To guarantee robust operation of data center, power supply units for data center must produce a stable output voltage even under abnormal input voltage conditions such as voltage sag and input voltage loss. In order to achieve such stringent requirements, a precise and rapid detection of input voltage loss or voltage sag plays a crucial role. This paper presents an advanced control algorithm for bridgeless totem-pole power factor correction (PFC) in data center power supplies, where a novel AC input voltage loss detection is first proposed to achieve proper control of totem-pole PFC during unexpected input voltage drop and recovery within the hold-up time of the power supply. In this method, the rectifier signal of the input voltage is compared with a pre-defined voltage level, which then combines with a time counter to detect the abnormal input voltage condition. The proposed detection method can detect AC voltage loss as fast as 500us to ensure no high current spike or overcurrent occurs during the event. Secondly, 2-poles-2-zeros (2p2z) controller, rather than classic proportional-integral (PI) controller, is employed, where for the first time through a systematic and optimized pole–zero design of a digital 2p2z controller, it can simultaneously deliver fast transient response and high-quality input current shaping in a totem-pole PFC without the need of a low-pass filter or a notch filter in the control loop. Analysis and a series of simulation tests are carried out to compare the control performance of previously developed control methods and 2p2z controller. Experimental tests of 3.4 kW totem-pole PFC prototype verify the effectiveness of the proposed control scheme.
Trinh et al. (Thu,) studied this question.