Output Transistor Current Limiting for Overcurrent Durability
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Solution Overview
Problem
Existing switch devices face durability issues due to repeated overcurrent protection operations, which cause temperature fluctuations in output transistors, affecting the device's structure and reliability.
Innovation Solution
A switch device with an overcurrent protection circuit that can adjust the upper limit current value, allowing it to change from a first current value to a second current value less than the first after performing the overcurrent protection operation, thereby reducing the target current to the first current value or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overcurrent protection operation is performed repeatedly to protect the output transistor, then the current magnitude is limited to a predetermined value, but temperature fluctuation occurs in the output transistor which badly affects the structure of the switch device
Solution Approach 1:
The patent applies dynamics by making the upper limit current value adjustable rather than fixed. The control circuit dynamically changes the upper limit current value between a first current value and a second current value based on the operating state, allowing the system to adapt to different conditions and reduce temperature fluctuations while maintaining protection functionality.
Solution Approach 2:
The patent changes the parameter of upper limit current value from a fixed predetermined value to a variable parameter that can switch between multiple current values. This parameter change allows the overcurrent protection circuit to operate at different current levels, reducing repeated stress on the output transistor and minimizing temperature fluctuations.
2Productivity
If the upper limit current value is kept at a high level to ensure adequate current supply, then productivity is maintained, but durability against overcurrent deteriorates when faults occur
Solution Approach 1:
The system dynamically adjusts the upper limit current value based on the detected state. When the output transistor is normally on, the first (higher) current value maintains productivity. When overcurrent protection is triggered, the second (lower) current value protects durability. This dynamic adjustment resolves the contradiction between productivity and durability.
Solution Approach 2:
The control circuit periodically or repeatedly changes the upper limit current value between the first and second current values based on the operating state. This periodic action allows the system to alternate between high current supply mode and protected low current mode, ensuring both productivity during normal operation and durability during fault conditions.
Data Source
AI summary
A switch device includes an output transistor, an overcurrent protection circuit configured to be capable of performing an overcurrent protection operation in which magnitude of target current flowing in the output transistor is limited to a predetermined upper limit current value or less, and a control circuit configured to be capable of controlling a state of the output transistor and capable of changing the upper limit current value among a plurality of current values including a predetermined first current value and a predetermined second current value less than the first current value. The control circuit can limit the magnitude of the target current to the first current value or less in response to the magnitude of the target current reaching the first current value, and then change the upper limit current value to the second current value.