Noise Removal Circuit with Dynamic Amplification Control
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Solution Overview
Problem
Conventional noise filters, such as those using capacitors or passive elements like Zener diodes, often distort the original signal waveform when removing spike noise, leading to reduced sensing accuracy due to nonlinear characteristics and capacitance effects.
Innovation Solution
A noise removal circuit with a differential amplifier and current mirror circuit that dynamically controls the amplification factor based on the voltage of the electrical signal, limiting amplification at high voltages to minimize spike noise without altering the original waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a low-pass filter with capacitor is used to remove spike noise, then spike noise is removed, but the original signal waveform is blunted due to time constant
Solution Approach 1:
The patent applies dynamics by making the amplification factor variable rather than fixed. The signal amplifying section dynamically adjusts its amplification factor based on the absolute value of the input signal, allowing the system to adapt its behavior to different signal conditions and remove the need for separate filtering stages that would distort the waveform.
Solution Approach 2:
The patent merges the signal amplification function and the spike noise removal function into a single integrated circuit. The signal amplifying section performs both amplification and noise removal simultaneously by controlling the amplification factor based on the input signal characteristics, eliminating the need for separate filter components that would blur the waveform.
2Object-affected harmful factors
If passive noise removal elements such as Zener diode or varistor are used, then spike noise is removed, but the signal waveform is changed due to capacitance components and nonlinear characteristics
Solution Approach 1:
The patent replaces passive mechanical/electrical noise removal elements (such as Zener diodes, varistors, and capacitors) with an active electronic circuit consisting of a signal amplifying section with controlled gain. This substitution eliminates the nonlinear characteristics and capacitance effects of passive components while maintaining effective noise removal through electronic control of the amplification factor.
3Power
If amplification factor is increased to amplify weak signals, then signal strength is improved, but spike noise is also amplified
Solution Approach 1:
The patent applies local quality by making the amplification factor dependent on the local characteristics of the input signal. The signal amplifying section adjusts the amplification factor based on the absolute value of the input signal, providing different amplification levels for different portions of the signal. This allows weak signal portions to be amplified while spike noise portions receive reduced amplification, achieving both goals simultaneously.
Data Source
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AI summary
The noise removal circuit 1 includes: a differential amplifier circuit 11 that amplifies a voltage change signal indicating a change in motor drive current and outputs the amplified signal; a V/I converting section 12 that converts a control signal formed based on the voltage change signal into a current signal; and a current mirror circuit 13 that changes the tail current of the differential amplifier circuit 11 according to the current signal received from the V/I converting section 12 to thereby control the amplification factor of the differential amplifier circuit 11. The noise removal circuit 1 controls the tail current so that the amplification factor of the differential amplifier circuit 11 decreases as the voltage of the voltage change signal increases. When spike noise is contained in the voltage change signal, the amount of amplification at spike noise portions is suppressed by reducing the tail current and limiting the amplification factor, and a signal from which the spike noise has been removed is output.