Page No. : 7/7

DS-RS2201-01

Nov, 2007

www.Orister.com

Features of Power supply design

Switching power supply design of fly back current control, discontinuous( a little continuous on the low voltage) current

operating mode.

Start-up current of power supply is designed of 0.5-3mA，the amplification multiple of power transistor should be calculate

as 10 times. To choose start-up resistor, the base current of power transistor must be 0.05-0.3mA when power supply

starts up. So the power consumption of start-up resistor should be reduced 10 times to reduce standby power consumption.

C5=680pF，the maximum operating frequency is about 60KHz.

Switching transformer providing operation current for RS2201 with operating power supply consults winding commutating

output 4.8-9V(6V is recommend).

If the maximum value of primary peak current of switching transformer is 0.8A. When demagnetization voltage is 140V in

220Vac, the maximum output power is 22W considering of power supply efficiency or other factors. If the wide voltage and

90V demagnetization voltage in 110Vac, a little continuous current mode is adapted when the voltage is below 95Vac, the

maximum output power is 18W.

The choice of power transistor: If the maximum peak value current is 0.8A, the βvalue of power transistor should reach

10@5Vce@0.8A considering of OB open current and the corresponding detecting resistor is 0.75Ω. The power transistor

should work at the saturation zone in any case and detecting resistor is 0.6V/the maximum value peak current.

Even the RS2201 has thermal protection, but if high output power is needed, it would reduce output power and output

voltage if widening thermolysis area of PCB is not considered. And when the output power is high, power transistor

thermolysis issue must be considered.

RS2201 12W（12V/1A）DEMO CHARACTERISTIC TEST REPORT

Table 1 Input characteristic at full load

Input voltage

Irms(A)

Pin(W)

Vo(V)

Io(A)

η

Specification

Test result

90V/63Hz

0.163

14.9

12.202

1

81.9

115V/60Hz

0.122

14.5

12.202

1

84.2

230V/50Hz

0.056

14.5

12.201

1

84.2

264V/47Hz

0.053

14.7

12.201

1

83.0

>75%

Pass

Table 2 Standby power at no load(4mA LED current)

Input voltage

Vo(V)

Pin(W)

Specification

Test result

90V/63Hz

12.205

0.19

115V/60Hz

12.205

0.20

230V/50Hz

12.204

0.25

264V/47Hz

12.204

0.27

<0.3W

Pass

Table 3 Line Regulation & Load Regulation

Input voltage

No load

Half load

Full load

Specification

Test result

90Vac/60HZ

12.205

12.203

12.202

115Vac/60HZ

12.205

12.203

12.202

132Vac/60HZ

12.204

12.203

12.202

180Vac/50HZ

12.205

12.203

12.201

230Vac/50HZ

12.204

12.203

12.201

264Vac/50HZ

12.204

12.202

12.201

Line Regulation

0.008%

<1%

Pass

Load Regulation

0.033%

<5%

Pass