Datasheet
TNY253/254/255
7
D
4/03
Figure 11. 3.6 W Constant Voltage-Constant Current Cellular Phone Charger Circuit.
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 operation
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.
Figure 11 shows a 5.2 V, 3.6 W cellular phone charger circuit
that uses the TNY254 and provides constant voltage and constant
current output over an universal input (85 to 265 VAC) range.
The AC input is rectified and filtered by D1 - D4, C1 and C2 to
create a high voltage DC bus connected to T1 in series with the
high voltage MOSFET inside the TNY254. The inductor L1
forms a π-filter in conjunction with C1 and C2. The resistor R1
damps resonances in the inductor L1. The low frequency of
operation of TNY254 (44 kHz) allows use of the simple π-filter
described above in combination with a single Y1-capacitor C8
to meet worldwide conducted EMI standards. The diode D6,
capacitor C4 and resistor R2 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 D5 and C5 to provide the 5.2 V output. Additional filtering
Figure 12. 0.5 W Open Loop AC Adapter Circuit.
PI-2244-042303
TinySwitch
D
S
EN
BP
+ 5.2 V
RTN
D1
1N4005
C1
6.8 µF
400 V
Fusible
RF1
10 Ω
C3
0.1 µF
85-265
VAC
L1
560 µH
D2
1N4005
D3
1N4005
D4
1N4005
R2
100 kΩ
1 W
U2
LTV817
D5
FR201
L2
3.3 µH
C5
220 µF
25 V
C2
4.7 µF
400 V
C6
220 µF
16 V
R7
100 Ω
R3
22 Ω
R4
1 Ω
1 W
R9
47 Ω
Q1
2N3904
R8
820 Ω
VR1
1N5230B
4.7 V
C8
2.2 nF
Y1 Safety
U1
TNY254P
C4
2200 pF
D6
1N4937
R6
0.82 Ω
1/2 W
T1
R1
1.2 kΩ
1
2
5
10
R5
18 Ω
1/8 W
PI-2190-042303
TinySwitch
D
S
EN
BP
+ 9 V
RTN
D1
1N4004
C1
2.2 µF
200 V
Fusible
RF1
1.8 Ω
C4
68 pF
1 kV
115 VAC
± 15%
R2
100 Ω
D2
1N4004
C3
0.1 µF
D3
1N3934
C6
100 µF
16V
C2
2.2 µF
200 V
VR1
1N5239B
C5
2.2 nF
Y1 Safety
U1
TNY253P
T1
1
5
6
10