Can we PWM an LED backlight on LCD module

[Demon]

From what I've seen so far, backlights on LCDs (often over 100mA) still consume a lot of current compared to the logic circuit (usually in single mA). I'd like to improve that.



Since LED backlights generally run on 5V without resistors (I'm assuming resistors are now built-in and cannot be "easily" disabled), I was thinking of running the backlight on 7 VDC, but with PWM.

Is there a reason why this wouldn't work just like it does for ordinary single LEDs?

In my feeble mind, LED is LED, shouldn't it act the same way?

[Ioannis]

Without knowing the specs of the LED's is not easy to say if it is OK to drive the LED string with 7V instead of with 5V as it was designed initially, even with PWM control.

Besides that PWM may stuck in the ON state and burn everything...

Ioannis

[Demon]

... PWM may stuck in the ON state and burn everything...

That is my biggest concern with this plan.


My design now has 3 enclosures, with power being fed into the center unit. I'm now thinking of using 3 separate voltage regulators; one per unit.

That way each 7805 doesn't get as hot as a single device trying to feed all three. Less complicated (less parts, simpler circuitry) than trying to "cheat the system" so to speak.

[Ioannis]

Why not use SMPS? No heat generated, no heatsink needed.

Unless you need a clean +5V for ADC purposes. In all my cases though, a switching did not make any difference in the ADC.

Ioannis

[Demon]

(post removed, because I can't tell the difference between a circuit that provides power to PIC, and a circuit that provides power while relying on PWM from a PIC)

[Demon]

I'm currently using these buck converters to drop from 12V from wall adapter down to 5V:

https://www.amazon.ca/gp/product/B0B5GQTS64/


These go for $2 each and they are only rated at max 3A with warning to remain under 2.5A.