Semiconductor Circuit Rapid Overcurrent Detection
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Solution Overview
Problem
Current detection circuits, utilizing isolation amplifiers, face a significant delay in responding to overcurrents due to the time required for signal processing, making it impossible to rapidly detect overcurrents in control targets like motors.
Innovation Solution
Incorporating a primary circuit with a light emitting element that emits brighter light during overcurrents and a secondary circuit that outputs a voltage corresponding to the light emission, allowing for rapid overcurrent detection through a comparator and buffer configuration, enabling prompt transition of the FAULTN terminal voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolation amplifier with a signal processing circuit such as a ΔΣ ADC and decoder is used to detect current, then electrical insulation is maintained, but the response time becomes slow (several tens of μs) making it impossible to rapidly detect overcurrent
Solution Approach 1:
The isolation amplifier is divided into two separate circuits: a primary circuit that generates light based on current magnitude, and a secondary circuit that detects the light. This segmentation allows the primary circuit to respond immediately to overcurrent by changing light emission, while the secondary circuit processes the optical signal, thereby achieving both electrical insulation and fast response time.
Solution Approach 2:
The electrical signal transmission across the isolation barrier is replaced with optical signal transmission. The primary circuit converts current information into light emission, and the secondary circuit converts the optical signal back to electrical form. This substitution eliminates the need for complex signal processing circuits on the isolated side, enabling rapid overcurrent detection while maintaining electrical insulation.
2Speed
If a light emitting element is used to indicate overcurrent through brighter light emission, then rapid detection is enabled, but the device complexity increases due to additional circuits
Solution Approach 1:
The light emitting element serves dual functions: it acts as an indicator of current magnitude (brighter light for higher current) and as a transmission medium for transferring signal information across the isolation barrier. This multi-functionality enables rapid overcurrent detection without requiring separate indicator circuits, thereby limiting the increase in device complexity.
Solution Approach 2:
The light emitting element and photodetector act as intermediaries for signal transmission across the isolation barrier. Instead of directly transmitting electrical signals or adding complex communication interfaces, the patent uses optical conversion as an intermediary mechanism. This approach simplifies the overall system architecture while achieving fast response times for overcurrent detection.
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
This configuration enables rapid detection of overcurrents by utilizing brighter light emission from the light emitting element, facilitating immediate notification of overcurrents without the need for extensive decoding or D/A conversion processes, thus improving response time.
Implementation Method 1
a primary circuit that causes the light emitting element to emit light in accordance with a current flowing through a control target
Implementation Method 2
a secondary circuit that is electrically insulated from the primary circuit, outputs a voltage according to a light emission amount of the light emitting element
Data Source
AI summary
A semiconductor circuit has a primary circuit that causes the light emitting element to emit light in accordance with a current flowing through a control target, and that causes the light emitting element to emit light brighter when an overcurrent flows through the control target; and a secondary circuit that is electrically insulated from the primary circuit, outputs a voltage according to a light emission amount of the light emitting element, and outputs an overcurrent detection signal indicating the brighter light emission in the light emitting element.