Datasheet
D
4/03
TNY253/254/255
6
Figure 9. 1.3 W TV Standby Circuit using TNY253.
Figure 10. 10 W Standby Supply Circuit.
10 W Standby
The TNY255 is ideal for standby applications that require up to
10 W of power from 230 VAC or 100/115 VAC with doubler
circuit. The TNY255 operates at 130 kHz as opposed to 44 kHz
for TNY253/254. The higher frequency operation allows the
use of a low cost EE16 core transformer up to the 10 W level.
Figure 10 shows a 5 V, 10 W 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
standby circuit. The high voltage DC bus is applied to the
primary winding of T1 in series 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 5 V ouput. Additional filtering is provided by L1
and C5. The output voltage is determined by the sum of the
optocoupler U2 LED forward drop (~ 1 V) and Zener diode
VR1 voltage. The resistor R2, maintains a bias current through
the Zener to improve its voltage tolerance. For tighter tolerance,
a TL431 precision reference IC feedback circuit may be used.
Cellular Phone Charger
The TinySwitch is well suited for applications that require a
PI-2242-042303
TinySwitch
D
S
EN
BP
+ 5 V
RTN
C1
0.01 µF
1 kV
C3
0.1 µF
240-375
VDC
R1
150 kΩ
1 W
U2
LTV817
D2
SB540
L1
10 µH
C4
2700 µF
6.3 V
C5
220 µF
10 V
VR1
1N5229B
U1
TNY255P
C2
4700 pF
1 kV
T1
1
4
8
10
R2
68 Ω
D1
1N4937
Optional
PI-2246-042303
DC IN
120-375 VDC
TinySwitch
D
S
EN
BP
+ 7.5 V
RTN
C3
0.1 µF
R2
1 kΩ
VR1
1N5235B
C1
0.01 µF
1 kV
R1
100 Ω
1/2 W
C2
56 pF
1 kV
D1
1N4934
L1
15 µH
C5
47 µF
10 V
C4
330 µF
10 V
U1
TNY253P
T1
U2
SFH615-2
C6
680 pF
Y1 Safety
1
4
8
10
Optional
+