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 x1ODXVIs016642 for ; Sun, 24 Feb 2019 14:33:39 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1gxtqx-0006RO-NG for rs_out_1@blacksheep.org; Sun, 24 Feb 2019 13:29:59 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1gxtqx-0006RF-9K for rsgb_lf_group@blacksheep.org; Sun, 24 Feb 2019 13:29:59 +0000 Received: from mail-ua1-x935.google.com ([2607:f8b0:4864:20::935]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91) (envelope-from ) id 1gxtqu-0003Dp-GW for rsgb_lf_group@blacksheep.org; Sun, 24 Feb 2019 13:29:58 +0000 Received: by mail-ua1-x935.google.com with SMTP id j8so6000733uae.13 for ; Sun, 24 Feb 2019 05:29:56 -0800 (PST) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to; bh=e+VEXJsUhp87tM7p300VMdmHUNfT/shg7FYt8dMbyWw=; b=PBXZxKF/lxmKYQ8F+a9mJ6wonbN+SIxIWss3f5mdS+3KBYrF4AjjEUwIliF1FmuMk8 oEUg9fAvxgQcv3tUvNkULovJ2hbh+YILnoV/P3kfVl78gKE8kg1i5OnO5UiJfQLJ0qPi RUGZlkr+aALQGd/5b/mUWNpn5CJPfZmYch83VMB+RxnK79+tDob65zX/TNGqzVP5Fixg ytiTjk9LzOeSxVDwFupfIyCcJxw0R28+HRPPbvOxArGXpbuEWxogaNfuH5eOg5SXJOms 3oKRudKr7sHS3++4ZkFD8OpekQAVsZ1LbysIqewFDjazU1zz9LI2c9OK8gSf57GDeTHe lwLg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to; bh=e+VEXJsUhp87tM7p300VMdmHUNfT/shg7FYt8dMbyWw=; b=OZnKm2PXThGqZVYdk/vWSxGrmEToILyZc6Ko1ro4V0mZpensuMDA+l1MhviWWt4Q+E Rea2y0nRbNR1xgMllWaxQuQI7rOI4320HJJsRmcmQBWGNeOrZMjO7inrX6cysO6MgrC8 4w+RYsl6d1eGntR2vM7WIj0kRNhoiQZgOeT8kDE5v3+K2Ojw6f9kfnvE6t9VCdVfZNj4 TbsSGd1orWvu5dtJw9hhzTOsLXTSAHTEwq2KzAYxZh/LXtOlwu8rUrVdQfxewCrQl20c GPEoj3rlSwldkdJwPTtMFopXyliHjdRXeMCyd5q0KoAAFEB+UVTuPAyIsIIemq2XzKl5 EQAA== X-Gm-Message-State: AHQUAuZbmmWVjFPk/3uvyt06QL2+eRAsyVs8gtoozsh+CjLkVsp+wiit 2MKDw36q/OZXMLL0/FGmL2rsjp/M3YZ9zXw0aQVDCA== X-Google-Smtp-Source: AHgI3IZhCnksC3CRbl9jWM3fOhRDwwcAQvagv2dTstrSqYU0Pt4Oh4vob+436Vq6EMOsyWl4d/3KCF583zXoTmIPdKk= X-Received: by 2002:a67:7a04:: with SMTP id v4mr6788422vsc.127.1551014994698; Sun, 24 Feb 2019 05:29:54 -0800 (PST) MIME-Version: 1.0 References: <043bec62-8144-5ff3-98a6-9f04699f6a4c@no3m.net> <1551011916482.41235@kuleuven.be> <1551014480338.17397@kuleuven.be> In-Reply-To: <1551014480338.17397@kuleuven.be> From: Andy Talbot Date: Sun, 24 Feb 2019 13:29:35 +0000 Message-ID: To: "rsgb_lf_group@blacksheep.org" X-Spam-Score: 0.0 (/) 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 the administrator of that system for details. Content preview: Why not AC couple your gates. That removes all possibility of latching 100nF in series, reverse biassed diode to ground shunted by 10k or so for DC restoration Or transformer couple Andy www.g4jnt.com Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [2607:f8b0:4864:20:0:0:0:935 listed in] [list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (andy.g4jnt[at]gmail.com) 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: 0c28add2673aaa1c8f62f1695e18ff8b Subject: Re: LF: Re: Class D current spikes Content-Type: multipart/alternative; boundary="000000000000cce6a40582a3d17f" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,HTML_MESSAGE, TO_ADDRESS_EQ_REAL 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 --000000000000cce6a40582a3d17f Content-Type: text/plain; charset="UTF-8" Why not AC couple your gates. That removes all possibility of latching 100nF in series, reverse biassed diode to ground shunted by 10k or so for DC restoration Or transformer couple Andy www.g4jnt.com On Sun, 24 Feb 2019 at 13:24, Rik Strobbe wrote: > Addendum: 3 microseconds is for 472kHz, for a 136kHz PA it should be 10 > microseconds. > > 73, Rik ON7YD - OR7T > > ________________________________________ > Van: owner-rsgb_lf_group@blacksheep.org < > owner-rsgb_lf_group@blacksheep.org> namens Rik Strobbe < > rik.strobbe@kuleuven.be> > Verzonden: zondag 24 februari 2019 13:38 > Aan: rsgb_lf_group@blacksheep.org > Onderwerp: LF: Re: Class D current spikes > > Hello Eric, > > I had a similar problem: > at "key up" one of the driver outputs will remain low and the other high. > As a result the gate of one of the power MOSFETs is kept high for a time > much longer that half a period. During that time this MOSFET is in ON-state > (conducting) and thus drawing excessive current. > I solved the problem by adding monostable multivibrators that disable the > MOSFET driver when one of the driver outputs stays high longer than 3 > microseconds. > > Assuming that you refer to the W1VD "500W RF-deck" ( > http://www.w1vd.com/137-500-500WTX.pdf): it is actually a voltage mode > design (thus having current spikes). > A current mode class D amp has a choke between the supply voltgae and the > output transformer center tap, limiting the current (and causing voltage > spikes). > > 73, Rik ON7YD - OR7T > > ________________________________________ > Van: owner-rsgb_lf_group@blacksheep.org < > owner-rsgb_lf_group@blacksheep.org> namens Eric NO3M > Verzonden: zondag 24 februari 2019 13:08 > Aan: rsgb_lf_group@blacksheep.org > Onderwerp: LF: Class D current spikes > > I recently got a current mode (outp xfmr center tap not bypassed) Class > D amp going on 136khz, basically modeled after the W1VD / G0MRF > circuits. FETs are 59N25s, 4820p / 10ohm snubbers, 5t+5t / 21t 3C90 > 42mm output xfmr, 62uH (25t T157-26) choke. Output xfmr depends on the > power supply in use: > > 30V linear supply: 5t+5t / 21t 3C90 42mm, 300W out > 48V switching supply: 5t + 5t / 16t 3C90 51mm, 500W out > > I am also using the G0MRF keying circuit, ie. P-channel MOSFET (IRF9540) > in the driver (MCP1404) supply line. > > If the driver is left active (key down), the beginning and end of the > input RF envelope produces a "clicking" noise... assume this is from > current spikes being developed and sunk by the FET body diodes? If the > driver is keyed with input RF already applied, thereby interrupting the > drive to the FETs, there is no such behavior. The keying is shaped, > resulting in a ramping of the driver supply voltage and resultant gate > waveforms to the FETs. > > These current spikes do not bother my 30V linear power supply, however, > when I attempt to use a 48V switching supply (rated at 17.7A), it seems > to be OK with the current spike generated on the beginning of the RF > envelope, but not the spike at the end of the envelope and goes into > fault mode. If the driver is keyed with continuous RF applied, it's > happy and does not trip out. But keying the driver doesn't seem > practical for digi modes without some exotic circuitry or engaging > computer generated signaling to key down *after* RF drive is applied and > key up *before* RF drive is removed.... again, this phenomena only > happens at the beginning and end of the input RF envelope. > > Is there way to mitigate these current spikes, especially the one > generated when RF is removed? > > 73 Eric NO3M > > > > > --000000000000cce6a40582a3d17f Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Why not AC couple your gates.=C2=A0 That removes= all possibility of latching
100nF in series, reverse biasse= d diode to ground shunted by 10k or so for DC restoration
= Or transformer couple



On= Sun, 24 Feb 2019 at 13:24, Rik Strobbe <rik.strobbe@kuleuven.be> wrote:
Addendum: 3 microseconds is for 472kHz, = for a 136kHz PA it should be 10 microseconds.

73, Rik=C2=A0 ON7YD - OR7T

________________________________________
Van: owner-rsgb_lf_group@blacksheep.org <owner-rsgb_lf_group@blacksheep.or= g> namens Rik Strobbe <rik.strobbe@kuleuven.be>
Verzonden: zondag 24 februari 2019 13:38
Aan: rsgb= _lf_group@blacksheep.org
Onderwerp: LF: Re: Class D current spikes

Hello Eric,

I had a similar problem:
at "key up" one of the driver outputs will remain low and the oth= er high. As a result the gate of one of the power MOSFETs is kept high for = a time much longer that half a period. During that time this MOSFET is in O= N-state (conducting) and thus drawing excessive current.
I solved the problem by adding monostable multivibrators that disable the M= OSFET driver when one of the driver outputs stays high longer than 3 micros= econds.

Assuming that you refer to the W1VD "500W RF-deck" (= http://www.w1vd.com/137-500-500WTX.pdf): it is actually a voltage mode = design (thus having current spikes).
A current mode class D amp has a choke between the supply voltgae and the o= utput transformer center tap, limiting the current (and causing voltage spi= kes).

73, Rik=C2=A0 ON7YD - OR7T

________________________________________
Van: owner-rsgb_lf_group@blacksheep.org <owner-rsgb_lf_group@blacksheep.or= g> namens Eric NO3M <no3m@no3m.net>
Verzonden: zondag 24 februari 2019 13:08
Aan: rsgb= _lf_group@blacksheep.org
Onderwerp: LF: Class D current spikes

I recently got a current mode (outp xfmr center tap not bypassed) Class
D amp going on 136khz, basically modeled after the W1VD / G0MRF
circuits.=C2=A0 FETs are 59N25s, 4820p / 10ohm snubbers, 5t+5t / 21t 3C90 42mm output xfmr, 62uH (25t T157-26) choke.=C2=A0 Output xfmr depends on th= e
power supply in use:

30V linear supply: 5t+5t / 21t 3C90 42mm, 300W out
48V switching supply: 5t + 5t / 16t 3C90 51mm, 500W out

I am also using the G0MRF keying circuit, ie. P-channel MOSFET (IRF9540) in the driver (MCP1404) supply line.

If the driver is left active (key down), the beginning and end of the
input RF envelope produces a "clicking" noise... assume this is f= rom
current spikes being developed and sunk by the FET body diodes?=C2=A0 If th= e
driver is keyed with input RF already applied, thereby interrupting the
drive to the FETs, there is no such behavior.=C2=A0 The keying is shaped, resulting in a ramping of the driver supply voltage and resultant gate
waveforms to the FETs.

These current spikes do not bother my 30V linear power supply, however,
when I attempt to use a 48V switching supply (rated at 17.7A), it seems
to be OK with the current spike generated on the beginning of the RF
envelope, but not the spike at the end of the envelope and goes into
fault mode.=C2=A0 If the driver is keyed with continuous RF applied, it'= ;s
happy and does not trip out.=C2=A0 But keying the driver doesn't seem practical for digi modes without some exotic circuitry or engaging
computer generated signaling to key down *after* RF drive is applied and key up *before* RF drive is removed.... again, this phenomena only
happens at the beginning and end of the input RF envelope.

Is there way to mitigate these current spikes, especially the one
generated when RF is removed?

73 Eric NO3M




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