VND600sp

Iyolc.1 · ‎2020-10-21

Good morning all. I hope you are well.

My quest is for the VND600-SP

I am using this power switch for the LED drive.

I drive LEDs using the Pwm signal for dimming the power of the leds.

I use 1 khz frenquence input f the vnd600-sp

Problems arise in this situation. The VND600-sp gets very hot.

About 90 centergrad. Is this temperature normal? or this power switch is not compatible with using pwm.

I am waiting for your answer.

Sincerely thank you

Peter BENSCH · ‎2020-10-26

LED power: supplied by a current source or voltage source?

Value of LED channel current?

According to your scope picture max string voltage is 12V?

What is the duty cycle range in which you want to dim the LEDs?

What happens if you reduce the PWM frequency to e.g. 100Hz?

BTW: are there important reasons, not to use e.g. a MOSFET instead of a high side switch to drive an LED?

/Peter

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Iyolc.1 · ‎2020-10-27

Hi Peter,

Thank you for answering my question

I'll try to answer your questions as best I can.

ED power: supplied by a current source or voltage source?

I use this ecu in the ambulance vehicle,

My power source is the engine alternator, so it's a source of voltage.

Value of LED channel current?

In the vehicle, I use 2 LED strip, one 3 meters long and the other 2.5 meters long.

The 3 meter led strip consumes 6.4 amps and 2.5 meter consumes 5.4 amps.

According to your scope picture max string voltage is 12V?

In the vehicle, the voltage is 14,4V

What is the duty cycle range in which you want to dim the LEDs?

For dimming the led, we have 4 dim different dim level.

first level is %20
second level is %30
third level is %50
fourth level is %100

At the first photos you can see the first and third dim level duty-cycle

What happens if you reduce the PWM frequency to e.g. 100Hz?

I am not sure what happen for instant. When ı will try ı will reply in this post.

BTW: are there important reasons, not to use e.g. a MOSFET instead of a high side switch to drive an LED?

I think it will be good to use VND600-SP in the vehicle.

https://www.st.com/content/st_com/en/products/automotive-analog-and-power/high-and-low-side-drivers-switches/high-side-switches/vnd600sp-e.html

Peter BENSCH · ‎2020-11-02

Any news on this?

The oscillogram doesn't look really good. The PWM frequency is 996Hz but it shows fairly flat edges which is a linear range and usually causes a lot of power dissipation which leads to the heating of the drivers.

How are the LED stripes internally connected (number of LEDs and current limitation)?

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