Insulation Detection Circuit for EV Battery Packs
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Solution Overview
Problem
Current insulation resistance detection methods for electric vehicle battery packs face inaccuracies due to interference from distributed capacitance and high-frequency signal injection, as well as reduced precision from voltage division methods, necessitating improved detection precision.
Innovation Solution
An insulation detection circuit with a first and second voltage dividing module, isolation modules, and a signal generating module that injects a low-frequency signal, utilizing a DDS waveform generator to reduce interference and calculate insulation resistance based on sampled signals and phase shift, thereby enhancing detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-frequency signal injection method is used for insulation resistance detection, then detection speed is improved, but detection precision deteriorates due to distributed capacitance interference and DC system interference
Solution Approach 1:
The patent changes the signal frequency parameter from high-frequency to low-frequency (specifically using a frequency of 1Hz or lower) to eliminate the negative effects of distributed capacitance and DC system interference, thereby improving measurement precision while maintaining acceptable detection speed
Solution Approach 2:
The patent employs periodic square wave signal injection at low frequency to periodically excite the insulation resistance being measured, allowing for accurate measurement through periodic sampling and calculation without the continuous interference problems of high-frequency methods
2Device complexity
If resistance voltage division method is used for insulation resistance detection, then device complexity is reduced, but detection precision deteriorates due to resistor interference and high-voltage circuit interference with low-voltage circuit
Solution Approach 1:
The patent introduces an isolation module as an intermediary between the high-voltage detection circuit and low-voltage control circuit, effectively blocking high-voltage interference while allowing signal transmission, thus improving measurement precision without significantly increasing device complexity
Solution Approach 2:
The patent divides the detection system into separate high-voltage and low-voltage sections with clear isolation, preventing interference between circuits while maintaining functional integrity, achieving a balance between device complexity and measurement precision
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution improves the accuracy and precision of insulation resistance detection by minimizing voltage fluctuations and interference, effectively addressing the limitations of existing methods.
Implementation Method 1
a signal generating 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
Implementation Method 2
the other end of the first voltage dividing module is connected to a first isolation module and a second voltage dividing module respectively; the first isolation module, connected to one end of a sampling module
Implementation Method 3
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
Implementation Method 4
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
Implementation Method 5
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
Data Source
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Figure 5
AI summary
The present application discloses an insulation detection circuit, a method and a battery management system. 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 the 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. The insulation detection circuit according to the embodiments of the present application improves the detection precision of the insulation resistance value.