Voltage Regulator Feedback Isolation for Fast Stable Response
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Solution Overview
Problem
Conventional voltage regulators with high loop gain suffer from instability and slow response times due to the need for frequency compensation, which limits their ability to maintain tightly regulated voltages in the face of sudden load changes.
Innovation Solution
The implementation of an isolation circuit that decouples the frequency compensation capacitor from the output transistor's gate, allowing for high-frequency negative feedback without charging or discharging the capacitor, thereby maintaining a fast response time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If frequency compensation circuit is used to prevent instability, then stability is improved, but response time deteriorates
Solution Approach 1:
The patent segments the feedback path into two distinct paths: a high-frequency feedback path that bypasses the compensation capacitor for rapid response, and a low-frequency feedback path that includes the compensation capacitor for stability. This segmentation allows the system to simultaneously achieve both fast response time and stability by routing different frequency components through different paths.
Solution Approach 2:
The patent introduces an intermediary component (such as a resistor or inductor) in series with the compensation capacitor to create a frequency-dependent feedback network. This intermediary element acts as a mediator that allows high-frequency signals to bypass the capacitor's charging/discharging delay while still providing low-frequency compensation for stability.
2Measurement precision
If high loop gain is used to tightly control output voltage, then voltage regulation precision is improved, but stability deteriorates
Solution Approach 1:
The patent changes the effective feedback impedance parameters dynamically by using frequency-selective components. At low frequencies, the compensation capacitor provides high impedance to reduce loop gain and prevent oscillation. At high frequencies, the capacitor's impedance decreases, allowing full loop gain to be applied for tight voltage regulation, thus resolving the stability-precision contradiction through parameter variation with frequency.
3Ease of operation
If compensation capacitor is charged/discharged to drive regulated voltage, then voltage control is achieved, but speed deteriorates
Solution Approach 1:
The patent segments the feedback current path so that high-frequency correction currents can flow through a separate path that bypasses the compensation capacitor. This allows rapid voltage corrections to occur without being limited by the capacitor's charging/discharging time constant, while the capacitor continues to provide necessary low-frequency voltage control.
Solution Approach 2:
The patent allows the high-frequency feedback path to provide excessive or partial correction action for rapid response, while the compensation capacitor provides the remaining partial action for steady-state voltage control. This partial action approach enables the system to achieve both fast transient response and accurate long-term regulation.
Data Source
AI summary
Circuits, devices and methods are provided, such as an amplifier (e.g., a voltage regulator) that includes a feedback circuit that supplies negative feedback through a feedback path. One such feedback path includes a capacitance coupled in series with a “one-way” isolation circuit through which a feedback signal is coupled. The “one-way” isolation circuit may allow the feedback signal to be coupled from a “downstream” node, such as an output node, to an “upstream” node, such as a node at which an error signal is generated to provide negative feedback. However, the “one-way” isolation circuit may substantially prevent variations in the voltage at the upstream node from being coupled to the capacitance in the isolation circuit. As a result, the voltage at the upstream node may quickly change since charging and discharging of the capacitance responsive to voltage variations at the upstream node may be avoided.