Ni-MH batteries

　　Working principle, circuit diagram and PCB schematic of mobile power supply

　　Fed up with the short standby time of smartphones, power banks are hugely popular. In addition to the casing of mobile power supplies, how much do you know about mobile power supplies? If you are an engineer, you must not miss the sharing of the working principle of mobile power, components of mobile power, circuit diagram of mobile power and PCB schematic diagram of mobile power. Maybe you can get inspiration from it and make a finished mobile power supply yourself!

　　How mobile power works

　　The power bank is not a disposable device, it can be used repeatedly hundreds of times. So when the power of the mobile power supply is used up, we must charge the mobile power supply. The principle is the same as charging a mobile phone. Connect to a 5V USB computer interface or USB charger to charge the mobile power supply. Therefore, there must be a charging management system inside the mobile power supply. The charging management system can automatically adjust the charging current according to the voltage of the lithium battery. The processes include: precharging, constant voltage charging, and float charging, etc.

　　Various components of mobile power supply

　　A mobile power supply is a portable device that integrates power storage, voltage boosting and charging management. The storage medium generally uses lithium battery cells, because lithium battery cells are relatively small in size, have large capacity, have wide market circulation, and are moderately priced, so they are widely used in digital products. The voltage of lithium battery is between 2.7-4.2V, and the voltage decreases as the battery capacity decreases. The voltage of 2.7-4.2V cannot directly charge other digital products, because the lithium battery voltage of digital products is also 2.7-4.2V, and voltages of the same potential cannot be charged. Therefore, when a mobile power supply outputs electric energy, it must have a voltage boosting system to boost the 2.7-4.2V lithium battery voltage to 5V, so that it can charge other digital products, such as mobile phones, MP4s, tablets, PSPs, etc.

　　Power battery:

　　Commonly used ones include polymer lithium batteries, 18650 lithium batteries, and AAA nickel-metal hydride batteries.

　　Polymer battery: standard voltage 3.7V, many shapes, customizable, large capacity, high quality and low price, widely used, such as: mobile phones, MP4, portable speakers.

　　18650 lithium battery: standard voltage 3.7V, small size, large capacity, standard voltage 3.7V, mainly used in high-end products such as notebook computers.

　　AAA NiMH battery: standard voltage 1.2V. Capacity is relatively small. It should be widely used, household appliances, gamers, etc.

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