[AMPS] Voltage Doublers

2 2@vc.net
Thu, 17 May 2001 07:58:30 -0700

>Steve Thompson wrote:
>>>What does the voltage regulation look like, from 'zero' current (bleeder
>>>resistors only) to say 100mA ZSAC and then to 300mA peak?
>>With Glenn's new data, at 5mA load, 2300V, at 300mA, 2150V. Rs calculates at
>>29 ohms.
>>>What diode model did you use... and can you e-mail it please?
>>Here's the line I added to the 'rectifier.txt' file:
>>EHT, SS, 0.2, 20, 9.35, 6000, 200, 99
>>I'll leave anyone interested to collect their own version of the software
>>and decide if my model is duff.
>Not duff at all, Steve. I get the same values as you, so I was wrong
>about including the resistance contribution of the diode strings. 
>It seems that the diodes should be regarded as only a source of forward
>voltage drop, which is too small to matter in a HV supply.
€  valid point

>A good fit to the design charts seems to be simply Rs = R_secondary +
>N^2*R_primary (where N is the step-up turns ratio). For Glenn's
>transformer, Rs comes out as 29-30 ohms, same as Steve found, and using
>that value the chart agrees with the SPICE model. 
>So it looks like you're in business with that transformer after all,
>Glenn. Sorry if my pessimistic analysis gave you a bad 24 hours!
>Even so, that doesn't change the fact that FWD is *much* more sensitive
>to Rs than FWB is.
€  However, transformers for FWB duty need:  twice as many secondary 
turns, more insulating paper, and smaller diameter copper wire in the 
secondary.  The bottom-line  is that FWB transformers have much more R 
than same-physical-size FWD transformers.  More copper and less paper is 
why most of the ham market SSB amplifiers use a FWD.  For FM, AM, RTTY 
and AŘ, nothing beats a FWB with resonant-choke filtering.  

cheers, Ian

-  R. L. Measures, 805.386.3734, www.vcnet.com/measures.  

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