TWI574608B - Plant factory with light recipe verification platform - Google Patents

Description

Plant factory light formula verification platform

The present invention relates to plant plants, and more particularly to a light formulation verification platform for plant plants.

According to the United Nations, by 2050, the global population will increase from the current 7.3 billion to 10 billion, and 80% of the population will live in cities. At the same time, 80% of arable land has been used. In addition, the global warming effect caused by local climate anomalies will result in a significant reduction in crop yields and lead to higher food prices. Therefore, the food crisis and food security issues have received great attention from the international community in recent years, and people are paying more and more attention to the way food is produced. Pesticide-free, organic, non-genetically modified agriculture is the future development trend, which makes people constantly seek innovation in planting technology to achieve indoor planting methods without daylight conditions.

Plant factories (called "vertical farming" in Europe and America) can not only solve the food crisis, but also be free from the deterioration of the environment. The plant factory contains four major points of construction, equipment, environmental control, and growth materials. These four key points need to complement each other to maximize their benefits. The general plant factory types are sunlight-use type, sunlight and artificial light source type, and fully artificial light source type. Plant factory equipment includes light sources, fans, hygrometers, water source adjustment, carbon dioxide supply equipment, etc., where the light source is the most critical. At present, plant light sources include cold cathode fluorescent lamps, metal halide lamps, high pressure sodium lamps, fluorescent lamps, and LED (light emitting diode) lamps.

The plant factory has been developed since 1957 and the Netherlands is one of the best growing plants in the country. The newly developed horticultural crops sustainable energy-saving greenhouse production technology and application, combined with the illumination technology, light quality, luminous flux and remote automatic monitoring system of artificial light sources such as LED, can effectively improve the production quality. The future plant plant development goal in the Netherlands is the greenhouse village (Zonneterp), which is based on the concept of recycling to save energy and water to achieve self-sufficiency. With the maturity of LED lighting applications, plant factories that combine LED light sources have also flourished in recent years. The plant growth lamp with LED light source has the advantages of small size, light weight, long life, no heat radiation, adjustable light wavelength, etc., which makes LED lamps favored by multi-stage cultivation plant factories. Although the decline in the price of LED light sources helps the penetration of LED lamps in plant factories, plant physiology knows that different plants have great differences in light perception. Plants can effectively use specific wavelengths of light and have different wavelengths. The light has a small reaction. So instead of providing light to the plants around the clock, there will be a good harvest. Irradiation of ineffective wavelengths of light to plants does not meet the needs of plant growth, only increasing energy consumption and greenhouse gas emissions. In addition, horticultural LED lighting is deeply influenced by regional characteristics, and is highly correlated with local climate, soil, and consumption needs. Therefore, suitable light formulations must be developed for different regions to optimize production and save energy. In addition, the wavelength of illumination required for each plant is not the same. How to use the characteristics of the light source to achieve mass production is the focus of plant development. Since the LED performance parameters, output luminous flux and wavelength are easily affected by the junction temperature rise, the LED light attenuation problem is also considered by the plant factory whether to use the LED light source. Therefore, reducing the LED light attenuation problem and establishing different plant planting requirements The light recipe database is the key to whether plant factories can continue to thrive and have economic value.

At present, the research on the use of LEDs for plant growth lamps can be divided into three major parts, the first is light formula research, the second is based on wireless sensing network environment control and monitoring man-machine system construction, the third In order to propose a high-performance drive architecture to improve the efficiency of the drive circuit, it is described as follows:

Light formula research: Some studies have pointed out that the lm/W of LED light source is not the key to whether LED light source is suitable for plant growth lamps. The wavelength of LED light source is the key. In fact, the wavelengths of light required by various plants are not the same, and various plants have specific wavelengths of light that are suitable for them. In recent years, international companies such as Philips, Osram, Mitsubishi, and Panasonic have actively invested in gardening LED lighting and focused their development on light formulations. Because gardening LED lighting is deeply influenced by different characteristics of different places, it has a high correlation with local climate and consumption demand. Therefore, how to develop light formula suitable for different regions is the goal of garden LED lighting. It is suggested in the literature that the effect of low-power LED combined light source on the proliferation, bract formation and hair root of oriental hybrid lily slices is compared with the traditional fluorescent tube as the control group, and the literature also uses RGB for different plants (red, green and blue). ) - LED light with different wavelengths, and explore the effects of different formulations on plant growth at different ratios of red and blue light. It is obvious that the establishment and verification of the light formula database is the key to the future development of plant plants and economic scale.

Plant factory environmental control and monitoring man-machine system construction: plant factory to build four major points including construction, equipment, environmental control, growth materials, and accurate environmental control and friendly monitoring man-machine system, is it possible to improve the establishment of light formula data The key to the library and large-scale planting. Therefore, there are many literatures that propose different environmental control and monitoring human-machine system architectures. With the maturity and popularity of wireless sensing and communication network technologies, the plant factory environmental control and monitoring human-machine systems proposed in recent years are based on wireless. Sensing, communication network to build. The wireless network protocol works with different terminal devices (PC, laptop, smart phone and tablet) to provide a lot of convenience, flexibility, low cost, and convenient time recording. Managers do not need to go to the plant every day. Wireless communication vehicles such as mobile phones can also instantly monitor the growth environment of plants and do emergency treatment.

High-performance drive architecture to improve drive circuit efficiency: If you need to use a single-group power converter to drive RGB LEDs if you need to further reduce costs, because the red, green, and blue LEDs have different forward-flow voltage drops, The power converter must change the output voltage for the turn-on voltage requirements of each of the light-emitting diodes in order to reduce the power loss on the current-stabilizing circuit. This technique is called dynamic voltage regulation technology. It has been proposed in the literature to dynamically adjust the output voltage of the power converter by feedback the voltage on each LED string current stabilizing circuit to further reduce the power loss on the current stabilizing circuit. In terms of the driver circuit hardware structure, the architecture of the red, green, and blue LED driver circuits is more complicated than that of the white LED driver circuit, mainly because the driving characteristics required for red, green, and blue light are not completely the same. It is proposed in the literature that three sets of series resonant converters respectively drive the red, green and blue light-emitting diodes with different forward voltage drops. The drive circuit can achieve relatively high efficiency due to zero voltage switching function. Three sets of converters; there are literatures that use multiple sets of output flyback converters to drive red, green, and blue LED loads, and the transformers need to be specially designed; there are literature on how to use magnetic amplifiers (Magnetic Amplifier) to make multiple sets The output winding is suitable for driving red, green and blue LED loads. A literature proposes an energy-saving driving method for large-area LED panels. With the low-cost modification of the existing hardware architecture, multi-stage PWM can be used. The MPWM) modulation drive method is implemented on the LED drive system; a floating buck dimmable LED driver and solid-state lighting application have been proposed in the literature, and an adaptive timing difference compensation mechanism is proposed to adjust the cut-off time of the lower switch. Enables high-accuracy average current, fast settling time, and high speed over a wide input voltage range and numerous LED loads Operating frequency; also a literature proposes an optimal trajectory control PWM dimming strategy for multi-string constant current LLC resonant LED driver, LED brightness can be controlled by PWM dimming signal.

The main object of the present invention is to provide a light formula verification platform for plant factories, which can operate with high efficiency to mix illumination light with specific color light, and can overcome illumination due to LED aging by a light wavelength feedback compensation mechanism. The problem of wavelength shift.

To achieve the above objectives, a light formula verification platform for plant plants has been proposed which has:

a power converter having two input terminals coupled to the positive and negative terminals of an input voltage, a voltage output terminal for providing a variable output voltage, and a red optical synchronization signal output terminal for providing a red light synchronization signal, a green light sync signal output terminal for providing a green light sync signal and a blue light sync signal output terminal for providing a blue light sync signal, wherein the variable output voltage presents a first when the red light sync signal is at an active potential a voltage that exhibits a second voltage when the green light synchronization signal or the blue light synchronization signal is at an active potential;

An RGB LED circuit having a string of red LEDs and a first switch connected in series with the string of red LEDs, a string of green LEDs, and a second switch in series with the string of green LEDs, a string of blue LEDs And a third switch connected in series with the string of blue LEDs, and a certain current unit, wherein the string of red LEDs, the string of green LEDs, and the string of blue LEDs are all powered by the variable output voltage; The open relationship is controlled by a first driving signal, the second open relationship is controlled by a second driving signal, and the third open relationship is controlled by a third driving signal; the first switch, the second switch, and the third The switch is coupled to a reference ground via the constant current unit; and the constant current unit is configured to provide a current, wherein a first average current flowing through one of the red LEDs is equal to one of the first driving signals Multiplying the constant current; a second average current flowing through one of the string of green LEDs is equal to one of the second drive signals being multiplied by the constant current; and a third average current flowing through one of the string of blue LEDs is equal to One of the third drive signals is multiplied by the constant current;

a light sensor for sensing the red light LED, the green LED, and the output light of the blue LED to provide a red light sensing signal, a green light sensing signal, and a blue light Sense signal;

a control unit storing a firmware program for executing a driving signal generating program for sequentially generating the first driving signal, the second driving signal, and the third driving signal, wherein the driving signal generating program includes a proportional-integral-differential operation and the driving signal generating program performs the proportional-integral according to a first mode when the first average current, the second average current, and the third average current are both lower than a threshold current a differential operation, wherein the proportional-integral-derivative operation is performed in a second mode when at least one of the first average current, the second average current, and the third average current is higher than the threshold current ;

Wherein, when the control unit is operated in the first mode, the driving signal generating program sequentially performs the proportional-integral-derivative operation according to a preset red light reference value and the red light sensing signal. The preset green light reference value and the green light sensing signal perform the proportional-integral-differential operation, and perform the proportional-integral-derivative operation according to a preset blue light reference value and the blue light sensing signal; when the control When the unit is operated in the second mode, the driving signal generating program is a ratio of the threshold current to the first average current, a ratio of the threshold current to the second average current, and the threshold current and the Finding a minimum ratio in the ratio of the third average current, multiplying the minimum ratio by the preset red light reference value to obtain a corrected red light reference value, and multiplying the minimum ratio by the preset green light reference And obtaining a corrected green light reference value, multiplying the minimum ratio by the preset blue light reference value to obtain a corrected blue light reference value, and sequentially correcting the red light reference value and the red light sensing Signal to make the ratio An integral-differential operation, performing the proportional-integral-derivative operation according to the corrected green light reference value and the green light sensing signal, and performing the proportional-integral according to the corrected blue light reference value and the blue light sensing signal Differential operation.

In one embodiment, the light recipe verification platform for the plant factory further has a monitoring information processing device, and the monitoring information processing device communicates with the control unit in a wired manner or in a wireless manner.

In one embodiment, the power converter is an LLC resonant power converter.

In one embodiment, the drive signal generation program includes an analog to digital conversion operation.

In an embodiment, the drive signal generation program further includes a low pass filtering operation.

In an embodiment, the control unit includes a driving unit to provide the first driving signal, the second driving signal, and the third driving signal.

The detailed description of the drawings and the preferred embodiments are set forth in the accompanying drawings.

Please refer to FIG. 1 , which illustrates an embodiment of a light formula verification platform for a plant factory of the present invention. As shown in FIG. 1, the light recipe verification platform has a power converter 100, an RGB LED circuit 110, a light sensor 120, and a control unit 130.

The power converter 100 can be an LLC resonant power converter having two input terminals A, B coupled to the positive and negative terminals of an input voltage V _IN and a voltage output terminal C to provide a variable output voltage V _O a red sync signal output terminal for providing a red sync signal S _R , a green sync signal output terminal for providing a green sync signal S _G , and a blue sync signal output terminal for providing a blue sync signal S _B Wherein the variable output voltage V _O exhibits a first voltage (eg, but not limited to 48V) when the red sync signal S _{R is} at an active potential, and the green sync signal S _G or the blue sync signal S _{B is} in a role The potential exhibits a second voltage (such as, but not limited to, 72V).

The RGB LED circuit 110 has a string of red LEDs and a first switch connected in series with the string of red LEDs, a string of green LEDs and a second switch connected in series with the string of green LEDs, and a string of blue LEDs and a third switch connected in series with the string of blue LEDs, and a certain current unit, wherein the string of red LEDs, the string of green LEDs, and the string of blue LEDs are all powered by the variable output voltage V _O ; An open relationship is controlled by a first drive signal V _R , the second open relationship is controlled by a second drive signal V _G , the third open relationship is controlled by a third drive signal V _B ; the first switch, the first The second switch and the third switch are both coupled to a reference ground via the constant current unit; and the constant current unit is configured to provide a certain current I _S , wherein a first average current flowing through one of the red LEDs a duty ratio equal to the first drive signal V _R multiplied by the constant current I _S ; a duty ratio of the second average current flowing through one of the string of green LEDs equal to the second drive signal V _G multiplied by the constant current I _S And a third average current flowing through the string of blue LEDs is equal to the duty ratio of the third drive signal V _B multiplied by the constant current I _S .

The light sensor 120 is configured to sense the string of red LEDs, the string of green LEDs, and the output light of the string of blue LEDs to provide a red light sensing signal V _RS , a green light sensing signal V _GS , And a blue light sensing signal _VBS .

The control unit 130 stores a firmware program for executing a driving signal generating program to sequentially generate the first driving signal V _R , the second driving signal V _G , and the third driving signal V _B . The driving signal generating program includes a proportional-integral-derivative operation and the driving signal generating program is in a first mode when the first average current, the second average current, and the third average current are both lower than a threshold current Performing the proportional-integral-differential operation, performing the ratio according to a second mode when at least one of the first average current, the second average current, and the third average current is higher than the threshold current - Integral - differential operation.

In the first mode, the driving signal generating program sequentially performs the proportional-integral-derivative operation according to a preset red light reference value and the red light sensing signal V _RS according to a preset green light. the reference value and the green sense signal V _GS for the proportional - integral - differential operator, and blue light according to a predetermined reference value and the blue sensing signal V _BS for the proportional - integral - differential operator.

In the second mode, the driving signal generating program is a ratio of the threshold current to the first average current, a ratio of the threshold current to the second average current, and the threshold current and the third Find a minimum ratio in the ratio of the average currents, multiply the minimum ratio by the preset red reference value to obtain a corrected red reference value, and multiply the minimum ratio by the preset green reference value. Obtaining a corrected green light reference value, multiplying the minimum ratio by the preset blue light reference value to obtain a corrected blue light reference value, and sequentially correcting the red light reference value and the red light sensing signal V _{The RS} performs the proportional-integral-differential operation, performs the proportional-integral-differential operation according to the corrected green light reference value and the green light sensing signal _VGS , and the corrected blue reference value and the blue light sensing signal. The _VBS performs the proportional-integral-derivative operation.

The functional blocks of the control unit 130 include an analog to digital conversion unit 131, a low pass filtering unit 132, a mode decision unit 133, a proportional-integral-derivative operation unit 134, and a drive unit 135.

The analog-to-digital conversion unit 131 is configured to perform an analog-to-digital conversion operation; the low-pass filtering unit 132 is configured to perform a low-pass filtering operation on the analog-to-digital conversion unit 131; the mode determining unit 133 is configured to The threshold current is compared with the first average current, the second average current, and the third average current to determine the first mode or the second mode; the proportional-integral-derivative operation unit 134 is configured to The first mode or the second mode adjusts a duty cycle of the first driving signal V _R , the second driving signal V _G , and the third driving signal V _B ; and the driving unit 135 is configured to provide the The first driving signal V _R , the second driving signal V _G , and the third driving signal V _B .

In addition, the control unit 130 determines the first driving signal V _R and the second driving signal V _G by the red optical synchronization signal S _R , the green optical synchronization signal S _G , and the blue synchronization signal S _B provided by the power converter 100. And the action time of the third drive signal V _B .

In addition, the control unit 130 can communicate with a computer 200 or a mobile phone 210 by wired (eg, RS232) or wireless (eg, Bluetooth) to accept external monitoring.

Accordingly, the present invention provides a fixed shade formulation for a particular plant growth.

The principle of the invention will be described in detail below.

1. Effect of light wavelength on plant physiology

The color temperature and lumen of the artificial light source are seen by the eyes of the creature, and the plant's demand for light is the photosynthesis, which is determined by the radiation value without looking at the color temperature and lumens. Plant physiology knows that different plants have different perceptions of different spectra, and the effects of different light wavelength ranges on plant physiology are organized:

280~315nm: This wavelength range is already ultraviolet light. It has direct repressive growth for all kinds of animals, plants and even fungi, and has little effect on morphology and physiological processes.

315~400nm: This wavelength range belongs to far ultraviolet light. Although there is no ultraviolet damage to plants, it has no direct effect on plant growth, and chlorophyll absorption is less, affecting photoperiod effect and preventing stem elongation.

400~520nm (blue light): This kind of wavelength can directly promote the development of roots and stems of plants. It has the largest absorption ratio of chlorophyll and carotenoids and the greatest impact on photosynthesis.

520~610nm (green light): Green plants will be repellent to green light, and the absorption rate of green pigment is not high.

610~720nm (red light): The chlorophyll absorption rate of red light on plants is not high, but this wavelength has a significant effect on photosynthesis and plant growth rate.

720~1000nm: These wavelengths belong to the infrared wavelength. The absorption rate of plants is low, but it can directly stimulate plant cells, which will affect the flowering and seed germination time.

>1000nm: The wavelength near the laser light has been converted into heat.

From the above data on the physiological effects of different light wavelengths, it can be seen that the effects of different wavelengths of light on plant photosynthesis are different. Among the light required for photosynthesis in plants, 400~520nm (blue) light and 610~720nm (red) light contribute the most to photosynthesis, while 520~610nm (green) light has a very good effect on promoting plant growth. low. That is to say, the spectra of 400~520nm (blue light) and 610~720nm (red light) have direct growth effects on plants, so the plant growth lights under the academic concept are mostly in the form of red and blue, all blue and all red. To provide red and blue wavelengths of light to cover the wavelength range required for photosynthesis in plants. Generally, the white light LED has two peaks in the blue region of 445 nm and the yellow-green region of 550 nm, while the red light of 610-720 nm required by plants covers less, so it is impossible to provide photosynthesis for plants. Light efficiency, which is why the growth rate and yield of plants are not as good as those of outdoor plants under the illumination of white LEDs.

The spectral ratio of the red and blue lights of the plant growth lamp is generally between 5:1 and 10:1, and the ratio of 7 to 9:1 is usually selected, and the ratio of the brightness of the LED lamp to the mixed light is only required for the proportional distribution. The number of lights is based on the light mixing. When using LED plant growth lamps for planting, the height of the leaves is generally about 30-50 cm. In the middle, different light intensities are required depending on the type of plant to be planted. The height adjustment is generally regarded as the most convenient way to adjust the brightness. In the plant kingdom, green plants dominate. In all photosynthetic oxygenated plants, the chlorophyll in the leaves has two absorption peaks for sunlight, which are the blue region near 440 nm and the red region near 680 nm. Green light between 500-600 nm absorbs very little, and most of the green light is reflected, so most of the plants we see are green. With the maturity of LED lighting technology, LED light sources and wavelength-adjustable technologies have gradually entered the field of biological lighting. In addition to saving energy compared to conventional light sources, LEDs also greatly reduce the cost of lighting in the biological field. In addition, LED can also control the growth rate of plants, prolong the flowering period of flower plants, and make economic crops free from seasonal restrictions and accelerate the results. For example, plants can perform 16 hours of photosynthesis per day, but natural light exposure is very limited, making plants grow slowly. If you use LED lights to continuously replenish the plants, the ripening period of the vegetables can be shortened.

2. Light formula verification platform system

The optical formula verification system architecture shown in Figure 1 is mainly composed of high power factor, high efficiency, low cost power converter, high power RGB-LED string, PC or smart phone (including wireless communication system setting and monitoring). Man-machine interface), and a controller that can perform wavelength feedback compensation. The power converter can be an LLC resonant converter with power factor correction to increase power factor and significantly reduce switching loss and conduction losses. Moreover, because the red, blue, and green LED strings have different conduction voltages, if the same voltage is used to supply the parallel RGB LED strings, in addition to damaging the LEDs, a large amount of power consumption is generated in the steady current control circuit, so the present invention proposes A dynamic bus voltage regulation mechanism is matched with the field color sequential driving method, and the digital PWM regulation and the use of a digital variable resistor (MCP4651) are used to accurately control the output voltage of the LLC resonant converter to make it R, G. The B sequence provides the required voltage value.

In order to find out and verify which illumination light is most helpful for the growth of a particular plant, the control unit can be controlled by wired or wireless communication through the friendly human-machine interface of the present invention, and the desired color light can be easily obtained to verify whether the color light is suitable. Specific plant growth. In addition, in order to solve the aging light decay caused by the LED lighting time and the junction temperature rise, the set light formula (wavelength, color temperature (CCT), and brightness) changes, which affects the correctness of the verification light formula. The invention sets the output optical feedback control and photoelectric signal conversion mechanism. The light recipe setting and the wavelength feedback compensation control of the present invention utilizes a photo sensor (photodiode) to sense the mixed output light amount (related to the wavelength) of the RGB three primary color LEDs, and the analog digital number in the microcontroller (MCU) After the converter (ADC) is digitized, the PWM photocurrent is converted by a low-pass filter and the high frequency chopping is filtered to generate a voltage signal suitable for feedback control. Then, the optical wavelength compensation algorithm is used to calculate the correction amount of the new tristimulus values reference value required for the LED light decay caused by aging, and finally the PID controller calculates the RGB-LED string PWM drive current. The required duty cycle is such that the LED light output in the aging condition still satisfies the preset light recipe value. The proposed light formula setting and verification system has the advantages of simple structure, high energy efficiency, easy setting of color light, and automatic light decay compensation. With a single power converter and RGB timing output different voltages to drive RGB LED strings, the drive system architecture is simple, the control complexity is low, and the implementation cost is low. The components of the system are described below.

3. Optical wavelength compensation control method

As shown in the system architecture of Figure 1, the light recipe setting and wavelength feedback compensation controller of the system utilizes a light sensor (photodiode) to sense the output light quantity (related to the wavelength) of the three primary color LEDs, via a microcontroller ( The analog-to-digital converter (ADC) in MCU2) is digitized and then low-pass filtered to minimize the sensing error, and then the optical wavelength compensation algorithm (WCA) is used to calculate the LED light attenuation caused by aging. The correction compensation amount of the new three primary color stimulation reference values is finally calculated by the PID controller to calculate the duty cycle required for regulating the RGB-LED string PWM drive current, so that the LED light output under the aging condition still conforms to the preset light recipe value. . 2 is a block diagram of a light wavelength direct feedback control system proposed by the present invention. In the implementation of this feedback control, many issues such as the placement of the photosensor (photodiode), the sampling of the output light, the effect of the drive current on the wavelength of the light, and the stability of the control system when the dimming and color changes are required must be paid attention to. In other words, it is necessary to accurately process the conversion of light and electric signals. The light sensor must be able to accurately sample the mixed light containing the light emitted by the individual RGB-LEDs, otherwise the accuracy of the wavelength of the mixed light will be affected. Generally, the noise of the feedback circuit, temperature drift, optical diode tolerance, and analog-to-digital converter (ADC) quantization error will cause optical sensing error, and 2.5% of the light sensing error can make people The eye notices the offset of the color point; in addition, the resolution of the duty ratio of the PWM dimming also affects the accuracy of the light mixing wavelength and the color error Duv, where the Duv is on the CIE 1960 UCS plane, the color point ( u , v ) the amount of chromatic aberration deviating from the reference value ( u _r , v _r ), which can be defined as

(1)

In the case of large dimming range requirements, at least 12-bit dimming resolution is required to avoid appreciable chromatic aberration, otherwise the color and brightness are unstable, and the PWM dimming frequency should be properly selected to avoid flicker. (flicker) phenomenon. In order to accurately control the light formula, an effective control method and controller are needed to regulate the light output of the RGB-LED, and to correct the problem of the offset of the output light formulation caused by the temperature rise and long-time illumination aging of the LED. The controller design of Figure 2 can be carried out by including the transfer function of the optical and electrical system parts. Because the three LEDs are used to mix the desired light recipe, it is a multiple input multiple output (MIMO) system and is required in the system model. Processing optical and electrical signal conversion. The transfer function G _LED (s) and G _pd (s) of the RGB-LED lamp and the light sensing system are derived using a model of light and electricity combination.

3-1 RGB-LED Lamp transfer function

The present invention utilizes a three primary color stimulus value feedback control method for calculating a mixed light output spectrum to maintain and verify a desired light recipe during plant growth, which is a light sensor integrated with a light diode and a filter to detect mixed light. After the three primary color stimulation values, compared with the preset light formula (the three primary color stimulation reference values) input through the human-machine interface, the obtained optical wavelength error amount is calculated by the PID controller, and then the PWM signal for updating the LED driving current is generated accordingly. . In Figure 2, the three primary color stimulus values (V _X , V _Y , V _Z ) of the output mixed light are a function of the mixed light spectrum P(l, s), representing the color and brightness of the light seen by the human eye, ( V _X , V _Y , V _Z ) are controlled target parameters, and (V _Xref , V _Yref , V _Zref ) is the system reference value calculated by the converted light formula input value input by the human-machine interface. The optical coupling between the RGB-LED lamp and the photodiode can be modeled using parameters such as trichromatic stimulus values, optical flux, and spectral power density (SPD). Since the photocurrent output of the photodiode is related to the radiated power (W/nm) of each wavelength of the RGB-LED mixed light output, only the SPD can directly provide the RGB-LED output light and the photodiode. The coupling relationship between the bodies. Therefore, as shown in FIG. 3, the optical output current can be obtained after filtering and integrating the spectral power density of the RGB-LED light output in the spectral response region of the photodiode. The general LED response time is about 100ns and its dynamics are negligible, so it can be assumed that the RGB-LED light output only changes with the PWM wavelength; in addition, the LED characteristics change with time and temperature faster than the dynamic response of the light engine's subsystem. A lot, so this change can be ignored and the RGB-LED lights are modeled in a linear, time-invariant model. Assuming that the light can be perfectly mixed, the SPD p _i (l) of the RGB-LED lamp can be expressed as visible light in the wavelength range of 380 nm to 730 nm.

(2)

A portion of the RGB-LED light is coupled to the photodiode as shown by C _XYZ (s) in FIG. Since the response speed of the photodiode is fast, there is a photocurrent output at the moment of illumination. The output current of the three photodiodes can be expressed as

(3)

Where p _X (l), p _Y (l), p _Z (l) are the spectral responses of the photodiode, and C _Xi , C _Yi , and C _Zi are the coupling coefficients of the RGB-LED light coupling to the photodiode portion. (3) can be rewritten into a matrix type

(4)

Where k _ij ( i =1~3, j =1~3) is the DC gain, defined as , , .

k ₂₁ to k ₃₃ have similar definitions. The transfer function between the photocurrent and the RGB-LED forward current can be obtained from the equation (4), which can be expressed as

(5)

The low pass filter is a first order system and can be expressed as

(6)

Where R _cx , R _cy , R _cz are current sense resistors, and t _x , t _y , t _z are time constants, t _i = R _ci C , i = x , y , z , C are filter capacitors. Then the transfer function between the three primary color stimulus values (V _XYZ ) and the RGB-LED forward current can be obtained as

(7)

among them . The coefficients K _dc are DC gains, which can be obtained experimentally using equation (8).

(8)

3-2 Wavelength Compensation Control Algorithm Generally, the output luminosity of LED will decrease with aging. The traditional control method is to maintain the total output luminosity of a certain value after mixing, and increase the average driving current of each primary color LED as the aging increases. This will result in an increase in the temperature rise of the LED junction and the average drive current reaching the saturation of its upper limit and the risk of no further regulation. When the average drive current of one or more primary color LEDs reaches their saturation value, the feedback system will become open loop and the light output of its primary color LEDs can no longer be adjusted. When the aging causes the LED light to become more severe, the color point of the total output light after the light mixing is deviated from the original preset value. In order to maintain the accuracy of the light formula, the present invention proposes a new dynamic tristimulus reference values (TRV) modulation optical wavelength compensation control method to prevent LED drive current saturation, as shown in FIG. . The proposed method has two modes of operation. When the average driving current of the three primary color LEDs is lower than a threshold current value I _th , the duty ratio update ratio (DUR) unit according to the corresponding duty ratio D _i (= I _avgi / I _pk ) < D _Crit (= I _th / I _pk ) relationship (where i = X, Y, Z, I _avgi and I _pk are the LED average drive current and maximum current, D _crit is the threshold duty ratio), the switch S _{DUR is} cut off, the system Operates in mode I, DUR=1, This mode controls the total output light of the three primary color LEDs in a general PID control mode, so that the color point ( x , y , z ) is maintained at the desired set value, and the color point value can be expressed as

(9)

Where X _ref , Y _ref , Z _ref are the three primary color stimulus reference values corresponding to the light output.

When the average driving current in the three primary color LEDs is higher than the threshold current value ( D _{i 3} D _crit ), the DUR unit turns on the switch S _DUR and the system operates in mode II. There are two cases in this mode: Case 1) If only one of the three primary colors has an average driving current higher than the threshold current, the excitation reference value of the LED will be reduced so that the average driving current can be maintained within the threshold current value; Case 2) If the average driving current of two or three LEDs in the three primary colors is higher than the threshold current value, the stimulus reference value of the LED with the maximum light output attenuation and the average driving current exceeding the threshold current value needs to be reduced, so that The average drive current can be maintained within the threshold current value, and the other two primary color stimulus reference values need to be adjusted proportionally to maintain the mixed color point at the desired value. Because the light output of the PWM-driven LED is proportional to its duty cycle, when the LED ages, it is assumed that the excitation value X generated by the red LED loop increases so that its average drive current ( I _avg-R ) increases beyond the threshold current ( I _Th ), in order for I _avg-R to return to I _th , the DUR unit calculates a new X stimulus reference value For correction, and to maintain the total mixed color point and wavelength, the stimulus reference values of Y and Z also need to be adjusted in proportion, so it can be expressed as

(10)

And the corrected color point value can be expressed as

(11)

It can be seen that the color point value of the total output light is still maintained as before the correction. On the other hand, when more than two currents exceed the threshold current value, the DUR unit will find the minimum duty cycle update ratio, and then adjust the three primary color stimulus reference values based on this ratio (DUR). This mechanism can be expressed mathematically. for

(12)

5(a)-5(b) are block diagrams showing the operation mode of the new dynamic three-primary color stimulus reference value modulation optical wavelength compensation control method, and FIG. 6 is a flow chart of a control method adopted by the present invention. After the system is initialized, the present invention senses the LED current and the output light amount, uses the PID controller to regulate the light recipe (color point) of the RGB LED, and adds a periodic PWM duty cycle check point to periodically check the aging of the LED, when D _i 3 D _crit , the system enters mode II operation, and then calculates to find the minimum duty cycle update ratio ( And updating the tristimulus reference value according to (10) or (12), and then updating D _crit using equation (13), returning to the PID controller to adjust the wavelength according to the new tristimulus reference value. Generally, D _{crit is} set to a fixed value, but since the aging speed of the RGB LED is different, it is not easy to find a D _crit value suitable for the three LEDs at the same time. If the D _crit value is set to be much less than 1, the system will always operate in mode II, and the total light output of the LED will be reduced. On the other hand, if the D _crit value is set to be close to 1, the value of the PWM will be soon. A 1 (saturation current value) is reached, making the color point uncontrollable. Therefore, the control method of the present invention calculates a new one based on the change in the duty ratio of each LED for each manipulation. Value to replace the fixed D _crit setting method, Can be expressed as

(13)

In order to increase the controllability, (13) includes a margin value a (31), which can take into account the aging rate variation between two periodic checkpoints, so that the control algorithm can adaptively learn The aging rate of individual RGB-LEDs, and the individual D _crit values can be accurately set.

3-4 RGB LED Dynamic supply voltage control and digital dimming control program

As shown in Fig. 7(a), in order to achieve the purpose of driving the RGB LED by the field color sequential method, the digital control must generate the output voltage commands of 48V and 72V according to the LED forward voltage characteristics of different colors, and provide the field. The color sequence synchronization signals (Seq_R, Seq_G, Seq_B) control the steady current dimming circuit synchronously. Figure 7 (b) is a system program control flow chart, which first determines whether the system is in the LED conduction interval. The planned R, G, and B LED on-times are all 5.22 ms. In each 1/3 conduction interval, there is a conversion time of 0.33 ms for each RGB LED to be non-conducting. In this interval, the converter output voltage is changed, so RGB turns on. The primary frequency is 60 Hz. After determining the timer time, if it is the LED conduction interval, it is judged that the red or green or blue LED is turned on at this time, and the field color sequence command is sent to the steady current dimming circuit. In the voltage conversion interval, the output voltage command is transmitted to the digital variable resistor through I ² C to change the feedback voltage to dynamically adjust the output supply voltage.

FIG. 8 is a schematic diagram of a digital dimming PWM control process adopted by the present invention, which uses a computer-side human interface created by LabVIEW or an app of a smart phone to send four groups of 12 PWM dimming commands (three groups of R per region). , G, B component dimming signal), and synchronously control the field color sequence control signal sent by the microprocessor of the LLC resonant converter to complete the dimming control. In order to avoid unnecessary power loss caused by LEDs with different forward-pass voltages at the same time, when switching LEDs with different colors, a transition interval (0.33ms) is added in the middle, and no LED is turned on in this interval, and the operation is performed. The mode change changes the output voltage to the desired command voltage value. The clock of the digital dimming controller used is the synchronous frequency of the digital driving power supply, and the preset dimming control signal is a PWM signal with an 8-bit resolution and a frequency of 180 Hz. The transition interval is set to 0.33 ms and a sawtooth time is 5.22 ms, so the output R, G, B switching frequency is 180 Hz. The dimming signal is generated by the LabVIEW human-machine control panel or the smart phone app to send 12 sets of 8-bit PWM dimming commands (0~255) through the RS232 serial transmission interface, and will be written by the serial transmission receiving program. The received dimming commands are sequentially stored in the dimming command vector, as shown in FIG. Since the R, G, and B LEDs need to be time-divisionally enabled, the digital color control synchronization control signals (Seq_R, Seq_G, and Seq_B) are sent by the digital power control core to enable the output of each set of sawtooth waves and comparators. When the comparator receives the enable signal, it compares the dimming command vector values (CMD_R, CMD_G, CMD_B) with the counter count values (SAW_R, SAW_G, SAW_B). When the dimming command vector value is greater than the count value output, "High potential", otherwise it is "low potential". In this way, a total of 12 sets of PWM dimming control signals are generated in four regions, and the timing chart is shown in FIG.

The disclosure of the present invention is a preferred embodiment. Any change or modification of the present invention originating from the technical idea of the present invention and being easily inferred by those skilled in the art will not deviate from the scope of patent rights of the present invention.

In summary, this case, regardless of its purpose, means and efficacy, is showing its technical characteristics that are different from the conventional ones, and its first invention is practical and practical, and it is also in compliance with the patent requirements of the invention. I will be granted a patent at an early date.

100‧‧‧Power Converter
110‧‧‧RGB LED circuit
120‧‧‧Light sensor
130‧‧‧Control unit
131‧‧‧ analog to digital conversion unit
132‧‧‧Low Pass Filter Unit
133‧‧‧ mode decision unit
134‧‧‧Proportional-Integral-Derivative Unit
135‧‧‧ drive unit
200‧‧‧ computer
210‧‧‧Mobile phones

1 illustrates an embodiment of a light formulation verification platform for a plant factory of the present invention. 2 is a block diagram of a light wavelength direct feedback control system proposed by the present invention. FIG. 3 illustrates the coupling relationship between the RGB LED and the photodiode. 4 is a block diagram of a light wavelength compensation control taken by the present invention. Figures 5(a)-5(b) are block diagrams showing two modes of operation proposed by the present invention. Figure 6 is a flow chart of a control method proposed by the present invention. Fig. 7(a) shows the waveforms of the variable output voltage and the three sync signals of the present invention. Figure 7(b) is a flow chart showing one of the control outputs for generating the variable output voltage and the three sync signals of Figure 7(a). FIG. 8 illustrates a digital dimming PWM control flow proposed by the present invention. FIG. 9 is a timing diagram of a control signal generated by the digital dimming PWM control flow of FIG. 8.

100‧‧‧Power Converter

110‧‧‧RGB LED circuit

120‧‧‧Light sensor

130‧‧‧Control unit

131‧‧‧ analog to digital conversion unit

132‧‧‧Low Pass Filter Unit

133‧‧‧ mode decision unit

134‧‧‧Proportional-Integral-Derivative Unit

135‧‧‧ drive unit

200‧‧‧ computer

210‧‧‧Mobile phones

Claims (6)

A light recipe verification platform for a plant factory, comprising: a power converter having two inputs for coupling with positive and negative ends of an input voltage, and a voltage output for providing a variable output voltage, a red light a sync signal output terminal for providing a red light sync signal, a green light sync signal output terminal for providing a green light sync signal, and a blue light sync signal output terminal for providing a blue light sync signal, wherein the variable output voltage is The red light synchronization signal exhibits a first voltage when it is at an active potential, and presents a second voltage when the green light synchronization signal or the blue light synchronization signal is at an active potential; an RGB LED circuit having a string of red LEDs and The string of red LEDs is connected in series with a first switch, a string of green LEDs, and a second switch connected in series with the string of green LEDs, a string of blue LEDs, and a third switch connected in series with the string of blue LEDs And a certain current unit, wherein the string of red LEDs, the string of green LEDs, and the string of blue LEDs are all powered by the variable output voltage; the first open relationship is controlled by a first driving signal, The second open relationship is controlled by a second driving signal, and the third open relationship is controlled by a third driving signal; the first switch, the second switch, and the third switch are all coupled to a reference via the constant current unit And the constant current unit is configured to provide a current, wherein a first average current flowing through one of the red LEDs is equal to a duty ratio of the first driving signal multiplied by the constant current; flowing through the green a second average current of one of the light LEDs is equal to a duty ratio of the second drive signal multiplied by the constant current; and a third average current flowing through one of the string of blue LEDs is equal to a duty ratio of the third drive signal multiplied by the a current sensor; a light sensor for sensing the red light LED, the green LED, and the output light of the blue LED to provide a red light sensing signal, a green light sensing signal, And a blue light sensing signal; and a control unit storing a firmware program for executing a driving signal generating program to sequentially generate the first driving signal, the second driving signal, and the third driving signal, Among them, the drive letter The generating program includes a proportional-integral-differential operation and the driving signal generating program performs the first mode when the first average current, the second average current, and the third average current are both lower than a threshold current a proportional-integral-differential operation, wherein the proportional-integral is performed according to a second mode when at least one of the first average current, the second average current, and the third average current is higher than the threshold current a differential operation; wherein, when the control unit is operated in the first mode, the driving signal generating program sequentially performs the proportional-integral-derivative according to a preset red light reference value and the red light sensing signal Computing, performing the proportional-integral-derivative operation according to a preset green light reference value and the green light sensing signal, and performing the proportional-integral-derivative operation according to a preset blue light reference value and the blue light sensing signal When the control unit operates in the second mode, the driving signal generating program is a ratio of the threshold current to the first average current, the ratio of the threshold current to the second average current And finding a minimum ratio between the threshold current and the third average current, multiplying the minimum ratio by the preset red reference value to obtain a corrected red reference value, multiplying the minimum ratio Upsetting the preset green light reference value to obtain a corrected green light reference value, multiplying the minimum ratio value by the preset blue light reference value to obtain a corrected blue light reference value, and sequentially correcting the red light The reference value and the red light sensing signal perform the proportional-integral-differential operation, perform the proportional-integral-derivative operation according to the corrected green light reference value and the green light sensing signal, and the corrected blue reference value The proportional-integral-derivative operation is performed with the blue light sensing signal. The light formula verification platform for a plant factory according to claim 1, further comprising a monitoring information processing device, wherein the monitoring information processing device communicates with the control unit in a wired manner or in a wireless manner. . The light formula verification platform for a plant factory according to claim 1, wherein the power converter is an LLC resonant power converter. The light formula verification platform for a plant factory according to claim 1, wherein the driving signal generating program comprises an analog to digital conversion operation. The light formula verification platform for a plant factory according to claim 4, wherein the driving signal generating program further comprises a low pass filtering operation. The light formula verification platform for a plant factory according to claim 1, wherein the control unit comprises a driving unit to provide the first driving signal, the second driving signal, and the third driving signal.