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Old 01-17-2022, 05:39 PM   #21
bohaboha
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Default Re: can a flyback transformer for USB charger isolate?

eccerr0r the tube led lamps should be out of function but the circuit itself is perfectly ok as myself i picked old led lamps from the environmental room that we have here where people throw what they do not need. sharing is for the idea that you asked to see
then if you did not like ...
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Old 01-17-2022, 08:39 PM   #22
eccerr0r
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Default Re: can a flyback transformer for USB charger isolate?

Sorry, probably missed my rant about youtube videos... mainly because people still use machines that can't view them and it takes forever to figure out if it contains useful information 3/4 the way through or not...
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Old 01-19-2022, 01:34 AM   #23
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Default Re: can a flyback transformer for USB charger isolate?

Quote:
Originally Posted by eccerr0r View Post
I'd like to see this switch mode transformer idea, it's possible but tricky to pull off...
If it is what I think it is... I've done it, it's supper easy, and works 100%... but I've only had good success with ATX PSUs.

Basically, take any old crappy ATX PSU (but preferably one that won't explode on you if you mistreat it ). Then find another crappy (preferably non-working) ATX PSU and extract the big/main transformer from it. Open the working ATX PSU and solder wires directly on the transformer's secondary side output pins (i.e. ground, 5V, and 12V... or 2x wires for 5V and 2x for 12V in case of half-bridge PSUs with a center-tap.) Place PSU back into its case, but bring out those wires outside for easy access/hook up (might help to label them first too, so you know what's what.) These wire outputs will now have low-voltage, high-frequency AC that you can use to drive just about any other SMPS transformer. Depending on how you connect these to the 2nd big/main transformer extracted from the non-working PSU, you should get back something like about 170V (or slightly more) high-frequency AC back on the primary-side pins.

I suppose the same idea could/may (should?... to an extent) work with USB chargers too... but not sure how well. Main reason I think this might not be ideal is because most small USB chargers and other power adapters have "flyback" transformers that operate in discontinuous mode (i.e. secondary side output "pulse" occurs only after the primary side current is cut off, collapsing the magnetic field in the core of the transformer and releasing its energy on the secondary.) So if you hook up another flyback traffo "back-to-back" on the output of the USB/adapter, there's actually no telling if the output voltage on the "primary" of the 2nd transformer will be the same as that on the first... or consistent in any way. In fact, flyaback transformers aren't really "transformers" in the true sense. They are coupled inductors with a "gapped" core.

So indeed that may be a little tricky with the USB chargers, as eccerr0r suggested... but certainly give it a try.

On the other hand, with ATX PSUs, the main transformer operates in continuous mode, just like a regular line-frequency transformer does. So input and output voltages will be consistent based on turn ratios. Just have to watch out, though - the output of the 2nd (back-to-back) transformer is not protected in any way from over-power, over-current, or short-circuit... so you can fry your circuits easily if not careful. I suggest adding a 12V halogen bulb between the two low-voltage sides of the two transformers to limit power.

Quote:
Originally Posted by eccerr0r View Post
Sorry, probably missed my rant about youtube videos... mainly because people still use machines that can't view them and it takes forever to figure out if it contains useful information 3/4 the way through or not...
Your rant is completely valid.
If i had a penny for every self-proclaimed "tech's" video on YouTube, I'd be a millionaire myself. Seems like they are dime a dozen, and more popping up every day. A lot of them are just a waste of time, though... or too long to watch through... or too specific, as if the issue they found is the only issue you will ever find in such device.
That's not to say there aren't any good tech/educational videos on YT. But the ratio of good/worthwhile ones to crap/garbage ones is very small.
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Old 01-19-2022, 08:14 AM   #24
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Default Re: can a flyback transformer for USB charger isolate?

Quote:
Originally Posted by momaka View Post
If it is what I think it is... I've done it, it's supper easy, and works 100%... but I've only had good success with ATX PSUs.

Basically, take any old crappy ATX PSU (but preferably one that won't explode on you if you mistreat it ). Then find another crappy (preferably non-working) ATX PSU and extract the big/main transformer from it. Open the working ATX PSU and solder wires directly on the transformer's secondary side output pins (i.e. ground, 5V, and 12V... or 2x wires for 5V and 2x for 12V in case of half-bridge PSUs with a center-tap.) Place PSU back into its case, but bring out those wires outside for easy access/hook up (might help to label them first too, so you know what's what.) These wire outputs will now have low-voltage, high-frequency AC that you can use to drive just about any other SMPS transformer. Depending on how you connect these to the 2nd big/main transformer extracted from the non-working PSU, you should get back something like about 170V (or slightly more) high-frequency AC back on the primary-side pins.

On the other hand, with ATX PSUs, the main transformer operates in continuous mode, just like a regular line-frequency transformer does. So input and output voltages will be consistent based on turn ratios. Just have to watch out, though - the output of the 2nd (back-to-back) transformer is not protected in any way from over-power, over-current, or short-circuit... so you can fry your circuits easily if not careful. I suggest adding a 12V halogen bulb between the two low-voltage sides of the two transformers to limit power.
Could you please post a picture of this circuit or a wiring diagram of how you would hook this up thanks
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Old 02-06-2022, 05:10 PM   #25
bohaboha
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Default Re: can a flyback transformer for USB charger isolate?

Quote:
Originally Posted by momaka View Post
If it is what I think it is... I've done it, it's supper easy, and works 100%... but I've only had good success with ATX PSUs.

Basically, take any old crappy ATX PSU (but preferably one that won't explode on you if you mistreat it ). Then find another crappy (preferably non-working) ATX PSU and extract the big/main transformer from it. Open the working ATX PSU and solder wires directly on the transformer's secondary side output pins (i.e. ground, 5V, and 12V... or 2x wires for 5V and 2x for 12V in case of half-bridge PSUs with a center-tap.) Place PSU back into its case, but bring out those wires outside for easy access/hook up (might help to label them first too, so you know what's what.) These wire outputs will now have low-voltage, high-frequency AC that you can use to drive just about any other SMPS transformer. Depending on how you connect these to the 2nd big/main transformer extracted from the non-working PSU, you should get back something like about 170V (or slightly more) high-frequency AC back on the primary-side pins.

I suppose the same idea could/may (should?... to an extent) work with USB chargers too... but not sure how well. Main reason I think this might not be ideal is because most small USB chargers and other power adapters have "flyback" transformers that operate in discontinuous mode (i.e. secondary side output "pulse" occurs only after the primary side current is cut off, collapsing the magnetic field in the core of the transformer and releasing its energy on the secondary.) So if you hook up another flyback traffo "back-to-back" on the output of the USB/adapter, there's actually no telling if the output voltage on the "primary" of the 2nd transformer will be the same as that on the first... or consistent in any way. In fact, flyaback transformers aren't really "transformers" in the true sense. They are coupled inductors with a "gapped" core.

So indeed that may be a little tricky with the USB chargers, as eccerr0r suggested... but certainly give it a try.

On the other hand, with ATX PSUs, the main transformer operates in continuous mode, just like a regular line-frequency transformer does. So input and output voltages will be consistent based on turn ratios. Just have to watch out, though - the output of the 2nd (back-to-back) transformer is not protected in any way from over-power, over-current, or short-circuit... so you can fry your circuits easily if not careful. I suggest adding a 12V halogen bulb between the two low-voltage sides of the two transformers to limit power.


Your rant is completely valid.
If i had a penny for every self-proclaimed "tech's" video on YouTube, I'd be a millionaire myself. Seems like they are dime a dozen, and more popping up every day. A lot of them are just a waste of time, though... or too long to watch through... or too specific, as if the issue they found is the only issue you will ever find in such device.
That's not to say there aren't any good tech/educational videos on YT. But the ratio of good/worthwhile ones to crap/garbage ones is very small.
thank you momaka for your suggestion i was going to ask the same thing as sam_sam_sam if you could? and please can you say what you thought it was?

Last edited by bohaboha; 02-06-2022 at 05:17 PM.. Reason: incomplete question
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