Research On Capacitor Charging Power Supply Based On TMS

Transcranial magnetic stimulation(TMS)as a non-contact,painless,non-invasive stimulation method,has obvious advantages in clinical application and basic research on brain function.The TMS technology mainly relies on the pulsed magnetic field generated by the magnetic field generator to achieve therapeutic effects.The magnetic field generator mainly comprises a charging energy storage system(charging power supply and energy storage unit)and a discharge system(discharge switching circuit and stimulation coil).The capacitor charging power supply(CCPS)is an important part of the magnetic field generating circuit system,which is of great significance to the system to produce a smooth and reliable pulse magnetic field.Aiming at the problems of large charging circuit and low charging accuracy in the traditional magnetic field generating circuit,this paper analyzes and designs the capacitor charging power supply based on resonant converter.Firstly,this dissertation analyzes and summarizes the circuit topology of the existing capacitor charging power supply,especially the resonant converter is the most widely used.According to the analysis of the working characteristics of the LCL-T resonant converter,the influence of the parasitic parameters of the transformer on the power supply is analyzed,and the parasitic parameters of the transformer are absorbed as part of the resonant circuit.The LC-LC resonant converter is used as the capacitor charging power supply.Secondly,the fundamental characteristics of the resonant network are analyzed by the fundamental frequency approximate ac analysis method,including:current gain H,converter voltage-resonant current phase relationship and voltage gain M of the resonant network.Obtaining the operation under the conditions of?_n=1 and?+?=1 is the basic condition for designing the LC-LC resonant converter as a constant current source.At the same time,it is found that the converter voltage and the resonant current remain in phase,so that the inverter switch achieves zero current shutdown and reduces switching losses.The converter voltage gain varies with load impedance,reducing the need for high frequency transformers.The simulation results are verified by PSpice simulation software.The simulation results are basically consistent with the theoretical analysis,and the feasibility of constant current charging is verified.Finally,combined with the previous theoretical analysis and performance indicators of capacitor charging power supply,the overall experimental platform is built,including the main control circuit and main circuit module with KL25 as the core.The main circuit includes an EMI filter circuit,an input rectification-filter circuit,a soft start circuit for preventing surge current,an LC-LC resonant inverter circuit,a voltage detection circuit,and an auxiliary board-level power supply circuit.And the board-level power supply voltage and voltage detection circuit are tested and analyzed.The power supply voltage waveform is flattening.During the input voltage of 1V?3V,the relative measurement error is less than 1%,which met the requirements of the system.Experimental tests show that the resonant current remains in phase with the converter voltage,enabling soft switching of the inverter switch.The linear rise of the load voltage indicates its constant current output characteristics.The charging circuit can achieve an output voltage of up to 300V,and the charging accuracy is less than 2%,meeting the design requirements.