Biasing Stage Current Control Under LDO Dropout Conditions
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Solution Overview
Problem
Existing low-dropout (LDO) voltage regulators, buffers, and amplifiers face issues with uncontrolled power consumption, adverse load transient behavior, and lack of monitoring when the supply voltage approaches or equals the output voltage, leading to unnecessary power consumption and voltage drops.
Innovation Solution
A control loop system comprising a comparator and amplifier is implemented to manage the drain-source voltage across a transistor, ensuring reduced current consumption and stable AC stability, with a digital flag for dropout monitoring and automatic bypass mode activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the supply voltage approaches or equals the output voltage in prior art LDOs, then the voltage regulator operates in dropout conditions, but power consumption becomes uncontrolled and load transient behavior deteriorates
Solution Approach 1:
The patent implements a control loop that continuously monitors the supply voltage and adjusts the biasing current accordingly. When dropout conditions are detected (supply voltage approaching output voltage), the control loop reduces the biasing current to maintain stable operation, thereby controlling power consumption while preserving load transient behavior through active feedback adjustment
Solution Approach 2:
The biasing stage transitions from a static biasing arrangement to a dynamic one where the biasing current can be adjusted in real-time based on supply voltage conditions. This dynamic adjustment allows the system to adapt to dropout conditions by reducing current consumption while maintaining reliable load transient response
2Adaptability or versatility
If bypass mode is implemented in prior art circuits, then the circuit can operate under dropout conditions, but power consumption increases significantly
Solution Approach 1:
The bypass mode is implemented dynamically with automatic activation based on supply voltage monitoring. The control loop detects when dropout conditions occur and automatically switches to bypass mode with reduced biasing current, providing adaptability while minimizing power consumption through conditional rather than continuous bypass operation
Solution Approach 2:
The system changes the operating parameters of the bypass mode based on supply voltage conditions. When dropout is detected, the biasing current parameter is reduced while maintaining bypass functionality, allowing the circuit to adapt to dropout conditions with optimized power consumption rather than fixed high-current bypass operation
3Device complexity
If no control loop is used in the biasing stage, then the circuit is simpler, but power consumption cannot be controlled when supply voltage equals output voltage
Solution Approach 1:
A control loop with feedback mechanism is introduced to monitor supply voltage and adjust biasing current accordingly. This feedback system enables automatic power consumption control during dropout conditions by comparing supply voltage against reference levels and adjusting the biasing stage parameters in real-time
Solution Approach 2:
The control loop acts as an intermediary between the supply voltage source and the biasing stage. It processes supply voltage information and generates appropriate control signals to adjust the biasing current, serving as a mediator that enables intelligent power management without requiring complex direct control of the biasing transistors
Data Source
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AI summary
Circuits and methods to control current through a device biasing an output device in case the supply voltage is not higher than the output voltage are disclosed. The circuits and methods are applicable to e.g. LDOs, amplifiers, or buffers. A control loop detects if the supply voltage is not higher than the output voltage and regulates the drain-source voltage of the biasing device. The disclosure reduces power consumption in a driver stage in case the supply voltage is not higher than the output voltage.