Design Of Solar Power Management Circuit Of Wireless Sensor Networks

Design of Solar Power Management Circuit of Wireless Sensor NetworksAlong with the developing of the Internet of Things in our country, one of the nerve endings of Internet of Things——Wireless Sensor Network (WSN), its role in the process of developing the Internet of Things is becoming more and more important, it has been more and more widely applied in the daily life of data collection, industrial control, etc. Wireless Sensor Network node is usually consists of sensor module, processor module, wireless communication module and power supply module. In the node circuit, power supply is usually by the way of battery power supply, power supply circuit often decides the service life cycle of wireless sensor nodes, and it is the important part of the node circuit. At present, if using the large capacity battery as the power of the wireless sensor node, battery will be exhausted after a short running time, so the energy limited battery power supply mode, can lead to replace the battery cause human and maintenance costs a lot of work. However, if the wireless sensor node is by the way of solar power supply, for those wireless sensor nodes that work in the outdoor, this way can supply a perennial power continuously, without replacement battery, at the same time solar energy is a green energy, environmental protection and energy saving, no pollution, easy maintenance. Now it is widely that the power circuit of wireless sensor network node is by the method of solar power.For solar power management circuits, it contains the solar panel module, charge and discharge circuit and battery module these three parts, the key problem in the circuit design has the following two aspects. From the perspective of the circuit functions, power management circuits need real-time monitoring the battery charging current and voltage of the battery in terms of charging, to avoid excessive charging, which will cause damage, such as leakage phenomenon. In terms of discharge, battery needs discharge protection, monitor the real-time voltage of the battery, in order to prevent the damage due to excessive discharge the battery. On the other hand, from the perspective of energy utilization, to make full use of solar power, the management circuit should achieve real-time tracking of maximum power point (MPPT) of solar panels to make full use of solar panels output energy. After DCDC circuit conversion, output energy of solar panel is used to charge the battery and super capacitor. The output energy of DCDC circuit can reasonably store by power management circuit, to achieve the full advantage of the output energy of DCDC circuit.This paper presents a highly efficient solar-powered power management circuit, which is by using batteries and super capacitor two level energy storage mechanisms to achieve rational allocation of solar panel output energy, and to achieve optimal battery charge protection, to ensure that the system is capable of long life working, without the need to replace the battery.This paper also presents a method based on the maximum output current of DCDC converter to track the maximum power point of solar panels, a method based on fuzzy logic control theory is applied to the solar power management circuit for intelligent charge and discharge management. A DCDC converter mathematical model is established, the theoretical deduction proved a fact that tracking the maximum power point of solar panels based on the maximum output current is feasible. According to the above model, we use STM8L single-chip microcomputer to control Sepic converter circuit to achieve tracking the maximum power point of the3W low power solar panels, and achieve constant current and constant voltage charge control and discharge protection control of the energy storage unit, the experimental results validate the correctness and rationality of the design, which implement the optimal charge and discharge control of solar power management circuit. Thesis research results is applied to the on-line dielectric loss measurement project based on wireless sensor network(WSN), the power management circuit has conversion efficiency of80%or more, and its quiescent current is less than1mA, under different temperature and light intensity, power management circuits can intelligently track maximum power point and do dynamic power management according to environmental conditions of the system, the experimental result confirm that the circuit cost is low, and it has a high stability and reliability.