Digital Filter Insulation Resistance Detection for High-Voltage Noise
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Solution Overview
Problem
Existing apparatuses for detecting insulation resistance reduction between a vehicle body and a high-voltage circuit suffer from low accuracy due to temperature variations and aging degradation of analog filters, and require costly high-voltage resistance elements for protection.
Innovation Solution
A digital filter and aliasing suppression circuit are used in conjunction with a protection circuit to accurately detect insulation resistance changes, utilizing a digital filter with a higher signal-to-noise ratio and a protection circuit with low voltage-resistance elements to suppress high-voltage noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an analog filter is used to remove high-voltage noise, then noise removal is achieved, but detection accuracy deteriorates due to temperature variation and aging degradation
Solution Approach 1:
The patent replaces the analog filter (mechanical/electrical system subject to physical degradation) with a digital filter implemented in software. The analog filter's properties change due to temperature and aging, but the digital filter's filtering characteristics remain stable as they are defined by software algorithms rather than physical components subject to environmental degradation.
Solution Approach 2:
The patent changes the filtering approach from analog domain to digital domain, transforming the filter's operational parameters from physical component values (resistance, capacitance, inductance) to digital signal processing parameters (sampling frequency, filter coefficients). This parameter transformation eliminates the degradation issues associated with physical components.
2Measurement precision
If temperature-compensated elements are added to the analog filter to improve accuracy, then detection accuracy improves, but device complexity increases
Solution Approach 1:
The patent eliminates the need for complex temperature-compensated analog circuits by replacing the entire analog filter with a digital filter. This substitution removes the requirement for multiple temperature-compensated elements and their associated complex circuitry, achieving accuracy improvement without increasing device complexity.
3Reliability
If high-voltage resistance elements are used to protect the determiner, then high voltage resistance is ensured, but cost increases
Solution Approach 1:
The patent replaces high-voltage resistance physical elements with a digital protection mechanism. The coupling capacitor blocks DC high-voltage components, and the digital filter processes only the AC signal components, eliminating the need for expensive high-voltage resistance elements in the signal path while maintaining protection of the determiner.
4Reliability
If a protection circuit with high voltage-resistance elements is provided, then the determiner is protected from high-voltage noise, but device complexity increases
Solution Approach 1:
The patent replaces complex high-voltage resistance protection circuits with a simpler combination of a coupling capacitor and digital signal processing. The coupling capacitor provides high-voltage blocking, and the digital filter provides noise rejection, achieving protection with fewer and simpler 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
This configuration enhances the accuracy of insulation resistance detection while ensuring high voltage resistance with a simpler and cost-effective setup, reducing the impact of temperature and aging on detection accuracy.
Implementation Method 1
An oscillation circuit 22 is configured to apply an AC voltage of a predetermined frequency to a second terminal 21b of the coupling capacitor 21 through a predetermined output impedance 221
Implementation Method 2
A digital filter 232 is configured to remove noise included in the potential to ground to be forwarded to the determiner 231
Implementation Method 3
An aliasing suppression circuit 24 is configured to suppress aliasing in the digital filter 232, where the aliasing suppression circuit 24 is electrically connected between the second terminal 21b of the coupling capacitor 21 and a signal input of the digital filter 232
Implementation Method 4
A protection circuit 25 is configured to protect the determiner 231 and the digital filter 232 from high-voltage noise generated in the high-voltage circuit 1
Data Source
AI summary
An apparatus capable of detecting reduction in insulation resistance between a vehicle body and a high-voltage circuit. In the apparatus, a filter for removing noise included in a potential to ground at a terminal of a coupling capacitor includes a digital filter and an aliasing suppression circuit for suppressing aliasing in the digital filter. In addition, a protection circuit, which protects the digital filter and a determiner operable to detect the reduction in insulation resistance from high-voltage noise generated in the high-voltage circuit, is electrically disposed between a resistor of the aliasing suppression circuit and a signal input of the digital filter, where a potential at a junction between the resistor of the aliasing suppression circuit and the signal input of the digital filter is lower than a potential at the terminal of the coupling capacitor upon application of the high-voltage noise to the apparatus.