| With the emergence of LED as the fourth generation lighting source,the trend has been to use LED as an artificial light source in various industries.Nowadays,indoor growing is developing rapidly,and LED is an artificial supplemental light source,which has become a mature method to improve the yield as well as the quality of planting plants.Generally,the output of LED plant lamps is continuous light,but some studies have shown that pulse light is helpful to promote plant growth and save energy.At present,the common LED pulse optical driver is usually driven by switching power supply,using multiple switches to control the LED current,but more switches will consume a certain amount of energy,affect the efficiency,and need multiple signal sources to control the switches.Therefore,this paper designs a high-efficiency led plant lamp driving power supply with controllable pulse energy using buck single tube circuit,which can independently adjust the pulse frequency,pulse duty cycle and instantaneous light intensity of LED output pulse light.The plant lamp with controllable pulse energy designed in this paper uses a single-tube Buck circuit as the LED driving circuit,and the LED output pulse light is achieved by controlling the power-up and shutdown of the Buck circuit.However,the output pulse light of LED controlled by a single-tube Buck circuit has the problem of limited adjustable range of pulse light frequency,which is due to the rise time of the output current when the Buck circuit id powered up and the fall time when it is turned off,resulting in the current in the bright area of the pulse cannot be stable and the dark area cannot be reduced to 0 when the pulse light frequency is too high.In order to improve the adjustable pulse frequency range and reduce the ripple,the control mode(DEMPT-PID)of dual-edge modulation pulse sequence(DEMPT)combined with PID is proposed,which can suppress overshoot on the basis of shortening the rise time of output current.At the same time,the experimental prototype is built to verify the feasibility of DEMPT-PID.The second chapter mainly analyzes the reason for limiting the adjustable range of output pulse light frequency when a single Buck circuit is used to output pulse light.Due to the problems of rising time and fall time when the Buck circuit powers up and shuts down,the pulse optical frequency cannot be adjusted to a high frequency.Therefore,the singletube Buck circuit is modeled to analyze the influence of filter inductance L and output filter capacitor C on the ideal rise time and ideal fall time,so that the circuit component selection is determined.Finally,according to the equivalent value of the load LED,the appropriate filter element parameters are selected to ensure the adjustable frequency of the pulse light.In the third chapter,the working principle and experimental verification of the DEMPTPID control mode are introduced.DEMPT-PID control is based on the use of DEMPT control at the beginning of the dimming cycle.When DEMPT completes the output current rise phase and overshoot suppression phase,it switches to PID control.The high dynamic performance of DEMPT is used to shorten the rise time of circuit output current.At the same time,due to the large oscillation in the steady-state of DEMPT and the inaccurate current regulation,the DEMPT mode is switched to PID mode to eliminate the low-frequency oscillation in the steady-state of DEMPT control and improve the accuracy of output current regulation.In order to ensure that the rise time of the output current meets the requirements of the dimming frequency,the parameters of DEMPT-PID control are changed according to the output current waveform of the previous dimming cycle to ensure the quality of the output pulse light.Finally,the feasibility of DEMPT-PID control is verified by experiments.In the fourth chapter,the overall design of LED plant lamps is introduced,including the selection of LED light quality,optimization of LED light distribution,design of the driver control module,design of the control mode,and so on.The secondary lens optimization spot problem is solved to concentrate the illumination range and improve the utilization rate of light energy.The LED drive system is designed with pre-storage mode and dynamic mode to realize the dynamic and accurate adjustment of the lighting environment.Finally,the efficiency of different light qualities is tested.In the fifth chapter,the LED pulse energy adjustable plant lamp designed in this paper is applied in the plant planting experiment to verify the promotion effect of pulse light on plant growth and the effect of energy-saving.Four groups of illumination environment are adopted,namely the reference group CK of continuous light,T1 with a pulse frequency of 1kHz and duty cycle of 50%,T2 with a pulse frequency of 1kHz and duty cycle of 70%,and T3 with staggered pulse mode,pulse frequency of 1 kHz and duty cycle of 50%.Through the analysis of the above four groups of hydroponic lettuce data under light environment treatment,it is concluded that T1 is the most suitable light for hydroponic lettuce,which can promote plant growth to a certain extent and save energy. |
