Study And Design On The Programmable AC Power Supply Based On DSP

Based on the need to develop and test the products, a single phase DSPbasedprogrammable AC power supply is designed. The power supply is capable of providing a stableAC voltage with adjustable amplitude and frequency over a wide range. Moreover, it cangenerate various highquality and lowfrequency arbitrary waveforms. Because of theadvantages above, it will have great value in practice and a promising future in testing field.The main circuit of the power supply is to use rectifier and filter to make 220V ACvoltage become steady DC voltage firstly. Then the inverter and the LC LPF are employed toproduce the AC voltage which is required in the test system. The key part of the inverter is IPMmodule. The controller of the power supply is TMS320LF2407A which is a special DSP for thecertain applications like power electronics and power drive. It is not an expensive one but withhigh reliability and high operational ability. The EV module of TMS320LF2407A includingPWM generator is very effective in controlling power supplies and motors.Synchronous modulation is employed as the control method of the PWM generator. Thekey control strategy is to keep the ratio of the frequency of the carrier to the frequency of themodulator constant. So if the frequency of the power supply should be changed to meet therequirement, the frequency of the carrier must be changed .The detailed way to make it is tochange the value of the register T1PR of the Timer1 .Furthermore, if it is not enough, if theamplitude of the output voltage should be changed, the ratio of the amplitude of the carrier tothe amplitude of the modulator must be changed to meet the further requirement.The output voltage can be captured by the Halleffect voltage sensor. Then the voltage issent to the ADC module of the DSP. The data are calculated and operated to modify the valuesof the register CMPR to supply the closedloop control. The RS232 bus can also be used toprovide communication between the SCI module of DSP and the computer, so the values of thefrequency and the amplitude of the output voltage can be arranged in an easy way.