Short Circuit Protection Circuit Using Current Mirror Transistors
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Solution Overview
Problem
Conventional short circuit protection circuits face challenges with increased chip area and current consumption, and often omit protection in smaller chip designs to conserve space and power, resulting in insufficient protection for short circuits.
Innovation Solution
A short circuit protection circuit configuration using a first transistor and a resistor serially connected between the source and drain of an output transistor, along with a second transistor forming a current mirror, and optionally a third transistor to synchronize conduction and cutoff of current paths, integrated with a driver circuit and output transistor to manage current and area efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional short circuit protection circuit with a comparator is used to detect overcurrent, then short circuit protection is provided, but chip area increases and current consumption increases
Solution Approach 1:
The patent extracts the overcurrent detection function from a conventional comparator-based protection circuit and implements it using only transistor components (Q1-Q3) that can be integrated into the existing output stage. This removes the need for separate comparator circuits, thereby reducing chip area while maintaining protection functionality.
Solution Approach 2:
The transistor Q1 serves dual purposes: it acts as part of the output push-pull stage (along with Q2) and simultaneously functions as the detection element for overcurrent protection. The transistor Q3 further serves both as an output device and as part of the protection mechanism. This multi-functionality reduces the total component count and chip area.
2Reliability
If a conventional short circuit protection circuit with a comparator is used to detect overcurrent, then short circuit protection is provided, but current consumption increases
Solution Approach 1:
The protection circuit operates in a periodic manner: during normal operation, the transistors Q1 and Q2 conduct alternately as part of the push-pull output stage, and the protection transistor Q3 remains off. When overcurrent is detected, Q3 turns on to clamp the output voltage and limit current. This periodic operation mode minimizes continuous current consumption while providing protection when needed.
Solution Approach 2:
The protection circuit uses the existing output transistors Q1 and Q2 to provide the detection function, eliminating the need for separate dedicated detection components that would consume additional current. The circuit serves itself by utilizing the operational states of the output transistors to detect overcurrent conditions.
3Area of stationary object
If short circuit protection is omitted in smaller chip designs to conserve space, then chip area is reduced, but protection for short circuit becomes insufficient
Solution Approach 1:
The patent merges the protection circuit functionality with the existing output push-pull stage by using transistors Q1, Q2, and Q3 that are already part of or can be easily integrated into the output stage. This consolidation eliminates the need for separate protection circuitry, allowing small chip designs to include protection without significant area increase.
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 a short circuit protection circuit with reduced area and current consumption, effectively protecting against overcurrent while maintaining detection precision and minimizing current consumption during normal operation.
Implementation Method 1
a second transistor connected between the source and the gate or the emitter and the collector of the output transistor and forming a current mirror with the first transistor
Data Source
AI summary
The present disclosure provides a short circuit protection circuit with small area and less current-consuming. A short circuit protection circuit 14 includes a transistor M11 and a resistor R11, serially connected between a source and a drain of an output transistor 11 (transistor M10); and a transistor M12, connected between the source and a gate of the output transistor 11 and forming a current mirror together with the transistor M11.