I am working on a design for a 16 channel LED driver design. at the moment the basic design is based on three main components:
the Circuit needs to initially drive a 110V led Light with 250mA LED strings but wants to be adjustable to driver sets of other LEDs e.g Ledengin LZ7
without further components i think this design should work in principle with M1 getting a RDS(on) of ~30 mOhm (other similar mosfets had larger RDS(on)). the RDS(on) can be reduced further if i can supply higher voltage (14.1 mOhm at 6V and 12.6 at 10V)
(this combination of R2, M1 Q1 R2 and D1..n are repeated for each channel though R1 will be varied dependent on different D1..n on each channel)
the PCA9685 can supply limited current of 10mA per channel and if im reading it right 25mA total and can operate PWM at upto 1526 Hz
some simulation at 1526Hz PWM (assuming i did it right) shows if i have R2 with 10K resistor i get inrush current of 500uA which should be no issue
if i reduce r2 to 1k i get 5mA which is likely too large to operate more than 4 channels at once
and 100 gets 50mA which too large for a single channel and the PCA9685.
How do i determine the best value for R2?
Would the inefficiency of resulting from a large R2 make it worth putting in a gate driver e.g a MAX620EWN+ (would need 4) or a cheaper alternative?
or is there another, cost effective?, way to make this more efficient?
simulation model and output( the New macro are a PLW7070GA spice model)