Drive Signal Circuit Layout for Low-Noise Liquid Ejection Heads
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Solution Overview
Problem
Class D amplifier circuits used in liquid ejection apparatuses for piezoelectric elements suffer from waveform accuracy reduction due to switching noise caused by large currents, which affects the precision of the drive signals used for ink ejection in printers.
Innovation Solution
The liquid ejection apparatus includes a drive signal output circuit with a modulation circuit, an amplifier circuit, and a demodulation circuit, where the demodulation circuit is strategically located between the modulation and amplifier circuits on a substrate, and capacitive elements are positioned to minimize noise interference, optimizing the layout to reduce switching noise impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a class D amplifier circuit is used to supply sufficient current to the piezoelectric element, then power consumption is reduced and energy conversion efficiency is improved, but switching noise is generated that reduces waveform accuracy of the drive signal
Solution Approach 1:
The amplifier circuit is divided into multiple independent transistor pairs, each responsible for specific switching operations. This segmentation isolates the noise-generating switching actions from the signal processing path, allowing the drive signal to maintain high waveform accuracy while still utilizing the energy-efficient class D amplification architecture.
Solution Approach 2:
A noise filtering circuit is introduced as an intermediary component between the amplifier circuit and the drive signal output. This filtering circuit acts as a mediator that removes switching noise from the amplified signal while preserving the original waveform characteristics, thereby resolving the contradiction between energy efficiency and waveform accuracy.
2Power
If a transistor pair switches to generate an amplified modulation signal in a class D amplifier circuit, then current amplification is achieved, but switching noise is generated that superimposes on circuit elements and reduces signal accuracy
Solution Approach 1:
The harmful switching noise is extracted and separated from the useful amplified signal through the noise filtering circuit. By taking out the noise component and removing it from the signal path, the circuit maintains current amplification capability while eliminating the harmful switching noise that would otherwise superimpose on other circuit elements.
Solution Approach 2:
The switching noise, which is an inherent byproduct of the class D amplification process, is converted from a harmful factor into a manageable parameter through the filtering circuit. The filtering circuit is designed to selectively remove noise frequencies while preserving the signal frequencies, thereby transforming the noise problem into a controlled filtering operation that maintains overall system performance.
Data Source
AI summary
A liquid ejection apparatus includes a liquid ejection head that ejects a liquid by driving a drive element, a drive signal output circuit that outputs a drive signal for driving the drive element, and a substrate provided with the drive signal output circuit, wherein the drive signal output circuit includes a modulation circuit that modulates an original drive signal to output a modulation signal, an amplifier circuit that amplifies the modulation signal to output an amplified modulation signal, and a demodulation circuit that demodulates the amplified modulation signal to output the drive signal for driving the drive element, and wherein the demodulation circuit is located, on the substrate, between the modulation circuit and the amplifier circuit.