Dual-Loop Voltage Regulator for Fast LDO Transient Response
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Solution Overview
Problem
Existing low dropout (LDO) regulators struggle to quickly compensate for abrupt changes in output voltage due to their reliance on a single feedback loop, leading to instability and the need for large output capacitors that increase manufacturing costs.
Innovation Solution
A voltage regulator design incorporating a fast feedback loop and a slow feedback loop, utilizing a compensator, buffer circuit, pass transistor, and additional transistors to rapidly compensate for abrupt changes and maintain output voltage stability through a combination of fast and slow feedback mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single feedback loop is used in LDO regulator, then the circuit complexity is reduced, but the response speed to output voltage changes is slow
Solution Approach 1:
The feedback loop is segmented into two independent loops: a fast feedback loop that responds to abrupt output voltage changes and a slow feedback loop that maintains steady-state stability. This segmentation allows each loop to be optimized for its specific function, resolving the contradiction between response speed and stability.
Solution Approach 2:
The system dynamically switches between fast and slow feedback modes based on operating conditions. The fast feedback loop uses a common gate amplifier configuration for rapid response, while the slow feedback loop uses a common source amplifier for stability, allowing the system to adapt its characteristics to different operational states.
2Productivity
If a fast feedback loop is added to improve response speed, then the compensation speed increases, but the device complexity increases
Solution Approach 1:
The fast and slow feedback loops are merged into a unified voltage regulator circuit that shares common components such as the pass transistor, compensator, and buffer circuit. This merging allows the system to achieve fast compensation capability while minimizing the increase in overall device complexity through component sharing.
Solution Approach 2:
The buffer circuit and compensator serve dual functions in both the fast and slow feedback loops, providing multi-functionality that reduces the need for separate dedicated components for each feedback path, thereby limiting the increase in device complexity.
3Stability of the object's composition
If large output capacitors are used to maintain stability, then the output voltage stability is improved, but the manufacturing cost increases
Solution Approach 1:
The dual feedback loop system provides active voltage regulation that maintains output stability through feedback control rather than relying on passive capacitor sizing. The fast feedback loop quickly corrects voltage deviations, reducing the need for large output capacitors to maintain stability, thereby lowering manufacturing costs.
Data Source
AI summary
A voltage regulator providing an output voltage includes; a compensator receiving a reference voltage and a first feedback voltage corresponding to the output voltage and generating a comparison voltage in response to the reference voltage and the first feedback voltage, a buffer input control circuit receiving the comparison voltage and generating a buffer input voltage in response to the comparison voltage and a second feedback voltage, a buffer circuit receiving the buffer input voltage and generating a gate voltage in response to the buffer input voltage, a pass transistor generating an output voltage at an output voltage node in response to the gate voltage, and a fast voltage compensating circuit generating the second feedback voltage in response to the output voltage.