• ## 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 […]

• ## Basic Power Conversion Examples

Let’s look at a few examples of power electronic systems. Consider the circuit shown below. It contains an AC source, a switch, and a resistive load. It is therefore a […]

• ## Inverters, Controlled Rectifiers, and the SCR

In many cases, the distinction between a rectifier and an inverter is artificial; In a rectifier, energy flows from an ac source to a dc load. In an inverter, the […]

• ## The Need for Electrical Conversion

In the 1880s, two major inventions determined the course of electric power systems. George Stanley built a practical transformer, and so allowed convenient conversion among various voltage levels for ac. […]

## 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 […]

## Introduction to Switches

We have seen that circuits involving switches and energy storage can be operated to give energy conversion functions. Switches come in a huge variety including mechanical and semiconductor styles. It is important to develop a systematic way to identify appropriate power electronic circuits, and to find out how they can be controlled to give the desired performance. Consider, for example, […]

## 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 […]

## Important Variables and Notation

In a power electronic system, several electrical quantities are of special interest. Efficiency has already been identified in previous posts. Maximum values of currents and voltages will be needed to determine the necessary device ratings. Energy flow is the underlying objective, and power and energy levels in each part of the system are very important. We are most interested in […]

## The Reliability Objective and Integration

It is well established in military electronics that the more parts are in a system, the more likely it is to fail. As we shall see, power electronic circuits tend to have few parts, especially in the main energy flow paths. The necessary operations must be carried out through shrewd use of those parts. Often, this means that sophisticated control […]

## The Efficiency Objective and the Switch

As simple a circuit element as the light switch like the one illustrated below gives a reminder that the extreme requirements in power electronics are not especially novel. Ideally, when a switch is on, it provides vswitch = 0, and will carry any current imposed on it. When a switch is off, it blocks the flow of current (iswitch = […]

## The Basic Objectives of Electrical Conversion

The function of a power conversion circuit is to control the energy flow between a given electrical source and a given load. A converter must manipulate flow, but should not consume energy. The reason is simple. Since a power converter appears between a source and a load, any energy used within the converter is lost to the overall system. To be […]