ADC and Current-Sink Circuit for Reserve Capacitor Voltage Drop Measurement
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Solution Overview
Problem
Existing systems for measuring voltage drops in reserve capacitors of supplemental restraint systems in vehicles have limited dynamic range and low-resolution accuracy, making it difficult to reliably monitor the health and functionality of these capacitors, especially during critical events like crashes.
Innovation Solution
A method and circuit using an analog-to-digital converter, a current sink, and a controller to measure voltage drops by determining a set point for the current sink, sampling outputs during steady-state and voltage drop conditions, and computing relative voltage drop values, which allows for high-resolution accuracy while maintaining a wide operating range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing measurement systems are used for reserve capacitors, then the system structure is simple, but the measurement precision and dynamic range are limited
Solution Approach 1:
The measurement process is divided into distinct phases: steady-state sampling phase and voltage-drop sampling phase. The controller separates the measurement into discrete time intervals, sampling at specific moments rather than continuously, which improves precision without requiring complex continuous measurement circuitry
Solution Approach 2:
The system performs preliminary sampling during steady-state conditions before the voltage drop occurs. This preliminary measurement establishes a baseline that is then compared with post-drop measurements, enabling accurate determination of voltage change without needing complex real-time differential measurement circuits
2Adaptability or versatility
If the analog-to-digital converter operates over a wide voltage range, then the adaptability is improved, but the converter may saturate during voltage drops
Solution Approach 1:
The system dynamically adjusts the measurement strategy based on operating conditions. During steady-state, the ADC operates at its full range for maximum resolution. During voltage drops, the system switches to differential measurement mode, effectively adapting the measurement range to match the instantaneous voltage conditions and preventing saturation
Solution Approach 2:
The controller implements periodic sampling at strategically chosen moments: once during steady-state and again during voltage-drop conditions. This periodic measurement approach allows the system to capture voltage information across a wide range while avoiding continuous exposure that could cause saturation
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 provides improved dynamic range and high-resolution accuracy for measuring voltage drops, enabling effective monitoring of reserve capacitors and preventing analog-to-digital converter saturation, thus ensuring reliable operation of supplemental restraint systems.
Implementation Method 1
analog-to-digital converter, a current sink, and a controller, an input of the analog-to-digital converter and an input of the current sink coupled to the node
Implementation Method 2
determining a set point for the current sink; sampling an output of the analog-to-digital converter during the voltage drop
Data Source
Figure 1a~1b
Figure 2~4
Figure 5
AI summary
A system and method is provided for measuring a voltage drop at a node (VIN). In embodiments, a circuit includes an analog-to-digital converter (402), a current sink (406), and a controller. The input of the analog-to-digital converter (402) and the input of the current sink (406) is coupled to the node (VIN) to be measured. A set point for the current sink (406) is determined. The output of the analog-to-digital converter (402) during the voltage drop is sampled. And a relative voltage drop value is computed by subtracting the sampled output of the analog-to-digital converter (402) during the voltage drop from a sampled output of the analog-to-digital converter (402) during a steady-state condition. The current sink (406) operating at the set point during the steady-state condition and during the voltage drop.