Outdoor multi-energy charging treasure solution development

In recent years, with the wave of economic globalization sweeping the world, issues such as energy and environmental protection have increasingly become topics of international attention, and international cooperation in environmental protection is booming. Mechanical energy power generation is a clean, environmentally friendly and convenient energy source that is not restricted by the environment, and has always been favored by people; wind power generation is an energy source with relatively large limitations but great usable value. A new type of energy has the advantages of being green and clean, without environmental pollution, inexhaustible and without geographical restrictions. The charger designed in this paper is based on these aspects, integrating mechanical power generation, wind power generation, and solar power generation, and the charger adopts a modular structure and a standard USB interface, which can be used for various digital products such as mobile phones, MP3s, and cameras. Charge.

1. The principle of smart charging treasure

The structure of the smart power bank is shown in the figure below, which consists of mechanical energy conversion circuit, wind energy conversion circuit, solar energy conversion circuit, power supply and its management circuit, low-power single-chip microcomputer, GPS module and display module. Power bank energy conversion input part: mechanical energy voltage conversion circuit, wind energy conversion circuit and solar energy conversion circuit. Power bank output part: The charger is equipped with a standard USB interface and emergency lighting. Power supply part: the battery management circuit can monitor the battery status in real time, and display it on the LED, and protect the battery from overvoltage, overcurrent, overcharge, overdischarge and other multiple protections; processing part: the single chip microcomputer processes the data received by the GPS module Finally, the time, latitude and longitude, and altitude are displayed on the LED in real time.

2. The design of each module of the power bank

2.1 Charging energy input part

The voltage regulator used in this product is L7805cv. L7805ev is a three-terminal positive voltage regulator, which forms a regulated power supply without external compensation components. It contains current limiting protection current to prevent the load from being burned due to short circuit. Contains a power consumption limiting circuit; prevents burning out of the output driver transistor, and is reliable and convenient to use. The output current can reach 1.5A, the output voltage range is 4.75-5.25V, the input voltage range is 7-35V, and the output resistance is small, which is very suitable as a core device for mechanical energy, wind energy, and solar energy conversion circuits.

The single-chip microcomputer is a kind of integrated circuit chip, which uses VLSI technology to integrate the central processing unit CPU with data processing capabilities, random memory RAM, read-only memory ROM, various I/O ports and interrupt systems, and timers/timers. And other functions, integrated into a small but complete computer system formed on a silicon chip.

This product uses STC89C52 microcontroller as the core processing chip. STC89C52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K in-system programmable Flash memory. On a single chip, with smart 8-bit CPU and in-system programmable Flash, STC89C52 provides highly flexible and super-effective solutions for many embedded control application systems. Has the following standard functions: 8K bytes of Flash, 512 bytes of RAM, 32-bit I/O port lines, watchdog timer, built-in 4KBEEPROM, MAX810 reset circuit, three l6-bit timers/counters, one 6-vector 2-level Interrupt structure, full-duplex serial port. In idle mode, the CPU stops working, allowing RAM, timer/counter, serial ports, and interrupts to continue working. In the power-down protection mode, the contents of RAM are saved, the oscillator is frozen, and all work of the single-chip microcomputer stops until the next interrupt or hardware reset. The highest operating frequency is 35MHz, 6T/12T is optional.

1. Mechanical energy part

When a part of the conductor of a closed circuit moves in a magnetic field to cut the magnetic field lines, a current will be generated in the conductor. This method of using a magnetic field to generate current is called electromagnetic induction, and the resulting loop current is called induced current. Mechanical energy can be converted into electrical energy by cutting the magnetic field lines of the electromagnetic coil. A generator can be made by using the phenomenon of electromagnetic induction to convert mechanical energy into electrical energy. The maximum induced electromotive force of the alternator satisfies the formula Em=nBStotel.

The mechanical energy conversion circuit can convert the unstable and excessive output voltage of the mechanical energy generator into a standard input voltage, preventing the excessive voltage fluctuation generated by the mechanical energy generator from seriously affecting other circuits or batteries. Since the output voltage and power of the mechanical energy generator fluctuate greatly, firstly, the DC voltage output is obtained after full-bridge rectification and capacitor filtering, and then the voltage is stabilized by the voltage regulator L7805ev to output a stable 5V voltage, and through the marked USB interface output. Among them, the capacitor is used to filter out the high-frequency and low-frequency voltage at the output and input terminals of the chip, and because the output current through L7805cv is relatively large, a 5n voltage-dividing current-limiting resistor is connected in series, and the output of L7805ev is about 5V DC voltage. It is more convenient to charge various devices. In order to charge the battery directly, a 1N4007 diode is added to the output end, and the standard charging voltage of the lithium battery is obtained by using the diode voltage drop principle, which can be used for normal charging of the battery and for lighting. .

2. Wind energy

The wind drives the windmill to rotate, converts wind energy into mechanical energy, and converts mechanical energy into electrical energy through the principle of electromagnetic induction.

The principle of wind energy conversion circuit is similar to that of mechanical energy voltage conversion circuit. Compared with the voltage converted from mechanical energy, the voltage fluctuation obtained from wind energy conversion is relatively small, and the output voltage and power of wind energy generators are relatively low. Therefore, the wind energy conversion circuit first uses full-bridge rectification, and then stabilizes the voltage through the voltage regulator L78o5ev to output Stable 5V voltage for use. The output of L7805cv is 5V DC voltage. Adding a 1N4007 diode at the output end uses the principle of diode voltage drop to provide the standard charging voltage of the lithium battery, and then charging the battery can normally charge the battery and work for the lighting lamp.

3. Solar energy

Photovoltaic effect is the phenomenon that light causes a potential difference between different parts of inhomogeneous semiconductors or semiconductors combined with metals. It is firstly the process of converting photons into electrons and light energy into electrical energy; secondly, it is the process of forming voltage. After forming a current loop, it can supply power to the load. There are many types of solar cells, and silicon solar cells are still the main products at present. Silicon solar cells have different sensitivities to incident light of different wavelengths. The wavelength range of solar radiation that can produce photovoltaic effects is 0.4-1.1m, and the maximum sensitivity of the spectral response of silicon solar cells is 0.8-0.95m.

Due to the instability of electric energy converted from light energy, a voltage stabilizing circuit is required to complete the stable work of voltage. The voltage stabilizing circuit in this design mainly consists of an integrated voltage stabilizing CW7805, a capacitor and a diode used to prevent current backflow.

2.2 Charging energy output part

This product is equipped with a standard USB output interface, the output voltage is 4.75V-5.25V, and the output is about 500mA. It can normally supply power for mobile phones, cameras, MP3 and other equipment in case of emergency. Secondly, this product is equipped with high-efficiency energy-saving lighting. When the light is dark at night, the battery can be selected to be used through switch control or the extra energy of mechanical energy and wind energy modules can be used to provide lighting circuits for emergency needs. Make the lighting use the extra mechanical energy and the electric energy converted from wind energy. When the energy converted from mechanical energy and wind energy is less, that is, the voltage is not enough, or the mechanical energy and wind energy are not working, the lighting circuit can automatically switch to battery power supply. mode to keep working.

2.3 The power part of the power bank

1. Power protection

As the power supply equipment of all electronic products, the power supply not only needs to meet the requirements of power supply products, but also has its own protection measures, such as overvoltage, overcurrent, and overheat protection. Once an electronic product fails, such as a short circuit on the input side or an open circuit on the output side of the electronic product, the power supply must turn off its output voltage to protect the internal circuit of the device from being burned, otherwise it may cause further damage to the electronic product. The power supply of this product has a variety of built-in protection circuits, such as over-current protection, over-voltage protection, over-charge protection and over-discharge protection.

(1) Over-current protection: When the current exceeds the set current, the device will automatically power off, and the method of protecting the device is called over-current protection. When the voltage at the two terminals of EB of Ql is O.TV, Q1 is turned on, and the voltage at terminal C is output. Therefore, based on the principle of overcurrent detection, the magnitude of the detection current depends on the values of RI and R2, and the voltage at the two terminals of the transistor EB exceeds 0.7V. When it is turned on, the circuit will cut off the output of the subsequent stage after it is turned on, which plays a protective role.

(2) Overvoltage protection: When the output voltage exceeds a certain value, the output voltage is limited within the safe value range, which is overvoltage protection. When the internal voltage stabilization loop of the switching power supply fails or the output overvoltage occurs, the overvoltage protection circuit will protect it to prevent damage to the subsequent electrical equipment.

In terms of performance, thyristor not only has unidirectional conductivity, but also has more controllability than silicon rectifier elements. It has only two states of on and off. Thyristor has many advantages, such as: controlling high power with low power, and the power magnification is as high as hundreds of thousands of times; the response is extremely fast, and it is turned on and off within the order of microseconds; no contact operation, no spark, no noise, etc. wait.

(3) Overcharge protection: Overcharge refers to continuing high-voltage charging after normal charging, which may lead to increased internal pressure of the battery, battery deformation, liquid leakage, etc., resulting in a significant decrease in battery performance or even battery damage. Overcharging causes the remaining lithium ions on the positive electrode to continue to transfer to the negative electrode, but the negative electrode cannot embed more lithium ions, so that lithium ions are precipitated as metal lithium on the surface of the negative electrode, causing dendrites and other phenomena, resulting in damage to the isolation film, battery short circuit, and electrolyte leakage. danger of burning.

(4) Over-discharge protection: Over-discharge is the phenomenon that the battery continues to discharge after it is normally discharged to the cut-off voltage. Exceeding the cut-off voltage of battery discharge and continuing to discharge will cause the internal pressure of the battery to rise, the reversibility of the positive and negative active materials will be damaged, and the capacity of the battery will be significantly reduced. Since a certain amount of lithium ions needs to be kept in the negative electrode to maintain a stable structure, over-discharging will cause more lithium ions to move out, destroying the stable structure of the negative electrode and causing irreversible damage to the negative electrode.

The circuit is mainly composed of lithium battery protection application-specific integrated circuit DW01, charge and discharge control is composed of MOS-FET and other parts. During the charging process, when the voltage of the single battery exceeds 4.35V, the OC pin output signal of the ASIC DW01 turns off the charging control MOSFET, and the lithium battery immediately stops charging, thereby preventing the lithium battery from being damaged due to overcharging. During the discharge process, when the voltage of the single battery drops to 3.70V, the OD pin output signal of DW01 turns off the discharge control MOSFET, and the lithium battery immediately stops discharging, thereby preventing the lithium battery from being damaged due to over-discharge. The CS pin of DW01 is When the output of the current detection pin is short-circuited, the conduction voltage drop of the charging and discharging control MOSFET increases sharply, the voltage of the CS pin rises rapidly, and the output signal of DW01 makes the charging and discharging controlling MOSFET turn off quickly, thereby realizing overcurrent or short circuit protection.

2. Handling of remaining battery power

(1) Charging characteristics of lithium batteries: Lithium-ion batteries have high requirements on voltage accuracy, and the error cannot exceed 1%. At present, the battery with a rated voltage of 3.7V is commonly used. The charging termination voltage of this battery is 4.2V, so the allowable error range is 0.042V. Lithium-ion batteries usually use constant current to constant voltage charging mode. Charging begins as a constant current stage, and the voltage of the battery is low. During this process, the charging current is stable. As the charging continues, the battery voltage gradually rises to 4.2V. At this time, the charger should immediately switch to constant voltage charging, and the charging current will gradually decrease. When the current drops to a certain range, it enters the trickle charging stage, and the charger continues to charge the battery at a certain charging rate, and finally makes the battery in a sufficient state.

(2) Discharge characteristics of lithium batteries: When discharging lithium batteries, first, the discharge current should not be too large. Excessive current will cause internal heating, which may cause permanent damage. After the battery voltage cannot be lower than the end-of-discharge voltage, if it continues to discharge, over-discharge will occur, which will also cause permanent damage to the battery. Under different discharge rates, the change of battery voltage is very different. The greater the discharge rate, the battery under the corresponding remaining capacity. The lower the voltage. The battery capacity can be measured according to the corresponding relationship between the charging and discharging voltage and the electric quantity of the lithium battery. According to the charging and discharging curve of the battery in normal use, the charging and discharging process is divided into 4 equal parts. Taking the lithium battery with a charging limit voltage of 4.2V as an example, the corresponding relationship between voltage and remaining power percentage can be listed as follows: 4.20V-100%, 3.85V - 75%, 3.75V - 50%, 3.60V - 25%, 3.40V - 5%. Obviously, the highest accuracy is only 25%. In addition, the battery voltage will change suddenly with the power transmission of RFPA, and it will usually decrease by 0.2V to 0.3V. In order to solve the measurement problem that the battery voltage suddenly decreases, the common method is to use the software algorithm to perform average filtering to average the battery voltage within a period of time. If the average battery voltage during this period drops, it means that the estimated power is reduced, otherwise That is, it is considered that the power has not actually changed.

There is a defect in the method of simulating the remaining power of the battery voltage, which can be improved by monitoring the power consumption of the battery in real time and calculating the remaining power through the coulomb counter. FAN4010 is a current detection chip, which is specially used to detect the charging and discharging current of the battery of portable devices. It can convert the current signal passing through the precision detection resistor into a voltage signal that can be detected by ADC, so as to calculate the real power consumption within a period of time.

Summarize

Although there are many bicycles for charging electronic devices such as mobile phones at present, most of the products mainly have the following two disadvantages. On the one hand, the energy utilized by most modified bicycles is single and needs to be charged for a long time; on the other hand, because it is expensive, it is difficult for most users to accept, so it cannot be popularized. This product starts from life, makes full use of natural resources, and combines wind energy, solar energy, and mechanical energy. It not only realizes the charging function, but also maximizes the use of natural resources. To sum up, this product can make full use of wind energy, solar energy and mechanical energy. It is suitable for cycling enthusiasts such as going to the beach and mountaineering. It is clean, environmentally friendly and healthy. It is the trend of future development and has a good application prospect.

The above is the development example of smart charging treasure introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. for you. If you have the development needs of smart charging treasure solutions, you can trust us. We represent a variety of single-chip microcomputers, voice chips, dual-mode Bluetooth ICs, and wifi chips. Brands include Songhan MCU, Yingguang MCU, Jerry Bluetooth, Ankai Bluetooth, Allwinner, and Realtek. Our technical services include: PCB design, MCU development, Bluetooth solution, software and hardware custom development, APP development, small program development, WeChat official account development, etc. It can also undertake the design of intelligent electronic products, the development of living appliances, the research and development of beauty equipment, the application of Internet of things platform, the smart home control system, the development of TWS earphones, Bluetooth earphone speakers, the development of children's educational toys, the design of electronic education products, etc.