®
Design Idea DI-33
Tin yS w it c h®-II Wide Range DVD
Supply: <50 mW No-load Consumption
Topology
Flyback
Device
Power Output
Input Voltage
Output Voltage
Application
DVD Player
11 W cont. 17 W pk. 85-265 VAC
TNY268P
+3.3 V, +5.0 V, +12.0 V, -12 V
the use of foil windings and dual sense feedback via R15
and R16.
Design Highlights
• No-load input power <50 mW
• To minimize potential noise coupling to the SOURCE pin
during common mode surges, the Y1 capacitor C8 is
connected between secondary return and the HV DC rail.
• Resistors R5 and R7 damp ringing to improve EMI.
• Optionalsoft-finishcapacitorC7eliminatesoutputstartup
overshoot.
• Optional under-voltage resistor R1 provides clean startup
and prevents output glitches on power down.
R1 = (VUV-2.5 V)/50 µA.
• Small loop areas in the secondary layout around D10,
C12, D9, C11, D7, C15, D8 and C9 together with post-
filters L2/C20, L3/C17 and L4/C18 provide low output
ripple, below 50 mV p-p.
• 700 mW of output power with 1 W input
• Built-in frequency jitter allows low cost π filter
• 132 kHz operation minimizes transformer size and turns,
providing good cross-regulation
• High efficiency – >77% minimum
• MeetsCISPR22B/EN55022BandFCCBwith>10dBmargin
Key Design Points
• Anoptionallowvoltagebiascircuit,D9andC10,powersU1
via R6, reducing light and zero load power consumption.
This provides bias current that would otherwise be provided
from the DRAIN by the internal high voltage current source.
The current source is disabled when the BP pin is fed
externally, an internal clamp limiting the voltage to
6.3 V. The bias supply is designed to produce 7.5 V at
no-load. Resistor R6 is chosen to provide
approximately 500 µA into the BP pin, the maximum
consumption at no-load.
12 V, 0.4 A
8
13
9
L2
3.3 uH
D7
UF4003
C20
150 µF
25 V
C15
470 µF
25 V
D9
1N5822
5 V, 1.6 A
3.3 V, 0.7 A
RTN
L3
3.3 uH
• Good cross-regulation on 5 V and 3.3 V outputs is
achieved by minimizing secondary leakage through
C11
C17
1800 µF
470 µF
10 V
D10
1N5822
25 V
C8
1 nF
Y1
L4
3.3 uH
C12
C18
470 µF
10 V
1000 µF
10 V
R7
100 Ω
11
D1 & D2
1N4007
C2
0.01 µF
1 kV
VR1
1
4
C9
C6
P6KE180
220 µF 220 µF
25 V
25 V
D8 UF4003
-12 V, 0.1 A
F1
R5
47 Ω
14
C1 & C4
33 µF
R9
R6
R12
L
R1
2 MΩ
200 Ω
D6 1N4148
3.3 kΩ
1 Ω
400 V
C3
0.047 µF
X2
1/2 W
R16
6.34 kΩ
1%
(Optional)
6
85-265
VAC
C10
10 µF
50 V
D5
1N4007
R8
1 kΩ
U2
R10
3.3 kΩ
R15
20 kΩ
5,7
Tin yS w it c h -II
N
D
1%
EN
C14
0.1 µF
D3 & D4
1N4007
C7
BP
10 µF
50 V
U3
TL431
S
U1
TNY268
C5
0.1 µF
50 V
L1
R13
U2
PC817
1.4 mH
0.5 A
10 kΩ
1%
PI-3205-091302
Figure 1. TinySwitch-II DVD Player Schematic.
September 2002
DI-33
www.powerint.com