Searching \ for '[EE]:Voltage Reg vs Switcher' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/power/priswitch.htm?key=switcher
Search entire site for: 'Voltage Reg vs Switcher'.

Exact match. Not showing close matches.
PICList Thread
'[EE]:Voltage Reg vs Switcher'
2001\07\17@085858 by Robert E. Griffith

flavicon
face
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.

Thanks,

--BobG

{Original Message removed}

2001\07\17@091954 by Byron A Jeff

face picon face
On Tue, Jul 17, 2001 at 08:57:40AM -0400, 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.

Easy? yes. Low cost? Depends on your price range. Take a look at the National
semiconductor Simple switcher series. Requires little more than a coil, diode,
and a cap. But the total cost will be in the $10 range.

BAJ

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics


2001\07\17@100102 by Ashley Roll

flavicon
face
Or the Linear Technology LT1111 if your current requirements aren't too high
(300mA?)

The application note has some example circuits and you can get a 12-28v to
5V 300mA output with 5-7 components.

Also look at the LT1173, LT1070, LT1071.

There are heaps of these types of chips out there. I don't know about
prices.

You can also get pre-made SIP/DIP modules. eg NME1205 (12V -> 5V).

A word of warning, you may want to add a L/C filter after the switcher to
kill some of the noise it generates.

Alternatively you could use a 5V wall wart and a 5V -> 12V switcher to get
the power for the LCD (assuming it doesn't use much current). It may even be
possible to use "switched capacitor" voltage doubler to get nearly 12V for
the LCD and be "close enough".

Ash.

> {Original Message removed}

2001\07\17@100317 by Roman Black

flavicon
face
Byron A Jeff wrote:
>
> On Tue, Jul 17, 2001 at 08:57:40AM -0400, 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.


Hi Jeff, since you didn't specify the currents at the
3 voltages, I can only guess, but one way to handle
this problem is to get a cheap multi-tap transformer,
like 3v-12v, these are common from most hobby type
electronics shops, and similar sizes and costs to
your wall wart.

This can give you a 12v rail and a 7v rail, ready for
the 3 pin regulators. Cheaper and simpler and more
reliable than going to switching regulators, and more
efficient as a transformers runs about 90% efficiency.

After servicing many cheap CD portable hifis and CD
players I notice all the manufacturers doing this,
cheap multiple tap transformer and six diodes (two
full rect bridges) to give the 12v rail for the
mechanicals and power amp and the 5v rail for all the
control circuits.
-Roman

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics


2001\07\17@101037 by artstar

flavicon
face
You could definitely go switcher but depends on how you define low-cost.
If $10 seems reasonable, then it's definitely low-cost 3#-)

Otherwise, I find the LM7805T works quite well for a linear regulator
and ultimately, requires only a clip-on TO220 heatsink clip provided
that you're drawing no more than about 500mA from it.

Adios,
LarZ

---------------  TAMA - The Strongest Name in Drums  ---------------

{Original Message removed}

2001\07\17@101238 by Mark Newland

flavicon
face
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:

{Quote hidden}

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics


2001\07\17@111015 by Robert E. Griffith

flavicon
face
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 removed}

2001\07\17@125218 by John Ferrell

flavicon
face
Take a look at the voltage booster in this device.
www.uoguelph.ca/~antoon/gadgets/carnc12.htm
I stumbled onto this from another post on the piclist...

John Ferrell
6241 Phillippi Rd
Julian NC 27283
Phone: (336)685-9606
Dixie Competition Products
NSRCA 479 AMA 4190  W8CCW
"My Competition is Not My Enemy"



----- Original Message -----
From: "Robert E. Griffith" <spam_OUTbobTakeThisOuTspamJUNGA.COM>
To: <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU>
Sent: Tuesday, July 17, 2001 11:08 AM
Subject: Re: [EE]:Voltage Reg vs Switcher


{Quote hidden}

> {Original Message removed}

2001\07\18@052613 by mike

flavicon
face
On Tue, 17 Jul 2001 07:08:35 -0700, you wrote:

>Find a wall wart with a regulated 5V output and then use a boost convertor to
>get your LCD display voltage.
For most small LCDs, you can often use a simple charge pump (cheaper!)
{Quote hidden}

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2001\07\18@052618 by mike

flavicon
face
On Tue, 17 Jul 2001 11:08:41 -0400, you wrote:

>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.
For most small LCDs, you can often use a simple charge pump to boost
the 5V rail. If you can generate the drive waveform from the PIC (PWM
output or software toggle), the cost is just a  few diodes & caps -
pennies
>
>
>{Original Message removed}

2001\07\18@135410 by Peter L. Peres

picon face
You can always try to add a few resistors (to distribute the heat) in
series with the 7805. Place them around the board so the heat is
distributed. They should be sized such that the 7805 (or 340) sees 7V
input at maximum load (see data sheet for minimum input voltage).

hope this helps,

Peter

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


More... (looser matching)
- Last day of these posts
- In 2001 , 2002 only
- Today
- New search...