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Author Topic: Optimal PWM Frequency  (Read 2393 times)

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Offline bumba000Topic starter

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Optimal PWM Frequency
« on: October 21, 2015, 04:54:11 pm »
I would like to know if there is a calculator or a formula to figuring out the best PWM frequency and duty cycle for an inductor.

Thank You, John
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Online DimitriP

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Re: Optimal PWM Frequency
« Reply #1 on: October 21, 2015, 05:41:42 pm »
Post some numbers and what you are expecting the inductor to do with this PWM frequency or even better what you are expecting to do with this inductor.....
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   If three 100  Ohm resistors are connected in parallel, and in series with a 200 Ohm resistor, how many resistors do you have? 
 

Offline bumba000Topic starter

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Re: Optimal PWM Frequency
« Reply #2 on: October 21, 2015, 05:59:47 pm »
I've built a boost converter. See my schematic and parts list here https://www.eevblog.com/forum/beginners/boost-converter-vout-drops-with-load/

I have all the solder and trace routing kinks worked out. I want to run a 0.5ohm load at about 5V and 10A from the 18650 battery. I'm having a good bit of success around 22.5khz but I'm sure it could be better. I can only seem to find calculators and formulas to figure out what frequency we're producing as apposed to what frequency we should be producing.

Thank you, John
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Offline bumba000Topic starter

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Re: Optimal PWM Frequency
« Reply #3 on: October 21, 2015, 07:44:48 pm »
I found out about partsim.com and that too is going to take a bit of learning. I've started a spreadsheet and have begun tracking my results. I'm finding so far that as Vin changes so must the duty cycle and the frequency. This is going to be quite a task, but I'm up for it.

John
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Offline bumba000Topic starter

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Re: Optimal PWM Frequency
« Reply #4 on: October 21, 2015, 08:21:15 pm »
Thank you. You've just made this a whole lot easier on me. I'll still have to do some testing and tracking to find the optimal frequency, but so far 25kHz is doing pretty well. I'm waiting on batteries to recharge now.
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Offline bumba000Topic starter

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Re: Optimal PWM Frequency
« Reply #5 on: October 21, 2015, 08:37:26 pm »
Thanks again. I've had other recommendations in the 30khz to 40khz range at 28% duty cycle. I have spoken with the engineer of the inductor and he tells me that its happy anywhere from 1khz to 1mhz. So, I like and appreciate what you say.

While I'm waiting for batteries to charge I've decided to try using an old HP 379349-001 atx power supply to make an adjustable power supply. I have a few potentiometers and LM317T's here to work with. If you're already seeing a problem with this please let me know. I'm going on pizza break now.

Thanks again, John
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Offline xwarp

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Re: Optimal PWM Frequency
« Reply #6 on: October 23, 2015, 08:47:22 am »
Just curious, is all this to run an atomizer coil for an e-cigarette?
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