Research On Conducted EMI Suppression Measures Of Induction Heating Power Supply

Induction heating technology is widely applied in metal melting, heat treatment and other industries with characteristics which are not available in traditional heating technology. In recent years, with the continuous development of power electronic technology, the switching speed and frequency of switch power converter lead to the increase of power density of switching devices and electromagnetic compatibility(EMC) problems of switching power converters, which conduction Electromagnetic interference(EMI) problem is particularly prominent, also makes the EMI problem become the current research focus of EMC.Study the topology of induction heating power supply, analyze conduction EMI path, and mathematical modeling, build the system simulation model test conducted EMI size. Three kinds of conduction EMI suppression measures are proposed: first, the hybrid EMI control technology based on active filter and chaotic control is proposed from the propagation path and the frequency band range; Second, the transmission EMI active elimination method based on the driving signal feature extraction from the interference of the switching device; Third, the transmission EMI passive elimination method based on impedance balance is proposed from the circuit topology and interference signal loop.For the proposed suppression measures, active filter circuit and chaotic control circuit are designed, and based on the characteristics of the active filter in the low frequency and chaotic control in medium-high frequency, the conducted EMI is suppressed from full frequency range;Discussed the relationship between the amplitude and phase of drive signal and EMI in power supply, and adjusts the PWM drive signal extracted by the conditioning circuit, which has the same amplitude and phase of the interference signal on the DC bus; On the basis of equivalent modeling, by adding a new interference circuit to prevent EMI from signal flow to network side,and to design the balance circuit according to the balance conditions of the equivalent model,the voltage of the balance circuit is reduced to zero, that is, the external current signal is zero,so as to suppression of conducted EMI.On this basis, this paper has set up a platform main circuit simulation model and experimental test to test conducted EMI size, three different suppression circuit model and experimental model are built, simulation and experimental results show that three conducted EMI suppression measures can effectively reduce the conducted EMI in power supply.