In an example, a system includes a single-output flyback/LLC converter adapted to be coupled to an alternating current (AC) power supply. The system also includes a buck regulator coupled to the single-output flyback/LLC converter. The system includes a first LED including an anode coupled to the single-output flyback/LLC converter and a cathode coupled to the buck regulator. The system also includes a second LED including an anode coupled to the single-output flyback/LLC converter and a cathode coupled to a ground terminal.

Disclosed are a novel zero-voltage switching control circuit and a control method. By a chip of a controller, a first switch unit is controlled to switch on-off of an input winding and a second switch unit is controlled to switch on-off between an auxiliary winding and a negative voltage level, wherein before the input winding is conducted, the auxiliary winding of a voltage converter is conducted with the negative voltage level in advance, and the input winding is forced to generates a negative current based on a coupling effect between the input winding and auxiliary winding, to release the energy of parasitic capacitance in the first switch unit cross voltages, so as to further enable a polarity inversion of the input winding, and the first switch unit cross-voltage decays to an expected low switching potential level. The invention can achieve the zero-voltage switching under a Continuous Conduction Mode (CCM) and a Dis-continuous Conduction Mode (DCM) to reduce the power consumption in switching of first electronic switch, and also in the embodiment of a Flyback converter, it separates the primary current and secondary current from each other that are originally with short overlap under the cross-over transition in CCM operation, so as to avoid a cross-conduction happens as well as to reduce the obstacle in controlling secondary side synchronous rectification.

A flyback DC-DC converter. The converter having a transformer with a primary and a secondary windings, first and second switches, a capacitor coupled between the second switch and the primary winding, where the second switch is arranged to operate such that a sum of a first and second time periods equals a sum of third and fourth time periods, where the first time period is a delay time period from a time that the first switch is turned off to a time that the second switch is turned on, the second time period is a time period that the second switch is on, the third time period is a resonance time period of a resonator formed by a leakage inductance of the transformer and a capacitance of the capacitor, and the fourth time period is a time period for discharge of the leakage inductance of the transformer into the capacitor.

A switching power circuit for charging a battery can include: four switches extending between two ports of a low-frequency AC input voltage and an energy storage circuit, where the energy storage circuit and a primary winding of a transformer are coupled between first and second nodes, the first node is a common node of the first and second switches, and the second node is a common node of the third and fourth switches; a rectification circuit having an input terminal coupled to a secondary winding of the transformer; a DC-DC converter having an input terminal coupled to an output terminal of the rectification circuit, and generates a charging current; and a control circuit that adjusts the charging current by controlling an operation of the DC-DC converter according to a charging requirement, in order to make an average value of the charging current meet the charging requirement.

A power converter is provided. The power converter includes an LLC converter, a feedback circuit, a first driving circuit, and a second driving circuit. The LLC converter includes a first arm transistor group and a second arm transistor group. The feedback circuit provides a feedback signal corresponding to a current value of the LLC converter. The first driving circuit drives the first arm transistor group in response to the feedback signal and provides a control signal. The second driving circuit drives the second arm transistor group in response to the control signal.

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.

Systems and methods for providing a constant current controller for use in constant current welding applications are described. In one embodiment, a current controller controls the output current of the welding torch without directly measuring the output current of the welding torch. The current controller controls or sets a current in a primary winding of a transformer in an inverter of a welding power supply to control the output current of the welding torch.

An isolated converter includes an input circuit, a transformer, a first switch, a second switch and a snubber circuit. The input circuit includes at least two input capacitors, and is configured to provide an input voltage. A divider node is arranged between the at least two input capacitors. The transformer includes a primary winding and a secondary winding to generate an output voltage on the secondary winding according to the input voltage. The primary winding of the transformer is electrically connected between the first switch and the second switch. The snubber circuit is electrically connected between the first switch and the second switch, and forms a discharge path with the primary winding. The snubber circuit is configured to receive a reflected voltage from the secondary winding back to the primary winding, and the divider node is connected to the discharge path.

A power converter, includes: a first line to which a first voltage is applied; a second line to which a second voltage lower than the first voltage is applied; a third line to which a third voltage lower than the second voltage is applied; a first bridge circuit that is provided between the first line and the second line, the first bridge circuit including a plurality of first switching elements; a second bridge circuit that is provided between the second line and the third line, the second bridge circuit including a plurality of second switching elements; and a voltage output circuit configured to generate a predetermined direct current (DC) voltage based on operations of the first and second bridge circuits.

Power converters with power factor correction circuits and controllers thereof that are configured to generate frequency-adjustable first and second pulsed signals having respective and complementary phases separated by an adjustable deadtime. For example, a power converter may be configured to receive an alternating current (AC) input signal and output a direct current (DC) output signal. The power converter may include at least one DC/DC converter and a power factor correction circuit. The power factor correction circuit may include a first switching transistor comprising a first gate; a second switching transistor in series with the first switching transistor and comprising a second gate; and a controller configured to generate first and second pulsed signals having respective and complementary phases and separated by an adjustable deadtime and apply the generated first and second pulsed signals to the first and second gates, respectively.