Load Switch Overcurrent Protection Using Temperature Feedback
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Solution Overview
Problem
Existing switch devices fail to ensure safe and efficient operation of electrical continuity or shutdown between terminals, particularly in high-current applications, leading to potential overheating and safety risks due to excessive current flow.
Innovation Solution
A load driving system incorporating a switch device with a controller, current detection circuit, and temperature detection circuit that monitors and controls the output transistor to prevent excessive current and temperature, using overcurrent protection characteristics adjusted based on external temperature to ensure safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output transistor is used to ensure electrical continuity between terminals, then the electrical connection reliability is improved, but excessive current flow causes overheating and safety risks
Solution Approach 1:
The control circuit performs preliminary detection of output current and external temperature before the excessive current condition becomes critical. Based on the detected temperature, the control circuit pre-adjusts the overcurrent protection threshold to appropriate levels, preventing overheating before it occurs
Solution Approach 2:
The control circuit continuously monitors the output current and external temperature through detection circuits, and dynamically adjusts the overcurrent protection characteristics based on this feedback. This closed-loop control ensures the output transistor operates safely while maintaining electrical continuity
2Reliability
If the overcurrent protection value is set to a low level to prevent overheating, then safety is improved, but the current carrying capacity and power transmission efficiency deteriorate
Solution Approach 1:
The overcurrent protection value is made dynamic rather than fixed. The control circuit adjusts the protection threshold in real-time based on the detected external temperature, allowing higher current capacity when cool and lower current capacity when hot, thus optimizing both safety and power transmission
Solution Approach 2:
The control circuit changes the protection parameter (overcurrent threshold) based on temperature conditions. When external temperature is low, a higher protection value is applied to maximize power transmission; when temperature rises, the protection value is reduced to ensure safety
3Power
If large wiring diameters are used to handle high current, then the current carrying capacity is improved, but the device size and cost increase
Solution Approach 1:
The switch device performs self-protection by monitoring its own operating conditions (current and temperature) and automatically adjusting protection characteristics. This eliminates the need for oversized wiring as a passive safety measure, allowing compact wiring design while maintaining safety through active control
Data Source
AI summary
The switch device includes an input terminal, an output terminal, an output transistor provided between the input terminal and the output terminal, and a control circuit configured to, under its control, turn on or off the output transistor in response to a control signal. The control circuit is enabled to execute a protective operation by which the output transistor is switched over from on to off independent of the control signal on a basis of an outside temperature of the switch device and an output current flowing through the output transistor.