ADC Input Switching for Signal Line Disconnection Detection
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Solution Overview
Problem
Conventional analog-to-digital (AD) conversion devices require pull-down resistors on each signal line to detect disconnection, leading to increased circuit scale, especially when a large number of input units are connected, which complicates the circuit design.
Innovation Solution
An AD conversion device that uses a switching unit connected to multiple input units through signal lines, a sample and hold circuit, and a controller to determine disconnection by selecting a reference voltage different from the external voltage before selecting the external voltage, eliminating the need for pull-down resistors by assessing voltage changes between the reference and external voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pull-down resistors are provided on each signal line to detect disconnection, then disconnection detection capability is improved, but circuit scale increases
Solution Approach 1:
The patent merges the disconnection detection function with the existing AD conversion circuitry by using the switch and voltage detection mechanisms already present in the system. Instead of adding separate pull-down resistors on each signal line, the invention combines detection functionality into the shared control circuit, thereby maintaining detection capability while reducing overall circuit complexity
Solution Approach 2:
The switch and controller are designed to serve multiple functions: they control signal selection for AD conversion and simultaneously perform disconnection detection by monitoring voltage levels. This multi-functionality eliminates the need for dedicated pull-down resistors on each line, reducing circuit scale while preserving reliability
2Measurement precision
If pull-down resistors are provided on each signal line to detect disconnection, then disconnection detection accuracy is improved, but number of components increases
Solution Approach 1:
The invention extracts the essential detection function from the physical pull-down resistor implementation and realizes it through voltage level monitoring controlled by the switch. By taking out the detection capability from hardware-dependent pull-down resistors and implementing it through control logic and voltage sensing, the system maintains detection accuracy while dramatically reducing the number of required components
Solution Approach 2:
Instead of physically replicating pull-down resistors on each signal line, the system uses a single switch and controller that can sequentially monitor multiple lines by switching between them. This virtual copying approach through time-division multiplexing maintains detection accuracy across all lines without requiring proportional increases in physical components
Data Source
AI summary
An analog-to-digital conversion device includes: a switch connected to input units through signal lines to receive external voltages selecting and outputting one external voltage; an S/H circuit holding a voltage corresponding to an output of the switch; a converter performing AD conversion based on the voltage; and a controller determining the external voltage selected by the switch and performing a disconnection determination whether a disconnection occurs in the signal line. In the disconnection determination, the controller controls the switch to select a reference voltage different from the external voltage before controlling the switch to select the external voltage to be determined, and performs the disconnection determination based on a voltage difference between the reference voltage and the external voltage after controlling the switch to select the external voltage.