A simple, cheap bipolar power supply

[Paul Schreiber]

ALSO:....

The AC line voltage will vary from 85 to 132 VRMS on the input of the transformer. So there are 2 things to worry about:

a) at low line, there is at least 2 volts across the regulators
b) at high line, they don't fry

Paul Schreiber
Synthesis Technology

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From: 	Mariano Elizalde[SMTP:mariano-elizalde at worldnet.att.net]
Sent: 	Sunday, February 23, 1997 11:16 PM
To: 	chordman at concentric.net
Cc: 	synth-diy at horus.sara.nl
Subject: 	Re: A simple, cheap bipolar power supply

At 10:53 PM 2/23/97 +0000, you wrote:
>Here is a simple bipolar linear supply.  Using good heat sinking, over
>1 ampere is available from each pole.  Other regulator ICs are
...
>Here is an ascii-matic:


  ... just a couple of suggestions;

... use a transformer rated to 18VAC instead of the one you suggest because;

at 12VAC <secondary> you will not have enough raw dc to hold regulation into
the LM7815/LM7915
 
at 12VAC as the secondary voltage, the rectified DC will be about
(12(vac)*1.414)-0.6 or, 16.38 vdc.

at 18vac <secondary> the raw dc will be around 25 volts... you stress a bit
the regulators but if they have a heatsink, they will survive..

 the LM7815/7915 are rated for an input of 3 volts above the regulated
output or about 18 volts...


and last; suggest you multiply times 10 the value of your capacitors  in
order to reduce the ripple and to hold max. output power (I*V) since you are
using half wave rectifiers there...

 ... just a suggestion...  :)

mariano



   mariano

  elizalde at internetconnect.net