Solid-state microwave source plasma light source modulation method and system

Abstract

The invention discloses a solid-state microwave source plasma light source modulation method and system, the advantage that a solid-state microwave source is easy to control at low voltage is utilized, a frequency spectrum range with a certain width is broadened towards two sides by taking a working frequency as a center, and when a microwave light source emits light, the frequency point of the actual working frequency is within the frequency spectrum range broadened by the central frequency point. High-frequency oscillation is generated in a certain period, so that a frequency point is continuously changed; in the starting stage of the microwave plasma light source, under the condition of spectrum broadening, a continuous wave working mode is used. In a stable arc discharge stage and when heat balance is achieved, pulse power modulation waveforms with a certain duty ratio are superposed while spectrum broadening is carried out, and electromagnetic radiation is reduced and the luminous efficiency of the microwave light source is improved under the condition of equal input electric power by changing the duty ratio and the modulation frequency.

Description

Technical Field

[0001] The invention relates to the technical field of solid-state microwave source plasma light sources, and in particular to a solid-state microwave source plasma light source modulation method and system. Background Art

[0002] Microwave light source is an electrodeless light source that uses microwave energy to excite gas discharge. There is no metal electrode in the arc tube of the microwave light source. It is just a quartz or ceramic material that seals a buffer gas and fills it with luminescent elements such as metal halides to produce plasma light. Therefore, the life of the microwave light source has been greatly improved. The plasma light source allows the quartz material lamp beads to work at a high temperature of more than 1000K, which is more conducive to the broadening of the discharge spectrum of the luminescent elements. It can emit a continuous full spectrum from ultraviolet to infrared. It is an excellent light source that is truly similar to the solar spectrum. It has the advantages of full spectrum, high brightness, long life and high light efficiency, and has broad application prospects.

[0003] The early microwave plasma light source was a microwave sulfur lamp, which used a magnetron to generate energy. The microwave frequency generally operated at 2.45GHz and the power was above 700W. Due to the limited life of the magnetron filament and the need for a motor to drive the sulfur lamp bulb to rotate and dissipate heat, the life of the sulfur lamp was affected. Another problem is that the electromagnetic radiation generated by high-power microwaves requires the sulfur lamp to adopt various shielding measures to reduce the emission of electromagnetic radiation, such as using a metal mesh resonant cavity and adding a high-density copper wire mesh or stainless steel metal mesh in front of the light-transmitting glass cover to reduce radiation interference with other products. The use of metal mesh shielding measures not only reduces the transmittance of the light source, but also increases the complexity and cost of the lamp.

[0004] In recent years, semiconductor solid-state microwave sources have developed rapidly to drive plasma luminescence. LDMOS or GaN devices are used as microwave amplifiers. The resonant cavity generates a concentrated electric field near the lamp bead, which breaks down the gas mixture 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. Typical applications on the market include ceramic resonator plasma light sources and coaxial resonator light sources. However, although the use of solid-state microwave sources has improved the life of plasma light sources, the electromagnetic radiation generated by microwave energy is still a serious problem. Even with various shielding measures, it is difficult to pass the harsh electromagnetic interference test at the operating frequency point.

[0005] In addition, although the microwave plasma light source has a high light efficiency, compared with other light source lighting systems, in addition to the DC power supply, a microwave driver that generates microwaves is added. Due to the limitation of the energy conversion efficiency of the radio frequency power amplifier, these all consume a certain amount of energy, which generally leads to a reduction of about 30% in the luminous efficiency of the microwave light source system. Therefore, new methods are needed to improve the system luminous efficiency of microwave light sources without increasing energy consumption. Summary of the invention

[0006] In order to solve the technical problems existing in the background technology, the present invention proposes a solid-state microwave source plasma light source modulation method and system.

[0007] A solid-state microwave source plasma light source modulation method proposed by the present invention comprises the following steps:

[0008] During the start-up phase of the plasma light source, the operating frequency is set to a preset spectrum broadening range extending from the central operating frequency point to both sides, and a continuous wave operating mode is used;

[0009] In the stable arc discharge stage, the preset spectrum broadening range is maintained, and a pulse power modulation waveform with a preset duty cycle is superimposed.

[0010] Preferably, the preset spectrum broadening range is (F0-Δf, F0+Δf), F0 is the center operating frequency, Δf is the preset broadening value, 0.1MHz≤Δf≤10MHz, the value of Δf is determined according to the use frequency F0, generally Δf<0.5%*F0, wherein Δf<0.25%*F0 is better.

[0011] Preferably, the preset duty cycle is 50%-100%.

[0012] Preferably, during the start-up phase of the plasma light source, spectrum broadening is generated by a voltage-controlled oscillator;

[0013] In the stable arc discharge stage, the pulse power modulation waveform is generated by square wave controlling the secondary amplifier drain modulation or the microwave switch after the voltage controlled oscillator;

[0014] Preferably, the pulse power modulation waveform is a square wave, and a triangle wave or a sawtooth wave is used to control the voltage-controlled oscillator.

[0015] Preferably, during the startup phase of the plasma light source, the operating frequency is set to a preset spectrum widening range that is widened to both sides from the central operating frequency point, and a continuous wave operating mode is used, specifically: during the startup phase of the plasma light source, a square wave pulse signal is output by a microcontroller, and the square wave pulse signal is shaped by an RC filter to form a triangular wave or a sawtooth wave with a preset amplitude to form a modulated waveform, and then the operating frequency is oscillated within a bandwidth of 2Δf on both sides of the central operating frequency point F0 by a voltage-controlled oscillator to widen the frequency point to both sides to form an oscillating waveform.

[0016] Preferably, in the stable arc discharge stage, the preset spectrum broadening range is maintained, and a pulse power modulation waveform with a preset duty cycle is superimposed. Specifically, a pulse modulation waveform with a preset frequency (preferably 20-100kHz) and a duty cycle (preferably 50-100%) is generated by a microcontroller, and the drain of a low-power RF power amplifier is modulated through a switching tube. The pulse modulation waveform is preferably a square wave.

[0017] Preferably, in the stable arc discharge stage, the preset spectrum broadening range is maintained, and a pulse power modulation waveform with a preset duty cycle is superimposed. Specifically, a pulse modulation waveform with a preset frequency (preferably 20-100kHz) and a duty cycle (preferably 50-100%) is generated by a microcontroller to control the microwave switch at the output end of the voltage-controlled oscillator to generate a pulse power modulation waveform.

[0018] In the present invention, the proposed solid-state microwave source plasma light source modulation method utilizes the advantage of the solid-state microwave source being easy to control at low voltage, takes the working frequency as the center, and widens the spectrum range of a certain width to both sides. When the microwave light source emits light, the frequency point of the actual working frequency generates high-frequency oscillations with a certain period within the spectrum range widened by this center frequency point, so that the frequency point changes continuously. In the startup phase of the microwave plasma light source, when the spectrum is widened, a continuous wave working mode is used. In the stable arc discharge phase, when thermal equilibrium is reached, a pulse power modulation waveform with a certain duty cycle is superimposed while the spectrum is widened. By changing the duty cycle and the modulation frequency, the electromagnetic radiation is reduced and the luminous efficiency of the microwave light source is improved under the condition of equal input power.

[0019] The present invention also provides a solid-state microwave source plasma light source modulation system for implementing the above-mentioned solid-state microwave source plasma light source modulation method.

[0020] Preferably, it comprises: a voltage-controlled oscillator, a microcontroller, an RC filter (resistance-capacitance circuit), a microwave switch, a switch tube and a secondary power amplifier;

[0021] Preferably, it also includes a final-stage high-power amplifier for performing final-stage amplification on the signal output by the secondary power amplifier.

[0022] Preferably, it includes: a wireless transmitting chip, which integrates a register and a phase-locked source, realizes the movement of the working center frequency F0 by a fast frequency hopping method, realizes the spectrum broadening by a frequency shift keying method, and generates a pulse power signal waveform with a duty cycle by an amplitude modulation phase-locked source modulation mode.

[0023] In the present invention, the proposed solid-state microwave source plasma light source modulation system has a technical effect similar to the above-mentioned solid-state microwave source plasma light source modulation method, so it is not described in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic structural diagram of an implementation of a solid-state microwave source plasma light source modulation system proposed in the present invention.

[0025] Figure 2 This is a DC signal diagram of an implementation of a solid-state microwave source plasma light source modulation method proposed in the present invention.

[0026] Figure 3 A single center frequency diagram in one embodiment of a solid-state microwave source plasma light source modulation method proposed in the present invention.

[0027] Figure 4 A superimposed wave diagram in an implementation manner of a solid-state microwave source plasma light source modulation method proposed by the present invention.

[0028] Figure 5 This is a center frequency oscillation diagram in one implementation of a solid-state microwave source plasma light source modulation method proposed by the present invention. DETAILED DESCRIPTION

[0029] like Figure 1 As shown, Figure 1 This is a structural schematic diagram of an embodiment of a solid-state microwave source plasma light source modulation system proposed by the present invention. Figure 2 This is a DC signal diagram in an embodiment of a solid-state microwave source plasma light source modulation method proposed by the present invention. Figure 3 A single center frequency diagram in one embodiment of a solid-state microwave source plasma light source modulation method proposed by the present invention, Figure 4 A superimposed wave diagram in an embodiment of a solid-state microwave source plasma light source modulation method proposed by the present invention, Figure 5 This is a center frequency oscillation diagram in one implementation of a solid-state microwave source plasma light source modulation method proposed by the present invention.

[0030] A solid-state microwave source plasma light source modulation method proposed by the present invention comprises the following steps:

[0031] During the start-up phase of the plasma light source, the operating frequency is set to a preset spectrum widening range that is widened to both sides from the central operating frequency point, and the continuous wave operating mode is used. Specifically, the preset spectrum widening range is (F0-Δf, F0+Δf), F0 is the central operating frequency point, Δf is the preset widening value, 0.1MHz≤Δf≤10MHz, and the value of Δf is determined according to the operating frequency F0. Generally, Δf<0.5%*F0, and Δf<0.25%*F0 is better.

[0032] In the stable arc discharge stage, the preset spectrum broadening range is maintained, and a pulse power modulation waveform with a preset duty cycle is superimposed. Specifically, the pulse power modulation waveform is a square wave, the preset duty cycle is 50%-100%, and the modulation period is 20-100kHz.

[0033] In a specific embodiment, during the plasma light source startup phase, spectrum broadening is generated by a voltage-controlled oscillator; during the stable arc discharge phase, a pulse power modulation waveform is generated by square wave-controlled secondary amplifier drain modulation or a microwave switch after the voltage-controlled oscillator. Specifically, the pulse power modulation waveform is a square wave, and the voltage-controlled oscillator is controlled by a triangle wave or a sawtooth wave.

[0034] In this embodiment, the proposed solid-state microwave source plasma light source modulation method and system utilizes the advantage of the solid-state microwave source being easy to control at low voltage, takes the working frequency as the center, and widens the spectrum range of a certain width to both sides. When the microwave light source emits light, the frequency point of the actual working frequency generates high-frequency oscillations with a certain period within the spectrum range widened by this center frequency point, so that the frequency point changes continuously. In the startup phase of the microwave plasma light source, when the spectrum is widened, a continuous wave working mode is used. In the stable arc discharge phase, when thermal equilibrium is reached, a pulse power modulation waveform with a certain duty cycle is superimposed while the spectrum is widened. By changing the duty cycle and modulation frequency, the electromagnetic radiation is reduced and the luminous efficiency of the microwave light source is improved under the condition of equal input power.

[0035] The principle of this embodiment is that the microwave light source generally works in a frequency band above 300MHz. In the electromagnetic interference standard test of this frequency band, the 6dB intermediate frequency bandwidth of the general receiver is 120kHz. The method of oscillating the working frequency point within the range of several megahertz adopted in this embodiment reduces the integration time of the working frequency at a single measurement point, thereby reducing the average radiation power of the measurement frequency point. In the stable solitary light discharge stage, the microwave power pulse modulation method is adopted to increase the peak power of the excitation lamp bead at the same average power. For example, when the average power is 100W, if the duty cycle is 83%, the peak power can reach 120W. After the plasma light source is ignited, the spatial plasma density is positively correlated with the excitation electric field strength when it is greater than the maintenance field strength. The high electric field itself can produce a higher electron density and increase the luminous intensity. After the pulse modulation, it can also promote the arc distribution to move outward, further allowing more light to penetrate the quartz bulb shell and improve the luminous efficiency; on the other hand, the increase in electron density reduces the skin depth of microwaves in the plasma, which can produce better absorption of microwaves, so that microwaves cannot penetrate the plasma, thereby further reducing electromagnetic radiation to the outside world.

[0036] Based on the above solid-state microwave source plasma light source modulation method, this embodiment also proposes a solid-state microwave source plasma light source modulation system.

[0037] Reference Figure 1 In a specific embodiment, the solid-state microwave source plasma light source modulation system includes: a voltage-controlled oscillator 2, a microcontroller 1, an RC filter 5, a microwave switch 4, a switch tube 3 and a secondary power amplifier 6.

[0038] In the specific working mode of the modulation system of this embodiment, at the startup stage of the plasma light source, a pulse signal is outputted by the microcontroller 1, and the pulse signal is shaped by the RC filter 5 to form a triangular wave with a preset amplitude, forming a modulated waveform, and then the operating frequency is oscillated within a bandwidth of 2Δf on both sides of the center operating frequency F0 by the voltage-controlled oscillator 2 to widen the frequency point to both sides, forming an oscillating waveform.

[0039] In the stable arc discharge stage, the preset spectrum broadening range is maintained, and a pulse power modulation waveform with a preset duty cycle is superimposed. Specifically, the secondary power amplifier 6 is a low-power RF power amplifier, and a pulse modulation waveform with a preset frequency and duty cycle is generated by the microcontroller 1. The secondary power amplifier 6 is drain modulated through the switch tube 3 to achieve pulse superposition. The microcontroller 1 can also generate a pulse modulation waveform with a preset frequency and duty cycle to control the microwave switch 4 at the output end of the voltage-controlled oscillator 2 to generate a pulse power modulation waveform.

[0040] In actual design, a final-stage high-power amplifier 7 may be provided at the output end of the secondary power amplifier 6 to perform final-stage amplification on the signal output by the secondary power amplifier 6 .

[0041] In the above specific implementation manner, a frequency source of a voltage-controlled oscillator may be used, and a triangle wave or a sawtooth wave may be superimposed on a control signal or a modulation signal of the frequency source. Figure 1 This is the schematic diagram of the MCU modulating the drain of the low-power amplifier PA through the modulation switch tube. After the drain is modulated, a pulse power with a certain duty cycle is formed, and then further amplified by the final stage to drive the plasma light source to produce high-intensity light. At the voltage control end, if a DC signal (such as Figure 2 ), the voltage-controlled oscillator generates a single center frequency F0 microwave, see Figure 3 Changing the DC control voltage will change the center frequency F0. Furthermore, a triangle wave or sawtooth wave with a certain amplitude is superimposed on this DC signal, such as Figure 4 The superimposed triangular wave is shown. According to the voltage-controlled sensitivity of the voltage-controlled oscillator, the spectrum of the center frequency F0 is widened by Δf on both sides, and the sawtooth wave or triangular wave makes the actual operating frequency oscillate back and forth within the 2Δf bandwidth near the center frequency F0, as shown in Figure 5 As shown. After the microwave light source generates gas breakdown, plasma is generated, and this broadened spectrum is always loaded near the center frequency F0. After the gas breakdown, as the center frequency F0 is constantly changed and moved, the broadened spectrum 2Δf also moves with the center frequency F0, controlling the efficient coupling of microwave energy into the plasma, and the gas transitions from glow discharge to arc discharge within tens of seconds. In the stable arc discharge stage, a pulse power modulation waveform is added, and a pulse modulation waveform with a certain frequency and duty cycle is generated by a microcontroller. The intermediate low-power RF power amplifier PA is drain modulated through the modulation switch tube, or the microwave switch after the voltage-controlled oscillator is controlled to generate a pulse power modulation waveform of several hundred watts.

[0042] After pulse modulation, under the condition of consuming the same electric power, even if the average power is equal, the peak value of the modulated microwave power is higher than the unmodulated average power, thus producing a higher plasma electron density and luminous intensity. The high electron density reduces the skin depth and produces better absorption and shielding of microwaves, thereby suppressing the radiation interference of the RF power to the outside world. It should be noted that after pulse modulation, the instability caused to the plasma should be controlled to prevent the light source from flickering and extinguishing.

[0043] In another specific implementation of the solid-state microwave source plasma light source modulation system of this embodiment, it includes: a wireless transmitting chip, the wireless transmitting chip is integrated with a register and a phase-locked source. The method of fast frequency hopping is realized by configuring the register to realize the movement of the working center frequency F0, the frequency shift keying method is used to realize the widening of the spectrum, and the amplitude modulation phase-locked source modulation mode is used to generate a pulse power signal waveform with a duty cycle. The frequency source with the wireless transmitting chip as the core realizes the widening of the spectrum by configuring the register corresponding to the modulation mode of the wireless transmitting chip. The register is configured on the basis of the basic frequency, and the center frequency F0 is switched by constantly changing the value of the register in the application. The method of fast frequency hopping is realized by configuring the built-in register to realize the movement of the center frequency F0, so as to control the microwave energy to be coupled into the plasma with the maximum amplitude. While the center frequency F0 is moving, the frequency shift keying or other methods are used to realize the widening of the spectrum, and the modulation modes such as amplitude modulation OOK (phase-locked source) are used to generate a pulse power signal waveform with a duty cycle, and the plasma light source is further driven after multi-stage amplification.

[0044] The actual effect of this embodiment is that by widening the spectrum near the center frequency point, the working frequency point oscillates back and forth near the center frequency point, effectively reducing the integration time at a certain measurement frequency point during electromagnetic interference measurement, thereby reducing the average radiation power measured at the frequency point. When equilibrium is reached in the stable arc discharge stage, a pulse power modulation waveform with a certain duty cycle is superimposed while the spectrum is widened, so as to achieve the conditions of the same input power, increase the electron density, reduce electromagnetic radiation and improve the luminous efficiency of the microwave light source.

[0045] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A solid-state microwave source plasma light source modulation method, characterized in that: The following steps are involved: During the start-up phase of the plasma light source, the operating frequency is set to a preset spectrum broadening range that is broadened to both sides from the central operating frequency point, and a continuous wave operating mode is used; In the stable arc discharge stage, the preset spectrum broadening range is maintained, and a pulse power modulation waveform with a preset duty cycle is superimposed.

2. The solid-state microwave source plasma light source modulation method according to claim 1, characterized in that: The preset spectrum broadening range is (F0-Δf, F0+Δf), F0 is the center operating frequency, Δf is the preset broadening value, 0.1MHz≤Δf≤10MHz.

3. The solid-state microwave source plasma light source modulation method according to claim 1, characterized in that: The preset duty cycle is 50%-100%.

4. The solid-state microwave source plasma light source modulation method according to claim 1, characterized in that: During the start-up phase of the plasma light source, spectrum broadening is generated by a voltage-controlled oscillator; In the stable arc discharge stage, the pulse power modulation waveform is generated by square wave controlling the secondary amplifier drain modulation or the microwave switch after the voltage controlled oscillator; Preferably, the pulse power modulation waveform is a square wave, and a triangle wave or a sawtooth wave is used to control the voltage-controlled oscillator.

5. The solid-state microwave source plasma light source modulation method according to claim 4, characterized in that: In the plasma light source startup phase, the operating frequency is set to a preset spectrum widening range that is widened to both sides from the central operating frequency point, and a continuous wave operating mode is used, specifically: in the plasma light source startup phase, a square wave pulse signal is outputted by a microcontroller (1), and the square wave pulse signal is shaped by an RC filter (5) to form a triangular wave with a preset amplitude, thereby forming a modulated waveform, and then the operating frequency is oscillated within a bandwidth of 2Δf on both sides of the central operating frequency point F0 by a voltage-controlled oscillator (2) to widen the frequency point to both sides, thereby forming an oscillating waveform.

6. The solid-state microwave source plasma light source modulation method according to claim 5, characterized in that: In the stable arc discharge stage, a preset spectrum broadening range is maintained and a pulse power modulation waveform with a preset duty cycle is superimposed. Specifically, a pulse modulation waveform with a preset frequency and duty cycle requirement is generated by a microcontroller (1), and drain modulation is performed on a low-power radio frequency power amplifier via a switch tube (3).

7. The solid-state microwave source plasma light source modulation method according to claim 5, characterized in that: In the stable arc discharge stage, a preset spectrum broadening range is maintained and a pulse power modulation waveform with a preset duty cycle is superimposed. Specifically, a pulse modulation waveform with a preset frequency and duty cycle is generated by a microcontroller (1) to control a microwave switch (4) at the output end of a voltage-controlled oscillator (2) to generate a pulse power modulation waveform.

8. A solid-state microwave source plasma light source modulation system, used to implement the solid-state microwave source plasma light source modulation method according to any one of claims 1 to 7.

9. The solid-state microwave source plasma light source modulation system according to claim 8, characterized in that: include: Voltage controlled oscillator (2), microcontroller (1), RC filter (5), microwave switch (4), switch tube (3) and secondary power amplifier (6); Preferably, it also includes a final-stage high-power amplifier (7) for performing final-stage amplification on the signal output by the secondary power amplifier (6).

10. The solid-state microwave source plasma light source modulation system according to claim 8, characterized in that: It includes: a wireless transmitting chip, which integrates a register and a phase-locked source, realizes the movement of the working center frequency F0 by a fast frequency hopping method, realizes the spectrum broadening by a frequency shift keying method, and generates a pulse power signal waveform with a duty cycle by an amplitude modulation phase-locked source modulation mode.

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