Applied Research To Restrain Electromagnetic Interference On The Flyback Type Power Converters

In recent years, with the rapid development and wide application of the power supply, the development trend of miniaturization, high frequency makes the electromagnetic interference problem becomes more and more serious, which will not only affect the normal work of flyback power supply itself, it also can cause pollution to the surrounding electromagnetic environment, and influence the normal work of the equipment or system around him. Therefore, the electromagnetic flyback power compatibility issues are getting more and more attentions, as the core of electromagnetic power supply, DC converter compatibility problems is the priority.This paper is focused on the use of pulse width modulation model type (Pulse Width Modulation, PWM) IC design of flyback power converter. This paper uses S.T UC3842production company PWMIC current mode typical, with a complete circuit is equipped to supply a high performance, high reliability of the switching power converter. The output voltage is15V, output current is4A, the output power of the power converter60W. The main components include:switching power components, isolation transformer, PWMIC, output diodes, the output capacitor. The converter provides a voltage output path. Electromagnetic interference can obtain stable output voltage and small, help to increase power density, reduce cost.This paper first discusses the basic principle of flyback power converter, and next puts forward the flyback type power converter circuit design based on UC3842PWMIC, then explain the consideration of measurement to restrain the electromagnetic interference, it mainly focus on the EMI emission energy of those bands to make the centralized spectrum energy diversified so that achieve frequency drift, to meet the EMI tolerance to solve the EMI problem. Finally60watts of traditional PWMIC and new type PWMIC power converters are produced and measured to experimental verification. According to the experimental results, the use of frequency jitter technique of PWMIC can reduce the electromagnetic interference more than traditional PWMIC. Compared with the traditional electromagnetic interference suppression measures such as reducing the leakage inductance and distributed capacitance, frequency jitter can effectively solve the EMI problem. It can increase power density and reach the goal of reducing the cost.