A solid-state microwave source plasma light source modulation method and system

Abstract

The present invention discloses a solid-state microwave plasma light source modulation method and system. Taking advantage of the ease of low-voltage control of solid-state microwave sources, the system broadens a spectrum range of a certain width on both sides, centered around the operating frequency. When the microwave light source emits light, the actual operating frequency generates high-frequency oscillations at a certain period within the spectrum range broadened from this central frequency point, causing the frequency point to continuously change. During the startup phase of the microwave plasma light source, a continuous wave operating mode is used while the spectrum is broadened. During the stable arc discharge phase, when thermal equilibrium is reached, a pulse power modulation waveform with a certain duty cycle is superimposed on the spectrum broadening. By varying the duty cycle and modulation frequency, the system reduces electromagnetic radiation and improves the luminous efficiency of the microwave light source under conditions of equal input power.

Description

Technical Field

[0001] The present 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 sources are electrodeless light sources that utilize microwave energy to excite gas discharges. The arc tubes of microwave light sources lack metal electrodes. Instead, they consist of a quartz or ceramic material enclosing a buffer gas, which is then filled with luminescent elements such as metal halides to generate plasma light. This significantly improves the lifespan of microwave light sources. Plasma light sources allow quartz lamps to operate at temperatures exceeding 1000K, which further broadens the discharge spectrum of the luminescent elements, producing a continuous, full spectrum from ultraviolet to infrared. These excellent light sources truly resemble the solar spectrum, offering a full spectrum, high brightness, long life, and high luminous efficiency, promising a wide range of applications.

[0003] Early microwave plasma light sources were sulfur lamps, using magnetrons to generate energy. The microwave frequency typically operated at 2.45 GHz, with a power of over 700 W. However, the limited lifespan of the magnetron filament and the motor-driven rotation of the sulfur lamp bulb reduced the lamp's lifespan. Another issue was the electromagnetic radiation generated by high-power microwaves, which necessitated various shielding measures to reduce electromagnetic radiation emission. These measures, such as metal mesh resonant cavities and the addition of high-density copper or stainless steel mesh in front of the translucent glass cover, reduced radiation interference with other products. This metal mesh shielding not only reduced the light transmittance of the light source but also increased the complexity and cost of the lamp.

[0004] In recent years, semiconductor solid-state microwave sources have rapidly developed to drive plasma luminescence. These utilize LDMOS or GaN devices as microwave amplifiers. A resonant cavity generates a concentrated electric field near the bulb, breaking down the gas mixture within the bulb. As the temperature rises, the metal halide within the bulb ionizes, forming an arc discharge and generating high-brightness plasma light radiation. Typical applications include ceramic resonator plasma light sources and coaxial resonator light sources. However, while the use of solid-state microwave sources has improved the lifespan of plasma light sources, electromagnetic radiation generated by microwave energy remains a serious concern. Even with various shielding measures, it is difficult to pass stringent electromagnetic interference tests at the operating frequency.

[0005] Furthermore, although microwave plasma light sources offer high luminous efficiency, compared to other light source lighting systems, in addition to a DC power supply, they also require a microwave driver to generate microwaves. Due to the energy conversion efficiency limitations of radio frequency power amplifiers, this consumes a certain amount of energy, generally reducing the luminous efficiency of microwave light source systems by approximately 30%. Therefore, new methods are needed to improve the 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] The present invention provides a solid-state microwave plasma light source modulation method, comprising the following steps:

[0008] During the plasma light source startup phase, 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] During 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 operating frequency F0, generally Δf<0.5%*F0, among which 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 controlling the drain modulation of the secondary amplifier or the microwave switch after the voltage-controlled oscillator through square wave;

[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 of 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. Then, a voltage-controlled oscillator is used to oscillate the operating frequency within a bandwidth of 2Δf on both sides of the central operating frequency point F0 so that the frequency point is widened 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 the low-power RF power amplifier is modulated through the switching tube. The pulse modulation waveform is preferably a square wave.

[0017] Preferably, during 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 microcontroller generates a pulse modulation waveform with a preset frequency (preferably 20-100kHz) and a duty cycle (preferably 50-100%) to control the microwave switch at the output end of the voltage-controlled oscillator to generate a pulse power modulation waveform.

[0018] The proposed solid-state microwave plasma light source modulation method leverages the ease of low-voltage control of solid-state microwave sources. With the operating frequency as the center, the spectrum is broadened to a predetermined width in both directions. When the microwave source emits light, the actual operating frequency generates high-frequency oscillations with a predetermined period within the broadened spectrum from this central frequency point, causing the frequency point to continuously change. During the startup phase of the microwave plasma light source, while the spectrum is broadened, a continuous wave operating mode is used. During the stable arc discharge phase, when thermal equilibrium is reached, a pulse power modulation waveform with a predetermined duty cycle is superimposed on the spectrum broadening. By varying the duty cycle and modulation frequency, electromagnetic radiation is reduced and the microwave light source's luminous efficiency is improved under the same input power conditions.

[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 includes: a voltage-controlled oscillator, a microcontroller, an RC filter (resistance-capacitance circuit), a microwave switch, a switching 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, adopts a frequency shift keying method to realize spectrum broadening, and adopts an amplitude modulation phase-locked source modulation mode to generate a pulse power signal waveform with a duty cycle.

[0023] In the present invention, the solid-state microwave source plasma light source modulation system proposed 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 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.

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

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

[0027] Figure 4 This is a superimposed wave diagram in an embodiment 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 of an embodiment 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 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 one embodiment of a solid-state microwave source plasma light source modulation method proposed by the present invention. Figure 3 This is 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 This is a superimposed wave diagram in one 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 of an embodiment of a solid-state microwave source plasma light source modulation method proposed by the present invention.

[0030] The present invention provides a solid-state microwave plasma light source modulation method, comprising the following steps:

[0031] During the plasma light source startup phase, the operating frequency is set to a preset spectrum broadening range extending from the central operating frequency toward both sides, using continuous wave operation. Specifically, the preset spectrum broadening range is (F0-Δf, F0+Δf), where F0 is the central operating frequency and Δf is the preset broadening value, 0.1MHz≤Δf≤10MHz. The Δf value is determined by the operating frequency F0. Generally, Δf<0.5%*F0, with Δf<0.25%*F0 being preferred.

[0032] During the stable arc discharge phase, 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 with a preset duty cycle of 50%-100% and a modulation period of 20-100kHz.

[0033] In one embodiment, during the plasma light source startup phase, spectrum broadening is generated by a voltage-controlled oscillator. During the arc discharge stabilization phase, a pulse power modulation waveform is generated by square-wave controlled drain modulation of a secondary amplifier 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 plasma light source modulation method and system leverages the ease of low-voltage control of solid-state microwave sources. With the operating frequency as the center, the spectrum is broadened to a predetermined width in both directions. During microwave light emission, the actual operating frequency generates high-frequency oscillations with a predetermined period within the broadened spectrum from this central frequency, causing the frequency point to continuously change. During the startup phase of the microwave plasma light source, while the spectrum is broadened, a continuous wave operating mode is used. During the stable arc discharge phase, when thermal equilibrium is reached, a pulse power modulation waveform with a predetermined duty cycle is superimposed on the spectrum broadening. By varying the duty cycle and modulation frequency, electromagnetic radiation is reduced and the microwave light source's luminous efficiency is improved under the same input power conditions.

[0035] The principle behind this embodiment is that microwave light sources generally operate in a frequency band above 300 MHz. In standard electromagnetic interference testing for this frequency band, the typical receiver 6dB intermediate frequency bandwidth is 120 kHz. This embodiment employs a method of oscillating the operating frequency within a range of several megahertz to reduce the integration time at a single measurement point, thereby lowering the average radiated power at that measurement frequency. During the stable solitary discharge phase, microwave power pulse modulation can increase the peak power of the excitation lamp while maintaining the same average power. For example, at an average power of 100 W, a duty cycle of 83% can achieve a peak power of 120 W. After ignition of the plasma light source, the spatial plasma density is positively correlated with the excitation electric field strength when it exceeds the maintenance field strength. A high electric field inherently generates higher electron density, enhancing luminous intensity. Combined with pulse modulation, this can also shift the arc distribution outward, further allowing more light to pass through the quartz bulb and improving luminous efficiency. Furthermore, the increased electron density reduces the skin depth of microwaves in the plasma, resulting in better microwave absorption and preventing them from penetrating the plasma, thereby further reducing electromagnetic radiation to the outside world.

[0036] Based on the above-mentioned solid-state microwave source plasma light source modulation method, this embodiment further 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 switching tube 3 and a secondary power amplifier 6.

[0038] In the specific working mode of the modulation system of this embodiment, during the startup phase 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. Then, the voltage-controlled oscillator 2 is used to make the operating frequency oscillate within a bandwidth of 2Δf on both sides of the center operating frequency F0, so that the frequency point is widened to both sides, forming an oscillating waveform.

[0039] During the stable arc discharge phase, a 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. The microcontroller 1 generates a pulse modulation waveform with a preset frequency and duty cycle, and the switch tube 3 performs drain modulation on the secondary power amplifier 6 to achieve pulse superposition. Alternatively, the microcontroller 1 can 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 principle diagram of how the MCU modulates 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, which is then further amplified in 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. The sawtooth wave or triangular wave makes the actual operating frequency oscillate back and forth within a bandwidth of 2Δf near the center frequency F0, as shown in the figure. Figure 5 As shown in the figure, after the microwave light source generates gas breakdown, plasma is generated, and this broadened spectrum is constantly loaded near the center frequency F0. After the gas breakdown, as the center frequency F0 is continuously controlled and shifted, the broadened spectrum 2Δf also moves with the center frequency F0, controlling the efficient coupling of microwave energy into the plasma. The gas transitions from glow discharge to arc discharge within tens of seconds. During the stable arc discharge stage, a pulse power modulation waveform is added. The microcontroller generates a pulse modulation waveform with a certain frequency and duty cycle. The modulation switch tube performs drain modulation on the intermediate low-power RF power amplifier PA, or controls the microwave switch after the voltage-controlled oscillator, generating a pulse power modulation waveform of several hundred watts.

[0042] After pulse modulation, even when consuming the same electrical power and producing the same average power, the peak power of the modulated microwave is higher than the unmodulated average power, resulting in a higher plasma electron density and luminous intensity. The high electron density reduces the skin depth, resulting in better absorption and shielding of microwaves, thereby suppressing the interference of RF power radiation to the outside world. It is important to note that after pulse modulation, the instability of the plasma must be controlled to prevent flickering and extinction of the light source.

[0043] Another specific embodiment of the solid-state microwave plasma light source modulation system of this embodiment includes a wireless transmitter chip integrated with a register and a phase-locked source. The operating center frequency F0 is shifted by configuring the registers for rapid frequency hopping, frequency shift keying (FSK) is used to achieve spectrum widening, and amplitude modulation (OM) phase-locked source modulation is used to generate a pulse power signal waveform with a duty cycle. The frequency source, with the wireless transmitter chip as its core, achieves spectrum widening by configuring registers corresponding to the modulation mode of the wireless transmitter chip. Registers are configured based on the base frequency. During application, the center frequency F0 is switched by continuously changing the register values. Rapid frequency hopping is achieved by configuring the built-in registers to shift the center frequency F0, thereby controlling the maximum coupling of microwave energy into the plasma. While the center frequency F0 is shifting, frequency shift keying (FSK) or other methods are used to achieve spectrum widening. Amplitude modulation (OOK) (phase-locked source) and other modulation modes are used to generate a pulse power signal waveform with a duty cycle. This is further amplified in multiple stages to drive the plasma light source.

[0044] This embodiment achieves the practical effect of broadening the spectrum near the center frequency, causing the operating frequency to oscillate back and forth around it. This effectively reduces the integration time at a specific frequency during electromagnetic interference measurement, thereby lowering the average radiated power measured at that frequency. When equilibrium is reached during the stable arc discharge phase, a pulse power modulation waveform with a specific duty cycle is superimposed on the spectrum broadening. This increases electron density, reduces electromagnetic radiation, and improves the luminous efficiency of the microwave light source under the same input power conditions.

[0045] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection 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 plasma light source startup phase, 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; 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; 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 controlling the drain modulation of the secondary amplifier or the microwave switch after the voltage-controlled oscillator through square wave; The pulse power modulation waveform is a square wave, and the voltage controlled oscillator is controlled by a triangle wave or a sawtooth wave; During the plasma light source startup phase, the operating frequency is set to a preset spectrum widening range that is widened to both sides of the central operating frequency point, and a continuous wave operating mode is used. Specifically, during 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. 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), so that the frequency point is widened to both sides, thereby forming an oscillating waveform.

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, and 0.1 MHz≤Δf≤10 MHz.

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: 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).

5. The solid-state microwave source plasma light source modulation method according to claim 1, 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 microcontroller (1) generates a pulse modulation waveform with a preset frequency and duty cycle requirement to control a microwave switch (4) at the output end of a voltage-controlled oscillator (2) to generate a pulse power modulation waveform.

6. 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 5.

7. The solid-state microwave source plasma light source modulation system according to claim 6, characterized in that: include: A voltage-controlled oscillator (2), a microcontroller (1), an RC filter (5), a microwave switch (4), a switching tube (3) and a secondary power amplifier (6).

8. The solid-state microwave source plasma light source modulation system according to claim 7, characterized in that: 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).

9. The solid-state microwave source plasma light source modulation system according to claim 7, characterized in that: It includes: a wireless transmitting chip, which integrates a register and a phase-locked source. It realizes the movement of the working center frequency F0 by the fast frequency hopping method, adopts the frequency shift keying method to realize the spectrum broadening, and adopts the amplitude modulation phase-locked source modulation mode to generate a pulse power signal waveform with a duty cycle.

Images