Insulation Detection Circuit Parasitic Capacitance Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional insulation detection circuits for power batteries in electric vehicles face significant errors due to the impact of parasitic capacitance, leading to inaccurate insulation resistance measurements.
Innovation Solution
An insulation detection circuit with a first isolation module, voltage division module, signal generation module, and processor that injects a sine wave AC signal and calculates insulation resistance by determining phase shift and voltage amplitudes, isolating the high-voltage signal from interfering with low-voltage sampled signals, thereby improving detection accuracy and reducing detection time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-frequency AC signal is directly injected into the power battery for insulation detection, then the detection process can be implemented, but the parasitic capacitance of the power battery causes large detection errors
Solution Approach 1:
The patent introduces an isolation module as an intermediary component between the signal injection circuit and the power battery. This isolation module (comprising isolation capacitor C1 and isolation resistor R1) mediates the interaction between the detection circuit and the power battery, blocking the harmful high-frequency signal from directly coupling with the parasitic capacitance while still enabling insulation resistance measurement through the isolated signal path.
Solution Approach 2:
The patent extracts and separates the isolation function into a dedicated isolation module that is physically and electrically separated from the main detection circuit. By taking out the isolation functionality as an independent module with specific components (C1, R1), the harmful parasitic capacitance effects are isolated from the measurement path, allowing accurate detection without direct coupling of the high-frequency signal to the power battery terminals.
2Productivity
If conventional insulation detection methods are used, then the detection can be performed, but the detection time is extended and system stability is compromised
Solution Approach 1:
The patent employs periodic action by using AC signals of specific frequencies (50Hz or 400Hz) for insulation detection instead of continuous DC measurement. The isolation module is designed to work with these periodic signals, allowing the system to perform rapid periodic measurements without causing stability issues, thereby improving detection speed while maintaining system reliability through the stabilizing effect of the isolation circuitry.
3Measurement precision
If high-frequency AC signal injection is used for insulation detection, then the detection function is achieved, but the cost and complexity of the circuit increase
Solution Approach 1:
The patent applies parameter changes by selecting specific standard frequency values (50Hz or 400Hz) for the AC signal injection and choosing appropriate parameter ranges for the isolation components (capacitor C1 with 1nF-100nF, resistor R1 with 1kΩ-100kΩ). These parameter specifications simplify the circuit design and component selection while maintaining measurement precision, avoiding the need for complex adjustable circuits or specialized high-frequency components.
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 solution enhances the accuracy and speed of insulation resistance detection, reducing errors caused by parasitic capacitance and maintaining system stability at a lower cost.
Implementation Method 1
the signal generation module is connected to the first sampling point and configured to inject a sine wave AC signal of a predetermined frequency into the power battery under detection
Implementation Method 2
the first isolation module includes an isolation capacitor, a first end of the isolation capacitor is connected to the positive electrode of the power battery under detection, and a second end of the isolation capacitor is connected to the second sampling point
Implementation Method 3
the voltage division module includes a voltage division resistor, a first end of the voltage division resistor is connected to the first sampling point, and a second end of the voltage division resistor is connected to the second sampling point
Implementation Method 4
calculate a phase shift θ of the second sampled signal relative to the first sampled signal according to the first voltage amplitude u, the bias voltage M, the first instantaneous voltage UA, the second voltage amplitude U, and the second instantaneous voltage UB
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The embodiments of the present disclosure provide an insulation detection circuit, an insulation detection method and a battery management system. The circuit includes a first isolation module (G1), a voltage division module (F1), a signal generation module (Y1), a first sampling point (S1), a second sampling point (S2) and a processor (P1). A first end of the first isolation module (G1) is connected to a positive electrode of a power battery under detection, and a second end of the first isolation module (G1) is connected to the second sampling point (S2). The signal generation module (Y1) is connected to the first sampling point (S1) and configured to inject an AC signal of a predetermined frequency into the power battery under detection and provide the first sampling point (S1) with a first sampled signal of the predetermined frequency. A first end of the voltage division module (F1) is connected to the first sampling point (SI), and a second end of the voltage division module (F1) is connected to the second sampling point (S2). The processor (P1) is configured to calculate an insulation resistance (Rnp) of the power battery under detection according to the first sampled signal and the second sampled signal.