Hybrid LDO Regulator With Dynamic Bandwidth and PSRR Control
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Solution Overview
Problem
Existing low-dropout (LDO) regulators face challenges in maintaining power supply rejection ratio (PSRR), quiescent current, and loop bandwidth tradeoffs, especially when the voltage source is close to the output voltage.
Innovation Solution
A low-dropout regulator incorporating an analog low-dropout (ALDO) circuit assisted by a digital low-dropout (DLDO) circuit that senses operating information to adjust current and bandwidth based on the ALDO's operating region, using comparators and an analog-to-digital converter (ADC) to control current and capacitance, thereby stabilizing the ALDO's operation point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the voltage source drops lower and closer to the output voltage, then the regulator operates in low-dropout mode, but the power supply rejection ratio deteriorates
Solution Approach 1:
The patent implements dynamic adjustment of the loop bandwidth based on the operating conditions. When the voltage source drops closer to the output voltage, the system dynamically reduces the loop bandwidth to maintain adequate power supply rejection ratio. This is achieved through a controller that adjusts the bandwidth control signal based on the voltage differential between the source and output, allowing the regulator to adapt its performance characteristics to the current operating point.
2Speed
If the loop bandwidth is increased to improve response speed, then the regulator responds faster to load changes, but the power supply rejection ratio deteriorates
Solution Approach 1:
The system dynamically adjusts the loop bandwidth based on operating conditions rather than using a fixed bandwidth. The controller monitors the voltage differential and load conditions, then adjusts the bandwidth control signal to optimize the balance between response speed and power supply rejection ratio. This allows the regulator to have wide bandwidth when needed for fast response and narrow bandwidth when needed for high PSRR.
3Use of energy by moving object
If the quiescent current is reduced to improve power efficiency, then the power consumption decreases, but the loop bandwidth and response capability are limited
Solution Approach 1:
The patent employs dynamic adjustment of the loop bandwidth and operating parameters based on real-time conditions. The controller adjusts the bandwidth control signal according to the voltage differential and load requirements, allowing the system to achieve high power efficiency during light-load or steady-state operation while maintaining adequate response capability when load changes occur. This dynamic operation allows the regulator to optimize the trade-off between quiescent current and loop bandwidth.
Data Source
AI summary
A low-dropout (LDO) regulator having an analog low-dropout (ALDO) regulating circuit and a digital low-dropout (DLDO) regulating circuit. The DLDO regulating circuit assists the ALDO regulating circuit based on a sensed voltage different from an output voltage at the output terminal of the LDO regulator. The DLDO regulating circuit has a controller operating based on the two comparators. The controller controls a current that the DLDO regulating circuit provides to a load. The first comparator compares the sensed voltage with an upper limit voltage in default, and changes to comparing the sensed voltage with a medium threshold voltage in response to the sensed voltage exceeding the upper limit voltage. The second comparator compares the sensed voltage with a lower limit voltage in default, and changes to comparing the sensed voltage with the medium threshold voltage in response to the sensed voltage dropping lower than the lower limit voltage.