[ARC5] Power Supply Filter Question

Sat Dec 21 20:37:24 EST 2013

A Beta-C filter is relative simple and more than adequate. With a couple
of protective diodes, it's just about bulletproof. The version with a
Zener will easily add sufficient regulation.

-John

==============

> Bruce,
>
> I can agree with that statement.  The circuits are reproducible and
> components affordable, but the gotcha's should a tube-trained person try
> to
> roll his own design are just too numerous.  The high power FETs do have
> better SOA, but robustness issues remain.
>
> Dennis AE6C
>
>
> On Sat, Dec 21, 2013 at 11:02 AM, Bruce Long
> <coolbrucelong at yahoo.com>wrote:
>
>> You are correct Dennis to a large extent, however i think it is fair to
>> recast your comments as:  "Active, robust HV power supply regulation is
>> well within the capabilities of the amateur community but its adoption
>> has
>> been extremely limited because there is essentially no documentation or
>> traditional use within the amateur literature".  Notice this
>> conversation
>> on receiver HV power supply design started up with a reference to the
>> information on this subject in the ARRL handbook, information that has
>> been
>> mature for about 80 years.  You can buy 200 Watt power fets for no more
>> and
>> sometimes even significantly less then the cost of a new 20 Watt
>> resistor.
>> In my day job I have had to make test loads in the range of a few
>> hundred
>> to a few thousand Watts and unless i use water heating elements mounted
>> in
>> a 55 gallon drum of water it is easier and much-much cheaper to use a
>> gaggle of power fets each with a simple op-amp control loop to mimic the
>> effect of a fixed value power resistor.
>>
>> I have a voltage regulated, over current and transient protected power
>> design for a ARC-5 receiver sitting in my freeware schematic capture
>> software for almost two years now. I even have parts sitting on my
>> shelf.
>> The idea was to breadboad the design, document the performance and
>> publish
>> an article in the amateur literature.  Problem is I am a co-founder of a
>> technology start up business that is approaching viability and i have
>> two
>> young kids who want to do things with daddy.
>>
>> To be clear i have absolutely no problem with people building
>> traditional
>> style power supplies for traditional equipment but filter chokes are
>> somewhat hard to get, somewhat expensive, and certainly big and heavy.
>> It
>> is not unreasonable to consider another design approach making use of
>> modern, mass produced and therefore inexpensive power electronics
>> devices.
>>
>> Yes i agree the choke and HV transformer availability situation has
>> improved somewhat recently and i am grateful for that but i think the
>> point
>> still remains.
>>
>>
>>
>>
>>   On Friday, December 20, 2013 10:48 PM, Dennis Monticelli <
>> dennis.monticelli at gmail.com> wrote:
>>  I use power transistors to filter and regulate the HV for my ARC-5
>> transmitter, but it is not as easy as using L's and C's because the HV
>> transistors need fast-acting protection circuitry.  The Safe Operating
>> Curves for power transistors leave a lot to be desired.  The breakdown
>> voltage may be there but you will find that they cannot simultaneously
>> conduct even a small fraction of their rated current when fed from near
>> their max voltage.  I do not recommend it for someone that doesn't have
>> experience with semiconductor power electronics.
>>
>> Dennis AE6C
>>
>>
>> On Fri, Dec 20, 2013 at 7:05 PM, Bruce Long
>> <coolbrucelong at yahoo.com>wrote:
>>
>> It might offend the traditionalists but in my opinion power
>> semiconductors
>> are so cheap that active - as opposed to passive LC filtering- needs to
>> be
>> seriously considered.  Bruce   KJ3Z
>>
>>
>>
>>
>>
>> On Friday, December 20, 2013 9:35 PM, K5MYJ <macklinbob at gmail.com>
>> wrote:
>>
>> If there are two capacitors and an inductor in the supply you could try
>> leaving out the input capacitor. The output of an inductor input filter
>> is
>> lower than that of a capacitor input filter.
>>
>> Bob Macklin
>> K5MYJ
>> Seattle, Wa.
>> "Real Radios Glow In The Dark"
>> ----- Original Message -----
>> From: "Robert Eleazer" <releazer at earthlink.net>
>> To: <arc5 at mailman.qth.net>
>> Sent: Friday, December 20, 2013 6:04 PM
>> Subject: [ARC5] Power Supply Filter Question
>>
>>
>> > Back when I first started learning about boatanchors I read the usual
>> ARRL
>> > material that described the classic way to build a power supply: a
>> > capacitor, an choke inductor, and a capacitor.  I soon found out how
>> rare
>> > and expensive the required inductors were.
>> >
>> > I was amused last year when I rebuilt the AC power supply on a
>> BC-348-N.
>> > It was classic - literally right out of the Surplus Conversion Manual
>> -
>> > using two fairly low valued high voltage caps and a pretty big
>> inductor.
>> > I used some new, bigger, caps when I rebuilt it but left the inductor
>> in
>> > place.  Of course, it was also running the B+ way too high and I added
>> > some power resistors in both the AC input line and the B+ line.  Got
>> the
>> > B+ from over 250VDC down to about 200 VDC.
>> >
>> > Now, we have available high voltage caps that have much larger values
>> that
>> > those 20 mfd cans we used to use and are a lot smaller as well.  But I
>> > wonder if adding some inductance to the power supply circuit would do
>> some
>> > good?  Would winding some wire around a piece of steel or even around
>> a
>> > nail provide better filtering than just some big caps?
>> >
>> > Thanks,
>> >
>> > Wayne
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