Nowadays, smartphones consume more and more power, and most of the smartphone batteries are not removable. A mobile power source with large capacity and convenient carrying capacity has become an essential electronic product for people to travel. However, the recent mobile power safety accidents have caused consumers and engineers to re-examine the design and development of mobile power. How much do you know about the internal structure of mobile power? A mobile power source usually consists of a housing, a battery, and a circuit board. The outer casing is mainly product packaging, as well as the effect of beautiful appearance, protection, etc., which are commonly used for plastics and metals. Some good products are often fireproof materials for plastics. The board is primarily used for voltage, current control, input and output control, and more. Cell is the most costly component of mobile power, with 18650 cells and polymer cells being the two most common. In addition to the battery core, the board in the mobile power supply is also very important. For rechargeable batteries, the specification has a safe charge cut-off voltage and a safe discharge cut-off voltage, with a nominal rated maximum operating current. The design of the mobile power supply must first securely charge the polymer battery because the battery cost is relatively high, and a charging management system is required for the safe and reliable operation of the system. When it is necessary to charge a portable device, the polymer battery is discharged to the outside. Since the portable device generally has a input voltage of 5V, there is a system that boosts 5V. Both the charging management system and the boosting system require a circuit board to provide, so the design of the internal circuit board of the mobile power supply determines whether the product is smart or not. 1. Overcharge protection Lithium battery overcharge protection is realized by the power management chip to detect the voltage. The internal state of the chip is in the reference setting state (the mobile phone lithium battery is generally 3.5V). When the reference rises slowly, when it rises to the VSS-VDD design value, the voltage at this time is the protection overcharge shutdown voltage, and the external control circuit is controlled by the logic output low or high level to achieve overcharge protection. When the voltage drops slowly, set the VSS-VDD voltage value to take the reference value. When the reference detects that it is below the setting, this is the logical relationship to cancel the overcharge protection. 2. Over-discharge protection The over-discharge protection voltage refers to the lowest voltage that protects the battery during the discharge transition. When discharging to this voltage point, the protection circuit cuts off the circuit to achieve the purpose of protecting the battery. According to the relationship between battery life and discharge depth and the relationship between battery voltage and discharge rate and discharge depth, combined with the actual load of the equipment, the battery discharge termination voltage is determined, and the battery discharge protection circuit is designed. 3. The circuit current caused by the short circuit protection short circuit is generally more than 10 times of the rated working current, while the overcurrent protection needs to be delayed by about tens of milliseconds. The direct short circuit causes dozens of times the rated current in tens of milliseconds will also be on the battery pack. Performance has an impact. The existing protection method is the PPTC method, which is a thermal cut-off circuit generated by current, which also requires a reaction time of a millisecond level, and increases the impedance in the loop. There is also a short-circuit integrated chip dedicated to the battery pack, which has a narrow application range and high cost. 4.PTC introduces PTC positive temperature coefficient thermistor, also known as polyswitch, polymer resettable fuse polymer self-resetting fuse consists of polymer matrix and carbon black particles making it conductive. Since the polymer self-resetting fuse is a conductor, current flows therethrough. When an overcurrent is passed through the polymer self-resetting fuse, the heat generated (I2R) will cause it to expand. As a result, the carbon black particles will separate and the resistance of the polymer self-resetting fuse will rise. This will cause the polymer self-resetting fuse to generate heat more quickly, expand more, and further increase the resistance. When the temperature reaches 125 ° C, the resistance changes significantly, so that the current is significantly reduced. The small current flowing through the polymer self-resetting fuse at this point is sufficient to keep it at this temperature and in a high resistance state. When the fault is removed, the polymer self-resetting fuse shrinks to its original shape and rejoins the carbon black particles, thereby reducing the resistance to a level that has a specified holding current. Understand the main components inside the mobile power supply, then how do we choose a high-quality mobile power supply? 1. Battery Although I have repeatedly introduced the battery in the articles I wrote earlier, I don't necessarily understand it, so I will describe it here. The current mobile power supply on the market is 18650 and soft-pack lithium batteries. The 18650 is a liquid lithium battery that is wrapped around a thick steel shell and has an aluminum shell and a cylindrical shape. The other is a paste-like lithium battery, which is known in the industry as a soft bag that can be customized in a variety of shapes. The advantages of the 16850 are: mature technology and large capacity. It is said that the largest one can achieve 3000mAh. If it is simply based on the battery core, then the 18650 has certain safety hazards. The laptop battery explosion in previous years is a case. (Note: the probability is very low, and the protection board is selected, it can effectively reduce the safety.) The soft-pack lithium battery is calculated according to the length, width and thickness with a certain mathematical formula! The biggest feature is that it can be arbitrarily shaped, which can highlight personality. At present, the market's very personal mobile power supply is basically a soft package. His advantages Currently, compared with the 18650, the security risk is lower, that is, the 18650 may explode, but the biggest problem of the soft pack is the increase in the package and the burning. In fact, that is good, in the long run, it is still soft! Of course, I am not saying that the 16850 is excluded. After all, this product has been used for ten years, and the technology is quite mature. Additional: 16850 is doing better, is Sanyo, Panasonic. Soft pack lithium batteries are more famous for ATL, BAK, Bungay, BYD and so on. Others include Ronda, Lishen, Huayuebao, Yiwei, Haopeng, Kunpeng, Meibai, Haiyang, Yaoan, etc. (Note, this is the name I can remember, it does not mean All, for reference only). 2. Protection board PCBA protection board is mainly to do a few things, over-charge and over-discharge automatic adjustment. We use such a metaphor that a person who does not eat too much is too hungry, and eating too much is not good for the body. Therefore, in order to ensure that the battery of the mobile power source does not reach two extremes, the protection board is designed to protect the battery from damage. For example, if the mobile power is full, the power is automatically turned off, which is the same as the charger protection of the mobile phone. In addition, the protection board has an important function, which is the conversion rate. For example, when the battery's nominal 5000mAh charges the user's equipment, it is not completely 100% converted. Your 1500mAh mobile phone battery, charged with 5000mAh mobile power, theoretically charged more than three times, but in fact may not be full. This is because the cell and the object during this charging process are resistive, which consumes a portion. As a result, the board acts in this role, minimizing internal resistance and optimizing IC line design for improved performance. For specific details, this requires knowledge of the IC or electronics. A good protection board, according to the introduction of the industry, can achieve more than 90%, while the average is about 80-85%. The estimate of the difference is only about 70%. 3. Weight difference The appearance and weight of the mobile power supply is one of the most important considerations for many users. The beautiful and stylish appearance is not only pleasing to the eye, but also adds a lot of color to everyday use. The compact body weight is relatively light, the portability is improved, and the user can carry it conveniently in daily activities, increasing the practicality. At present, there are two kinds of materials for the mainstream mobile power products on the market, which are plastic materials such as plastic or fireproof material ABS+PC, and all aluminum or aluminum alloy materials. Plastic shells are generally treated with piano paint to increase the aesthetics and comfort, and the weight is relatively light; the metal shell is usually processed by brushing or matting, which adds metal texture and enhances the beauty and feel of the body. The weight will be slightly heavier. Generally speaking, the volumetric weight of the mobile power body is proportional to its core capacity. The larger the volume, the larger the volume and the heavier the volume. Otherwise, the lighter. The mass user chooses the mobile power source with the capacity of 5000mAh or so, which can basically guarantee the charging life of the mobile phone, and the volume is small, and the carrying is relatively light; the volume and weight of the mobile power source with the capacity of 10000mAh or more are relatively large, and the user is at When you are carrying it out, you can put it in the bag, which is suitable for users of tablet PCs; laptop users generally need to choose mobile power of about 20000mAh to ensure more durable power support for the device. Of course, the above is only a reference suggestion, in actual use. The user's equipment, charging times and usage methods are not the same. You still have to choose the capacity of the mobile power source according to your actual situation. Shenzhen Xcool Vapor Technology Co.,Ltd , http://www.xcoolvapor.com