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Reply-To: "Kevin Aylward"
From: "Kevin Aylward"
Subject: Re: Using inductor resistance as current sensor
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Date: Wed, 2 Oct 2002 08:15:13 +0100
NNTP-Posting-Date: Wed, 02 Oct 2002 08:15:21 BST
"John Popelish" wrote in message
> I have had an idea for quite a while that I have never tested. In the
> standard buck regulator, I think one could use the resistance of the
> inductor to perform current limit or current mode control. The
> problem with it is that the small DC voltage drop is riding on the
> large inductive swing. But if the inductor was wound bifilar with one
> heavy conductor and one very fine conductor, with both tied to the
> switch end, and only the heavy conductor tied to the output filter,
> then the voltage difference between the downstream ends would be very
> close to just the resistive drop of the heavy current carrying wire
> with almost none of the inductive EMF. A simple subtractor could
> reference and amplify this small drop to make a control signal. This
> would save the need for a current shunt resistor and its additional
> voltage drop while providing instantaneous inductor current
> information. This measurement would have a positive temperature
> coefficient, but at least it would prevent thermal runaway.
> The post on the low drop current regulator brought this back to the
> Does this sound workable? Would anyone want to volunteer to simulate
> it, or build it to try it out?
Interesting idea. Have you done a patent search on it?
I might have some time to check it out. I am actually working on a
little generic PWM subckt model right at the moment, can't have this
LTSpice getting all the glory in automatic PS design:-)
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
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