CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/CN2020/072238, filed on Jan. 15, 2020, which claims priority to Chinese Patent Application No. 201910037377.7, filed on Jan. 15, 2019, both of which are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present application relates to the field of new energy, in particular, to an insulation detection circuit, a detection method and a battery management system.

BACKGROUND

The use of electric vehicles to replace fossil-fueled vehicles has become a trend in the development of the automotive industry. The mileage, service life, and safety of use of battery packs are particularly important for electric vehicles. The battery pack is one of key parts of an electric vehicle, the safety of high-voltage electricity of the battery pack must be put into one of the first considerations of a power battery system. Therefore, the detection of insulation performance of the electric vehicle is an essential part of the design.

Currently, the main methods for detecting insulation resistance include high-frequency signal injection method and resistance voltage division method. When a detection system using the high-frequency injection method is adopted, the detection result of the insulation resistance value is likely to be affected by the distributed capacitance of the detection system, and the high-frequency signal causes interference to the direct current system, which results in a large error in the insulation resistance value. When the resistance voltage division method is adopted, the resistors connected in series reduce the insulation performance, and the high-voltage circuit will cause interference to the low-voltage circuit, which would also reduce the detection precision of the insulation resistance value. Therefore, improving the detection precision of the insulation resistance value is an urgent problem to be solved.

SUMMARY

Embodiments of the present application provide an insulation detection circuit, a detection method and a battery management system, which improve the detection precision of the insulation resistance value.

According to an aspect of the embodiments of the present application, an insulation detection circuit is provided, where the circuit includes:

a first voltage dividing module, where, 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, where, the other end of the sampling module is connected to one end of a signal generating module;

the signal generating module, where, the other end of the signal generating module is connected to power ground, and the signal generating module is configured to inject a signal at a predetermined frequency into the power battery to be detected; and

a processing module, 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 generating module.

In an embodiment, the first voltage dividing module includes a first resistor, where 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.

In an embodiment, the second voltage dividing module includes:

a second resistor, where, one end of the second resistor is connected to the other end of the first resistor, and the other end of the second resistor is connected to a first switch; and

the first switch, connected to the negative electrode.

In an embodiment, a resistance value of the first resistor is equal to a resistance value of the second resistor.

In an embodiment, the first isolation module includes:

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.

In an embodiment, the sampling module includes a third resistor, which is connected to the first isolation module and the signal generating module respectively.

In an embodiment, the signal generating module is a DDS waveform generator.

In an embodiment, a value of the predetermined frequency ranges from 0.1 Hz to 10 Hz.

In an embodiment, the circuit further includes:

a first sampling circuit, where, 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 processing module, and the first sampling circuit is configured to collect the first sampled signal from the one end of the sampling module.

In an embodiment, the circuit further includes:

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

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

In an embodiment, the second insolation module includes:

a first voltage follower, where, 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.

In an embodiment, the circuit further includes:

a second sampling circuit, where a first end of the second sampling circuit is connected to the one end of the signal generating module, the second end of the second sampling circuit is connected to the processing module, and the second sampling circuit is configured to collect the second sampled signal from the one end of the signal generating module.

In an embodiment, the circuit further includes:

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

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

In an embodiment, the third isolation module includes:

a second voltage follower, where, 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.

According to another aspect of the embodiments of the present application, a battery management system is provided, where the battery management system includes the insulation detection circuit according to the embodiments of the present application.

According to yet another aspect of the embodiments of the present application, an insulation detection method is provided, where the method is applied to the insulation detection circuit according to the embodiments of the present application and the method includes:

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

In an embodiment, the calculating the insulation resistance value of the power battery to be detected according to the first sampled signal and the second sampled signal includes:

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.

According to the insulation detection circuit, the method and the battery management system provided by the embodiments of the present application, the signal at the predetermined frequency is injected between the first voltage dividing module and the second voltage dividing module, which reduces the influence of the voltage fluctuation of the power battery on the signal between the sampling module and the first isolation module, thereby improving the accuracy and precision of the detection of the insulation resistance value.

