I have a solar panel and an external power source feeding into a DC converter (U10) that are both used to feed a battery charger (U2):

enter image description here

In a previous design I used 2 schottki diodes to prevent back feeding from solar to U10 and from U10 to solar.

But as the schottky has a voltage drop I would like to use a different solution with as little power loss as possible.

Any tip on how to design this?


  • \$\begingroup\$ Using an ideal diode. The circuit generates only 20mV voltage drop. \$\endgroup\$ – Marko Buršič Feb 28 '19 at 11:13
  • \$\begingroup\$ just wondering.... suppose the external power is connected AND solar panel is generating a minumum amount of power and gets to 3 volts, it opens the diode. Will the higher voltage on "OUT" pin of the diode close the ideal diode preventing feedback to the solar panel? \$\endgroup\$ – Vorstendom Feb 28 '19 at 12:07
  • \$\begingroup\$ Ideal diode circuits for example LTC4358 do always apply such voltage on gate, so that there is a minimal yet operational/detectable forward voltage drop. It works as variable resistor, if the voltage tends to be smaller or even negative it forces the MOSFET to reach high resistance and stop conducting. \$\endgroup\$ – Marko Buršič Feb 28 '19 at 12:37

You can use a mosfet to act as a diode like in this article

It is also covered in this post check the answer of Russel which link to this article

Using a MOSFET in place of a diode provides a resistive channel so that voltage drop is proportional to current and can be much lower than for a diode.

The question is also discussed here

enter image description here

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  • \$\begingroup\$ thx, as I am using max 500 mA at 5V I think the ideal diode is the best option, thx Marco! \$\endgroup\$ – Vorstendom Feb 28 '19 at 11:50

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