-3074-091402
Figure 1. TinySwitch-II 3 W Universal Adapter.
September 2002
DI-13
www.powerint.com