Welcome, Guest
Username: Password: Secret Key Remember me

TOPIC: Mini-Tip: Diode Without a Voltage Drop

Re: Mini-Tip: Diode Without a Voltage Drop 7 years 3 months ago #15649

  • majenko
  • majenko's Avatar
  • Offline
  • Fresh Boarder
  • Thanks received: 62

I often find that the 0.7v voltage drop across a diode can be somewhat annoying.

Yes, you can use a Schottky diode to reduce that to 0.3v or so, but still, in a project where every volt counts, 0.3v is a lot of voltage to waste.

Luckily there is a trick you can use in some situations whereby you can have pretty much no voltage drop at all.

The trick is to replace the diode with a P-channel MOSFET in reverse.

Read full article...

Re: Mini-Tip: Diode Without a Voltage Drop 7 years 3 months ago #10696

  • Jon Chandler
  • Jon Chandler's Avatar
  • Offline
  • Moderator
  • Posts: 365
  • Thanks received: 352
This is a great application for a p-channel MOSFET. It's the same circuit shown in

Power Protection Circuits and

Power Protection Circuits - A Closer Look at the P-Channel MOSFET Circuit

In this case, rather than acting to prevent reverse polarity connections, the p-channel MOSFET is acting as a diode to prevent discharging of the battery through the solar cell during periods of darkness.

If you're going to use this circuit at greater than about 12 volts, a slight modification of the circuit is needed to prevent the MOSFET gate voltage limits being exceeded.

http://digital-diy.com/forum/download/file.php?id=1897click here.

Re: Mini-Tip: Diode Without a Voltage Drop 7 years 3 months ago #10697

  • majenko
  • majenko's Avatar
  • Offline
  • Fresh Boarder
  • Thanks received: 62
That's a nice modification there. The circuit I am using has 15v maximum from the solar cells, and a GS limit of +/- 20V, so I'm ok with this one for the time being. But yes, it's good to check your limits and modify accordingly.

Re: Mini-Tip: Diode Without a Voltage Drop 7 years 3 months ago #10724

  • Jon G
  •  Jon G's Avatar
  • Offline
  • Fresh Boarder
  • Thanks received: 33
Excellent!

So, I'm wondering if I can accomplish this task: general-electronics/supplying-power-from-different-locations-t2187.html using two of these? Seems doable to me...

Re: Mini-Tip: Diode Without a Voltage Drop 7 years 3 months ago #10726

  • majenko
  • majenko's Avatar
  • Offline
  • Fresh Boarder
  • Thanks received: 62
I don't see why not - they just act like diodes as long as the potentials are of the right style and you have the ability to pull the gate down below the source.

Re: Mini-Tip: Diode Without a Voltage Drop 7 years 2 days ago #12204

  • markjo
  • markjo's Avatar
  • Offline
  • Fresh Boarder
That's a generality for normal operating currents where the forward drop is typically about 0.65-0.7v, but it varies from that with current.

smt assembly
Time to create page: 0.278 seconds