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Driving LED strips with the TLC59711
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Driving LED strips with the TLC59711

by sunst0ne on Mon Aug 19, 2019 3:54 pm

I am having that classic electronics n00b problem of having bought half the parts before realizing a design problem.

I am hoping to drive some 24V analog LED strips with the TLC59711. I understand this is not an ideal setup, because the TLC59711 is intended as a constant current source (?). I do however want one of the features specifically provided by the TLC59711: it's a lighting-specific PWM chip, it chops up the PWM such that visible flicker isn't a problem at very low duty cycles. I want to dim/control my LED strips with the absolute minimum possible perceptible flicker, even (especially) for people who are highly sensitive to flicker.

So what I'm asking is: how would I best drive my LED strips with the TLC59711, *or* what is another IC that will drive the strips with similarly low flicker which can be controlled by a Raspberry Pi (e.g. by SPI or similar)?

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Re: Driving LED strips with the TLC59711

by XRAD on Tue Aug 20, 2019 9:18 am

Sounds like a cool project. 400hz and gamma correction should get you where you need to be....

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Re: Driving LED strips with the TLC59711

by adafruit_support_bill on Tue Aug 20, 2019 9:43 am

The TLC59711 can't drive the strips directly. But you can use it for the PWM control and add some MOSFET drivers.

See Mike's circuit diagram here: viewtopic.php?f=19&t=95187&p=478044

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Re: Driving LED strips with the TLC59711

by sunst0ne on Fri Aug 23, 2019 11:23 am

Thank you so much for this information. I'm very new to electronics - is the symbol in his diagram just a standard N-channel MOSFET? And I would control it with any PNP transistor off the shelf that has the right ratings?

Including the diagram below in case anyone needs it.

Image

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Re: Driving LED strips with the TLC59711

by adafruit_support_bill on Fri Aug 23, 2019 12:24 pm

The PNP is not too critical. It is just driving the gate of the MOSFET, so current will be minimal.
https://www.adafruit.com/product/3598


The N-channel MOSFET should be one with a fairly low gate threshold. Many need 10v or more to fully turn on. These are optimized for operation with 5v logic levels, and can easily handle high current loads like LED strips.
https://www.adafruit.com/product/355

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Re: Driving LED strips with the TLC59711

by sunst0ne on Fri Aug 23, 2019 4:13 pm

Thank you again! If I use a IRFZ44N for the MOSFET, it won't blow up right... just get a bit hotter for the same amount of current going thru the LED strips?

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Re: Driving LED strips with the TLC59711

by adafruit_support_bill on Sat Aug 24, 2019 7:08 am

That one looks like it should work OK for you.

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