Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dc05.r1000.mx.aol.com (Internet Inbound) with ESMTP id 8CE44380000B8; Mon, 8 Apr 2013 16:23:18 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1UPIa4-0001nb-Vi for rs_out_1@blacksheep.org; Mon, 08 Apr 2013 21:22:20 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1UPIa4-0001nS-7s for rsgb_lf_group@blacksheep.org; Mon, 08 Apr 2013 21:22:20 +0100 Received: from mout2.freenet.de ([195.4.92.92]) by relay1.thorcom.net with esmtps (UNKNOWN:AES256-GCM-SHA384:256) (Exim 4.77) (envelope-from ) id 1UPIa1-00013O-Sz for rsgb_lf_group@blacksheep.org; Mon, 08 Apr 2013 21:22:19 +0100 Received: from [195.4.92.140] (helo=mjail0.freenet.de) by mout2.freenet.de with esmtpa (ID dl4yhf@freenet.de) (port 25) (Exim 4.80.1 #2) id 1UPIZg-0005I3-Fk for rsgb_lf_group@blacksheep.org; Mon, 08 Apr 2013 22:21:56 +0200 Received: from localhost ([::1]:37394 helo=mjail0.freenet.de) by mjail0.freenet.de with esmtpa (ID dl4yhf@freenet.de) (Exim 4.80.1 #2) id 1UPIZg-0000Hk-96 for rsgb_lf_group@blacksheep.org; Mon, 08 Apr 2013 22:21:56 +0200 Received: from [195.4.92.14] (port=38177 helo=4.mx.freenet.de) by mjail0.freenet.de with esmtpa (ID dl4yhf@freenet.de) (Exim 4.80.1 #2) id 1UPIWj-0000Gg-LX for rsgb_lf_group@blacksheep.org; Mon, 08 Apr 2013 22:18:53 +0200 Received: from blfd-4d08800a.pool.mediaways.net ([77.8.128.10]:3919 helo=[192.168.178.22]) by 4.mx.freenet.de with esmtpsa (ID dl4yhf@freenet.de) (TLSv1:DHE-RSA-CAMELLIA256-SHA:256) (port 465) (Exim 4.80.1 #2) id 1UPIWj-0001No-7l for rsgb_lf_group@blacksheep.org; Mon, 08 Apr 2013 22:18:53 +0200 Message-ID: <5163262C.60204@freenet.de> Date: Mon, 08 Apr 2013 22:18:52 +0200 From: wolf_dl4yhf User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:14.0) Gecko/20120713 Thunderbird/14.0 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <7EB77D10460A4EBF9E1F63437A4C99A6@gnat> In-Reply-To: <7EB77D10460A4EBF9E1F63437A4C99A6@gnat> X-Spam-Score: -2.4 (--) 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: .. or wind a few turns of fat copper wire around a 'reed relay' contact tube. Virtually no voltage loss then. I used this for a power supply, but it would work for the DC current feed inside a PA as well. IIRC, the product of number of turns * Amperes was about 50 for the contact to close. [...] Content analysis details: (-2.4 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [195.4.92.92 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (dl4yhf[at]freenet.de) -2.4 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: 85ec4a6bf4b19214eecc06056d1d344b Subject: Re: LF: Re: Hall Effect for Over-current shutdown? Content-Type: multipart/alternative; boundary="------------000206020404080706010406" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.6 required=5.0 tests=HTML_20_30, 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: 3039ac1d408551632736172a X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. --------------000206020404080706010406 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit .. or wind a few turns of fat copper wire around a 'reed relay' contact tube. Virtually no voltage loss then. I used this for a power supply, but it would work for the DC current feed inside a PA as well. IIRC, the product of number of turns * Amperes was about 50 for the contact to close. 73, Wolf . Am 08.04.2013 21:39, schrieb Alan Melia: > Ah yes that is Class D and can go that way if mis-matched......that is > a lot of power in a sensing resistor! I guess a Hall effect device or > even a temp sensor would do that job. I think in over current > condition a lot of power is dissipated in the devices. High side > sensors should be available at 30v The sheets I have seen, > suggest they require some assistance above about 40v. > Alan > > ----- Original Message ----- > *From:* Warren Ziegler > *To:* rsgb_lf_group > *Sent:* Monday, April 08, 2013 8:07 PM > *Subject:* Re: LF: Re: Hall Effect for Over-current shutdown? > > 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 > --------------000206020404080706010406 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit
.. or wind a few turns of fat copper wire around a 'reed relay' contact tube. Virtually no voltage loss then. I used this for a power supply, but it would work for the DC current feed inside a PA as well. IIRC, the product of number of turns * Amperes was about 50 for the contact to close.

73,
   Wolf .

Am 08.04.2013 21:39, schrieb Alan Melia:
Ah yes that is Class D and can go that way if mis-matched......that is a lot of power in a sensing resistor! I guess a Hall effect device or even a temp sensor would do that job. I think in over current condition a lot of power is dissipated in the devices. High side sensors should be available at 30v The sheets I have seen, suggest they require some assistance above about 40v.
 
Alan
----- Original Message -----
Sent: Monday, April 08, 2013 8:07 PM
Subject: Re: LF: Re: Hall Effect for Over-current shutdown?

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

 

--------------000206020404080706010406--