Current-Feedback Linear Power Circuit for VCM Driver Linearity
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Solution Overview
Problem
Existing linear power source circuits for VCM drivers face challenges in achieving good linearity of input and output characteristics and preventing through currents, particularly when using voltage feedback type operational amplifiers.
Innovation Solution
The implementation of a current feedback type operational amplifier in the linear power source circuit, which includes a buffer circuit, current-voltage and voltage-current convertors, and a class-AB amplifier configuration, to enhance transimpedance, responsiveness, and oscillation stability, while preventing through currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a voltage feedback type operational amplifier is used in the linear power source circuit, then the circuit can operate with a conventional configuration, but the linearity of input and output characteristics deteriorates and through currents occur
Solution Approach 1:
The patent changes the feedback parameter from voltage feedback to current feedback, fundamentally altering the operational amplifier's feedback mechanism. This parameter change resolves the linearity issue by using current feedback to drive the output stage, which maintains better input-output linearity and prevents through currents while still using a conventional operational amplifier configuration
2Device complexity
If a voltage feedback type operational amplifier is used, then the circuit design is straightforward, but transimpedance and responsiveness are insufficient
Solution Approach 1:
The patent changes the feedback parameter from voltage to current, which directly improves transimpedance and responsiveness. The current feedback operational amplifier configuration provides higher bandwidth and faster response characteristics while maintaining manageable circuit design complexity through the use of standard operational amplifier building blocks
3Ease of manufacture
If a voltage feedback type operational amplifier is used, then the circuit can be implemented with standard components, but oscillation stability is poor
Solution Approach 1:
The patent changes the feedback mode from voltage to current, which fundamentally improves oscillation stability. The current feedback operational amplifier configuration provides inherent stability benefits due to its lower output impedance and improved phase margin characteristics, while still using standard operational amplifier components that are readily available
Data Source
AI summary
A linear power source circuit includes: an input unit to which an input signal is input and which outputs a first current signal; a current-voltage convertor which converts the first current signal into a first voltage signal; a voltage-current convertor configured to convert the first voltage signal into a second current signal; and an output unit configured to generate an output voltage signal from the second current signal by a first current mirror unit, a second current mirror unit, and a third current mirror unit, and configured to output the output voltage signal to an output terminal. The input unit and the current-voltage convertor constitute a current feedback type operational amplifier.