Return-Path: Received: from mtain-mk03.r1000.mx.aol.com (mtain-mk03.r1000.mx.aol.com [172.29.97.135]) by air-de03.mail.aol.com (v129.4) with ESMTP id MAILINDE031-5eaa4d2f506f2dd; Thu, 13 Jan 2011 14:20:15 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mk03.r1000.mx.aol.com (Internet Inbound) with ESMTP id 74704380000DF; Thu, 13 Jan 2011 14:20:13 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PdShn-00005T-VT for rs_out_1@blacksheep.org; Thu, 13 Jan 2011 19:19:31 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PdShn-00005K-DL for rsgb_lf_group@blacksheep.org; Thu, 13 Jan 2011 19:19:31 +0000 Received: from cavuit02.kulnet.kuleuven.be ([134.58.240.44]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PdShk-000136-VL for rsgb_lf_group@blacksheep.org; Thu, 13 Jan 2011 19:19:31 +0000 Received: from smtps02.kuleuven.be (smtpshost02.kulnet.kuleuven.be [134.58.240.75]) by cavuit02.kulnet.kuleuven.be (Postfix) with ESMTP id 57BF775A0D2 for ; Thu, 13 Jan 2011 20:19:17 +0100 (CET) Received: from ICTS-S-HUB-N3.luna.kuleuven.be (icts-s-hub-n3.luna.kuleuven.be [10.112.9.13]) by smtps02.kuleuven.be (Postfix) with ESMTP id 498A3F3862 for ; Thu, 13 Jan 2011 20:19:17 +0100 (CET) Received: from ICTS-S-EXC2-CA.luna.kuleuven.be ([10.112.11.13]) by ICTS-S-HUB-N3.luna.kuleuven.be ([10.112.9.13]) with mapi; Thu, 13 Jan 2011 20:19:17 +0100 X-Kuleuven: This mail passed the K.U.Leuven mailcluster From: Rik Strobbe To: "rsgb_lf_group@blacksheep.org" Date: Thu, 13 Jan 2011 20:19:16 +0100 Thread-Topic: LF: Re: Re: FET RDS Thread-Index: AcuzS2TJlrZAWR6AR5+bPSgRCmy8ZQACKGpe Message-ID: References: <003801cbb33e$8b59e620$0401a8c0@xphd97xgq27nyf> <004001cbb349$8b4ec190$0401a8c0@xphd97xgq27nyf>, In-Reply-To: Accept-Language: nl-NL, nl-BE Content-Language: nl-BE X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: nl-NL, nl-BE MIME-Version: 1.0 X-KULeuven-Information: Katholieke Universiteit Leuven X-KULeuven-Scanned: Found to be clean X-KULeuven-Envelope-From: rik.strobbe@fys.kuleuven.be X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: RE: LF: Re: Re: FET RDS Content-Type: multipart/alternative; boundary="_000_BF4A524700075746A6467658DFC7102C88715AEA66ICTSSEXC2CAlu_" 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 x-aol-global-disposition: G x-aol-sid: 3039ac1d61874d2f506d3138 X-AOL-IP: 195.171.43.25 X-Mailer: Unknown (No Version) --_000_BF4A524700075746A6467658DFC7102C88715AEA66ICTSSEXC2CAlu_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Andy, I agree. I just had a look in experiment logbook. In 2002 I did build a 137kHz clas= s E PA using a single IRF640 and got 255W output at 56V and 4.9A input (= =3D 275W input), so efficiency was almost 93%. Initially efficiency was mu= ch lower (85%) mainly caused by the inductances. After rewinding them it= was OK. For comparison: my push pull class D PA (clone of the G3YXM design) had= an effiency of 86% on 137kHz (430W out at 56V / 8.9A). Later I modified= this PA to 500kHz where I get 80% effeciency (350W out at 56V / 7.8A). Ag= ain a significant part of the losses are in the coils of the LPF that get= quite hot in QRSS mode or after longer CW transmissions. 73, Rik ON7YD - OR7T ________________________________ Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.or= g] namens Andy Talbot [andy.g4jnt@gmail.com] Verzonden: donderdag 13 januari 2011 18:55 Aan: rsgb_lf_group@blacksheep.org Onderwerp: Re: LF: Re: Re: FET RDS If I can get 80% for 400V on 500kHz using a pair of cheap and cheerful FET= s cobbled together, 90% plus should be easy-enough by spending a bit of ti= me and effort on their selection. A while back I managed greater than 85% on a 20W class E topband PA, and= that is an overall efficiency figure, including power taken by driver st= ages and dropped in linear regulators. So its hardly rocket science. Andy www.g4jnt.com On 13 January 2011 17:44, mal hamilton > wrote: Jim What you say is correct but it is virtually impossible to achieve the 90% plus efficiency claimed by some. The FET required in practice is not available and these high efficiencies are only theoritical. I have found this in practice ie 80% if you are lucky on a good day mal/g3kev ----- Original Message ----- From: "James Moritz" > To: > Sent: Thursday, January 13, 2011 5:31 PM Subject: LF: Re: FET RDS > Dear Mal, Andy, LF Group, > > There is a trade-off in construction of MOSFETs - basically, for a given > area of silicon, higher BVdss requires a thicker active region of the > MOSFET with higher on resistance. You can reduce Rdson by using a greate= r > chip area, but that means higher capacitances, increased cost, etc. So= you > can't have your cake and eat it. > > In Andy's breadboard circuit, there is a mismatch between the available > MOSFET type and the available PSU voltage - the 500V BVdss is a bit too high > for a 60V DC supply - the peak voltage in an ideal class E is 3.56 x Vdc= , > perhaps you would allow 5 x Vdc for safety. 300V BVdss mosfets seem a bi= t > thin on the ground, so more efficient schemes might be to increase Vdc= to > about 100V, or reduce it to about 40V and use lower Rdson 200V mosfets. > > Cheers, Jim Moritz > 73 de M0BMU > > > --_000_BF4A524700075746A6467658DFC7102C88715AEA66ICTSSEXC2CAlu_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Andy,
 
I agree.
I just had a look in experiment logb= ook. In 2002 I did build a 137kHz class E PA using a single IRF640 an= d got 255W output at 56V and 4.9A input (=3D 275W input), so efficien= cy was almost 93%. Initially efficiency was much lower (85%) mainly caused by the inductances. After rewinding th= em it was OK.
For comparison: my push pull class= D PA (clone of the G3YXM design)  had an effiency of 86% on 137kHz (430W out at 56V / 8.9A). La= ter I modified this PA to 500kHz where I get 80% effeciency (350W out at= 56V / 7.8A). Again a significant part of the losses are in the= coils of the LPF that get quite hot in QRSS mode or after longer CW transmissions.
 
73, Rik ON7YD - OR7T
Van: owner-rsgb_= lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Andy= Talbot [andy.g4jnt@gmail.com]
Verzonden: donderdag 13 januari 2011 18:55
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: Re: Re: FET RDS

If I can get 80% for 400V on 500kHz using a pair of cheap and ch= eerful FETs cobbled together, 90% plus should be easy-enough by spending= a bit of time and effort on their selection.   
A while back I managed greater than 85% on a 20W class E topband= PA, and that is an overall efficiency figure,  including power taken= by driver stages and dropped in linear regulators. 
So its hardly rocket science.
 
Andy
 


 
On 13 January 2011 17:44, mal hamilton <g3kevmal@talktalk.n= et> wrote:
Jim
What you say is correct but it is virtually impossible to achieve the 90%<= br> plus efficiency claimed by some. The FET required in practice is not
available and these high efficiencies are only theoritical.
I have found this in practice ie 80% if you are lucky on a good day
mal/g3kev


----- Original Message -----
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blac= ksheep.org>
Sent: Thursday, January 13, 2011 5:31 PM
Subject: LF: Re: FET RDS


> Dear Mal, Andy, LF Group,
>
> There is a trade-off in construction of MOSFETs - basically, for a gi= ven
> area of silicon,  higher BVdss requires a thicker active region= of the
> MOSFET with higher on resistance. You can reduce Rdson by using a gre= ater
> chip area, but that means higher capacitances, increased cost, etc.= So you
> can't have your cake and eat it.
>
> In Andy's breadboard circuit, there is a mismatch between the availab= le
> MOSFET type and the available PSU voltage - the 500V BVdss is a bit= too
high
> for a 60V DC supply - the peak voltage in an ideal class E is 3.56 x= Vdc,
> perhaps you would allow 5 x Vdc for safety. 300V BVdss mosfets seem= a bit
> thin on the ground, so more efficient schemes might be to increase Vd= c to
> about 100V, or reduce it to about 40V and use lower Rdson 200V mosfet= s.
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
>
>



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