That's why you shouldn't throw away your old phone charger !

I modified an old phone charger and made it output 30 volts then, I added a voltmeter screen to use it as a tester for measuring any LED or zener diode less than 30 volts.

[Inventor_AW]

Warning: ⚠ ⚠ ⚠ have fun but always remember to be Safe, anything you try is at your own Risk, thank you

[anilpatel]

Very good information, earlier i show one circuit with multimeter after adding some circuit we able to measure led, zener diode, mcpc ect, and there voltage.

[derkarhu]

if you just turn the pot around, you would get increasing voltage with clockwise rotation....

[dgakadoug]

These small switchers are invariably flyback types. Significantly raising the output voltage of the supply MAY result in damage to the switch on the high-voltage side. If you are using an AC line voltage well below the allowed maximum you are probably safe. If your line voltage is already near the maximum allowed, you could destroy the switcher.

The secondary voltage is "reflected" back to the input side and "stacked" on the supply voltage according to the turns ratio of the so-called transformer when the switch turns off and the energy stored in the input winding is being transferred to the output winding. This is the only time that the inductor really acts as a transformer, and it is a design limitation for a flyback converter. Typically the inductor is designed so there is some safety margin between the sum of the peak DC on the input side and the reflected output voltage and the voltage rating of the switch. If you increase the output voltage it may result in exceeding the maximum allowable voltage across the switch which usually causes it to fail short-circuit.

Another potential problem is that many of these switchers use an extra winding on the inductor to power the switcher IC after it initially starts. If the output voltage is set too low the IC may get insufficient voltage to keep it running, resulting in in shutting down, trying to restart, running for a fraction of a second (typically) then shutting down again.

[buylon]

Why waste our time. Tell us at the start what this is supposed to do.

[aldemiralveslima]

Fantástico! Indispensável na bancada de qualquer profissional da área da eletrônica. Parabéns e obrigado por compartilhar. Um respeito abraço do Brasil 🤗 🇧🇷🙏

[DYIIdeas]

These small switchers are invariably flyback types. Significantly raising the output voltage of the supply MAY result in damage to the switch on the high-voltage side. If you are using an AC line voltage well below the allowed maximum you are probably safe. If your line voltage is already near the maximum allowed, you could destroy the switcher.

[sureyyaak]

Thank you very much for this very useful device. In my opinion because of the voltmeter power supply is maximum 30 Volts, you don't want to excess 29 Volts. If it is possible to increase the output voltage more than 30 Volts, you can add for example 7812 voltage adjusting device and take + 12 Volts for power supply of voltmeter. Thanks again. 👍

[nexus]

I just did this, was testing a smd LED, touched the uninsulated connections to the power supply inlet with my elbow…. Muscle spasmes and my arm shot out…. Punched the cat….. cat went out the window…. Landed on my old school teachers head….she fell over onto my car and broke my door mirror! Thanks! Now I have no door mirror and a vets bill for a cats PTSD fear of heights and a school teacher that now gives my kids bad reports at school parents evenings! All for saving a couple dollars on a ready made unit!

[andreystya]

It will work in low current range (ae no load), because voltage output element is transformer, that zener only for voltage stabilization via feedback circuit.

[utlykfl]

Que bueno !!! Te felicito un buen probador de diodos comunes, zener y led, lo voy hacer, gracias amigo . y Viva la libertad, carajo !!!
VLLC!!!

[WiekingderViking]

So nice to see a fellow who actually knows how to solder!

[reptilian_leader_]

Thank you for the useful information, you explained it clearly and made it easy to understand! 👌🏻

[Gagibit]

I have analog version made from little tranformer 30V 150mA with current limiter at few mA so i can check the Zener diodes values up to this is AWESOME idea as well...very compact!!! Will do some of this as well for sure!!!

[Djvbxns]

*Не стоит забывать о том, что не смотря на изменение выходного U, выходная P (мощность) = остаётся прежней* ☝

[ThePhoenixAscendant]

Bruh, I've got to say this has been one of the best demonstrations on how to desolder components from a PCB. I WILL be referencing this in the future when I move and have time to get into electronics again...

[Vilvaran]

Well at least it's not as deadly as some - but i'd still look at that transformer closer before using it.
Also most phone chargers will have a '431 reference of their own, so modifications are either easier or harder, depending on the circuit...

Finally, you should never push a transformer winding too far outside it's design voltage, as things get quite inefficient - possibly even dangerous! There is a reason why a relay clicks in the benchtop power supply; it selects three taps on the secondary winding - 0-7V, 7-15V and the final one goes to 30V... Simply looking at transformer action etc. should make it clear as to why it does this (hint: it's to do with 3Amp output current)
Here there is a 10K? resistor, to limit the current - so the power handling is actually not bad...

[foxmolder]

it is quite dangerous to OVERCLOCK the fly power supply at 6 V to 30 V with such a power, the reverse voltage on the output diode will grow (up to 250-300v) and it needs to be changed!
but what is much more dangerous is the gratifying voltage on the 1 winding and the corresponding impuls on the MOSFET DRAIN inside the PWM CHIP! if it exceeds the limit for them (and this is very likely), then there will be a big EXPLOSION and possibly a fire!
but the idea itself is of course interesting, just for the correct and safe release of it, you need to recalculate and rewind the transformer for your new voltage and replace the diode with a corresponding voltage 400-800v ulta fast diode!!!

[robinsattahip]

Interesting, but I would have picked a better charger to modify. That's one of those dangerous Chinese suicide chargers that doesn't even have a fuse or interference filter, and if CY1 is really a Y-rated capacitor and not just a 1KV cap I'd be surprised. I don't even like having those things around.

[agahgokdag]

Thanks to you, I can evaluate our old chargers, thank you very much...