Linear Regulator Gain Boosting via Positive Feedback
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Solution Overview
Problem
Existing methods for increasing the open loop gain of linear regulators, such as using cascade stages or positive feedback, often introduce complexity and stability issues, limiting the potential for gain boosting without hardware overhead.
Innovation Solution
A linear regulator design that incorporates a positive feedback loop with a gain greater than or equal to 0.8 and a negative feedback loop, along with a transfer function featuring two poles, allowing for unconditional stability and high open loop gain without additional hardware, achieved by selecting appropriate feedback gains and pole placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cascade stages are used to increase open loop gain, then the open loop gain is improved, but the design complexity increases and stability issues arise
Solution Approach 1:
The patent combines the gain boosting function with the existing error amplifier by integrating a positive feedback loop into the single-stage amplifier architecture. This merging approach achieves high open loop gain without requiring separate cascade stages, thereby avoiding increased design complexity while maintaining stability through unified compensation design.
Solution Approach 2:
The patent applies positive feedback to the error amplifier to boost the open loop gain. By carefully designing the feedback network with specific gain values and pole placements, the system achieves theoretically infinite open loop gain while maintaining unconditional stability, eliminating the need for complex multi-stage cascade structures.
2Measurement precision
If positive feedback is used to boost open loop gain, then the open loop gain is improved, but the amplifier becomes unstable during operation
Solution Approach 1:
The patent changes the parameters of the feedback system by introducing a second pole at a higher frequency than the first pole. This parameter configuration (p1 < p2) ensures that the positive feedback does not cause instability while achieving high open loop gain, as the phase margin is maintained through proper pole placement.
Solution Approach 2:
The patent uses positive feedback with carefully controlled gain and pole placement to boost open loop gain while maintaining stability. The feedback network is designed with specific constraints (gain ≥ 0.8, two poles with p1 < p2) that ensure unconditional stability during operation, preventing oscillations while achieving theoretically infinite open loop gain.
3Measurement precision
If gain boosting is implemented in LDOs, then power supply rejection ratio and load regulation are improved, but hardware overhead is introduced
Solution Approach 1:
The patent merges the gain boosting functionality into the existing error amplifier of the LDO by adding a positive feedback loop. This integration approach improves power supply rejection ratio and load regulation without requiring separate gain boosting hardware stages, thereby avoiding additional hardware overhead while achieving high open loop gain.
Solution Approach 2:
The error amplifier in the LDO is designed to serve multiple functions: voltage amplification, error signal generation, and gain boosting through positive feedback. This multi-functional design improves PSR and load regulation without requiring dedicated gain boosting components, eliminating hardware overhead while achieving theoretically infinite open loop gain.
Data Source
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AI summary
The present document relates to linear regulators. In particular, the present document relates to a method and a system for increasing the open loop gain of linear regulators. A linear regulator (100) configured to derive an output voltage (112) from an input voltage (111) is described. The linear regulator (100) comprises an amplifier (102) configured to derive an amplifier output signal from an amplifier input signal, and a pass device (103) configured to convert the amplifier output signal into the output voltage (112). Furthermore, the linear regulator (100) comprises a positive feedback loop configured to determine a positive feedback signal from the amplifier output signal, using a positive feedback gain y (104), and a negative feedback loop configured to determine a negative feedback signal from the output voltage (108), using a negative feedback gain ² (105). In addition, the linear regulator (100) comprises a combining unit (101) configured to determine the amplifier input signal from the input voltage (111), from the positive feedback signal and from the negative feedback voltage. A transfer function of the linear regulator exhibits a first and a second pole at a first frequency wp 1 and at a second frequency wp2, respectively.