Want to Boost Current Output of LM2595 simple switcher?

[grtbluyonder]

The LM2595 simple switcher has a current limit of 1amp. It looks like you could boost it's current capabilities by adding either a bipolar transistor or a power mosfet to the output pin 1 , linked to +Vin and use this to drive the inductor/diode/cap output. Has anyone tried this and if so, what were the results and problems if any?

Of course a different higher current inductor would have to be selected but this is no big deal.

 

[alexan_e]

How much current do you need?
You can use LM2596 for 3A or LM2678 for 5A

 

[grtbluyonder]

How much current do you need?
You can use LM2596 for 3A or LM2678 for 5A

Yes I could but I have a whole tube of LM2595's and want to use them up. Have none of the others.

I'm only after 3 amps.

 

[mtwieg]

Using an external NPN to form a darlington with the internal BJTs should work in principle, but you will lose efficiency due to the higher saturation voltage of the darlington, and your switching speeds will probably suffer somewhat. Turn off of the external NPN may be excessively slow, causing poor performance. A FET would be faster, but will have more conduction losses due to a higher Vthresh.

 

[grtbluyonder]

Thanks, I assumed the efficiency and switching speed would suffer, still it should be a lot better than a linear regulator, Vmax 16 V to 5Volts at 3 Amps.

I'm just etching a pcb to try it with an external NPN or FET. I can always look for a 2596 if the sky falls in.