Driving circuit for piezo

[luoxx416]

Hi everyone,

I'm trying to build a circuit for driving piezo element at high power. The circuit diagram is attached. The main components in the circuit are a gate driver(TC4422), a power MOSFET(IRL520) and a piezo which should resonant at 342kHz based on the spec sheet.

The input digital signal is 5V square wav, the Vcc = 5V and VDD = 15V for testing.

I measured the signals using an oscilloscope.
CH1(Orange):    Directly from the signal generator
CH2(Blue):   Output from gate driver
CH3(Purple):    VDS from MOSFET with/without piezo

F0052TEK is the one without the piezo element. The output from MOSFET looked nice.
When I connected piezo to the MOSFET, the signal became worse. I am trying to understand why it happened.

F0053TEK is the one with piezo element and the driving frequency is ~341 kHz.
F0054TEK is the one with piezo element and the driving frequency is ~342 kHz.

The output signal changed with the frequency. It looked better when driving frequency is closer to resonant frequency. My guess is the piezo has inductive and capacitive components when it’s not at resonance. That will cause the signals became less square wave like. Am I understanding this correctly?

Thanks for the help!

[SiliconWizard]

https://www.efunda.com/materials/piezo/electronics/elec_equiv_circuit.cfm