AD Converter Sampling for Ripple Reduction in Piezo Inkjet Drivers
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Solution Overview
Problem
Ink jet printers using piezoelectric elements face challenges in accurately monitoring driving signals due to remaining ripples after class D amplification, which affects the accuracy of voltage measurement and can lead to printing quality issues such as ejection failures and deteriorated resolution.
Innovation Solution
A liquid ejecting apparatus is designed with a modulation circuit, gate drivers, transistors, a lowpass filter, and an AD converter that includes multiple capacitors to sample and equalize voltages of the driving signal at different timings, reducing the influence of ripples and improving accuracy by generating an average value of the driving signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If class D amplification is used to drive piezoelectric elements, then power loss is reduced and device size is miniaturized, but ripples remain in the driving signal making voltage measurement inaccurate
Solution Approach 1:
The patent segments the voltage measurement process into multiple discrete sampling points. Instead of measuring the driving signal at a single point, the system samples the signal at K different time points (where K≥2) during the same period, thereby capturing the ripple variations and enabling accurate average voltage calculation despite the presence of ripples.
Solution Approach 2:
The patent employs periodic sampling of the driving signal at multiple time points within each driving period. By performing AD conversion at K different timings periodically and calculating the average, the system effectively filters out the ripple components while maintaining the benefits of class D amplification.
2Productivity
If multiple piezoelectric elements are driven simultaneously to increase productivity, then output is improved, but load characteristics vary making feedback control difficult
Solution Approach 1:
The patent changes the feedback control parameter from instantaneous voltage to average voltage calculated from multiple sampling points. This parameter transformation allows the feedback circuit to remain simple while accurately representing the actual voltage applied to multiple piezoelectric elements, regardless of their varying load characteristics.
3Speed
If high voltage is applied to piezoelectric elements to achieve high speed ejection, then ejection speed is improved, but voltage monitoring accuracy deteriorates due to ripple interference
Solution Approach 1:
The patent performs preliminary sampling of the driving signal at multiple time points before using the data for feedback control. By预先 capturing the voltage information at K different timings and calculating the average, the system prepares accurate voltage data that compensates for ripple effects, enabling precise monitoring even during high-speed ejection operations.
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 allows for accurate monitoring of driving signals with reduced ripple influence, enhancing the precision of voltage measurement and maintaining high printing quality by ensuring accurate ink ejection and resolution.
Implementation Method 1
a piezoelectric element that is displaced when the driving signal is applied
Implementation Method 2
a lowpass filter that smoothes the amplified modulated signal to generate a driving signal
Implementation Method 3
an AD converter that includes at least K (where K is an integer equal to or greater than 2) capacitors and a controller that causes the K capacitors to sample voltages based on the driving signal at temporally different timings, and subsequently equalizes the voltages and outputs a result of the AD conversion based on the equalized voltage
Data Source
AI summary
A liquid ejecting apparatus includes a modulation circuit that performs pulse modulation on an original signal to generate a modulated signal; a pair of transistors that generate an amplified modulated signal amplified from the modulated signal; a lowpass filter that smoothes the amplified modulated signal to generate a driving signal; an AD converter that performs AD conversion on a voltage based on the driving signal; a piezoelectric element that is displaced to eject a liquid when the driving signal is applied. The AD converter includes at least K (where K is an integer equal to or greater than 2) capacitors and a controller that causes the K capacitors to sample voltages based on the driving signal at temporally different timings, and subsequently equalizes the voltages and outputs a result of the AD conversion based on the equalized voltage.