The nominal voltage of a 36w power adapter
is usually referred to as the open circuit output voltage, which is the value of the voltage without any load and no current output. Therefore, it can also be considered that this is the upper limit of the output voltage of the power supply. When active voltage stabilizing units or voltage reference elements are used in the power supply, the nominal voltage can be directly measured by using a dc voltmeter with high internal resistance. Even if the voltage fluctuates to a certain extent, the output is stable and constant.
Generally speaking, the real no-load voltage of common 36w power adapter
is not necessarily the same as the nominal voltage, because the characteristics of electronic components are not completely consistent. So there is an allowance of a certain error. The civil situation controls in 0.1% to 5% according to the needs of the use. The smaller the error, the more consistent the electronic components, the higher the cost in industrial production and, of course, the higher the price.
Next is the nominal current value of the power supply. Any power supply has a certain internal resistance, so when the power supply outputs current, it will generate a voltage drop inside, equal to the output current times the power supply internal resistance. This leads to two consequences. One is heat generation, and the other is the output voltage becoming nominal minus the internal voltage drop, resulting in a lower output voltage.
After considering the heat dissipation problem, the general design will limit current value. When the output current reaches the worth, the output voltage decreases to 95% or other proportion of the nominal voltage. Each manufacturer sets a higher or lower proportion according to the different need of load products. If the load resistance is too low, which leads to the output current more than nominal current, generally two things happen: one is the individual elements burned due to fever more than the heat dissipation capacity caused power supply is damaged, the other is a thermal design have allowance, only to further reduce the output voltage, and the too much reduction of the output voltage leads to the work failure.
The nominal voltage of a normal power adapter is likely to be different from the actual no-load voltage, mainly because the characteristics of the electronic components make it impossible for the two values to be exactly equal, and there must be some error between the two values.
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