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