Power Factor Correction AC/DC Switching Technology

Generally, a high power factor (PF) AC/DC power supply consists of two stages: a pre-power factor corrector is added before the DC/DC converter, which requires at least two main switching tubes and two sets of control drive circuits. For low-power switching power supplies, the overall efficiency is low and the cost is high.

When the input power factor is not required to be high, a low-power AC/DC switching power supply is formed by combining a PFC and a converter circuit. Only one main switch tube is needed to correct the PF to above 0.8, which is called a single-stage (Single Switch Single Stage, S4) PF correction AC/DC converter. For example, an isolated S4PF correction AC/DC converter, the front power factor corrector uses a Boost converter running in DCM, and the main circuit of the rear voltage regulator is a flyback converter, which runs in CCM or DOM; the two-stage circuit shares one main switch tube. Of course, if active clamping or other soft switching technology is added, an auxiliary switch tube is also needed, which is called a single-stage (Single Stage, S2) isolated PF correction soft switching power supply.