Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id w9E9gXAc020213 for ; Sun, 14 Oct 2018 11:42:35 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1gBcoL-0006Al-MG for rs_out_1@blacksheep.org; Sun, 14 Oct 2018 10:35:45 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1gBco8-0006Ac-6z for rsgb_lf_group@blacksheep.org; Sun, 14 Oct 2018 10:35:32 +0100 Received: from mout02.posteo.de ([185.67.36.66]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91_59-0488984) (envelope-from ) id 1gBco6-0007Rx-2D for rsgb_lf_group@blacksheep.org; Sun, 14 Oct 2018 10:35:30 +0100 Received: from submission (posteo.de [89.146.220.130]) by mout02.posteo.de (Postfix) with ESMTPS id D72F92400FB for ; Sun, 14 Oct 2018 11:35:28 +0200 (CEST) X-DKIM-Result: Domain=posteo.de Result=Signature OK DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.de; s=2017; t=1539509728; bh=Fy+7lMpifPcSh6FTT2Mrv0VFjc4wM+5IpOka05xmup4=; h=Date:From:To:Subject:From; b=pmwMNIACc4SseHkaZ9H5Ulk2luVYiUvsTCjY6i2lNO5q0v63+m9r0of8k7SMRbJ89 i0IYHJYClUo1862cL5Kaaxd4Uog/x9ukBTQRhOR91qLGdYVzrUwFzcUJRuGM/SfanK xzDSCKAPE0p3LT09z9WZI4Pz1sovqW2LJ+22b+adHLg9ir3EIHGZ126nZdn80Hka9s dSTmcN5U6XF4dNDCj5B6MmdgZMM+WfCMptMv9Co31T2PUPpXcL3hB5spN1Dh8hgmiT YLu3LBtfbUaFwsUuNTCk4gmfEoQpaSPdCxaAtUMLdOMX25G0oRdkEno7+RTI8x/980 PVa6lmPNVlaMQ== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 42XxJJ45s6z9rxT for ; Sun, 14 Oct 2018 11:35:28 +0200 (CEST) Message-ID: <5BC30DE0.2070608@posteo.de> Date: Sun, 14 Oct 2018 11:35:28 +0200 From: DK7FC 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: <5BC2FE9C.3080106@posteo.de> <1344457995.20181014100026@gmail.com> In-Reply-To: <1344457995.20181014100026@gmail.com> X-Spam-Score: -2.3 (--) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see @@CONTACT_ADDRESS@@ for details. Content preview: Hi Chris, Can you exclude that this is a driver issue? Because then it is a different story. If the PA is hard keyed, always with a proper waveform (pulsewidth), then i expect no problems. For the problem discussed, i think that the currents are limited by the on-resistance, the inductance of the loop between the components and by the internal resistance of the capacitor. As soon as the current starts to flow, the voltage of the cap will drop, so this will lower the peak current (i.e. it is not the voltage of the cap divided by the on-resistance only). The peak current may be 100 A, but just for some 10 us. And the strong FET will handle this. [...] Content analysis details: (-2.3 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at http://www.dnswl.org/, medium trust [185.67.36.66 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -0.0 T_RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: ebba021850e0a5d4120636e52401e975 Subject: Re: VLF: Class E PA Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=none 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 Hi Chris, Can you exclude that this is a driver issue? Because then it is a different story. If the PA is hard keyed, always with a proper waveform (pulsewidth), then i expect no problems. For the problem discussed, i think that the currents are limited by the on-resistance, the inductance of the loop between the components and by the internal resistance of the capacitor. As soon as the current starts to flow, the voltage of the cap will drop, so this will lower the peak current (i.e. it is not the voltage of the cap divided by the on-resistance only). The peak current may be 100 A, but just for some 10 us. And the strong FET will handle this. 73, Stefan PS: I remember i had similar problems on LF. But that was a driver issue, a wrongly built up comparator circuit. Am 14.10.2018 11:00, schrieb Chris Wilson: > > Hello DK7FC, > > The biggest voltage and current spikes in my W1VD Class d amp are when > a WSPR or OPERA transmission ceases, from back EMF I presume. > > I am curious as tvo whether a "soft voltage start" circuit could be devised > and added to other power supplies similar to the one discussed > earlier? > > Sunday, October 14, 2018, 9:30:20 AM, you wrote: > > >> >> Hi Tom, >> >> Good luck with your PA. >> Tell us the component values when you're finished, as well as the >> actual efficiency. From my LF PA i remember the coil, which was >> quite large already ('air-cored'). >> >> Regarding current peaks at the first switching: I would simply >> ignore the problem and see if the FET will survive (and how old it >> becomes). If it's lifetime is actually to short, then i would start >> thinking about a solution for the problem. One of them just costs 2 >> EUR or so, so it is worth to try... >> >> 73, Stefan >> >> >> >> Am 14.10.2018 00:16, schrieb DK1IS: >> >> Hello group, >> Just to close this thread: >> > >> Concerning the problem of the first drive pulse with DC power >> already on: Bob, W1XP, made an important contribution in a private >> mail. He pointed out that the current spike I was worried about >> would be limited by the FETs output characteristic anyway. Looking >> to the data sheet of my intended IRFB 4227 this seems to be true >> although there could persist a certain limitation by the save >> operation area. Perhaps I was a little bit too naive estimating the >> peak current as Vdc / Rdson ... Be that as it may, using the newly >> discovered DC soft start feature of my power supply should overcome >> this challenge. Controlled by a logic level input it runs up the >> output voltage with a time constant of about 100 ms. This will >> protect the FET, avoid any key clicks and won´t affect the >> readability of the long lasting vlf signals. To keep the signal >> phase constant (essential on vlf) oscillator and gate drive of the FET won´t be keyed at all. >> > >> I´ve just modified the antenna / loading coil system to resonate at >> 8270 Hz without transformers, - 3dB band width now being 168 Hz. >> Including 25 m RG213U from the arbour to the shack (being later on >> part of the matching network) the feeding impedance is now 480 Ohms >> pure resistive which will be matched to the rest of the class E PA >> by its output network. Thus I`m able to omit the two matching >> transformers being used up to now, see www.qrz.com/db/dk1is. >> > >> Now I´m waiting for the driver ICs coming from China - in Germany >> up to now without additional tax ;-) ! >> > >> Thanks for all the feedback, 73, >> Tom, DK1IS >> >> > >