Electronics Cookbook

Chapter 7. Power Supplies

7.0 Introduction

Anything electronic needs a source of power. This may be as simple as a battery, but often will involve reducing high-voltage AC to the normal 1–12V DC that most electronics use.

Sometimes you need to generate higher voltages from a low-voltage battery. This may be stepping up the supply from a single 1.5V AA battery to a 6 or 9V, or it may be to generate much higher voltages for applications such as the 400V to 1.5kV supply needed by Geiger-Müller tubes.

The ultimate high-voltage power supply is a solid-state Tesla coil (see Recipe 7.15).

This is the first chapter where you will encounter a fair selection of ICs. When using an IC that you are not familiar with, your first port of call should be its datasheet. It will not only tell you how to avoid destroying it (by making sure you do not exceed its maximum ratings) but will also tell you how it behaves and if you are lucky will often include “reference designs” that are complete circuits that use the chip in a practical situation. These designs are developed by the chip manufacturer to show you how to use the IC, and many of the recipes in this chapter start from such reference designs.

If the datasheet for the IC does not include such useful designs, then the next thing to search for is “application notes” for the IC. This will often expand the rather terse and scientific-looking datasheet into practical circuits using the IC.

7.1 Convert AC to AC

Problem

You want to know how to ...