piclist 2002\09\06\150456a >
Thread: [EE:] Driving a 15W LED?
www.piclist.com/techref/microchip/devices.htm?key=pic
picon face BY : Harold M Hallikainen email (remove spam text)



On Sat, 7 Sep 2002 04:42:04 +1000 Roman Black <spamBeGonefastvidSTOPspamspamEZY.NET.AU>
writes:
{Quote hidden}

       THANKS Roman! I've been reviewing your simple SMPS page. Nice! Are you
suggesting using the comparator (and sense resistor) to make sure we
don't go over a maximum switch current, but regulating the output using
the PIC's PWM output? Relying purely on the PWM could result in the
switch current taking off if something goes wrong, so limiting duty cycle
based on a maximum measured switch current seems appropriate. I still
need to adjust the switch duty cycle based on the LED current. I'm
thinking A/D there, but are you suggesting use of a comparator there?
Perhaps ramp up duty cycle until the comparator trips, then ramp down
until it "untrips"?
       Anyone know of a simple current to voltage converter chip with an
accurate built-in shunt? Maxim (I think it is) has some that are +/-7A
with PWM output. Interesting parts.

Harold


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