12 V regulator

[rr]

With the input voltage requirements spanning above and below
the output voltage requirements, the only regulator that will
operate correctly is a switching buck-boost combination.

BobR.


Steve.Flanagan at VerizonWireless.com wrote:

> I have a requirement for 12 V regulation (+/- 15% or a range of 10.2 to 13.8
> volts).
>
> My application is driving several 12V time delay relays (TDRs) and I am
> building it to work in a drag car that can be powered with 12v + Alternator
> or a 16V system.  Keep in mind that with the 16V system, the battery charger
> can put over 18V's.
>
> The TDRs pull as low as 1 ma each when in the off state, and as high as 200
> ma each when the relay is triggered.   So lets just say my requirements for
> a regulator are:
>
> Input Voltage:  10v to 20v
> Output Voltage: 12v (+/- 15%)
> Output Current: 1mA to 500mA
>
> I tried to use a 12V regulator purchased from Digikey just as a test and it
> seems to crap out at the lower current levels (I don't have the part number
> handy, its at home, and this was a project I was working on over a year ago,
> something just stirred up my memory that I never was able to resolve this.
> Originally I was not aware of the lower current levels, so the regulator I
> purchased worked in the 100ma range, but not at lower (1ma) range.
>
> Could someone recommend a very reliable 12V regulator that I can use to meet
> my needs.
>
> As a work around I built my own regulator with a 12 V zener, resistor and
> 2n2222 transistor that seems to work, however, I am concerned about the
> reliability and heat issues with the 2n2222.
>
> Thanks,
>
> Steve F
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