High Frequency PWM dimming of LEDs is OK?

Hello,

We are wanting to do high frequency PWM dimming of the output of Resonant Inductive Couplers (which feed LED lamps) hooked up to a twisted pair bus.
Do you think the “gap toothy” resulting waveform (see below) will be a cause of any problems?

(This is a different question on a subject discussed elsewhere here, needing a new thread due to new diagramatic info here)

Block diagram………………..
https://i46.tinypic.com/28151kz.jpg

….you can see the “shorting FETs which dim by stopping current flowing to the LEDs when the FETs are ON.
(-please ignore the number of secondary turns....as you know, there is a resonant coupling method)

We do NOT want to do low frequency PWM dimming, (~200Hz) because the low frequency of this dimming causes problems for the current source. (-it means the current source is switching from high power to low power output which causes problems)

Therefore, we wish to do dimming at a much higher frequency (83.3KHz). But do you think that the resulting current waveform (as below, when D is not equal to 1) is going to mean problems?


LED lamp current with no dimming (D = 1)
https://i47.tinypic.com/o9iv.jpg


LED lamp current with dimming with D = 0.083
https://i48.tinypic.com/3ctas.jpg


LED lamp current with dimming with D = 0.33
https://i50.tinypic.com/1zofdzp.jpg

LED lamp current with dimming with D = 0.92
https://i49.tinypic.com/np5d91.jpg


(Also, how would you reduce dissipation in the current source by correcting the power factor in the twisted pair?)


Resonant inductive coupling…………
https://en.wikipedia.org/wiki/Resonant_inductive_coupling

I think you have to answer the last question first. What is the voltage and current in the primary?

In the actual system the current in the primary is fixed 2.9 Amps AC 50KHz sinusoidal

If I understand correctly the primary is a single wire. If so what is the voltage of the primary and what is the load on it?

the theory behind the couplers is "resonant inductive coupling"

https://en.wikipedia.org/wiki/Resonant_inductive_coupling

Maybe, but the frequency is wrong - see your other thread. It would help to know the answer to post 4. Perhaps it is just a single wire driven from a current source?

Perhaps it is just a single wire driven from a current source?

Click to expand...

This is the basic situation..but please ignore the detail of the turns in the coupler......this is where the top secret stuff comes into it.

https://i46.tinypic.com/28151kz.jpg


...As you say, it is pretty much a single wire driven by a current source