Power Factor of Power Adapters

　　Power factor is an important parameter in the performance evaluation of power adapters. It represents the ratio of real power (the power actually used by the load) to apparent power (the product of the root - mean - square voltage and current).

　　A low - power - factor power adapter can cause several problems. When the power factor is low, the electrical current drawn from the power grid contains a significant amount of reactive power. This reactive power does not contribute to the actual work done by the device but still occupies the capacity of the power grid. As a result, it increases the burden on the power grid, leading to higher energy losses and reduced power - grid efficiency.

　　In the case of power adapters, especially those with non - linear loads (such as switching power adapters), the input current waveform is often distorted, resulting in a low power factor. To address this issue, power - factor - correction (PFC) techniques are employed. There are two main types of PFC: passive and active.

　　Passive PFC uses inductors and capacitors to correct the power factor. It is a relatively simple and low - cost solution. However, its power - factor - correction performance is limited, and it can only achieve a power factor of around 0.7 - 0.8.

　　Active PFC, on the other hand, uses more complex electronic circuits, such as boost converters. Active PFC can achieve a much higher power factor, often close to 1. This significantly reduces the reactive power drawn from the power grid, improving the overall efficiency of the power system. Many modern power adapters, especially those designed for high - power applications or those required to meet strict energy - efficiency standards, are equipped with active PFC circuits to ensure a high power factor.

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Principle of Power Adapter

Power adapter is the core component of electronic devices