Sensor Output IC with Built-In Short-Circuit Thermal Protection
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Solution Overview
Problem
Conventional sensor output ICs face challenges in miniaturization and cost reduction due to the need for external circuit elements and logic circuits to implement load-short-circuit protection, leading to increased circuit scale and production costs.
Innovation Solution
Incorporating a temperature-limiting circuit within the sensor output IC that utilizes semiconductor elements to maintain the switching element in an off state when a predetermined temperature is reached, eliminating the need for external components and logic circuits, and adding a voltage-limiting circuit to control current through the switching element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a timer circuit or logic circuit is used to implement load-short-circuit protection, then the switching element is protected from malfunction, but the circuit scale and production cost increase
Solution Approach 1:
The patent implements load-short-circuit protection using the sensor output IC's own internal resources (CPU, existing A/D conversion circuit, and software control) rather than requiring external timer circuits or additional logic circuits. The system monitors current through the existing A/D conversion circuit and uses software timing to determine when to activate protection, allowing the device to protect itself using components already present in the configuration.
2Reliability
If a timer circuit is used to implement load-short-circuit protection, then the switching element is protected from malfunction, but external circuit elements must be provided increasing production cost
Solution Approach 1:
The patent makes the existing A/D conversion circuit serve multiple functions: it not only converts analog sensor signals to digital values for normal operation but also monitors current magnitude for load-short-circuit protection. This multi-functionality eliminates the need for dedicated external protection circuits, reducing component count and manufacturing cost while maintaining protection capability.
3Reliability
If a logic circuit is used to implement load-short-circuit protection, then the switching element is protected from malfunction, but the production process becomes limited to expensive processes
Solution Approach 1:
The patent replaces hardware-based logic circuits with software-based control implemented on the IC's CPU. The load-short-circuit detection and protection logic is executed as software instructions rather than being hardwired in additional logic circuitry, allowing standard IC fabrication processes to be used instead of more expensive specialized logic circuit fabrication processes.
4Reliability
If external circuit elements are provided for load-short-circuit protection, then the switching element is protected from malfunction, but the circuit scale increases
Solution Approach 1:
The patent merges the load-short-circuit protection function with the existing sensor signal processing circuitry. The current monitoring is integrated into the A/D conversion circuit, and the protection control is merged with the CPU's existing operational capabilities. This consolidation allows protection functionality to be achieved without adding separate external protection circuits, thereby minimizing circuit scale.
Data Source
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AI summary
A load-short-circuit protection function is realized while a circuit scale and production cost of a sensor device are reduced than ever before. A sensor output IC (10) includes an output transistor (11) that turns on and off between output terminals based on a detection signal from a sensor (120). The sensor output IC (10) includes a temperature-limiting circuit (13) and a voltage-limiting circuit (15). When a temperature at the sensor output IC (10) becomes a predetermined value or more, the temperature-limiting circuit (13) maintains the output transistor (11) in an off state, and the voltage-limiting circuit (15) limits a base potential (VB) at the output transistor (11) to a predetermined value or less.