Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dk06.r1000.mx.aol.com (Internet Inbound) with ESMTP id 372B738000091; Tue, 9 Apr 2013 08:28:23 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1UPXeS-0000Yl-1C for rs_out_1@blacksheep.org; Tue, 09 Apr 2013 13:27:52 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1UPXeR-0000Yc-G4 for rsgb_lf_group@blacksheep.org; Tue, 09 Apr 2013 13:27:51 +0100 Received: from relay.uni-heidelberg.de ([129.206.100.212]) by relay1.thorcom.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.77) (envelope-from ) id 1UPXeP-0003Kn-Fj for rsgb_lf_group@blacksheep.org; Tue, 09 Apr 2013 13:27:50 +0100 Received: from freitag.iup.uni-heidelberg.de (freitag.iup.uni-heidelberg.de [129.206.29.204]) by relay.uni-heidelberg.de (8.14.1/8.14.1) with ESMTP id r39CRRJX029386 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Tue, 9 Apr 2013 14:27:27 +0200 Received: from [129.206.22.206] (pc206.iup.uni-heidelberg.de [129.206.22.206]) by freitag.iup.uni-heidelberg.de (8.12.11.20060308/8.11.2) with ESMTP id r39CRQVT028741 for ; Tue, 9 Apr 2013 14:27:26 +0200 Message-ID: <5164092A.3090803@iup.uni-heidelberg.de> Date: Tue, 09 Apr 2013 14:27:22 +0200 From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: In-Reply-To: X-Spam-Score: -3.1 (---) 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 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. [...] Content analysis details: (-3.1 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [129.206.100.212 listed in list.dnswl.org] -2.4 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: b0c81be0f3328ec24fe2fd5b2fd44f86 Subject: Re: LF: Re: Hall Effect for Over-current shutdown? Content-Type: multipart/alternative; boundary="------------000008020603070107080003" 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-sid: 3039ac1db40a516409664978 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. --------------000008020603070107080003 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit 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, > > 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 ----- > *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 > --------------000008020603070107080003 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit 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,

    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 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 -----
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

 
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