Design of a controller for DC-DC converters

Abstract

A dc chopper can be used as a dc transformer to step up or step down a fixed dc voltage. The chopper can also be used for switching mode voltage regulators and for transferring energy between two dc sources. However, harmonics are generated in the input and load side of the chopper and these harmonics can be reduced by input and output filter. A chopper can operate on either constant frequency or variable frequency. A variable- frequency chopper generate harmonic of a variable frequencies and filter design becomes difficult. A fixed-frequency chopper is normally used to reduce the sizes of filter and to lower the load ripple current, the chopping frequency should be high. Thyrister choppers require extra circuitry to turn off the main thyristor, and as a result the chopping frequency and minimum on-time are limited. This work covers the types of dc motor and the speed control method in a dc motor. A pulse width modulation controller and control of buck converters are designed to control the speed of a d.c motor.