Thanks everyone for the quick and informative responses!

I am going to research both the split transformer solution and the 5-12
voltage booster solution today.  $10 is too much for a switcher in this
application. The budget is more like $4 or under.

--BobG




-----Original Message-----
From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On
Behalf Of Mark Newland
Sent: Tuesday, July 17, 2001 10:09 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [EE]:Voltage Reg vs Switcher

Find a wall wart with a regulated 5V output and then use a boost convertor
to
get your LCD display voltage.

"Robert E. Griffith" wrote:

> I have a design that uses a 12v wall wart power supply because an LCD
needs
> the 12v.  The main circuit runs on 5v and 3v.  In the prototype I have a
5v
> regulator (LM340TS) dropping the 12v to 5v and a 3v regulator (TPS7230QP)
> that drops 5v down to 3v. This device will be on all the time.
>
> I have a heat sink on the 5v reg and it gets hot. I want to put the
finished
> circuit in a project box with vents but no fan.
>
> My question is: is there an easy, low cost, solution to implementing a
> switcher to drop the 12v to 5v? Is this done? The 3v reg does not provide
> much power so it is not a problem.

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