An energy efficient apparatus includes a switching device, a frequency dependent reactive device, and a control element is provided. The switching device is coupled to a source of electrical power and includes a pair of transistors and is adapted to receive a control signal and to produce an alternating current power signal. The frequency of the alternating current power signal is responsive to the control signal. The frequency dependent reactive device is electrically coupled to the pair of transistors for receiving the alternating current power signal and producing an output power signal. The frequency dependent reactive device is chosen to achieve a desired voltage of the output power signal relative to the frequency of the alternating current power signal. The control element senses an actual voltage of the direct current power signal and modifies the control signal delivered to achieve the desired voltage of the direct current power signal.

An energy efficient apparatus includes a switching device, a frequency dependent reactive device, and a control element is provided. The switching device is coupled to a source of electrical power and includes a pair of transistors and is adapted to receive a control signal and to produce an alternating current power signal. The frequency of the alternating current power signal is responsive to the control signal. The frequency dependent reactive device is electrically coupled to the pair of transistors for receiving the alternating current power signal and producing an output power signal. The frequency dependent reactive device is chosen to achieve a desired voltage of the output power signal relative to the frequency of the alternating current power signal. The control element senses an actual voltage of the direct current power signal and modifies the control signal delivered to achieve the desired voltage of the direct current power signal.

A wireless power transfer apparatus has a resonant circuit electrically coupled to a power converter. The resonant circuit includes a magnetic coupler L.sub.pt for magnetic coupling with a second apparatus. A controller associated with the power converter is configured to vary a relative phase of operation of the power converter with respect to the second apparatus, the phase being varied to at least partially compensate for variations in a resonant frequency of the resonant circuit.

A holdup circuit includes a high-voltage generation circuit that outputs a high voltage and a holdup capacitor charging/discharging circuit that includes a holdup capacitor that is charged by the high voltage output by the high-voltage generation circuit. An inrush control circuit includes a constant-current source that includes a first transistor and a second transistor. During start-up, input current flows through the second transistor, and after start-up and during normal operation, the input current flows through the first transistor.

A power conversion device includes a power conversion circuit having first, second, third, and fourth switches, and a controller. The controller generates a first pulse signal for controlling the turning on and off of the first and fourth switches and a second pulse signal for controlling the turning on and off of the second and third switches, based on a circuit current flowing in the power conversion circuit and a voltage of an AC power source. The turning on and off of the switches causes the power conversion device to have a flowing current in which a high frequency component is mixed with a low frequency component.

A power switching converter includes a switch coupled to an input terminal through a primary winding of a transformer and a control circuit configured to drive the switch to provide a regulated output signal at a secondary winding of the transformer. A wake up circuit is provided to force the switching-on of the switch when the power converter enters in a burst mode. The wake up circuit includes a transmitting section coupled to the secondary winding and a receiving section coupled to an auxiliary winding of the transformer and the control circuit. The transmitting section is configured to provide a wake up signal communicated in a wireless manner to the receiving section when the output signal falls below a threshold value.

An isolated power conversion apparatus has an isolation transformer, a series circuit including a load and an inductor connected in series with each other, the series circuit being disposed on a secondary side of the isolation transformer, and one or a plurality of switching means disposed between the series circuit and the secondary side of the isolation transformer, the switching means being bidirectional. This apparatus sends out power from a DC power supply of a primary side of the isolation transformer toward the load as DC power or AC power of an arbitrary polarity, or regenerates and supplies the DC power or AC power from the load to the DC power supply.

An isolated power conversion apparatus has an isolation transformer, a series circuit including a load and an inductor connected in series with each other, the series circuit being disposed on a secondary side of the isolation transformer, and one or a plurality of switching means disposed between the series circuit and the secondary side of the isolation transformer, the switching means being bidirectional. This apparatus sends out power from a DC power supply of a primary side of the isolation transformer toward the load as DC power or AC power of an arbitrary polarity, or regenerates and supplies the DC power or AC power from the load to the DC power supply.

A multiple parallel-connected resonant converter, an inductor-integrated magnetic element and a transformer-integrated magnetic element are provided. The multiple parallel-connected resonant converter includes a first and a second converters. The first converter having a first input and output end includes a first inductor, a first transformer and a first capacitor connected in series. The second converter having a second input and output end includes a second inductor, a second transformer and a second capacitor connected in series. The second output end is connected with the first output end in parallel. The first and second inductor are integrated in a first magnetic element, the first magnetic element includes a first and second side column, and a first and second central column. The first inductor includes a first coil positioned around the first central column and the second inductor includes a second coil positioned around the second central column.

According to one aspect, embodiments herein provide an AC-DC converter comprising a rectifier, a capacitor, a DC bus coupled to the capacitor, a plurality of first switches coupled to the DC bus, a plurality of second switches coupled between the rectifier and the first switches, a transformer having a primary winding and a secondary winding, the primary winding coupled to the plurality of first switches, the plurality of second switches, and the rectifier, and the secondary winding coupled to an output, and a controller configured, in response to a determination that the input AC power is acceptable, to operate the plurality of second switches and the plurality of first switches such that output DC voltage is maintained at a desired output DC voltage level, and operate the plurality of first switches such that a DC bus voltage on the DC bus is maintained at a desired DC bus voltage level.