Insulation detection circuit, detection method and battery management system

1. An insulation detection circuit, comprising:

a first voltage dividing module, wherein, one end of the first voltage dividing module is connected to a positive electrode of a power battery to be detected, and the other end of the first voltage dividing module is connected to a first isolation module and a second voltage dividing module respectively;

the second voltage dividing module, connected to a negative electrode of the power battery to be detected;

the first isolation module, connected to one end of a sampling module;

the sampling module, wherein, the other end of the sampling module is connected to one end of a signal generator;

the signal generator, wherein, the other end of the signal generator is connected to power ground, and the signal generator is configured to inject a signal at a predetermined frequency to the power battery to be detected; and

a processor, configured to calculate an insulation resistance value of the power battery to be detected according to a first sampled signal collected at the one end of the sampling module and a second sampled signal collected at the one end of the signal generator,

wherein the first voltage dividing module comprises a first resistor, one end of the first resistor is connected to the positive electrode, and the other end of the first resistor is connected to the first isolation module and the second voltage dividing module respectively;

the second voltage dividing module comprises: a second resistor, one end of the second resistor being connected to the other end of the first resistor, and the other end of the second resistor being connected to a first switch; and the first switch, connected to the negative electrode;

a resistance value of the first resistor is equal to a resistance value of the second resistor; and

the first isolation module comprises: a second switch, connected to the other end of the first voltage dividing module; and an isolation capacitor, connected to the second switch and the sampling module respectively.

2. The circuit according to claim 1 , wherein, the sampling module comprises a third resistor, wherein, the third resistor is connected to the first isolation module and the signal generator respectively.

3. The circuit according to claim 1 , wherein, the signal generator is a direct digital frequency synthesis (DDS) waveform generator.

4. The circuit according to claim 1 , wherein, a value of the predetermined frequency ranges from 0.1 Hz to 10 Hz.

5. The circuit according to claim 1 , wherein, the circuit further comprises:

a first sampling circuit, wherein, a first end of the first sampling circuit is connected to the one end of the sampling module, a second end of the first sampling circuit is connected to the processor, and the first sampling circuit is configured to collect the first sampled signal at the one end of the sampling module.

6. The circuit according to claim 5 , wherein, the circuit further comprises:

a first filtering module, connected to the one end of the sampling module and a second isolation module respectively;

the second isolation module, connected to the first sampling circuit and configured to isolate interference of the first sampling circuit on the first sampled signal.

7. The circuit according to claim 6 , wherein, the second isolation module comprises:

a first voltage follower, wherein, a first input end of the first voltage follower is connected to the first filtering module, and an output end of the first voltage follower is connected to a second input end of the first voltage follower and the first sampling circuit respectively.

8. The circuit according to claim 1 , wherein, the circuit further comprises:

a second sampling circuit, wherein, a first end of the second sampling circuit is connected to the one end of the signal generator, a second end of the second sampling circuit is connected to the processor, and the second sampling circuit is configured to collect the second sampled signal at the one end of the signal generator.

9. The circuit according to claim 8 , wherein, the circuit further comprises:

a second filtering module, connected to the one end of the signal generator and a third isolation module respectively;

the third isolation module, connected to the second sampling circuit and configured to isolate interference of the second sampling circuit on the second sampled signal.

10. The circuit according to claim 9 , wherein, the third isolation module comprises:

a second voltage follower, wherein, a first input end of the second voltage follower is connected to the second filtering module, and an output end of the second voltage follower is connected to a second input end of the second voltage follower and the second sampling circuit respectively.

11. A battery management system, comprising the insulation detection circuit according to claim 1 .

12. An insulation detection method, applied to the insulation detection circuit according to claim 1 , wherein, the method comprises:

calculating the insulation resistance value of the power battery to be detected according to the first sampled signal and the second sampled signal.

13. The method according to claim 12 , wherein, the calculating the insulation resistance value of the power battery to be detected according to the first sampled signal and the second sampled signal comprises:

acquiring a first voltage amplitude value of the first sampled signal and a second voltage amplitude value of the second sampled signal;

calculating a phase shift of the first sampled signal relative to the second sampled signal according to the first voltage amplitude value and the second voltage amplitude value; and

calculating the insulation resistance value of the power battery to be detected based on the phase shift, the first voltage amplitude value, the predetermined frequency and the second voltage amplitude value.