LM723 circuit schematic problem

Thread Starter

Nguyễn Duy Mạnh

Joined Apr 25, 2018
26
hello guys. I used LM723 to create a voltage regulator. I`m using this sche behind. I change my VR to desire my voltage. i can handle it from 8v to 15v. I let my output is 8v. But when i connect Load (Load is 100ohm - 5w), the voltage drop out to only 2v. i dont know what exactly my problem is. My darlington transistor can load 5amp. i just put all the components on strip board, not a real board. Can someone explain for me why ?
 

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ArakelTheDragon

Joined Nov 18, 2016
1,353
Its early in the morning, I don't see anything wrong with your circuit (only 1 look is what I did).

A general solution is that your source can not sypply the needed current.
 

Ylli

Joined Nov 13, 2015
1,053
How much current is your 26 V source capable of supplying? Do you have that LED on the input connected? If so, does it dim when you apply the load to the supply or does it remain full brightness?
 

Thread Starter

Nguyễn Duy Mạnh

Joined Apr 25, 2018
26
How much current is your 26 V source capable of supplying? Do you have that LED on the input connected? If so, does it dim when you apply the load to the supply or does it remain full brightness?
i do. i got led at input, my input from a transformer 220VAC/18VAC - 10A, when i through it full bridge, it becomes 26v. when i put load the led at input remains full brightness, but my output drop quickly
 

ericgibbs

Joined Jan 29, 2010
13,614
hi NDM,
You say the input voltage is 26Vdc, the out voltage is 8Vdc and the resistive Load is 100R.??
Is that correct.?
E
 

ericgibbs

Joined Jan 29, 2010
13,614
hi,
OK,
So thats 8V into a 10R Load, ie: 0.8Amps
The Input voltage is 26V, so you have 18V across the 2N3055 at 0.8A, thats 14.4Watts.
Do you have a heat sink on the 2N3055.??
E

EDIT:
Could you post a photo image of the project.?
 

Thread Starter

Nguyễn Duy Mạnh

Joined Apr 25, 2018
26
hi,
OK,
So thats 8V into a 10R Load, ie: 0.8Amps
The Input voltage is 26V, so you have 18V across the 2N3055 at 0.8A, thats 14.4Watts.
Do you have a heat sink on the 2N3055.??
E

EDIT:
Could you post a photo image of the project.?
i can, i didnot put heatsink on 2n3055 now, because i just put it in breadboard, hard to use heatsink
 

Thread Starter

Nguyễn Duy Mạnh

Joined Apr 25, 2018
26
OK,
If you could post a photo it would help, don't worry if it looks a mess.:)
E
Eric, i measure the voltage from the INPUT, it is 26v with no load, but when i put Load, the voltage of input dropout is only 20v. Is that my source can not supply my needed current ? because i only use full bridge with 2A diode?
 

bertus

Joined Apr 5, 2008
21,532
Hello,

Can you post a schematic with all values of the 26 Volts supply?
Perhaps the buffer capacitor is not large enough or the transformer has to less power.

Bertus
 
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