Power factor correction by measurement and removal of overtones

摘要

A power factor correction circuit (42/44) responsive to an input power supply signal at an input supply voltage (V_AC) that varies largely sinusoidally with time at a fundamental supply frequency contains regulator/control circuitry (60, 62, and 64) for measuring and removing overtones (I_LDm or I_FWRm) in the input supply current (I_LD) or in a rectified form (I_FWR) of the input supply current. Each overtone is expressible as the product of an amplitude component (I_m) and a sinusoidal function (I_m sin [(m+1)ω_ACt]) that varies with time at an integer multiple of the fundamental supply frequency. The regulator/control circuitry measures an overtone by determining the overtone's amplitude component. After generating an adjustment factor (S_ADJ) largely as the product of that overtone's amplitude component and an associated sinusoidal function, the regulator/control circuitry adjusts the input supply current or its rectified form by an amount corresponding to the adjustment factor for each measured overtone.