Application of PTC thermistor in lithium battery
polymer battery (ie, lithium ion battery), compared with NiCd or NiMH battery, has the unique advantages of large power capacity per unit volume, large current density, fast charging, small size, light weight, high conversion efficiency and so on. It is not only widely used in various portable devices and mobile devices. And can be used in various fields such as medical devices, industry, agriculture, national defense, and transportation. However, in the actual application process of lithium-ion batteries, there are quite strict requirements on conditions such as charging, discharging, and high-temperature environments. When charging, the voltage at both ends of the battery is too high, which will increase the risk of battery leakage, smoke, burning, and explosion, which is very harmful. Overcharging may be caused by uncontrolled charging, wrong electrode or incorrect charger; when the charging and discharging current of lithium-ion battery is too large or external short-circuit, internal heating may damage the battery or burn other parts, which will seriously shorten the battery’s cycle life; Similarly, lithium-ion batteries work in high-temperature environments or encounter loads and large currents that cause high temperatures inside the lithium-ion batteries. Lithium-ion batteries will also increase the risk of battery leakage, smoke, burning, and explosion.
Therefore, a dedicated battery management circuit must be designed for lithium-ion batteries. All lithium-ion battery management circuits include overcharge and overdischarge termination control functions, and there is no protection against overcurrent, overtemperature, short circuit, etc., so the protection circuit The task is to monitor the parameters of the battery charging and discharging state in view of various possible faults of the battery, to ensure the battery life and efficiency, and to protect the battery and external equipment from damage. Polymer PTC thermistor products have outstanding advantages in the over-current, over-temperature, and short-circuit protection of high-current density lithium-ion batteries and their management circuits. Polymer PTC thermistors are also called self-resetting overload protectors or self-resetting overload protectors. Reset the fuse, a single component can complete over-current, over-temperature, and short-circuit protection. It has an irreplaceable role in the protection application of lithium-ion batteries and their management circuits, and has now developed into a protective element that must be used in lithium-ion batteries and their management circuits.
Li-ion battery management and protection circuit is usually a primary protection circuit composed of a dedicated integrated IC and a metal oxide field effect transistor. The protection IC controls the turn-on or turn-off of the FET by monitoring the voltage across the battery and the discharge current to prevent malfunctions such as overcharge, short circuit, and overdischarge. Although primary protection is generally considered to be reliable, the protection IC or MOS-FET may be damaged when the electrostatic discharge voltage is too high or over-temperature, and the integrated circuit will oscillate when a short circuit occurs. At the same time, most IC+MOS-FET circuits charge , The detection of discharge overcurrent is indirect, and it cannot guarantee that overcurrent protection will be provided under all working conditions of the battery, and the reliability of the protection is also reduced. After the polymer PTC thermistor is connected to the protection circuit, even if the protection circuit fails or the temperature rises high, the PTC can still provide timely protection against overcharge, overcurrent, short circuit, overtemperature and other faults to ensure that the battery is incorrectly protected. In the case of use or abuse, or external reverse connection, short circuit, etc., safety problems such as explosion and damage to the battery will not occur.
Popular ic chip you may need:
D25XB60
FQP17P06
FDPF33N25T
2SC2525
