High side switching circuit

Abstract

A high side switching circuit, comprising: a switching transistor; a charge pump drive circuit including a circuit for generating an oscillating signal; and a charge pump arranged to provide a gate drive voltage to the switching transistor in response to a control signal; wherein the charge pump is driven by the charge pump drive circuit, and the circuit for generating an oscillating signal comprises: an oscillator having a power supply input and first and second outputs, outputting first and second pulse trains respectively of the same frequency but out of phase such that when the first pulse train is high, the second pulse train is low and when the second pulse train is high, the first pulse train is low; first and second transistors connected in series with the drain of the first transistor connected to a high voltage input relative to the high level of the first and second pulse train pulses, the source of the first transistor connected to the drain of the second transistor, the source of the second transistor connected to a voltage input less than or equal to the low level of the first and second pulse train pulses, the gate of the first transistor being connected to the first output of the oscillator and the gate of the second transistor being connected to the second output of the oscillator; and an output terminal connected to the source of the first transistor thereby outputting a third pulse train in phase with the first pulse train and providing a current derived from the drain of the first transistor when the first transistor is conducting and sinking a current when the second transistor is conducting; and wherein the switching transistor and first transistor are vertical MOSFETs or IGBTs, said switching and first transistors being provided on a semiconductor substrate having first and second surfaces, such that said switching and first transistors have a common drain contact provided on said second surface of the substrate.