David Duffy (AVD) wrote:
> For one of the projects we have on the go at present, I'm using a 78L05 
> regulator to drop the 24V incoming supply down to 5V for the PIC and 
> MAX1485. The board's relay is a low power 24V type, so only draws about 
> 8.5mA when energised.
> 
> With the 78L05, the idle current draw from the 24V supply was about 
> 4.7mA. Swapping it out for an LM2931-5 regulator dropped that to about 
> 1.4mA, quite an improvement as the relay is off most of the time.
> 
> That's good enough for this application, but it got me thinking about 
> the few wasted mA * 19V (24V - 5V) in the linear regulator. This design 
> is through hole, but had to be compact so I didn't even try to fit a 
> switching regulator in.
> 
> I chose 24V for low cable losses, as there are up to 70 devices on a 
> common power and data buss. Relays are easy and cheap to buy in 24V too.
> 
> Are there any small, low-current, hi-efficiency switching regulators out 
> there that are still reasonably priced? I realise that a 78L05 is hard 
> to beat price wise, but are there good alternatives out there?
> David...
> 

You can try this. http://www.romanblack.com/smps/smps.htm.

Cheers

Ravi

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