Explain the design of mobile power protection circuit and product selection

Mobile power protection circuit design and product selection Nowadays, smart phones consume more and more power, and most smart phones’ batteries are non-removable. Therefore, a large-capacity portable power supply and lunch box have become a must for people to travel. Prepared electronic products. However, the frequent occurrence of mobile power supply accidents has forced users and engineers to re-examine the planning and development of mobile power supply from the very beginning. How much do you know about the internal structure of a mobile power supply? A mobile power supply generally consists of a casing, a battery and a circuit board. The outer shell is the first process of product packaging, and has beautiful end-face modeling, protection and other functions. It is generally used for plastics and metals, and some products are often plastics and are also used for fire protection information. The circuit board is mainly used for terminal voltage, current control, input and output control and other functions. Batteries are the most expensive components in mobile power sources, and 18650 batteries and polymer batteries are the two most common ones. In addition to batteries, circuit boards are also important in mobile power supplies. Regarding rechargeable batteries, this specification has a safe charge cut-off voltage and a safe discharge cut-off voltage, with a calibrated additional maximum operating current. In mobile power planning, the polymer battery must be safely charged first, because the cost of the battery is relatively high, and for the safe and reliable operation of the system, there must be a charging processing system. Polymer batteries are discharged when charging portable devices. Because of their wide input voltage of 5V, they have a 5V boost. Regardless of whether it is a charging processing system or a boosting system, the circuit board is required for power supply, so the internal circuit board's planning for the mobile power supply determines whether the product is smart or not. 1. Charge protection Lithium battery overcharge protection uses a power processing chip to detect the end of the voltage, and the inside of the chip is the reference setting (the mobile phone lithium battery is generally 3.5v). When the reference value gradually rises and rises to the programmed value of vss-vdd, the voltage at this time is the protection overcharge shutdown voltage, and the overcharge protection is completed by the logic connection to output a low level or a high level to control the external control circuit. When the voltage drops slowly, set the voltage value of vss-vdd as the reference value. When a reference is detected under the settings, this is the logical connection to remove the overcharge protection. 2. Over-discharge protection Over-discharge protection voltage refers to the lowest voltage that protects the battery during discharge transition. When the discharge reaches this voltage point, the protection circuit blocks the circuit, achieving the purpose of protecting the battery. According to the connection of battery life and depth of discharge, the connection of battery voltage, discharge rate and depth of discharge, combined with the actual load of the device, determine the battery discharge stop voltage and plan the battery discharge protection circuit. 3. Short circuit protection The circuit current caused by the short circuit is generally more than 10 times of the extra working current, and the overcurrent protection has a delay of tens of milliseconds. Dozens of times the extra current that appears in a direct short circuit will also affect the function of the battery within tens of milliseconds. The existing protection methods include the PPTC method, that is, a thermal resistance circuit with a sudden increase in current, but at the same time a response time of milliseconds is required, and the impedance of the circuit is added. There is also an integrated chip specifically for short-circuiting the battery, which has a small application scale and high cost. 4. Analyzed the PTC (Automatic Train Control System) PTC positive temperature coefficient thermistor, also known as polysilicon, polymer self-fuse (polymer resettable fuse), polymer matrix and conductive carbon black behind the fuse Particle composition. Because polymer fuses are conductors, current flows through them. When the overcurrent flows through the polymer self-fuse, heat (I2R) will cause it to expand. The carbon black particles are separated and the resistance of the polymer self-fuse increases. This will cause the polymer self-fuse to heat up faster, expand more, and further add resistance. When the temperature reaches 125°C, the resistance changes significantly and the current decreases significantly. The small current flowing through the polymer self-healing fuse is sufficient to keep the fuse in this temperature and high resistance state. When the fault is eliminated, the polymer is shortened from the composite fuse to its original shape, and the carbon black particles are combined together. Statement: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete the previous one: Introduction Lithium battery anode materials: graphite and graphene