Power factor corrector with high power factor at low load or high mains voltage conditions

摘要

A power factor corrector raises power factor at low loads or high mains voltages by having the a greater amount of current delivered to the load during the falling time of the absolute value of the mains AC voltage than during the applicable rising time. It achieves this by increasing the switch-on time of a control switch during the falling time so that the majority of the switch-on time during a mains period occurs during the falling time. This may involve using a timing voltage increasing over a period within each half mains cycle to increase the switch-on time of conversion cycles in the falling time. This may also involve shifting the power conversion in time domain during each half mains cycle so that a majority of the time occurs during the falling time.