Detailed Lithium-ion battery integrated protection circuit

During the use of lithium-ion batteries, overcharge, over-discharge, and overcurrent are important factors that affect the service life and performance of lithium-ion batteries. The lithium-ion battery integrated protection circuit effectively monitors and prevents damage to the lithium-ion battery through each protection unit circuit. Lithium-ion battery charge and discharge protection circuit, a lithium-ion battery protection circuit is composed of two field-effect transistors and a control integrated circuit plus some resistance and capacitance elements. Due to the high energy density of lithium-ion batteries, it is difficult to ensure battery safety. In the overcharged state, the battery's energy will be excessive after the temperature rises, so the electrolyte decomposes to generate gas, which may cause spontaneous combustion or rupture due to the increase in internal pressure; on the contrary, in the over-discharged state, the electrolyte will decompose and cause the battery characteristics and The durability is deteriorated, thereby reducing the number of rechargeable times. The maximum end-of-charge voltage of a single-cell lithium battery is 4.2V, which cannot be overcharged, otherwise, the battery will be scrapped due to the loss of too many lithium ions in the positive electrode. When charging the lithium battery, a dedicated constant current and constant voltage charger should be used. First, charge with constant current until the voltage at both ends of the lithium battery is 4.2V, then switch to the constant voltage charging mode; when the constant voltage charging current drops to 100mA, Charging should be stopped. The charging method required for lithium-ion batteries is constant current and constant voltage charging. The initial charge is a constant current charge. As the charging process progresses, the charging voltage gradually increases to 4.2v (depending on the cathode material, some batteries have a constant voltage of 4.1v). During the charging of the lithium-ion battery, if the charger circuit is out of control, after 4.2v, the lithium-ion battery will continue to be charged with a constant current, and the voltage of the lithium-ion battery will continue to rise at this time. When the voltage of the lithium-ion battery is higher than 4.3v, the chemical side-use of the lithium-ion battery will be aggravated, resulting in battery damage or safety problems. The protection circuit of the lithium-ion battery is to ensure safety in such an overcharge and discharge state and prevent the deterioration of the characteristics. The protection circuit of the lithium-ion battery is composed of a protection IC and two power MOSFETs. The protection IC monitors the battery voltage and switches to an external power MOSFET to protect the battery when it is overcharged or discharged. The function of the protection IC is excessive. Charge protection, over-discharge protection, and over current/short circuit protection. Due to the internal structure of the lithium battery, all lithium ions cannot move to the positive electrode during discharge, and some lithium ions must be retained in the negative electrode to ensure that lithium ions can be inserted into the channel smoothly during the next charge. Otherwise, the battery life will be shortened. In order to ensure that some lithium ions remain in the graphite layer after discharge, it is necessary to strictly limit the minimum discharge termination voltage, which means that the lithium battery cannot be over-discharged. Of course, the single crystal of functional components is an unchanging goal. For example, mobile phone manufacturers are currently moving towards a two-chip chipset composed of peripheral circuits such as protection ICs, charging circuits, power management ICs, and logic ICs, but the open-circuit impedance of the power MOSFET is currently required It is difficult to integrate with other ICs. Even if a single chip is made with special technology, the cost will be too high. Therefore, it will take some time to protect the single crystal of IC.