LDO Regulator Dynamic Zero Compensation for Stability
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Solution Overview
Problem
Conventional low-dropout (LDO) regulators face challenges in maintaining stability under variable load conditions due to the movement of non-dominant poles, leading to potential oscillations and inefficiencies in compensation, especially when using fixed zero compensation methods or high quiescent current consumption.
Innovation Solution
The implementation of a dynamic zero-compensation circuit and a compensation control circuit that adjusts the frequency of the zero to track the non-dominant pole, using a PMOS transistor as a variable resistor and a Miller compensation circuit, allowing the zero to cancel the non-dominant pole across varying load currents, thereby maintaining phase margin and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Miller compensation is used to introduce a zero to cancel the non-dominant pole, then stability is improved, but the compensation becomes ineffective when the non-dominant pole location changes due to variable load conditions
Solution Approach 1:
The patent applies the Dynamics principle by making the compensation zero frequency adjustable rather than fixed. A control circuit dynamically adjusts the compensation capacitor value based on the operating conditions, specifically tracking the non-dominant pole location as load current varies. This allows the zero frequency to adapt and remain effective for pole cancellation under different load conditions, resolving the contradiction between stability and adaptability.
2Reliability
If the non-dominant pole is moved far away from the unity gain frequency, then stability is improved, but quiescent current consumption increases significantly
Solution Approach 1:
The patent applies the Parameter changes principle by dynamically adjusting the compensation capacitor value based on operating conditions rather than using a fixed large capacitor value. The control circuit modifies the effective capacitance to track the non-dominant pole location, allowing stability to be maintained with much lower quiescent current consumption. This resolves the contradiction by changing the parameter (capacitance value) adaptively rather than using a permanently large value.
Data Source
AI summary
A low-drop out (LDO) regulator circuit is provided having a gate of a pass transistor coupled to an output of an operational transconductance amplifier, the LDO regulator exhibiting a non-dominant pole at an output of the LDO. A dynamic zero-compensation circuit is coupled in parallel to the pass transistor. A compensation control circuit is coupled and configured to adjust a frequency, at which a zero is generated, and cause the generated zero to track with the non-dominant pole.