First of all, the nominal voltage of the general power supply refers to the voltage of the open-circuit output, that is, the voltage when there is no external load and no current output, so it can also be understood that this voltage is the upper limit of the output voltage of the power supply.

In the case of using active voltage-stabilizing components inside the power supply, even if the mains voltage fluctuates, the output is a constant value. Like small transformers on the market, such as Walkman and other power supplies, if the mains voltage fluctuates, The output of the power supply will also fluctuate accordingly.

Generally speaking, the real no-load voltage of ordinary power adapters is not necessarily exactly the same as the nominal voltage. Because the characteristics of electronic components cannot be completely consistent, there is a certain error. The smaller the error, the higher the consistency requirements for electronic components. , the production cost is high, so the price is also more expensive.

In addition, regarding the nominal current value, any power supply has a certain internal resistance, so when the power supply outputs current, a voltage drop will be generated internally, resulting in two things, one is to generate heat, so the power supply will be hot, the other One is to cause the output voltage to drop, which is equivalent to internal consumption.