I'm trying to drive a Panasonic EFTU11R8MX50 piezoceramic transformer that has a rated input capacitance C(INPUT) = 61.6 nF. The output capacitance is C(OUT) = 11.4 pF. In series with the input side of the transformer is a series R of .66 ohms, a series L of .94 mH and a series C of 2.79 nf.
Instead of using the typical 50 percent duty cycle square wave switched input with series inductors to resonate with the parallel C input of the device (at 55 Khz), I want to drive it with a 55 Khz fixed frequency sine wave and vary the input amplitude in order to regulate the output.
The TI driver chip (UCC3977) talks about achieving a 'zero crossing switch' by choosing inductor sizes that don't achieve resonance at 55 Khz, the inductors are smaller than they should be to resonate at 55 Khz.
If I drive the unit with a 55 Khz sine wave, do I need to be concerned with this zero voltage switching problem or will the sine wave input minimize this problem? If I drive the input with a sine wave, should I use series inductors on the input to minimize higher frequency harmonics which destroy efficiency?
I'll post document that talks about this zero crossing switch problem is abse. The discussion about the zero voltage switching is at the top of page 22 in the first 2 paragraphs.
Mebart