Constant-Voltage Power Supply Circuit Positive Feedback Load Regulation
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Solution Overview
Problem
Existing constant-voltage power supply circuits exhibit poor load regulation characteristics, particularly at low output currents, leading to significant voltage drops as output current increases, which is undesirable for efficient power supply performance.
Innovation Solution
Incorporating a positive feedback circuit between the output terminal of the error amplifier and the gate of the output transistor, along with specific transistor configurations and feedback resistor arrangements, to enhance the gain of the error amplifier and reduce the risk of oscillation, thereby improving load regulation across the entire output current range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high resistance value resistors are used for output voltage detection to reduce current consumption, then current consumption is reduced, but load regulation characteristics deteriorate at low output currents
Solution Approach 1:
The patent introduces positive feedback from the output terminal to the non-inverting input terminal of the error amplifier. This feedback mechanism compensates for the voltage drop caused by high resistance detection resistors at low output currents, thereby maintaining both low current consumption and good load regulation characteristics simultaneously
Solution Approach 2:
The patent changes the operating parameters of the error amplifier by applying positive feedback voltage to its non-inverting input terminal. This parameter change allows the system to maintain accurate voltage regulation despite using high resistance detection resistors, resolving the contradiction between current consumption and load regulation performance
2Reliability
If the error amplifier gain is increased to improve load regulation characteristics, then load regulation characteristics are improved, but the risk of oscillation increases
Solution Approach 1:
The patent uses positive feedback specifically tuned to improve load regulation without causing oscillation. By controlling the feedback amount and using it in conjunction with the existing negative feedback loop, the system achieves better load regulation while maintaining stability, avoiding the oscillation problem that would result from simply increasing the error amplifier gain
Solution Approach 2:
The patent introduces an intermediary positive feedback path that mediates between the output voltage and the error amplifier input. This intermediary mechanism allows for fine-tuned adjustment of the amplifier's effective gain, improving load regulation while preventing the direct gain increase that would cause oscillation
Data Source
AI summary
According to one embodiment, a constant-voltage power supply circuit includes: an error amplifier including an inverting input terminal and a noninverting input terminal, a reference voltage source connected with the inverting input terminal of the error amplifier, an output transistor, the transistor having a source connected with a power supply terminal, a drain connected with a circuit output terminal, and a gate connected with an output terminal of the error amplifier, and an output voltage detecting circuit, the circuit being connected between the circuit output terminal and a power supply terminal, detecting voltage of the circuit output terminal to apply the detected voltage to the noninverting input terminal of the error amplifier. The constant-voltage power supply circuit further includes a positive feedback circuit connected between the output terminal of the error amplifier and the gate of the output transistor.