[Amps] AC filament voltage regulator

[Hsu]

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 at grebe.plus.com>
To: <amps at 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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