Problem in Regulator Output

[mic5]

I am using a regulator(MC7805ACD2TR4) to convert 28V input into 5V output and that is given to a small circuit. When I power ON, it takes 1A maximum and returns to 300mA. But, at output circuit, i am getting only 2.2V. I have checked my entire circuit for short circuit. Still I cann't track the fault.

Any suggestion please...

 

[blueroomelectronics]

Schematic?

 

[MikeMl]

The regulator is overheating and shutting itself down? If you are drawing 1A at 5V starting from 28V, the regulator is dissipating (28-5)*1 =23Watts, meaning it will get stinking hot. It could only work in this application if it is bolted to a HUGE heatsink, probably about 30cm X 30cm.

 

[SABorn]

Some more data on your circuit would be useful.

You quote 28 volt input but fail to say off what supply, one could guess your 28 volt has a much higher ripple voltage than 28 volts then you are able to measure.
As the 7805 has a max input of 30 volts i well expect you are exceeding this with ripple voltage.

As requested prior a schematic would be useful.

help us help you.

Pete.

 

[mic5]

You are right(Regulator Overheating and shutting down). I have calculated that the circuit initially drawing more than 1A and this regulator section cannot be used. Now I have removed the regulator from the board and using 5V power supply.

Thanks to all for the valuable suggestions.

mic

 

[Boncuk]

After the ripple is removed use an 78S05 regulator.

The 78SXX regulators are designed for 2A current flow.

Boncuk