TNY253/254/255
D1
1N4934
L1
15 µH
T1
1
4
10
+
+ 7.5 V
RTN
C4
330 µF
10 V
C5
47 µF
10 V
8
Optional
TinySwitch
EN
R1
100 Ω
1/2 W
U2
SFH615-2
D
S
DC IN
120-375 VDC
C1
0.01 µF
1 kV
U1
TNY253P
BP
R2
1 kΩ
C3
C2
0.1 µF
56 pF
1 kV
VR1
1N5235B
–
C6
680 pF
Y1 Safety
PI-2246-082898
Figure 9. 1.3 W TV Stand-by Circuit using TNY253.
D2
SB540
L1
10 µH
T1
1
4
10
8
+ 5 V
C2
4700 pF
1 kV
R1
150 kΩ
1 W
C4
2700 µF
6.3 V
C5
220 µF
10 V
RTN
D1
1N4937
TinySwitch
D
S
EN
Optional
U1
TNY255P
BP
C1
0.01 µF
1 kV
R2
68 Ω
U2
LTV817
240-375
VDC
C3
0.1 µF
VR1
1N5229B
PI-2242-082898
Figure 10. 10 W PC Stand-by Supply Circuit.
PC Standby
with the integrated high voltage MOSFET inside the TNY255.
The diode D1, capacitor C2 and resistor R1 comprise the clamp
circuit that limits the turn-off voltage spike on the TinySwitch
DRAIN pin to a safe value. The secondary winding is rectified
and filtered by D2 and C4 to provide the 5V ouput. Additional
filtering is provided by L1 and C5. The output voltage is
determined by the sum of the optocoupler U2 LED forward
drop (~ 1V) and Zener diode VR1 voltage. The resistor R2,
maintains a bias current through the Zener to improve its
voltage tolerance.
TheTNY255wasdesignedspecificallyforapplicationssuchas
PC standby, which require up to 10W of power from 230VAC
or 100/115VAC with doubler circuit. The TNY255 operates at
130kHz as opposed to 44kHz for TNY253/254. The higher
frequency operation allows the use of a low cost EE16 core
transformer up to the 10W level. Figure10 shows a 5V, 10W
circuit for such an application. The circuit operates from the
high voltage DC supply already available from the main power
supply. Capacitor C1 filters the high voltage DC supply, and is
necessary only if there is a long trace length from the source of
the DC supply to the inputs of the PC standby circuit. The high
voltage DC bus is applied to the primary winding of T1 in series
Cellular Phone Charger
The TinySwitch is well suited for applications that require a
C
6
7/01
POWERINT [ Power Integrations ]
