Flipped Voltage Follower LDO Compensation for Fast Stable Regulation
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Solution Overview
Problem
Conventional low-dropout regulators consume substantial power due to large feedback loop unity gain bandwidths, and their frequency compensation techniques reduce speed and have poor power supply noise rejection.
Innovation Solution
A voltage regulator using a flipped voltage follower circuit with a folded cascode feedback network and a compensation capacitor coupled between the output node and a folding node for frequency compensation, which reduces power consumption and enhances noise rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional frequency compensation techniques are used in low-dropout regulators, then stability is improved, but speed is reduced and power supply noise rejection is poor
Solution Approach 1:
The patent changes the configuration parameters of the feedback circuit by using a folded cascode structure with specific transistor arrangements and a compensation capacitor connected between the output node and the folding node. This parameter change in the circuit topology achieves both stability and high-speed performance simultaneously, resolving the contradiction between stability and speed in conventional frequency compensation techniques
2Adaptability or versatility
If large feedback loop unity gain bandwidths are used for wide dynamic range of load currents, then dynamic range is improved, but power consumption increases substantially
Solution Approach 1:
The patent changes the operational parameters of the output transistor by configuring it as a common-source amplifier circuit with the source terminal coupled to the input power supply node and the drain terminal coupled to the output regulated power supply node. This parameter change enables the circuit to achieve wide dynamic range adaptability while maintaining low power consumption through optimized current paths and transistor operating points
3Reliability
If conventional low-dropout regulator design is used, then voltage regulation is achieved, but power supply noise rejection is poor
Solution Approach 1:
The patent introduces a folded cascode feedback circuit as an intermediary element between the output transistor and the input. This intermediate feedback structure with the compensation capacitor provides enhanced noise filtering and rejection capabilities while maintaining stable voltage regulation, effectively blocking power supply noise from affecting the regulated output
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution achieves fast load regulation with low leakage current and high power supply noise rejection, while maintaining stability across a wide range of load conditions.
Implementation Method 1
The compensation capacitor is coupled to the output regulated power supply node and the folding node
Data Source
AI summary
A voltage regulator includes an input power supply node, an output regulated power supply node, a flipped voltage follower circuit, and a compensation capacitor. The flipped voltage follower circuit includes an output transistor configured as a common-source amplifier circuit. A source terminal of the output transistor is coupled to the input power supply node and a drain terminal of the output transistor is coupled to the output regulated power supply node. The flipped voltage follower circuit includes a folded cascode feedback circuit. The folded cascode feedback circuit includes a folding node. The folded cascode feedback circuit is configured to receive an output regulated voltage on the output regulated power supply node and to provide a feedback signal to a gate terminal of the output transistor. The compensation capacitor is coupled to the output regulated power supply node and the folding node.