DC to DC converter ( high current )

[Ginnyyk]

78t05 heatsink

Hi,

I'm trying to convert 12V to 5V with linear regulator( 78T05 ). Since the circuit need almost 3A current, I found that the regulator is at very high temperature even heatsink is used. After some time, the system is shut down and restart automatically.

Does anyone have any suggestions to solve this problem?

Thank you.

 

[Eugen_E]

Use a big enough heatsink, 7805 has a thermal protection and is shut down when the temperature is to high. For bigger current you may use an external transistor.

The best solution to minimize power dissipation is a switching regulator like this:

http://www.elecfree.com/electronic/5v-3a-switching-power-supply-by-lm2576/
**broken link removed**

 

[Ginnyyk]

Thank you for your advice.

Can you tell more on adding transistor for larger current? I have no idea on it.

 

[Eugen_E]

For increasing output current, use the schematic in this link, page 12.

https://www.ortodoxism.ro/datasheets/nationalsemiconductor/LM78XX.pdf

If you choose IREGMAX low, 7805 may not need a heatsink. The transistor however will need adequate heatsink, so you can't eliminate the big heatsink, because it's a linear regulator.
The 78T05 should handle I<3A, with a big heatsink.
If you don't have space for heatsink, switching regulator - previous post - is the only option.

 

[rvionics]

You can use national semiconductors buck converter Ics to reduce the Linear
loses in the pass element.

 

[Ginnyyk]

Hi,

Thank you for all your suggestions.

At last, I tried to regulate the circuit with LM2576. However, when the load is connected, the inductor is burnt out. Why does it happen? Please give me some ideas on it.

Thank you.

 

[rvionics]

Please check the inductors current rating as it has to handle peak switching currents.