Patent ID: 6452343
Filing Date: 2002-09-17
Classification: H05B,Y10S

Abstract:
A ballast circuit for operating a discharge lamp comprising:input terminals for connection to an adjustable dimmer providing a low frequency supply voltage, rectifier coupled to the input terminals for rectifying the low frequency supply voltage, buffer capacitor means coupled to an output of the rectifier, for charging to a DC voltage, said voltage being dependent on the adjustment of the dimmer, and an inverter coupled to the buffer capacitor means for generating a high frequency lamp current from the DC voltage during operation, said inverter comprising a control circuit for controlling operation of the inverter, the ballast circuit further comprising a shut off circuit for switching off the control circuit and the lamp if said DC voltage drops below a first predetermined value, said first predetermined value being greater than a value at which the control circuit will receive insufficient energy to operate properly.