EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: kasunch on April 29, 2016, 11:36:53 am
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Hi,
I am trying to design a high current (about 700 mA) LED driver which is capable of PWM dimming. The LED driver should support higher PWM frequencies as high as 1 MHz. The purpose of higher PWM frequencies is to use LEDs as a data communication method as well as lighting.
I tried a simple constant current driver using a simple liner regulator (LM350T) together with an external MOSFET. The liner regulator wastes lot of energy as heat on high input voltages in addition to the current sense resister. I also came to know that these kind of liner regulators also have a limitation on transient response time with higher frequencies.
Then I looked at available switching LED drivers such as buck-boost drivers. However, supported maximum PWM frequency of them is below 100 kHz for almost all of them (looks like this is due to their switching frequency is below 2 MHz).
I appreciate it very much if you can give some pointers for achieving higher PWM frequencies.
Thanks.
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Yeah, I don't think you're going to find anything off the shelf. A quick google shows a couple of papers on LED drivers that use GaN power stages to achieve switching frequencies in the 10+ MHz range, but I don't believe there are any integrated commercial solutions yet. Parts that use Si power stages are going to top out at 1-2MHz, as you've seen. You might be able to roll your own higher frequency converter using a GaN power stage, but getting it to operate properly at such high frequencies will not be a simple task.
A much easier solution is probably to do a switching pre-regulator in constant voltage mode with a hefty output capacitor and a linear constant current stage following it.