Excellent design strategy for qualified mobile power supply

　　1. Analysis of the main chip of mobile power supply

　　1. Lithium battery management IC: At present, the domestic charging management system is relatively mature. The intelligent IC monitors the entire charging process and performs the three-stage charging functions of pre-charging, constant current and constant voltage of lithium batteries. The mainstream management ICs include Tuowei TP4056, Taiwan Dexin EUP8027, etc. The charging time of 5000maH is about 8 hours.

　　2. MCU: The intelligent control system on the PCB board prevents the device from being damaged by unstable current and voltage shocks during charging; it can control the charging and discharging of the product, and provide charging protection, discharge protection, temperature protection, and leakage protection. Multiple protections such as overload protection and short circuit protection make the product performance safer and more stable, and extend the service life of the product itself, while also preventing unstable output from causing damage to the mobile phone. Automatically identify mobile phones and a variety of digital products, support charging of various brands of smartphones and various tablets, and are compatible with charging of other digital electronic products with USB 5V input. Currently, the more common brands and models include STM8S003F3P6, Ten Speed, Songhan, HOLTEK, Haier HR6P61, and Xinhai Technology.

　　3. SMD boost IC : The voltage of the mobile power battery is 3.7V, while the output voltage is 5.0V. The power needs to pass through the boost circuit to be output. In the process of boosting, part of the power is lost due to heat in the circuit, so there is a certain difference between the actual output power and the battery output power. The ratio of the two is called the conversion rate of the mobile power. At present, the conversion efficiency of domestic technology varies, generally between 75-85%. Some powerful manufacturers also adopt a more costly solution and independently develop circuit design, and the actual conversion rate can reach more than 90%. Mobile power system manufacturers are accelerating the introduction of high-current DC-DC converters. Aiming at the huge mobile power market opportunities, power IC suppliers such as Zha Neng, Yuanxiang, O2Micro, MPS, Richtek and Zhixin have all started to develop or launch high-current DC-DC converters to help system manufacturers develop mobile power products with faster charging speeds.

　　4. SoC: Some domestic manufacturers are inclined to launch single-chip solutions to achieve the basic functions of mobile power with one chip. Zhishang Technology completely replaces the current MCU charging management IC boost IC solutions on the market with a ZS6366 chip; and provides Turnkey solutions for major solution companies to minimize the entry threshold. Xinwang Microelectronics MCU integrates charging management, synchronous rectification boost discharge control, power detection, various overcharge and over-discharge short-circuit protection, automatic load identification, lighting and LED/LCD display driver function modules, with built-in high-precision reference source, combined with peripheral simple hardware circuits, can better solve problems such as reverse charging. Xinhai Technology Co., Ltd. SOC chip CSU8RP3119 is used in single-chip solutions for mobile power products. By using the chip's built-in two-way high-speed PWM (16M) and four-way high-performance ADC (12bit, dead zone less than 3mV) and unique reference source digital correction patented technology, CSU8RP3119 can achieve a synchronous rectification mobile power supply with an efficiency of up to 93% without the need for other peripheral ICs. Under 2.1A output conditions, the efficiency is still higher than 88%.

　　2. Importance of circuit protection board

　　When it comes to the battery cell of a mobile power bank, many people always judge a person by his capacity. However, in the complex mobile power market environment and the premise that no unified standard has been formulated, although capacity is important, the quality and safety of the battery cell are more critical. At present, mobile power bank batteries generally use 18650 lithium-ion batteries and lithium polymer batteries. It is best to choose polymer batteries, which are safer and have a relatively long life. At present, Shenzu, a professional mobile power bank with polymer batteries, ranks high. All models are polymer batteries with queryable numbers, and the capacity of the same volume is 15% higher than that of ordinary polymer batteries, and there are no safety issues.

　　First of all, compatibility.

　　Differences in scope of application - not every mobile power bank can charge your phone properly. Let's first understand some of the requirements and parameters for charging smart devices such as mobile phones and tablets.

　　In addition, some domestic mobile phones have charging currents of 0.8A and 0.7A, which means that different devices have different current requirements. If the device is not charged according to the required parameters, there are safety risks and even permanent damage to the device.

　　If the resistors in the mobile power supply are different from those in the circuit board, or if they have not passed the national inspection, the quality will be difficult to guarantee. The circuit board of a mobile power supply with poor workmanship usually only has a simple boost system, which simply increases the battery voltage from 3.7V to 5V without any protection circuit.

　　Such a crude circuit has unstable current output, which may explode the battery of our digital device, or cause the circuit board inside the mobile phone to overheat and cause a short circuit, thus burning the circuit board.

　　The second is overload, overvoltage and overtemperature protection.

　　The precision boost IC can provide an efficient and safe automatic current matching solution. When the load is connected to the fast charging port, the boost IC can immediately detect the maximum acceptable current of the load and then provide the optimal output current for the load. This can protect the battery from being damaged by excessive current to the maximum extent while providing a fast charging mode for the load.

　　In fact, during the use of mobile power, if the usage method and environment are inappropriate, it may cause unexplained overcurrent, overvoltage and short circuit. A well-made mobile power can have a built-in temperature sensing chip. When the battery cell temperature exceeds the preset value, the circuit is closed, thereby effectively protecting the safety of the mobile power and rechargeable battery through the internal protection circuit.

　　In addition, there is over-discharge protection for the mobile power supply.

　　The mobile power circuit board equipped with a voltage intelligent detection system can achieve such a function - when the mobile power voltage is lower than its over-discharge voltage detection point, the over-discharge protection will be activated and the discharge will be automatically stopped to prevent over-discharge from affecting the life of the mobile power and even burning digital products such as mobile phones.

　　Finally, there is the issue of power conversion rate.

　　Power conversion rate: that is, the percentage of the standard capacity of the battery and the full output when actually charging mobile phones and digital devices. The quality of mobile power mainly depends on the energy conversion rate. Good quality mobile power can generally reach about 80%, ordinary ones are about 70-75%, and poor ones are even only 30%. If the conversion rate is lower than 75%, it means that the mobile power line loss is large and the heat generated by the battery itself is also large.

　　The most important factor affecting the conversion rate of a mobile power supply is the "mobile power supply protection board", so if the PCB circuit board of a mobile power supply adopts good workmanship and design, and the battery used is also excellent, and it has a solid protection circuit, then the quality of this mobile power supply is guaranteed.

　　As smartphones consume more and more power, and most smartphone batteries are non-removable, a large-capacity and easy-to-carry mobile power bank has become a must-have electronic product for people to travel with. However, recent frequent safety accidents involving mobile power banks have forced consumers and engineers to re-examine the design and development of mobile power banks. How much do you know about the internal structure of mobile power banks?