Static power conversion method and apparatus having essentially zero switching losses and clamped voltage levels

A power converter for converting DC power to AC power comprising:

• (a) a resonant circuit having an inductor adapted to receive a DC power input, a capacitor connected to the inductor, and a DC bus providing the output voltage from the resonant circuit;
• (b) means for causing the resonant circuit to oscillate stably at or below its resonant frequency and for the voltage across the DC bus to be maintained at an average DC level and to go to zero voltage at least once during each cycle of oscillation of the resonant circuit;
• (c) an inverter connected to receive the voltage on the DC bus and having gated switching devices which are switched on and off only when the voltage on the DC bus is substantially zero;
• and
• (d) clamping means for limiting the voltage across the DC bus to a selected maximum level.

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 an 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;
• and
• (d) clamping means for limiting the voltage across the DC bus to a selected maximum level.

A power converter comprising:

• (a) power supply means for providing DC output power;
• (b) a resonant circuit having an inductor and a capacitor connected together to receive the DC power from the power supply means and to provide direct current voltage to a DC bus;
• (c) means for causing the resonant circuit to oscillate stably at or below its resonant frequency such that the voltage on the DC bus goes to zero at least once during each cycle of oscillation of the resonant circuit;
• (d) an inverter connected to receive the voltage on the DC bus and having gated switching devices which are switched on and off only when the voltage provided on the DC bus is substantially zero;
• and
• (e) clamping means for limiting the voltage across the DC bus to a selected maximum level.

A power converter comprising:

• (a) power supply means for receiving AC power at a first frequency and providing DC output power;
• (b) a resonant circuit having an inductor and a capacitor connected together to receive the DC power from the power supply means and to provide direct current voltage to a DC bus;
• (c) means for causing the resonant circuit to oscillate stably at or below its resonant frequency at a second frequency substantially higher than the first frequency such that the voltage on the DC bus goes to zero at least once during each cycle of oscillation of the resonant circuit;
• (d) an inverter connected to receive the voltage on the DC bus and having switching devices which are switched only when the voltage provided on the DC bus is substantially zero to provide AC output power at a third frequency which is substantially lower than the second frequency;
• and
• (e) clamping means for limiting the voltage across the DC bus to a selected maximum level.