PWM vs runtime?

[Haz]

What is the relationship with PWM and runtime?

Would higher PWM mean shorter runtime compared to lower PWM?

Is there are any reduction, is it significant, or very negligible difference?

I guess the reason I'm asking is that some manufacturers still use low PWM that is still detectable with the human eye, when the light is waved around just a little. What is the purpose?, cost, runtime?, Why not just go for the higher PWM, 1,000Hz for example, so it's not so easily detectable with the human eye.

Thanks

Haz

 

[Th232]

Can't speak for all drivers, but from a couple of datasheets I've seen (one being the LT3475), a higher switching frequency increases switching losses, but increases the maximum duty cycle and allows you to use smaller inductors.

Seems to me that the first and third reasons will be applicable to all PWM, unsure about the second though.

 

[TorchBoy]

Haz, when you talk of "higher PWM" do you mean a higher frequency? I note that LEDs are normally most efficient at 0 Hz (the main exception being very low drive currents).

 

[HKJ]

What is the relationship with PWM and runtime?

Would higher PWM mean shorter runtime compared to lower PWM?

Changing the pwm frequency from 100 hz to 1000 hz does not have to affect runtime, but it will depend on the driver.

Look at the trace from a pwm driver, each time the pwm goes on, the driver uses some time on stabilizing the current, this kind of design has a limit on how high pwm frequency that it can use. Use to high frequency and the driver will never stabilize the current.

 

[kaichu dento]

Welcome topic here!