求助!L4981的PFC电路,输入电流在过零处出现畸变

boost升压型PFC电路,控制芯片为L4981,PFC电感约700uH,输出功率为300W.电路现在输出电压稳定,但输入电流在过零处出现畸变,且整个输入电流的波形近似三角波,而非正弦波,如图中所示.功率因数为0.988.将环路调遍了也不见改善.请大家帮忙看看是什么原因.谢谢!
输入电流波形
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CA-OUT脚波形
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