Insulation detection circuit and method

Abstract

The invention provides an insulation detection circuit and method, and the circuit comprises: a to-be-detected high-voltage power supply; a first voltage dividing circuit which comprises a first resistor R1 and a resistance value variable unit; a second voltage division circuit which comprises a second resistor R2 and a third resistor R3; a third voltage division circuit which comprises a fourth resistor R4 and a first switch S1; a first voltage acquisition unit which is used for acquiring voltage to ground of a middle point of the first resistor R1 and the resistance value variable unit; a second voltage acquisition unit which is used for acquiring the voltage to ground of the middle point of the second resistor R2 and the third resistor R3; and a processing unit which is connected with the first voltage acquisition unit and the second voltage acquisition unit, and is used for calculating the ground insulation resistance of the positive and negative electrodes of the to-be-detected high-voltage power supply according to the voltages acquired by the first voltage acquisition unit and the second voltage acquisition unit. After the technical scheme is adopted, errors of insulation detection calculation caused by voltage fluctuation of the to-be-detected high-voltage power supply can be avoided, and meanwhile, existence of a detection blind area can be avoided.

Description

technical field [0001] The invention relates to the technical field of insulation detection, in particular to an insulation detection circuit and method. Background technique [0002] The measurement of the insulation resistance of the positive and negative poles of the high-voltage power supply to the ground directly affects the safe operation of the high-voltage system. When the measured insulation resistance is lower than a certain safety value, it is necessary to disconnect the circuit in time to ensure safety. If the actual value is too small, it will cause the circuit to malfunction and disconnect the circuit, which is not conducive to the stable operation of the circuit. If the measured value of the insulation resistance is larger than the actual value, it will cause the actual insulation resistance to be lower than the safe value and not be discovered in time. , bringing security risks. See attached figure 1 , the existing insulation detection method is that the fi...

AI Technical Summary

Problems solved by technology

[0005] The problem with existing detection methods is that it is impossible to avoid voltage fluctuations when the high-voltage power supply is working with a load. To obtain an accurate insulation resistance value, it is necessary to ensure that the voltage cannot fluctuate between multiple switch openings and closings.

[0006] The existing high-voltage power supply to be tested, such as the high-voltage battery pack of an electric vehicle, when the electric vehicle is stationary, the power load (such as a motor, etc.) is not working, and the voltage of the high-voltage battery pack is basically stable. At this time, the insulation resistance can be accurately calculated. value; when the electric vehicle is working, the power load is working normally (such as the motor, etc.), the voltage of the high-voltage battery pack will fluctuate with the change of the power load (such as the speed of the motor speed, emergency stop, emergency start, etc.), and when the load is working The noise voltage introduced introduces errors to the measurement of insulation resistance. The greater the voltage fluctuation of the high-voltage battery pack, the greater the error of insulation resistance measurement.

[0007] At the same time, there is a blind area in the existing insulation detection. During the detection process, if the insulation resistance of the positive and negative poles of the high-voltage power supply to the ground changes at the same time and meets the corresponding conditions, the voltage at the sampling point will not change, and the insulation detection circuit cannot detect the change. insulation resistance

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