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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)
90V/63Hz
0.163
14.9
115V/60Hz
0.122
14.5
230V/50Hz
0.056
14.5
264V/47Hz
0.053
14.7
Table 2 Standby power at no load(4mA LED current)
Input voltage
Vo(V)
90V/63Hz
12.205
115V/60Hz
12.205
230V/50Hz
12.204
264V/47Hz
12.204
Table 3 Line Regulation & Load Regulation
Input voltage
90Vac/60HZ
115Vac/60HZ
132Vac/60HZ
180Vac/50HZ
230Vac/50HZ
264Vac/50HZ
Line Regulation
Load Regulation
No load
12.205
12.205
12.204
12.205
12.204
12.204
Half load
12.203
12.203
12.203
12.203
12.203
12.202
0.008%
0.033%
Full load
12.202
12.202
12.202
12.201
12.201
12.201
<1%
<5%
Pass
Pass
Specification
Test result
Vo(V)
12.202
12.202
12.201
12.201
Io(A)
1
1
1
1
η
81.9
84.2
84.2
83.0
Specification
>75%
Test result
Pass
Pin(W)
0.19
0.20
0.25
0.27
Specification
<0.3W
Test result
Pass
DS-RS2201-01
Nov, 2007
www.Orister.com
ORISTER [ ORISTER CORPORATION ]
