Rev. F 08/16

7

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TNY253/254/255

TNY253/254/255

Figure 11. 3.6 W Constant Voltage-Constant Current Cellular Phone Charger 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

Figure 12. 0.5 W Open Loop AC Adapter Circuit.

PI-2244-082898

TinySwitch

D

S

EN

BP

+ 5.2 V

RTN

D1

1N4005

C1

6.8 F

400 V

Fusible

RF1

10

C3

0.1 F

85 - 265

VAC

L1

560 H

D2

1N4005

D3

1N4005

D4

1N4005

R2

100 k

1 W

U2

LTV817

D5

FR201

L2

3.3 H

C5

220 F

25 V

C2

4.7 F

400 V

C6

220 F

16 V

R7

100

R3

22

R4

1

1 W

R9

47

Q1

2N3904

R8

820

VR1

1N5230B

4.7 V

C8

2.2 nF

Y1 Safety

U1

TNY254P

C4

2200 pF

D6

1N4937

R6

0.82

1/2 W

T1

R1

1.2 k

1

2

5

10

R5

18

1/8 W

PI-2190-031501

TinySwitch

D

S

EN

BP

+ 9 V

RTN

D1

1N4004

C1

2.2 F

200 V

Fusible

RF1

1.8

C4

68 pF

1 KV

115 VAC

± 15%

R2

100

D2

1N4004

C3

0.1 F

D3

1N3934

C6

100 F

16V

C2

2.2 F

200 V

VR1

1N5239B

C5

2.2 nF

Y1 Safety

U1

TNY253P

T1

1

5

6

10