What is the role of DZ1, R11, Q7, DZ2 and R14 in this circuit?
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1\$\begingroup\$ It might help if you said what that circuit is used for. It looks like filament supply and biasing for vacuum fluorescent display. \$\endgroup\$– JustmeCommented Apr 13, 2022 at 22:05
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\$\begingroup\$ What's the voltage level of "-HV"? \$\endgroup\$– td127Commented Apr 13, 2022 at 22:28
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\$\begingroup\$ Why do you have concerns? \$\endgroup\$– D.A.S.Commented Apr 13, 2022 at 23:57
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1 Answer
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It looks to me like it's an extra measure to prevent positive current leaking in from the rectifier diodes. If the Zener diode ever receives a positive charge, it passes through to the transistor base, and the transistor drains the excess positive charge built up in the rectifier to ground.
I'm not too sure as to the function of C5, but my best guess is that it's a buffer for when the positive charge is drained so that there isn't a dip or spike in your output voltage.
