Hello,
I was doing some reverse-engineering to a board and I came up with the circuit attached. I have depicted the current transformer with current source I1.
I want to understand how this circuit process the current transformer signal. What I can see is that the TVS diode D1 is for protection, followed by two Pi filters. But, what's the purpose of C5? I don't understand what happens after the burden resistor R1. There's a RC network at the non-inverting input of U1, does this cause a delay? At last, what's the function of the capacitor C7 which looks like it's in the positive feedback of U1. I think U2 and U3 non-inverting amplifiers for both positive and negative half cycles, right? I also see a DC offset of 1.65V added to the CT signal.
I was doing some reverse-engineering to a board and I came up with the circuit attached. I have depicted the current transformer with current source I1.
I want to understand how this circuit process the current transformer signal. What I can see is that the TVS diode D1 is for protection, followed by two Pi filters. But, what's the purpose of C5? I don't understand what happens after the burden resistor R1. There's a RC network at the non-inverting input of U1, does this cause a delay? At last, what's the function of the capacitor C7 which looks like it's in the positive feedback of U1. I think U2 and U3 non-inverting amplifiers for both positive and negative half cycles, right? I also see a DC offset of 1.65V added to the CT signal.
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