Overcurrent Protection Circuit Using Replica Transistor and Dynamic Reference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
There is a need for a device that can supply current to a load while preventing overcurrent conditions, as loads may drain currents of varying values, and existing solutions lack effective mechanisms to set and enforce upper current limits.
Innovation Solution
A device incorporating a main transistor, a replica transistor, an amplifier, and a variable signal source to provide overcurrent protection by biasing the transistors with a reference signal that changes between two values based on the load current, ensuring the load current does not exceed a predefined threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed reference signal is used to limit the load current, then the device structure is simple, but the device cannot adapt to varying load conditions and maintain precise current limiting
Solution Approach 1:
The reference signal is changed from a fixed value to a dynamically adjustable value that varies with the main transistor's drain-source voltage. This dynamic reference signal enables the overcurrent protection circuit to adapt to different operating conditions and load variations, resolving the contradiction between adaptability and structural simplicity.
Solution Approach 2:
The circuit uses feedback from the main transistor's drain-source voltage to adjust the reference signal level. This feedback mechanism allows the overcurrent protection to respond to changing load conditions automatically, achieving adaptability without requiring complex external control systems.
2Measurement precision
If the reference signal is adjusted dynamically based on main transistor voltage, then the current limiting precision is improved, but the device complexity increases
Solution Approach 1:
An intermediate circuit stage is introduced between the main transistor and the overcurrent protection comparison stage. This intermediary circuit processes the main transistor's drain-source voltage to generate the appropriate reference signal, achieving precise current limiting while keeping the overall device structure manageable through modular design.
3Measurement precision
If a replica transistor with smaller current is used, then the overcurrent protection accuracy is improved, but the device complexity increases
Solution Approach 1:
A replica transistor is introduced to create a scaled-down version of the main transistor's current. This copy circuit generates a replica current that is proportional to but smaller than the main transistor current, enabling accurate overcurrent detection at lower current levels while maintaining a relatively simple transistor-based implementation.
Data Source
AI summary
A device for overcurrent protection, the device may include a main transistor that is configured to supply, via an output node, a load current to a load; a current limiting resistor; a replica transistor that is configured to provide a replica current to the current limiting resistor; wherein the replica current is smaller than the load current, wherein a value of the replica current is responsive to a value of the load current; an amplifier; a current limiting transistor; a variable signal source that is configured to output a reference signal; wherein a value of the reference signal is based on a main transistor voltage; wherein the amplifier is configured to prevent the load current from exceeding a first load current threshold by biasing the main transistor and the replica transistor with a bias signal; wherein a value of the bias signal is responsive to the reference signal and to the replica current.