Patent ID: 8274239
Filing Date: 2012-09-25
Classification: H05B

Abstract:
1. An electronic high intensity discharge (HID) ballast for driving a high intensity discharge (HID) lamp, comprising: a rectifier circuit operative to receive input AC electrical power and having a rectifier output providing a rectified DC voltage; a boost converter circuit operative to receive the rectified DC voltage and having a boos converter output providing a first converter DC output voltage; a buck converter including a buck converter input operative to receive the first converter DC output voltage, a buck converter output providing a second converter DC output voltage, a forward circuit path between the buck converter input and the buck converter output, and a return circuit path between the buck converter input and the buck converter output, the buck converter comprising: an inverter circuit operative to receive the second converter DC output voltage and including a plurality of inverter switching devices operative according to inverter switching control signals to convert the second converter DC output voltage to provide an AC output voltage at an inverter output to drive an HID lamp; and a clamp circuit operatively coupled with the buck converter output to sense the second converter DC output voltage and operatively coupled to provide the mode control input signal to the buck converter control circuit, the clamp circuit operative to provide the mode control input signal at the first level when the second converter DC output voltage is less than a reference value, and at the second level when the second converter DC output voltage is greater than the reference value.