Adjustable Sensor Interface Circuitry for Engine Knock Detection
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Solution Overview
Problem
Existing engine knock sensor interface circuitry requires additional die area and cost for higher order filters with higher Q factors, which is not optimal for systems with fast analog-to-digital converters, and results in signal dynamic range loss due to increased gain.
Innovation Solution
An adjustable sensor interface circuitry that includes operational amplifiers, gain circuitry, and switches, allowing for electronic adjustment of gain and Q characteristics through external components and control signals, enabling a single integrated circuit to support multiple platforms with varying analog-to-digital converter speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a second order filter structure with higher Q factor is integrated on the interface integrated circuit, then the interface circuitry can be used with slower analog-to-digital converters, but additional die area is required and additional cost is incurred
Solution Approach 1:
The patent implements a universal interface circuitry design that can operate with both fast and slow ADCs by providing electronically adjustable filter order and Q factor. The circuit includes switchable feedback paths that allow dynamic reconfiguration between first-order and second-order filter modes, eliminating the need for separate dedicated circuits for different ADC speeds.
Solution Approach 2:
The patent employs dynamic reconfiguration of the filter structure through electronically controlled switches that can change the feedback path connections. This allows the filter order and Q factor to be adjusted in real-time based on the ADC speed, transitioning between first-order and second-order configurations without requiring additional physical components.
2Measurement precision
If a second order filter with higher Q is used, then knock signal detection capability is improved for slower ADCs, but gain of the output signal is increased leading to loss of signal dynamic range
Solution Approach 1:
The patent implements independent control of filter Q factor and output gain through separate electronic adjustment mechanisms. The Q factor can be increased to improve knock detection precision, while the gain can be independently reduced to maintain signal dynamic range, allowing optimization of both parameters without the coupled trade-off present in fixed-architecture filters.
Solution Approach 2:
The patent separates the filter function into distinct adjustable parameters (Q factor and gain) that can be controlled independently. This segmentation allows the Q factor to be optimized for detection precision while the gain is separately optimized to preserve dynamic range, rather than having both parameters fixed together as in traditional filter designs.
3Area of stationary object
If interface circuitry is designed for fast ADCs without integrated second order filter, then die area is reduced, but the circuitry cannot be used with slower ADCs
Solution Approach 1:
The patent creates a universal interface circuitry that adapts to different ADC speeds through electronic reconfiguration. The circuit includes switchable elements that enable it to function as a first-order filter for fast ADCs or reconfigure as a second-order filter for slower ADCs, providing platform independence without requiring additional die area for multiple dedicated circuits.
Data Source
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Figure 2
Figure 3
AI summary
A sensor interface filter (50) having adjustable gain and Q is provided. The sensor interface (50) includes a first operational amplifier (12) coupled to gain circuitry (26), a gain stage (27), and a resistor (18). The gain circuitry (26) and gain stage (27) are electrically coupled to each other. The gain stage (26) includes a gain stage switch (30), and is coupled to control circuitry (51). The control circuitry (51) controls the state of the gain stage switch (30) to vary the number of feedback current paths providing feedback to the inverting input (11) of the first operational amplifier (12), altering the gain provided by the first operational amplifier (12). The sensor interface (50) further includes a second operational amplifier (52) coupled to filter circuitry (41) and feedback switches (54,56). The feedback switches (54,56) are coupled to the control circuitry (51), which controls the state of the feedback switches (54,56) to vary the gain provided by the second operational amplifier (52) and the filter Q of the sensor interface (50). A method is also provided.