Resonant Cavity Insulation Resistance Detection Circuit

The patent introduces a resonant cavity as an intermediary component between the alternating-current signal source and the battery. The resonant cavity includes a capacitor and inductor that create a resonant effect at a specific frequency, allowing the system to operate in a resonant state where the impedance characteristics are stabilized and less sensitive to component tolerances. This intermediary resonant structure mediates the interaction between the signal source and the battery, reducing the direct impact of capacitor value deviations and parasitic capacitance on measurement precision while maintaining fast detection speed.

The patent changes the operating parameters by introducing a resonant frequency condition. Instead of relying on precise knowledge of the capacitor value across all frequencies, the system operates at a specific resonant frequency where the relationship between voltage, current, and impedance is simplified and more robust. The resonant frequency ω satisfies ω² = 1/(LC), where L is the inductance and C is the capacitance. At this frequency, the reactive components cancel out, and the system's response becomes primarily resistive, reducing sensitivity to capacitor value variations and improving measurement reliability.

The patent converts the harmful effect of parasitic capacitance into a beneficial factor by operating in a resonant state. The parasitic capacitance, which normally causes measurement errors in the active injection method, is compensated for by the resonant cavity's capacitive and inductive components. When the system operates at the resonant frequency, the total reactive impedance becomes zero, and the parasitic capacitance is effectively canceled by the inductive reactance of the resonant cavity. This transforms the previously harmful parasitic effect into a neutral or even beneficial factor that stabilizes the measurement.