REGULATORS IN PARALLEL

Other Hardware General Electronics
1

Hi

Is it OK to connect several constant voltage regulators in parallel to get increased current?
For example connecting 3 LM7809 9 volts regulators in parallel ?

Elico

2

Hi, no it is not okay to connect them in parallel. =(
If you need more current then look at the data sheet and applications for suggested circuits to boost their output.

http://www.ti.com.cn/cn/lit/ds/symlink/lm340-n.pdf

This link will tell you about LM78XX series and how to use them.

Tom...... :slight_smile:

3

Great info
Thanks

Elico

4

How much current do you require?

Tom..... :slight_smile:

5

For more current you want a voltage regulator that accepts an external pass-transistor.
The LM723 is a good example of a regulator chip designed to take advantage of an
external NPN power pass-transistor. (http://www.ece.usu.edu/ece_store/spec/LM723.pdf figure 16)

Or perhaps go to a DC-DC converter which can be more efficient.

Connecting linear regulators in parallel means they will fight each other, which
can lead to oscillation and destroy the whole circuit through over-voltage (happened
to me by accident - five surface-mount ICs needed replacing). The best outcome is
that one regulator takes all the load, which has no utility.