Why can't the chargers of small home appliances be made universal?

Why can't the chargers of small home appliances be universal? The chargers of various small home appliances are not universal, because different small home appliances have different internal circuits and working principles, and the types of rechargeable batteries inside the appliances (for example, some use lithium batteries, use nickel Hydrogen battery) and voltage may also be different, so you can not choose a universal charger for various small appliances. Let's take a look at the charging circuits of several common small home appliances. The rechargeable knife uses a 1.2v Ni-MH battery as a power source to drive a small motor. The charging circuit of the shaver is actually a simple low-power switching power supply. The AC220V voltage is converted into high-frequency alternating current through a single-tube oscillation circuit, and after being rectified by a high-frequency isolation transformer and diode FR102, the 1.2v Ni-MH battery is charged. LED is the charging indicator, and S is the power switch of the shaver. The charger mentioned by the questioner, as shown in the picture above, is not actually a charger because there is no rechargeable battery in the charger. Hand warmer heats its internal heat storage data through an external power supply. After the power is off, the heat storage data slowly releases heat to warm hands. The internal circuit of this charger is shown in the figure below. The AC220V alternating current is directly applied to the heating wire end of the warm hand treasure through the thermostat to make it hot. In other words, this charger outputs AC high voltage. And for all kinds of charging small desk lamps and flashlights, they often choose 4v batteries as the power source. The charging circuit of this kind of small electrical appliances chooses the resistance-capacitance step-down circuit shown in the figure above. The property is constant current charging. After the 4V battery is rectified through the step-down current limiting of the input terminal 1 of the capacitor F/400V and the rectifier bridge, the AC220V can be charged. Through the above several circuits, it can be seen that different small home appliances have different internal circuits and working principles, and the built-in rechargeable batteries and voltages are also different, so it is difficult to design a charger suitable for various small home appliances. Assuming that the cost is not considered, the internal circuit of this charger plan is more complicated, and the failure rate of the new product is very inconvenient to use, because the output port of this universal charger, the user has to choose the appropriate charging port when using it. The wrong charging port selection may damage the appliance. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Analysis of the four major advantages of 21700 lithium batteries