A Dynamic Conductance Model of Fluorescent Lamp for Electronic Ballast Design Simulation

In recent years, fluorescent lamps operating at high frequencies have emerged as an energy-efficient alternative to directly replace the incandescent lamps. Fluorescent lamps are operated at high frequencies for the advantages of higher lamp efficiency and longer life, and the electronic ballast that operates such lamps is essentially a power converter that transforms the mains power into high-frequency power. Electronic ballast with various features such as dimming and automated response to daylight have been designed but currently the computer-aided design of such ballast relies heavily on some oversimplified fluorescent lamp models which leads to unsatisfactory characterization of the overall lamp-ballast system's performance. A dynamic conductance model of fluorescent lamp is presented here. The model is based on an expression for the lamp conductance derived from the time-dependent ionization balance equation. The ionization rates are calculated as a function of the instantaneous lamp power ranging from 0 to 70 W using the positive column model of Loo et al [1] and fitted using a cubic polynomial function. The diffusion loss rate of electrons to the wall is assumed to be constant. A dimming electronic ballast circuit is constructed to measure the voltage and current waveforms. The experimental measurements are compared to the simulation results in SPICE and a very good agreement is obtained. More work is being carried out to generalize the model suitable for simulations under various operating conditions.