Design Idea DI-33
®
TinySwitch-II
Wide Range DVD
Supply: <50 mW No-load Consumption
Application
DVD Player
Device
TNY268P
Power Output
11 W cont. 17 W pk.
Input Voltage
85-265 VAC
Output Voltage
+3.3 V, +5.0 V, +12.0 V, -12 V
®
Topology
Flyback
Design Highlights
•
•
•
•
No-load input power <50 mW
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
• Meets CISPR22B/EN55022B and FCC B with >10 dB margin
•
•
•
•
Key Design Points
• An optional low voltage bias circuit, D9 and C10, powers U1
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.
• Good cross-regulation on 5 V and 3.3 V outputs is
achieved by minimizing secondary leakage through
C8
1 nF
Y1
•
the use of foil windings and dual sense feedback via R15
and R16.
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.
Optional soft-finish capacitor C7 eliminates output startup
overshoot.
Optional under-voltage resistor R1 provides clean startup
and prevents output glitches on power down.
R1 = (V
UV
-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.
12 V, 0.4 A
8
D7
UF4003
D9
1N5822
L2
3.3 uH
C15
470
µF
25 V
L3
3.3 uH
C20
150
µF
25 V
5 V, 1.6 A
13
C11
1800
µF
25 V
D10
1N5822
9
C17
470
µF
10 V
3.3 V, 0.7 A
L4
3.3 uH
C12
1000
µF
10 V
R7
100
Ω
D1 & D2
1N4007
VR1
P6KE180
C2
0.01
µF
1 kV
1
11
C9
220
µF
25 V
D8 UF4003
C1 & C4
33
µF
400 V
R5
47
Ω
D5
1N4007
D
C18
470
µF
10 V
RTN
C6
220
µF
25 V
-12 V, 0.1 A
R9
200
Ω
R16
6.34 kΩ
1%
R10
3.3 kΩ
C14
0.1
µF
U3
TL431
R15
20 kΩ
1%
F1
L
85-265
VAC
N
D3 & D4
1N4007
C3
0.047
µF
X2
R1
2 MΩ
(Optional)
4
14
R6
R12
D6 1N4148 3.3 kΩ 1
Ω
1/2 W
6
C10
R8
10
µF
1 kΩ
50 V
5,7
U2
TinySwitch-II
EN
BP
L1
1.4 mH
0.5 A
U1
S
TNY268
C5
0.1
µF
50 V
U2
PC817
C7
10
µF
50 V
R13
10 kΩ
1%
PI-3205-091302
Figure 1. TinySwitch-II DVD Player Schematic.
DI-33
www.powerint.com
September 2002
DI-33
PI-3301-091602
1200
1000
800
115 VAC
230 VAC
TRANSFORMER PARAMETERS
Core Material
Bobbin
Himag MZ4 EEL25.4, or equivalent,
2
Gap for A
L
of 344 nH/T
EEL25 Vertical 14 Pins
Shield: 32T, 2 x 32 AWG
Primary: 64T, 2 x 32 AWG
Bias: 6T, 4 x 32 AWG
Shield 2: 4T, 4 x 32 AWG
+12 V: 4T, 4 x 32 AWG
+5 V: 1T, 14 mm Cu Foil
+3.3 V: 2T, 14 mm Cu Foil
-12 V: 7T, 4 x 32 AWG
3 mm margin tape on both
sides of bobbin.
Shield (NC-5), tape,
Primary (1-4), tape,
Bias (7-6), tape,
Shield (NC-7), tape,
12 V (13-8), 3.3 V (11-9),
5 V (9-13), tape,
-12 V (14-11), tape
(NC - no connect)
1420
µH ±25%
500 kHz (minimum)
P
IN
(mW)
600
400
Winding Details
200
0
0
100 200 300 400 500 600 700 800
P
OUT
(mW)
Figure 2. P
IN
vs. P
OUT
Curve.
PI-3302-091302
80
70
60
50
40
QP
AV
Winding Order
(Pin Numbers)
Inductance
Quasi Peak
dBµV
30
20
10
0
-10
-20
0.15
1.0
10.0
-100.0
Average
Primary Resonant
Frequency
(Pins 1-4, all other open)
Table 1. Transformer Construction Information.
MHz
Figure 3. Conducted EMI with Artificial Hand Connected to Output Return.
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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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