In an application, 100+, 100W 24V halogen lamps need to be individually controlled and run simultaneously. They stay on for a few seconds at a time and need to have very constant irradiation.
Furthermore, It needs to be as cheap as possible, but have fine control of the lamp with at least in the 0.5% granularity of the maximum power output.
This system is enclosed and is for lab use.
The first attempt was to rectify and filter main (230VAC) and use a DC/DC buck converter to go from 300VDC rectified to 24VDC being controlled by a dsPIC33.
However, I miscalculated the inductor required and the main issue is, with the correct inductor, the Duty cycle of about 8% which at a frequency of 20kHz only leaves very large granularity for the speed of the dsPIC to generate the PWM.
Another option is to have a large (or several) AC/DC supply to go from the main to 25V or so and then a buck on each lamp, but that would increase the cost significantly, about 2-3k$ for the supplies and large currents will have to be handled.
Is there a cheap, more appropriate topology for this need, or is there a way to increase the nominal buck duty cycle without wasting power and having reasonably sized coil ?
Perhaps a possibility would be to have directly 230VAC and regulate the lamp directly with a Triac although the ripple would be too big at 50 (100Hz) so there would need some sort of circuit behind as well.
Someone came up with the idea of using lead-acid batteries which would lead to the use of a much smaller power supply and drive the lamp directly in PWM without buck, not sure about EMI and cold start.