Linear Regulator Dropout Control Using Load Current Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Linear regulators face challenges in maintaining regulated output voltage during dropout conditions, where input voltage decreases, leading to potential output voltage overshoot and increased power consumption due to varying load currents and temperatures.
Innovation Solution
A dropout control circuit is implemented, which includes a dropout error amplifier and driver circuit to regulate the output voltage by maintaining a target dropout voltage across the pass element, derived as a function of load current and temperature, ensuring stable operation and reducing power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the linear regulator uses a fixed dropout voltage control, then the circuit is simple to implement, but the output voltage cannot be maintained during dropout conditions and power consumption increases
Solution Approach 1:
The patent implements dynamic dropout voltage control where the dropout reference voltage is adjusted based on load current and temperature conditions. The dropout error amplifier dynamically modifies the reference voltage level to maintain proper regulation across varying operating conditions, transitioning from static to dynamic control to resolve the contradiction between reliability and complexity.
Solution Approach 2:
The patent changes the dropout voltage parameter dynamically based on operating conditions. By monitoring load current and temperature, the system adjusts the dropout reference voltage parameter to maintain optimal regulation performance, thereby improving reliability without requiring completely new control architecture.
2Reliability
If the dropout voltage is increased to maintain regulation, then output voltage stability improves, but power loss increases due to higher voltage drop across the pass element
Solution Approach 1:
The patent dynamically adjusts the dropout voltage parameter based on load current and temperature conditions. Under light load conditions, the dropout voltage is reduced to minimize power loss, while under heavy load or temperature variations, it is increased to maintain stability, thus resolving the contradiction between reliability and energy loss.
Solution Approach 2:
The system transitions from fixed dropout voltage to dynamic adjustment, allowing the dropout voltage to adapt to changing operating conditions. This dynamic behavior enables the system to optimize the balance between output stability and power efficiency in real-time.
3Device complexity
If the linear regulator operates without load current based control, then the circuit is simpler, but output voltage overshoot occurs during dropout conditions
Solution Approach 1:
The patent implements feedback control through the dropout error amplifier that continuously monitors the output voltage and adjusts the pass element control accordingly. This feedback mechanism prevents output voltage overshoot during dropout conditions by actively compensating for deviations, resolving the contradiction between simplicity and stability.
Solution Approach 2:
The system takes preliminary action by anticipating dropout conditions through load current monitoring and adjusting the dropout reference voltage before voltage regulation fails. This proactive control prevents overshoot and maintains stability without requiring complex reactive correction circuits.
Data Source
AI summary
In a linear regulator system, a pass element has a control terminal, an input terminal and an output terminal. The pass element is configured to provide an output voltage at the output terminal based on: an input voltage at the input terminal; and a control signal at the control terminal. A dropout error amplifier has an error output and first and second inputs. The first input is coupled to the output terminal, and the error output is coupled to the control terminal. The dropout error amplifier is configured to provide a dropout control signal at the error output based on a comparison between: the output voltage at the first input; and a dropout reference voltage at the second input. The pass element is configured to regulate the output voltage at the dropout reference voltage, responsive to the dropout control signal.