Patent ID: 6483252
Filing Date: 2002-11-19
Classification: H05B,Y02B

Abstract:
A ballast circuit for stable operation of a high intensity discharge (HID) lamp, comprising:an AC-to-DC converter to convert power from an AC source to DC, the AC-to-DC converter including a buffer capacitor to capture AC ripple riding on the DC; a high frequency inverter and ballasting element (HFIBE) coupled to the AC-to-DC converter and to the HID lamp the HFIBE including a generating unit to generate a lamp driving signal from the DC power drive to said HID lamp; a driver circuit coupled to the HFIBE, the driver circuit including a voltage controlled oscillator (VCO) to generate a driving signal to drive the HFIBE; and a frequency control circuit coupled to the buffer capacitor, the HFIBE and the driver circuit, wherein the buffer capacitor provides a control signal to the driver circuit, and wherein the VCO in the driver circuit responds to the control signal by controlling the HFIBE to output a frequency swept square wave signal to power said HID lamp without driving said lamp into an acoustic resonant state.