With the development of China's economy, energy demand has increased significantly, and lighting power consumption has accounted for 10% and 12% of total electricity consumption. Converting solar energy into electricity is an effective way to save energy. However, the instability of the solar energy will cause the battery voltage to be too low, which will affect the normal operation of the lighting system.
In view of the problem of solar and battery voltage instability, this paper proposes a dual-supply power supply mode combining solar energy and 220V power supply. Through the analysis of the characteristics of the battery and LED, the photoelectric complementary LED street light controller with PIC microcontroller as the core is designed. The controller can realize the charging and discharging control of the battery, the automatic switching of the battery power supply and the commercial power supply, and the control of the variable power lighting of the LED load, which can better meet the control requirements of the photoelectric complementary lighting system and improve the solar lighting system. Reliability, energy-saving lighting of LED street lights is realized.
1 controller structure and main functions 1.1 controller structure Photoelectric complementary lighting system controller structure as shown in the dotted line box, mainly composed of PIC microcontroller and peripheral circuits. The peripheral circuits mainly include: battery charging and discharging and protection circuit, battery power supply, a city power supply switching circuit, LED load driving circuit and signal sampling circuit.
Fund Project: Electrical and Mechanical Transmission Control of Guizhou Province Science and Technology Research Fund Project (黔科åˆSYå—3025å·).
1.2 The main function controller of the controller mainly realizes the following functions: voltage sampling of battery and solar battery. Timely voltage acquisition and A/D conversion of the battery and the solar battery are realized by the voltage sampling circuit.
Charge and discharge control of the battery. The single chip compares the sampling voltage with the set voltage, and sends a corresponding control signal according to the comparison result to realize the charge and discharge control of the battery.
Automatic switching control of battery power supply and mains supply. Comparing the collected battery voltage Vcx with the discharge protection voltage VoXmn of the battery, the corresponding port of the single chip transmits a control signal to the battery power supply switching circuit to realize automatic control of the battery power supply and the power supply switching.
Hurry up the branch to achieve LED power variable power lighting control. According to the input result of the human body infrared sensor, the corresponding port of the single chip sends a PWM control signal with different duty ratio to the load driving chip enable end to realize the variable power operation of the LED load.
2 controller hardware circuit design 2.1 PC single chip selection MCU is the core of the whole controller, the system needs to real-time sampling battery and solar cell voltage, the output voltage of solar cell is greatly affected by external factors, so the real-time system More powerful. Therefore, the system uses a PIC16F877A microcontroller with an A/D module and a 14-bit instruction width. The MCU uses three analog signal input ports AN0, AN1, AN2 and four output ports RC0, RC1, RC2, RC3. Among them, AN0, AN1, AN2 are used as analog signal input ports for battery, solar cell and human body infrared sensor respectively. RC0, RC1, RC2, and RC3 are used to control the on and off of the transistors T2, T3, and T5, respectively, and to issue PWM control signals to the LED driver chip.
2.2 Signal Sampling Circuit The signal sampling circuit is very important in the whole controller. The accuracy of the sampling voltage of the battery and the solar cell is directly related to whether the whole system can operate accurately.
The input analog voltage of the PIC16F877A MCU can be up to 5V. For safety reasons, the terminal voltage of the battery and the solar cell must be divided by the resistor before being sent to the analog input port of the MCU. Sampling circuit As shown, R1R6 is 6 voltage-dividing resistors with a precision of 5%. At the same time, in order to improve the anti-interference of the circuit and the sampling voltage is not distorted during transmission, between the A/D converter module and the voltage dividing resistor. Two voltage followers A1 and A2 are added. The A/D conversion result of the signal sampling circuit PIC16F877A is related to the input analog voltage and voltage: 2.3 The lead-acid battery is used in the battery charge and discharge control and protection circuit design, and the charging process is divided. It is a four-stage, namely: trickle charging phase, constant current charging phase, constant voltage charging phase and floating charging phase.
Battery charge and discharge control and protection circuit as shown, when the solar cell and battery voltage meet: Va; X Battery power supply - Mains power supply switching circuit 2.5LED load drive circuit and variable power illumination realize the working relationship between the brightness and current of the led load is approximately linear, but the current is too large to reduce its service life, the current is too small, the brightness is not enough, so it must be adopted Special constant current source drive circuit. This design adopts LED dedicated step-down constant current source driver chip PT4115. Its pin functions are: Vin is the DC power input terminal, CSN is the signal input terminal of the current reverse t expensive resistor R14, and SW is the internal power switch output terminal of the chip. Dim is the power switch enable. LED load drive circuit as shown, if 220V mains supply power to the LED load, it needs to change the 220V AC to 30V AC through the AC transformer (down to page 1856). 5 Conclusion By using the output voltage as the control object and the output current as The transfer function is established by two different control methods of the voltage-controlled switch regulation system of the control object. After comparing the control object from the output voltage to the output current, the system bandwidth decreases due to the change of the control object. In order to introduce the coefficient K when controlling the object, an improved method for reducing the input voltage in the design of the control object is proposed. The output voltage can be directly controlled and the output current can be controlled. Correspondence, theoretical analysis and system simulation. The main program includes the following contents: timely sampling the voltages Vox and Vxp of the livestock battery and the solar battery, and saving the sampling result to the data memory EEPROM; comparing Vcct and Vcomin, if VccVccrmn, entering the load illumination mode, otherwise entering the battery charging mode; The mains supply power to the load, otherwise the battery is used to supply the load. In the lighting mode, if the infrared sensor has input, the full power illumination, otherwise the half power illumination; in the battery charging mode, when the battery is charged by the solar battery; When Vccx
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