| 摘要 |
Methods for converting alternating current into direct current, using a pulse width modulated (PWM) converter (10) connected to a source (12) of alternating current are disclosed. The methods include determining the occurrence of the notch portion of the input current and generating control signals, in response to determining the notch portion for switching the plurality of bi-directional switches (20, 22, 26, 28, 32, 34) contained in the PWM converter so that the input current is modified only during the notch portion. It is preferred to modify the input current to a generally sinusoidal shape so that the total harmonic distortion of said input current is between five and ten percent. The step of determining the occurrence of the notch portion can include sensing the input voltage, preferably determining when said input voltage reaches a desired level, or sensing the input current to determine when it reaches a desired level. It is especially preferred to only switch the bi-directional elements (20, 22, 26, 28, 32, 34) during the notch portion. |
