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kender
Joined: 09 Aug 2004
Posts: 768
Location: Silicon Valley
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| How to make a diode? [slightly off-topic] |
 Posted: Wed Jan 12, 2005 10:09 pm |
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Colleagues,
No, this is not a semiconductor processing question. Neither it is a PIC question. I just need to make a circuit, which behaves like a diode wothout a diode drop and can conduct 0.7A; its purpose is to protect the solar panel from the reverse voltage. The best diode I could find was a Schottky with 0.15V drop.
Thanks,
Nick |
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TBrandt
Guest
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| Posted: Wed Jan 12, 2005 10:44 pm |
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What's the reason why you have to omit the dropout of the diode ? Is it just because of the power that you loose or do you need a dedicated minimum voltage - what would be in general a little bit dififcult if you make maximum power point tracking ...
have you thought about using power mosfet with a low RDson in forward (for the reverse voltage) and reverse direction (for the normal operation) with a small sensing circuit in order to stear the gate voltage so that you have a low Rdson in reverse direction for normal operation (0,7 A current) and a closing of the mosfet for reverse voltage ....
I have to admit - a diode is a little bit cheaper ;-) |
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Charlie U
Joined: 09 Sep 2003
Posts: 183
Location: Somewhere under water in the Great Lakes
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newguy
Joined: 24 Jun 2004
Posts: 1909
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| precision rectifier circuit |
| Posted: Wed Jan 12, 2005 10:50 pm |
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You need a precision rectifier, or "superdiode". It's an opamp circuit with two matched diodes that behaves like a perfect, inverting, diode.
I can't figure out how to post pictures here, so my description will have to do.
Imagine a standard inverting op-amp amplifier with a gain of -1. That is, an op-amp whose noninverting input is grounded, and a feedback resistor R from the output to the inverting input. Another resistor R is connected between the inverting input and the signal input.
A precision rectifier is based on this circuit. I'll attempt a crude ascii sketch below.
in-R----------R-------
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|--->|----- |
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-- opamp |-->|-|----out
Please excuse the "quality" of the art. The R's are the two matched resistors, and the >| are the diodes. If this isn't clear (I wouldn't be surprised), email me. I can get you a pdf. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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