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Science Forum Index » Electronics - Basics Forum » Impedance Matching Help!
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Message |
| p.i@ntlworld.com |
 Posted: Mon Feb 05, 2007 8:07 am |
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Guest
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Hello,
I am fairly new to electronics and need some advice regarding
impedance matching.
I wish to impendance match a half bridge to a parallel tuned circuit
(LC) Via series inductor ie LCLR netwowk.
Here is a link to what I am trying to achieve.
http://www.richieburnett.co.uk/indheat.html
Questions :-
How does one find the impendance of the Half-Bridge?
How do I calculate the L-match inductance / capacitance required
to match the inverter (h-bridge) to the load?
Regards
SRG |
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| Joel Kolstad |
| Posted: Mon Feb 05, 2007 1:26 pm |
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Guest
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<p.i@ntlworld.com> wrote in message
news:1170677227.716196.56870@v33g2000cwv.googlegroups.com...
It's more or less equal to the on resistance of the FETs... plus some
inductance thrown in for good measure. BUT: He's not trying to match the
impedance of the half-bridge to that of his coil; he's considering the
half-bridge to be (approximately) an ideal voltage source, and therefore
trying to drop the impedance of the coil so that he can get decent amounts of
power into it while using reasonable voltages (hundreds of volts rather than
thousands of volts).
Quote: How do I calculate the L-match inductance / capacitance required
to match the inverter (h-bridge) to the load?
You have to know what his "work resistance," R, is. I suspect he determined
this empirically -- it's going to be a little different depending on exactly
what you insert. I'd imagine he first ran the circuit without the matching
network and simply measured the power consumption at resonance to ascertain R
(he probably chose the total capacitance -- some of which eventually becomes
part of the matching network -- to resonate his coil at, say... 150kHz). He
probably then did a few "back of the envelope" calculations to see whether or
not building a matching network to 10 ohms was reasonable and discovered that,
yes, it was. (The main point here is: A lot of his design appears to have
been done empirically.)
---Joel |
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