#832

Рет қаралды 6,212

3 жыл бұрын

Episode 832
A look at the ring waveform of a self oscillating inductor used in a boost conversion circuit. Inductors have built-in capacitors.
Update: there is about 375pf of capacitance in FET drain source. This is larger than the capacitance of the inductor. I did a test where I used a relay instead of the transistor (so no extra capacitance). The ring went from 440khz to 1.4MHz. so there is still self capacitance but much lower capacitance than first thought. Thanks to several viewers that pointed this out.
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Пікірлер: 44

@engineereuler1762 Жыл бұрын

the capacitors' ratio is the square of that of the frequencies, so in this case, the inductor's internal capacitance is 1/25 and not 1/5 of the 10n, and that is 400pf

@robinbrowne5419 10 ай бұрын

True. The formula is FreqResonance = 1 / (2 * pi * sqrt(L * C))

@TheElectronicDilettante Жыл бұрын

Super cool. As you added load the waveform started to resemble the wave form of the secondary ignition firing a spark plug in an internal combustion engine.

@theinnovati0nlab782 4 ай бұрын

Very nice video! Thanks a lot. I am currently building a custom DC to DC boost converter and running through all the necessary calculations and measurements.

@ivanpopovic9503 10 ай бұрын

Primary resonant capacitance in your circuit is the output capacitance of mosfet since it is in order od nFs, and self capacitance of a 330uH coil is in order od pFs. It is easy to fool yourself when in analyzing the circuit one accepts all the parts of a test circuit but DUT itself, ideal. :) Also selfresonance between the inductance and mosfet output capacitance is used in PSM inverters to obtain zero voltage switching and enhance efficiency/reduce EMI.

@shawncalderon4950 3 ай бұрын

Nicely done!

@magnuswootton6181 Жыл бұрын

good for converting your boost.

@gauravsingh324 Жыл бұрын

Mark. The resonant frequency depends on square root of parallel cap. So if the frequency changes by order of 5 then I would guess the cap changed by order of 25. So the parasitic cap must be about C_external/25 ?

@engineereuler1762 Жыл бұрын

sorry, repeated your comment before reading through all comments

@Forensic1Man 3 жыл бұрын

Mark, It would be an interesting video for all if you could now go from this small "Tank-Circuit" demonstration and next show the viewers how you can make a tank-circuit for AM radio reception. You would go from theory to a practical application of electronics that people can build. AM tank-circuits can really pull in distance AM radio signals and these antennas are like magic with no wire connections to the radio!

@bobdoritique7347 Жыл бұрын

Merci for this video.

@pyrokinetikrlz 3 жыл бұрын

Great video! There is also parasitic inductance in capacitors (created mostly by large legs). It would be great to see how bad is that inductance in a small capacitor with large legs!

@IMSAIGuy 3 жыл бұрын

Here is a video for inductance in resistors: kzfaq.info/get/bejne/pr6aebZjss7ZoX0.html

@ryanjoyce88 4 ай бұрын

great explanation of the ringing, that makes sense, but what causes the overshoot at the start of the square waves, as seen at 9:50?

@tripplefives1402 6 ай бұрын

That's because everything has capacitance, inductance, and resistance.

@AllElectronicsChannel 3 жыл бұрын

Nice! I'm just recording a video about self resonance in capacitors. You can get a better measurement of the inductor's self resonance using your VNA or SA with tracking generator. Make a jig with the inductor in series, using S21. 😁😁

@IMSAIGuy 3 жыл бұрын

kzfaq.info/get/bejne/fMifh5SluNnYnJ8.html

@AllElectronicsChannel 3 жыл бұрын

@@IMSAIGuy Nice!! For parallel resonance the coax to environment transition will degrade more the measurement than for shunt resonance, I think

@IMSAIGuy 3 жыл бұрын

of course the granddaddy of self resonance is the crystal.

@NotMarkKnopfler 3 жыл бұрын

Thanks for this! Very interesting. Does anybody know (it wasn't clear to me from watching the video) - looking at the oscillation waveform of the inductor, is the centre line 0 volts? So... in other words, does the inductor effectively produce an AC output, which (in this particular circuit) is being half-wave rectified by the in-line diode? I need to learn more about inductors and do some experiments with them. Also, many thanks for the interesting tip about the transistor - that's a great part!

@IMSAIGuy 3 жыл бұрын

No, the ringing has nothing to due with that. I did a two part series that might help you: kzfaq.info/get/bejne/b8h2ibeSnaypfWg.html

@Wayde-VA3NCA 3 жыл бұрын

Are there any considerations on what resonant frequency would be preferred from a converter efficiency point of view? Ie. would tuning in a higher or lower res. freq be preferred? Or maybe just considerations of what freq might radiate emissions and cause interference?

@IMSAIGuy 3 жыл бұрын

There are many considerations and I am not the person to ask. If you go to Kiss Analog channel, he just reviewed a book on that subject.

@Wayde-VA3NCA 3 жыл бұрын

Thanks@@IMSAIGuy , I'll take a look. Thanks for your videos, I learn a lot!

@TonyBarr99 3 жыл бұрын

The filter capacitors of a power supply don't have an inductor or resister to form a LC or RC low pass filter. What is the other element that allows the 100 Hz or 120 Hz rectified current to be filtered out?

@IMSAIGuy 3 жыл бұрын

Are you talking about a linear supply? The ripple? The ripple is controlled with the bulk capacitor value and then the regulator circuit which follows.

@ats89117 3 жыл бұрын

Part of the parasitic capacitance is associated with the drain-gate junction of the transistor while it is turned off. I think if you ground the transistor's gate and source, you may be able to measure this with an LCR. Or I could look it up on the transistor's spec sheet if I wasn't so lazy! ;-)

@IMSAIGuy 3 жыл бұрын

read the description update

@mohammadrezamajidimosleh7917 3 жыл бұрын

First, I want to thank you for your helpful demonstration of boost converter. The ringing is caused by inductance and combination of any parasitic capacitances in the circuit. That includes power MOSFET parasitic capacitances as well. In circuits with high current low voltage MOSFETs, the dominant parasitic capacitance is likely to be MOSFET itself which may have as high as 1 nF capacitance for a typical power MOSFET.

@IMSAIGuy 3 жыл бұрын

You may be right, the datasheet says 375pf. I will have to repeat the experiment some day using a relay instead of a FET

@IMSAIGuy 3 жыл бұрын

I did. the resonance went from 440khz to 1.4MHz. So yes FET has the most effect. Thanks!

@Nar235 Жыл бұрын

Calculating the self capacitance when the ratio is 5 will give 1/4 of the added capacity not 1/5.

@chrisharper2658 3 жыл бұрын

I get 346pF for 330uH at 471KHz

@IMSAIGuy 3 жыл бұрын

that matches the FET capacitance perfectly. I just did a second video removing the FET from the setup and will post that in a few weeks.

@chrisharper2658 3 жыл бұрын

@@IMSAIGuy That would be series capacitance instead of parallel. That would be a low Z at resonance instead of high. Would it ring with a low Z?

@SpinStar1956 3 жыл бұрын

Great video but you still did NOT answer the question of where the UFO's are coming from!

@IMSAIGuy 3 жыл бұрын

They are electronic counter measures being tested on unsuspecting pilots.

@SpinStar1956 3 жыл бұрын

@@IMSAIGuy Oh, I feel much better now; I thought it surely was something else. 🧐 I can sleep much better now 🛌 Hi-Hi Thanks @IMSAI Guy 👍 73…

@IMSAIGuy 3 жыл бұрын

Maybe I want you to think that 😎

@SpinStar1956 3 жыл бұрын

@@IMSAIGuy Crap! Back to square-one… 😕