Foreword: as electronic product market and technology rapid development recently, many products depend on AC working. The product cannot work normally if the power is off. In order to make sure that the device can keep working to store and send the data for a while after power cut, this product needs a backup power with durance. Large Power has invented a lithium ion battery upgrading from 3.7V to 5V that can output stable voltage rapidly and charge the electronic product automatically.

Design requirement

Backup power design requirement of Internet of Things:

Based on the product specification and customer’s requirements, design backup battery to equip with host machine and integrate communication protocol terminal and 18650 lithium ion battery pack (3.7V voltage) into the scheme. The lithium ion battery outputs 5V voltage for standby under normal condition. If the product suffers power cut or abnormal power management, the backup battery of Internet of Things shifts automatically and keeps charging for the product so as to realize reasonable, efficient and safe power management. During the design process of the whole scheme, regard the perfect integration with host machine as direction, take the security and reliability of battery, battery pack and the whole system as precondition, and meeting relevant design regulations and certificate law as first choice. Besides, in order to make sure the security and reliability of lithium ion battery, the battery needs multiple protection to prevent damaging by overcharging, over discharging or short circuit.

Battery design solution of Internet of Things

Guard plate (PCM): it is protective circuit of rechargeable lithium ion battery pack. Because of the chemical characteristics of lithium ion battery, it needs protective functions of i overcharging, over-discharging, short circuit, overcurrent, over temperature, etc. so as to avoid combustion, explosion, etc.

Protection IC (S-8261): it is the chip has main protective function in the design scheme. The chip monitors the cell on the functions of overcharging, over-discharging, overcurrent, short circuit, etc. at any time, which helps the battery works under safe, stable and efficient circumstance.

Overcurrent protection (PTC): it is designed for secondary protective function. Restorable PTC fuse has dual functions of overcurrent protection and self-recovery. It can prevent high-temperature discharging and unsafe large current.

18650 lithium ion battery

MOSFET: it works as the switch in protective circuit to make sure that the voltages of two ends won’t be larger than rated value or lower than permissible value, so that the voltage will be stable and its cycle life will be longer.

Bosting control chip (S-8365AABBA): DC bosting chip has protective functions of overcurrent, overpressure and short circuit. It can output stable voltage and strong rated current for good efficiency and low loss.

Charging management chip: mature charging management scheme; 1% high precision, large current (setting 1000mA current) and make sure for fully charge each time.

Schematic diagram of design solution