Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mj06.r1000.mx.aol.com (Internet Inbound) with ESMTP id 05D8838000089; Tue, 9 Apr 2013 11:24:43 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1UPa30-0000xm-ST for rs_out_1@blacksheep.org; Tue, 09 Apr 2013 16:01:22 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1UPa30-0000xd-8s for rsgb_lf_group@blacksheep.org; Tue, 09 Apr 2013 16:01:22 +0100 Received: from mail-oa0-f48.google.com ([209.85.219.48]) by relay1.thorcom.net with esmtps (TLSv1:RC4-SHA:128) (Exim 4.77) (envelope-from ) id 1UPa2x-0003v4-Vg for rsgb_lf_group@blacksheep.org; Tue, 09 Apr 2013 16:01:21 +0100 Received: by mail-oa0-f48.google.com with SMTP id j1so7377836oag.7 for ; Tue, 09 Apr 2013 08:00:57 -0700 (PDT) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:x-received:in-reply-to:references:date:message-id :subject:from:to:content-type; bh=mIONyNXy2MHnlSkciCRb3O+Rlv/Lysatta0QUSRy8Xc=; b=xXAAne+oKd0ZlqQu5PRVRt/FrUfgjWQ1pf2lweBCraGpP3GYDYw5rLEi8YQYu0fnRy w33jsrx9VRwCQG/jGdhDiLD7gHqTHoLzm6coHFucBUd7cfhdffu9qkF8R5KHKdVz7+r+ D3Z/o84vSpkulsUA4R3URT5J7WZHPjK8akJeHubHvESkEyPogsq8m4LNK/vGYtEXN+Er iyuhP23DHL+4i8X4JFBiE9H7rgfVB6IU48dSFR7JhOMlI7Y2QZ/nsY8Hpz8zo4u2tEkb tJgeMBKfACS31JSydDPCxpfxsmaMXe9ZXE1finoqVEDB+YsmjXRicbSJz0ImH+x+Xqx2 TJKQ== MIME-Version: 1.0 X-Received: by 10.60.121.104 with SMTP id lj8mr1679228oeb.83.1365519657826; Tue, 09 Apr 2013 08:00:57 -0700 (PDT) Received: by 10.60.135.199 with HTTP; Tue, 9 Apr 2013 08:00:57 -0700 (PDT) In-Reply-To: <5164092A.3090803@iup.uni-heidelberg.de> References: <5164092A.3090803@iup.uni-heidelberg.de> Date: Tue, 9 Apr 2013 11:00:57 -0400 Message-ID: From: Warren Ziegler To: rsgb_lf_group X-Spam-Score: -0.7 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Hi Stefan, 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. But what I am looking for is for 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. [...] Content analysis details: (-0.7 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [209.85.219.48 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (wd2xgj[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: b64e297c4577ad617411a4f8f6174ca7 Subject: Re: LF: Re: Hall Effect for Over-current shutdown? Content-Type: multipart/alternative; boundary=047d7b3a9734237d5f04d9eed243 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=HTML_30_40, HTML_FONTCOLOR_UNSAFE,HTML_MESSAGE autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false x-aol-global-disposition: G X-AOL-SCOLL-AUTHENTICATION: mtain-mj06.r1000.mx.aol.com ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d7b9a516432bb60cb X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none --047d7b3a9734237d5f04d9eed243 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hi Stefan, 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. But what I am looking for is for 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. 73 Warren On Tue, Apr 9, 2013 at 8:27 AM, Stefan Sch=E4fer < 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 IRFP3710or > IRFP150N. That should work much better. > > 73, Stefan/DK7FC > > > Am 08.04.2013 21:07, schrieb Warren Ziegler: > > Hi Alan, > > I've modified the G0MRF amp with the M0BMU output configuration, I'm > using a 30V supply. > The G0MRF uses a current sense resistor to shut down the amp quickly in > case too much current is being draw. > I've modified the output transformer turns ratio to produce more power at > lower supply voltages (I'm using 500V, 55a FETs). > However with the new higher currents and with a new appropriate value > sense resistor its developing a LOT of heat (12 W or so) and needs to be > heat-sinked. > I'm thinking Hall-effect might be more efficient and produce less heat - > I'm pretty sure that others have used Hall effect devices to protect MOSF= ET > amplifier and I'm looking for circuit tips. > > 73 & Tnx! > Warren > > > > > On Mon, Apr 8, 2013 at 2:52 PM, Alan Melia wro= te: > >> Ah interesting problem Warren.... why is it over-current?? if it is >> over-current because a high voltage has welded/melted a short between dr= ain >> and source, then the protection wont help ....high currents usually lead= to >> excess heating ......but what is the real cause? If you really need DC >> supply protection would not a high-side current monitor be easier/faster= ??? >> The problem then could be there is enough energy stored in the PA choke = to >> zap the FET before, or even if, you can disconnect the supply. >> >> OK drive fails permanently on might be a condition it would protect the >> FETs against with DC coupled drive >> >> Alan G3NYK >> >> ----- Original Message ----- >> *From:* Warren Ziegler >> *To:* rsgb_lf_group >> *Sent:* Monday, April 08, 2013 7:15 PM >> *Subject:* LF: Hall Effect for Over-current shutdown? >> >> Anyone using a Hall effect device for overcurrent sensing and shutdown >> in a MOSFET amplifer? >> >> -- >> 73 Warren K2ORS >> WD2XGJ >> WD2XSH/23 >> WE2XEB/2 >> WE2XGR/1 >> >> >> >> > > > -- > 73 Warren K2ORS > WD2XGJ > WD2XSH/23 > WE2XEB/2 > WE2XGR/1 > > > > --=20 73 Warren K2ORS WD2XGJ WD2XSH/23 WE2XEB/2 WE2XGR/1 --047d7b3a9734237d5f04d9eed243 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Hi Stefan,

=A0 =A0 =A0I think you= are advocating higher voltage and lower current to decrease loss in the FE= T due to the on resistance which is a good idea.

=
But =A0what I am looking for is for =A0over-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.

73 Warren

<= div class=3D"gmail_extra">

On Tue, Apr 9,= 2013 at 8:27 AM, Stefan Sch=E4fer <Stefan.Schaefer@iu= p.uni-heidelberg.de> wrote:
=20
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 or IRFP150N . That should work much better.

73, Stefan/DK7FC


Am 08.04.2013 21:07, schrieb Warren Ziegler:

Hi Alan,

=A0 =A0 I've modified the G0MRF amp with the M0BMU output configuration, I'm using a 30V supply.
The G0MRF uses a current sense resistor to shut down the amp quickly in case too much current is being draw.
I've modified the output transformer turns ratio to produce more power at lower supply voltages (I'm using 500V, 55a FETs).=
However with the new higher currents and with a new appropriate value sense resistor its developing a LOT of heat (12 W or so) and needs to be heat-sinked.
I'm thinking Hall-effect might be more efficient and produce less heat - I'm pretty sure that others have used Hall effect devices to protect MOSFET amplifier and I'm looking for circuit tips.

73 & Tnx!
Warren




On Mon, Apr 8, 2013 at 2:52 PM, Alan Melia <alan.melia@btinternet.com> wrote:
Ah interesting problem Warren.... why is it over-current?? if it is over-current because a high voltage has welded/melted a short between drain and source, then=A0the protection wont help ....high currents usually lead to excess heating ......but what is the real cause? If you really need DC supply protection would not a high-side current monitor be easier/faster??? The problem then could be there is enough energy stored in the PA choke to zap the FET before, or even if,=A0you can disconnect the supply.
=A0
OK drive fails permanently on might be a condition it would protect the FETs against with DC coupled drive
=A0
Alan G3NYK
----- Original Message -----
Sent: Monday, April 08, 2013 7:15 PM
Subject: LF: Hall Effect for Over-current shutdown?

Anyone using a Hall effect device for overcurrent sensing and shutdown in a MOSFET amplifer?

--
73 Warren K2ORS
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XGJ
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XSH/23
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XEB/2
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XGR/1

=A0



--
73 Warren K2ORS
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XGJ
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XSH/23
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XEB/2
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XGR/1

=A0



--
73 Warren K2= ORS
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XGJ
=A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 WD2XSH/23
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XEB/2
=A0 =A0 = =A0 =A0 =A0 =A0 =A0 =A0 WE2XGR/1

=A0 --047d7b3a9734237d5f04d9eed243--