A DC-to-DC converter includes a first DC side, a second DC side, a first capacitor, a first switch circuit, a magnetic element circuit, a second switch circuit, and a second capacitor. The DC-to-DC converter is adapted for converting between a first DC voltage and a second DC voltage. The magnetic element circuit is electrically coupled to the first switch circuit, and includes a plurality of magnetically coupled windings and an inductor. An oscillating current flowing in the first switch circuit is generated by controlling the first switch circuit and the second switch circuit, and an oscillating frequency of the oscillating current is determined by the capacitance of the first capacitor and the inductance of the inductor in the magnetic element circuit, and the first switch circuit and the second switch circuit are switched at a specific region of a wave trough of the oscillating current.

A hybrid power conversion circuit includes a high-side switch, a low-side switch, a transformer, a resonance tank, a first switch, a second switch, a first synchronous rectification switch, a second synchronous rectification switch, and a third switch. The resonance tank has an external inductor, an external capacitance, and an internal inductor. The first switch is connected to the external inductor. The second switch and a first capacitance form a series-connected path, and is connected to the external capacitance. The first and second synchronous rectification switches are respectively coupled to a first winding and a second winding. The third switch is connected to the second synchronous rectification switch. When an output voltage is less than a voltage interval, the hybrid power conversion circuit operates in a hybrid flyback conversion mode, and otherwise the hybrid power conversion circuit operates in a resonance conversion mode.

Some embodiments of the invention include a pre-pulse switching system. The pre-pulsing switching system may include: a power source configured to provide a voltage greater than 100 V; a pre-pulse switch coupled with the power source and configured to provide a pre-pulse having a pulse width of T.sub.pp; and a main switch coupled with the power source and configured to provide a main pulse such that an output pulse comprises a single pulse with negligible ringing. The pre-pulse may be provided to a load by closing the pre-pulse switch while the main switch is open. The main pulse may be provided to the load by closing the main switch after a delay T.sub.delay after the pre-pulse switch has been opened.

Some embodiments of the invention include a pre-pulse switching system. The pre-pulsing switching system may include: a power source configured to provide a voltage greater than 100 V; a pre-pulse switch coupled with the power source and configured to provide a pre-pulse having a pulse width of T.sub.pp; and a main switch coupled with the power source and configured to provide a main pulse such that an output pulse comprises a single pulse with negligible ringing. The pre-pulse may be provided to a load by closing the pre-pulse switch while the main switch is open. The main pulse may be provided to the load by closing the main switch after a delay T.sub.delay after the pre-pulse switch has been opened.

A converter includes an input capacitor, a primary-side switch circuit, a magnetic element circuit, a secondary-side switch circuit, and an output capacitor. The magnetic element circuit includes a transformer and an inductor. The input capacitor is configured to receive an input voltage. The primary-side switch circuit is coupled to the input capacitor. The magnetic element circuit is coupled to the primary-side switch circuit. The inductor is a leakage inductor of the transformer or an external inductor coupled between the transformer and the primary-side switch circuit. The secondary-side switch circuit is coupled to the magnetic element circuit. The output capacitor is coupled to the secondary-side switch circuit. The input capacitor and the inductor generate an oscillating current. The primary-side switch circuit is switched at an adjacent region of a wave trough of the oscillating current.

Some embodiments of the invention include a pre-pulse switching system. The pre-pulsing switching system may include: a power source configured to provide a voltage greater than 100 V; a pre-pulse switch coupled with the power source and configured to provide a pre-pulse having a pulse width of T.sub.pp; and a main switch coupled with the power source and configured to provide a main pulse such that an output pulse comprises a single pulse with negligible ringing. The pre-pulse may be provided to a load by closing the pre-pulse switch while the main switch is open. The main pulse may be provided to the load by closing the main switch after a delay T.sub.delay after the pre-pulse switch has been opened.

Some embodiments of the invention include a pre-pulse switching system. The pre-pulsing switching system may include: a power source configured to provide a voltage greater than 100 V; a pre-pulse switch coupled with the power source and configured to provide a pre-pulse having a pulse width of T.sub.pp; and a main switch coupled with the power source and configured to provide a main pulse such that an output pulse comprises a single pulse with negligible ringing. The pre-pulse may be provided to a load by closing the pre-pulse switch while the main switch is open. The main pulse may be provided to the load by closing the main switch after a delay T.sub.delay after the pre-pulse switch has been opened.

A power conversion device includes an input detector for detecting input parameters of the DC input to the inverter; an output detector for detecting output parameters of the DC output from the power converter device; a duty calculator for calculating a duty for the switching elements of the inverter; a frequency search range calculator for determining an upper limit and a lower limit of a frequency search range for determining the drive frequency after the operating condition is changed, using at least one parameter of the input parameters, the output parameters, and a duty parameter; and a frequency search processor for determining the drive frequency by searching the frequency search range.

A method for charging a battery of a vehicle uses a battery charging station that provides an electric current at a first DC voltage. The electric current that is output by the battery charging station at the first DC voltage is supplied to a charger of the vehicle, The electric current at the first DC voltage is converted within the charger into a second electric current at a second DC voltage that is required for charging the battery of the vehicle, and then is supplied to the battery.

A first DC-DC conversion circuit and a second DC-DC conversion circuit, which are connected in parallel to one casing, are caused to operate independently of each other, whereby even in the event that a semiconductor switching element which configures either the first or second DC-DC conversion circuit fails, only a DC-DC conversion circuit which carries out a normal operation is caused to operate, thereby carrying out the continuation of power supply of a power conversion device.