Hi everyone:
I apologize if this has been asked before. I did do a bunch of research... but there is a difference (as far as I can tell) between my problem and what my research came up with.
I am trying to build a straight 120VAC RMS to 160 / 170V DC bridge rectifier that can provide 5 - 10 amps. The schematic is as shown on wikipedia under the basic operation section:
http://en.wikipedia.org/wiki/Diode_bridge
I know it is dangerous to work directly with AC mains. Many people have posted this in this forum. However, in this application, I cannot use a transformer for isolation and whatnot because of a weight constraint on the circuit. A transformer would add unneeded weight (around 3 pounds from my research). This circuit is 'mobile' and is to be put in a high mileage vehicle. It is also only to be plugged in at certain times, not all the time. ANYWAYS... onto the problem
For the two source terminals, I connect my AC wall power. One side of the rectifier goes to the hot wire (black), and the other side of the rectifier goes to the neutral wire (white). Now when I turn the power on (plug it in)... BANG.. top right diode always explodes. Ive tried the circuit 3 times replacing the diodes each time. Every time its the same exact diode that blows. The first time the circuit blew is because I connected a scope ground terminal of a probe to the 'ground' of the bridge. That was stupid... after research I see why. The second time.. I didn't connect anything and just had the neutral and hot connected with open circuit DC terminals. The third time I just put a couple of 2 megaohm resistors inside the bridge to make sure that no current could possibly go from one side of the hot to the other side directly.
This baffles me as literally, the DC outputs of the bridge are open (open circuit). For the rectifier diodes I am using 4 1n4004 general purpose diodes. In the datasheet it says that these are rated for a repetitive peak reverse voltage of 400 volts. I don't exactly know what the problem is.. because I am literally just hooking up a neutral and the hot wire to the bridge. The DC output is not grounded or connected to the third wire in a wall house plug (earth ground) or the green wire.
Another question. I need to add just a small amount of safety to the inherently unsafe circuit. Would a 5 - 10 amp circuit breaker at the input of the hot or neutral be alright? I don't exactly want to use a fuse as it is not resettable, but I will if suggested to. But seeing how things turned out today, I would have blown 3 fuses, which we do not have many of.
Any help is appreciated. I reiterate, I can't use a transformer for this application. Ultimately this is to be the base of a 0 - 120V selectable SMPS power supply.
Thanks
I apologize if this has been asked before. I did do a bunch of research... but there is a difference (as far as I can tell) between my problem and what my research came up with.
I am trying to build a straight 120VAC RMS to 160 / 170V DC bridge rectifier that can provide 5 - 10 amps. The schematic is as shown on wikipedia under the basic operation section:
http://en.wikipedia.org/wiki/Diode_bridge
I know it is dangerous to work directly with AC mains. Many people have posted this in this forum. However, in this application, I cannot use a transformer for isolation and whatnot because of a weight constraint on the circuit. A transformer would add unneeded weight (around 3 pounds from my research). This circuit is 'mobile' and is to be put in a high mileage vehicle. It is also only to be plugged in at certain times, not all the time. ANYWAYS... onto the problem
For the two source terminals, I connect my AC wall power. One side of the rectifier goes to the hot wire (black), and the other side of the rectifier goes to the neutral wire (white). Now when I turn the power on (plug it in)... BANG.. top right diode always explodes. Ive tried the circuit 3 times replacing the diodes each time. Every time its the same exact diode that blows. The first time the circuit blew is because I connected a scope ground terminal of a probe to the 'ground' of the bridge. That was stupid... after research I see why. The second time.. I didn't connect anything and just had the neutral and hot connected with open circuit DC terminals. The third time I just put a couple of 2 megaohm resistors inside the bridge to make sure that no current could possibly go from one side of the hot to the other side directly.
This baffles me as literally, the DC outputs of the bridge are open (open circuit). For the rectifier diodes I am using 4 1n4004 general purpose diodes. In the datasheet it says that these are rated for a repetitive peak reverse voltage of 400 volts. I don't exactly know what the problem is.. because I am literally just hooking up a neutral and the hot wire to the bridge. The DC output is not grounded or connected to the third wire in a wall house plug (earth ground) or the green wire.
Another question. I need to add just a small amount of safety to the inherently unsafe circuit. Would a 5 - 10 amp circuit breaker at the input of the hot or neutral be alright? I don't exactly want to use a fuse as it is not resettable, but I will if suggested to. But seeing how things turned out today, I would have blown 3 fuses, which we do not have many of.
Any help is appreciated. I reiterate, I can't use a transformer for this application. Ultimately this is to be the base of a 0 - 120V selectable SMPS power supply.
Thanks
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