A switching power supply includes a bridge rectifier, a switching device, and a controller. The bridge rectifier is operatively coupled to an alternating current (ac) signal, and outputs a rectified signal. The switching device is electrically connected in parallel with the bridge rectifier. The controller is responsive to the rectified signal and selectively controls the switching device to divert at least a portion of the rectified signal therethrough in response to the rectified signal. A met...

A Power Factor Correction (PFC) system providing near unity power factor for an AC power source (VAC) connected to a complex load. The system includes a bridge rectifier, boost or buck-boost converter, complex load, and pulse width modulation (PWM) controller to provide pulses with variable duty cycle to a power switch. The invention is a constant pulse proportional current (CPPC) PWM controller that generates trains of pulses constant in frequency and duty cycle for one semi-cycle of the VAC. T...

An AC-to-DC power converter that is capable of generating a regulated, isolated DC voltage output from a power factor corrected AC voltage input with improved efficiency. The AC-to-DC power converter is a two-stage power converter including a PFC stage connected in series to a power conversion stage. The PFC stage performs power factor correction using a zero current switching technique, and the power conversion stage includes a zero voltage switched half-bridge converter. The power conversion s...

A circuit for providing power factor correction in accordance with an embodiment of the present application may include a boost converter circuit and a control circuit receiving as inputs a rectified AC input voltage from a rectifier, a signal proportional to current through the boost inductor and the DC bus voltage across the capacitor of the boost converter. The control circuit provides a pulse width modulated signal to control the on time of a PFC switch. The control circuit further includes ...

Disclosed is a synchronous forward converter having a reverse current suppressor connected to the gate of a freewheel switch. The reverse current suppressor is configured to receive a control input signal generated by an internal circuitry of a power supply system where the forward converter locates, such as an enable signal, to detect the power-off of the forward converter, and in response thereto turn off the freewheel switch during the interruption of the input power of the forward converter....

A synchronous rectification circuit for power converters operable under fixed and/or variable frequencies where no current sense circuit or phase-lock circuit are needed is provided. It has a power switch coupled to a transformer for the rectification. A signal-generation circuit is used for generating a control signal in response to a magnetized voltage of the transformer, a demagnetized voltage of the transformer, and a magnetization period of the transformer. The control signal is coupled to ...

A synchronous rectification circuit for power converters operable under fixed and/or variable frequencies where no current sense circuit or phase-lock circuit are needed is provided. It has a power switch coupled to a transformer for the rectification. A signal-generation circuit is used for generating a control signal in response to a magnetized voltage of the transformer, a demagnetized voltage of the transformer, and a magnetization period of the transformer. The control signal is coupled to ...

A switch mode AC/DC converter with input current shaped for unity power factor. Input current is modulated by input voltage, and input inductor and isolation transformer are driven with the same duty ratio, with a low voltage across bulk capacitor. This voltage is determined only by input voltage amplitude. Energy stored in the leakage inductance of the transformer is returned back to the internal DC source. A soft switching circuit is connected to the primary side, eliminating the need for high...

An energy-feedback clamping circuit of a power converter is proposed. The converter includes a transformer coupled to a full-wave rectifier circuit. The clamping circuit includes: two clamping diodes having two anodes coupled to each other at a common-anode terminal and two cathodes coupled to two terminals of a secondary winding of the transformer, a first clamping capacitor having a first terminal coupled to a cathode of a first rectifying diode of the rectifier circuit and a second terminal c...

A vector controller for a polyphase synchronous rectifier, a method of vector-controlling a polyphase synchronous rectifier, and a synchronous rectifier incorporating the vector controller or the method. In one embodiment, the vector controller includes: (1) an input line voltage detector configured to detect voltages on at least two rectifier input lines and produce therefrom a neutral excursion vector and (2) a neutral excursion compensator, coupled to said input line voltage detector, that ap...