Switching power supply apparatus

A power conversion apparatus comprising a power switching branch which is configured to operate on input power to produce converted power by power switching operations, a power output portion for outputting the converted power, and a clamper circuit;

• wherein the power switching branch comprises a power inductor and a semiconductor switch which are connected in series;
• wherein the semiconductor switch is configured to switch between a power output state and a non-power output state at a switching frequency to perform the power switching operations;
• and wherein the clamper circuit is configured to output energy which is built-up or stored on a parasitic reactive element or parasitic reactive elements during a non-power output cycle to the power output portion in a power output cycle immediately following the non-power output state;
• wherein the semiconductor switch comprises a first terminal and a second terminal and is operable in an on-state or an off-state;
• wherein a low impedance current conductive path is formed between the first terminal and the second terminal when in the on-state and a high impedance current blocking path is formed between the first terminal and the second terminal when in the off-state;
• and wherein the clamper circuit comprise a first terminal and a second terminal which are electrically connected with the first and second terminals of the semiconductor switch.

A power conversion circuit comprising an electronic power switch, a power output circuit comprising a power output terminal, a first power supply rail and a second power supper rail, wherein the power switch comprises a switch first terminal, a switch second terminal which is connected to the second power rail and a switch third terminal which is a switching terminal, wherein the power switch is switchable by a train of switching pulses between an on-state during which current is to flow from the switch first terminal to the switch second terminal and an off-state during which flow of current between the switch first terminal and switch second terminal is impeded or blocked;

• wherein the output circuit comprises an inductor having an inductor first terminal which is connected to the first power supply rail and an inductor second terminal which is connected to the power switch first terminal, a capacitor having a capacitor first terminal which is connected to the first power supply rail and a capacitor second terminal which is connected to the output terminal of the power output circuit, and a diode having diode forward direction, a diode first terminal which is connected to the inductor second terminal and a diode second terminal which is connected to the output terminal;
• wherein the output circuit comprises an auxiliary electronic switch which is in parallel connection with the output diode and which is switchable between an on-state during which an auxiliary current path permitting a flow of auxiliary current in a reverse direction opposite to the diode forward direction is formed and an off-state during which the auxiliary current path is blocked or impeded;
• and wherein, during power conversion operations and during an off-cycle of the main power switch, the auxiliary electronic switch is to be turned on to permit a continuation of current to flow in the inductor after a forward current flowing to the output terminal through the inductor and the output diode has fallen to zero and to remain turned on for an on-duration to facilitate a reverse current flow through the auxiliary electronic switch, wherein the on-duration is set to cause discharge of parasitic charges stored on the main power switch when the main power switch is in an off-state.