TNY253/254/255
1
T1
10
D5
FR201
C5
220 F
25 V
L2
3.3 H
C6
220 F
16 V
R8
820
+ 5.2 V
D1
1N4005
D2
1N4005
R2
100 k
1W
C4
2200 pF
D6
1N4937
TinySwitch
U1
TNY254P
2
5
RTN
D
EN
BP
85 - 265
VAC
RF1
10
Fusible
D3
1N4005
C1
6.8 F
400 V
C2
4.7 F
400 V
S
U2
LTV817
R9
47
Q1
2N3904
R7
100
R3
22
R5
18
1/8 W
D4
1N4005
R1
1.2 k
C3
0.1 F
VR1
1N5230B
4.7 V
L1
560 H
C8
2.2 nF
Y1 Safety
R4
1
1W
R6
0.82
1/2 W
PI-2244-082898
Figure 11. 3.6 W Constant Voltage-Constant Current Cellular Phone Charger Circuit.
1
T1
10
D3
1N3934
C6
100 F
16V
VR1
1N5239B
+9V
D1
1N4004
5
6
RTN
115 VAC
± 15%
C1
2.2 F
200 V
C2
2.2 F
200 V
C4
68 pF
1 KV
TinySwitch
U1
TNY253P
D
EN
BP
S
RF1
1.8
D2
1N4004
R2
100
C3
0.1 F
C5
2.2 nF
Y1 Safety
Fusible
PI-2190-031501
Figure 12. 0.5 W Open Loop AC Adapter Circuit.
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
is provided by L2 and C6. The output voltage is determined
by the sum of the optocoupler U2 LED forward drop (~ 1 V)
and Zener diode VR1 voltage. The resistor R8, maintains a
bias current through the Zener to improve its voltage tolerance.
A simple constant current circuit is implemented using the V
BE
of transistor Q1 to sense the voltage across the current sense
resistor R4, which can be made up of one or more resistors to
Rev E
02/12
7
POWERINT [ POWER INTEGRATIONS, INC. ]
