Breadboarded this with 1uF polymer caps a string of 1N5819s and an ICL7660 in DIP package
Do you have idea what and how switching frequency is managed in ICL7660?
I wonder also what about limiting switching current (eg. MPU pin)-I've rdawn this 330R by by mistake on VCC, but my intention was limit pin current somehow to lets say <20mA, so I've did another simulation with 330R on MPU pin, as well as I will try adjust (optimise) switching frequency based on caapcitance used and current limit resistor.
Quick calculation of RC constant for eg. 330R and 1uF, gives 330us for RC, so lets use 3RC time to delay (half period) toggling this PWM MPU pin and we'll see what happends.
In hand made simulation it looked like, when we wait anougth time to charge/discharge througth this 330R resistor than I've got decent results even with small load (100k resistor on mosfets gate to ensure OFF state when gate driver circuit not powered yet, etc).
What I mean-I looked like we have to adjust somehow this switching fequency to allow capacitor fully charge/discharge and inserting calculated delay based on RC constant is for the moment best idea, but having another spare MPU pin probably it could be done easier-just but enabling pin change interrupts, however in this case not sure what logic voltage levels will be for low/high (need to verify datasheet depending on MPU used and VCC), those threshold logic voltage levels will be above zero and less than VCC.
It is interesting how ICL7660 manages this switching-it has build in oscilator set to predefined frequency, or comparator to watch when this first stage capacitor is close to fully charged/discharged?
Anyway, ICL7660 probably cheaper than MPU so it might me interesting option too, I knew details how its swithing frequency is managed