The Basic Technology Research Of DSP On Power Electronic System

The traditional power electronic circuits,especially in the switching power supply,almost all of the control come from the analog IC chip to complete and achieve, besides, the technology is more nature.However,the power supply is becoming much smaller,more portable and the frequency is higher than before. So the requirements are also increasingly high. At this moment the digital control strategy is a hot issue for all research.In recent years, along with the b reakthroughs achieved by digital signal processing technology, an increasing number of digital signal processing chips are used in the field of power supply, among these, one of the most widely used is the DSP which is made by TI company. But how to select the DSP and so on,we still lack the theoretical support.Thus with the base of digital PFC(Power Factor Correction) circuit and the reference of the anolog control circuit, we launch a discussion about the digital control and some questions related to it in the field of MH power supply.In this paper,the works are as follows:(1)At the base of one actual circuit, by contrast two different op-amp, we get the conclusion:the selection of the op_amp is very important.In addition,the bandwidth also plays an important role in the circuit,the simulation results are almost the same as the calculated basic.(2)The input impendence of the extral circuit for samping is quite large, we have given the equivalent model of the DSP internal ADC circuit,and a practical circuit analysis,proved that if the external input impedance choice is not appropriate, then there will be a great deviation between samping and actual values.(3)As the gain error and offset error will result in the ADC data deviation,so the proposed three methods to improve the accuracy of the DSP internal ADC,that is:software calibration,extenal AD chips of higher resolution and dual-sort mode.Not only this,but also we give traces on the PCB that should be noted and corresponding solutions.(4) The sampling is also a process of quantization,which will inevitably lead to a difference between sampling and actual values.Therefore a error is brought into the circuit.Here we introduce a square wave and a sawtooth to represent this error, and get the formula in the worst case resolution. We calculate the three-way sampling of the PFC circuit, and know that the DSP is fully meet the requirments. (5) Because of the unique advantage in the discretization of anlog system to digital system, the bilinear transformation is widely used.In this paper through anlyzing the three transformation methods, and by contrast of the difference at the stability in the time domain, frequency domain, the dynamic response, we get the conclution which method is optimal.(6)For power factor correction,in order to ensure constant power,then the input voltage and the input current should be was the trend of change in the opposite direction, but on the other hand,in order to impore the power factor, they shoule be was a positive change in direction, so this is a contradiction.To reslvove this problem,this paper introduces a feed-forward voltage,and realized the digital feedforward control technology through sofware,and achieved good experiment results.