G=F6khan SEVER wrote:
> Hi everybody,
> =

> I've designed a small led luminarie board which has 5 rgb leds and 2 ICs
> (PIC12F675 and MAX-485) and bunch of smd resistors and caps on it. For the
> 24V to 5V conversation i've used simple 7805 regulator circuitry. (Two ca=
ps
> take part at the two side of 7805 regulator.) Actually previously I had u=
sed
> lm2575 (Simple switcher 1A step-down voltage regulator) plus two caps and
> one inductor with it for the 24v -> 5v power conversation stage.

If the power dissipated by a linear regulator is too much in your =

application, you should probably use a switcher.

> =

> The problem is when i've used 7805 with 24V input voltage it over-heats. I
> dont have enough space for a heat-sink. There werent any heat problems wh=
en
> i've used lm2575.  About one thousand of led pcbs were manufactured for t=
he
> 7805 part and we're in urgent decision stage for proper component selecti=
on.
> Do you know 7805 alternative that will work well on my circuit?

Any linear regulator will have the heat problem. The ideal linear =

regulator will still have to dissipate 19*(current) W. Switchers are not =

limited by that, and do not waste as much energy as heat.

If lm2575 worked, why not stick with that? Unless you can find a =

switcher that fits in the footprint of a 7805 (I don't think any exist, =

given that they all need a coil and some extra stuff), I doubt you can =

use those PCBs as is (without some workaround to replace the 7805 with a =

switcher)

-- =

Hector Martin (hector@marcansoft.com)
Public Key: http://www.marcansoft.com/hector.asc

-- =

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