Hi John,
You are correct. But a problem ,AD's true RMS chip is not a inexpensive
device.
I have an idea, using a inexpensive CdS photoresistor-LED or micro-bulb
photocoupler( like N110 in ICOM PS-35 power supply) because bulb and CdS
photoresistor with very bad frequency response
so the sampling voltage will associate with true RMS volt (I guesss) ...
If the noise is not a problem and the tube's cathode is oxide-coated ,
the switching regulator is the best. but monolithic IC maximal out put
current
only 10A (ST's L4970) others need external power MOS FET.
73!Hsu
----- Original Message -----
From: "John G3UUT" <amps@grebe.plus.com>
To: <amps@contesting.com>
Sent: Sunday, July 10, 2011 5:12 PM
Subject: Re: [Amps] AC filament voltage regulator
> I've also been thinking about this problem and the reason I'm not keen
> on a DC regulator is that the distortion and peak current of the mains
> current waveform is already pretty bad with a capacitor input B+ supply
> and making it worse by adding the heater as well will undoubtedly make
> the regulation of the B+ worse. This is particularly a problem when
> using portable generators.
>
> I've not taken this down to circuit level yet but my idea was to use one
> of the Analog Devices RMS to DC convertors as its important to maintain
> the RMS of the AC constant - especially when using poor quality mains
> from a generator. Hsu - this is the problem with your circuit. My
> other idea was to use a biphase rectifier with a centre taped
> transformer and schottky rectifiers to reduce the diode losses - which
> are quite significant with a 5 V heater.
>
> 73 John G3UUT
>
> On 10/07/2011 03:03, Dr. David Kirkby wrote:
>> On 07/10/11 01:12 AM, Hsu wrote:
>>> I do not think a DC regulator for direct heater tube is a good idea,I draw
>>> a block diagram for AC filament regulator
>>> here:http://www.zmdz.com/bbs/incomefiles/20117/1089098780.JPG, just a block
>>> diagram.any advice? I know we have another selection,CVT. a special
>>> transformet.
>>> 73!Hsu
>> What's wrong with a DC regulator?
>>
>
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