How to calculate the charge quantity of mobile phone charger manufacturer? In fact, a lot of people don’t notice that we don’t need to calculate any charge when using a phone charger. But occasionally, let’s share how to calculate the power of a phone charger? 1. The output of a mobile phone charger is usually direct current. You can use the formula p = Ui, which is maximum output power = rated output voltage × maximum output current. The unit of voltage is volt, the unit of current is ampere, and the unit of power is watt. If the unit of current is Milliamperes, the unit of power is milliwatts. 1A = 1000 ma. Figure 2. The charger is not a pure resistive load, and the power factor is not 1, so the formula can not be used to calculate the input power. The input power should be p = USPHICOI. Figure 3. The input current of 200 Ma is the maximum input current (usually 200-300 ma) and not the actual input current, which represents the minimum input voltage at full load operation (rounded to a small margin) . The working voltage range of power supply is generally 100 ~ 240V, the actual design is 90 ~ 265V. Figure 4. AC, 220V and 200MA ARE RMS because the AC input is connected to the bridge and the current is non-linear, the direct multiplication of RMS voltage and current does not equal the effective power (times the power factor, usually measured as 0.3-0.5 for small power sources with no power factor correction) . The most convenient way to measure input power is to use a power meter.The energy efficiency of mobile phone charger is 70% ー80% , the specific index is related to the output power. The simple calculation is as follows: 5v1a power supply is more than 73.623% efficient according to the six energy efficiency requirements of the United States, more than 73.773% efficient according to the fifth edition of the European Union, and more than 78.704% efficient according to the six energy efficiency requirements of the United States, 5v1a power supply: Output Power: 5V * 1A = 5w efficiency (based on the above calculation) as required by the EU 5th edition. Figure 6. As a rule of thumb, if the AC input active power is 5w0.74 = 6.757W and the power factor is 0.4, then the AC input apparent active power is 6.757W0.4 = 16.892va at the minimum input voltage, the effective value of the input current is 16.892V/100v = 168.92Ma, and the remainder is 20% . In other words, the main problem is that the difference between the input power and the output power is so large because the input power is wrong (at 100 volts) and the power factor * Efficiency conversion ratio is less calculated.