PIC16F18856中的过零检测器只能与电源输一起工作吗

您好，请您确认，PIC16F18856内的零交叉检测器只能与电源输入（如附图和LTSPICE模拟）一起工作，如果还有一个电阻从ZCDXin引脚接地？如果电阻器接地不存在，则PIC16F18856内部的电流源将不工作，因此不会检测到零交叉……[电流源和电流汇内的微电路必须交替工作（交替地），以便零交叉检测。PIC16F18856数据表第316页的第21.2部分清楚地表明，零交叉检测既需要内部电流源，也需要内部电流接收器，在微电路内，交替操作。如果没有操作，则不会有过零检测。因此，电阻接地（R5在附加的示意图中，对于零交叉检测是必要的）。您同意吗？PIC16F18856数据表中的示意图显示了AC源和微控制器都被引用到相同的“地”的情况。但是，随着AC电源设置的附加示意图和模拟，这种情况并不普遍…因此，电阻接地是必要的（即从ZCDXI引脚到地面）……你同意吗？PIC16F18856 DATHEHETTP//WW1.Microchip…COM/…EVICEDOC/4001824A.PDF



      以下为原文

    Hello,

Please can you confirm that the Zero Cross Detector inside the PIC16F18856 can only work with a mains input  (as in the attached schematic and LTspice simulation) if there is also a resistor to ground from the ZCDxIN  pin? (R5 in the attached schematic).

If the resistor to ground is absent,  then the current source internal to the PIC16F18856 will not operate, and therefore zero cross will not be detected….-[Both current source and current sink inside the micro must operate (alternately) in order for zero cross detection to happen].

Section 21.2 of page 316 of the PIC16F18856 datasheet makes it clear that the zero cross detection needs both the internal current source, and also the internal current sink, inside the micro, to operate alternately. If one never operates then there will be no zero cross detection.
As such, the resistor to ground (R5 in the attached schematic, is necessary for zero cross detection).
Do you agree?

The schematic in the PIC16F18856 datasheet shows a situation where the AC source and the microcontroller are both referenced to the same  “ground”. But with the AC Mains setup of the attached schematic and simulation, this situation is not prevalent…and therefore the resistor to ground is needed (ie from ZCDxIN pin to ground)…do you agree?

PIC16F18856 datasheet
http://ww1.microchip.com/...eviceDoc/40001824A.pdf
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