Linear Regulator Bias Control for Fast Transient Response
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Solution Overview
Problem
Prior art linear regulators face challenges in achieving fast load transient response while maintaining low quiescent current, especially when there is no output capacitor, as the bias current is fixed and cannot be adjusted effectively.
Innovation Solution
The proposed fast response linear regulator incorporates a pre-stage circuit and an output stage circuit with a bias current circuit, a bias load circuit, a power transistor, and a voltage positioning transistor, along with an overshoot detecting circuit and suppressors to dynamically adjust the bias current and conduction resistance, allowing for effective overshoot and undershoot suppression without an external capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the bias current is increased to achieve fast load transient response, then the response speed is improved, but the quiescent current increases
Solution Approach 1:
The bias current is transformed from a fixed value to a dynamically adjustable parameter. The circuit includes a bias current control module that can adjust the bias current based on operating conditions, allowing high current during transients and low current during steady state, thus resolving the contradiction between response speed and quiescent current consumption
Solution Approach 2:
The invention changes the parameter of bias current from constant to variable. By introducing control circuits that can modify the bias current magnitude according to load conditions, the system achieves fast response when needed while maintaining low power consumption during normal operation
2Stability of the object's composition
If the bias current is increased to suppress overshoot and undershoot, then the output stability is improved, but the quiescent current increases
Solution Approach 1:
The invention implements feedback mechanisms through overshoot/undershoot detection circuits that monitor the output voltage and provide feedback signals to adjust the bias current accordingly. This allows the system to maintain output stability by suppressing voltage excursions only when necessary, rather than continuously maintaining high bias current
Solution Approach 2:
The bias current is dynamically adjusted based on detected output conditions. When overshoot or undershoot is detected, the bias current is increased to correct the deviation; when output is stable, the bias current is reduced, thus achieving stability without continuous high current consumption
3Device complexity
If a fixed bias current is used, then the circuit complexity is reduced, but the adaptability to different load conditions deteriorates
Solution Approach 1:
The circuit incorporates dynamic control elements including bias current adjustment circuits and overshoot/undershoot suppression circuits that enable the fixed-structure circuit to adapt to varying load conditions through real-time parameter adjustment
Solution Approach 2:
The bias current control module serves multiple functions: it adjusts bias current for fast transient response, suppresses overshoot, prevents undershoot, and maintains low quiescent current. This multi-functionality within a unified control structure achieves high adaptability without proportionally increasing circuit complexity
Data Source
AI summary
A fast response amplifier circuit includes a pre-stage circuit and an output stage circuit. The pre-stage circuit generates a control signal according to a difference between a first input signal and a second input signal. The output stage circuit generates an output signal at an output node according to the control signal. The output stage circuit includes: a power transistor controlled by a driving signal to generate the output signal; a voltage positioning transistor operates according to the output signal to steer a first portion and a second portion of a bias current; an overshoot detecting circuit detecting an overshoot of the output signal to generate an overshoot indicating signal; and a first overshoot suppressor which generates a first overshoot suppressing signal according to the overshoot indicating signal to adjust a conduction resistance of the power transistor to suppress an overshoot of the output signal.