Design Idea DI-13
®
TinySwitch-II
3 W Universal Adapter
Application
3 W Adapter
Device
TNY264
Power Output
3W
Input Voltage
85-265 VAC
Output Voltage
9V
Topology
Flyback
®
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.
C5 2200 pF Y1
2
10T
x2
1
8
10T
28 AWG
5
D6
11DQ06
C6
330
µF
16 V
L2
Bead
C9
220
µF
25 V
9 V, 330 mA
D1 & D3
1N4007
C3
2.2 nF
1 kV
R4
330 kΩ
1/2 W
96T
33 AWG
3
RTN
RF1
L
8.2
Ω
C1 & C2
4.7
µF
400 V
D5
1N4937
VR2
BZX79-B8V2
85-265 VAC
N
D1 & D4
1N4007
D
R2
4.7 kΩ
1/8 W
EN/UV
BP
U1
TNY264P
S
U2
LTV817A
C4
0.1
µF
TinySwitch-II
L1
1 mH
Figure 1. TinySwitch-II 3 W Universal Adapter.
PI-3074-091402
DI-13
www.powerint.com
September 2002
DI-13
PI-3075-080902
Key Design Points
•
Design transformer for low leakage inductance.
•
Varnish transformer to practically eliminate acoustic
noise - gluing not required.
•
Maximum flux density of main transformer should be no
more than 3000 gauss.
•
Use primary RCD clamp that allows no more than
600 V across the
TinySwitch-II
DRAIN and SOURCE
pins.
•
Provide adequate copper area on PCB at the connection
to the
TinySwitch-II
SOURCE pin, for heatsinking.
Transformer Parameters
Core Material
Bobbin
Winding Order
Primary Inductance
Primary Resonant
Leakage Inductance (all
secondary windings shorted)
Core: EF 12.6, gapped for A
L
of 135 nH/T
2
Bobbin: Hical EF 12.6, 8 pin
Power Consumption (mW)
78%
76%
Efficiency (%)
74%
72%
70%
68%
85
135
185
235
285
Input Voltage (VAC)
Figure 2. Efficiency vs. Input Voltage.
PI-3374-091402
250
Primary (3-1)
Shield winding (1-2)
Secondary (8-5)
1.25 mH
700 kHz (min)
50
µH
200
150
100
Table 1. Transformer Construction Information.
50
0
75
95 115 135 155 175 195 215 235 255 275
Input Voltage (VAC)
Figure 3. Efficiency vs. Input Voltage.
For the latest updates, visit our Web site:
www.powerint.com
Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability.
Power Integrations does not assume any liability arising from the use of any device or circuit described herein, nor does it convey any
license under its patent rights or the rights of others. The products and applications illustrated herein may be covered by one or more U.S.
and foreign patents or potentially by pending U.S. and foreign patent applications assigned to Power Integrations. A complete list of Power
Integrations’ patents may be found at www.powerint.com.
The PI Logo,
TOPSwitch
,
TinySwitch
and
EcoSmart
are registered trademarks of Power Integrations, Inc.
PI Expert
is a trademark of Power Integrations, Inc. ©Copyright 2002, Power Integrations, Inc.
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