#1465

Episode 1465
useful if you need +/- voltages in your circuits.
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[@p_mouse8676]

There are even symmetrical output variants of these things, which have another interesting use case, which is doubling the output voltage. So one can make a 48V (for like microphone phantom power) from a ±24V isolated DC-DC converter. On important thing to keep an eye on, is the switching frequency of these things. Some aren't constant frequency and some also go into hickup mode with low loads. Which really can ruin your day when you're not aware.

[@motherjoon]

Fun fact, you can run some buck converters just like you shown in the "wrong case" and they'll pump out negative voltages. You can also connect a capacitor at the switching node of a boost converter and use some diode magic to generate negative voltages and use an LDO to clean it up. Isolated DC/DC converters are relatively bulky and expensive.

[@MatsEngstrom]

Ah yes. I remember a video describing that. kzbin.info/www/bejne/qGWcc6qPZcp5hqM

[@p_mouse8676]

This isn't even a wrong way of using buck converters, but just a fine legit way of using them. The max input voltage will be extremely important at this point, since the input voltage now seen by the buck converter is the input voltage minus the negative output voltage. So with 12V input and -12V output this will be 24V. When using a so called coupled inductors (basically just a 1 to 1 transformer), you can make all kinds of symmetrical power supplies, or supplies with some kind of (low current) AUX output. Super useful!

[@kaber759]

1111¹¹1111¹¹¹3 is a ⅔and a 😂❤❤❤❤❤❤😂❤❤❤❤❤❤❤❤❤❤❤1e1r3¹²❤

[@Electronzap]

Didn't know about the B1212S-1W component. It's pretty cool. Nice and compact for what it does.

[@gorak9000]

I think the best way the terminals on the isolated side can be labeled is [#]V and [#]V return (or [#]V+ and [#]V-) - you see it labeled that way on some boards sometimes, and it makes it clear it's not ground, it's the "return current terminal related to the associated positive terminal". If you're hard wiring the + side of the isolated side to ground and using the reference terminal as a negative rail, then I'd label the terminals -[#]V and 0V (or -[#]V return) to not cause confusion!

[@jafinch78]

Interesting, I've never seen described and shown before like you've done in general. This is interesting as I've only more recently studied the half-bridge dc-dc converters when trying to better understand the theories that apply or might be able to be applied for designs using the Prius gen2 and gen3 inverter-converter assembly modules and parts.

[@georgesampson4714]

It is my opinion that we (electronics people) use the word "ground" too often resulting in misunderstanding by those who are just learning electronics, especially those in a non-formal setting. I think "common" provides a better description of what we really mean most of the time. In the olden days when I was just a neophyte I had an ancient HP oscilloscope of 2Mhz bandwidth which had 3 banana jacks on the front; "+", "-" and "GND" with a little shorting bar with which you could flip in to short "-" to "GND". I didn't quite understand the point of the shorting bar until one day with the two terminals shorted together and the scope connected to my circuit I plugged the two prong power cord in the wrong way and my lab was instantly filled with magic smoke and dripping burning insulation. It wouldn't have been so bad except my wife was standing next to me so I could show off my marvelous invention. She was impressed, but not by my skills. After much analysis of what went wrong I finally understood what that little shorting bar was for and the difference between common and earth ground.

[@bayareapianist]

You were lucky you saw there was a bar connected to the ground. . Most scopes do not tell their power ground are connected to input ground.

[@TonyBarr99]

Nearly the exact thing happened to me. The differences were 1.) my daughter, not my wife and 2.) It was with a Tek scope. I had just probed the mains the day before to see my mains sine wave. Unfortunately, when I showed it off to my daughter the next day, I had the probe reversed. Boom!

[@antoinchamamyan5680]

Oh, You’re so lucky guys to get some people watching you while in your workshop, my wife keeps yelling on me to get me out to live as a family a 5 minutes I stepped in 😂😂😂

[@gkdresden]

You can also use a non-isolated 24 V converter to make a +12 V / 0 / -12 V power supply. The former +12 V line is the new ground line, the former ground line is new -12 V line and the 24 V output is the new +12 V line

[@andrewandrosow4797]

Interesting video! I made some experiments - and I think that PWM in flyback converter is not a good idea. Suppose - we have 100kHz PWM (5 microSec on , and 5 microsec off). When load becomes very small - the feedback loop decreases pulse width to very small values - less that 1microsecond. So we can not on/of a mosfet with such a small time effectively. A burst mode (packets of pulses) much increases noise and pulsation on output. Therefore - there can be some pulse-frequency modulation.

[@PATRIK67KALLBACK]

I'm into power supply with a clean voltage. I have been using isolated dc/dc converter, however, it's a hell to filter the high frequency ripple that is arround 50 - 100 mV RMS. When I use the old school transformer together with ldo the ripple is 2 - 4 mV RMS.

[@charliemopps4926]

ah... so these are noisy? that's a problem as... the primary reason to need the negative voltage are audio circuits.

[@plateoshrimp9685]

You can also get a DC DC converter with + and - 12 outputs that runs off pretty much whatever input you want.

[@rogergreenwood1536]

Such a good take away:- don't look for what they do say, look for what is missing, in this case the word "isolated". Your channel always educates, informs and entertains, thank you. p.s we need to see Imsai cat next..... ;-)

[@IMSAIGuy]

ImsaiDog ate the cat

[@darrellsharrock3859]

Why I love electronics. There are lots of ways to do stuff. Analogue uses fewer components though. Try a 78L12 . Those low power devices can be added for powering Opamps and they are the size of a small signal transistor. Really cheap too. Come in surface mount too , if you have better eyesight than I do. Sucks getting older 😂

[@wiwingmargahayu6831]

optocoupler and agilent meter is amazing Sir beside your math skill Sir

[@antoinchamamyan5680]

Funny how your multimeter was showing the ambient temperature 14.7 degrees C, keep yourself warm mate.

[@bayareapianist]

Let's say you want to have +/-12V. Can you use a 7812 and an 7824 and they their input to a sufficient (28v) non-regulated dc PS. Then you will have 24v and 12v wrt ground. Then use +12v as a new ground. The old ground is now -12v and +7824 output would be +12v. Anything wrong here? The idea is the same as voltage divider explained here but has much more stable current.

[@TheEmbeddedHobbyist]

you can't beat a good old transformer for isolation, either a big lump of iron in a linear or a small lump of ferrite in a DC-DC isolated converter. but still they produce transformers where the isolation is only provided by the enamel on the wire.

[@RoyArmy-WREW918]

so, your just talking about what I remember being referred to as a "Floating Ground" in other words moving the Zero Reference away from a hard ground. Right???

[@__--JY-Moe--__]

hark! I think I hear story time on the radio! A fiery horse with the speed of light, a cloud of dust and a hearty Hi-Yo Silver! The Lone Ranger! ... With his faithful dog sparky, the daring and resourceful masked rider loves performing tricks in the park! Hi-Yo Silver away! sorry! so after U teach, it's story time!

[@alnoorratansi9364]

Great video, How would you increase the output current, let say to 1 amp ?

[@IMSAIGuy]

at 12V, you would need to buy a 12W version

[@Ouefdie]

This can be used to power a Eurorack Synthesizer right? Well with a higher wattage version i suppose.

[@chrisharper2658]

On your Isolated DC to DC schematic, where does the op-amp get its power? I've been amazed that those power supplies can maintain such good regulation when using an opto-coupler and yet they do. Part of the magic is that the PWM has to kick start the circuit into operation.

[@maeanderdev]

Usually shunt regulators, such as the tl431 are used. I guess it's datasheet answers your questions. The 'Opamp' as well as the reference voltage were inside that 3 Pin device and it gets wired in series with the optocoupler. That way it is supplied with it's output pin

[@hachikiina]

can't you use a zener diode for reference voltage?

[@maeanderdev]

@@hachikiina not shure if I underrstand you correctly The shunt regulator is at the secondary circuit of the cvonverter and compares the output voltage to an internal reference voltage. It passes current from it's cathode to it's anode pin through an optocoupler if the measured voltage exceeds the reference voltage, thus providing feedback to the primary circuit. A zener in series with an optocoupler would work as a simple feedback network. However the temperature coefficient of a zener depends on the zener voltage. If it is chosen to cancel out the tempco of the optocoupler, only one output voltage (or a higher one by using a divider) is possible and probably exceeds many common converter output voltages. contrary to that shunt regulators are temperture compensated and have a specified accuracy. The input is high inpedance (opamp like), furtther easing the design and also easing loop compensation network design

[@huanglin210]

It is so cool,but it is too difficult for me. Because I'm a new hand,would you please make more basical video? thank you very much!

[@jimomertz]

Did Madge stop using Palmolive?

[@IanNature7]

🦦I like your videos you‘re best electronic teacher ever ☺️ 🙏 if i had a wish 🫣 then a teacher who teach me the inner life of op amps 🤔🙏thx for all

[@IMSAIGuy]

opamp: kzbin.info/www/bejne/kGmtdaasm7-dgpo

[@IanNature7]

🦦 Yeah, but there are so many out there, whats the differents or are they the same in some way 🤔 and, why is there no op amp for high voltage and current like an op amp with many 2N3055 🤔 can you explain that 🙏☺️thx

[@IMSAIGuy]

there are many types, I did some videos on a OPA549A

[@IanNature7]

🦦 Someday I will have seen all your videos 😉🙏

[@sajalsnanda6209]

Can u please share the link for the circuits

[@IMSAIGuy]

sorry, too long ago

[@sajalsnanda6209]

@@IMSAIGuy im doing a project on boost converter with voltage mode feedback i don't want to use 555 neither microcontroller I have to use op amps but I'm having problems in simulation of my circuits I saw your video in this video you introduced isolated dc converter using octocoupler I liked it very much.Thank you for such easy to understandable videos.

[@JurassicJenkins]

I just reverse the capacitors in the 2 circuit. 😮

[@johnwest7993]

I see I can recognize your channel by a glance at the back of your hand above a schematic. The isolated DC to DC converters are getting tiny. I like it. It's a shame they don't make manual focus cameras anymore. ALL of the KZbin channels have trouble with optical focus.

[@stheil]

Eh most "professional" cameras (DSLR/mirrorless) have the option to manually focus. I think most people just don't bother because autofocus works just fine *most* of the time and it would be a hassle to always manually focus just because every now and then autofocus might decide to focus on the wrong thing... Totally agree on the size of isolated DC/DC converters nowadays, they are absolutely tiny and the efficiency and ripple are also miles above what they used to be.

[@IMSAIGuy]

Yes, of course I could manually focus everything but it is just too much work. Once in while I do manual focus for close shots and my macro lens is an old manual lens. There is a lot of things I could do to make polished videos but at that point I would loose interest and quit. For me it is about having fun in the garage and sharing it.

[@hgbugalou]

@@stheil Bigclive still uses manual focus. It works for him because his framing rarely changes.

[@Stevie_D]

I was looking for a quick and dirty low-current voltage doubler when I stumbled into this video - as I was watching it hit me like a jot from an AC Mains circuit ... but someone below (P_Mouse) beat me to the comment! They say "Great minds think alike" ... or is it that fools seldom differ - either way, I will have fun playing with it!

[@agnelomascarenhas8990]

Charge pump such as 7660, I think can do that. Take in +V and output -V. Meant for very low loads. Very efficient.

[@IMSAIGuy]

kzbin.info/www/bejne/n6nNZ4iChZtkmrs

[@gd2329j]

Are you over thinking it ! Just have a 6v battery pack & a dc - dc converter outputting 12v . Battery pos is 0 v Battery neg is -6 The dc - dc converter output is +6 Converter are noisy little monsters ! RF splatter boxes ….................. 😢

[@mikegaskill6347]

Watch your camera focus, so we can see what your doing. Please.