Re: Voltage controlled 10V->100V DC-DC converter

On 26 May 2005 12:33:59 -0700, jwodin@xxxxxxxxx wrote:

>Output current is going to be in the low mA range, though I don't have
>an exact number (the load is almost entirely capacitive, with a very
>high R in parallel). I was hoping that the physical size would be
>something like 1"x1" on a PC board, if possible. And as far as
>efficiency, I assume you mean
>
>Power out / Power in ?
>
>If so, I can deal with very low efficiency. I'd have no problem having
>a standard rack HP power supply, or a few of them, powering the whole
>thing. As far as a control input voltage, I'll be controlling these
>DC-DC convters via CPU (with a National Instruments analog I/O board)
>that can supply -10V-10V analog (I can do digital too, but sounds more
>complicated).


I don't know much about switching supplies, but how about something
like this:


+12V>--+-----------------------------------+
| | Vc Vout
[L1] | 0-10 0-100
| | | /
+---[CR1>]--------------------------|---|---+--->>---+
| | | | |
| | | | |
C A---+ /+|--+ [R3] |
Q1 B--[R1]-+-Y NAND | A-------< | | +---+
E | B---+-+-Y NAND \-|------+ | |
| | | B---+ | | [C] [R]
| | | | | | | |
| | +--[R2]--+ | [R4] +---+
| | | | | |
| +--------[C1]-------+ | | |
| | | |
GND>---+-----------------------------------+-------+--->>---+

Basically a boost converter where the two NANDs form a gated
oscillator which turns Q1 on and off, forcing current through L1 and
then shutting it off abruptly which makes a spike that gets integrated
by C (your capacitor). As the stream of spikes charges C, the voltage
at the junction of R3 and R4 (a 10:1 voltage divider) rises until it
equals the voltage on the comparator's + input, at which time the
output of the comparator goes low, stopping the oscillator and turning
Q1 off. Then, when R (your load resistance) discharges C to the point
where the voltage on the - input of the comparator goes lower than the
voltage on the + input, the comparator's output will go high again,
starting the oscillator and recharging C.

--
John Fields
Professional Circuit Designer
.

Relevant Pages

  • Re: Charging a capacitor to 6kV
    ... How fast do you want to charge the capacitor? ... Expect to take on the order of a second to charge the ... "Blocking" oscillator is another term for flyback. ... for a high flyback voltage, even lower turns ratio would be good: ...
    (sci.electronics.design)
  • Re: "High" Voltage regulation
    ... regulation I have come up with a simple dual capacitor mode. ... voltage while the other is discharging into the load. ...
    (sci.electronics.design)
  • Re: "High" Voltage regulation
    ... regulation I have come up with a simple dual capacitor mode. ... voltage while the other is discharging into the load. ...
    (sci.electronics.design)
  • Re: Sourcing energy storage capacitors in the UK
    ... >> Not needed for the primary load. ... The salient behavior of a capacitor is that the voltage is ... and the motor will see wildly varying power ...
    (sci.electronics.design)
  • Re: "High" Voltage regulation
    ... also a voltage dividing effect. ... resistors the load will generally see a higher voltage than you might ... to quickly stop charging the capacitor as it will end up charging up ... Sort of a delta-sigma regulator. ...
    (sci.electronics.design)