What does this sampling circuit mean?

灞波儿奔

What does this sampling circuit mean? [Copy link]

There is an AC voltage sampling circuit between the live wire and the neutral wire. The
AC voltage differential sampling between the ground wire and the neutral wire is directly performed. What is the function of this sampling? Insulation? Can any teacher give an analysis?

maychang

The function of this sampling circuit is to prevent large common-mode voltage from damaging the op amp.

Note that the resistance of the differential circuit connected to the mains is as high as more than 20 megohms.

lkh747566933

Obviously, the N or neutral line voltage is directly collected. Of course, a large resistor must be connected in series, otherwise the voltage will be raised and the op amp cannot withstand it.

灞波儿奔

lkh747566933 posted on 2023-10-12 18:03 It is obvious that the N or neutral line voltage is directly collected. Of course, a large resistor must be connected in series, otherwise the voltage will be raised and the op amp cannot withstand it.

The directly collected N is the zero line voltage

Meaning single phase voltage detection circuit?

maychang

灞波儿奔 posted on 2023-10-13 13:06 Does the directly collected N, that is, the neutral line voltage, mean a single-phase voltage detection circuit?

Two input terminals, one connected to N and the other connected to PE. N is the neutral line and PE is the ground line. Normally, the voltage between the neutral line and the ground line is very small, at most a few V. But in the case of a fault, the voltage between the neutral line and the ground line may be as high as hundreds of V. The purpose of this circuit may be to detect line fault conditions.

dyjccx

High-impedance differential sampling converts high voltage into low voltage and limits the current. That is, the output after the op amp can be considered a safe voltage, but it also depends on whether the op amp power supply is on the dangerous side!

lkh747566933

maychang posted on 2023-10-13 17:41 Two input terminals, one connected to N and the other connected to PE. N is the neutral wire and PE is the ground wire. Normally, the voltage between the neutral wire and the ground wire is very small, at most several V. But...

I think what you said is correct. This should be the principle. When the pressure difference reaches a certain value, an alarm signal will be issued.

dabiaoke

This should be the zero-ground voltage detection. Generally, if there is pe, the input should be connected to the y capacitor. If pe is defined as absolute 0V, n is 110V. When the voltage insulation fails or other situations occur, protection can be achieved based on the zero-ground voltage.