5V Linear regulator help

[amayilsamy]

I need 5 V @ 550 mA Linear regulator. And my input voltage is 12 V - 6.5 V. 12 V from SMPS . 6.5 V from Li-Ion Battery.

I already check with LM317 its emits more heat. How to avoid heat? Or Suggest which is more compatible for this?

 

[cameo_2007]

LM317 might also have a drop out voltage which will not let you convert from 6.5V to 5V

Check LM2576 Switching voltage regulator.

 

[BradtheRad]

With 12V supply, a resistive device must drop 7V.
This means it must dissipate 3.5W.
Even if a 317 or 7805 IC could work from 6.5V, they will need a heatsink.

A similar project is discussed at the thread below. (Look for my schematic of a simple NPN-and-zener type regulator.)

https://www.edaboard.com/threads/275291/

 

[Sunny55]

From 6V to 5V, you need a low dropout voltage regulator. Just google around.

 

[amayilsamy]

I don't want go to switching regulator..

How to reduce heat from linear regulator? If there is only chance to provide a heat sink.

Recommend what is the smaller heat sink for 3.5 W power dissipation.

 

[ArNvC]

Just use a small heatsink and fix the regulator onto it. A 7805 should work fine for your requirements, think simple. If you want to build your own regulator ;-) go for a zener diode and a series resistor.

 

[tpetar]

Use MC34063 or some dedicated IC for 5V output.

 

[unitt]

Hi Amayil
A LM1117-5.0 is possible.
Unitt

 

[tpetar]

I need 5 V @ 550 mA Linear regulator. And my input voltage is 12 V - 6.5 V. 12 V from SMPS . 6.5 V from Li-Ion Battery.

I already check with LM317 its emits more heat. How to avoid heat? Or Suggest which is more compatible for this?

For standard linear regulators you need at least 2,5-3V difference between input and output voltages, that means that minimum input voltage what you must to ensure is 8V. Second option is to use LDO regulator. Use adequate heatsink to regulate heat in allowed temperature ranges, and eliminate any spikes from SMPS (filter voltage output from SMPS), that will lower temperature if you have bad spikes in SMPS voltage.

:wink:

 

[1132]

lm2576 is switched mode regulator ic, 7805 is enough for your requirements, to reduce heating use a heat zinc.

 

[betwixt]

A 7805 will NOT work in this case. The input voltage at 6.5V is too low for it to operate. If you use a linear regulator you will produce heat - I'm afraid that's physics and there's nothing we can do about it. The best solution is a small switch mode regulator like the MC34063 as tpetar suggested. It's only 8 components instead of 3 and none of them are expensive.

Brian.

 

[pjmelect]

You need to use the TLE4258 low drop out voltage regulator, with a good heatsink to do what you want. As with all low drop out regulators be sure to decouple the output with preferably a 100uF tantalum capacitor.
Coincidentally I am selling these regulators on eBay UK for only £1 for 5 with £2 P&P (UK only)