How long does it take to fill a smartphone? A few years ago, the number was just a few hours, but with the growth of smartphone charging power visible to the naked eye in recent years, this time can now be calculated in minutes. On February 28th, a well-known smartphone brand displayed a mobile phone product equipped with advanced fast charging technology on its official Weibo account, claiming that its charging power has reached 300 watts and can fully charge the phone battery within 5 minutes. Not only is the wired charging power rapidly increasing, but the wireless charging power of mobile phones has also increased by nearly 10 times compared to the early stage, reaching a maximum of 67 watts. In the process of embedding smart phones into people's lives step by step, the rapid development of mobile phone charging technology has played a role that cannot be ignored. With the rapid growth of charging power and the gradual popularization and upgrading of smart phones, mobile phones can achieve more and more functions, and their performance is becoming increasingly powerful. One of the immediate consequences of this is a significant acceleration in the speed of power consumption. In order to maintain the normal use of mobile phone functions, the battery capacity of mobile phones has increased from about 1000 mAh at the beginning to about 4000 mAh at present. Long range models can even exceed 5000 mAh. The significant increase in battery capacity has stimulated consumer demand for charging speed. In the era of "machine in hand", batteries that often require hours or even an entire night to "come back to life" cannot meet consumers' requirements for the charging speed of smartphones. Therefore, fast charging technology emerged as the times require and quickly gained the favor of users. Yan Huaizhi, director of the Institute of Network and Security at Beijing University of Technology, said in an interview with a reporter from Science and Technology Daily that although fast charging technology has been iterating in recent years, its basic principle is actually very simple. "Charging power is the product of voltage and current. To achieve fast charging, it is necessary to increase the charging power, either by increasing the voltage, or by increasing the current, or both simultaneously," he said. When smartphones first appeared, the charging power was mostly 5 watts, which is 5 volts (voltage) multiplied by 1 ampere (current). When fast charging technology began to take off, high current and low voltage schemes were widely adopted. With the voltage unchanged, the current was successively increased to 1.5 A and 2 A, and the charging power was correspondingly increased to 7.5 W and 10 W. However, the continuous improvement of current has higher requirements for charging wires. The original ordinary charging wires and plugs have been unable to carry higher current, and the development route of fast charging technology has also differentiated here. Some manufacturers have chosen to continue along the path of high current and low voltage, so they have upgraded their charging wires, such as adding charging interface contacts, installing IC chips, etc., increasing the current to 5 amperes, and increasing the charging power to 25 watts. Other manufacturers have shifted to the direction of high voltage and low current, increasing the charging voltage to 9 volts, 12 volts, and even 20 volts, increasing the charging power to about 18 watts. Yan Huaizhi stated that the two upgrade schemes have their own advantages and disadvantages, and the low voltage and high current schemes require higher requirements for wire and interface technology; The problem with high voltage and low current schemes is that their efficiency is low, resulting in high battery heat generation. But soon, as the phone's charging interface