TNY253/254/255
+
1
T1
10
D1
1N4934
L1
15 H
C4
330 F
10 V
C5
47 F
10 V
+ 7.5 V
4
8
RTN
U2
SFH615-2
R2
1k
Optional
DC IN
120 - 375
VDC
C1
0.01 F
1 kV
R1
100
1/2 W
TinySwitch
U1
TNY253P
D
EN
BP
S
C2
56 pF
1 kV
C3
0.1 F
VR1
1N5235B
–
C6
680 pF
Y1 Safety
PI-2246-082898
Figure 9. 1.3 W TV Standby Circuit using TNY253.
D2
SB540
C4
2700 F
6.3 V
4
8
1
T1
10
L1
10
H
C5
220 F
10 V
+5V
R1
150 k
1W
C2
4700 pF
1 kV
D1
1N4937
RTN
Optional
240 - 375
VDC
C1
0.01 F
1 kV
TinySwitch
U1
TNY255P
D
EN
BP
S
U2
LTV817
R2
68
C3
0.1 F
VR1
1N5229B
PI-2242-082898
Figure 10. 10 W Standby Supply Circuit.
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
constant voltage and constant current output. TinySwitch is
always powered from the input high-voltage, therefore it does
not require bias winding for power. Consequently, its opera-
tion is not dependent on the level of the output voltage. This
allows for constant current charger designs that work down to
zero volts on the output.
6
Rev E
02/12
POWERINT [ POWER INTEGRATIONS, INC. ]
