Electronic ballast for HID lamps with high frequency square waveform to avoid acoustic resonances

This paper presents a driver for an HID lamp based on the application of a high frequency current square waveform through the lamp with the goal of avoiding acoustic resonances. The proposed ballast is fed from a 12 V DC input voltage and is intended to be used in systems supplied from nonconventional sources, such as back-up batteries, photovoltaic generators and automotive applications. In order to initiate the discharge in the lamp, a specially designed igniter supplied from the 12 V DC voltage is used to apply high voltage ignition peaks to the lamp. Experimental results obtained from a laboratory prototype for a 70 W metal halide lamp supplied at 30 kHz are also shown to evaluate the possibilities of the proposed topology.