Shunt FET PWM dimming

Lighting Solutions
1

Do any of the LED drivers (e.g. MP2410 or MP2341) support high frequency dimming using a shunt FET?

Apparently there can be an issue with overshoot in output current when the FET turns on, but the technique works with a fair number of drivers.

Thanks for any insight!

2

Any more information I can provide here?

3

Doubt that the MP2410 will do it, it features short circuit protection, you need a part that will pump the full current into a short. They may not even know what you are speaking of, perhaps share a snippet of your proposed schematic.

4

Ah, fascinating, thanks for the reply! Do you have a favorite part (or any suggestions) for using with this technique?

5

Hi Elan,
Some of the LED drivers have the FET integrated,

Here is one with an external shunt FET:
MP24894 | 6V-60V input Buck WLED Controller with Hysteretic Control , DC and PWM Dimming Control | MPS (monolithicpower.com)

Regards,
Nouman

6

thank you for the reply! that shows an external FET but it doesn’t appear to be a shunt FET, which is driven by PWM signal, connected in parallel with the LEDs (so essentially shorting them when active).

7

MPQ2489 might do it, doesn’t seem to have any smarts to get in the way of shorting the load

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