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UCC28063A: ZCD lost (delayed) in bridgeless boost pfc in negtive half line cycle

Part Number: UCC28063A

I have used UCC28063A  in bridgeless boost PFC, but there are some problems. Pls see the figures below. 

Two auxiliary windings are used to acheve ZCD in positive and negative linecycle,respectively (see fig. 1), but the ZCD signal seems lost (or delayed) in the negative half line cycle (see Fig. 2).