The load of DBD (dielectric barrier discharge) type ozonizer is of the capacitive characteristic, and its total equivalent capacitance becomes high gradually with the increasing of the voltage provided for the load. A high frequency power supply based on a closed-loop control strategy is presented in this paper. It is a kind of frequency traced control based on the output current of the inverter. The features of the control strategy are analyzed. The inverter based on the control strategy has the advantages of simple structure, small variation range of the working frequency and low switching losses. All analyses are confirmed by experimental results.

A shunt active power filter (APF) based on cascade multilevel converters with carrier phase shifted sinusoidal pulse width modulation (CPS-SPWM) is presented. The main sections of the shunt APF such as switching modulation strategy, harmonic and reactive current detection, AC side control and DC side control are discussed. Simulated results are given that verify this APF can compensate the harmonic and reactive current correctly and validly.

Sample time staggered SVM (STS-SVM) is a new modulation strategy for high power equipments, which has been successfully applied to multi-modular converters and cascade multilevel converters. Instanced by a kind of minimum switching loss SVM (MSL-SVM) in this paper, its modulation model is derived by dual Fourier transforms. The modulation model in frequency domain of STS-SVM is then deduced and the harmonic characteristic of that is analyzed quantitatively. The conclusions are drawn that this technique can largely improve the equivalent switching frequency with no fundamental component loss. This conclusion is the same with other kinds of SVM. Experimental results verified the theoretical analysis.

In this paper, the self-oscillating LC series resonant parallel load inverter for electronic ballast applications is investigated from a system point of view. By considering the discharge lamp as a resistor in steady state, the self-oscillating series resonant parallel load inverter with lamp loads can be naturally modeled as a relay system. Precise frequency determination and stability of self-oscillating is analyzed using the methods by describing function method, Tsypkin method (frequency domain) and Hamel method (time domain). The characteristic of these three kind methods is analyzed respectively. The design approach is described and implemented successfully in a 36 W fluorescent lamp system.