Return-Path: X-Spam-DCC: paranoid 1290; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, FORGED_RCVD_HELO autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id t7ACEIao024243 for ; Mon, 10 Aug 2015 14:14:18 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ZOlv2-0003za-6J for rs_out_1@blacksheep.org; Mon, 10 Aug 2015 13:11:08 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ZOlv1-0003zR-Ps for rsgb_lf_group@blacksheep.org; Mon, 10 Aug 2015 13:11:07 +0100 Received: from smarthost01b.mail.zen.net.uk ([212.23.1.3]) by relay1.thorcom.net with esmtp (Exim 4.86) (envelope-from ) id 1ZOlu2-0001r6-G4 for rsgb_lf_group@blacksheep.org; Mon, 10 Aug 2015 13:11:06 +0100 Received: from [82.70.254.222] (helo=OfficeWin7.lan) by smarthost01b.mail.zen.net.uk with esmtp (Exim 4.80) (envelope-from ) id 1ZOltq-0003H0-BQ for rsgb_lf_group@blacksheep.org; Mon, 10 Aug 2015 12:09:54 +0000 Date: Mon, 10 Aug 2015 13:09:54 +0100 From: Chris Wilson Organization: Gatesgarth Developments X-Priority: 3 (Normal) Message-ID: <1892164761.20150810130954@chriswilson.tv> To: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 X-Originating-smarthost01b-IP: [82.70.254.222] X-Scan-Signature: 3b8620872b19e25fb6f4dfaf1256edc3 Subject: LF: Protecting a MOSFET driver chip from MOSFET failure? Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit 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-Scanned-By: MIMEDefang 2.56 on 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 3838 10 August 2015 Is there a way of protecting a typical MOSFET driver IC from being taken out by a MOSFET failure in a Class E LF amp? I was experimenting with drive level into my G3YXM 1kW 136 kHz amp and managed to blow 2 of the 4 IRFP450 MOSFET's and half the TC4426 driver chip. I also came to realize that I did not follow my car engineering knowledge, and built the thing with little regard to servicing it, changing the devices was surgically challenging (read a PITA...) and I should perhaps have put them on PCB screw type connector blocks in a more accessible position. If I build another that would be my main change, making repair access far easier! As an aside why would reducing drive to the amp perhaps cause MOSFET failure when TX'ing into a dummy load? I am still trying to find a way to set the over current trip on this, it's by means of a Hall effect sensor looking at the south pole of the ferrite choke CH1. The thing draws 12.5 amps tops when TX'ing into a dummy load, and even with the Hall sensor against the face of the ferrite (and I am sure I have the south pole end, and the correct face of the Hall sensor together), it doesn't trip, diagram at http://www.chriswilson.tv/schematic_modified_2.jpg Am I going to have to put some stonking big resistor on the output end of the choke and try and make it draw more current momentarily? Thanks, and thanks for a most entertaining "LF Weekend" sadly I was not able to get an antenna sorted in time. -- Best regards, Chris mailto:chris@chriswilson.tv