Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-di02.r1000.mx.aol.com (Internet Inbound) with ESMTP id 3FD2D38000085; Tue, 9 Apr 2013 10:50:03 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1UPZrL-0000qB-PC for rs_out_1@blacksheep.org; Tue, 09 Apr 2013 15:49:19 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1UPZrL-0000q2-5Z for rsgb_lf_group@blacksheep.org; Tue, 09 Apr 2013 15:49:19 +0100 Received: from nm1.bt.bullet.mail.ird.yahoo.com ([212.82.108.232]) by relay1.thorcom.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.77) (envelope-from ) id 1UPZrG-0003qo-AB for rsgb_lf_group@blacksheep.org; Tue, 09 Apr 2013 15:49:18 +0100 Received: from [212.82.108.229] by nm1.bt.bullet.mail.ird.yahoo.com with NNFMP; 09 Apr 2013 14:48:53 -0000 Received: from [46.228.39.175] by tm2.bt.bullet.mail.ird.yahoo.com with NNFMP; 09 Apr 2013 14:48:52 -0000 Received: from [127.0.0.1] by smtp116.bt.mail.ir2.yahoo.com with NNFMP; 09 Apr 2013 14:48:52 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=btinternet.com; s=s1024; t=1365518932; bh=bYqV3IWQGIlQZ6Ir/VtDR3T4EVySGSWoJ0Y8iqT6/kg=; h=X-Yahoo-Newman-Id:X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:X-Rocket-Received:Message-ID:From:To:References:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE:X-Antivirus:X-Antivirus-Status; b=xPLwoUbP0rqXwPyWRyU95O1WxolWVlz90fgVoCdY9v16ewdeHsXMGOIy4YbLkzyPjvptNSUlwMeCUi2qgPSB2/chwJ67K5qitBO7asubL4HB3vIh+1A1MofKr/XvACmU3kTjuY24GlBysLCreBLR8ON1M9cRQ9Kc7ejUTyzA2RA= X-Yahoo-Newman-Id: 956368.25598.bm@smtp116.bt.mail.ir2.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: 7ePP73oVM1nOrJP3qjJeqteDiICAFcFT4hqzktyhQ7NDSNj MyI1UV8k7VmoCQ9M7qKO7_fdq6PNU1_su9BFDbkN5TOGDF04rj612KBoBLEV KwFaql3pI.q63Nx6ldHB3cU1FKfAydzsqIrkWmlo_xnwUzt2dd09nLlCCSez aZMYo2pCZA3X.Q9XTrwc9mHMgHJ6PZjqOov9hqLc9lFpR5uDoeiCvuO.yvdk ycSafhU9usP0ghwl4hsWLZvd_NxNohs750zlz3LwnJxrlcRuqcZe93Wh9Jtn Jbv4xIa2elpOf3l1x.vD_awX9dhFd_A2tU1RG_6xdb1L5w2vyS3Y1Wp23E.4 wJcdLIHt9W1gTzs.ks00Y0_S97iJxOrF_KMxcJeYm3bBn4rAhcoh5.KMrmmE JeCDQedTi6ycXAe.ptqC6pcNg9DFwZJ7tbz4BEtuVURl.a_eOskMQqItGJ.l DrG5ypdsqMNfZY1y3OjVIE2V2P_SyJWwfzvHRULVHkZ6xo9m7T1C6xeGT7DU 5lWAsB4lYRFYkPonZWCBaIsXSX4.ghL7F_l15BYX.ICvu6kloGYoMbMPi4vI Q6z.kVA-- X-Yahoo-SMTP: fpz.2VeswBBs59bVshRPmMN51lcO2lgFRIvE4XTqE8dRwOxd70E- X-Rocket-Received: from gnat (alan.melia@86.149.140.116 with login) by smtp116.bt.mail.ir2.yahoo.com with SMTP; 09 Apr 2013 14:48:52 +0000 UTC Message-ID: <91F7973589C74BDC80FAD0361FF22F37@gnat> From: "Alan Melia" To: References: <5164092A.3090803@iup.uni-heidelberg.de> Date: Tue, 9 Apr 2013 15:47:58 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-Antivirus: avast! (VPS 130409-0, 09/04/2013), Outbound message X-Antivirus-Status: Clean X-Spam-Score: 0.0 (/) 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 that might be taking a bit of a risk! A 100v working FET might be ok at 24 V but the recommended minimum rating is 4 times the DC supply for Class D and E. It does mean you have to put up with higher rds(on) but all design has its compromise somewhere. [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [212.82.108.232 listed in list.dnswl.org] 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: 8c16534bff9e7be1d3e99d60b0efbf3e Subject: Re: LF: Re: Hall Effect for Over-current shutdown? Content-Type: multipart/alternative; boundary="----=_NextPart_000_005C_01CE3539.9BFBEDF0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: ** X-Spam-Status: No, hits=2.5 required=5.0 tests=FORGED_MUA_OUTLOOK,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-di02.r1000.mx.aol.com ; domain : btinternet.com DKIM : pass x-aol-sid: 3039ac1da60651642a9b386e X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. ------=_NextPart_000_005C_01CE3539.9BFBEDF0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Stefan that might be taking a bit of a risk! A 100v working FET might = be ok at 24 V but the recommended minimum rating is 4 times the DC = supply for Class D and E. It does mean you have to put up with higher = rds(on) but all design has its compromise somewhere. Alan G3NYK ----- Original Message -----=20 From: Stefan Sch=E4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Tuesday, April 09, 2013 1:27 PM Subject: Re: LF: Re: Hall Effect for Over-current shutdown? Hi Warren,=20 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,=20 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 = 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 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 -----=20 From: Warren Ziegler=20 To: rsgb_lf_group=20 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? --=20 73 Warren K2ORS WD2XGJ=20 WD2XSH/23 WE2XEB/2 WE2XGR/1 =20 --=20 73 Warren K2ORS WD2XGJ=20 WD2XSH/23 WE2XEB/2 WE2XGR/1 ------=_NextPart_000_005C_01CE3539.9BFBEDF0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Stefan that might be taking a bit of = a risk! A=20 100v working FET might be ok at 24 V but the recommended minimum rating = is 4=20 times the DC supply for Class D and E. It does mean you have to put = up with=20 higher rds(on) but all design has its compromise somewhere.
 
Alan
G3NYK
----- Original Message -----
From:=20 Stefan = Sch=E4fer
Sent: Tuesday, April 09, 2013 = 1:27=20 PM
Subject: Re: LF: Re: Hall = Effect for=20 Over-current shutdown?

Hi Warren,

Instead of spending to much effort = to the=20 current sensing my advice is to use other FETs. A 500 V FET at 30 V = supply=20 voltage is a heavy waste of power in the on resistance. For 30 V and a = class=20 D, try e.g. a IRFP3710=20 or IRFP150N=20 . That should work much better.

73, Stefan/DK7FC


Am=20 08.04.2013 21:07, schrieb Warren Ziegler:
Hi Alan,=20

    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=20 case too much current is being draw.
I've modified the output transformer turns ratio to produce = more power=20 at lower supply voltages (I'm using 500V, 55a FETs).
However with the new higher currents and with a new appropriate = value=20 sense resistor its developing a LOT of heat (12 W or so) and needs = to be=20 heat-sinked.
I'm thinking Hall-effect might be more efficient and produce = less heat=20 - I'm pretty sure that others have used Hall effect devices to = protect=20 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=20 over-current?? if it is over-current because a high voltage has=20 welded/melted a short between drain and source, then the = protection=20 wont help ....high currents usually lead to excess heating = ......but what=20 is the real cause? If you really need DC supply protection would = not a=20 high-side current monitor be easier/faster??? The problem then = could be=20 there is enough energy stored in the PA choke to zap the FET = before, or=20 even if, you can disconnect the supply.
 
OK drive fails permanently on might be a = condition=20 it would protect the FETs against with DC coupled = drive
 
Alan G3NYK
-----=20 Original Message -----
From:=20 Warren Ziegler
To:=20 rsgb_lf_group
Sent:=20 Monday, April 08, 2013 7:15 PM Subject:=20 LF: Hall Effect for Over-current shutdown?

Anyone using a Hall effect device for overcurrent = sensing=20 and shutdown in a MOSFET amplifer?

--
73 Warren K2ORS
      =  =20         WD2XGJ
      =  =20         WD2XSH/23
      =  =20         WE2XEB/2
      =  =20         WE2XGR/1

 =20



--
73 Warren K2ORS
        =  =20       WD2XGJ
          =  =20     WD2XSH/23
            =  =20   WE2XEB/2
              =  =20 WE2XGR/1

  = ------=_NextPart_000_005C_01CE3539.9BFBEDF0--