Re: 1KV buck converter

On 25/05/2025 5:16 am, john larkin wrote:

On Sun, 25 May 2025 04:21:16 +1000, Bill Sloman
<bill.sloman@ieee.org> wrote:
 

On 25/05/2025 3:35 am, john larkin wrote:

On Sat, 24 May 2025 12:23:52 -0400, legg <legg@nospam.magma.ca>
wrote:
 

On Fri, 23 May 2025 08:05:28 -0700, john larkin
<jl@glen--canyon.com> wrote:

<snip>

You are right. A diac isn't the best choice to make a 99% efficient converter.

99% would be a bit ambitious. Jim Williams got to about 92% with his
version of the Baxandall inverter, going the other way.
I've been thinking of a version on a RM14 core where I could fit 6000
turns of AWG38 wire. Centre-tapped, that would give me two 61.2H
primaries, and  245H for the tank circuit. If the parallel capacitance
of the windings can be held down to 25pF that's a resonant frequency of
2kHz, so the impedance at resonance is 3Mohm,and 1mA s the resonant current.
The resistance of windings is 474 ohm, so I^2.R is 500uW. 10uA at 1kV is
1OmW, so using 5% of that to keep the resonant tank ringing at a 3kV
would leave me with 95% efficiency.
It's strictly a back of the envelope calculation, and 25pF
is an ambitious target. You might need to bank the windings to get there - perhaps as flat pancakes wound one after the other with self-bonding wire, bonded by brief self-heating and stacked onto a cut-down coil former.
--
Bill Sloman, Sydney