Insulation detection circuit of direct current bus

The insulation detection circuit comprises a balance bridge circuit and a non-balance bridge circuit, the first end of the balance bridge circuit is connected with a positive bus, and the second end of the balance bridge circuit is connected with a negative bus; the first end of the unbalanced bridge circuit is connected with the positive bus and the second end is connected with the negative bus; the midpoint of the balance bridge circuit and the midpoint of the non-balance bridge circuit are grounded; the balance bridge circuit comprises a first resistor and a second resistor which are connected in series, and the connection point of the first resistor and the second resistor is the midpoint of the balance bridge circuit; an upper bridge arm of the unbalanced bridge circuit comprises a third resistor and a first MOS tube which are connected in series, and a lower bridge arm of the unbalanced bridge circuit comprises a fourth resistor and a second MOS tube which are connected in series. The DC bus insulation