Ultrasonic Cleaner Circuit Design: Frequency, Power and Control

The load is not a resistor

A piezoelectric transducer bonded to a tank behaves like a resonant circuit with a strong capacitive component. Its impedance changes sharply around resonance and shifts with temperature, liquid level and load. The generator must cope with all of this.

Choosing the operating frequency

Lower frequencies (for example around 25–28 kHz) produce larger cavitation bubbles and more aggressive cleaning. Higher frequencies (for example 40 kHz and above) produce smaller bubbles and gentler, more uniform action suited to delicate parts. The transducer is built for a specific frequency, and the electronics must match it.

Power stage topology

Half-bridge and full-bridge switching stages are common. A transformer steps up voltage and provides isolation, while a matching inductor compensates the transducer capacitance so that the stage sees a more resistive load near resonance.

• Device selection for voltage, current and switching losses
• Dead-time control to avoid shoot-through
• Snubbers and layout to control ringing

Frequency tracking and sweep

Control and user experience

Power level, timers, degas modes, heater control and fault indication are all firmware features. Designing them in from the start produces a coherent product rather than a power stage with controls bolted on.