AC-DC power converter with power factor correction

A method of applying power factor correction to an AC-DC power converter using a charge pump circuit, said method comprising steps of:

• converting an AC line voltage into a rectified line voltage,
• applying the rectified line voltage to a DC supply voltage of a resonant DC-DC converter through a rectifying element,
• generating a resonant inverter voltage by switching a resonant inverter at a fixed or controllable switching frequency,
• rectifying the resonant inverter voltage to generate a DC output voltage or DC output current,
• drawing charging pulses, at the switching frequency, from the AC line voltage into a pump or flying capacitor connected between the rectified line voltage and the resonant inverter voltage, wherein electrical charges of the charging pulses vary proportionally to an instantaneous amplitude of the AC line voltage, and
• discharging the pump or flying capacitor into a smoothing capacitor, connected to the DC supply voltage, by supplying current pulses, at the switching frequency, into the smoothing capacitor,
• wherein the charge pump circuit comprises:
• the smoothing capacitor connected to the DC supply voltage of the resonant DC-DC converter, and
• the pump or flying capacitor connected from the resonant inverter voltage to the rectified line voltage,
• wherein the charge pump circuit is configured for, during a cycle of the switching frequency, sequentially cycling through states of:
• a first state where each of the rectifying element and the AC rectification circuit is non-conducting/off and a voltage across the pump/flying capacitor remains substantially constant,
• a second state where the AC rectification circuit is conducting/on and the rectifying element is non-conducting/off to charge the pump/flying capacitor by line current drawn from the AC line voltage,
• a third state where each of the rectifying element and the AC rectification circuit is non-conducting/off and the voltage across the pump/flying capacitor remains substantially constant, and
• a fourth state where the AC rectification circuit is in a non-conducting/off state and the rectifying element is in a conducting/on state such that discharge current flows from the pump/flying capacitor into the smoothing capacitor to increase the DC supply voltage of the resonant inverter and decrease the voltage across the pump/flying capacitor;
• wherein the charge pump circuit is further configured for:
• cycling through its second state during a rising edge of a waveform of the resonant inverter voltage, and
• cycling through its fourth state during a falling edge of the waveform of the resonant inverter voltage;
• and
• wherein a capacitance of the smoothing capacitor and a capacitance of the pump/flying capacitor are selected such that the DC supply voltage of the resonant inverter is higher than the AC line voltage across an entire cycle of the AC line voltage.