What is PFC?
PFC (Power Factor Correction) power factor correction is mainly to improve the ratio of the effective power to the apparent power at the AC input of the power supply. Generally, the power factor of the model without PFC line is only 0.4~0.6 at the input end, while that with active PFC line can reach more than 0.9. The correlation formula is as follows: Apparent power = input voltage x input current (VA) effective power = input voltage x input current x power factor (W)
From the point of view of environmental protection: the power plant of the electric power company must generate electric energy greater than the apparent power, so that its generator set can stably supply the market electric energy demand, and the actual use of electric energy is the effective power. If the power factor is 0.5, it means that the generator set generates more than 2VA of electricity to fully supply the demand of 1W of electricity, and its energy operation efficiency is poor. Conversely, if the power factor is improved to 0.95, as long as the generator set of the power company generates more than 1.06VA of electricity, there is no problem in supplying 1W of electricity, and the energy operation efficiency is better.
Active PFC can be divided into single-stage PFC and dual-stage PFC according to the line structure. For comparison, please refer to the following table.
PFC Architecture Advantages Disadvantages Application Limitations
Single stage PFC low cost
Simple line
Low power efficiency High Ripple is too large
The feedback is not easy to adjust and affects the PF 1. No Hold up time directly affects the output of the AC power supply terminal change
2. Higher Ripple current is easy to affect the life of LED lamps (direct drive
use)
3. The feedback response is slow, and the load characteristic has a great influence
Dual Stage PFC High Power Design
Good PFC characteristics
Feedback compensation is easy to adjust
Good load characteristics, high cost
Complicated circuit Same as general power supply, it can be used in most environments, no special restrictions
