On 1/16/2013 11:18 PM, David Duffy (AVD) wrote:
> I have the need to regulate the voltage going out to some LED strips.
> These strips are simple 12V DC types that have 3 LEDs and a resistor per
> section, repeating throughout the strip.
>
> The voltage available is nominally 12V, but can vary between 12V and
> 14V.  The ability to handle up to 18V input is also desired by the
> client.  The current draw of the LED load is approx 3 Amps.
>
> I was thinking of a simple 12V LDO, but at 2V differential that's 6
> Watts in heat - ouch!  Ideally this unit needs to run with minimal heat
> dissipation.  I also thought about a SEPIC converter, but that would
> take too long to design and debug and be overkill for this application.
>
> My next thought was to use a PIC12 to PWM a logic level MOSEFT and use
> the A2D in the PIC to sample the output voltage via an R/C network.  In
> theory this will allow me to regulate the output and even allow for a
> dimming function to be offered as an option.
>
> There are only 100 units to build initially and maybe some more after
> that, but not thousands.  A PIC based solution would be low parts count
> and fairly easily tweaked to my mind.  Does this sound like a reasonable
> solution?
> David...
>
This is really a stepdown regulated power supply project. You will need=20
a good MOSFET, a fast diode, an inductor, a low ESD capacitor, then a=20
pic10fxxx to drive everything. The PIC will charge the inductor, then=20
the inductor will charge an output capacitor according to the PIC's A/D=20
value. Another A/D input will have to be a reference voltage input, such=20
as two 1n4148's in series.

You might take a look at Roman Black's regulator, if I remember=20
correctly, it is very close to what you need.

-- Bob A

--=20
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