[SOLVED] 2 Amp 16 Volt Power supply problem

[cutedrummerboy]

i have a 16v 2 amp transformer, i make a bridge with 1N4007 and after the bridge two 2200uf/25volt and a .1uf disc type capacitor is paralleled. now when i switched on, two of my diodes is burned... can anyone help me to rectify this problem. i am a newbie to electronics. thanks in advance. here is my schematic:

 

[IanP]

i have a 16v 2 amp transformer, i make a bridge with 1N4007 and after the bridge two 2200uf/25volt and a .1uf disc type capacitor is paralleled. now when i switched on, two of my diodes is burned... can anyone help me to rectify this problem. i am a newbie to electronics. thanks in advance. here is my schematic:

First, you must have a 1.5A-2A slow-blow fuse between the input and the bridge, and second, when you connect diodes make sure - and double-check - that they are connected in the right direction ..

:wink:
IanP

 

[Pjdd]

There's nothing wrong with your circuit. Maybe you made a mistake in your actual wiring. Double-check the polarities of the diodes and the two 2200/25 capacitors.

One further suggestion which is not about why your diodes got burnt: The 1N4007 is a 1-amp diode and four of them in a bridge rectifier can theoretically supply 2A. But if you intend to use the power supply at anything close to 2A, it's better to use diodes of a higher current rating. The 1N540x series are 3-amp diodes and are also cheap and widely available. Here x stands for specific numbers from 0 to 8, according to their voltage ratings as with the 1N400x series.

 

[cutedrummerboy]

thanks all for your suggestion. i will check it. i have one more question, why we use 8 diode in a single bridge? i saw that there is two parallel diode in every arm of some bridge. can anyone explain me this?

 

[ALERTLINKS]

why we use 8 diode in a single bridge

Just to increase current handling. Still cost less in contrast to using hi current rectifiers.

 

[Pjdd]

Paralleling two diodes increases current rating. Theoretically, 2 diodes in parallel can carry twice the current and two 1N4007 could carry 2A, but that's not quite so in practice. Unless the two diodes are specially matched (or some form of equalizing circuit is used), they are likely to have small differences and will not share the current equally. Therefore it's not a good idea to use two diodes in parallel at more than about 1.5 times the maximum rating of one diode.

 

[cutedrummerboy]

thank you all. i understand it. now i am going to build my power supply. i am planning to add a voltmeter and a ammeter to it also. pjdd can you tell me why in some power supply there .1uf paralleled with every diode? is it good or bad?

 

[RetroTechie]

:!: Also 1N4007 can overheat while soldering, because it has relatively thick wires that conduct heat to the silicon easily. When you're not aware of this, it's better to leave longer wire ends on the diodes, read: put them higher above circuit board with longer wires going down. This makes that the silicon itself doesn't overheat as easily when you're soldering the wire ends.

1N4007 is no good if you draw 2A, better use 3A diodes like 1N540x series that Pjdd suggested. Or use a >=2A bridge rectifier... :-D

pjdd can you tell me why in some power supply there .1uf paralleled with every diode? is it good or bad?

These serve to suppress electrical noise (resulting from high-frequency current changes through the diodes), either coming in from AC side, or (less so) going out from power supply to transformer. For most applications these aren't necessary. If added, .1uF is on the high side, something from 100pF to a couple nF's should do fine.

 

[cutedrummerboy]

thank you all. now my problem is solved.

 

[mvs sarma]

always use 3 amp diodes like 1N540x or FR306 etc to make a bridge for 2 amps load.
we cant expect 1amp diodes in bridge to deliver 2 amps , which amounts that the diodes are tried at 100% continuous load. they become hot. instead of paralleling diodes, use higher current ones.

 

[cutedrummerboy]

Thank you sharma jee

 

[Tahmid]

Since you have stated that it's a 16 volt power supply, have you designed the regulator stage yet?

For 2A load, use 3A diodes like 1N5408 (1N540x). Better still, why not just use a bridge rectifier? How much more is that going to cost? Not that much more.

Hope this helps.
Tahmid.

 

[mvs sarma]

yes, he can use a bridge.
but unless one makes a bridge using diodes, properly, perhaps one won't enjoy. i saw many times people can't make a sch of bridge properly.

 

[cutedrummerboy]

sharma jee the bridge connection was correct and thamid, the regulator stage is designed with LM317 and it is correct. i had found that the problem was 1N4007 can not take load of 2 amp. now i am using 1N5402 and i am quit satisfied with my power supply.... bridge rectifier is more costly than four 1N5402

 

[Pjdd]

.... bridge rectifier is more costly than four 1N5402

That's usually the case. Besides, my experience over the years in designing and repairing has been that bridge rectifier modules fail more often than a bridge made up of four discrete diodes of equivalent ratings. This is why I always use discrete diodes in my designs wherever practicable.

 

[Tahmid]

That's usually the case. Besides, my experience over the years in designing and repairing has been that bridge rectifier modules fail more often than a bridge made up of four discrete diodes of equivalent ratings. This is why I always use discrete diodes in my designs wherever practicable.

My experience has been quite the opposite. I've hardly ever had bridge rectifier module failures, and more discrete diode failures. But if your circuit is running satisfactorily, then it's all good. No need to change anything.

 

[mvs sarma]

That is fine, I was just elaborating that in general, we better make few discrete bridge connections. btw, we save money in case of damage to bridge as replacement of individual diodes works cheaper. it is true that 1 amp diodes in bridge formation can handle 2 amps load as each half wave is taken by different diode pair. However, we should have our safety margin and we should not work at full spec of the component.

@Tahmid,
It is question of gaining experience boss !! many members here are into production engineering.

 

[Li_ereunpisan]

using IC regulATOR 7815.....

 

[poorchava]

Use an integrated diode bridge. You can buy one with several amps rating for $1-2.

 

[mvs sarma]

perhaps 4 diodes for the same function together cost only a fraction of a $ . and the member be a student or hobbyist has a practice. I was indicating many times, many who want to make things that are dam cheap in local market, are only doing for leaning.