Research And Design Of PWM Power Amplifier Based On Resonant Pole Soft Switching

Lithography system is the equipment of manufacturing electronic components. Ultra precision planar motor and servo drive are the most critical elements, which are the power source of system that determines the accuracy of lithography system. As the blank of domestic research and the technology blockade of foreign companies, it shows important significance to carry out the research on PWM power amplifier.First of all, the theoretical research on the two key modules in PWM power amplifier is carried out, including the converting topology and current controller. The switching frequency is higher, the output current ripple has smaller peak-peak value, and system can obtain a better dynamic response. But with the increasing of switching frequency, both the switching loss and EMI get worse. Soft switching technology can solve these problems effectively. Among all kinds of soft switching circuits, resonant pole soft switching has been widely used because of its simple structure. This paper carries out a detailed theoretical analysis of resonant pole topology, and then analyzes the modified circuit. There are kinds of PWM tracking methods. Dues to the advantages of simple structure, easy to be realized, and closed loop control, and better dynamic response, the hysteresis current controller has been widely used. This paper carries out the theoretical analysis of variable hysteresis current control method, and discusses its application theory for resonant topology. When the high side switching device of bridge arm is driven by bootstrap circuit, the minimum ON time and the maximum duty cycle can not be guaranteed. A method to solve the problem by the criteria of diL/dt has been imported.Based on the above theories, this paper designed the circuit of the prototype in details.The modified topology was analyzed based on the basic resonant pole topology. This paper proposed a methed to design the components’ parameters of resonant pole soft switching and filter by the criteria of switching frequency, filter resonant frequency and maximum duty cycle. As the MOSFET gate driver capability determines the switching frequency, so accordingly, the gate drive circuit parameters were designed in details. The feedback circuit is the hardware implementation of hysteresis current controller, which has an important impact on the performance of the entire system. So this paper proposed the current sampling scheme, designed the hall sampling circuit and current transformer circuit the hysteresis current control. At last, other function circuits were designed, such as the control module, the over-current protection circuit, etc.Finally, based on the principle circuit and theory of variable hysteresis current control method, a prototype was manufactured and the current control program applied in FPGA was designed. Then measurements were performed on the prototype with variable hysteresis current controller. The results proved the correctness and feasibility of the principle and design.