It is normal for a three-terminal voltage regulator chip (such as the 7805) to heat up during operation. These voltage regulator chips are usually linear voltage regulator circuits, and the heat output of the regulator tube (already integrated in these chips) depends on two parameters: the pressure difference of the regulator tube and the current flowing through the regulator tube. Therefore, the heating power of the three-terminal voltage regulator chip can be basically calculated by the following formula: P=(UI-UO) In formula I, Ui is the input voltage, Uo is the output voltage, I is the output current (or input current, the output current and the output current of the linear power supply should be basically equal, the input current is slightly greater than the output current), P is the dissipated power of the device itself. It can be seen from the formula that it is normal for the three-terminal voltage regulator chip to heat up during operation.