LDO Regulator Architecture for Low-Voltage Large-Load Stability
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Solution Overview
Problem
Low dropout regulators (LDO regulators) face challenges in operating efficiently with relatively low input voltages, especially when handling large loads, as the error amplifier may not function properly due to shared input voltage with the driving transistor, leading to potential operational issues and increased current consumption.
Innovation Solution
The LDO regulator design separates the input voltage for the driving transistor and the error amplifier, using a PMOS transistor connected between the input line and the gate terminal of the driving transistor to reduce unnecessary current consumption and eliminate the need for a pull-up element, allowing for stable operation even with low input voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the input voltage is lowered to save power in large load LDO regulators, then power efficiency is improved, but the error amplifier cannot operate normally
Solution Approach 1:
The patent segments the power supply into two separate paths: one path supplies the driving transistor with low input voltage for power efficiency, while another path supplies the error amplifier with sufficient voltage through a dedicated boost circuit for reliable operation. This segmentation allows each component to receive appropriate voltage levels independently.
Solution Approach 2:
The patent introduces a boost circuit as an intermediary component that takes the low input voltage and generates a higher voltage specifically for the error amplifier. This intermediary mechanism resolves the conflict by providing the error amplifier with the voltage headroom it needs without requiring the main input voltage to be high.
2Stability of the object's composition
If a pull-up element is used to maintain gate terminal voltage, then operational stability is improved, but current consumption increases
Solution Approach 1:
The patent replaces the static pull-up element with a dynamic switching mechanism controlled by the driving controller. The switch dynamically connects or disconnects the gate terminal based on operational state, eliminating continuous current consumption while maintaining voltage stability when needed. This dynamic approach removes the trade-off between stability and power consumption.
Solution Approach 2:
The driving controller monitors the operational state and automatically controls the switching element to maintain gate terminal voltage only when necessary. This self-service mechanism ensures voltage stability during critical operations while eliminating unnecessary current consumption during normal operation, making the system adapt its own power management.
Data Source
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Figure 3A~3C
AI summary
A low dropout regulator can comprise a driver configured to receive a first input voltage and generates an output voltage, an error amplifier configured to receive a second input voltage having a magnitude different from the first input voltage and output an amplifier output voltage based on the difference between a feedback voltage corresponding to the output voltage and a reference voltage, and a driving controller configured to control the output voltage of the driver based on the amplifier output voltage.