Power factor (PF) is a number between 0 and 1 that indicates how well energy is transmitted from input to output of a sys- tem. It can be described by average power (PAVG), RMS voltage (VRMS), and RMS current (IRMS):
Or by distortion factor (KDIST) and displacement factor (KDISP):
With a purely resistive system, PF = 1. The addition of reactive elements necessary in any converter, such as EMI filters and energy storage, will induce some amount of displacement (phase shift between the input voltage and input current). The addition of switching devices will also create distortion (ener- gy present in the harmonics relative to the switching frequen- cies). These non-idealities decrease the PF towards zero.
Active power factor correction attempts to make the input impedance look as resistive as possible to the power source. Since the output of the converter is usually a regulated voltage or current, there is a need for large energy storage elements to remove the twice line frequency (100Hz or 120Hz) ripple. A power factor control architecture, as shown in Figure 2, has very little capacitance at the input. Instead, the twice line fre-
Power factor (PF) is a number between 0 and 1 that indicates how well energy is transmitted from input to output of a sys- tem. It can be described by average power (PAVG), RMS voltage (VRMS), and RMS current (IRMS):Or by distortion factor (KDIST) and displacement factor (KDISP):With a purely resistive system, PF = 1. The addition of reactive elements necessary in any converter, such as EMI filters and energy storage, will induce some amount of displacement (phase shift between the input voltage and input current). The addition of switching devices will also create distortion (ener- gy present in the harmonics relative to the switching frequen- cies). These non-idealities decrease the PF towards zero.Active power factor correction attempts to make the input impedance look as resistive as possible to the power source. Since the output of the converter is usually a regulated voltage or current, there is a need for large energy storage elements to remove the twice line frequency (100Hz or 120Hz) ripple. A power factor control architecture, as shown in Figure 2, has very little capacitance at the input. Instead, the twice line fre-
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