Design and analysis of DC-DC PWM converter and DC-AC converter

Abstract

Converters are electrical circuits that converts a voltage level to another. Inverter is used in different purposes of lives. DC-DC converters are also known as switching converters, switching power supplies or switches. DC-DC converters are important in portable device such as cellular phones and laptops. Why do we need DC-DC converter? For example, when we want to use a device with low voltage level, if we connected the device such as laptop or charger directly to the rectified supplied from the socket at home, the device might not functioning properly or it might be broken due to over current or overvoltage. Therefore, to avoid unnecessary damage to the equipment and devices, we would need to convert the voltage level to suitable voltage level for the equipment to function properly. Inverters are required in a variety of applications including electronic ballasts for gas discharge lamps and electrosurgical generators. Induction heater is another field where inverter is needed. It is one of the popular techniques of producing high temperature. Pulse Width Modulation or PWM technology is used in Inverters to give a steady output voltage of 230 or 110 V AC irrespective of the load. The Inverters based on the PWM technology are more superior to the conventional inverters. The use of MOSFETs in the output stage and the PWM technology makes these inverters ideal for all types of loads. Pulse width modulation is the process of modifying the width of the pulses in a pulse train direct proportion to a small control signal; the greater the control voltage, the wider the resulting pulses become. PWM inverters are among the most used power-electronic circuits in practical applications. These inverters are capable of producing ac voltages of variable magnitude as well as variable frequency. The quality of output voltage can also be greatly enhanced, when compared with square wave inverters. The PWM inverters are very commonly used in adjustable speed ac motor drive loads where one needs to feed the motor with variable voltage, variable frequency supply. For wide variation in drive speed, the frequency of the applied ac voltage needs to be varied over a wide range. The applied voltage also needs to vary almost linearly with the frequency. PWM inverters can be of single phase as well as three phase types.