Electronics > Beginners
Capacitive Reactance, Inductive Reactance, Power Factor, Switching Hz
TheDood:
--- Quote from: MagicSmoker on December 14, 2019, 02:06:55 pm ---
--- Quote from: TheDood on December 13, 2019, 12:04:35 pm ---...The only way that I can see of maintaining the current flow I had before implementing the VFPFC, is by increasing the VAC input...
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Increase the value of C1 - it is acting as a "lossless" current limiter due its capacitive reactance. This reactance, in Ohms, is found using the classic formula: 1/(2*Pi*f*C) where f is in Hz and C is in Farads.
12.2uF gives a reactance of approximately 217 ohms which will limit current into a short circuit of 0.55A when supplied by 120Vrms (remember to use the RMS value of the AC voltage here). Note that the higher the voltage drop of the LED string the lower the current the capacitor will let through since it is the difference in voltage between the (rectified) source and LED string that is dropped across the capacitor.
Making this kind of circuit dimmable with a conventional triac-based dimmer is nightmarish. There's probably some specialized ICs already on the market that enable this functionality, but I leave it to you to do that research.
In the meantime, I attached an LTSpice simulation of a rectifier + valley fill PFC + LED load circuit that simulates just fine and rather quickly, even with the alternate solver. I did not take any care in selecting components to leave you with something to do, but it gives you a good - and working - starting point.
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That's awesome, thanks, I appreciate it, I'll look it over and see what I can see, you've been very helpful.
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