Disconnection Detecting Circuit High-Impedance Initialization
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Solution Overview
Problem
Existing disconnection detection circuits for AC-driven loads, such as antennas and sensors, face issues with erroneous detection due to variations in load characteristics and noise, leading to increased chip area and cost in conventional designs.
Innovation Solution
A disconnection detecting circuit comprising a capacitor, diode, initialization circuit, and control circuit that sets an output terminal to a high-impedance state during disconnection detection, initializes charges in the capacitor, and drives the load with an AC signal, allowing reliable detection by comparing the capacitor voltage with a determination reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reference voltage Vref is decreased to prevent erroneous detection, then disconnection detection accuracy is improved, but erroneous detection due to noise increases
Solution Approach 1:
The initialization circuit performs preliminary action by initializing the capacitor to a known state before disconnection detection begins. This ensures that the detection process starts from a consistent baseline, allowing the use of a high reference voltage without risking erroneous detection from residual charges or uncertain initial conditions.
Solution Approach 2:
The invention changes the parameter of reference voltage from low to high. By using a high reference voltage in combination with the initialization circuit, the system achieves both accurate disconnection detection and noise immunity, as the high voltage provides a clear distinction between connected and disconnected states while the initialization ensures reliable starting conditions.
2Measurement precision
If the size of MOSFET 11 is increased to increase current flowing in the shunt resistor, then disconnection detection accuracy is improved, but chip area and manufacturing cost increase
Solution Approach 1:
The invention extracts the charge initialization function from the main detection circuit by introducing a separate initialization circuit. This allows the use of a high reference voltage for accurate detection without requiring increased current through the shunt resistor, thereby avoiding the need for larger MOSFETs and reducing chip area.
Solution Approach 2:
The capacitor serves as an intermediary element that stores charge information. The initialization circuit manages this intermediary by periodically resetting the capacitor's charge state, enabling accurate detection using a high reference voltage without requiring high current flow through the shunt resistor.
3Productivity
If a conventional disconnection detection circuit is used for AC-driven loads, then the circuit can operate, but erroneous detection occurs due to variations in load characteristics and noise
Solution Approach 1:
The initialization circuit performs preliminary action by resetting the capacitor's charge state before each detection cycle. This preliminary initialization eliminates the influence of residual charges and ensures that subsequent detection is based solely on the current AC-driven load state, preventing erroneous detection due to load variations or noise.
Solution Approach 2:
The system implements periodic action by repeatedly initializing the capacitor and performing disconnection detection in cycles. This periodic initialization and detection process ensures that each measurement starts from a known state, improving accuracy for AC-driven loads whose characteristics may vary over time.
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 prevents erroneous detection by setting a high determination reference voltage and reduces chip area and manufacturing costs by eliminating the need for additional semiconductor elements, ensuring reliable disconnection detection despite load variations and noise.
Implementation Method 1
a capacitor (26) connected between the second output terminal (6) and a reference potential
Implementation Method 2
a diode (28) connected in a chargeable direction between the second output terminal (6) and the capacitor (26)
Data Source
AI summary
In a disconnection detecting mode, first and second MOSFETs are turned off, a transistor is turned on, and charges of a capacitor are initialized. After that, third and fourth MOSFETs are alternately turned on/off by drive signals and having a complementary relation. When an antenna is connected normally, a pulse AC signal is transmitted to an output terminal via the antenna, and current flows from the output terminal into the capacitor via a resistor, a diode, and a resistor. When a voltage across terminals becomes equal to or higher than a determination reference voltage, a disconnection detection signal is changed to the H level (a connection state).