# The Backlight **URL:** \ **Category:** Machine Design\ **Created:** [February 7, 2018, 10:40am UTC](https://forums.kinograph.cc/t/the-backlight/966 "2018-02-07T10:40:59Z")\ **Posts on this page:** 1\ **Showing post:** 136
**Author:** ![PM490](https://forums.kinograph.cc/user_avatar/forums.kinograph.cc/pm490/32/3176_2.png) [@PM490](https://forums.kinograph.cc/u/PM490)\ **Post date:** [April 23, 2023, 12:36pm UTC](https://forums.kinograph.cc/t/the-backlight/966/136 "2023-04-23T12:36:52Z")
Adding to @cpixip comments to provide nuance in regard to PWM controlled drivers. In an oversimplification, I would group these in three types. First ones, including the Mean Well, switch on/off the led based directly on the PWM control input, the current accross the LEDs will be close to a squarewave. The second group, are switching current regulators, also with PWM control input. On these, the current across the LED is typically in the form of a sawtooth wave. The Fentobuck is a good example of this configuration, here the [datasheet](https://cdn.sparkfun.com/assets/5/9/8/e/4/AL8860.pdf) for the IC, see IL representations in Page 10. Lastly, there may be some designs, that use a PWM control input for simplicity, but are providing a constant current. The drawback of this design is that to achieve constant current the PWM input is converted (low pass filtered) to a DC, which decreases the speed of control. My [first driver design](https://forums.kinograph.cc/t/another-led-driver-simple-scalable-controllable/2197) is based on this configuration, and this [video](https://www.youtube.com/watch?v=daHqoSEXuvA&t=16s) shows the controlling input (PWM) and the resulting DC output which controls the LED current. The convenience of a single wire for 16bit control is at the expense of a very slow response (low pass filter). The practical testing suggested by @cpixip is spot on. --- _[View the full topic](https://forums.kinograph.cc/t/the-backlight/966)._