A method involves controlling, for a duration of a first modulation period, a first average off-time of a main switch of a power converter such that the first average off-time of the main switch corresponds to a first intermediate valley number of multiple intermediate valley numbers, an average of the intermediate valley numbers corresponding to a target number of valleys of a resonant waveform at a drain node of the main switch. A second intermediate valley number of the intermediate valley numbers is selected upon expiration of the first modulation period. A difference of the second intermediate valley number and the first intermediate valley number is equal to a fractional valley number offset. A second average off-time of the main switch is controlled for a duration of a second modulation period such that the second average off-time of the main switch corresponds to the second intermediate valley number.

The subject application provides a zero-voltage switching flyback converter comprising: a transformer having a primary winding and a secondary winding; a primary switch and a secondary switch for conducting the currents flowing in the primary winding and secondary winding respectively. A timing control method for operating the flyback converter are provided to accomplish zero-voltage switch by turning on the secondary switch twice within one switching power cycle.

There is described a snubber circuit comprising an electronic switch. The circuit includes an impedance network comprising reactive circuit elements to smooth energy transients if the electronic switch is turned off and if the switch is turned on. A resistive element dissipates energy released by at least one of the reactive circuit elements. The resistive element is of a load to be driven using the electronic switch. A power supply unit may include the described snubber circuit.

A transient current in a rectifier circuit is efficiently reduced. In a rectifier circuit, a first rectifier is provided between the first terminal and a second terminal. In the rectifier circuit, when a switch element is turned ON, a primary winding current flows from a power source to a primary winding in a transformer. When the switch element is turned OFF, a second rectifier current flows from a secondary winding in the transformer to a second rectifier. When the second rectifier current flows, a first reverse voltage is applied between the first terminal and the second terminal. The first reverse voltage is a reverse voltage applied instantaneously.

This application discloses a switched-inductor power converter, a communication system, and a method. The switched-inductor power converter includes a coupling winding and a unidirectional conduction circuit, and the coupling winding and the unidirectional conduction circuit are connected in series to form a closed loop. A leakage inductor is formed after the coupling winding and a power inductor are magnetically coupled. Existence of the leakage inductor and the unidirectional conduction circuit may suppress a reverse recovery stress of a first diode, to further reduce a reverse recovery current of the first diode, and reduce a reverse recovery loss of the first diode.

An active flyback converter is transitioned between a plurality of operational states based on a comparison of a control voltage signal to voltage thresholds and a count of a number of consecutive switching cycles during which a clamp switch is kept off. The plurality of operational states includes a run state, an idle state, a first burst state, and a second burst state. Each set of consecutive switching cycles of the first burst state includes a determined number of switching cycles during which signals are generated to turn the power switch on and off and to maintain an off state of the clamp switch, and a switching cycle in a determined position in the set of switching cycles during which signals are sequentially generated to turn the power switch on, turn the power switch off, turn the clamp switch on and turn the clamp switch off.

A method for controlling an active snubber circuit includes measuring a gate voltage at a first transistor and measuring a gate voltage at a second transistor. The method also includes determining whether the first transistor and the second transistor are in the same state based on the gate voltage measured at the first transistor and the gate voltage measured at the second transistor. The method also includes, in response to a determination that the first transistor and the second transistor are in the same state, enabling the active snubber circuit. The method also includes, in response to a determination that the first transistor and the second transistor are not in the same state, disabling the enable signal. The method also includes disabling the active snubber circuit in response to the enable signal being disabled.

A controller configured for use in a power converter. The controller includes a control circuit coupled to receive an input line voltage sense signal representative of an input voltage of the power converter. The control circuit is configured to generate a control signal in response to a request signal representative of an output of the power converter. The control signal represents a delay time to turn on a power switch after a turn on of a clamp switch in response to the input line voltage sense signal. The control circuit can further generate a clamp drive signal to control a clamp driver and a drive circuit configured to generate a drive signal to control the power switch to transfer energy from an input of the power converter to the output of the power converter.

The subject invention reveals new methods and structures for achieving single stage power conversion with both regulated input current and regulated output voltage processing a minimum of load power and thereby achieving higher efficiency than other singles stage power converters with both regulated input current and regulated output voltage and two stage power factor corrected power converters. The subject invention reveals power factor corrected converters that improve the efficiency of the single stage power factor corrected converters on which they are based by adding an auxiliary converter that processes a small fraction of the total load power.

A method for controlling a resonance type power converter including a first resonance circuit (L.sub.0, C.sub.0) and a shunt circuit (3), which converts and outputs the power of the DC power supply, shunting a current flowing into a first capacitor (C.sub.S) by controlling a second switching element (S.sub.2) during a predetermined period within turn-off period of a first switching element (S.sub.1), the first capacitor connected in parallel to the first switching element (S.sub.1), the second switching element (S.sub.2) included in the shunt circuit (3), and the first switching element (S.sub.1) operated in response to the resonance of the first resonance circuit (L.sub.0, C.sub.0).