Boost -> Microcontroller or Microcontroller -> Boost?

[legtu]

i have a couple of microcontrolled, multi-level PWM amc7135 "regulators" and i'm planning on adding them to a couple of lights which have boost circuits.

if light 1 has an input voltage range of 2.4v to 3v, should i put the PWM controller before or after the boost circuit?

if light 2 has a boost/buck circuit running on a lithium primary(3v) or rechargeable(4.2v), should i put the PWM controller before or after the boost circuit?

thanks for any inputs.

 

[legtu]

Anyone?

Looking at DX or KD multimode drivers, those with boost seems to be setup as boost circuit->microcontroller.

 

[VidPro]

owww, you hurt my head
so you have a current control device that can end up having harmonic shift if fed with a chopped DC input, and on that device it has a DC choped output, and your going to feed that to a booster that will sort of purposfully make chopped DC to pump up the voltage for boosting.

i go with PWM/linreg before booster.
PWM only after Boost
PWM after buck, although i have starved a buck and it lowers output, so the buck would be more flexable in that respect, BUT the Linear regulator is sort of a buck type device already, and it is no wonder why my head hurts :wave:

that just leaves if it acts like any of them older drivers that failed when the output was unloaded, for those your lin regulator pwm would be first always.

at any rate "unexpected results" could possibly be countered by using a capacitor (storage device) at an output of one before heading into another, to turn the chopping back into a solid(er) DC to be messed with by the next item.

if you only needed the PWM itself, then toss the regulators by removing them and shorting across the I/O (but not the gate thing) or just buy a PWM only board, the dimm2Dimm used to do that, and now there is another that is a PWM only board. then that goes after the boost, before the LED and still will depend on the boost type.

 

[TorchBoy]

i go with PWM/linreg before booster.

Unfortunately the AMC7135 wants 2.7 V minimum, and if it has a polarity protection diode that takes it to 3.3 V. Using a capacitor sounds like a good idea.