Design and simulation of DC current comparator demodulation circuit

The demodulation circuit is a major part of DC current comparator (DCC), of which performance directly influences the accuracy, sensitivity and noise of whole system. Separately describe the working principle of two demodulation methods, based on which the corresponding circuits were designed; experiments and simulation studies were carried out. The research results show that both methods can realize the function of converting the even harmonic signals characterizing the measured DC current to the corresponding DC voltage. The important advantage of peak difference demodulation is that it can demodulate all even harmonic signals. A high detection gain will be obtained accordingly, which is favorable to increase sensitivity. But the ripple of secondary current is large. Narrow band characteristics of phase sensitive demodulation are beneficial for reducing the system noise level; the ripple of secondary current is very small. As only second harmonic is demodulated, it is necessary to satisfy the best condition to achieve high sensitivity.