With the development of modern society, entertainment has begun to turn to outdoor, many entertainment facilities also began to tend to outdoor. Portable Bluetooth player is one of the most popular products for outdoor entertainment. Due to its full miniaturization and portability, high-quality speaker effect, and the integration of the special functions of home utility player and Bluetooth transmission, it has become the first choice of outdoor entertainment equipment in modern society. Because of the requirements of portability, providing a safe, efficient, stable, portable and sufficient backup power solution for portable Bluetooth player has become an important guarantee for people to have a long time outdoor entertainment. Because of its unique advantages, portable Bluetooth player backup battery has become the first choice of power solutions for outdoor entertainment devices.
1. Design requirements of backup lithium battery for portable Bluetooth player:
The working current of the player is small, but the continuous working time of the battery is required to meet the continuous working time of the equipment for at least 8 hours. The battery should have the over temperature protection function, and the finished battery should pass the UL2054 certification requirements, and the weight of the battery should be controlled within 200g. For this reason, our company adopts imported Samsung cell, which has the advantages of high energy ratio, light weight, small volume, high cycle life, high safety, high voltage and good consistency. The lithium battery pack is designed to output over-current protection value of 15a, maximum continuous working current of 2.2A and charging capacity of 2.2ah, which fully meets the power consumption time demand of the player. The specific design parameters are as follows:
1) Lithium battery pack model design requirements: 18650-3s1p / 2.2ah/11.1v.
2) Circuit design requirements:
• Single section overcharge protection voltage: 4.35 ± 0.25V
• Single section overcharge recovery voltage: 4.15 ± 0.50v
• Single section over discharge protection voltage: 2.40 ± 0.08v
• Recovery voltage of single section over discharge: 3.00 ± 0.10v
• Over current protection value of combined battery (10ms): 10 ~ 17A
• Over temperature protection value of combined battery (recoverable): 70±5 ℃
• The finished battery has short circuit and reverse charge protection.
3) Battery cycle life design requirements: 300 ~ 500 times (national standard for charging and discharging)
4) Battery size design requirements: refer to the finished battery size
2. Design scheme of backup lithium battery for portable Bluetooth player:
1) Protection board (PCM): it is mainly a protection circuit designed for rechargeable lithium battery pack. Due to the chemical characteristics of lithium battery itself, it needs to provide intelligent power calculation, overcharge, over discharge, short circuit, overcurrent and other protection functions to avoid burning, explosion and other hazards.
2) Protection IC (Protection IC): the main protection function chip of the design scheme, which can monitor the overcharge, over discharge, over current, short circuit and other functions of the cell online and constantly, so that the cell can work in a safe, stable and efficient range.
3) Temperature switch: mainly designed for temperature protection function. When the temperature of the battery itself reaches 70 ± 5 ℃ due to other abnormal problems, the temperature switch will act for temperature protection
4) 18650 Li ion cell: 18650 / 2200mAh / 3.7V Li ion cell.
5) Field effect transistor (MOSFET): MOSFET, in the protection circuit to play a switching role, always make the voltage at both ends of the load will not rise or fall, to ensure voltage stability.
6) Battery package: PCV heat shrinkable