#773

Episode 773
Measurements of the power supply showing PWM and load regulation
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[@richardcranium5839]

wouldda been nice to see where you probed and what your scope settings were

[@SVSunnyJim]

I finally got it. Following your instructions and by copying your diagrams, along with making a bullet pointed list of the flow of current from start to finish I at last managed to understand.. ..and slowly I turn my attention to all the electrical things I've broken.... 👍

[@CASHSEC]

Would have like to see what happens when design load is exceeded but without creating smoke.

[@technical5880]

watched part 1 and 2, simple and understandable, thanks, may allah bless you.

[@paulstaf]

That is how I hold my tools to my workbench too!

[@jdmccorful]

Demonstration of operation is tops!Enjoyed watching.

[@hicmikrolab]

Great video with simplicity. I love this

[@electronicengineer]

Excellent video demonstrating the PWM function of the DK1203 switch mode controller IC as it receives its feedback from the TL431 shunt voltage reference IC. Thanks for showing us the actual waveform on the oscilloscope Mr. IMSAI Guy! Always an interesting video on your KZbin channel. You are very much appreciated. I found the ringing, after the on pulse rather interesting to see... Fred

[@paulcohen1555]

Very nice. The IC is Okay and comes almost for free. The problem with these cheap power supplies is the quality of the components, usually the capacitors.

[@zarzarel1910]

Big LIKE and Subscribed...Better than college...clear and logical explanations...thanks a lot for your lessons, best regards, Dan

[@zarzarel1910]

To Curiostory user: I didn't understand your message, which you didn't even leave visible to others... do you have something against my comment or are you selling cheap philosophy? From Mr. IMSAY Guy, I always have competent and necessary advice for me, for my field of work and I thank him (professor IMSAY Guy) once again for his kindness and explanations.. I'm posting the message I received from you, for this video: "You're comparing apples and oranges. It's not better than college, and nor is it trying to be better. College gives a road map into the unknown, and these kind of videos just give you the accompany..." doesn't help anyone with anything, technically speaking, about the subject of this video

[@Travis141123]

Maybe a quick video on failure points and what to look out for?

[@lupojacobo9892]

Thanks for sharing your knowledge

[@IMSAIGuy]

My pleasure

[@gmendes1831]

Thanks!

[@space_cowboy007]

Hello and thanks for the content. What does happen to the pwm waveform when you try to draw a bigger current than the maximum rated?

[@jugnu361]

smart thing u did by NOT connecting ur Scope Ground lead on -ve of The Input Bridge rectifier..............it saved u from smoking ur scope........

[@Richard-ul2sh]

Great video, but not sure where you are connecting the scope? Therefore is it dc or ac you are reading.

[@72chargerse72]

I would even like to see how you connected your scope.

[@dbmaster46446]

we need a part 3 with the big psu and what happen when you over current the psu?

[@johndavis1465]

the waveform shown is unstable due to rining also not show or say anything about isolation transformer

[@RiaziMohandesi]

Were are the probes placed?

[@EJEuth]

This #773 and the previous #772 were very good to know. Did you see how it works if in OVERLOAD (overcurrent) mode? When does it happen? Does it enter intermittent ‘hiccup ‘ mode or simply looses regulation like those cheap 12V adapters?

[@Sidicas]

Without an overcurrent protection shutoff circuit it will just burn itself up. I know because I've seen so many junk PC switching power supplies fail in exactly that way on overcurrent condition where they just blow up. Check out the Games Nexus video "Speedrun Gigabyte Power Supply Explosion: Biggest Failure Yet "

[@jbrown468]

Mr @IMSAI Guy, thanks for another great video. I have a question. How does a switching supply reduce the transformer size requirement -- or does that only apply in certain applications?

[@IMSAIGuy]

higher frequency, less inductance needed

[@argcargv]

Is this measured across the switch or across the primary? It looks like it is across the switch which goes low when the switch is on, the high flat part is where the diode in the output is conducting, charging the output capacitor, and the ringing part is when the output winding voltage has dropped below the power supply capacitor voltage so it is disconnected and the transformer is resonating with the circuit parasitic capacitance. Is that what we are seeing on the scope?

[@paulcohen1555]

I think that's the exact explanation of the waveform.

[@ryanjoyce88]

do you have a video on the "dummy load" device you built? that seems like it would be a really useful item to have on a bench. is it just a giant pot with an ammeter and voltmeter built in? would be curious to learn more.

[@IMSAIGuy]

buy: kzbin.info/www/bejne/o4SpoIqvgZeSoZY make: kzbin.info/www/bejne/hZ3UqqB5iL9ne80

[@ryanjoyce88]

what is the bouncing/ringing sine wave after the square wave of each pulse? looks like there's a very high frequency ringing followed by a low frequency ringing. for instance at 6:21 you can see it very clearly, the sine wave looking signals that's slowly reducing in amplitude (dead center on your oscilloscope screen at that timestamp)

[@IMSAIGuy]

kzbin.info/www/bejne/fmHbfGqMrNiZr5I

[@jamaljoscho3411]

nice thank you very much...Where in the circuit board did you put the terminal for the oscilloscope

[@IMSAIGuy]

at the anode of the diode I think

[@fredflintstone1]

Nice follow on video:-)

[@fredflintstone1]

could you add caps to reduce the ripple??

[@IMSAIGuy]

I did not measure the ripple, but if it has some then yes, adding caps helps

[@flippo1971]

I looked at the Scope but did not see the switching frequency of the DK1203. Did anybody else catch it? Great video, very interesting and informative, Thank you!!

[@IMSAIGuy]

check out the datasheet. it is 65khz

[@IMSAIGuy]

grupoautcomp.com.br/wp-content/uploads/2016/11/Specification-IC-DK1203.pdf

[@jvk-pj8jr]

Time base is 5 us/div, period T from scope about 3 divisions, f = 1/T so f = 67 kHz

[@JTKhopefuls]

how do i make one of these load kits?

[@IMSAIGuy]

buy: kzbin.info/www/bejne/o4SpoIqvgZeSoZY make: kzbin.info/www/bejne/hZ3UqqB5iL9ne80

[@nayanjagirdar8408]

👍

[@patwhens]

BW limit the scope for this type of SMPS measurement.

[@argcargv]

He is not measuring the output of the supply, he is measuring a point on the switching side of the supply to show how the switching supply functions. There is no need to BW limit for these purposes.