Regulator Circuit Phase Compensation for Higher PSRR Stability
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Solution Overview
Problem
Conventional regulator circuits face challenges in effectively controlling current flow and suppressing ripple components, leading to unbalanced load and phase shifts in frequency bands, which affect the Power Supply Rejection Ratio (PSRR) and stability of output voltage.
Innovation Solution
Incorporating a filter with phase variable elements, such as capacitors or inductors, connected between the control node of a differential amplifier and the output transistor, to adjust the phase and frequency response, thereby reducing phase and amplitude differences between the voltage applied to the source and gate electrodes of the output transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional regulator circuit is used, then the circuit structure is simple, but the phase and amplitude differences between control voltages cause poor PSRR and unstable output voltage
Solution Approach 1:
A capacitor is introduced as an intermediary element connected between the control node and the source electrode of the output transistor. This capacitor mediates the interaction between control voltages and source voltage, eliminating direct coupling and reducing phase shifts. The capacitor acts as a frequency-dependent impedance that compensates for phase differences without requiring complex circuit restructuring.
Solution Approach 2:
The invention changes the electrical parameters of the regulator circuit by introducing a capacitor with specific capacitance value. This parameter change modifies the frequency response characteristics of the circuit, adjusting the phase relationship between control voltages and source voltage to optimize PSRR and output stability across different frequency bands.
2Reliability
If the circuit area is increased to improve PSRR, then output voltage stability improves, but the circuit area increases
Solution Approach 1:
The invention extracts the phase compensation function from the overall circuit structure and implements it through a single dedicated capacitor element. Instead of using complex multi-component networks or large operational amplifier stages to achieve phase alignment, the solution isolates the compensation function to one discrete component, minimizing circuit area while maintaining effective PSRR.
3Reliability
If the output transistor is controlled to reduce ripple, then output voltage stability improves, but phase shifts occur in frequency bands affecting PSRR
Solution Approach 1:
The capacitor serves as a mediator that decouples the direct phase relationship between control voltages and source voltage. By introducing this intermediary element, the circuit can control the output transistor to reduce ripple while the capacitor compensates for the resulting phase shifts, maintaining accurate phase relationships in the feedback loop across different frequency bands.
Data Source
AI summary
A regulator circuit according to one embodiment includes a first transistor, a filter, and a differential amplifier. The first transistor is provided between an input terminal on a power supply side and an output terminal on an output side. The differential amplifier includes an output node connected to the first transistor, and controls the first transistor on the basis of a result of comparison between a reference voltage and a feedback voltage according to an output voltage applied to the output terminal. The filter is connected to a control node that makes a differential pair with the output node, in the differential amplifier.