Sensor Output Circuit for Power Line Disconnection Detection
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Solution Overview
Problem
Conventional semiconductor electronic circuits fail to accurately detect disconnection of the power supply line due to intermediate potential and current inflow issues, making it difficult for the ECU to recognize disconnection and utilize the power supply voltage effectively.
Innovation Solution
An electronic circuit with a load, transistor, current generation circuit, and control circuit is designed to suppress current inflow and set output impedance to high impedance, ensuring the output terminal voltage equals the external circuit voltage during power supply disconnection, using a current generation circuit to control the transistor with a changing control voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output terminal has a current flow path to the power supply line during disconnection, then current flows from the output terminal into the power supply line, but the output terminal voltage becomes intermediate potential making disconnection detection difficult
Solution Approach 1:
The patent applies preliminary anti-action by introducing a diode connected between the power supply line and ground that becomes conductive when the power supply voltage drops below a threshold level. This diode preemptively counteracts the intermediate potential problem by providing an alternative current path to ground, ensuring the output terminal voltage drops to a detectable low level even when current flows from the output terminal into the power supply line during disconnection.
2Reliability
If the power supply line is disconnected, then the ECU side needs to recognize disconnection through high output impedance and high output terminal voltage, but electric charge remains in the power supply line causing intermediate potential
Solution Approach 1:
The patent extracts the problematic stored charge from the power supply line by providing a dedicated discharge path through the diode to ground. When disconnection occurs, the diode becomes conductive and rapidly drains the stored charge from the power supply line and associated capacitors, separating the discharge function from the normal power distribution path. This enables quick voltage collapse to ground level for reliable disconnection detection without waiting for natural discharge.
Solution Approach 2:
The diode serves as an intermediary element that activates specifically during disconnection conditions. It mediates between the stored charge in the power supply line and the ground, providing a controlled discharge path only when needed. This intermediary component enables the system to maintain normal operation during connected states while facilitating rapid voltage collapse during disconnection for accurate detection.
3Measurement precision
If the output terminal voltage is to be set to high level during disconnection, then current inflow to the output terminal must be suppressed, but intermediate potential persists due to remaining charge
Solution Approach 1:
The diode provides preliminary anti-action by preemptively creating a low-impedance path to ground when the power supply voltage drops below the diode's forward voltage threshold. This counteracts the intermediate potential effect before it can prevent accurate detection, ensuring that any current flowing from the output terminal into the power supply line is shunted to ground, maintaining the output terminal at a clearly detectable low voltage level.
Data Source
AI summary
An electronic circuit that recognizes a disconnected state from an outside during disconnection of a power supply line is provided. For this purpose, an electronic circuit includes: a load provided between a power supply line and an output terminal in the electronic circuit; a transistor provided between the load and the output terminal; a current generation circuit that generates current using a power supply voltage at a power supply line in the electronic circuit; and a control circuit that controls the transistor using a control voltage that changes according to the current generated by the current generation circuit.