Dual-Transistor Linear Regulator for Low Quiescent Fast Response
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Solution Overview
Problem
Existing linear regulator circuits face challenges in achieving low quiescent current consumption while maintaining fast response to load variations, especially at regulated voltage levels below five volts, which complicates design reliability and efficiency.
Innovation Solution
The proposed solution involves a linear voltage regulator circuit with a pass element configured using a small input transistor and a larger transistor, where the small transistor provides current at low demand levels and the larger transistor kicks in when demand exceeds a threshold, allowing for low quiescent current operation and fast response to load changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single large transistor is used as the pass element, then the regulator can provide sufficient current to the load, but the quiescent current consumption increases and the response speed decreases
Solution Approach 1:
The pass element is segmented into two transistors: a first transistor for low current operation and a second transistor for high current operation. This segmentation allows the regulator to use only the necessary current capability, reducing quiescent current when load demand is low while maintaining sufficient current supply when demand is high.
Solution Approach 2:
The regulator dynamically switches between the first transistor and the second transistor based on load current demand. The switching is controlled by comparing the load current to a threshold value, enabling the system to adapt its current supply capability to match actual requirements, thus optimizing both power consumption and response speed.
2Power
If a single large transistor is used as the pass element, then the regulator can provide sufficient current to the load, but the response time to load variations increases
Solution Approach 1:
The pass element is segmented into two transistors: a first transistor for low current operation and a second transistor for high current operation. This segmentation allows the regulator to use only the necessary current capability, reducing quiescent current when load demand is low while maintaining sufficient current supply when demand is high.
Solution Approach 2:
The regulator employs periodic switching between transistors based on load conditions. The switching is triggered when load current exceeds or falls below a threshold, creating a dynamic response that optimizes both speed and efficiency across different operating conditions.
3Device complexity
If conventional pass elements are used, then the circuit design is simple, but the bandwidth is limited and transient response is slow
Solution Approach 1:
The pass element is segmented into two transistors: a first transistor for low current operation and a second transistor for high current operation. This segmentation allows the regulator to use only the necessary current capability, reducing quiescent current when load demand is low while maintaining sufficient current supply when demand is high.
Solution Approach 2:
The regulator dynamically switches between the first transistor and the second transistor based on load current demand. The switching is controlled by comparing the load current to a threshold value, enabling the system to adapt its current supply capability to match actual requirements, thus optimizing both power consumption and response speed.
Data Source
AI summary
The disclosure is directed to techniques for a pass element in a linear regulator circuit. The pass element is configured with a transistor with a low input capacitance that provides current to the load for light current demand levels. When the output current exceeds a predetermined threshold, the pass element is configured to turn on a second transistor to provide the additional current. The configuration of the pass element with the regulator circuit causes the regulator circuit to operate with a low quiescent current and with large bandwidth for fast response to load changes.