Modern high-frequency switching power supply to improve the input power factor

A passive filter

Passive filter is a filter inductor in series between the rectifier and the capacitor resonator filters,solar panel or access the mains input side. Its main advantages are: the circuit is simple, low cost, high reliability, EMI. The main disadvantages are: the volume weight is large, it is difficult to obtain the input power factor close to 1 (typically between 0.8 and 0.9 can be achieved), related to the operating performance and frequency, load changes, and the input voltage changes, the inductance and capacitance between the charge, the discharge current is large and so on.

2 Active Power Filter

Active power filter APF (Active P. Wer Filter) is the use of power electronic inverter and feedback technology, real-time measurement of the voltage and current waveforms of the nonlinear load, to provide the required load current harmonics to the electricity grid, Input current to compensate for the power inverter  grid, so close to a sine wave, reducing the electricity grid input current THD, and improve the quality of the mains power grid. APE power generally.

3 Active Power Factor Correction

Rectifier of Zan and load of indirect PFC converter (both DC / DC converter), the application of current feedback technology, the end of the input current iin waveform tracking sinusoidal AC input voltage waveform, iin nearly sinusoidal. So that the input current THD <5%, while the input power factor can be increased to 0.99 or higher. This technology applied to active power devices and feedback technology, so that the input current waveform is nearly sine wave from the narrow pulses status changes to improve the input power factor, it is called Active Power Factor Correction (APFC) active input current waveform shaping technology. The APFC power generally small, as AC / DC switching power supply, inverter, AC uninterruptible power supply (UPS), fluorescent lamp electronic ballasts and other input terminal of the power factor correction.

Its main advantages are: high input power factor, such as 0.97 to 0.99, even close to 1; city power grid tie inverter input current THD; wide input voltage range ( as 90 ~ 264 V AC) and broadband; small size, light weight; adjust the input current waveform, the current negative feedback, the output voltage can be kept substantially constant. The main disadvantages are: complex circuit, MTBF decline; costs (such as AC / DC switching power supply plus top-level APFC, will make the cost of a 15% increase); EMI; efficiency decreased slightly.