## The Significance of Fourier Analysis

The switch action in a conversion circuit is most often periodic. The waveforms themselves are rather choppy and sometimes discontinuous. We must form an approximate DC output of a rectifier, for instance, by piecing together ‘chunks’ of the AC input. Given the strange waveforms and the periodic action, how can we determine whether a conversion operation is successful? What filtering is […]

## Overview of Switching Devices

A switching function has a value of either 1 or 0; either a switch is on or it is off. When on, it will carry any amount of current for any length of time and in any direction. When off, it will never carry current, no mattery how much voltage is applied. This combination of conditions describes an ideal switch. […]

## Review of Fourier Series

Nearly any periodic function of time , such that , can be written as a sum of sinusoids known as the Fourier Series. where the radian frequency is defined as . This result applies to signals with jump discontinuities which are often encountered in the world of power electronics. While there are few very special periodic functions without Fourier Series […]

## Characteristics of Power Semiconductor Devices

Diode – Current ratings from under 1 A to more than 5000 A. Voltage ratings from 10 V to 10 kV or more. The fastest power devices switch in less than 20 nanoseconds, while the slowest require 100 microseconds or more. The function applies in rectifiers and DC-DC circuits. BJT – (Bipolar Junction Transistor) Conducts collector current (in one direction) when […]

## Kirchhoff’s Voltage and Current Laws

Granted, a switch circuit can perform power conversion, and granted, it can be described as a switch matrix. How do we make the choices of switch operation? Consider first the simple circuit shown to the right – something we might try for AC-DC conversion. This circuit has problems. Kirchoff’s Voltage Law (KVL) tells us: The sum of voltage drops around a […]

## Recap of Power Electronics

Power electronics involves the study of electronic circuits intended to control the flow of electrical energy. These circuits handle power flow at levels higher than the individual device ratings. Energy conversion is our business because people use light, mechanical work, information, heat and other tangible results of energy – not electricity itself. In most electronics, devices are limited by their […]

## Filtering a Switched Power Supply

As seen in the previous post, a simple switch or diode rectified output is still not a clean DC signal. The waveform contains AC components on top of the DC offset. The simplest methods for smoothing this output involve filtering through the use of passive storage elements such as capacitors or inductors. In essence, these components tend to smooth the […]

## The Effect of Phase on Switching Rectifiers

In the previous post, we examined some of the most basic switch based rectifying circuits and saw that the switch could be replaced with a passive diode. Here, we will explore what happens when the switch is no longer in phase with the input. Let us consider a different way to operate the switch. Using the same circuit as the […]