Re: LF: Re: Hall Effect for Over-current shutdown?

[Warren Ziegler <wd2xgj@gmail.com>]

Clemens,

  Thank you!

Warren

On Mon, Apr 8, 2013 at 3:42 PM, Clemens Paul <cpaul@gmx.net> wrote:

Hi Warren,

I know a German OM (RF engineer) who has recently implemented a hall sensor
for overcurrent shutdown for  his
home built 1KW short wave FET PA successfully.
I will ask him if he is willing to disclose his design and send it to you if
he agrees.

73
Clemens
DL4RAJ

>-----Original Message-----
>From: owner-rsgb_lf_group@blacksheep.org
>[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Warren Ziegler
>Sent: Monday, April 08, 2013 9:07 PM
>To: rsgb_lf_group
>Subject: Re: LF: Re: Hall Effect for Over-current shutdown?
>
>Hi Alan,
>
>    I've modified the G0MRF amp with the M0BMU output
>configuration, I'm using a 30V supply.
>The G0MRF uses a current sense resistor to shut down the amp
>quickly in case too much current is being draw.
>I've modified the output transformer turns ratio to produce
>more power at lower supply voltages (I'm using 500V, 55a FETs).
>However with the new higher currents and with a new
>appropriate value sense resistor its developing a LOT of heat
>(12 W or so) and needs to be heat-sinked.
>I'm thinking Hall-effect might be more efficient and produce
>less heat - I'm pretty sure that others have used Hall effect
>devices to protect MOSFET amplifier and I'm looking for circuit tips.
>
>73 & Tnx!
>Warren
>
>
>
>
>On Mon, Apr 8, 2013 at 2:52 PM, Alan Melia
><alan.melia@btinternet.com> wrote:
>
>
>
>       Ah interesting problem Warren.... why is it
>over-current?? if it is over-current because a high voltage
>has welded/melted a short between drain and source, then the
>protection wont help ....high currents usually lead to excess
>heating ......but what is the real cause? If you really need
>DC supply protection would not a high-side current monitor be
>easier/faster??? The problem then could be there is enough
>energy stored in the PA choke to zap the FET before, or even
>if, you can disconnect the supply.
>
>       OK drive fails permanently on might be a condition it
>would protect the FETs against with DC coupled drive
>
>       Alan G3NYK
>
>               ----- Original Message -----

>               From: Warren Ziegler <mailto:wd2xgj@gmail.com>
>               To: rsgb_lf_group
><mailto:rsgb_lf_group@blacksheep.org>
>               Sent: Monday, April 08, 2013 7:15 PM
>               Subject: LF: Hall Effect for Over-current shutdown?
>
>               Anyone using a Hall effect device for
>overcurrent sensing and shutdown in a MOSFET amplifer?
>
>
>               --
>               73 Warren K2ORS
>                               WD2XGJ
>                               WD2XSH/23
>                               WE2XEB/2
>                               WE2XGR/1
>
>
>
>
>
>
>--
>73 Warren K2ORS
>                WD2XGJ
>                WD2XSH/23
>                WE2XEB/2
>                WE2XGR/1
>
>

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--
73 Warren K2ORS
                WD2XGJ
                WD2XSH/23
                WE2XEB/2
                WE2XGR/1