A thermal increase system includes a cavity, a first electrode disposed in the cavity, a second electrode disposed in the cavity, and a self-oscillator circuit that produces a radio frequency signal that is converted into electromagnetic energy that is radiated into the cavity by the first and second electrodes. The self-oscillating circuit includes the first electrode and the second electrode. In an embodiment, the first electrode is a first plate in a capacitor structure and the second electrode is a second plate in the capacitor structure. The cavity and a load contained within the cavity operates as a capacitor dielectric of the capacitor structure. A resonant frequency of the self-oscillator circuit is at least partially determined by a capacitance value of the capacitor structure.

A control method of controlling a resonance type power conversion device including a voltage resonance circuit is provided. The voltage resonance circuit comprising, a choke coil connected to input power supply, a first switching element connected to the choke coil, a capacitor connected in parallel to the first switching element, and a resonance circuit connected between a connection point and an output terminal, the connection point being a point at which the choke coil and the first switching element are connected. The control method comprising, detecting a polarity of current flowing through parallel circuit connected in parallel to the first switching element by using a sensor included in the voltage resonance circuit; and controlling an operating condition of the first switching element depending on a polarity of the current detected by the sensor.

A switching power supply apparatus includes a switching circuit, a resonance circuit, a rectifying circuit, and a control circuit. The switching circuit includes switching elements connected in series between input terminals of a source. The resonance circuit includes an excitation inductor of a primary winding of a transformer, a resonance inductor connected in series with the excitation inductor, and a variable resonance capacitor which is connected in series with the excitation inductor and whose electrostatic capacity changes according to a control voltage. The control circuit generates, on the basis of a feedback voltage, switching signals in which frequency diffusion is given to a switching frequency and the control voltage and outputs the switching signals and the control voltage to simultaneously change the switching frequency and the electrostatic capacity of the variable resonance capacitor.

A power conversion system for an aircraft on-board power system converts high voltage DC to low voltage DC and vice versa. The system includes switching means configured so that the system operates in a plurality of configurations, each forming an isolated DC/DC converter.

A power supply that supplies power to a capacitive load comprises: a converter; an inverter; a resonant transformer; a detector configured to detect output frequency or output current and output voltage; and a controller configured to control the inverter, wherein the controller is configured to: calculate output power; adjust the output frequency within a predetermined frequency search range, adjust the output voltage within a predetermined voltage search range, and specify, as a frequency target value, a minimum value of the output frequency with which the output power reaches predetermined output power; and control the inverter so that the output frequency will be the frequency target value, adjust the output voltage within the predetermined voltage search range, and specify, as a voltage target value, a value of the output voltage with which the output power is target output power.

An inductive power transmitter comprising: at least two switching elements connected across a resonant circuit, the resonant circuit including an inductance and a capacitance; wherein the transmitter is configured to adjust the value of the capacitance based on a desired operating frequency.

A contactless power supply device that supplies electric power to a vehicle in a contactless manner, includes: a power transmission resonance circuit; a power source circuit supplying direct-current power; and a power transmission circuit converting the direct-current power of the power source circuit into alternating-current power and supplying alternating-current power to the power transmission resonance circuit. The power transmission circuit includes: an inverter circuit converting the direct-current power of the power source circuit into alternating-current power; and a power transmission-side immittance conversion circuit adjusting the alternating-current power of the inverter circuit and supplies the adjusted alternating-current power to the power transmission resonance circuit. The ratio of a characteristic impedance of the power transmission-side immittance conversion circuit to an impedance backward on the power transmission resonance circuit side from the power transmission-side immittance conversion circuit is adjusted such that harmonic components in the alternating-current power of the inverter circuit becomes lessened.

Provided are methods and circuits for a resonant converter comprising at least one switch-controlled capacitor, wherein the at least one switch-controlled capacitor controls a resonant frequency of the resonant tank circuit. Provided are constant and variable switching frequency embodiments, and full-wave and half-wave switch-controlled capacitor embodiments. Also provided are interleaved resonant converters based on constant and variable switching frequency, and full-wave and half-wave switch-controlled capacitor resonant converter embodiments. Interleaved embodiments overcome load sharing problems associated with prior interleaved resonant converters and enable phase shedding to improve light load efficiency.

A quasi-resonant auto-tuning controller includes a zero-voltage crossing detection circuit and a valley tuning finite-state machine having a look-up table. The zero-voltage crossing detection circuit receives a reference voltage and receives an auxiliary signal from an auxiliary winding. The zero-voltage crossing detection circuit produces a comparison signal having pulses when the auxiliary signal is less than the reference voltage. The valley tuning finite-state machine produces a divided pulse width based on the comparison signal, stores the divided pulse width of each pulse in the look-up table, determines, from the comparison signal, that the auxiliary signal is less than the reference voltage, waits a time period corresponding to the divided pulse width stored in the look-up table if the auxiliary signal is less than the reference voltage, and produces a valley point signal after waiting the time period.

A direct current (DC) to DC power converter includes a first converter for converting a first DC bus voltage into a first high frequency AC voltage and a second converter for converting a second high frequency alternating current (AC) voltage into a second DC bus voltage. The DC to DC converter also includes a resonant circuit for coupling the first bus converter and the second bus converter and a controller for providing switching signals to the first converter and the second converter to operate the power converter in a soft switching mode. The resonant circuit includes a high frequency transformer coupled between the first converter and the second converter and an auxiliary converter coupled in series with a first resonant inductor and the high frequency transformer. The resonant circuit further includes second inductor coupled across a first winding of the high frequency transformer. An auxiliary voltage generated by auxiliary converter is added in series with an output voltage of the first converter.