xeratule
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I just scribbled down a quick and clear (obviously not, sorry) circuit to focus on. Hence you're right, I should have changed the IGBT position ... Anyway, I think my real problem is about impedance matching.... Btw I didn't understand what you meaned to chack away C1. Do you mean there should be no series capacitor to the primary winding of the transformer although assuming the circuit is corrected? I whink that series capacitor is necessary, as I see changing its value and that way loosing resonance at primary side leads to few power at output.... I have a well operationg full bridge driver circuit which is driven by 25khz pwm (25khz is the resonance frequency of the transducer). I built a simplified circuit to focus on my problem, please see the attached file ...
I'm sure, we looked carefully. Please don't foul us.If you look carefully, I actually have a push pull full bridge circuit.
Yes I updated the schematic to full bridge view ... Sorry for misunderstandings ... I was just a little lazy to draw full schematic and to be clear I draw a simple schematic. Please see the updated attachment in my first post. Circuit PWM is operating in complementary pwm mode so that Q1&Q4 operates at one half Q2&Q3 at second half ...I'm sure, we looked carefully. Please don't foul us.
I see, you are just up to replace your schematic. :lol:
Anyway, please don't stick into circuit DC path, driver circuit ... vs problems because the circuit actually operates good but not well enough to have maximum output power.The circuit doesn't work, because there's no DC path for the IGBT current. Also the IGBT driver details are questionable, and you most likely would want a means to protect the IGBT against overvoltages.
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Vcc = 220V, Transducer is capable of handling 300watts of output power. Yes, transducer may have adjacent parallel and series resonances but not have a real impedance at all. When I sweep the frequency between 24khz - 30khz it has a quite variable impedance though remaining between this range. And transducer's resonance frequency (minimum impedance frequency) changes with load and temprature. I thought if I design my circuit at resonance frequency where transducer impedance is least, I could get most power from it.Regarding impedance matching, I would ask at first for applicable voltage respectively power levels. What's the transducer specification? Usually, piezo transducers have an impedance characteristic similar to a crystal, showing adjacent parallel and series resonances. The impedance will be real at both of them, so you don't necessarily need a parallel inductor, although it's used in some applications.
Btw I didn't understand what you meaned to chack away C1. Do you mean there should be no series capacitor to the primary winding of the transformer although assuming the circuit is corrected? I whink that series capacitor is necessary, as I see changing its value and that way loosing resonance at primary side leads to few power at output.
All the resonance you need you can get from the leakage of the transformer and your load (you may need a cap in parallel on the sec side) having a series cap on the primary for a single ended drive (1 x transistor) simply will not work, hence chuck C1 away for that circuit as you need to let the collector volts rise to nearly 2 x the input volts to balance the volt-seconds applied to the transformer and get proper (resonant) operation.
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Would be the first transducer that hasn't a real impedance at resonance frequency. But you didn't show the impedance measurement. Normally, the impedance will be inductive at one side of a resonance and capacitive at the other, applies both to series and parallel resonance.Yes, transducer may have adjacent parallel and series resonances but not have a real impedance at all.
Transducer of course has real impedance,what I tried to explain was it's not purely resistive at all, sorry about my englishWould be the first transducer that hasn't a real impedance at resonance frequency. But you didn't show the impedance measurement. Normally, the impedance will be inductive at one side of a resonance and capacitive at the other, applies both to series and parallel resonance..
I tried many different transformers, different windings for both primary and secondary side. Actually I don't know how leakage inductance is used and controlled.Have you considered extra L on the sec side (or a xfmr with increased leakage) to help you obtain a nicer resonant operation?
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Wouldn't transformer secondary do the tuning or an effect on tuning? Why should I additionally use series inductor?The frequency that will give you the most real power transfer at a given drive voltage is the resonance that has the lowest real impedance. For piezo elements this resonance usually has a significant capacitive reactance that you want to tune out, usually with a series inductor on the secondary side of the transformer. Your series capacitor C1 is working against you for tuning. If you make C1 real big so that its reactance is negligable it may prevent damage in the case of drive failure. But it does not help tune the ducer.
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