AC to DC Converter Using Microcontroller

Abstract

The aim of the project is to obtain a controlled DC output from a standard single phase 230V, 50Hz power supply. For this we first rectified the ac voltage using four diodes. Then the rectified DC voltage is used to get controlled DC voltage output using an IGBT with a pulse of variable duty cycle, generated by a microcontroller. By varying the duty cycle of the square wave pulse the average output DC voltage is regulated. For user interfacing, a knob is used to set the required voltage. This is achieved by converting the analog signal input, from the knob, to digital signal by using the internal Analog to Digital converter present in the microcontroller. The microcontroller sets the duty cycle of the PWM wave according to the ADC value obtained. This PWM wave is given as input to the IGBT to regulate its duty cycle, and hence the average output voltage is regulated. This is basically the open loop regulation of voltage. If the load varies, then we have to use closed loop control to automatically increase the duty cycle of the gate pulse to the IGBT if the output voltage falls below a set point and vice versa. The negative feedback loop is based on PID loop control. Thus the output voltage is continuously tuned with the set point voltage.