离线式电源的增长使功率因数校正(PFC)成为必须的部分，以减少输入电流，满足未来调整的需要。开关电源采用桥式整流器，后接一个大电容，这会产生谐波电流。这些谐波只会增加电源的RMS输入电流，对真正的功率没有任何贡献。LT1508和LT1509 通过集成PFC和脉宽调制器(PWM)，可完全满足这一设计需要。 advertisement
Single IC, Power Factor Corrected, Off-Line Supply
Design Note 143
Kurk Mathews
An ever increasing number of off-line power supplies now lower part count and improved PC board layout. Start-up is
include power factor correction (PFC) in order to reduce controlled by separate PFC and PWM soft start pins. The
input current and meet future regulatory requirements. PWM Soft Start pin is held low, disabling the PWM output
Switching power supplies that incorporate a bridge recti- until the PFC stage is in regulation. The PWM will remain
fier followed by bulk capacitance create harmonic cur- enabled as long as the PFC output voltage stays above 73%
rents. These harmo……
