Using diodes to reduce voltage by 1-2 V under a very high load (e.g., 20A)

[TheElectricChicken]

Well it was true in the case of a large 7 megawatt variable speed drive at my refinery.

Wait, I need to go outside and check the 7 megawatt variable speed drive on my cordless drill. I'll be back in 5 minutes.

[wraper]

Power semiconductors usually become short, not open. And all your circuit becomes busted.

according to the encyclopedia of you ? no seriously, where do you get your guesses from ?

LOL, I have my guesses from expedience. Your guesses seem to be out of thin air. BTW this is not guess but how the things do happen in the real world.

[madires]

Power semiconductors usually become short, not open. And all your circuit becomes busted.

according to the encyclopedia of you ? no seriously, where do you get your guesses from ?

That's common EE knowledge! You will see that quite often when you repair broken stuff. For example, I've fixed a broken remote controlled mains adapter recently. The fault was caused by a shorted Zener in the power supply circuitry.

[TheElectricChicken]

Ok, my 7 megawatt variable speed drive on my drill is fine. Actually maybe I should have taken my glasses because I don't think that a 7 megawatt variable speed drive is the sort of equipment that beginners will come across. Certainly has nothing to do will "ALL SEMICONDUCTORS FAIL SHORT" . Maybe I'm missing the connection without my glasses because it looks like you're just making up guesses with statements like that.

I can make up better crap, like "open circuit" gets 5 million hits on google whereas "short circuit" gets 20 million hits therefor 75% of faults are short circuit. See? how will you ever start a company that sells battery life extenders if you can't sound more convincing with your wild guesses.

[TheElectricChicken]

That's common EE knowledge! You will see that quite often when you repair broken stuff. For example, I've fixed a broken remote controlled mains adapter recently. The fault was caused by a shorted Zener in the power supply circuitry.

Well there WAS that 150 Megawatt drive on that old ladies wheelchair that shorted out, boy was she pissed by the time the batteries ran out. Luckily she still hasn't made it back to my workshop to claim on the warranty I gave her, I hear she's in Uzbekistan last time NASA picked her up on radar.

Sorry, but that is STILL "encyclopedia of YOU" with nothing at all to back it up.

[wraper]

Sorry, but that is STILL "encyclopedia of YOU" with nothing at all to back it up.

Sorry, I have no intention to back up anything for people not seeing further than their arse.

[TheElectricChicken]

http://images.sodahead.com/polls/004375463/2955483819_not20surprised20_3e3394ec866826de6153b04b99d9a297_xlarge.jpeg

[wraper]

http://images.sodahead.com/polls/004375463/2955483819_not20surprised20_3e3394ec866826de6153b04b99d9a297_xlarge.jpeg

Congratulations! You won in this contest. Continue to live happy in your imaginary world.

[TheElectricChicken]

there was no contest, you were simply making up the idea that most semiconductors fail shorted, and presenting it as though it was fact. It is not fact. This is the beginners section so presenting bull&** as though it was fact and being serious about it, is misleading the beginners. I just don't find it cool.

And no, people were never able to send me to the store to get a box of amps or a left handed spanner. I just think it's inappropriate to give poor information dressed up as something it is not. I always say "I would guess" or "my intuition tells me..." or something like that, or better, give a link to fact.

[c4757p]

Chrissake, dude, do you know anything? Yes, semiconductors almost always fail short. Why? Well, why wouldn't they? Think about the way they are made. Almost the whole thing is conductive, except for that extremely thin depletion region in the middle...

[SharpEars]

Well it was true in the case of a large 7 megawatt variable speed drive at my refinery.

Wait, I need to go outside and check the 7 megawatt variable speed drive on my cordless drill. I'll be back in 5 minutes.

Chicken, I may not agree with your arguments, but I do love your humor.

[TheElectricChicken]

Chicken, I may not agree with your arguments, but I do love your humor.

Thank you SharpEars. I do very well when I have good quality questions being fed into my brain, however, when poor quality is fed in... well the output is ... DODGEY!!

I always like to be the sort of person who, if I had to argue, you'd shout food and drink just so that you could have a good argument with me all afternoon.

[TheElectricChicken]

Chrissake, dude, do you know anything? Yes, semiconductors almost always fail short. Why? Well, why wouldn't they? Think about the way they are made. Almost the whole thing is conductive, except for that extremely thin depletion region in the middle...

Oh I'm sure you know more than anyone, myself included. I'm a chicken who learned to type after all.

There are only two choices when you send 20 AMPS continuous through a 1A diode. It will either melt, blow off the plastic coating and splutter all over the place and go OPEN CIRCUIT,

OR

You've invented a new way to distribute power across the country in a way that engineers have been perusing for decades, they can dump their ridiculous and expensive pursuit of room temperature super-conductors and go with a long string of diodes instead. Because if they fail, they fail as a short circuit and therefore, you can continue sending the fault current through them forever. 20x 50x 100x doesn't matter because they always fail shorted, according to the encyclopedia of you. which I don't believe btw. I use it to prop up a lop sided table.

[wraper]

You were simply making up the idea that most semiconductors fail shorted, and presenting it as though it was fact. It is not fact. This is the beginners section so presenting bull&** as though it was fact and being serious about it.

This is the fact, if you were a tiny bit smart, you'd asked where you could find a more information about it. Yet you disagree with every good practices an widely known information people suggesting to you, claiming they got it in their own "encyclopedia". You even managed to completely upend the idea in those thermal images  .

[wraper]

...according to the encyclopedia of you. which I don't believe btw. I use it to prop up a lop sided table.

Believing if for religious nuts. Smart people prefer knowledge.

[c4757p]

There are only two choices when you send 20 AMPS continuous through a 1A diode. It will either melt, blow off the plastic coating and splutter all over the place and go OPEN CIRCUIT,

OR

No, typically it will fail short. Yes, if you're pumping an insane 20x overload through it, it will then continue to fail in new and interesting ways, usually ending in an open circuit, but most semiconductor failures are not due to 20x overload! Try a 1.5x overload for an extended period of time.

[madires]

Yesterday a friend brought a broken TV, obviously bad power supply (standby LED not lit, doesn't turn on). A voltage check confirmed that the the main voltage is missing. The secondary of the SMPSU has three diodes (SB5B0: 5A, 100V, Schottky) in parallel for the main voltage. Actually there are four on the PCB, one unpolulated. One failed short and the fault also released the magic smoke of the SMPSU controller (integrated MOSFET) and two resistors (current path to ground for the SMPSU controller's MOSFET). A quick search showed that Vestel, the manufactuer of the SMPSU, is known for that problem. Of course there's also a video: