Research On Soft Switching Resonant Converter With Voltage Multiplier

With the rapid development of power electronics and the appearance of fully-controlled devices,high-voltage DC power supplies have been widely used in daily life,agriculture,industry,military and other fields.There are two basic methods to generate DC high voltage: The first method to form a boost converter is using high-voltage transformer with high turns ratio and rectifier diodes with high withstand voltage.However,in practical applications,transformer ratio which is too high will increase the non-ideality of the transformer,and the non-ideality will lead to spikes in the voltage and current of the transformer,loss and noise increased,distributed capacitance increased and other problems.The second method is using the voltage multiplier which is connect with the secondary side of the high voltage transformer to raise the voltage.and the use of voltage multiplier can boost the voltage of the transformer twice.By using voltage multiplier circuit,the turns ratio of the transformer and the non-ideality above mentioned can be greatly reduced.The development trend of highvoltage power supply is high-frequency,high-voltage power supply can work under the conditions of high-frequency,which can not be separated from soft-switching technology.The resonant converter that adding a resonant network between the primary side of the transformer and the inverter circuit can implement soft switching,which can reduce the switching loss of the switching operation at high frequencies.Therefore,the structure of the resonant network,high-frequency transformer,voltage multiplier circuit is a reasonable choice for achieving high voltage.This thesis mainly works on the voltage multiplier boost circuit in the high voltage power supply.Through the reading of the literature related to high voltage DC power supply,In-depth study of the voltage multiplier circuits at home and abroad,a new resonant voltage multiplier is designed.Firstly,the principle and implementation method of soft switching are analyzed,and the series resonant converter which can realize soft switching technology is studied.The transient steady state mode,voltage drop and ripple of the CW voltage multiplier circuit are analyzed in detail.The comparative analysis of several voltage multiplier circuits derived from CW voltage multiplier circuit is carried out.The positional relationship between the capacitor and the diode is established.The method of deriving different types of voltage multiplier circuits from the changing the positional relationship between capacitors and diodes is studied in detail,and the laws of capacitors and diodes in the voltage multiplier loop of these voltage multiplier circuits are described.Secondly,a new topology of voltage multiplier circuit is proposed,and the equivalent circuit of the circuit in the steady state working period is given.Through the detailed analysis of the circuit’s working mode,the mathematical expressions of the output voltage ripple,output voltage,output voltage gain and short-circuit characteristics of the circuit are derived,and the circuit is quantitatively analyzed.Finally,the voltage gain characteristics,short-circuit characteristics and output voltage characteristics of the new voltage multiplier circuit were simulated,and the experimental circuit model of resonant voltage multiplier circuit is built.The driving signal and resonant current waveform of the switch are analyzed from simulation and experiment,and it is verified that the switch realizes soft switching.In addition,from the calculation results of the model,the simulation results and the experimental results,the resonant voltage multiplier circuit and the CW voltage multiplier circuit are compared and studied.It is verified that the new resonant voltage multiplier circuit has the characteristics of smaller output voltage ripple and output voltage drop.