Series Regulator Circuit Phase Margin Stabilization
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Solution Overview
Problem
Existing series regulator circuits face challenges in maintaining stable voltage output with low current consumption, particularly when the capacitance of the load changes, which can lead to insufficient phase margin and unstable feedback control.
Innovation Solution
A series regulator circuit design that includes a first transistor connected to a constant current source and a reference voltage line, with a second transistor connected to the input voltage line and an output terminal, and a third transistor connected between the input voltage line and a connection node of resistors, ensuring stable voltage output by maintaining a sufficient phase margin of 90 degrees or greater through a PD control system and secondary delay element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a two-stage voltage amplification circuit is used to reduce current consumption, then current consumption is reduced, but phase margin becomes insufficient and stability deteriorates
Solution Approach 1:
A capacitor is introduced as an intermediary element in the feedback path between the output terminal and the control terminal of the second transistor. This capacitor acts as a phase compensation element that adds a leading phase effect, thereby increasing the phase margin without requiring additional active amplification stages that would consume more current.
Solution Approach 2:
The invention changes the electrical parameters of the feedback path by introducing a capacitor with specific capacitance value. This parameter change modifies the frequency response characteristics of the circuit, creating a zero in the transfer function that compensates for phase lag and improves stability margin while maintaining the low-current two-stage architecture.
2Speed
If a three-stage voltage amplification circuit is used to improve response and increase GB product, then response is improved, but current consumption increases
Solution Approach 1:
The invention extracts the essential function of phase compensation from the third amplification stage, removing the need for a complete third stage. By taking out only the necessary phase compensation function and implementing it through a passive capacitor in the feedback path, the circuit achieves adequate phase margin and stability without the current consumption penalty of a full third amplification stage.
Solution Approach 2:
Instead of implementing a full third amplification stage, the invention applies partial action by using a single capacitor element that provides just enough phase compensation to achieve the required phase margin. This partial compensation approach is sufficient to ensure stability while consuming minimal current, avoiding the excessive current consumption of a complete third stage.
3Adaptability or versatility
If the capacitance of the load changes, then adaptability is affected, but phase margin becomes insufficient leading to instability
Solution Approach 1:
The capacitor in the feedback path creates a feedback mechanism that automatically compensates for changes in load capacitance. As load capacitance varies, the feedback network adjusts the phase response dynamically, maintaining adequate phase margin across different loading conditions. This feedback-based phase compensation ensures both adaptability to different loads and maintained stability.
Data Source
AI summary
A series regulator circuit for supplying voltage with low current consumption without depending on the capacitance of a load. A constant current source, which is connected to an input voltage line, is connected to a ground voltage line via a bipolar transistor. The gate terminals of first and second n-channel MOS transistors are connected between the constant current source and the collector terminal of the bipolar transistor. The drain terminals of the first and second transistors are connected to the input voltage line. The source terminal of the transistor functioning as an output terminal is connected via a first resistor element to the source terminal of the first terminal, which is connected to a ground voltage line via second and third resistor elements. A connection node between the second and third resistor elements is connected to a base voltage of the bipolar transistor.