Make your own free website on
EDN Access

[an error occurred while processing this directive]  

May 22, 1997

Transformerless supply fits CATV applications

Michael Ellis, Antec Technology Center, Norcross, GA

Coaxial CATV systems derive their power from a 60-Hz square wave that shares the center conductor with the television channels. You often need to place active devices along the distribution path. If the dc-power requirements for these devices are small, you can use a transformerless power supply to provide power to the active devices. The circuit in Figure 1 provides current as high as 10 mA at 5V dc. You can modify the component values for any desired output voltage and current. The design equations for selecting the components are the input parameters,

Minimum ac square-wave input voltage=VIN(min);

Maximum ac square-wave input voltage=VIN(max);

Desired dc output voltage=VOUT;

Maximum desired dc output current=IOUT;

For a complete derivation of the design equations and the Spice-simulation results, send a self-addressed envelope to Michael Ellis, Antec Technology Center, 5720 Peachtree Parkway, Norcross, GA 30092. (DI #2036)

Figure 1


Look, Ma, no transformer. Capacitive coupling allows you to derive power from the 60-Hz square wave in the coaxial cable in CATV systems.

| EDN Access | Feedback | Table of Contents |

Copyright 1997 EDN Magazine, EDN Access. EDN is a registered trademark of Reed Properties Inc, used under license. EDN is published by Cahners Publishing Company, a unit of Reed Elsevier Inc.