LDO Regulator Correction Loop for Voltage Stability
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Solution Overview
Problem
Conventional low dropout (LDO) regulators fail to maintain stable output voltage when subjected to large dv/dt and di/dt variations, leading to potential transistor destruction and performance degradation in applications like laser drivers.
Innovation Solution
Incorporating a negative feedback correction loop with a programmable current sink element into the LDO regulator circuit, which has a bandwidth less than the main voltage regulation loop, to correct the output voltage by comparing it to a reference voltage and adjusting the sink current accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional LDO regulators are used with high bandwidth main voltage regulation loop, then fast response to supply variations is achieved, but output voltage stability deteriorates under large dv/dt and di/dt variations
Solution Approach 1:
The voltage regulation system is divided into two separate loops: a main voltage regulation loop for fast response and a correction loop for stability. The main loop handles high-frequency variations while the correction loop addresses low-frequency drift, allowing each loop to be optimized independently for its specific function without compromising the other.
Solution Approach 2:
A correction loop with negative feedback is implemented to monitor and adjust the output voltage. This feedback mechanism detects deviations in output voltage caused by large supply variations and automatically corrects them, ensuring long-term stability while the main loop maintains fast response capability.
2Speed
If the correction loop bandwidth is made higher to respond faster to output variations, then response speed improves, but the correction loop becomes ineffective at filtering low-frequency drift and supply variations
Solution Approach 1:
The system employs dynamic bandwidth allocation where the main voltage regulation loop operates at high bandwidth for fast transient response, while the correction loop operates at low bandwidth to filter out low-frequency drift and supply variations. Each loop's bandwidth is dynamically suited to its specific correction task, optimizing overall system performance.
3Device complexity
If the main voltage regulation loop operates independently without correction loop, then device complexity is reduced, but output voltage stability under large supply variations deteriorates
Solution Approach 1:
The voltage regulation functionality is segmented into two distinct loops with separate control mechanisms. The main loop handles basic voltage regulation while the correction loop specifically addresses stability issues under supply variations. This segmentation allows the system to achieve enhanced stability without significantly increasing overall complexity, as each loop has a dedicated and simplified function.
Data Source
AI summary
Techniques that can prevent the low dropout (LDO) output voltage degradation that occurs with conventional LDO regulators, even with large LDO supply variations. An LDO regulator circuit can include another loop that is much slower than the main LDO regulator loop, concentrates the load regulation, and fixes the voltage regulation runaway problem due to the large supply variation with large frequency content. The LDO regulator circuit can include a negative feedback correction loop that corrects the LDO output by, in some examples, adding sink current to the main voltage regulation loop via a programmable current sink element.