Power in the ATX power supply
The concept of power is a physical quantity related to work (energy) and time (W), is the work done within a unit of time). In ATX power supply, there are several concepts related to power: apparent power, active power, reactive power and power factor.
This article will mainly introduce the active power and reactive power
Input power from AC 220V, will be converted by ATX power supply to the motherboard and other loads. Then is the conversion process 100% of the conversion? The answer is no.
Some may say that any circuit has its own wear and tear, a process that will certainly not be 100% converted. And the truth is. If we idealize the ATX power supply and think it has no circuit loss, will this conversion process be 100% conversion? The answer is still no.
For power conversion devices based on the electromagnetic induction principle, they are actually inductive loads (of course, there are capacitive and resistive loads corresponding to them). The 18 W power input from AC 20 previously measured, in addition to the power consumed by the built-in cooling fan and no-load resistor of the ATX power supply, There are actually two directions to the 18W power: one is the loss of any circuit has arrived at; the other is the magnetic energy stored in the magnetic field generated by the inductance in the inductive load (the various inductors in the ATX power supply).
To sum up, if from the perspective of conservation of energy. It is not strictly considered that the active power is the real power that can be used by the load such as built-in cooling fan, no-load resistor, motherboard and so on after the conversion of the ATX power supply, and the reactive power is the power occupied by the ATX power supply in the process of energy conversion. This part of the power is stored in the form of magnetic field energy in the internal inductor of the ATX power supply. The prominent performance of reactive power is that although this part of the power has been input from AC 220V to the internal ATX power supply, but it cannot be output to the load by the ATX power supply. Therefore, reactive power is meaningless to the load. In particular, this is not to say that reactive power is meaningless to the ATX power supply itself. On the contrary, reactive power is of great significance.
In electricity, reactive power is not useless power, it does not vanish out of thin air (energy is immortal), it just can't be used by load. The electrical nature of reactive power is that there is a phase difference between AC 220V current and voltage (which is out of sync).
Understanding the concepts of active power and reactive power is of little significance to maintenance, but it helps us to understand the functions of PFC.
It is not hard to understand that for an ideal ATX power supply,we hope that it can ideally complete the energy conversion process: that is, without considering the loss of the circuit itself, how much of the electricity it receives from the AC 220V input, the output of how much electricity can be provided at the output terminal. But the existence of reactive power actually means that the ATX power supply cannot convert the input power from AC 220V more efficiently (again, the effectiveness here has nothing to do with the loss of the circuit itself) to the electrical energy that the load can use.
This article is from Allicdata Electronics Limited