# Resonant Power Supply for Plasma Cleaning Based on Fuzzy Logic Power Tracking
## 3 Resonant Power Supply Control Method for Plasma Cleaning
The module uses an integrator and flip comparator to convert the adjustable digital input signal into an adjustable triangular wave signal, and then compares the triangular wave with the duty cycle signal to generate a pulse waveform with an adjustable frequency. A delay device is used to generate a four-channel PWM waveform with a phase shift angle, which is used to drive the full-bridge circuit [20]. Figure 12: Internal structure of a PSPWM controller. Figure 13: Internal structure of a fuzzy PFM controller. Adjust the equivalent load of the system, set the resonance frequency of the system as 42.54 kHz, the initial operating frequency as 35 kHz, the initial phase shift angle as 45\({}^{\circ}\), the duty cycle as 0.4, and the output power as 1000 W to simulate the system. Figure 15 shows the output power, phase shift angle, and operating frequency. As can be seen from the figure, after 0.05 s, the output power of the system is stable at about 1000 W, the phase shift angle is stable at 53\({}^{\circ}\), and the working frequency is stable at about 40 kHz. It can be seen that the hybrid modulation algorithm has the advantages of a fast adjustment speed, a high-adjustment precision, and is operable. Set the initial operating frequency of the system as 40 kHz, the initial phase shift angle as 55\({}^{\circ}\), the duty cycle as 0.4, and the target output power as 1000 W. At 0.05 s, the parallel capacitor C\({}_{1}\) perturbation is introduced, and its capacitance value is 25 nF, that is, the equivalent load capacitance of the system increases from 35 nF to 60 nF at 0.05 s, and  
Figure 14: Internal structure of the driver wave generator. Figure 15: Simulation waveform of hybrid modulation algorithm. the anti-perturbation performance of the system is simulated. Figure 16 shows the output power, phase shift angle, and operating frequency. As seen in Figure 16, at 0.05 s the load capacitance spurts resulting in the system and the resonance frequency of the power of the output power falling sharply. The error of the algorithm to detect the output power is very big and tries to improve the power output by rapidly reducing the phase-shifting angle. When the phase-shifting angle adjustment to the lower limit of 20\({}^{\circ}\) still cannot meet the needs of power set, the maximum power tracking algorithm based on fuzzy PFM starts to work. During the period of 0.05 s to 0.25 s, the operating frequency of the system decreases, and the resonant frequency point is constantly approached, so that the output power increases. During the period from 0.25 s to 0.46 s, the working frequency continues to decrease and approach the resonant frequency, so as to maintain the maximum efficiency of the plasma power supply, but the output power should be stable at 1000 W and cannot continue to rise. At this time, PSPWM takes effect, making the working frequency track the resonant frequency point while the output power remains stable. Finally, after 0.46 s, the output power, phase shift angle, and operating frequency of the system stabilize at about 1000 W, 60\({}^{\circ}\), and 32 kHz, respectively. Under the same conditions, the C\({}_{2}\) perturbation of the series capacitor is introduced at 0.05 s with a capacity of 46 nF, that is, the equivalent load capacitance of the system drops from 35 nF to 19.88 nF at 0.05 s. The anti-perturbation performance of the system is simulated, and the simulation results are shown in Figure 17.  
As can be seen from Figure 17, at 0.05 s, the sudden change of load leads to a sharp decline in system output power, and the phase shift angle is rapidly adjusted to the lower limit of 20\({}^{\circ}\), but the actual output power is still too small. The maximum power tracking algorithm based on fuzzy PFM takes effect at this time.