[AMPS] Voltage Doublers
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
>>>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.
- R. L. Measures, 805.386.3734, www.vcnet.com/measures.
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