Partial active electrical source power factor correction circuit

The present invention provides a part active power factor correction circuit which has a branch circuit arranged between the anode of isolating diode and cathode of bridge rectification circuit. The correction circuit includes a second capacitor with one end connected with the anode of the isolating diode, the other end connected with the cathode of a second diode the anode of which is connected with the cathode of a third diode, the anode of the third diode is connected with one end of a third capacitor, and the other end of the third capacitor is connected with the cathode of dc output end of the bridge rectification circuit; the joint end of the connection between the anode of the second diode and the cathode of the third diode is connected to the other end of the ac input end of the bridge rectification circuit which has no connection with the inductor; a controlled switch is connected between the cathode of the second diode and the anode of the third diode; the controlled switch is controlled to close if the dc detected voltage of the bridge rectification circuit is lower than a critical voltage and is controlled to turn off if the dc detected voltage of the bridge rectification circuit is higher than a critical voltage.