Re: [TCML] Calculating SSTC Secondary Output Voltage

["Udo Lenz" <udo_lenz@xxxxxxxxxxxxxx>]

Andreas wrote:

> Interesting. I just came across Don K's SSTC theory page
> (http://donklipstein.com/sst.html) and he implies that due to resonant
> effects an SSTC could get much higher than the Vpri * k * sqrt(Lsec/Lpri)
> [correct version of the earlier formula] that I've seen attached to SGTCs.
> Is this incorrect, or do you mean that other designs (like DRSSTCs) get
> even higher voltages?

For SGTCs you need to leave out the k, i.e. the voltage would be

Vpri *  sqrt(Lsec/Lpri)

For an _unloaded_ SSTC the equation would be

Vpri * k * sqrt(Lsec/Lpri) / (1 - (1 - k^2) * f^2 / fres^2)

where f is the input frequency and fres the secondary resonant frequency.
For a certain f the denominator will go to zero, so in principle the
voltage can be arbitrarily high. In practice sparks will break out, so
that the secondary is not unloaded anymore. So this equation holds only
for rather low secondary voltages.

In the case that f is such that the denominator of the above equation is
zero, i.e. the coil is perfectly tuned and there is a secondary load R,
the voltage is:

Vpri * k * sqrt(Lsec/Lpri) * R / ( (1-k^2) * 2 * pi * f * Lsec )

Since the voltage is proportional to R, the coil acts like a constant
current source to the secondary. Note also, that

R / ( (1-k^2) * 2 * pi * f * Lsec )

is approximately the secondary Q, so that the equation can be shortened to

Vpri * k * sqrt(Lsec/Lpri) * Q

Disclaimer: I didn't find any reference to these equations, so they might be
wrong ,-)

Udo


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