Research On Design And Optimizaiton For A 10 MHz Isolated Class Φ₂₄ DC/DC Converter

With the development of modern electronic equipment,the performance of its power supply,the key part of electrical application,needs to be improved.The user’s demand aims at higher integration,portability and efficiency.The application of high-frequency power conversion technology can reduce the numerical value of energy storage components in topology,which effectively decreasing the weight and volume of the switching mode power supply（SMPS）.However,with increasing operation frequency,some serious challenges occurs for the components of SMPS such as switching power devices,magnetic components,and high-frequency driver IC,etc.Therefore,the researches aiming at the high frequency power conversion topology,magnetic components and the control strategies suitable for high-frequency switching conditions is vital to improving the performance of modern SMPS.In this dissertation,the problem that the high voltage stress across power device in traditional ClassΦ₂ resonant inverter topology is concerned,and ClassΦ₂₄ topology is proposed to improve the resonant filter network of the topology and further suppress the resonant voltage stress under steady state,the detailed derivation procedure of its parameters is given.Then,three inductors in the topology are replaced by the leakage inductance of the high-frequency transformer,which reduces the number of magnetic devices and improve the power density.In addition,the value range of the parameter C_F in the inverter topology is optimized with efficiency and the optimization design procedure is given.In order to improve the efficiency and power density of the high-frequency power converter,the planar PCB inductor and the planar PCB transformer with optimized structure parameter is designed.In order to solve the difficulties occur in the analytical estimation of inductance value to windings with complex structure,the electromagnetic simulation software,Ansoft HFSS is adopted to complete inductance calculation and get a series of structure parameters meet the design requirements,then these data points in the design space are fitted and the theoretical optimal solution of the magnetic device’s structure parameters is obtained to manufacture the PCB board..Aiming at the problem of voltage overshoot phenomenon and transient zero voltage switching（ZVS）failure problem caused by state switching operation in traditional closed-loop ON/OFF control,the modified Soft-Start PWM-ON/OFF control strategy with initial adjusting stage is proposed,the duty cycle and frequency in this stage is adjustable,which can effectively suppress the transient voltage overshoot across drain and source to Ga N power device,and eliminate the transient ZVS failure phenomenon within certain load range.The relationship between frequency parameter f_s and Duty parameter D of PWM pulses in proposed topology is derived by proposed waveform approximate method under ZVS limit.The interrupt delay caused by instruction cycles of DSP is solved by program flow optimization,so the error pulses invalidate the ON/OFF transient overvoltage suppression performance is avoided.As a result,the efficiency of the converter is ensured,the practical working condition of the Ga N transistor is improved,the durable life and reliability of the high-frequency power converter is increased.In order to verify the effectiveness of the proposed topology,magnetic device and the control strategy,a ClassΦ₂₄ isolated DC/DC prototype with 20 W output power is built in digital control.The test result shows that the voltage stress across Ga N when D=0.46 is only about 2.41 times of input DC voltage V_in in steady state,which meets the design specifications.Compared with the traditional ClassΦ₂ topology,V_dsmax in steady state is reduced by 15%;the peak value of transient overvoltage under proposed control strategy is decreased by 38%comparing with the traditional ON/OFF control,The efficiency of the prototype using the proposed optimized planar PCB inductor is increased by about 4.2%,which verifies the effectiveness and feasibility of the proposed resonant topology,magnetic device optimization design method and Soft-Start PWM-ON/OFF control strategy.