LDO Regulator Ultra-Low Quiescent Current Transient Response
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Solution Overview
Problem
Low dropout (LDO) regulators face challenges in reducing power consumption while maintaining accurate operation, as ultra-low quiescent current consumption can negatively impact load transient behavior, power supply rejection ratio (PSRR), and output voltage noise, particularly in battery-operated devices.
Innovation Solution
The implementation of an LDO regulator with an ultra-low quiescent current, featuring a bandgap voltage reference circuit filtered by RC and noise filters, along with a transconductance amplifier and bias current source, improves PSRR and load transient behavior by generating a stable reference voltage and adjusting bias currents based on load variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If quiescent current is reduced to ultra-low levels, then battery life is extended, but load transient behavior deteriorates
Solution Approach 1:
The bias current generation circuit dynamically adjusts the bias current based on operating conditions. The transconductance amplifier modifies the bias current in response to load transient events, allowing the system to have ultra-low quiescent current during normal operation while providing sufficient current during transient conditions to maintain stable output voltage.
Solution Approach 2:
The patent changes the parameter of bias current from a fixed ultra-low value to a variable value that can be adjusted based on circuit needs. The transconductance amplifier enables the bias current to transition between different levels, achieving both ultra-low quiescent current and acceptable load transient behavior through parameter modulation.
2Use of energy by moving object
If quiescent current is reduced to ultra-low levels, then power consumption is minimized, but power supply rejection ratio (PSRR) deteriorates
Solution Approach 1:
The bias current is dynamically adjusted based on the operating state of the LDO regulator. During normal low-power operation, the bias current remains at ultra-low levels to minimize power consumption. When power supply disturbances occur, the transconductance amplifier detects the disturbance and increases the bias current to improve PSRR, thereby rejecting power supply noise effectively.
Solution Approach 2:
The transconductance amplifier provides feedback control by monitoring the output voltage and adjusting the bias current accordingly. This feedback mechanism enables the circuit to maintain good PSRR by increasing bias current in response to power supply disturbances, while keeping quiescent current ultra-low during normal operation when no disturbances are present.
3Use of energy by moving object
If quiescent current is reduced to ultra-low levels, then battery life is extended, but output voltage noise increases
Solution Approach 1:
The bias current generation circuit dynamically adjusts the bias current level based on circuit conditions. The transconductance amplifier enables the bias current to increase when output voltage disturbances are detected, thereby reducing output noise. During normal operation with no disturbances, the bias current remains at ultra-low levels to extend battery life.
Solution Approach 2:
The patent employs parameter changes by modulating the bias current between ultra-low and higher levels based on operating conditions. The transconductance amplifier changes the bias current parameter in response to output voltage disturbances, achieving low noise performance when needed while maintaining ultra-low quiescent current for battery life extension.
Data Source
AI summary
An apparatus includes at least one filter configured to filter a reference voltage to generate a filtered reference voltage. The apparatus also includes an amplifier configured to amplify a difference between the filtered reference voltage and a feedback voltage to generate a drive signal. The apparatus further includes a first transistor configured to generate an output voltage based on the drive signal, where the feedback voltage is based on the output voltage. The apparatus also includes a second transistor configured to generate a first bias current for the amplifier based on the drive signal. In addition, the apparatus includes a voltage-to-current converter configured to generate a second bias current for the amplifier based on the reference voltage and the feedback voltage. The second transistor can generate higher first bias currents during higher load currents, and the voltage-to-current converter can generate higher second bias currents during faster load current variations.