Radio frequency power supply arc rapid detection method and system

Abstract

The invention belongs to the technical field of radio frequency power supply detection, and discloses a radio frequency power supply arc rapid detection method and system, and the method comprises the steps: obtaining a voltage signal and a current signal after a coupler couples an output radio frequency signal; sampling the voltage signal and the current signal, performing digital signal processing, and calculating amplitude values of the voltage signal and the current signal; selecting a plurality of sampling points, and respectively calculating a voltage change rate and a current change rate; and the voltage change rate and the current change rate are compared with the threshold of the rated value to complete arc judgment. The FPGA is used as a main control chip, a sampling chip is a high-speed AD, the advantage of high real-time performance is achieved, whether the arc phenomenon occurs or not is judged by judging the change rate of the voltage and the current, and therefore the problem that threshold values of the voltage and the current are difficult to select can be avoided. The method has the advantages of short calculation delay, quick response and high judgment accuracy, and can obtain a judgment result in an extremely short time.

Description

Technical Field

[0001] The present invention belongs to the technical field of radio frequency power supply detection, and in particular, relates to a method and system for rapid detection of radio frequency power supply arcs. Background Art

[0002] Arcing is inevitable in RF power systems. Due to the accumulation of charges on the workpiece surface at the load end and the discharge at the tip of the surface, arcing can easily occur, causing irreversible damage to the workpiece surface. Rapid and efficient arc detection and early intervention are essential for the protection of workpieces. When an arc occurs, the current amplitude and voltage amplitude of the output signal will undergo an instantaneous mutation. There are usually two detection methods for arcing detection: 1. By comparing the output voltage amplitude and the output current amplitude in the current state with a certain threshold, when the voltage amplitude is lower than a certain threshold and the current amplitude is higher than a certain threshold, it is considered that an arc has occurred. 2. By detecting the change in the reflection coefficient, it is determined whether an arcing phenomenon has occurred. Generally, the deviation between the current value of the reflection coefficient and the average value of the recent short period of time is judged. If it exceeds a certain threshold, it is considered that an arcing phenomenon has occurred.

[0003] The arc is judged to be defective by the voltage amplitude being lower than a certain threshold and the current amplitude being higher than a certain threshold. 1) The thresholds are inconsistent under different output powers, and the thresholds need to change according to the output power. 2) The thresholds are inconsistent for different load impedances. Even if the output power is the same, the voltage and current corresponding to the high impedance load and the low impedance load are different when working normally, and the difference may be very large. Therefore, it is necessary to test the current load impedance and adjust the threshold according to different load impedance values. Therefore, the selection of the threshold is difficult and the operability is not strong. It is difficult to meet various actual working environments. If the threshold is set unreasonably, it will cause inaccurate arc detection, frequent omissions or false alarms.

[0004] The method of detecting whether an arc has occurred by changing the reflection coefficient also has certain defects.

[0005] The reflection coefficient cannot be directly coupled and sampled relative to the voltage and current values, and a certain conversion is required. This is difficult to process and may result in a large processing delay, making it difficult to respond in a timely manner.

[0006] During the process of fast matching and tuning of the matcher, the reflection coefficient will also change rapidly, and the faster the tuning speed, the faster the reflection coefficient changes. At this time, it is difficult to distinguish whether the change in reflection coefficient is caused by the arc or the matching tuning, unless the matching speed is limited. This is contrary to the need for faster matching speed. Summary of the invention

[0007] In view of this, the present invention provides a method and system for rapid detection of arc in a radio frequency power supply to solve the above-mentioned problem.

[0008] In order to solve the above technical problems, the present invention provides A method for quickly detecting arc in a radio frequency power supply, comprising: Obtaining a voltage signal and a current signal after the coupler couples the output radio frequency signal; Sampling the voltage signal and the current signal, and performing digital signal processing to calculate the amplitude values ​​of the voltage signal and the current signal; Construct a trend graph of the amplitude values ​​of the voltage signal and the current signal, select multiple sampling points on the trend graph along the time axis, and calculate the voltage change rate and the current change rate respectively; The voltage change rate is compared with the threshold of the rated voltage, and the current change rate is compared with the threshold of the rated current; if the voltage change rate is greater than the threshold of the rated voltage and the current change rate is greater than the value of the rated current, it is determined that an arc has occurred.

[0009] As an optional method, FPGA is used to control high-speed AD to sample the coupled voltage and current analog signals.

[0010] As an optional method, sampling point a, sampling point b, and sampling point c are selected on the amplitude value trend graph of the voltage signal and the current signal; The voltage change rate is: Vk = (Va-Vb) / Va + (Vb-Vc) / Vb; The rate of change of current is: Ik = (Ib-Ia) / Ib + (Ic-Ib) / Ic; Wherein, Va is the voltage amplitude value at sampling point a, Vb is the voltage amplitude value at sampling point b, and Vc is the voltage amplitude value at sampling point c; Ia is the current amplitude value at sampling point a, Ib is the current amplitude value at sampling point b, and Vc is the current amplitude value at sampling point c.

[0011] As an optional manner, sampling point a, sampling point b, and sampling point c are continuous sampling points.

[0012] As an option, the threshold value interval of the rated voltage and / or the rated current is between 0 and 1.

[0013] On the other hand, the present invention also provides a radio frequency power supply arc rapid detection system, which is used to execute the above radio frequency power supply arc rapid detection method, including: Coupler, FPGA control unit, high-speed AD chip; The coupler is used to couple the output RF signal to obtain two analog signals of voltage and current; The FPGA is current-connected to the high-speed AD chip for sampling the coupled voltage signal and current signal; the sampling rate of the high-speed AD chip is 100Msps.

[0014] The beneficial effects of the present invention are: The present invention determines whether an arc phenomenon occurs by judging the rate of change of voltage and current, thereby avoiding the problem that the voltage and current thresholds are difficult to select. Compared with the reflection coefficient judgment method, the voltage and current values ​​can be easily directly coupled and sampled, and the rate of change can be obtained by simple calculation, and the calculation delay is also very short, which can respond quickly. The judgment accuracy is high, and the judgment result can be obtained in a very short time, and the response speed is fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of current and voltage amplitude waveforms when the impedance value changes slowly provided by an embodiment of the present invention; Figure 2 A schematic diagram of current and voltage amplitude waveforms when an arc occurs provided by an embodiment of the present invention; Figure 3 A schematic diagram of a detection process provided by an embodiment of the present invention; Figure 4 A schematic diagram of rapid arc detection provided by an embodiment of the present invention; Figure 5 A sampling example diagram provided for an embodiment of the present invention; Figure 6 A schematic diagram of the waveform of the current and voltage amplitude of the RF output when an arc is detected and the RF output is shut down instantly according to an embodiment of the present invention. DETAILED DESCRIPTION

[0016] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with specific implementation methods.

[0017] See also Figure 1 and Figure 2 , Figure 1 It is the changing trend of current and voltage amplitude when impedance changes. The starting point is at the upper end for current, and the starting point is at the lower end for voltage. Figure 2 The current and voltage change trends when an arc occurs. The starting point is at the upper end for current, and the starting point is at the lower end for voltage. When an arc occurs, the current and voltage change suddenly, while when the impedance changes, the current and voltage change slowly. The arc is judged by the voltage amplitude being lower than a certain threshold and the current amplitude being higher than a certain threshold. Figure 1 Misjudgment occurs in the case of.

[0018] To solve the above problems, see Figure 3 and Figure 4 This embodiment provides a method for quickly detecting an arc in a radio frequency power supply, comprising: Obtaining a voltage signal and a current signal after the coupler couples the output radio frequency signal; Sampling the voltage signal and the current signal, and performing digital signal processing to calculate the amplitude values ​​of the voltage signal and the current signal; Construct a trend graph of the amplitude values ​​of the voltage signal and the current signal, select multiple sampling points on the trend graph along the time axis, and calculate the voltage change rate and the current change rate respectively; The voltage change rate is compared with the threshold of the rated voltage, and the current change rate is compared with the threshold of the rated current; if the voltage change rate is greater than the threshold of the rated voltage and the current change rate is greater than the value of the rated current, it is determined that an arc has occurred.

[0019] In this embodiment, FPGA is used as the main control chip, and high-speed AD is used to sample the voltage and current of the RF signal coupled from the VI sensor. The sampling rate can reach 100Msps, which can accurately capture the amplitude changes of current and voltage when the arc is generated. And by taking advantage of the FPGA digital signal processing, a series of digital signal processing operations are performed on the quantized voltage signal and current signal to quickly calculate the amplitude values ​​of the voltage signal and current signal.

[0020] See also Figure 5 When an arc is generated, the voltage amplitude will instantly decrease, and the current amplitude will instantly increase. In order to obtain the complete current amplitude and voltage amplitude change rate when an arc is generated, this embodiment takes three consecutive voltage amplitudes and current amplitudes to calculate the change rate.

[0021] The three calculated continuous voltage amplitude values ​​are taken as Va, Vb, and Vc. The voltage change rate is calculated as follows: Vk = (Va-Vb) / Va + (Vb-Vc) / Vb; Take the calculated three consecutive current amplitude values ​​as Ia, Ib, and Ic. Then the current change rate is calculated as Ik = (Ib-Ia) / Ib + (Ic-Ib) / Ic. Compare Vk with the rated voltage threshold and Ik with the rated current threshold. If Vk is greater than Vth (rated voltage threshold) and Ik is greater than Ith (rated current threshold), it is considered that an arc phenomenon has occurred (the threshold interval value of the rated voltage and / or rated current is 0 to 1). If Vk is greater than Vth and Ik is greater than Ith, it is considered that an arc phenomenon has occurred.

[0022] See also Figure 6 In the figure, the starting point at the top is the current, and the starting point at the bottom is the voltage. The vertical change represents the amplitude, and the horizontal change represents the time (unit: microsecond). Figure 1 , Figure 2Based on the method proposed in this embodiment, in some implementation scenarios, when an arc is detected, the RF output is immediately turned off through the FPGA. At this time, the voltage and current amplitude values ​​after the RF output is turned off are 0, which can prevent the workpiece from being damaged, such as Figure 6 As shown in the figure, due to the high sampling rate and the use of FPGA as the main control chip, the arc response speed can reach the ns level.

[0023] Through the above scheme, the present invention uses FPGA as the main control chip and high-speed AD as the sampling chip, which has the advantage of high real-time performance. By judging the rate of change of voltage and current, it is judged whether arc phenomenon occurs, thereby avoiding the problem that the threshold values ​​of voltage and current are difficult to select. Compared with the reflection coefficient judgment method, the voltage and current values ​​can be easily directly coupled and sampled, and the rate of change can be obtained by simple calculation. The calculation delay is also very short and can respond quickly. The judgment accuracy is high, and the judgment result can be obtained in a very short time, and the response speed is fast. The arc phenomenon can be detected at the ns level, the output is cut off, the workpiece is protected, and no misjudgment will occur in a load environment with impedance changes.

[0024] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for rapid detection of arc in a radio frequency power supply, characterized in that: include: Obtaining a voltage signal and a current signal after the coupler couples the output radio frequency signal; Sampling the voltage signal and the current signal, performing digital signal processing, and calculating the amplitude values ​​of the voltage signal and the current signal; Constructing a trend graph of the amplitude values ​​of the voltage signal and the current signal, selecting a plurality of sampling points on the trend graph in sequence along the time axis, and calculating the voltage change rate and the current change rate respectively; The voltage change rate is compared with the threshold of the rated voltage, and the current change rate is compared with the threshold of the rated current; if the voltage change rate is greater than the threshold of the rated voltage and the current change rate is greater than the value of the rated current, it is determined that an arc has occurred.

2. A method for rapid detection of arc in a radio frequency power supply according to claim 1, characterized in that: FPGA is used to control high-speed AD to sample the coupled voltage and current analog signals.

3. The method for rapid detection of arc in a radio frequency power supply according to claim 1, characterized in that: Selecting sampling point a, sampling point b, and sampling point c on the amplitude value trend graph of the voltage signal and the current signal; The voltage change rate is: Vk = (Va-Vb) / Va + (Vb-Vc) / Vb; The current change rate is: Ik = (Ib-Ia) / Ib + (Ic-Ib) / Ic; Wherein, Va is the voltage amplitude value at sampling point a, Vb is the voltage amplitude value at sampling point b, and Vc is the voltage amplitude value at sampling point c; Ia is the current amplitude value at sampling point a, Ib is the current amplitude value at sampling point b, and Vc is the current amplitude value at sampling point c.

4. The method for rapid detection of arc in a radio frequency power supply according to claim 1, characterized in that: Sampling point a, sampling point b, and sampling point c are continuous sampling points.

5. The method for rapid detection of arc in a radio frequency power supply according to claim 1, characterized in that: The threshold value interval of the rated voltage and / or rated current is between 0 and 1.

6. A radio frequency power supply arc rapid detection system, used to execute the radio frequency power supply arc rapid detection method as described in any one of claims 1 to 5, characterized in that: include: Coupler, FPGA control unit, high-speed AD chip; The coupler is used to couple the output radio frequency signal to obtain two analog signals of voltage and current; The FPGA is current-connected to the high-speed AD chip for sampling the coupled voltage signal and current signal; the sampling rate of the high-speed AD chip is 100Msps.

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