Insulation Impedance Detection Circuit, Impedance Detection Method, Converter and Photovoltaic Centrifuge

An insulation impedance detection circuit, comprising:

• an impedance detection module connected between a positive terminal and a negative terminal of a direct-current bus to be detected, the impedance detection module comprising a first resistance bridge and a second resistance bridge arranged in parallel, wherein the first resistance bridge is composed of a first resistor R3 and a second resistor R4 connected in series, a connection line between the first resistor R3 and the second resistor R4 being grounded, and the second resistance bridge is composed of a third resistor R5, a fourth resistor R6, and a first switch S disposed between the third resistor R5 and the fourth resistor R6, the third resistor R5 or the fourth resistor R6 being grounded through the first switch S;
• wherein the first resistor R3 and the third resistor R5 are connected to the positive terminal of the direct-current bus to be detected through a first sampling resistor R1, the second resistor R4 and the fourth resistor R6 are connected to the negative terminal of the direct-current bus to be detected through a second sampling resistor R2, each of the first sampling resistor R1 and the second sampling resistor R2 being provided with a voltage sampling chip, and the impedance detection module is configured to calculate an insulation impedance value of the direct-current bus to be detected according to voltage values of two sampling resistors before and after switching of the first switch S.