The Design Of Control Circuit Of Class-E~2 Soft Switch Power Supply With Only One Inductor

The main trends in development of the switching power supply are high frequency, miniaturization and high power density, etc. After proposing the soft switching technology, the switching power supply can achieve high efficiency under a higher frequency. And the soft switching technology is widely used for switching power supply field since it can reduce the volume of the switching power supply effectively and raise power density.There are usually two control methods for the switching power supply:constant frequency and variable frequency. Pulse-width modulation (PWM) is a common constant frequency modulation. PWM will achieve output control by changing the pulse duration (Duty cycle) but frequency of PWM driving signal remains constant, the frequency of variable frequency driving signal is inconstant. In the design, the converter works in soft switching state (zero-voltage-switching), but the two methods which are above-mentioned can't satisfy the requirement, therefore, a novel control method is proposed.The main research of this paper is design of control circuit of Class E2 isolated soft switch DC/DC converter since the control of output voltage is a key problem that must be solved in designing a high performance switching power supply. It is very essential to design a high performance control circuit. At the same time, there exists the probability of instability for the whole closed-loop control system. So a compensation circuit needs to be designed for the feedback control system in an attempt to make the system stable.First of all, the paper introduces the circuit topology and operating principle of class E2 DC/DC converter. Based on the topology and operating principle of DC/DC converter, a Class E2 isolated soft switch DC/DC converter with 100W and 24V output is designed, which has given the parameters of the circuit and chosen an appropriate switch device. Then it has validated by simulation assistance. And a control chip MC33262, being selected that combined with the operating principle and characteristics of the converter, is taken as the core to design control circuit of the converter. The designed control circuit consists of two components:isolating and sampling circuit used for sampling output voltage and isolating primary and secondary of the converter; type 2 error amplifier, designing compensated circuit for error amplifier to stabilize feedback circuit system. According to the characteristics of the chip as a critical current conduction mode controller, a RC lagging circuit is added in the circuit to realize the soft switch of the converter (zero-voltage-switch) and finally completes the whole design of the circuit. The paper designs the control circuit to make switching power supply in soft switching state available. It improves efficiency and power density with a stable circuit, which reaches the design target and will have a certain practical application.