Okay, so I read all the advices and thank you all for explaining the
problems with this power supply. Since the board is extremely small and I
will be installing it in a very thin housing, I don't really have much
space to do modifications on it. So, I'll implement PS in my PCB design and
solder its components on it.
I'd like to know if you could check this PS and see if it should be ok for
my clock (4x IN-14 and 4x INS-1 tubes)?
Thanks a lot in advance.
<https://lh3.googleusercontent.com/-b9BU5T8kpY4/VgLxiEHdmZI/AAAAAAAAAFk/x7hJ0aVd_dA/s1600/mc34063_mk15cm1.gif>
Dana utorak, 22. rujna 2015. u 21:23:39 UTC+2, korisnik gregebert napisao
je:
>
> Why not just use a totem-pole pre-driver for the MOSFET ?
>
> BTW, this touches on a challenge when designing HV drivers, whether they
> are for DC-DC converters or driving cathodes. Most high-voltage NMOS
> devices (~400V) need 5-6 volts for solid gate turn-on, yet logic-levels on
> most micro-controllers and FPGAs are only 1.2 to 3.3volts. That leaves a
> few options:
>
> 1. Use high-voltage logic, such as 4000-series CMOS, to drive HV NMOS. My
> first nixie clock does this.
>
> 2. Use NPN drivers; you can easily design constant-current drivers running
> from 3.3V. I've used surface-mount devices with 2 NPNs inside, and they are
> rated at 250V.
>
> 3. Use a level-shifter between your logic and the driver. I'm doing this
> on my current design with a HV5530.
>
> 4. Find a device with a low-voltage gate. Good luck on this; most
> logic-levels NMOS devices only handle 60V or less. If you also want low Rds
> (necessary for DC-DC converters), you have even fewer options.
>
> 5. Pull-up resistor. Ugghhh... It will work, but you will burn more power.
> Could be dangerous for a DC-DC converter if the logic/software turning off
> the gate goes haywire, which would lead to large current/burnout.
>
>
> I advise against relying upon the voltage-drop of the nixie tube to
> protect the driver, though this is commonly done with designs using the
> 74141. I always select my driver to handle the maximum-possible anode
> supply, and add margin above that. I've never had a fried driver, ghosting,
> etc. Parasitic capacitance and leakage can stress drivers above their
> maximum ratings, which will lead to premature failure.
>
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