关于小功率电源，想谈谈成本问题，如何降成本！

先看看现在小功率电源与充电器的基本规范吧！

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     Standby power < 0.50W
2) California Energy Commission (CEC)
     Standby Power < 0.75W
      Average efficiency > 64% for Po=5W
3) Blue Angel
     Standby Power < 0.3W

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Linear
1) Low cost (< $0.3 PCBA for 5W)
2) Large size & heavy
3) Single line Input
4) Not meeting Green Mode

Switching Mode
1) Higher Cost (> $0.5 PCBA for 5W)
2) Universal line input
3) Meet Energy star, blue angel, CEC
4) EMI

RCC
    1) Lowest cost
    2) Variable Frequency
    3) Inconsistent performance



PWM
    1) $0.1 – $0.2 more than RCC
    2) Fixed frequency
    3) Consistent green mode & EMI

RCC SCH:
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1) No PWM IC
          ($0.1 - $0.2)

2) NPN Switch
         ($0.025)

PWM SCH:



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1) PWM IC + MOSFET
      ($0.1-0.2 + $0.125)
2) Integrated Switch High Voltage Switch
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1) Cost
     ($0.125 vs 0.025)
2) Efficiency
3) EMI Emitter Switching Topology

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Base Switching
1) Slow turn-off            
2) VCEO blocking rating
    (450V for MJE13003)

Emitter Switching
1) Fast turn-off
2) VCBO blocking rating
   (700V for MJE13003) EST Advantages
1) Fast turn-off time
2) VCBO blocking voltage rating
3) Low High Frequency EMI ? No Y-cap
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