Analysis of self-excited electronic ballasts using BJTs/MOSFETs as switching devices

Self-excited electronic ballasts are analysed and compared using the same circuit configuration but two different switching devices, BJTs and MOSFETs. These two different charge-driven switching devices normally result in different circuit behaviour and design. According to the operating points of saturable driving transformers and switching devices, a complete circuit operation is divided into six stages. Based on the charge control analysis, the effects of switching devices on the self-excited ballasts are discriminated and evaluated. The analysis reveals that BJTs are more suitable than MOSFETs in this transformer-driven self-excited ballast circuit, and it also provides a clear insight into the utilisation of switching devices.