#772 Basics: Switching Power Supplies (part 1 of 2)

Samsung phone modifies a power supply’s output A. If the supply only supports 5V 1 A, the phone can only slow charge, the phone sets the charger for fast charging. If the charger is faulty, after a few charges it will become reliable.

Edit: my comment is wrong.
~~Y capacitors are made to handle more current, which is why they are used in line to line configuration. X capacitors on the other hand are used in line to ground configuration.~~

They use a Y-capacitor instead of an X-capacitor between the primary and secondary windings for EMI reduction because if a Y-cap fails it fails as an open. X-caps fail as a short. So if you instead used an X-cap between the primary and secondary windings, a failure in the cap would short the high voltage side to the low voltage side (typically not a good thing).

maan such a great explanation, I finally got it :)
One thing that I still can´t understand is how the max effiency of SMPS is stated as 96%, whilst a full bridge rectifier only achieves 82%... so how can the SMPS, which consists of many more parts, be more efficient?

Merci

it's an perfect explanation, thank you....

Hi people, I am a newbie on this and had some interest in this topic. I watched the video and read about switching power supply. Wanted to dig further into power supply so i found two malfunctioning LG flat monitors from 2007 (with the back lights fused). Found the service manual with full schematics and elements of the power supply, so my curiosity grew even further. I always put nitrile gloves, use 20A cat III multimeter probes, 500C silicone on table and I wear glasses. I always measure without pluging to electricity but iin this case there was so much curiosity. Thing is I tried to measure AC voltage on the rectifier input pins and the rectifier exploded, multimeter is ok, but can someone explain me what happened, I am totally sure it was my fault not the hardware. Maybe because the multimeter is automatic and switched to dc mode without noticing? Maybe because the diagram is different and there is an X 0.47u condenser and an inductor (choke filter) before the rectifier? I read the AC on the input pins of the board and the DC in the + - output of the rectifier/condenser and everyting was fine. Another thing I don't understand is that after burning the rectifier i removed it from the circuit, tested it with the multimeter in diode mode and all readings looked fine with 0.6 drop in all the diodes and reverse not conducting electricity, but then I put it again in the circuit and the readings on the DC output on the condenser dropped from 360 volts to 0.6 volts. And yes to be totally sure I am a complete idiot I repeated the process with the second power supply and burnt another rectifier xD. I will buy an extintor also and a couple of books and learned a big lesson. I will work with lower voltages in the future. The issue here is that i still do not get why this happened, I have the schematics of this power supply if someone can help me by having a look at it. It also seems a good continuation for this series of videos o_O, adding many more filters and multiple V outputs (+5, +12). Moved this comment here because I put it on the wrong video.

A couple things that perhaps were already addressed in previous comments:
You used same symbol for two different sets of ground. There's a ground on the high voltage side, and a different ground on the low voltage side, which the two sides should not be tied together.
Also for the high voltage side, you're missing your ground source reference.

Question:
I've seen some switching supplies, trying to fix one myself, that do not appear to have feedback from the PS output to the controller. Instead there seems to be a sense winding on the transformer. How do those work?
In the 12v PS I'm trying to fix, I get output for about 1 second every few seconds. Ideas?

thanks for fantastic job , just wondering if you could tell me about transformer wire size the primery and secondary or if possible to make a video about how to make step down /up transfarmer . many thanks

So nice thanks

Thanks, master great lesson. Thanks a lot for the fine explanation.

The basics are similar as long as you ignore the last 100 years of development and stick to the 1920 vintage buck, boost, and buck-boost. When you add the Ćuk, integrated magnetics, hybrid switching, PWM-Resonant, and Resonance Scaling Method concepts you get significantly cheaper, smaller, 99+% efficiency, and faster transient response.

Try a Bridgeless PFC converter followed by a Four-switch step-down storageless converter. Something from the 21st century. Or a VRM, 48V in 1.5V out at 200A.

Vintage! circa 1920. Try a 21st-century converter.

thanks

How do switching power supplies work when there's no feedback from the output side?

Best Explanation❤

He has no idea what he is talking about. As soon as he called the Snubber circuit a current limiter for the coil I laughed. It is simply a counter EMF snubber that limits the Reverse field EMF from back biasing the Rectifier diodes. Lots of made up information here. Dont waste your time

Nice1 Imsai & thank u

Your Capacitor in winding transformer is not real place.

Awesome explanation ❤

Thanks for the snubber circuit

Nice vid, and very clear and helpful commentary. It would have been useful to briefly mention "why use a SM PS?" The answer being that the size and weight - especially of the transformer - is much reduced, and that this is made possible by the AC frequency at the transformer being much higher than the 50/60 Hz of the mains. The downside (as you mentioned) is that this higher frequency gets emitted as interference to nearby electronics, even when quietened down by on board capacitors. Loved the use of a simple design to demonstrate the principle. The more complex SM PS are often difficult to fault-find and repair.

Thank you for excellent explanation

It's not 'Maysure' it's 'Measure', and by the way, you are completely Bonkers.

Great Video. Thank you.

Someone need to help this guy to film & edit the video, because heck did a great job & we don't want him to be distracted 😂

You did not mention the resistors

Tank you very much ,wanderfoll

Wow. This is so simplified and easy to understand. Thank you so much for posting this informative video.

How about the inductor at the output side

Just curious, with the blue capacitor jumping the coils, doesn't that end our circuit isolation? We now have a physical connection from one side to the other.

How does the ac voltage become 164 volts on the capacitor side? Is the capacitor processed with 1.4 and efficiency?

119x /-2? 168

i have just found your channel and judging from the videos I saw so far you sir are a good explainer. thank you mr

It's out of focus. For a shallow DOF.

If I had my bet, the idea came from the military, mainly the Air Force, using 400 Hz inverters, and noticing how the transformer's core was smaller due to the higher switching frequency. Frequency directly affects the core's size.

Dude has a serious case of ADHD…All over the place

Good evening idol new sending support from Philippines

very interesting way of explaining, you draw a diagram and then keep it covered with your hands the whole time!

Thank you ❤

I don't understand how switching a DC supply ON and OFF provides an AC supply. Surely all you have is a DC supply that turns ON and OFF?

Tel about earthing for smps

You can check it out here: [Click here]

I think you did an excellent tutorial of this version of a Switched Mode Power Supply ! Thanks for taking the time to help others to better understand how it works.

The world's best teacher thanks sir

Yeah but how does this fancy ic get powered ?, zener ?

Excellent tutorial on SMPS, thank you. The blue cap across the transformer is seen as a short circuit path to ground for VHF frequencies generated by the switching action of the DK1203. The DK1203 is an on/off switch with a fast switching speed, therefore it generates lots of VHF spikes / harmonics, which would lead to undesirable RFI; the cap gives a path to ground (snubbed) for those VHF components. Recall that Xc is the inverse of 2 π FC, so as frequency goes up, the impedance seen by those frequencies goes down...hence the VHF energy is shunted to ground while the lower frequency energy is kept in the transformer primary.