Low-Dropout Regulator Feedback Clamping for Stable Quiescent Current
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Solution Overview
Problem
Existing low-dropout regulators experience indefinite increases in quiescent current with load current, leading to poor stability and efficiency due to unnecessary energy loss.
Innovation Solution
Incorporating a clamping current source between the feedback switching transistor and the input voltage, allowing the feedback switching transistor to be completely turned on at a predetermined load current, limiting the feedback current to the value of the clamping current source, and partially turned on at lower load currents, maintaining proportional feedback current to the load current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the quiescent current is increased to ensure load transient regulation capability and stability, then the load capacity and transient regulation are improved, but the energy loss increases and efficiency decreases
Solution Approach 1:
The patent implements dynamic quiescent current adjustment by using the feedback current (proportional to load current) to control the bias current of the error amplifier. When load current is high, the quiescent current is increased to maintain stability and transient regulation. When load current is low, the quiescent current is automatically reduced to minimize energy loss. This dynamic adaptation resolves the contradiction between reliability and energy loss.
2Power
If the quiescent current is increased to provide larger output load capacity, then the load capacity is improved, but the overall circuit efficiency decreases
Solution Approach 1:
The patent employs dynamic quiescent current adjustment where the bias current of the error amplifier is controlled by the feedback current which is proportional to the load current. This ensures that sufficient quiescent current is provided when large output load capacity is needed, while automatically reducing quiescent current when load demand is low, thereby maintaining high circuit efficiency across different operating conditions.
3Reliability
If the quiescent current increases indefinitely with load current, then the biasing components have sufficient current, but the circuit stability and efficiency deteriorate
Solution Approach 1:
The patent implements a feedback mechanism where the feedback current (proportional to load current) is used to control the bias current of the error amplifier. This feedback loop ensures that the quiescent current automatically adapts to the load conditions: increasing when load current increases to maintain stability, and decreasing when load current decreases to reduce power loss, thus resolving the contradiction between stability and power loss.
4Reliability
If a higher quiescent current is used for biasing components, then the transient regulation capability is improved, but the negative effects such as poor stability and decreased efficiency occur
Solution Approach 1:
The patent implements dynamic quiescent current adjustment by using the feedback current to control the error amplifier bias current. This ensures sufficient quiescent current is available when transient regulation capability is needed (high load conditions), while automatically reducing quiescent current under light load conditions to eliminate negative effects like poor stability and decreased efficiency, thus resolving the contradiction between transient regulation capability and efficiency.
Data Source
AI summary
The present disclosure relates to a low-dropout regulator that limits a quiescent current. It mainly includes an error amplifier, an output switching transistor, a feedback switching transistor, a current duplicating circuit, and a clamping current source. The clamping current source is added between an input voltage and the feedback switching transistor, so that a feedback current outputted by the feedback switching transistor is clamped, and the highest value is only proportional to a current value of the clamping current source. In this way, the quiescent current outputted by the low-dropout regulator is no longer increasing indefinitely in proportional to a load current, which can effectively solve the technical problems of poor stability and decreased efficiency caused by the infinite increase of the quiescent current.