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How to design an offline lithium battery charger?

by:Vglory      2021-04-09
How to design offline lithium battery chargers. High-efficiency, low-cost and reliable battery charger plans can be completed in many ways, but the choice of flash 8-bit microcontrollers can not only shorten planning time, reduce costs and supply safe and reliable products, but also enable Plan on-site sales promotion with minimal staff work. Considering the importance of cost, planned power, and safe charging, MCU solutions provide planners with many advantages. By choosing 8 MCUs with suitable peripherals and flash memory, engineers can use this to design an offline lithium battery charger. This is the case of the philips80C51 microcontroller, which comes with 2KB of flash memory and a suitable peripheral, providing a cheap solution. Integrated flash can also provide efficient and convenient debugging code and on-site software promotion (if required) talents. Because the planning community is not only familiar with and widely accepted 8-bit MCUs, but also software and hardware development can proceed quickly. Another advantage of this approach is to provide powerful and inexpensive development tools for various functions provided by many vendors. Using this method, the planning team can not only significantly shorten the planning cycle, but also make a more chaotic plan and keep the overall material cost (BOM) of the project within an acceptable planning range. For example, when the MCU is integrated with the internal oscillator, the offline lithium battery charger program benefits from two aspects. First, eliminate the external oscillator, saving money and PCB occupation; second, the internal oscillator can improve the stability of the system at startup. The four-channel A/D converter is another valuable peripheral circuit, and planners should try to integrate it into the chip. In addition to being more economical than using an external A/D converter, it can also be used to detect charging voltage, current and battery temperature, which are almost all important parameters in battery safe charging operations. The MCU (P89LPC916) used to complete the program described below not only integrates all these features, but also has a high-performance processor architecture that can execute instructions together on two clocks, and then increase its performance to six times that of the 80C51 device. It is very simple to configure Time0 (timer 0) as a PWM output, and it is easy to set up and use the PWM function. Root battery charging specification This method is specially designed for lithium battery charger solutions with additional 700-750mah, 3.6v discharge voltage and 4.2v voltage limit. The charging sequence is divided into three stages: pre-charge stage, stable current charging stage and stable voltage charging stage. When the remaining battery power is very small, so only a very low output voltage can appear, it is necessary to pre-charge. In this case, it is necessary to choose low-current charging to protect the battery. However, if the rechargeable battery can present a higher voltage (>3V), then the pre-charge phase can be eliminated. Of course, this is the most common situation. During the constant current and constant voltage charging phases, most of the electrical energy flows into the battery from the charger. The maximum charge current allowed by the battery is determined by the additional capacity of the battery. For example, for fast charging, a 700 mA battery can be charged with 350-400 mA current. In the case of a lithium battery, the MCU must monitor the charging current while maintaining the normal charging voltage of the battery, so that the charging process can be interrupted after the battery is fully charged. Temperature monitoring can be used to ensure a safe charging process, because any additional electrical energy will fully charge the battery converted into heat. Although it is necessary for the MCU to add a temperature monitoring function to its completed functions, most lithium batteries currently on the market have built-in overcharge protection, so despite the demand, temperature monitoring is rarely used. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: How many times is the life cycle of a lithium battery?
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