Regulator Phase Compensation Circuit Reducing Chip Area
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Solution Overview
Problem
Existing constant voltage circuits face challenges in miniaturization due to the large area occupied by phase compensation capacitors, and maintaining phase compensation accuracy with a wide range of output currents is difficult, especially with the use of external phase compensation capacitors and current mirrors.
Innovation Solution
A regulator design that incorporates a phase compensation circuit with a variable resistor, where a transistor functions as a variable resistor to adjust the output impedance of a differential amplifier, reducing the need for a large phase compensation capacitor and improving phase margin across a wide range of output currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large phase compensation capacitor is used to compensate for phase shifts in the feedback loop, then the phase margin is improved and stability is enhanced, but the chip area occupied by the constant voltage circuit increases significantly
Solution Approach 1:
The patent changes the parameter of phase compensation from using a large fixed capacitor to using a variable impedance element (transistor-based circuit) whose resistance or capacitance can be dynamically adjusted. This allows the phase compensation effect to be maintained with much smaller physical dimensions, resolving the contradiction between achieving sufficient phase margin and minimizing chip area.
Solution Approach 2:
The patent replaces the traditional mechanical/electrical phase compensation capacitor with an active electronic circuit using transistors and resistors that can dynamically adjust their characteristics. This substitution enables phase compensation functionality to be achieved with significantly reduced chip area while maintaining or improving phase margin through active control.
2Reliability
If an external phase compensation capacitor is connected to achieve phase compensation, then the phase shifts are compensated, but the circuit complexity increases and miniaturization is hindered
Solution Approach 1:
The patent merges the phase compensation function with the existing circuit elements by using transistors and resistors that are already part of the constant voltage circuit architecture. Instead of adding a separate external capacitor, the phase compensation is integrated into the feedback loop using existing components, thereby reducing circuit complexity and enabling miniaturization while maintaining phase compensation accuracy.
3Reliability
If a current mirror with extreme current ratio (1/1000 or 1/10000) is used to generate mirror current for compensating output voltage drop, then the output voltage compensation is achieved, but offset errors and gain errors become difficult to control within tolerable ranges
Solution Approach 1:
The patent introduces dynamic adjustment capability to the phase compensation circuit, allowing the resistance or capacitance to vary based on operating conditions. This dynamic characteristic enables the circuit to maintain accurate phase compensation across different output current levels without relying on extreme current ratios, thereby controlling offset and gain errors within tolerable ranges while achieving output voltage compensation.
Data Source
AI summary
A regulator circuit includes an output transistor that generates an output current in accordance with a control voltage that is applied to a control terminal of the output transistor. A differential amplifier provides feedback control of the control voltage in accordance with a level of the output current. A phase compensation circuit is connected to the differential amplifier and the control terminal of the output transistor. The phase compensation circuit adjusts an output impedance of the differential amplifier. The phase compensation circuit includes a variable resistor that decreases the output impedance of the differential amplifier when the output current increases.