Output Circuit Current Limiting for Short-Circuit Protection
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Solution Overview
Problem
Existing semiconductor output circuits face challenges in managing short circuits to ground, leading to increased current flow before interruption, which enlarges circuit scale and increases costs due to the need for wider interconnects and more output transistors in parallel, compromising safety and efficiency.
Innovation Solution
An output circuit design that initiates operation in a constant-current drive state, limiting output current to a predetermined value, and shifts to a normal drive state only when necessary, preventing high-current output during short circuits and reducing the need for oversized interconnects and transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output circuit uses conventional overcurrent protection design, then the circuit can protect against short circuits, but the circuit scale increases and manufacturing costs increase due to wider interconnects and more output transistors in parallel
Solution Approach 1:
The patent applies preliminary action by initiating operation in a constant-current drive state before normal drive state. The constant-current limiting circuit pre-limits the output current to a predetermined value during startup and short-circuit conditions, preventing excessive current flow before it can cause damage. This proactive current limitation eliminates the need for oversized protective components.
Solution Approach 2:
The patent changes the operating parameter from fixed normal drive mode to variable mode with two states: constant-current drive state (during startup/short circuit) and normal drive state. The control circuit dynamically switches between these states based on circuit conditions, allowing the output current to be predetermined during critical phases and full power during normal operation, thereby reducing the need for oversized components designed for worst-case scenarios.
2Power
If the output circuit allows high current flow during short circuits, then normal operation performance is maintained, but power supply breakage risk increases
Solution Approach 1:
The constant-current limiting circuit is activated in advance during startup and short-circuit conditions to prevent excessive current flow before it can damage the power supply. By establishing current limits proactively rather than reactively, the circuit protects the power supply while still allowing full power output during normal operation when the limiting circuit is bypassed.
Solution Approach 2:
The control circuit dynamically switches between constant-current drive state and normal drive state based on real-time circuit conditions. During short circuits or startup, the dynamic switching enables predetermined current flow that protects the power supply. During normal operation, the dynamic switching transitions to full power mode, maintaining performance while adapting to operational needs.
Data Source
AI summary
There is provided an output circuit for supplying an output current to a load coupled to an output terminal in response to an input signal. The output circuit includes an output transistor for supplying the output current to the output terminal, an output-drive circuit for driving the output transistor, a constant-current limiting circuit for generating a current control signal for limiting the output current to a predetermined current value, and a control circuit for implementing a control such that the output current is controlled on the basis of the current control signal if a voltage at the output terminal is at a predetermined voltage, or less after the input signal is supplied while the output transistor is driven by the output-drive circuit if the voltage at the output terminal is in excess of the predetermined voltage.