Adaptive-Bias LDO Regulator for Fast Load-Change Stability
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Solution Overview
Problem
Low dropout (LDO) regulators face challenges in stabilizing output voltage when faced with rapid changes in load currents, particularly in high-rate operating memory devices and electronic devices.
Innovation Solution
The proposed LDO regulator incorporates a voltage regulating circuit that uses output voltage as first feedback and an adaptive biasing circuit that generates a biasing signal using a sensing signal from an internal node, to support the regulation of output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LDO regulator uses only output voltage feedback for regulation, then the circuit structure remains simple, but the output voltage cannot be stabilized when load current changes rapidly
Solution Approach 1:
The patent introduces a dual feedback mechanism: (1) output voltage feedback through the voltage regulating circuit that compares output voltage with a reference voltage, and (2) internal node voltage feedback through the adaptive biasing circuit that senses the voltage at the second node (proportional to load current) and generates a biasing signal. This dual feedback approach enables the regulator to respond to both voltage deviations and load current changes, stabilizing output voltage under rapid load transitions while maintaining reasonable circuit complexity through systematic integration of feedback paths.
Solution Approach 2:
The patent transitions from single-loop voltage feedback to a two-dimensional control approach by adding current feedback through the adaptive biasing circuit. The biasing circuit generates a biasing signal based on the sensing signal from the internal node, creating an additional control dimension that compensates for load current effects. This dimensional expansion allows independent optimization of voltage regulation and load response without fundamentally redesigning the entire system.
2Speed
If the LDO regulator responds slowly to load current changes, then the circuit remains stable, but it cannot meet the requirements of high-rate operating memory devices
Solution Approach 1:
The adaptive biasing circuit performs preliminary action by sensing the voltage at the second node (which is proportional to load current) before the output voltage significantly deviates. The biasing signal generated from this sensing signal proactively adjusts the operating point of the voltage regulating circuit, preparing it for anticipated load changes. This preliminary detection and adjustment mechanism enables faster response to load current variations while maintaining output voltage stability through coordinated action between the two feedback paths.
Data Source
AI summary
An example low dropout (LDO) regulator includes a voltage regulating circuit and an adaptive biasing circuit. The voltage regulating circuit is configured to regulate an output voltage of an output node connected with a load by using the output voltage as first feedback. The adaptive biasing circuit is configured to generate a biasing signal that supports regulation of the output voltage by using a sensing signal in an internal node of the voltage regulating circuit as second feedback, and to provide the biasing signal to the voltage regulating circuit.