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5Volt 2 ampere supply - very hot - cannot use LM2576

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garg29

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Hi friends,
I found the below given circuit diagram for 3A 5 volt power supply, I tried building the same, (with 10 volt input & 2 Amperes Load) it works buts gets up Very Very Hot. must be due to (10volt -5 volt) x 2 = 10Watts of heat dissipation. Can there be a way where I can build some small circuit for 2 amperes 5 volt supply which dosen't waste too much power in form of Heat. I cannot use LM2576.

Thanks regards.
 

5Volt 2 ampere supply

I was going to suggest a National Semi switcher! Why can you not use one?

Keith.
 

5Volt 2 ampere supply

Hi Keith,
Switchers spikes arent over all welcome...
@garg29,
What means pls very hot, & how is cooling soluted?
You see, if you has 7V ac= your buffer C has ca. 9..10V (input to Emiiter), in sum you has ca 10W to dissipate_need a nice heat shink!
K.

Added after 2 minutes:

What you do can?; select some better, so called LowDropOut Regler!
The best are at 0.5..1.2V on the market:)

Added after 2 minutes:

Check by Linear Technology/Micrel/Ti...
 

Re: 5Volt 2 ampere supply

karesz said:
Hi Keith,
Switchers spikes arent over all welcome...
Click to expand...

True, but if you want to drop 5V at 2A and don't want 10W of power dissipation, you need to use them.

The switcher options are:

1. filtering of the output voltage (and screening if it is near some sensitive circuitry and radiated interference is a potential problem)

2. using a switcher followed by linear regulation (and screening if necessary).

Maxim used to do some switching regulators (MAX710, I think) with a built in low dropout regulator - the switcher went to within 100mV of the output voltage. They worked very well - I am not sure if they still do similar things. You can do the same thing yourself with a switcher and LDO.

Keith.
 

5Volt 2 ampere supply

Hi Keith,
Clear_ I dont bhave some problem with the better ifficiencies, I applyed in some projects after regulators too, All these is better for dissipation, not so direct better for place requirements (needs often + EMI filters:-() & mosten are the prices not lower...
Developer has it every time concret to check and calculate_search for an intelligent compromise:).
K.
A good extrem low dropout regulator is i.e. a PNP transistor...
We can buy some extrem quite switcher too...
 

5Volt 2 ampere supply

Thank you guys....but will this be useful...(i found this on EDN site)
 

Re: 5Volt 2 ampere supply

garg29 said:
Thank you guys....but will this be useful...(i found this on EDN site)
Click to expand...

If you don't use a switcher you will still have the heat to get rid of - there is no way round that. That circuit is wrong anyway - the 78L12 can only supply 100mA.

Keith.
 

5Volt 2 ampere supply

ya I saw that 78L12....but the main point is if we put 2 LM7812 in parallel will it be proper way
 

Re: 5Volt 2 ampere supply

garg29 said:
ya I saw that 78L12....but the main point is if we put 2 LM7812 in parallel will it be proper way
Click to expand...

Well you would use two 7805s, but the regulation would not be great due to the diode drops which could be different. There is no guarantee the regulators will share the load equally. I wouldn't do it.

If you really want to stick with a linear regulator just buy one that is man enough for the job and stick a heatsink on it. Personally I would use a switcher plus whatever else is required to get the noise down (filter/LDO after switcher).

Keith.
 

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    garg29

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5Volt 2 ampere supply

Thanks keith for your time & for all the replies. I can't use LM2576 not because of noise but due to some other reason. Is there any other switching regulator(available at reasonable price)?
 

5Volt 2 ampere supply

garg29 said:
Thanks keith for your time & for all the replies. I can't use LM2576 not because of noise but due to some other reason. Is there any other switching regulator(available at reasonable price)?
Click to expand...

Hundreds of them! There are so many it is difficult to choose. Try **broken link removed** and select the "Power" button on their Webench designer at the top right. Put in your requirements and see what comes up.

The last ones I used were Linear Technology LT1308 but they only do 1A (I needed very low Vin <1V). Anyway, Linear Technology would be worth a look.

I used the National LM3478 a couple of years ago for a 4A supply, but it uses an external transistor.

I would say - use the online guides on the manufacturers sites to help you choose - there are so many.

Keith.

Added after 36 minutes:

By the way, the reason for using the web site tools like the one at National is that it will calculate the component values for you.

Keith.
 

5Volt 2 ampere supply - help needed

Hi garg29,
If you are on diverse google settings active: you has (as Keith told it too) X hundreds as candidates...
As I proposed too, check pls i.e. for Micrel LDO regulators, In TO220, they has for ex. 400...600mV drops_ONLY!
These is really not much:):
**broken link removed**
In worse case is LT`s LT1117 pin compatible w. LM317, but has ca. 1.2V dropout (max. 0.8A!)& not 2.5...3V as the original:)...
K.
 

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