Static power conversion and apparatus having essentially zero switching losses

A method of maintaining stable oscillations in a resonant circuit composed of an inductor receiving uni-directional power and a capacitor connected to the inductor, wherein the resonant circuit is connected to an inverter having gate turn off switching devices such that the output voltage from the resonant circuit is provided to the inverter, comprising the steps of:

• (a) shunting the current from the inductor around the capacitor and then opening the shunt to allow the current from the inductor to flow into the capacitor and into the inverter, the capacitor being shunted for a period of time sufficient to build up sufficient current in the inductor such that, when the shunt is removed, the voltage across the capacitor will be driven to zero at the end of one resonant cycle;
• and
• (b) switching the switching devices of the inverter on and off only at times of substantially zero voltage provided from the resonant circuit to the inventor.

A resonant DC power supply comprising:

• (a) a converter including pairs of gate turn off switching devices connected in a bridge configuration to receive AC power from an AC power system and to be switched to rectify the AC power to uni-directional power at an output and including inductance connected between the AC power system input lines and its uni-directional output;
• (b) a resonant circuit having an inductor and a capacitor connected together, the resonant circuit connected to the output of the bridge converter switching devices, and an additional power supply capacitor connected in series with the inductor, and including a DC output bus connected to the resonant circuit;
• (c) means for causing the resonant circuit to oscillate stably at or below its resonant frequency such that the voltage across the DC output bus goes to zero voltage at least once during each cycle of oscillation and such that a average voltage is maintained across the power supply capacitor and across the DC bus, and wherein the switching devices in the converter are controlled to switch at times of zero voltage across the DC bus.

A resonant DC power supply comprising:

• (a) a converter including a pairs of switching devices connected in a bridge configuration to receive AC power from an AC power system and to be switched to rectify the AC power to uni-directional power at an output and including inductance connected between the AC power system input lines and its uni-directional output;
• (b) a resonant circuit having an inductor and a capacitor connected together, the resonant circuit connected to the output of the bridge converter switching devices and an additional power supply capacitor connected in series with the inductor, and including a DC output bus connected to the resonant circuit;
• (c) means for causing the resonant circuit to oscillate stably at or below its resonant frequency such that the voltage across the DC output bus goes to zero voltage at least once during each cycle of oscillation and such that an average voltage is maintained across the power supply capacitor and across the DC bus, wherein the means for causing the resonant circuit to oscillate includes a switching device connected across the DC bus and means for controlling the switching of the switching device to switch at times of zero voltage across the DC bus to maintain steady oscillations in the resonant circuit.

A resonant DC power supply comprising:

• (a) a converter including pairs of switching devices connected in a bridge configuration to receive AC power from an AC power system and to be switched to rectify the AC power to uni-directional power at an output and including inductance connected between the AC power system input lines and its uni-directional output;
• (b) a resonant circuit having an inductor and a capacitor connected together, the resonant circuit connected to the output of the bridge converter switching devices and an additional power supply capacitor connected in series with the inductor, and including a DC output bus connected to the resonant circuit;
• (c) means for causing the resonant circuit to oscillate stably at or below its resonant frequency such that the voltage across the DC output bus goes to zero voltage at least once during each cycle of oscillations and such that an average voltage is maintained across the power supply capacitor and across the DC bus, wherein the means for causing the resonant circuit to oscillate includes pairs of switching devices connected across the DC bus to maintain steady oscillations in the resonant circuit.

A power converter adapted to convert input power which is at a first frequency, comprising:

• (a) means for receiving the input power at a first frequency and for providing a uni-directional output voltage on a DC bus which cyclically reaches zero voltage at a second frequency which is substantially higher than the first frequency, wherein the means receiving power includes a resonant circuit having an inductor and a capacitor connected together, converter means receiving the input power at the first frequency for rectifying the input power and providing the rectified power to the resonant circuit, and further including means for causing the resonant circuit to oscillate stably at the second frequency such that the voltage across the DC bus goes to zero voltage at least once during each cycle of oscillation;
• and
• (b) inverter means, connected to receive the power from the DC bus and having switching devices therein, for converting the DC power from the DC bus to AC power at a third frequency which is substantially lower than the second frequency, the switching devices in the inverter means being switched only when the voltage at the DC bus is substantially at zero volts.