High-efficiency fully soft-switching single-stage three-level (SS-3) power amplifier

A circuit for use as a single-stage three-level power amplifier or a single-stage three-level inverter or DC/AC converter, the circuit having a first and a second terminals, the circuit comprising:

• a power supply sub-circuit coupled to and between the first and second terminals, the power supply configured to supply DC power;
• a high-frequency transformer having a primary winding center-tapped with a center-tap thereof, the primary winding having an upper terminal and a lower terminal, the transformer further having a secondary winding center-tapped with a center-tap thereof coupled to the ground, the secondary winding having an upper terminal and a lower terminal;
• a first full-bridge sub-circuit coupled to and between the first and second terminals and configured to receive DC power from the power supply sub-circuit, the first full-bridge sub-circuit having two switching legs both coupled to and between the first and second terminals, each said switching leg having two semiconductor switching devices coupled in series with each other via a respective junction point there-between, the two respective junction points of the two switching legs coupled to the respective upper and lower terminals of the primary winding, the first full-bridge sub-circuit configured to receive modulated switching driving signals modulated with an input signal and use received modulated switching driving signals to drive the semiconductor switching devices to generate, at the respective junction points of the two switching legs, high-frequency switching transformer-driving signals adapted to drive the primary winding through the upper and lower terminals of the primary winding to produce two amplified three-level modulated signals respectively at the upper and lower terminals of the secondary winding;
• a primary-side passive auxiliary network sub-circuit coupled to the first and second terminals and coupled to the center-tap of the primary winding, the primary-side passive auxiliary network sub-circuit comprising:
• a capacitive voltage divider sub-circuit coupled between the first and second terminals and having a first and a second capacitors coupled in series with each other via a voltage divider junction point;
• and
• an auxiliary inductor coupled between the voltage divider junction point and the center-tap of the primary winding;
• and
• wherein the primary-side passive auxiliary network sub-circuit is configured, through the capacitive voltage divider sub-circuit and the auxiliary inductor, to provide reactive current for the respective semiconductor switching devices of the switching legs so that the respective semiconductor switching devices of the switching legs achieve ZVS during respective switching operations.