STCS05 for LCD backlight control

ETogn.1 · ‎2022-03-29

Good morning, I am thinking to drive a LCD backlight with ic STCS05 and to control it with enable and pwm signal from a cpu. Led driving voltage of leds matrix of my LCD is 16.5V with 140 mA typical current (see picture attached). Do I have to supply STCS05 and led with a regulated 16.5V power supply (Vin in attached picture)? Thanks in advance. Best Regards. Enrico

Peter BENSCH · ‎2022-03-30

Perhaps I should add that you should not make the supply voltage unnecessarily large, because the differential voltage to the LED matrix must be burnt out linearly (--> heating). Try to provide a VCC of 1...3V above the LED voltage, the smaller, the lower the losses at the STCS05.

Regards

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

View solution in original post

Peter BENSCH · ‎2022-03-30

Welcome, @ETogn.1, to the community!

You can drive the matrix of the backlight LEDs directly with the STCS05, which does not need an extra VCC regulated to 16.5V, but only any supply voltage up to a maximum of 40V.

Regards

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

ETogn.1 · ‎2022-03-30

Wow...Thanks for your fast reply!

Do you have any EMI/EMC suggests for tipical application?

Enrico

Peter BENSCH · ‎2022-03-30

Without PWM, the STCS05 is a linear constant current LED driver.

Problems with EMC only arise when the brightness has to be adjusted using PWM. In this case, the entire LED matrix acts as a transmitting antenna and radiates the PWM. Hints for reducing interference radiation always depend on the respective circumstances and are therefore difficult to generalise.

There are plenty of application notes on EMC on our website, just search for EMC, select tab Resources and then tick Application Notes on the left.

Does it answer your question?

Regards

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

Peter BENSCH · ‎2022-03-30

Perhaps I should add that you should not make the supply voltage unnecessarily large, because the differential voltage to the LED matrix must be burnt out linearly (--> heating). Try to provide a VCC of 1...3V above the LED voltage, the smaller, the lower the losses at the STCS05.

Regards

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

ETogn.1 · ‎2022-03-30

Hi Peter,

I have all the answers :beaming_face_with_smiling_eyes:

Have a good day

Enrico

Peter BENSCH · ‎2022-03-30

Great!

If the problem is resolved, please mark this topic as answered by selecting Select as best under your favourite answer. This will help other users find that answer faster.

Good luck!

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.