[EE] I want to put 1KV on a 200 uf capacitor

[AGSCalabrese]

Since I have 200V caps laying around from scrapped AT computer power
supplies , I thought of stacking 5 of them and balancing the voltage
with high value resistors and 200V zeners. Is there a better way ?

Best

Gus
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[Jinx]

> Since I have 200V caps laying around from scrapped AT computer
> power supplies , I thought of stacking 5 of them and balancing the
> voltage with high value resistors and 200V zeners. Is there a better
> way ?

My Big Boy's Book Of DC Supplies has a mains-driven 1100V
100mA circuit. There are 3 x 64uF 450V caps in series between
V+ and 0V with a 25k 10W bleeder resistor across each cap

[Spehro Pefhany]

At 10:19 PM 8/15/2009, you wrote:
>Since I have 200V caps laying around from scrapped AT computer power
>supplies , I thought of stacking 5 of them and balancing the voltage
>with high value resistors and 200V zeners. Is there a better way ?

You'd need 25 capacitors (5 in parallel = 1000uF/200V) and then 5 of
those sets in series to get 200uF/1kV. Resistors are the easiest way.
If you have 5 200V zeners in series you'll get a lot of current flow
if the voltage exceeds 1kV by a bit, whereas the caps have some ability
to handle surges.

Don't kill or maim (eg. blind) yourself, those voltages and energy storage
amounts (100J) should be taken very, very seriously as they are potentially
(so to speak) lethal.

>Best regards,

Spehro Pefhany --"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

[Ben Hencke]

Anyone have a schematic? I'm trying to visualize how that would
balance voltage without draining the caps at the same time. I've been
wanting to do something like this with cheap 2.5v super caps for
higher (not hundreds) voltage solar applications.

Cheers,
Ben

[AGSCalabrese]

Could one do it using a MOSFET per capacitor ?
MOSFET would be turned on if voltage rating of capacitor was exceeded.
R1 would be a high value such as 1 Mohm and the ratio of R1 and R2
would determine at what voltage the MOSFET Q1 began to turn on.
I guess Q1 could also be a BJT.

[William "Chops" Westfield]

>> I'm trying to visualize how that would balance voltage without
>> draining the caps at the same time. I've been wanting to do
>> something like this with cheap 2.5v super caps for higher (not
>> hundreds) voltage solar applications.

The supercap vendors tend to have app notes discussing this sort of
thing. For example:

http://www.cooperbussmann.com/pdf/35f489ea-89f2-4089-bbe3-9432cd21f9be.pdf

BillW

[M. Adam Davis]

The simpler design take this load into account - the charger simply
charges at a greater rate than teh discharge of the resistors.

They also tout it as a safety feature - the discharge rate is pretty
quick once the device is turned off.

More advanced solutions conserve that energy by only load balancing
when needed. It's not unlike choosing between a linear regulator and
a switching power supply - one is dead simple but has higher losses,
and the other is slightly more complex and expensive with fewer
losses.

-Adam