A transformerless single switch ballast for operating compact fluorescent lamps from batteries

The class E resonant ZVS inverters are well suited for economic and reliable electronic ballast due to their high efficiency and versatility. In general, the compact fluorescent lamp (CFL) has high efficacy rating together with a low power rating (typically 7 W or 11 W) and hence, can be easily operated from batteries. The design procedure of a self-oscillating and high output voltage transformerless CFL inverter, operated from batteries, has been discussed in detail. The basic equations for the component selections have been derived and their validity has been checked with PSPICE simulations. This design procedure is independent of the input DC voltage and is equally applicable for high voltage fluorescent lamp ballast. An inverter meant for CFL application, has been designed for 24 V DC input and tested in the laboratory. The performance has been found to be quite satisfactory. The associated waveforms for this inverter have been presented. Since, this ballast circuit works on ZVS principle, the device losses are negligible, which is evident from the oscillograms. The two main striking features of this circuit is that (a) the circuit is self oscillatory and (b) the output voltage boosting is done by a series parallel loaded network.