LDO Compensation Circuit Using Low-Voltage Capacitor for Stability
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Solution Overview
Problem
High-rated voltage capacitors required for stability in LDO circuits occupy larger chip areas, increasing cost and size, especially when output voltage is high.
Innovation Solution
A compensation circuit with a low-rated voltage compensation capacitor is used to introduce a zero point into the open-loop transfer function of the linear voltage regulator, reducing the chip area required for the capacitor by generating a feedback voltage lower than the output voltage through a resistor divider and using a compensation capacitor with a low rated voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitor with high rated voltage is used to maintain stability at high output voltage, then system stability is improved, but chip area increases
Solution Approach 1:
The patent segments the voltage regulation function into two independent parts: (1) a resistor divider network that steps down the high output voltage to a lower feedback voltage, and (2) a compensation capacitor that operates at this lower voltage level. This segmentation allows the capacitor to be sized for the lower feedback voltage rather than the full output voltage, reducing chip area while maintaining stability through the feedback control mechanism.
Solution Approach 2:
The resistor divider network acts as an intermediary between the high-voltage output node and the compensation capacitor. It transforms the high output voltage into a lower feedback voltage, allowing the compensation capacitor to operate at reduced voltage stress. This intermediary structure enables the use of a smaller, lower-rated voltage capacitor while still achieving the required stability compensation function.
2Reliability
If a capacitor with high rated voltage is used to ensure stability, then system stability is improved, but manufacturing cost increases
Solution Approach 1:
By segmenting the voltage regulation function using a resistor divider network, the patent enables the compensation capacitor to operate at a lower voltage level. This segmentation reduces the capacitor's rated voltage requirement, which directly lowers both component cost and chip area, thereby improving ease of manufacture while preserving stability through feedback control.
Solution Approach 2:
The resistor divider serves as an intermediary that decouples the high-voltage output requirement from the compensation capacitor's operating voltage. This intermediary structure allows the use of a cheaper, lower-rated voltage capacitor in the integrated circuit, reducing overall manufacturing cost while maintaining system stability through the feedback mechanism.
Data Source
AI summary
A linear voltage regulator includes a transistor, an error amplifier, a feedback circuit and a compensation circuit. The transistor has a first terminal for receiving an input voltage, a second terminal for providing an output voltage, and a control terminal. The error amplifier has a first input terminal, a second input terminal and an output terminal, wherein the first input terminal receives a reference voltage, and the output terminal is coupled to the control terminal of the transistor. The feedback circuit receives the output voltage and generates a feedback voltage lower than the output voltage. The compensation circuit is configured to receive the feedback voltage and generate a compensation voltage at the second input terminal of the error amplifier. The compensation circuit includes a compensation capacitor for introducing a zero point into an open-loop transfer function of the linear voltage regulator to improve system stability.