Design Of High Speed Control Loop For 1MHz LLC Resonant Converter

In a switching power supply system,dynamic response is an important indicator of the performance of a switching power supply.The dynamic response of the switching power supply can affect the stability of the powered device.Subject to digital control delay and linear control strategy,the dynamic response of traditional digital switching power supply can not meet the requirements of some high-performance electrical equipment.Therefore,research on the high-speed control scheme of digital switching power supply has the stability to ensure the stability of electrical equipment.Important practical significance.In this thesis,a high-speed closed-loop control scheme is proposed for the Buck Boost LLC cascade converter.The dynamic response of the cascade converter is improved from the aspects of reducing the digital control delay and improving the control strategy.In terms of reducing the digital control delay,the method of finding the phase shift amount by using the Look Up Table(LUT)replaces the traditional phase shift calculation process,thereby reducing the closed loop control period.In terms of control strategy,a hybrid control strategy is proposed,that is,when the cascade converter works at light load,an improved ON/OFF control is adopted,so that the cascade converter can realize its dynamic response while improving its dynamic response.Efficiency optimization;when the cascade converter works at non-light load,this thesis introduces a fast dynamic switching control strategy based on traditional PI control.The strategy controls the output capacitor and the energy in the pre-output capacitor to quickly replenish or release the load when the cascade converter is switched to improve the dynamic response of the system.Through the cooperation of the LUT algorithm and the hybrid control strategy,the dynamic response of the cascade converter in the full load range is improved,and the output voltage overshoot is limited.The design content of the thesis is verified on the prototype of the cascaded converter with a switching frequency of 1 MHz.The test results show that the proposed method based on LUT to find the phase shift shortens the closed-loop control period compared with the method of directly calculating the phase shift.75%.At the same time,the high-speed closed-loop control scheme proposed in this thesis,when the load is switched from 50% to 10% load,the dynamic response time is 470?s,which is about 30 times higher than the traditional PI control.In addition,the overshoot of the system output voltage is also limited to 5% of the output voltage.