Piezoelectric Head Drive Circuit Layout for Stable Self-Oscillation
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Solution Overview
Problem
Existing liquid discharge apparatuses using piezoelectric elements for inkjet printing face challenges in energy efficiency and print quality due to the complexity of class D amplification systems, which require additional oscillation circuits and can result in abnormal oscillations and frequency variations.
Innovation Solution
A liquid discharge apparatus with a simplified configuration that includes a modulation circuit, a pair of transistors, a low-pass filter with an inductor and capacitor, and a piezoelectric element, where the shortest distance between the low-side transistor and capacitor is shorter than the high-side transistor and capacitor, allowing for class D amplification without a separate oscillation circuit, thereby preventing print quality deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If class D amplification is implemented with a separate oscillation circuit, then energy efficiency is improved, but device complexity increases
Solution Approach 1:
The patent merges the oscillation circuit functionality into the amplifier circuit itself, eliminating the need for a separate oscillation circuit. The amplifier circuit generates self-oscillation through its internal feedback mechanism, combining what were previously separate functions into a single integrated circuit block, thereby reducing device complexity while maintaining energy efficiency.
Solution Approach 2:
The amplifier circuit is designed to perform multiple functions: it provides class D amplification for energy efficiency while simultaneously generating the necessary oscillation signals through self-oscillation. This multi-functional design eliminates the need for dedicated separate circuits for each function, reducing overall system complexity.
2Reliability
If a separate oscillation circuit is added for frequency stabilization, then frequency stability is improved, but device complexity increases
Solution Approach 1:
The patent implements a feedback mechanism within the amplifier circuit where the output signal is fed back to the input through a feedback path. This feedback controls the self-oscillation frequency, ensuring frequency stability without requiring external oscillation circuits. The feedback loop automatically adjusts to maintain stable operation.
Solution Approach 2:
The amplifier circuit is designed to generate and stabilize its own oscillation frequency through self-oscillation mechanisms. The circuit serves itself by internally generating the reference signal and maintaining frequency stability through its own feedback control, eliminating the need for external frequency stabilization circuits.
3Object-affected harmful factors
If the distance between high-side transistor and capacitor is reduced, then parasitic inductance is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs asymmetric layout design where the low-side transistor is positioned closer to the capacitor than the high-side transistor. This asymmetric arrangement optimizes the parasitic inductance characteristics by minimizing the critical current path length to the capacitor, while the design tolerances are set to accommodate manufacturing variations.
Solution Approach 2:
The patent applies different design considerations to different parts of the circuit: the low-side transistor is positioned with specific precision relative to the capacitor to minimize parasitic inductance, while other parts of the circuit have different tolerance requirements. This localized optimization allows high precision where needed without requiring uniform high precision throughout the entire circuit.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances energy efficiency, stabilizes self-oscillation frequency, and prevents abnormal oscillations, ensuring high print quality by maintaining a frequency range of 1 MHz to 8 MHz and minimizing parasitic inductance and wiring impedance.
Implementation Method 1
a piezoelectric element that is displaced by application of the drive signal thereto
Implementation Method 2
a low-pass filter that includes an inductor and a capacitor and smoothes the amplified modulated signal to generate a drive signal
Data Source
AI summary
A liquid discharge apparatus includes: a modulation circuit that generates a modulated signal by pulse-modulating a source signal through self-oscillation; a pair of transistors that include a high-side transistor and a low-side transistor and amplify the modulated signal to generate an amplified modulated signal; a low-pass filter that includes an inductor and a capacitor and smoothes the amplified modulated signal to generate a drive signal; a piezoelectric element that is displaced by application of the drive signal thereto; a cavity that is filled with a liquid inside and has an internal volume which changes when the piezoelectric element is displaced; and a nozzle that is provided to discharge the liquid inside the cavity in response to the change of the internal volume of the cavity. A shortest distance between the low-side transistor and the capacitor is shorter than a shortest distance between the high-side transistor and the capacitor.