Pt Resonant Converter Modeling And Simulation

Piezoelectric transformer (abbreviated as PT) is a power transmission device to conduct energy relying on mechanical vibration. It has the features of high voltage-gain, high power density, compact size, no electromagnetic noise and electromagnetic pollution, low cost and ease of mass production, etc., which bring it good development prospects. PT has been widely used in various electronic equipments such as electronic ballast for fluorescent, AC-DC and DC-DC converters. Therefore, many scholars and engineers have begun to work on the PT resonant converters in recent years. This paper put forward a small-signal model of PT resonant converter, based on which the compensating network is designed and the stability of the system studied.The electrical characteristics of PT resonant converter are similar to the characteristics of LCC resonant tank, while the LCC resonant tank is constituted mainly by the inductance and capacitance. So in one or several switching cycles, the voltage and current are sinusoidal signals. In the condition of small modulation index, the FM signal can be seen as amplitude modulation signal. With this method, the small-signal model for PT resonant converter from control-to-output is presented in this paper.However, the phase frequency characteristics of the small-signal model transfer function for LCC resonant converter has a large phase lag. To compensate for the lag, a band-stop filter providing 180°advanced phase is applied. A new resonant converter compensation network with a lead and lag compensator is presented in this paper. Bode plots of the compensated open-loop transfer function are mapped out by MATLAB, which verify the feasibility of this method. Finally, the output voltage waveforms of the open-loop and closed-loop are simulated via PSpice. The closed-loop transient simulation results show that when there are disturbances to the system load or to the input voltage, the output voltage can remain constant, which verifies the system's good stability and the correctness of the design scheme.