A main circuit of a power conversion device includes: an AC/DC converter for performing power factor correction control for a single-phase AC power supply; and a DC/DC converter connected to the AC/DC converter via a DC capacitor. In order to reduce ripple voltage and ripple current for the DC capacitor, a control circuit superimposes, onto a DC current command, an AC current command having the minimum value at the zero cross phase of the single-phase AC power supply and having the maximum value at the peak phase thereof, to generate an output current command for the DC/DC converter, and performs output control for the DC/DC converter, using the output current command.

A zero-crossing detection circuit can include: a state judging circuit that generates a judging signal based on whether a body diode of a synchronous power switch is conducting when the synchronous power switch is off; a regulation voltage generator that reduces a regulation voltage when the judging signal indicates that the body diode is conducting, and increases the regulation voltage when the judging signal indicates that the body diode is not conducting, where a detection voltage includes a sum of the regulation voltage and a voltage at a first terminal of the synchronous power switch; and a comparison circuit that compares the detection voltage against a voltage at a second terminal of the synchronous power switch, and generates a zero-crossing detection signal that is activated to turn off the synchronous power switch when the detection voltage equals the voltage at the second terminal of the synchronous power switch.

In a power converter, switch-off of the synchronous rectification switch while the auxiliary switch is on causes the first capacitance of the main switch and the second capacitance of the synchronous rectification switch to resonate with the inductance of the second magnetic component. A parameter obtainer detects a voltage across a selected one of the main switch and the synchronous rectification switch, and obtains a parameter indicative of a corresponding one of rising and falling waveforms of the voltage across the selected switch while the selected switch is switched. A controller controls a switching control signal for the auxiliary switch to adjust switch-on timing of the auxiliary switch as a function of the parameter obtained by the parameter obtainer.

A zero-crossing detection circuit includes a zero-crossing detection unit arranged to compare a first monitoring target signal and a second monitoring target signal respectively input through diodes from a first node and a second node between which an AC signal is applied, so as to generate a first comparison signal, and a logic unit arranged to estimate a zero cross of the AC signal from the first comparison signal so as to generate a zero-crossing detection signal. The zero-crossing detection circuit preferably includes a monitoring unit arranged to adjust the first monitoring target signal and the second monitoring target signal to be suitable for input to the zero-crossing detection unit. The logic unit preferably counts a period of the first comparison signal and estimates a zero cross of the AC signal using a count value thereof.

A power supply comprising a transformer unit for transforming an AC voltage and AC current input on a primary side of the transformer unit into an AC voltage and AC current for supplying a load connectable to a secondary side of the transformer unit, a controllable switch controlled by a switch signal, and a processing unit. The processing unit is configured to generate the control signal based on a zero crossing information signal, further based on a set output voltage and/or a set output current, and further based on an actual output voltage and/or an actual output current.

An apparatus includes a first power converter and a second power converter. The first power converter converts an input voltage into a first output voltage; the second power converter converts the first output voltage into a second output voltage that powers a load. The second power converter includes a switched-capacitor converter combined with a magnetic device. The switched-capacitor converter provides capacitive energy transfer; the magnetic device provides magnetic energy transfer. Additionally, the second power converter provides unregulated conversion of the first output voltage into the second output voltage via the capacitive energy transfer and the magnetic energy transfer. To maintain the magnitude of the second output voltage within a desired range or setpoint value, the first power converter regulates a magnitude of the first output voltage based on comparison of a magnitude of the second output voltage with respect to a desired setpoint reference voltage.

A load control device for controlling power delivered from an alternating-current power source to an electrical load may comprise a controllably conductive device, a control circuit, and an overcurrent protection circuit that is configured to be disabled when the controllably conductive device is non-conductive. The control circuit may be configured to control the controllably conductive device to be non-conductive at the beginning of each half-cycle of the AC power source and to render the controllably conductive device conductive at a firing time during each half-cycle (e.g., using a forward phase-control dimming technique). The overcurrent protection circuit may be configured to render the controllably conductive device non-conductive in the event of an overcurrent condition in the controllably conductive device. The overcurrent protection circuit may be disabled when the controllably conductive device is non-conductive and enabled after the firing time when the controllably conductive device is rendered conductive during each half-cycle.

The present disclosure relates to a totem pole bridgeless power factor correction device and a power supply system. The device includes a power factor correction module. The power factor correction module includes a first transistor, a second transistor, a third transistor, a fourth transistor, an inductor and a control module for generating a zeroth control signal in the first time period to control the third transistor and the fourth transistor to be in an off state, performing a zero-crossing detection on an AC voltage in the first time period, generating a first control signal to control a conduction state of the first transistor and the second transistor before the AC voltage crosses zero, and generating a second control signal to control the conduction state of the first transistor and the second transistor after the AC voltage crosses zero. The embodiments of the present disclosure can enable the device to smoothly transition the current when the device is at the zero-crossing point, and improve the stability and efficiency of the device.

A zero current detection system for a switching regulator is provided. The switching includes an inductor. In the zero current detection system, a comparator has a positive input coupled to a terminal of the inductor and an output terminal for outputting a comparison result signal; a first signal latch circuit has a clock terminal for receiving the comparison result signal and outputting a latched output signal; a delay line module starts counting upon receipt of the latched output signal, and then outputs a zero current detection signal after counting a delay time; in response to the zero current detection signal, a voltage sampling module samples a node voltage at two different time points, to generate two sampling voltages; a delay control module adjusts the delay time of the delay line module according to the two sampling voltages.

A power conversion circuit and a method thereof, wherein the power conversion circuit includes a first grid interface and a second grid interface coupled to an AC power source, a power harvesting module, a sampling module and a switching module. The power harvesting module is coupled to the first grid interface, and the power harvesting module includes a first diode and a first charging capacitor coupled to the first diode. The power harvesting module receives the AC power source from the first grid interface to generate an output voltage. The switching module includes a switch component controlled by the sampling module. The sampling module is coupled to the power harvesting module and acquires a sampling voltage. The sampling module controls the switch component to be turned off during at least a period of time within positive half cycles of the AC power source.