Research And Design Of Multi-output Forward Converter With Low Crossover Regulation

The cross-regulation problem has been well solved in the multi-output flyback converter,but in the application of the multi-output forward converter,the cross-regulation problem has not been effectively solved.In order to reduce the cross regulation rate of the multi-output forward converter,a target average current control strategy is proposed,and the design of a three-output forward converter is completed with this strategy.The specific implementation process of the target average current control strategy is to sample the output voltage and output current of each channel in real time to obtain the real-time load RLi;obtain the target average current from the expected output voltage VEi of each channel and the real-time load RLi;from the secondary side energy storage inductance The relationship between the peak current and the target average current IEi,the secondary side energy storage inductance value,the real-time input and output voltage value,the expected output voltage value and other parameters calculate the on-time of each rectifier switch tube on the secondary side;the primary side main switch tube is turned on The time is equal to the maximum on-time value of the secondary side rectifier switch tube.The software programming and hardware system design are completed,and STM32F103C8T6 is selected as the main controller.The primary side main switch tube is driven by transformer isolation,and the secondary side rectifier switch tube is driven by bootstrap.A diode is connected in series after the rectifier switch,and the cathode potential of the diode is used as the reference potential of the bootstrap drive circuit to keep the terminal voltage of the bootstrap capacitor stable,and the stable bootstrap voltage makes the drive voltage of the secondary rectifier switch tube.It continues to be normal during the on-time of the switch.The hardware parameters of the secondary side energy storage inductance,transformer,etc.all give a detailed design process.The proposed control strategy is simulated by Saber circuit simulation software.It can be seen that under this control strategy,the cross regulation rate of the multi-output forward converter is within 1%,which is consistent with the theoretical analysis.Prototypes were made and performance tests were carried out.The experimental results showed that the cross regulation rate of the three outputs was less than 1.4%,and the output voltage accuracy,load regulation rate and voltage regulation rate all met the research goals.