TNY253/254/255
1
T1
10
D5
FR201
C5
220
µF
25 V
L2
3.3
µH
C6
220
µF
16 V
R8
820
Ω
R7
100
Ω
R9
47
Ω
+ 5.2 V
D1
D2
1N4005 1N4005
R2
100 kΩ
1W
C4
2200 pF
D6
1N4937
D
TinySwitch
EN
BP
S
2
5
RTN
U1
TNY254P
85-265
VAC
RF1
U2
LTV817
10
Ω
C1
6.8
µF
400 V
C2
4.7
µF
400 V
Fusible
D3
D4
1N4005 1N4005
R1
1.2 kΩ
C3
0.1
µF
Q1
2N3904
R3
22
Ω
R5
18
Ω
1/8 W
VR1
1N5230B
4.7 V
R6
0.82
Ω
1/2 W
PI-2244-082898
L1
560
µH
C8
2.2 nF
Y1 Safety
R4
1
Ω
1W
Figure 11. 3.6 W Constant Voltage-Constant Current Cellular Phone Charger Circuit.
1
T1
D3
1N3934
10
D1
1N4004
5
6
C6
100
µF
16V
+9V
VR1
1N5239B
RTN
115 VAC
± 15%
C1
2.2
µF
200 V
C2
2.2
µF
200 V
D
TinySwitch
EN
BP
C4
68 pF
1 KV
U1
TNY253P
S
RF1
1.8
Ω
Fusible
D2
1N4004
R2
100
Ω
C3
0.1
µF
C5
2.2 nF
Y1 Safety
PI-2190-031501
Figure 12. 0.5 W Open Loop AC Adapter 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.
Figure11 shows a 5.2V, 3.6W cellular phone charger circuit
that uses the TNY254 and provides constant voltage and constant
current output over an universal input (85 to 265VAC) 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 (44kHz) 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 5.2V output. Additional filtering
C
7/01
7
POWERINT [ POWER INTEGRATIONS, INC. ]
