Patent ID: 7298099

Claim:
An IC for controlling a power supply circuit for delivering power to a load circuit including a fluorescent lamp resonant output stage, comprising: ballast control and driver circuitry that provides drive signals to the power supply circuit, receives current sense signals indicative of current in said output stage, and responds to the current sense signals by modifying the drive signals; the ballast control and driver circuitry including: drive circuitry that provides the drive signals; and fault detection circuitry that receives the current sense signals and provides a detect signal in response to an overcurrent fault in the output stage, wherein each detect signal corresponds to an overcurrent condition coinciding with one of said drive signals, and in response to said detect signal, causes the drive circuitry to cease providing the drive signals; wherein said fault detection circuitry comprises an internal fault counter that delays termination of said drive signals until a predetermined number of consecutive detect signals have been counted; and wherein said internal fault counter reduces its count of detect signals when a drive signal does not coincide with an overcurrent condition in the output stage.