Power Factor Correction (PFC) is a method of compensating for the lagging power factor seen in many AC power supplies. PFC improves overall system efficiency by reducing energy consumption and reducing the amount of electromagnetic interference (EMI) generated. LED power supplies can be classified as those with PFC and those without PFC.

A power supply without PFC draws an input current that lags behind the input voltage and is typically lower than what is needed by the load. As a result, this type of power supply has a low power factor and a high total harmonic distortion (THD). THD produces additional higher frequency harmonics that can interfere with other electronic systems. As a consequence, power without PFC wastes energy, produces excessive heat and noise, and can lead to interference to other electronic equipment in the network.

On the other hand, a power supply with PFC compensates for the lag in the input current by shaping it to the shape of the input voltage (in-phase) and thus producing a power factor that is almost equal to 1. The PFC-enhanced power supplies draw a constant current from the AC line, effectively eliminating harmonic currents from the line.

LED power supplies with PFC have several benefits, including reduced energy consumption, lower EMI, and better overall system efficiency. They also tend to be more durable, more reliable, and able to operate in a wider range of temperature and voltage conditions.

In summary, power supplies with PFC are an advanced technology that can improve the performance and efficiency of LED lighting systems. Power supplies without PFC can be less efficient, and in some circumstances, may interfere with other electronic devices. As a result, it's recommended to choose LED power supplies with PFC to ensure better energy efficiency, lower EMI, and other benefits.