Analysis And Design Of Multiphase Interleaved Parallel BUCK DC-DC Converter

In the microprocessor power supply system,the DC-DC converter is required to output low voltage and large current.At the same time,in order to avoid voltage ripple interference with the digital circuit logic and lead to erroneous processing results,this requires DC-DC converter output voltage ripple lower.In order to meet these special power applications,this thesis has carried out research on DC-DC converters with output low voltage,large current and low ripple characteristics.The main work is as follows:Based on analysised the basic working principle of single-phase BUCK converter,presented the theoretical research and simulation of the topology of multi-phase interleaved synchronous BUCK converter,and presented the power stage circuit design method,including parameter calculation of input and output capacitors and energy storage inductor.Compared with the single-phase converter,the control strategy of the multi-phase interleaved parallel converter is more complicated,which is reflected in the need to solve the two problems of the current balance of each phase and the accurate phase shift of the drive signal.Affected by the manufacturing process,the actual parameters of the components of each phase are difficult to be completely consistent.The difference in parameters will lead to unbalanced current in each phase,reducing system stability and service life.Existing parallel current sharing technologies such as maximum current automatic current sharing method,external controller method,etc.need to add additional circuits,which increases circuit complexity.In this thesis,the average current control is used to achieve automatic equalization of the branch current of each phase without adding additional circuits.The simulation model of three-phase interleaved BUCK DC-DC converter based on average current control is built by Saber software.The simulation results show that the three-phase interleaved parallel DC-DC converter based on average current control can be realized without adding additional circuits and the current balance of each phase branch is better.A single-phase converter requires only one drive signal,while a multi-phase interleaved parallel converter requires multiple drive signals,and a certain phase difference is required between the multiple drive signals.In order to solve the problem of accurate phase shift of high-frequency drive signals required for multi-phase interleaving and parallel in analog circuits,the multi-phase interleaved parallel topology based on digital PID multi-loop control strategy is proposed by analyzed the disturbance signals of multi-phase interleaved parallel DC-DC converters.Taking the three-phase interleaved BUCK DC-DC converter as an example,the scheme is verified by Matlab/Simulink.The simulation results show that the three-phase interleaved BUCK DC-DC converter with this control strategy has those output characteristics.The output ripple is low,the load capacity is strong,the current balance of each phase and the dynamic performance of the system is good,and a good control effect is achieved.Finally,designed a prototype of three-phase interleaved BUCK DC-DC converter based on DSP digital PID control and built a test platform.When the output voltage is set to 1.8V,the peak-to-peak value of the output voltage ripple is measured to be 6.69 mV.The maximum load current is 18 A,and the maximum load regulation is less than 1.3%.When the load current is greater than 2A,the current imbalance of each phase is less than 5%.