Take in account that the system has a behavior similar to a cascode
switching circuit, SMPS with cascode switch use a high voltage bipolar
transistor in high side and a low voltage mosfet switch in low side so
the emitter of bipolar is connected to drain of power mos. In similar
manner if you open the cathode of the oscillator triode it stop to
oscillate and you don't need a high voltage thyristor, in any case if
you use pure AC or split doubled P/S thyristor naturally go in off state
at zero crossing, in case of pure AC the triode block the reverse
voltage at thyristor terminals.
Vladi
Il 25.01.2018 17:29 Steve White
ha scritto:
> I don't have much expertise with vacuum tubes. I am more
of a transistor person. My question concerns the 833A VTTC schematic of
Steve Ward. I have recently completed a VTTC based on this design and it
works well. My question involves the triac used for staccato operation.
The schematic specifies a triac with only a 480 volt rating. From the
schematic, it appears to me that this triac has to hold off about 4000
volts when switched off. Am I correct or am I missing something? Why is
a 480 volt triac adequate?
>
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