PWM drivers? Help me please.

Hey,

I got a little technical question. If a PWM driver on 100% is direct drive, 50% LED brightness would be achieved by pulsating the voltage to achieve the correct amount of average voltage. What happens if my batteries are so depleted that my direct drive mode is basically as bright as the 50% was with full batteries? Will the 50% mode then be the same as DD or will it be 50% lower than the 50% mode was initially with full batteries?
I'm asking specifically about Vinh's drivers (DriverVN) to understand how they react to depleting batteries.

LichtAn! said:

Hey,

I got a little technical question. If a PWM driver on 100% is direct drive, 50% LED brightness would be achieved by pulsating the voltage to achieve the correct amount of average voltage. What happens if my batteries are so depleted that my direct drive mode is basically as bright as the 50% was with full batteries? Will the 50% mode then be the same as DD or will it be 50% lower than the 50% mode was initially with full batteries?

I'm asking specifically about Vinh's drivers (DriverVN) to understand how they react to depleting batteries.

Click to expand...

I'm not that familiar with Vinh's drivers but technically, I'll take a stab at your question.

If there is no current limiting going on for each pulse..........in other words, the current through the LED is limited by the batteries capability..........then yes depleted batteries will not be able to source as much current and direct drive could look as bright as a 50% duty cycle with fresh batteries. That also means that at a 50% duty cycle, it will look proportionally less bright.........say equal to 25% duty cycle with fresh batteries. Those are just rough numbers to illustrate.

If there is current limiting going on for each pulse that represents less current than if just shorting a battery across an LED, then you will get a point further down the batteries voltage discharge value before the exact same scenario will happen.