A microwave plasma lighting system and automatic control method thereof

Abstract

The present invention discloses a microwave plasma lighting system and an automatic control method thereof. The system includes a radio frequency energy control area responsible for power output and a plasma light source that absorbs radio frequency power to maintain luminescence. The radio frequency energy control area includes: an integrated phase-locked control radio frequency chip, a switching circuit, a power amplifier, a PID current stabilization circuit, a voltage-controlled attenuator, and a detection circuit. The present invention utilizes a PID controller to stabilize the circuit current, and achieves successful startup of the plasma lamp by successively tracking the luminous state of the plasma light source and the continuous changes of various parameters. This method solves the problem that the plasma state is difficult to judge due to the interaction of multiple parameters faced by existing control means during the startup process. The system has high reliability and is easier to implement. Secondly, the present invention can maintain the stability of the light intensity during the final operation of the lighting system, while having a dimming effect, and introduces pulse radio frequency modulation to further improve the light efficiency.

Description

Technical Field

[0001] The invention relates to the field of microwave plasma lighting system control methods, in particular to a microwave plasma lighting system and an automatic control method thereof. Background Art

[0002] Plasma light sources use microwave radio frequency energy to excite gas discharge and emit bright white light. There are no metal electrodes in the arc tube of plasma lamps, which increases the lifespan and allows the bulb material to work at high temperatures, which is more conducive to the broadening of the discharge spectrum of the luminescent elements, emitting a continuous full spectrum from ultraviolet to infrared, similar to sunlight, with the advantages of full spectrum, high brightness and long life. It can be used in large stadiums, ultraviolet water treatment, agriculture, performing arts lighting, instrument lighting and other fields, and has broad prospects.

[0003] Early plasma light sources used magnetrons to generate radio frequency energy to drive the light emission. The short life of magnetrons limited the development of plasma light sources. In recent years, semiconductor solid-state microwave sources have developed rapidly to drive plasma light emission. LDMOS or GaN devices are used as microwave amplifiers to generate a concentrated electric field through a resonant cavity to break down the gas in the bulb. As the temperature rises, the metal halide in the bulb is ionized to form an arc discharge, generating high-brightness plasma light radiation. However, although the use of solid-state microwave sources has increased the life of plasma light sources, there are still many limiting factors in plasma lamps. Especially when the plasma lamp is started, a large standing wave is generated between the solid-state microwave source and the resonator, and the radio frequency power is difficult to couple into the bulb. On the one hand, it cannot absorb enough energy to convert to a bright arc state, and on the other hand, the high-power reflection on the line can easily damage the solid-state power amplifier tube.

[0004] There are some methods to automatically control the start-up of plasma light sources, such as adjusting the frequency of the voltage-controlled oscillator (VCO) and judging the state of the lamp by the reflected power. However, during the startup of the lamp, the standing wave is very large, the reflected power signal does not change significantly, and it is easy to be submerged in the interference generated by the high-power RF signal. Moreover, when the frequency changes, the current signal and the RF power also change at the same time, which will cause the failure of the automatic control to judge the working state of the lamp, resulting in serious consequences. For example, the RF power is continuously added when the lamp is not lit, causing damage to the power amplifier tube; or the startup time is too long and it cannot transition to arc discharge. In addition, the voltage-controlled oscillator (VCO) also produces a large frequency drift with the ambient temperature and time, causing instability when the plasma lamp is started, or it cannot be started.

[0005] Therefore, there is still a strong need to improve the automatic control method of the plasma light source. Summary of the invention

[0006] After analysis, it is believed that the defects of the existing automatic control means are mainly caused by excessive parameter changes when the lamp is started and some parameters are inaccurate. The purpose of the present invention is to provide a microwave plasma lighting system and an automatic control method thereof, which uses a microcontroller to follow the different states of the plasma light source under a certain working frequency and DC current consumption, and quickly makes the bulb absorb radio frequency energy and enter the arc discharge state, so as to solve the problems existing in the automatic control of the existing plasma light source during the startup process.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A microwave plasma lighting system comprises a radio frequency energy control area responsible for power output and a plasma light source area for absorbing radio frequency power to maintain light emission; characterized in that the radio frequency energy control area comprises:

[0009] An integrated phase-locked control radio frequency chip, internally integrating a microcontroller and a fractional frequency phase-locked loop, wherein the integrated phase-locked control radio frequency chip generates a radio frequency power signal;

[0010] A switch circuit connected to the first output terminal of the integrated phase-locked control radio frequency chip;

[0011] A power amplifier connected to the second output terminal of the integrated phase-locked control radio frequency chip and connected to the switch circuit;

[0012] A PID current stabilization circuit connected to the third output terminal of the integrated phase-locked control radio frequency chip;

[0013] A voltage controlled attenuator connected to the PID current stabilization circuit;

[0014] A detection circuit connected to the input end of the integrated phase-locked control radio frequency chip;

[0015] Among them, the microcontroller outputs a first PWM signal via the first output terminal, and the first PWM signal is input into the switching circuit; the microcontroller outputs a DAC1 signal after filtering and digital-to-analog conversion via the second output terminal, and the DAC1 signal is input into the power amplifier to switch the working state of the power amplifier tube of the power amplifier; the microcontroller outputs a DAC2 signal after filtering and digital-to-analog conversion via the third output terminal, and the DAC2 signal is input into the PID current stabilization circuit, and the DAC2 signal controls the voltage-controlled attenuator behind the integrated phase-locked control RF chip through the PID hardware current stabilization circuit; the above-mentioned first PWM signal controls the drain of the power amplifier tube through the switching circuit to realize pulse modulation of the RF signal.

[0016] Among them, the input end of the microcontroller uses the data acquisition of four analog-to-digital conversion channels as the plasma light source input control signal, wherein the first analog-to-digital conversion channel is an ADC1 signal for collecting the temperature driven by the RF power amplifier, the second analog-to-digital conversion channel is an ADC2 signal for collecting the circuit current measurement value, the third analog-to-digital conversion channel is an ADC3 signal for collecting the incident power measurement value of the plasma light source circuit, and the fourth analog-to-digital conversion channel is an ADC4 signal for collecting the reflected power measurement value.

[0017] Furthermore, the integrated phase-locked control radio frequency chip works in a single carrier state and uses fast frequency hopping technology to quickly change the operating frequency; the microcontroller is configured to change the operating frequency setting value by modifying the frequency divider of the fractional frequency phase-locked loop. The microcontroller and the phase-locked loop are integrated inside a chip, which reduces the cost of the system, and the frequency signal of the radio frequency signal generated by the phase-locked loop is determined. The traditional VCO, as the radio frequency source of the plasma light source, may produce a frequency drift of several megahertz within the operating temperature range. The fractional frequency phase-locked loop used in the present invention has a frequency drift within 1 Hz with changes in temperature and time, and there is almost no drift, which ensures the consistency of the plasma light source product and greatly reduces the subsequent testing and debugging workload.

[0018] Furthermore, the DAC2 signal controls the voltage-controlled attenuator behind the integrated phase-locked control RF chip through the PID hardware current stabilization circuit, so that the current of the entire drive circuit is constant, and the current size is set by the microcontroller through the DAC2 signal.

[0019] Furthermore, the first PWM signal controls the drain of the power amplifier tube through the switch circuit, and modulates the radio frequency signal output to the plasma light source into a pulsed radio frequency signal through the first PWM signal.

[0020] Furthermore, the DAC1 signal and the DAC2 signal are respectively generated by the second PWM signal and the third PWM signal generated by the microcontroller after filtering and digital-to-analog conversion, and are respectively used to adjust the static operating point of the power amplifier and the current setting value of the entire circuit.

[0021] Furthermore, the temperature sensor that generates the ADC1 signal and the channels related thereto can be integrated as a whole into a microcontroller inside the integrated phase-locked control radio frequency chip.

[0022] The DAC1 signal is used to switch the working state of the power amplifier tube. When the light source is started, the gate voltage is adjusted to make the power amplifier work in the AB class state. When the arc discharge is stable, the amplifier works in the C class state. According to the different working states, the RF amplifier can be divided into Class A, Class B, Class AB, Class C amplifiers, etc. The gain and efficiency of different types of amplifiers are different. In the early stage of the startup of the microwave plasma lighting system, the reflection coefficient is very high. The AB class state can take into account efficiency while ensuring high-power RF energy injection, ensuring that the bulb absorbs enough energy to transition to arc discharge. As the plasma state continues to change, the reflection coefficient continues to decrease until it is below the threshold level indicating that the startup is complete, and enters the stable operation stage. In this stage, the reflection coefficient is low, and the amplifier works in the C class state, which can improve the conversion efficiency of the RF power amplifier, thereby increasing the luminous efficiency of the microwave light source system.

[0023] The DAC2 signal controls the voltage-controlled attenuator behind the integrated phase-locked control RF chip through the PID hardware current stabilization circuit, so that the current of the entire drive circuit is constant, and its current size is set by the microcontroller through the DAC2 signal. In the parameter control of the microwave plasma lighting system, constant current control is very important, which avoids the mutual change of multiple input quantities when the plasma light source mismatches the load during the startup process, causing the wrong judgment of the light source state monitoring. Moreover, during the entire working process, the microcontroller adjusts the attenuator through the constant current PID circuit to keep the circuit with the desired current level, avoiding the overshoot of the circuit power and damage to the power amplifier. In the stable operation stage, the microcontroller can also achieve the dimming effect by adjusting and fixing the circuit current setting value. In addition, the constant current effectively avoids the flickering and stroboscopic when the microwave plasma light source is working stably, maintains the stability of the light intensity, and improves the visual experience and comfort of the microwave light source lighting. Compared with the traditional direct measurement of light intensity, the system design of indirectly realizing the radiation stability of the microwave plasma light source by controlling the circuit current feedback of the present invention is simpler and easy to implement.

[0024] The first PWM signal output by the microcontroller controls the drain of the power amplifier tube through the switch circuit, and modulates the RF signal output to the plasma light source into a pulsed RF signal through the PWM path. Compared with the prior art using pulse modulation control circuit chips, the parameters such as the period and duty cycle of the pulse signal output by this method are more accurate and flexible to adjust, and can better meet the requirements of the plasma light source. Tests have shown that the use of pulsed RF modulation signals can allow more light to be emitted from the resonator bulb, which has higher luminous efficiency than the plasma light source system using continuous carrier energy, saves electrical power, and can also bring about a dimming effect.

[0025] The present invention also provides the following technical solutions:

[0026] An automatic control method for a microwave plasma lighting system, comprising the following steps:

[0027] Step 1: Write the input frequency setting value of the plasma light source, the circuit current setting value, and the initial value of the static operating point of the power amplifier tube grid into the microcontroller;

[0028] Step 2: Change the input frequency setting value to quickly sweep from point F1 higher than the resonance frequency point to point F0 as the resonance frequency point. When the frequency sweeps to point F0, the microcontroller reduces the circuit current to the rated value through the DAC2 signal, collects the incident power measurement value Pin0 at the current F0 point through the ADC3 signal, and the microcontroller continues to sweep downward from point F0 by 2 - 3Mhz, and collects the incident power measurement value Pin1 at the current frequency point through ADC3;

[0029] Step 3: Determine whether the plasma light source is broken down by comparing Pin0 and Pin1. If Pin0≥Pin1, it is considered that the gas in the bulb is not broken down, and after a delay for a period of time, return to Step 2. If Pin0<Pin1, it is determined that the light source has been broken down and lit to generate plasma, and then enter Step 4;

[0030] Step 4: Change the input frequency to continue sweeping downward, and at the same time collect the circuit current measurement value when the input frequency changes through the ADC2 signal, and determine whether the circuit current exceeds the rated circuit current range. Once it exceeds the range, stop sweeping downward;

[0031] Step 5: Control the input frequency to sweep upward, and at the same time collect the corresponding incident power when the input frequency changes through the ADC3 signal, and determine whether the incident power measurement value increases as the frequency increases. If it no longer increases, stop sweeping upward and enter the waiting state;

[0032] Step 6: Fix the incident frequency setting value and the circuit current setting value unchanged through the digital phase-locked loop and the DAC2 signal, and monitor the circuit current measurement value and the reflected power measurement value through the ADC2 signal and the ADC4 signal;

[0033] Step 7: Determine whether the circuit current measurement value exceeds the rated circuit current range. Once it exceeds the range, return to Step 5. Otherwise, determine whether the reflected power measurement value is less than the threshold preset in the microcontroller. Once it is less than the threshold, enter Step 8. Otherwise, return to Step 6;

[0034] Step 8: The circuit current setting value is adjusted and fixed through the DAC2 signal to keep the final operating current value of the plasma lighting system unchanged, and the input frequency setting value is changed to perform a small frequency sweep upward and downward, and at the same time, the corresponding reflected power when the input frequency setting value is changed is collected through the ADC4 signal; and the input frequency corresponding to the minimum value of each reflected power is found, and the input frequency is adjusted to the input frequency corresponding to the minimum value of each reflected power;

[0035] Step 9: Determine whether the execution times of step 8 are not less than the rated times. If it is less than the rated times, return to step 8 after a delay. Otherwise, go to step 10, indicating that it enters the running state.

[0036] Step 10: Use the DAC1 signal to adjust the static operating point of the power amplifier gate so that the power amplifier tube works in Class C, and open the PWM channel to perform pulse modulation of the RF signal;

[0037] Step 11: Change the input frequency to perform a small frequency sweep, and at the same time collect the corresponding reflected power measurement value when the input frequency changes through the ADC4 signal, find the minimum value of each reflected power collected, and adjust the input frequency to the frequency corresponding to the minimum value;

[0038] Step 12: The temperature, incident power and reflected power of the RF power amplifier are collected through the ADC1 signal, ADC3 signal and ADC4 signal, and it is determined whether the temperature and the reflection coefficient are less than the corresponding threshold values ​​preset in the microcontroller. If they are both less than the threshold values, the process of step 11 is repeated after a delay. Otherwise, if the temperature exceeds 85 degrees or the reflection coefficient is greater than the set value, it indicates a sudden change or failure of the luminous state of the plasma light source, and the RF power signal is turned off. After waiting for a long time, return to step 2 and restart the execution.

[0039] The above method essentially divides the working process of the microwave plasma lighting system into three stages: ignition, preheating and operation.

[0040] In the ignition stage, the microcontroller modifies the frequency divider of the digital phase-locked loop to change the input operating frequency, and modifies the DAC2 signal to keep the driver at full power output. It adjusts a PWM signal to make the RF signal work in the continuous wave state CW, and performs a fast frequency sweep from the resonance frequency F0 higher than the plasma light source resonator, and gradually reduces from high frequency. After scanning to the resonance frequency F0, the DAC2 circuit current is reduced, the total input power is controlled to the rated value, and the incident power signal Pin0 corresponding to the analog channel ADC3 is collected at this time. Due to the constant current of the PID, the power of the input circuit is constant after the frequency continues to change. Then, continue to reduce a few megahertz from F0, typically by 2-3MHz, and continue to collect the incident power Pin1 signal corresponding to the ADC3 channel at this time. If Pin1>Pin0, it is determined that the light source has broken down and lit up to generate plasma. If Pin1≤Pin0, it is determined that it has not broken down, and the program is executed again from the beginning. The principle is to judge whether the filling gas in the bulb is broken down by the change of the incident power under constant power. If it is successfully broken down, it enters the preheating stage, and the light is weak at this time.

[0041] After the light source breaks down and enters the preheating stage, the operating frequency continues to be reduced, and the current value ADC2 is continuously detected. When the current value and the preset DAC2 have a certain deviation, or the impedance has been seriously mismatched, the PID can no longer generate a stable current, and the RF source frequency is stopped from being reduced. Next, the frequency is increased, and the signal of the incident power ADC3 is continuously collected. The frequency is continued to increase until the signal of ADC3 no longer increases, and the operating frequency is stopped and kept stable to enter the waiting state. In the waiting state, the temperature of the plasma continues to rise, and the current signal ADC2 is continuously detected at this time. If the current ADC2 deviates from the preset DAC2 again, the operating frequency is continuously increased until the current value ADC2 reaches a stable state again, and the signal of ADC3 no longer increases. In the current stable state, the value of the reflected power ADC4 is continuously collected. If the reflected power is lower than the set threshold, it is determined that the plasma lamp enters the running state. If the reflected power is still higher than or equal to the set threshold, the above-mentioned frequency increase and current ADC2 tracking process are continued.

[0042] In the operation stage, the plasma light source is already working in the arc discharge state and is basically in the load matching state. The goal at this time is to pursue the maximum luminous efficiency and luminous flux output. The microcontroller adjusts the frequency up and down in small increments through the phase-locked loop, and continuously collects ADC4 to determine that the current frequency has the minimum reflected power; after working near the minimum reflected power for a period of time, the third PWM signal is turned on through the switching circuit to realize the pulse modulation of the RF signal, thereby improving the luminous efficiency of the plasma light source. In the pulse modulation state, continue to adjust the operating frequency to follow the minimum reflected power. In the operation stage, when the temperature ADC1 driven by the RF power amplifier exceeds 85 degrees, stop the power output to avoid overheating and damage to the power amplifier.

[0043] The present invention has significant advantages over existing automatic control methods. First, the present invention uses a PID controller to stabilize the circuit current, and achieves successful startup of the plasma lamp by successively tracking the luminous state of the plasma light source and the continuous changes of various parameters. This method not only solves the problem of multi-parameter interaction faced by existing control methods during the startup process, which makes it difficult to judge the plasma state, which is often one of the main reasons for startup failure. The system has high reliability and is easier to implement. Secondly, the present invention can maintain the stability of light intensity during the final operation of the lighting system, while having a dimming effect, and introduces pulsed radio frequency modulation to further improve the light efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The hardware structure diagram of the device adopted in the present invention.

[0045] Figure 2 This is the automatic control principle diagram adopted by the device of the present invention.

[0046] Figure 3(a)-Figure 3(c) It is a control flow chart of the method of the present invention. DETAILED DESCRIPTION

[0047] See also Figure 1 , Figure 2As shown, a microwave plasma lighting control system adopts an integrated phase-locked control RF chip as the core, and an internal microcontroller and a fractional frequency phase-locked loop are integrated in an integrated phase-locked control RF chip. The phase-locked loop generates a radio frequency power signal, and its radio frequency power, frequency and other signal parameters are controlled by the internal microcontroller. The phase-locked loop frequency synthesizer adopts a charge pump digital output, and is composed of a phase frequency detector (PFD), a charge pump (CP), a loop filter (LOOPFILTER), a voltage-controlled oscillator (VCO) and a frequency divider (D-DIV, M-DIV). The microcontroller changes the input frequency of the plasma light source circuit by modifying the frequency divider of the digital phase-locked loop, and adjusts the working state of the power amplifier and the circuit current setting value respectively through the output signals DAC1 and DAC2 of the two digital-to-analog conversion channels, and controls the drain of the power amplifier tube through the switching circuit to realize the pulse modulation of the radio frequency signal through another PWM channel. The microcontroller also collects the temperature of the radio frequency power amplifier, the circuit current, the incident power and the reflected power of the plasma light source circuit respectively through the signals ADC1, ADC2, ADC3 and ADC4 input from the four analog-to-digital conversion channels. The temperature sensor and related channels for obtaining ADC1 can also be integrated as a whole into the microcontroller inside the phase-locked control RF chip.

[0048] The voltage-controlled attenuator is used, and the attenuation is continuously adjustable under the control of the DC bias voltage, which can achieve better matching and attenuation within a wider frequency band. The attenuator can not only adjust the current size and affect the light intensity, but also improve the resolution of the RF signal power. The microcontroller provides a reference voltage for the PID controller through DAC2. The PID controller adjusts the attenuator according to the circuit current collected by ADC2 to achieve the stability of the circuit current. The PID controller is used to stabilize the circuit current, and the circuit current is converted into a voltage signal as the input detection signal of the PID controller. The error signal is generated with the reference signal input by the microcontroller through DAC2, and the PID controller completes the proportional integral differential operation of the error signal. The output control signal is sent to the voltage-controlled attenuator as a DC working voltage to control the attenuator to attenuate the RF signal to varying degrees, thereby forming a closed-loop negative feedback. Automatic current regulation is achieved to maintain the stability of the light intensity.

[0049] Pulse modulation is used to modulate the RF signal output to the plasma light source into a pulse. A switch circuit is added after the DC power supply of the power amplifier. The microcontroller outputs a pulse signal through the PWM path as a switch signal to control the on and off of the switch circuit, so that the amplifier outputs a pulse RF signal RFout, and the microcontroller can adjust various parameters of the pulse RF signal.

[0050] Switch the operating state of the power amplifier. Since the class-AB amplifier has a large output power and the class-C amplifier has a high efficiency, the microcontroller adjusts the static operating point of the power amplifier gate through DAC1, so that the power amplifier operates in class-AB at the initial stage of the plasma light source startup and in class-C during stable arc discharge.

[0051] See Figure 3(a)-Figure 3(c) As shown, an automatic control method for a microwave plasma lighting system successively includes the following steps:

[0052] Step 1: Write the input frequency set value, circuit current set value, and initial value of the static operating point of the power amplifier tube into the microcontroller. The microcontroller adjusts the input frequency set value, circuit current set value, and static operating point of the power amplifier tube to the initial values through the digital phase-locked loop and DAC1, DAC2.

[0053] Step 2: The microcontroller changes the input frequency set value to perform a fast frequency sweep from point F1 (higher than the resonant frequency point) to point F0 (resonant frequency point). When the frequency sweeps to point F0, the microcontroller reduces the circuit current to the rated value through DAC2, and collects the incident power measurement value Pin0 at the current F0 point through ADC3. The microcontroller continues to sweep the frequency downward from point F0 by 2 - 3Mhz, and collects the incident power measurement value Pin1 at the current frequency point through ADC3.

[0054] Step 3: The microcontroller determines whether the plasma light source is broken down by comparing Pin0 and Pin1. If Pin0 ≥ Pin1, it is considered that the gas in the bulb has not been broken down, and after a delay period, it returns to Step 2. If Pin0 < Pin1, it is determined that the light source has been broken down and plasma has been generated, and then it enters Step 4.

[0055] Step 4: The microcontroller changes the input frequency and continues to sweep the frequency downward. At the same time, it collects the circuit current measurement value when the input frequency changes through ADC2, and determines whether the circuit current exceeds the rated circuit current range. Once it exceeds the range, it stops sweeping the frequency downward;

[0056] Step 5: The microcontroller controls the input frequency to sweep upward. At the same time, it collects the corresponding incident power when the input frequency changes through ADC3, and determines whether the incident power measurement value increases as the frequency increases. If it no longer increases, it stops sweeping the frequency upward and enters the waiting state.

[0057] Step 6: Fix the incident frequency set value and circuit current set value unchanged through the digital phase-locked loop and DAC2 signal, and monitor the circuit current measurement value and reflected power measurement value through the ADC2 signal and ADC4 signal;

[0058] Step 7: Determine whether the circuit current measurement value exceeds the circuit current rated range. If it exceeds the range, return to step 5. Otherwise, determine whether the reflected power measurement value is less than a threshold value preset in the microcontroller. If it is less than the threshold value, enter step 8. Otherwise, return to step 6.

[0059] Step 8: The circuit current setting value is adjusted and fixed through the DAC2 signal to keep the final operating current value of the plasma lighting system unchanged, and the input frequency setting value is changed to perform a small frequency sweep upward and downward, and at the same time, the corresponding reflected power when the input frequency setting value is changed is collected through the ADC4 signal; and the input frequency corresponding to the minimum value of each reflected power is found, and the input frequency is adjusted to the input frequency corresponding to the minimum value of each reflected power;

[0060] Step 9: Determine whether the execution times of step 8 are not less than the rated times. If it is less than the rated times, return to step 8 after a delay. Otherwise, go to step 10, indicating that it enters the running state.

[0061] Step 10: Use the DAC1 signal to adjust the static operating point of the power amplifier gate so that the power amplifier tube works in Class C, and open the PWM channel to perform pulse modulation of the RF signal;

[0062] Step 11: Change the input frequency to perform a small frequency sweep, and at the same time collect the corresponding reflected power measurement value when the input frequency changes through the ADC4 signal, find the minimum value of each reflected power collected, and adjust the input frequency to the frequency corresponding to the minimum value;

[0063] Step 12: The temperature, incident power and reflected power of the RF power amplifier are collected through the ADC1 signal, ADC3 signal and ADC4 signal, and it is determined whether the temperature and the reflection coefficient are less than the corresponding threshold values ​​preset in the microcontroller. If they are both less than the threshold values, the process of step 11 is repeated after a delay. Otherwise, if the temperature exceeds 85 degrees or the reflection coefficient is greater than the set value, it indicates a sudden change or failure of the luminous state of the plasma light source, and the RF power signal is turned off. After waiting for a long time, return to step 2 and restart the execution.

[0064] The parts of the present invention that are not described in detail belong to the known technology in the art. The above-described embodiments are only descriptions of the preferred implementation of the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation described. Under the premise of not departing from the design spirit of the present invention, various modifications and improvements made by ordinary technicians in this field to the technical solution of the present invention should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A microwave plasma lighting system, comprising a radio frequency energy control area responsible for power output and a plasma light source that absorbs radio frequency power to maintain light emission; characterized in that: The radio frequency energy control area includes: An integrated phase-locked control radio frequency chip, internally integrating a microcontroller and a fractional frequency phase-locked loop, wherein the integrated phase-locked control radio frequency chip generates a radio frequency power signal; A switch circuit connected to the first output terminal of the integrated phase-locked control radio frequency chip; A power amplifier connected to the second output terminal of the integrated phase-locked control radio frequency chip and connected to the switch circuit; A PID current stabilization circuit connected to the third output terminal of the integrated phase-locked control radio frequency chip; A voltage controlled attenuator connected to the PID current stabilization circuit; A detection circuit connected to the input end of the integrated phase-locked control radio frequency chip; Wherein, the microcontroller outputs a first PWM signal via the first output terminal, and the first PWM signal is input into the switching circuit; the microcontroller outputs a DAC1 signal after filtering and digital-to-analog conversion via the second output terminal, and the DAC1 signal is input into the power amplifier to switch the working state of the power amplifier tube of the power amplifier; the microcontroller outputs a DAC2 signal after filtering and digital-to-analog conversion via the third output terminal, and the DAC2 signal is input into the PID current stabilization circuit, and the DAC2 signal controls the voltage-controlled attenuator behind the integrated phase-locked control RF chip through the PID hardware current stabilization circuit; Among them, the input end of the microcontroller uses the data acquisition of four analog-to-digital conversion channels as the plasma light source input control signal, wherein the first analog-to-digital conversion channel is an ADC1 signal for collecting the temperature driven by the RF power amplifier, the second analog-to-digital conversion channel is an ADC2 signal for collecting the circuit current measurement value, the third analog-to-digital conversion channel is an ADC3 signal for collecting the incident power measurement value of the plasma light source circuit, and the fourth analog-to-digital conversion channel is an ADC4 signal for collecting the reflected power measurement value.

2. A microwave plasma lighting system according to claim 1, characterized in that: The integrated phase-locked control radio frequency chip works in a single carrier state and uses a fast frequency hopping technology to rapidly change the operating frequency; the microcontroller is configured to change the operating frequency setting value by modifying the frequency divider of the fractional frequency phase-locked loop.

3. A microwave plasma lighting system according to claim 1, characterized in that: The DAC2 signal controls the voltage-controlled attenuator behind the integrated phase-locked control RF chip through the PID hardware current stabilization circuit, so that the current of the entire drive circuit is constant, and the current size is set by the microcontroller through the DAC2 signal.

4. A microwave plasma lighting system according to claim 1, characterized in that: The first PWM signal controls the drain of the power amplifier tube through the switch circuit, and modulates the radio frequency signal output to the plasma light source into a pulsed radio frequency signal through the first PWM signal.

5. A microwave plasma lighting system according to claim 1, characterized in that: The DAC1 signal and the DAC2 signal are respectively generated by filtering and digital-to-analog conversion of the second PWM signal and the third PWM signal generated by the microcontroller.

6. A microwave plasma lighting system according to claim 1, characterized in that: The temperature sensor generating the ADC1 signal and its associated channels can be integrally integrated within the microcontroller inside the integrated phase-locked control radio frequency chip.

7. An automatic control method for a microwave plasma lighting system according to any one of claims 1 to 6, characterized in that: The method includes the following steps: Step 1: Write the input frequency set value of the plasma light source, the circuit current set value, and the initial value of the static operating point of the power amplifier tube gate into the microcontroller. Step 2: Change the input frequency set value, perform a fast frequency sweep from point F1 higher than the resonant frequency point to point F0 as the resonant frequency point. When the frequency sweeps to point F0, the microcontroller reduces the circuit current to the rated value through the DAC2 signal, collects the incident power measurement value Pin0 at the current F0 point through the ADC3 signal. The microcontroller continues to sweep the frequency downward from point F0 by 2 - 3Mhz, and collects the incident power measurement value Pin1 at the current frequency point through the ADC3 signal. Step 3: Determine whether the plasma light source is broken down by comparing Pin0 and Pin1. If Pin0 ≥ Pin1, it is considered that the gas inside the light source is not broken down. After a delay for a period of time, return to Step 2. If Pin0 < Pin1, it is determined that the gas inside the light source has been broken down and plasma is generated and lit, and then enter Step 4. Step 4: Change the input frequency and continue to sweep the frequency downward. At the same time, collect the circuit current measurement value when the input frequency changes through the ADC2 signal, and determine whether the circuit current exceeds the rated circuit current range. Once it exceeds the range, stop sweeping the frequency downward. Step 5: Control the input frequency to sweep upward. At the same time, collect the corresponding incident power when the input frequency changes through the ADC3 signal, and determine whether the incident power measurement value increases as the frequency increases. If it no longer increases, stop sweeping the frequency upward and enter the waiting state. Step 6: Fix the incident frequency set value and the circuit current set value unchanged through the digital phase-locked loop and the DAC2 signal, and monitor the circuit current measurement value and the reflected power measurement value through the ADC2 signal and the ADC4 signal. Step 7: Determine whether the circuit current measurement value exceeds the rated circuit current range. Once it exceeds the range, return to Step 5. Otherwise, determine whether the reflected power measurement value is less than the threshold preset in the microcontroller. Once it is less than the threshold, enter Step 8. Otherwise, return to Step 6. Step 8: Adjust and fix the circuit current set value to the current value for the final operation of the plasma lighting system through the DAC2 signal, and change the input frequency set value to perform small upward and downward frequency sweeps. At the same time, collect the corresponding reflected power when the input frequency set value changes through the ADC4 signal; and find the input frequency corresponding to the minimum value of each reflected power, and adjust the input frequency to the input frequency corresponding to the minimum value of each reflected power. Step 9: Determine whether the execution times of Step 8 are not less than the rated times. If it is less than the rated times, after a delay for a period of time, return to Step 8. Otherwise, enter Step 10, indicating entering the operating state. Step 10: Use the DAC1 signal to adjust the static operating point of the power amplifier gate so that the power amplifier tube works in Class C, and open the PWM channel to perform pulse modulation of the RF signal; Step 11: Change the input frequency to perform a small frequency sweep, and at the same time collect the corresponding reflected power measurement value when the input frequency changes through the ADC4 signal, find the minimum value of each reflected power collected, and adjust the input frequency to the frequency corresponding to the minimum value; Step 12: The temperature, incident power and reflected power of the RF power amplifier are collected through the ADC1 signal, ADC3 signal and ADC4 signal, and it is determined whether the temperature and the reflection coefficient are less than the corresponding threshold values ​​preset in the microcontroller. If they are both less than the threshold values, the process of step 11 is repeated after a delay. Otherwise, if the temperature exceeds 85 degrees or the reflection coefficient is greater than the set value, it indicates a sudden change or failure of the luminous state of the plasma light source, and the RF power signal is turned off. After waiting for a long time, return to step 2 and restart the execution.

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