How does LED PWM dimming work?

effexxess

effexxess

Well-Known Member
How does dimming work on an LED panel? Does the power supply voltage drop like analog incandescents? Or does the supply get chopped up like I've read with PWM? I'm interested in constant current output but PWM adjusted duty cycle coming out of a power driver. Is this even such a thing and who makes them?
 
effexxess

effexxess

Well-Known Member
I also came across this technical note (https://www.upowertek.com/what-is-pwm-dimming/) about Fake PWM Dimming, which I think is what I'm getting confused about.

Real PWM Dimming
In the real PWM dimming, the LED currents turn on and off at the designated frequency and duty cycle. There is a microcontroller(MCU) inside the driver. The presence of the MCU enables the PWM signal to detect peak voltages. Real PWM dimming allows a broader range of PWM frequency.
A significant positive with the real PWM dimming is its ability to preserve the white point of the LED output. It also permits a high level of the reference voltage, which is above offset errors. All uPowerTek drivers integrate MCU to work with PWM dimming.
Users need to choose PWM dimming mode in the driver programming software.
Click to expand...
Click to expand...
Would this still be constant current?
 
L

Lou66

Well-Known Member
Depends on the driver. Some drop the current others modulate the current with a PWM. Look at the datasheet of the driver. Both can use a PWM as data signal.

Especially with high CRI white leds the spectrum depends on the drive current. There you don't want to drop the current but use a PWM modulated output. Then the color/spectrum stays constant when dimming.
 
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