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Date: Tue, 09 Apr 2013 17:42:04 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: Re: Hall Effect for Over-current shutdown?
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Hi Warren,

What is the value of the shunt resistor?

73, Stefan

Am 09.04.2013 17:00, schrieb Warren Ziegler:
> Hi Stefan,
>
>      I think you are advocating higher voltage and lower current to=20
> decrease loss in the FET due to the on resistance which is a good idea.
>
> But  what I am looking for is for  over-current protection which would=20
> be valuable in any class-D design regardless of the choice of FETs. As=20
> Alan has pointed out the wrong output impedance can cause the amp to=20
> draw large currents. I am now using a current sense resistor but I was=20
> thinking that Hall Effect might be more efficient.
>
> 73 Warren
>
>
>
> On Tue, Apr 9, 2013 at 8:27 AM, Stefan Sch=E4fer=20
> <Stefan.Schaefer@iup.uni-heidelberg.de=20
> <mailto:Stefan.Schaefer@iup.uni-heidelberg.de>> wrote:
>
>     Hi Warren,
>
>     Instead of spending to much effort to the current sensing my
>     advice is to use other FETs. A 500 V FET at 30 V supply voltage is
>     a heavy waste of power in the on resistance. For 30 V and a class
>     D, try e.g. a IRFP3710
>     <https://dl.dropbox.com/u/19882028/Datenbl%C3%A4tter/irfp3710.pdf>
>     or IRFP150N
>     <https://dl.dropbox.com/u/19882028/Datenbl%C3%A4tter/irfp150n.pdf>
>     . That should work much better.
>
>     73, Stefan/DK7FC
>

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Hi Warren, <br>
<br>
What is the value of the shunt resistor?<br>
<br>
73, Stefan<br>
<br>
Am 09.04.2013 17:00, schrieb Warren Ziegler:
<blockquote
 cite="mid:CAMFjj71USWsQmU9CYQkf1PwpJFa9MBx39q6NVWx86z=Rcra2+Q@mail.gmail.com"
 type="cite">
  <div dir="ltr">Hi Stefan,
  <div><br>
  </div>
  <div style="">&nbsp; &nbsp; &nbsp;I think you are advocating higher voltage and
lower current to decrease loss in the FET due to the on resistance
which is a good idea.</div>
  <div style=""><br>
  </div>
  <div style="">But &nbsp;what I am looking for is for &nbsp;over-current
protection which would be valuable in any class-D design regardless of
the choice of FETs. As Alan has pointed out the wrong output impedance
can cause the amp to draw large currents. I am now using a current
sense resistor but I was thinking that Hall Effect might be more
efficient.</div>
  <div style=""><br>
  </div>
  <div style="">73 Warren</div>
  <div style=""><br>
  </div>
  </div>
  <div class="gmail_extra"><br>
  <br>
  <div class="gmail_quote">On Tue, Apr 9, 2013 at 8:27 AM, Stefan
Sch&auml;fer <span dir="ltr">&lt;<a moz-do-not-send="true"
 href="mailto:Stefan.Schaefer@iup.uni-heidelberg.de" target="_blank">Stefan.Schaefer@iup.uni-heidelberg.de</a>&gt;</span>
wrote:<br>
  <blockquote class="gmail_quote"
 style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
    <div bgcolor="#ffffff" text="#000000">
Hi Warren, <br>
    <br>
Instead of spending to much effort to the current sensing my advice is
to use other FETs. A 500 V FET at 30 V supply voltage is a heavy waste
of power in the on resistance. For 30 V and a class D, try e.g. a <a
 moz-do-not-send="true"
 href="https://dl.dropbox.com/u/19882028/Datenbl%C3%A4tter/irfp3710.pdf"
 target="_blank">IRFP3710</a>
or <a moz-do-not-send="true"
 href="https://dl.dropbox.com/u/19882028/Datenbl%C3%A4tter/irfp150n.pdf"
 target="_blank">IRFP150N</a>
. That should work much better.<br>
    <br>
73, Stefan/DK7FC</div>
  </blockquote>
  </div>
  </div>
</blockquote>
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