LED Driver Short Circuit Protection

Thread Starter

digital_ade

Joined Sep 19, 2016
7
Hi Folks,

I am looking for your feedback on a circuit protection methodology for a LED driver circuits using a BCR321 constant current driver.

The LED array that gets connected to this circuit has exposed solder points, and they frequently get shorted to an instrument housing which destroys the LED driver and also seems to cause random damage to the micro controllers (Atmel Xmega128A3U) that is driving the PWM to the BCR321.

I had two ideas for providing some protection.

1. Adding a forward diode on the PWM line to prevent any current flowing back to the micro.
2. Adding a current limiting resistor (fusistor) in line on the power side of the BCR321 where it is driving the LED array.

What are your thoughts?

Do you think that adding a forward diode on the PWM line will provide protection and will it interfere with my PWM signal.

Do you think that adding a passive component like a fusistor on my PWM output will effect these the LED array?

I have attached a schematic of the LED driver circuit. Signal LED_TOP is the PWM connected directly to the Microcontroller pin.

The BAS3007A is in place to provide reverse polarity protection and is exactly as specified in the BCR321 app note.

The PWM from the MCU is running at 15.85KHz

Looking forward to any feedback or suggestions you may have.

Many thanks
A.
 

Attachments

Delta prime

Joined Nov 15, 2019
326
circuit has exposed solder points, and they frequently get shorted to an instrument housing which destroys the LED driver and also seems to cause random damage to the micro controllers (Atmel Xmega128A3U) that is driving the PWM to the BCR321
I would put my attention on the exposed solder points!
 

pmd34

Joined Feb 22, 2014
503
The diode should protect the MC as you suggest as it will prevent power going back into it if the LED driver damages.
You could use a "resettable fuse" instead of current limiting resistor however. But as Delta prime suggests.. prevention is better than cure!
 

Thread Starter

digital_ade

Joined Sep 19, 2016
7
Hi both,

thanks for the feedback. The exposed solder pads on the LED array are outside of my control - they are an external component specified by the client. Needless to say I am keen to improve on this component in the system.

I will experiment with a PPTC and a forward diode on the PWM line.

many thanks.
A.
 

DickCappels

Joined Aug 21, 2008
6,374
1580465628376.png
It is a constant current power supply chip, so provided there is adequate heatsinking it would not be harmed by a short to ground.
 
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