This application note presents the half bridge converter for electronic lamp ballast using the L6574 and L6561. The L6574 is a high-performance ballast driver, designed using 600-V BCD offline technology, which ensures all the features needed to properly drive and control a fluorescent bulb. It is provided with built-in VCO start-up sequence circuitry, protections, and an operation amplifier for implementing a closed-loop control of the lamp current.