Linear Power Supply Circuit Phase Compensation
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Solution Overview
Problem
Linear power supply circuits face challenges in achieving high-speed response and phase compensation without significantly increasing circuit area, especially when the capacitance of the output capacitor is reduced, leading to difficulties in maintaining stable output voltage during rapid load changes.
Innovation Solution
The proposed linear power supply circuit incorporates a driver with a differential amplifier, a converter, and a current amplifier, along with a phase compensation circuit that includes a parallel transistor and capacitance, allowing the shifting of pole frequencies to lower frequencies without affecting the output capacitor, thereby enabling high-speed response and phase compensation without increasing circuit area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the capacitance of the output capacitor is reduced, then the circuit area is reduced, but the phase compensation becomes difficult and the response speed decreases
Solution Approach 1:
The patent segments the phase compensation function into two independent parts: one part uses the output capacitor for basic compensation, while the other part uses a dedicated phase compensation circuit with capacitor C2 and resistor R2 to adjust the pole frequency. This segmentation allows the output capacitor to be reduced in size without compromising phase compensation performance, as the dedicated circuit takes over that function.
Solution Approach 2:
The patent introduces an intermediary phase compensation circuit that mediates between the output capacitor and the amplifier's response characteristics. This circuit, comprising C2 and R2, acts as a buffer that allows independent optimization of the output capacitor size while maintaining proper phase compensation through adjustable pole frequency.
2Area of stationary object
If the capacitance of the output capacitor is reduced, then the circuit area is reduced, but the output voltage stability deteriorates during rapid load changes
Solution Approach 1:
The patent segments the voltage stabilization function between the output capacitor (for basic filtering) and the phase compensation circuit (for active stabilization). This allows the output capacitor to be minimized while the phase compensation circuit with adjustable pole frequency provides the necessary stability during load transients.
Solution Approach 2:
The patent changes the parameter of pole frequency in the phase compensation circuit to optimize stability. By adjusting the pole frequency through the R2-C2 network, the system maintains stable output voltage even with a reduced output capacitor, as the phase compensation circuit compensates for the reduced capacitance effect.
3Reliability
If a traditional phase compensation method is used, then the phase compensation is effective, but the circuit area significantly increases
Solution Approach 1:
The patent segments the compensation function so that the output capacitor handles basic compensation while a minimal phase compensation circuit (R2-C2) handles pole frequency adjustment. This segmentation achieves effective phase compensation with minimal additional circuit area, unlike traditional methods that require large compensation capacitors.
Solution Approach 2:
The patent uses parameter changes in the phase compensation circuit to achieve effective compensation with small components. By optimizing the pole frequency through R2 and C2, the system achieves reliable phase compensation without requiring large capacitor values that would increase circuit area.
Data Source
AI summary
A linear power supply circuit, includes: output transistor between input terminal where input voltage is applied and output terminal where output voltage is applied; a driver driving the output transistor based on difference between voltage based on the output voltage and reference voltage; and phase compensation circuit, wherein the driver includes differential amplifier outputting voltage corresponding to the difference between the voltage based on the output voltage and the reference voltage, a first capacitance having one end where output of the differential amplifier is applied and the other end where ground potential is applied, a converter converting the voltage based on the output of the differential amplifier into current, and a current amplifier amplifying the current output from the converter, and wherein the phase compensation circuit lowers gain of transfer function of the linear power supply circuit and output capacitor connected to the output terminal.