Smart Electronic Switch Current Sensing Circuit
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Solution Overview
Problem
Existing electronic circuit breakers, or e-fuses, in automotive applications lack adequate fault tolerance and functional safety, particularly in environments where stringent safety standards like ISO 26262 must be met, and they require efficient configuration to manage overcurrent scenarios effectively.
Innovation Solution
An integrated circuit with a power transistor, current sensing circuit, and control circuit that generates a drive signal based on a selected current versus time characteristic, allowing for diagnosis currents to represent load currents or specific characteristic curves, enhancing fault detection and protection mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If common driver circuits are used in electronic circuit breakers, then the device complexity is reduced, but the fault tolerance and functional safety deteriorate
Solution Approach 1:
The driver circuit is segmented into multiple independent functional blocks: a control circuit for generating drive signals, a current sensing circuit for monitoring load current, and a diagnosis circuit for fault detection. Each segment operates independently with dedicated functions, improving reliability without significantly increasing overall complexity.
Solution Approach 2:
A diagnosis current output circuit serves as an intermediary between the power transistor and external diagnosis equipment. This intermediary circuit provides fault information without requiring complex internal modifications, enabling enhanced fault tolerance while maintaining simple circuit architecture.
2Ease of operation
If electronic switches are used to replace fuses, then the ease of operation is improved, but the reliability deteriorates due to inadequate fault tolerance
Solution Approach 1:
The current sensing circuit continuously monitors the load current and feeds back this information to the control circuit. This feedback mechanism enables the electronic switch to automatically adjust its operation based on actual current conditions, maintaining ease of operation while significantly improving fault tolerance through real-time monitoring and protection.
3Measurement precision
If diagnosis current is provided to represent load current, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The diagnosis current output circuit creates an accurate copy of the load current signal without requiring complex measurement and reconstruction circuits. By directly providing a proportional current copy to external diagnosis equipment, the system achieves high measurement precision while keeping the internal circuit complexity minimal.
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
The solution provides improved fault tolerance and functional safety by accurately monitoring and managing overcurrent conditions, enabling robust protection of wires and loads in automotive systems while allowing for configurable settings based on wire parameters.
Implementation Method 1
a current sensing circuit configured to sense a load current passing through the power transistor
Data Source
AI summary
An integrated circuit may include a power transistor coupled between a supply pin and an output pin; a current sensing circuit configured to sense a load current passing through the power transistor and to provide a respective current sense signal; a first configuration pin; a current output circuit configured to provide a diagnosis current at a current output pin; a diagnosis pin for receiving a diagnosis request signal; and a control circuit configured to: select a characteristic curve representing a current versus time characteristic dependent on a external circuit connected to the first configuration pin; generate a drive signal for the power transistor dependent on the selected characteristic curve and the current sense signal; and control—dependent on a pulse pattern of the diagnosis request signal—the current output circuit to set the value of the diagnosis current such that it represents the load current or the selected characteristic curve.