L6569 Electronic Ballast

This is a electronic ballast circuit using L6569. This circuit uses The L6569 because it can control a low voltage halogen lamp transformer or a symmetric half bridge inverter of a fluorescent lamp ballast directly. The prevention of cross conduction is done by Two 270mA buffers drive the inverter MOSFETs with a 1.25ms built-in dead time. This circuit need only 150 mA at power up. Here is the circuit:

This circuit use BCD off line technology to drive The buffer of the upper Mosfet through a 600V level shifter. An oscillator and an internal 15V shunt regulator are used in this circuit. The internal regulator has a 9V Under Voltage Lock Out with an 1V hysteresis. And the frequency of the oscillator is from 25 to 150 kHz with a +/-5% maximum tolerance. [Source: STMicroelectronics Application Note]