Automatic frequency tracking circuit for power supply of ultrasonic cleaning machine and frequency tracking method of automatic frequency tracking circuit

The invention discloses an automatic frequency tracking circuit for a power supply of an ultrasonic cleaning machine. The automatic frequency tracking circuit comprises an output control module and an input sampling module, wherein the output control module comprises an EMI circuit, a rectification circuit, a full-bridge phase shift circuit, a matching circuit and a DSP main control chip, and the input sampling module comprises a sampling circuit, a phase detection circuit, a current effective value calculation circuit and a DSP main control chip. A frequency tracking method of the automatic frequency tracking circuit for the power supply of the ultrasonic cleaning machine comprises the following steps that S1, outputting the ultrasonic power supply at a certain step pitch from minimum frequency to maximum frequency in sequence to form a response curve; and S2, when a difference value delta Imax of a current peak value of a current period is smaller than the difference value delta Imax of a previous period, a