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reducing heat in voltage regulator

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bagavathi

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hi friends,
i m using 7812 regulator for convert 24vdc to 12vdc . it produce heat. i used heat sink also but still it produce heat. wat can i do for reduce the heat . pls say if any change or any other option to reduce the heat .
 

To reduce the heat, you need to use a switching regulator or improve heatsinking and heat dissipation techniques. However, I think, it's better to use a switching regulator. You can use the common LM2575. There are many many switching regulators out there. LM2575 is very common and since it's switching, it will be much more efficient than a 7812, especially with a 24V input, which means, lower heat.

You can also take a look at L4971, L4962, etc.

Hope this helps.
Tahmid.
 
Hello bagavathi
How much is your current ? for example if your current is about 1 amperes , your dissipation will be about 12W !!!!!! efficiency is about 50 percent !!! you have some way : first way , to use a LM7812K ( it is with better specifications) . and the other , adding an NPN transistor to the out put . and the better way , using a switch mode regulator .
Good luck
Goldsmith
 
goldsmith said:
Hello bagavathi
How much is your current ? for example if your current is about 1 amperes , your dissipation will be about 12W !!!!!! efficiency is about 50 percent !!! you have some way : first way , to use a LM7812K ( it is with better specifications) . and the other , adding an NPN transistor to the out put . and the better way , using a switch mode regulator .
Good luck
Goldsmith
Click to expand...

current is about 1 amperes. after conversion of 12v from 24v i further convert to 5v using 7805. because i need two 5&12 volt. 12v regulater only get heated 5v is not heated why?
 

The voltage drop on the 12v regulator is 24v-12v=12v and if the current is 1A then the consumption is 12W

For the 5v regulator it is 12v-5v= 7v * current

The 5v regulator has both lower voltage drop and lower current since the 12v regulator has to handle the current of both 12v and 5v circuits while the 5v just the 5v current
 
Again the dissipation will be linear and awful . try lm2576 ( you can find it at 5 volt and 12 volt an 3.3 volt and adjustable ) . it's efficiency is about 85 percent ( at least).
Best Wishes
Goldsmith
 
goldsmith said:
Again the dissipation will be linear and awful . try lm2576 ( you can find it at 5 volt and 12 volt an 3.3 volt and adjustable ) . it's efficiency is about 85 percent ( at least).
Best Wishes
Goldsmith
Click to expand...

**broken link removed**
the attachment image is i found from net .it is adjustable. i need 5v& 12v at a time for different circuit . pls say how can i get this two output from single adjustable circuit .
 

These regulators are designed with one output and can only be set to a single selected voltage but since you say that the 5v regular doesn't heat I would suggest to use the switching regulator to get the 12v and then use the 7805 to get the 5v from that.
 
Last edited:
A switching regulator like LM2576 would be a better choice.
97_1328708336.gif
 

The attachment of post #7 was a LM2576 (I have no idea why it is deleted now) and since he wanted two output voltages I have suggested him to use the switching regulator for 12v and the linear one for 5v (from 12v) since from what he said the 7805 don't get hot so apparently the current it provides is low and doesn't justify using a switching regulator with the complexity that this introduces.
 

ALERTLINKS said:
A switching regulator like LM2576 would be a better choice.
97_1328708336.gif
Click to expand...

There's a 12V version of LM2576 available (there are 3.3V, 5V, 12V, 15V, and adjustable output versions). So, the OP can just use that and there's no need for the feedback for variable output.

As Alexan has already said, the 5V section can be made with a 7805 following the output of the LM2576.

Hope this helps.
Tahmid.
 

Tahmid said:
There's a 12V version of LM2576 available (there are 3.3V, 5V, 12V, 15V, and adjustable output versions). So, the OP can just use that and there's no need for the feedback for variable output.

As Alexan has already said, the 5V section can be made with a 7805 following the output of the LM2576.

Hope this helps.
Tahmid.
Click to expand...

for above 1 ampere which regulator . i used lm2575 but still it produce heat what can i do?
its urgent pls help.....
 

Coil can't be smaller resistor type.
79_1328793602.jpg

There are a few unusal parts in this circuit. The 330uH inductor is available from digikey.com as part number TE2017-ND. Other inductors can be used, but they should be designed for use in switching power supplies. Use a 10uF tantalum capacitor in parallel with the output filter electrolytic capacitor . It is possible to use other capacitor combinations, such as a 330uF "Low ESR" type electrolytic capacitor and a 100nF ceramic disk capacitor or a standard 330uF electrolytic capacitor in parallel with a 1nF disk capacitor and a 100nF mylar capacitor. The small value capacitors improve the high frequency rejection of the electrolytic device.
**broken link removed**

Thermometry of +5V Switching regulator (1)
+5V Switching regulator (1)
 
Last edited:

Dear ALERTLINKS
Hi
What the beautiful circuit is that . did you made it ? ( all thing blue !). has the core of your coil gap space ?
Best Wishes
Goldsmith
 

Color spray cans do the trick

---------- Post added at 15:00 ---------- Previous post was at 14:48 ----------
all thing blue
Click to expand...
Color spray cans do the trick. Spray before drilling.
66_1328795606.jpg

No air gap! Its ferrite ring.
95_1328795861.jpg
 
Why when i used toroidal core without gap space , my inductor saturated ? i think the substance of your core is better than mine ? isn't it ?
Regards
Goldsmith
 

bagavathi said:
for above 1 ampere which regulator .
Click to expand...

For upto 3A, you can use LM2576.

i used lm2575 but still it produce heat what can i do?
its urgent pls help.....
Click to expand...

How much heat is produced? Is it as hot as the 7805? Did you mount it on a heatsink? What is the current you took?
 

Tahmid said:
For upto 3A, you can use LM2576.



How much heat is produced? Is it as hot as the 7805? Did you mount it on a heatsink? What is the current you took?
Click to expand...
only lm2575 get heated. 2A current i used. how to check heat from regulator.
 

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