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Solution for 12V HB LED driver

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dz99

dz99

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12V HB led driver

Hi All!

I would like to design a led tail/brake light for car. I've selected this kind of IC: **broken link removed**

The problem is, I need to drive each 5 leds series (assuming 1.85 nominal voltage @20mA) and with 30 or more leds it is highly impractical/costly.

What does the experts do? 12V to 70V PWM step up, and then current limiting?
35x1.9V = 66.5 V

Or do it by parallel led connecting with constant voltage? -> the spreading of each leds U-I characteristic will result in inhomogeneous lightning.

So it is a good question! :)
 

Re: 12V HB led driver

If you want to drive more 30 LEDs I think you should make 3 string of 10 LEDs in parallel instead of 30 LEDs in series. You can refer ACT6358 of Active-semi.Inc. It has 1A peak current limit. To make the current in each string match to each other, you need to use some external device to make current mirror.

BR,
 

    dz99

    dz99

    Points: 2
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Re: 12V HB led driver

dz99 said:
I would like to design a led tail/brake light for car. I've selected this kind of IC: **broken link removed**

The problem is, I need to drive each 5 leds series (assuming 1.85 nominal voltage @20mA) and with 30 or more leds it is highly impractical/costly.

What does the experts do? 12V to 70V PWM step up, and then current limiting?
35x1.9V = 66.5 V

Or do it by parallel led connecting with constant voltage? -> the spreading of each leds U-I characteristic will result in inhomogeneous lightning.

So it is a good question! :)
Click to expand...

Try this circuit.

R1 sets the constant current for the whole chains in parallel.

R2 and R3 will be small values to share the currents if there are any imbalances between strings.

Cheers

Ravi
 

    dz99

    dz99

    Points: 2
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