4 Test result

I tested the proposed method on a 3.6kW totem-pole bridgeless PFC [2]. Figure 6 shows that when the AC voltage drops out, it comes back in 10ms at its peak. Channel 1 (blue) is the PFC input current waveform (I_IN), while channel 2 (turquoise) is the relay on and off control signal. Figure 7 is the zoom in at relay on and off. During the AC drop period, relay Q₅ remains on. C_BULK continuously delivers the stored energy to the load and V_OUT drops. After the AC voltage resumes, because the relay is on and V_AC > V_OUT, the re-rush current quickly rises. Once the re-rush current reaches a predefined current limit threshold (40A in this example), the relay turns off, and the re-rush current reduces to a very low value because of R_T. The relay only remains off for 10µs, then turns on again. The re-rush current rises once again. This entire process allows the limiting of re-rush current within the M-CRPS specification while still supplying substantial current to rapidly charge C_BULK. The waveform also shows that the non-re-rush current, where V_AC < V_OUT, is well controlled without large current spikes.

Figure 7 shows the second re-rush current rising up with a limited slope, which occurs because the PFC input impedance – including the electromagnetic interference filter impedance and printed circuit board trace impedance – limit the current rising slope. The magnitude of the second re-rush current does not exceed the 40A threshold in this example; therefore, the relay turns off only once. If the second re-rush current also exceeds the threshold, the relay will turn off again.