Power Supply Circuit Overcurrent Protection Feedback Path
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Solution Overview
Problem
The existing power supply circuits have a relatively long feedback path, leading to delayed overcurrent protection response and instability due to circuit oscillation, which is not effectively addressed by prior art.
Innovation Solution
The power supply circuit incorporates an overcurrent protection mechanism that monitors the output current of the output transistor through a current detection transistor, limiting the drain current of the buffer transistor to control the output current, thereby shortening the feedback path and improving response and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the existing power supply circuit configuration is used, then the circuit can provide overcurrent protection, but the feedback path is relatively long causing delayed response and circuit oscillation
Solution Approach 1:
The invention extracts the overcurrent protection function from the traditional long feedback path and implements it through a dedicated current detection transistor Tr3 that directly monitors the output current. This separate detection path bypasses the error amplifier and buffer transistor, creating a direct feedback loop that significantly shortens the feedback path and eliminates circuit oscillation while maintaining reliable overcurrent protection.
2Stability of the object's composition
If the existing power supply circuit configuration is used, then the circuit can regulate output voltage, but the circuit experiences oscillation and instability
Solution Approach 1:
The invention introduces a direct feedback mechanism through current detection transistor Tr3 that provides real-time overcurrent protection by monitoring the output current directly. This feedback path bypasses the error amplifier and buffer transistor, creating a short and stable feedback loop that prevents circuit oscillation while maintaining voltage regulation through the original error amplifier path.
Data Source
AI summary
A power supply circuit includes an output transistor including a source coupled to power supply voltage, and a drain from which output voltage is outputted; a first error amplifier powered by the power supply voltage and outputting a signal based on a potential difference between the output voltage and a reference voltage; a buffer transistor including a gate coupled to the output of the first error amplifier, and a source coupled via a constant current source to the power supply voltage and coupled to a gate of the output transistor; a current detection transistor coupled to the output transistor such that a gate and source are shared; and an overcurrent protection circuit configured to limit the drain current of the buffer transistor based on the increase of the drain current of the current detection transistor and thereby control the output current of the output transistor.