Digital simulation and laboratory experiments are used to illustrate the method and evaluate the computational effort requirred. This paper presents a comparative study of several current controllers. Particular attention is paid towards the hysteresis controller and the ramp comparator is proposed in which the current error signals are compared to three 120 degree phase shifted triangular waveforms. Computer simulations are used to compare the performances. Fast Fourier transform technique is used to show the power spectrum of the current waveforms.
Experimental results validate the simulated performances.
The ballast is based on the half-bridge topology and includes a high voltage igniter and dimming capability. It was also found that for the present experimental conditions, the lamp is purely resistive and that the resistance is practically independent of the power level and operating frequency. The 2.8kV ignition pulse was found to be sufficient for both cold and hot start up under the proposed operating conditions. The algorithm is based on stepwise quadratic extrapolations on the branch voltages across each reactive element together with progressive validation of the switches' operation. The power of this new technique lies in its simplicity in solving purely resistive networks for each topological configuration, generality in requiring no a priori understanding of the switching relationships and sequence of operations, inclusion of the effects of the parasitic elements, effectiveness of using computer memory, and ease of implementation on a desktop computer.