Linear Power Supply Voltage Clamping for Stable Output
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Solution Overview
Problem
Linear power supplies face instability due to large variations in input voltage, leading to variations in transistor characteristics, making it difficult to sustain stable power output.
Innovation Solution
Incorporating a second transistor to clamp the drain-source voltage of the first transistor, maintaining it at a fixed value, and using a controller to adjust the gate voltage based on feedback and reference voltages, allowing for stable operation even with varying input voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a linear power supply uses a single transistor to regulate output voltage, then the circuit structure is simple, but the power supply becomes unstable when input voltage varies significantly
Solution Approach 1:
The power supply circuit is divided into two separate transistor stages: a first transistor for voltage regulation and a second transistor for clamping the drain-source voltage. This segmentation allows each transistor to perform a specific function independently, improving overall stability without excessive complexity
Solution Approach 2:
The second transistor acts as an intermediary element that clamps the drain-source voltage of the first transistor to a fixed value. This intermediary component isolates the first transistor from input voltage variations, enabling stable operation
2Device complexity
If the drain-source voltage of the transistor varies with input voltage, then the circuit configuration is simple, but the transistor characteristics vary leading to unstable output
Solution Approach 1:
The second transistor is configured to clamp the drain-source voltage of the first transistor before the first transistor performs its voltage regulation function. This preliminary clamping action ensures that the first transistor operates with a fixed drain-source voltage, maintaining consistent characteristics
Solution Approach 2:
The invention changes the operating parameter of the first transistor by fixing its drain-source voltage through the second transistor. This parameter control ensures that the first transistor's characteristics remain consistent despite variations in input voltage
3Adaptability or versatility
If higher withstand voltage transistors are used to handle input voltage variations, then the power supply can tolerate larger voltage swings, but the transistor size and cost increase
Solution Approach 1:
The voltage handling function is segmented between two transistors: the first transistor handles voltage regulation with a fixed drain-source voltage, allowing it to be smaller, while the second transistor handles the voltage clamping function. This segmentation enables the use of smaller, lower-withstand-voltage transistors
Solution Approach 2:
The second transistor serves as a protective intermediary that absorbs the voltage stress through clamping, allowing the first transistor to operate with lower voltage stress and thus use smaller dimensions
Data Source
AI summary
A linear power supply includes: a first transistor configured to be connectable between an input terminal configured to input an input voltage thereto and an output terminal configured to output an output voltage therefrom; a reference voltage generator configured to generate a reference voltage; a controller configured to control the first transistor based on the difference between a feedback voltage reflecting the output voltage and the reference voltage; and a second transistor configured to be connectable between the input terminal or the output terminal and the first transistor and configured to clamp the first terminal-to-second terminal voltage of the first transistor.