Return-Path: X-Spam-DCC: paranoid 1290; Body=3 Fuz1=3 Fuz2=3 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, FORGED_RCVD_HELO,SUBJ_RE_NUM 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 t7AF4YPH025719 for ; Mon, 10 Aug 2015 17:04:34 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ZOoZc-0004vl-II for rs_out_1@blacksheep.org; Mon, 10 Aug 2015 16:01:12 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ZOoZc-0004vc-9r for rsgb_lf_group@blacksheep.org; Mon, 10 Aug 2015 16:01:12 +0100 Received: from smarthost01d.mail.zen.net.uk ([212.23.1.7]) by relay1.thorcom.net with esmtp (Exim 4.86) (envelope-from ) id 1ZOoYY-0002UQ-38 for rsgb_lf_group@blacksheep.org; Mon, 10 Aug 2015 16:01:11 +0100 Received: from [82.70.254.222] (helo=OfficeWin7.lan) by smarthost01d.mail.zen.net.uk with esmtp (Exim 4.80) (envelope-from ) id 1ZOoYL-0001Wd-No for rsgb_lf_group@blacksheep.org; Mon, 10 Aug 2015 14:59:53 +0000 Date: Mon, 10 Aug 2015 15:59:53 +0100 From: Chris Wilson Organization: Gatesgarth Developments X-Priority: 3 (Normal) Message-ID: <859642924.20150810155953@chriswilson.tv> To: Rik Strobbe In-Reply-To: <7E7DFBB4D102A04DB5ADC88D66628A4A443E0BC1@ICTS-S-MBX1.luna.kuleuven.be> References: <1892164761.20150810130954@chriswilson.tv> , <7E7DFBB4D102A04DB5ADC88D66628A4A443E0BC1@ICTS-S-MBX1.luna.kuleuven.be> MIME-Version: 1.0 X-Originating-smarthost01d-IP: [82.70.254.222] X-Scan-Signature: 739d4fb39bd02fc5a2de5437a39bb056 Subject: Re[2]: 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: 3845 Hello Rik, Monday, August 10, 2015 > Maybe also worth to mention: Capacitive coupling of the driver to > the gate will reduce the peak voltage at the gate by half (assuming 50% duty cycle). > > The IC driver voltage should be at least 12V in order to ensure proper switching of the MOSFET. > > If you use a transformer (as suggested by Stefan) one can fiddle > with the transformer ratio to get the proper voltage at the gate. > > > > 73, Rik ON7YD - OR7T Hi Rik, thanks for that, I link to a `scope shot of the gate waveform, taken with a X10 probe, but the `scope does not auto compensate, so an 8V P to P signal I believe? Would that level accept the 50% loss with capacitive coupling? The pdf for the IRFP450's is also linked. The capacitors sound an easy mod... But I don't want to upset the apple cart with ill conceived changes :) Thanks. http://www.chriswilson.tv/gate_waveform._x10_probe.jpg http://www.chriswilson.tv/IRFP450.pdf -- Best regards, Chris mailto:chris@chriswilson.tv