Philips Electronics North America Corporation

Eugene J De Mol

Stephen L Wong

Paul R Veldman

A switched bridge circuit includes a low voltage to high voltage interface which selectively controls an input to a high side switch. A controller compares the voltage across the interface, the state of the high side switch, and the output of the circuit. If hard switching is detected by the controller, it latches the voltage across the interface thus keeping the high side switch on to allow the hard switching to occur. If soft switching is detected, the high side switch is kept off. A source follower is used to drive the high side switch so that the circuit output follows the interface output thereby avoiding oscillation. A falling edge detector for the output of the circuit uses the inherent parasitic capacitance of a high voltage device which also forms a bootstrap diode. When the output drops, the parasitic capacitance feeds a resistance which causes a driver to actuate. A second falling edge detector uses the inherent parasitic capacitance of the level shifter switch which is another high voltage device. When the output drops, the parasitic capacitance turns on a switch. A rising edge detector also uses the inherent capacitance of the low voltage to high voltage interface. A switch is coupled to the circuit output and the low voltage to high voltage interface. When the circuit output rises, the switch actuates.

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Eindhoven, Netherlands

Eugene J De Mol