A control circuit is configured to sense an AC input voltage of a power factor correction (PFC) power circuit in a switching power converter, provide a control signal having an on-time and an off-time to at least one power switch of the PFC power circuit, and in response to detecting a peak voltage of the AC input voltage, increase the on-time of the control signal based on the sensed AC input voltage during an interval that begins with the peak voltage of the AC input voltage and ends with the next zero crossing following the peak voltage of the AC input voltage to improve a power factor of the switching power converter. Other example switching power converters, PFC power circuits and control circuits for controlling one or more power switches are also disclosed.

A control circuit is configured to sense an AC input voltage of a power factor correction (PFC) power circuit in a switching power converter, provide a control signal having an on-time and an off-time to at least one power switch of the PFC power circuit, and in response to detecting a peak voltage of the AC input voltage, increase the on-time of the control signal based on the sensed AC input voltage during an interval that begins with the peak voltage of the AC input voltage and ends with the next zero crossing following the peak voltage of the AC input voltage to improve a power factor of the switching power converter. Other example switching power converters, PFC power circuits and control circuits for controlling one or more power switches are also disclosed.

A secondary controller drives a light emitting element of a photocoupler such that a detection voltage V.sub.OUTS corresponding to an output voltage V.sub.OUT generated in an output capacitor C approximates to a reference voltage V.sub.REF. A primary controller controls a switching transistor M according to a feedback signal V.sub.FB. A protection circuit is activated and drives the light emitting element of the photocoupler when detecting an abnormal state. An auxiliary power supply circuit includes a power supply capacitor C provided separately from the output capacitor C and supplies a power supply voltage V.sub.CC to the protection circuit and an anode of the light emitting element of the photocoupler.

A secondary controller drives a light emitting element of a photocoupler such that a detection voltage V.sub.OUTS corresponding to an output voltage V.sub.OUT generated in an output capacitor C approximates to a reference voltage V.sub.REF. A primary controller controls a switching transistor M according to a feedback signal V.sub.FB. A protection circuit is activated and drives the light emitting element of the photocoupler when detecting an abnormal state. An auxiliary power supply circuit includes a power supply capacitor C provided separately from the output capacitor C and supplies a power supply voltage V.sub.CC to the protection circuit and an anode of the light emitting element of the photocoupler.

Bridgeless PFC converters. Example embodiments are methods of operating a power converter including operating the power converter during a positive half-line cycle of an alternating current (AC) source by: charging an inductance through a low-side switch with a first charging current having a first polarity; measuring the first charging current using a low-side current transformer (CT), while shorting a secondary winding of a high-side CT; and discharging the inductance through a high-side switch with a first discharging current having the first polarity. Operating the power converter during a negative half-line cycle of the AC source by: charging the inductance through the high-side switch with a second charging current having a second polarity; measuring the second charging current using the high-side CT, while shorting a secondary winding of the low-side CT; and discharging the inductance through the low-side switch with a second discharging current having the second polarity.

Bridgeless PFC converters. Example embodiments are methods of operating a power converter including operating the power converter during a positive half-line cycle of an alternating current (AC) source by: charging an inductance through a low-side switch with a first charging current having a first polarity; measuring the first charging current using a low-side current transformer (CT), while shorting a secondary winding of a high-side CT; and discharging the inductance through a high-side switch with a first discharging current having the first polarity. Operating the power converter during a negative half-line cycle of the AC source by: charging the inductance through the high-side switch with a second charging current having a second polarity; measuring the second charging current using the high-side CT, while shorting a secondary winding of the low-side CT; and discharging the inductance through the low-side switch with a second discharging current having the second polarity.

An AC/DC converter and conversion method are provided, in which an AC input is rectified and shaped by a waveform shaping capacitor. A current source circuit is used to provide the output current to the output load which has a parallel bulk capacitor. The current source circuit is switched on and off with timing which is dependent on the phase of the AC input signal. This enables a relatively high power factor, for example between 0.7 and 0.9, with low cost circuitry with few components.

A power regenerative converter, includes: a power module configured to include rectifiers and regenerative switches; a smoothing capacitor connected to direct-current power supply terminals, and that accumulates direct-current power during an alternating-current to direct-current conversion; a bus current detector that detects a bus current flowing between either of the direct-current power supply terminals and the smoothing capacitor; a power supply phase detector that detects a phase of an input power supply; a base drive signal generator that generates base drive signals that perform ON/OFF control of the regenerative switching elements based on a power supply phase detected by the power supply phase detection unit; a regeneration controller that performs a start and stop process of a power regenerative operation based on a detection result of the bus current detector and the base drive signals; and an overload detector that detects overload of a power regenerative converter based on the detection result of the bus current detector.

Bridgeless PFC converters. Example embodiments are methods of operating a power converter including operating the power converter during a positive half-line cycle of an alternating current (AC) source by: charging an inductance through a low-side switch with a first charging current having a first polarity; measuring the first charging current using a low-side current transformer (CT), while shorting a secondary winding of a high-side CT; and discharging the inductance through a high-side switch with a first discharging current having the first polarity. Operating the power converter during a negative half-line cycle of the AC source by: charging the inductance through the high-side switch with a second charging current having a second polarity; measuring the second charging current using the high-side CT, while shorting a secondary winding of the low-side CT; and discharging the inductance through the low-side switch with a second discharging current having the second polarity.

Bridgeless PFC converters. Example embodiments are methods of operating a power converter including operating the power converter during a positive half-line cycle of an alternating current (AC) source by: charging an inductance through a low-side switch with a first charging current having a first polarity; measuring the first charging current using a low-side current transformer (CT), while shorting a secondary winding of a high-side CT; and discharging the inductance through a high-side switch with a first discharging current having the first polarity. Operating the power converter during a negative half-line cycle of the AC source by: charging the inductance through the high-side switch with a second charging current having a second polarity; measuring the second charging current using the high-side CT, while shorting a secondary winding of the low-side CT; and discharging the inductance through the low-side switch with a second discharging current having the second polarity.