Patent ID: 7321201
Filing Date: 2008-01-22
Classification: H05B

Abstract:
1. A control circuit implemented in an integrated circuit for providing a control signal to a power semiconductor device for providing power to a filament lamp, said control circuit comprising: an oscillator for generating said control signal; and a shutdown circuit for shutting down said oscillator in response to a fault condition including both overload and short circuit conditions, wherein said control circuit senses load current as a feedback voltage on a resistor connected to said power semiconductor device and feeds back said voltage to detect both short circuit and overload conditions, wherein said control circuit detects a short circuit by determining whether said feedback voltage exceeds a first threshold, and detects an overload by determining whether said feedback voltage exceeds a second threshold, said first threshold being higher than said second threshold, and wherein said control circuit shuts down the oscillator if the feedback voltage exceeds the first threshold for a first time, or exceeds the second threshold for a second time, said first time being shorter than said second time.