Single-stage single-switch PFC converter

Generally, a low-frequency energy storage capacitor CB is required inside the single-stage PFC converter circuit to balance the instantaneous power input and output, and filter out the second harmonic ripple, so that the waveform with twice the frequency of the mains power grid does not appear at the load end, and it has enough holding time. The voltage of this capacitor changes with the load current and the mains power grid voltage. For example, when the load is light, the output power of the converter decreases, and the energy input to the energy storage capacitor is greater than the energy taken out from the capacitor, causing the voltage on the capacitor to rise, and its peak value may be as high as 450V or more. It is necessary to use a high-voltage resistant energy storage capacitor, which increases the cost.

In summary, there are three forms of power factor correction for AC/DC power supplies with PF correction: passive PF correction, active two-stage converter, and active single-stage PFC converter. A qualitative comparison of these three technologies is shown in Table 1.

Table 1 Qualitative comparison of three PFC technologies

B. Sharifipour et al. also gave a comparative evaluation of three 100 W PFC technologies, see Table 2.

Table 2 Comparative evaluation of three 100 W PFC technologies

As can be seen from Table 2, the cost of an active single-stage PFC converter of about 100 W is lower than that of an active two-stage PFC converter, it uses fewer components and has a higher efficiency.

Since the 1990s, the international power electronics technology and industry have proposed many active single-stage PFC converter solutions. The most basic and most attractive typical single-stage PFC converter is introduced below, which is called integrated PFC rectifier-regulator, which is a single-stage single-tube PFC converter.