Research On Resonant Current Control Of Series Resonant High-voltage Capacitor Charging Power Supply

Pulsed power technology is widely used in high-tech industries, such as radiation sterilization, flue gas purification, medical devices, bio-science and so on. Capacitors have become the most common energy storage element due to its simplicity, reliability and mature technology. As a result, it is significant to study the control strategy for the capacitor charging supply.The Series Resonant Converter is the most widely used in capacitor charging supply. In the discontinuous current mode, the converter have many advantages such as simple to control, anti-load ability and. has the constant current characteristic, but it also has some disadvantages such as the outgrown resonance peak current and the difficulty of increasing the power. When operating in continuous current mode, PWM phase shift control is difficult to achieve soft-switching as the load charges, variable frequency control has much useless circulation in the initial stage. One kind of series resonant converter based on resonant current control is proposed in this paper, it detects resonant current in order to make switch on or off only when the resonant current is zero. Transducer is in continuous current mode, which has high work efficiency and ensures the switch tube working under arbitrary load conditions in soft switch at the same time.This paper introduces the four operating modes that the resonant converter may occur under the resonant current control. And uses iterative method to calculate and analyze the mathematical expressions between various physical quantities. Then it describes what effect will the distributed capacitance of the transformer and the switch lead angle for the converter. In the four circuit operating mode, the mode P can increase the charging current(defined as 1 state), mode F can reduce the charging current(defined as 0 state), so that charging current can be controlled upper and lower to the rated value by the method of state control.The average of the charging is essentially controlled by current State control, the RC low-pass filter can filter the AC component of the current in order to obtain an average value of the charging, but it also results in a feedback controller delay. The length of the delay determines the performance of state control, so a hysteresis comparator is added here to reduce the delays. We simulate the process of the circuit with MATLAB simulation software in this paper. Converter switching frequency and pulse width will not change under the resonant current control. The square wave with the current phase can be acquired through the comparator after sampling the resonance current, which can be directly used to control the on and off switching via a certain logic. So it uses analog components to construct the complex resonance controller and designs the various parts of the controller in this paper.Finally, an experimental prototype is proposed to do the capacitor charging experiments and verify the theoretical analysis, parameters’ design and the validity of the resonant current control strategy.