Re: Need input on high voltage regulator design

From: Frank Bemelman (f.bemelmanx_at_xs4all.invalid.nl)
Date: 11/28/04 

Date: Mon, 29 Nov 2004 00:43:46 +0100

"Scott Miller" <scott@3xf.com> schreef in bericht
news:10qkdhad5k7rmd7@corp.supernews.com...
> I got bored yesterday and started working again on a Geiger counter design
I
> came up with a couple of years ago. The high voltage power supply was
> mostly cribbed from a couple of other designs I found, since I'm a digital
> guy and high voltage isn't my thing. As it stands now, the
microcontroller
> puts out a square wave that drives the primary of a transformer via a
> MOSFET. A voltage doubler on the secondary gets the voltage into the
> required range (500+ volts in this case), and a couple of varistors in
> series form a shunt regulator.
>
> It's the shunt regulator I'm looking to replace right now. Since the
input
> to the inverter is provided by the MCU's timer channel, it can be easily
> pulse-width modulated. I just need to get some feedback from the HV side
so
> the MCU knows how to adjust the duty cycle. My first thought was to use a
> pair of resistors to form a voltage divider and feed maybe 1/120 of the
> output voltage into the MCU's A/D converter. But with any reasonable
> resistor values, there's too much load on the supply to maintain the
needed
> voltage. Higher values might work, but the thick film resistors are
> expensive and I'm not sure how much current the ADC needs to function
> correctly.
>
> Any suggestions? I'm thinking an op amp might help, with its high input
> impedance. That still means using expensive thick film resistors, though.
> And again, I'm a digital guy and I'm a bit out of my element here.
>
> I'm really trying to keep the cost and component count down to make it an
> easy hobby project, but I'd also like it to not suck a battery dry in 2
> hours. If anyone's got any suggestions on how to implement a better
> regulator, or maybe a different supply design entirely, let me know.
>
> Current schematic is at: http://n1vg.net/geiger/images/gc1-9v.png. The
HV
> supply is on the right-hand side - everything from MCU pin 13 to the
> Geiger-Mueller tube. The pin header at left is for an LCD display.

Could you replace the D10 diode with a transistor, emitter to ground?
Then you get a digital signal that tells if the voltage is above
or below 500V, which you can use to increase/decrease the pwm.

I assume you are trying to keep current consumption to a minimum,
running everything from a 9V battery? 

-- 
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)

Relevant Pages

  • Re: battery charger topology
    ... substantial powers used to charge a 300Ah 24V lead acid battery bank ... normally have to build into the design. ... sets the voltage you must boost to. ... 100KHz may be a bit fast for the power level. ...
    (sci.electronics.design)
  • Re: Need input on high voltage regulator design
    ... > I got bored yesterday and started working again on a Geiger counter design I ... > guy and high voltage isn't my thing. ... That still means using expensive thick film resistors, ...
    (sci.electronics.design)
  • Re: PWM a truck alternator
    ... holding the system voltage at a measly 14.2 volts. ... 15V might damage your battery. ... if you feel overly generous you could volunteer to design one for ... the crankshaft, no belt costs, meaning no belt to break. ...
    (sci.electronics.design)
  • Re: Simple Linear Supply (for teaching my son)
    ... although it could benefit from more modern design. ... zener for voltage stabilization. ... poor load regulation without direct feedback (you have indirect feedback ... voltage sense, and then you have a stable and useful supply. ...
    (sci.electronics.basics)
  • Re: Power Inverters
    ... The "designer" copied the circuit ... When using a square wave or modified sinewave ... Newer power supplies have built-in power factor correction to make ... the slightly higher voltage won't matter. ...
    (comp.sys.laptops)