Piezoelectric Drive Circuit Layout for EMI-Resistant Liquid Discharge
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Solution Overview
Problem
Existing liquid discharge apparatuses face challenges in reducing noise interference from high-voltage circuits on low-voltage circuits, leading to distorted driving waveforms and decreased discharge accuracy in ink jet heads.
Innovation Solution
A liquid discharge apparatus with a driving circuit that includes a transistor pair, a comparator, a gate driver, and a linear amplifier, where the output end of the transistor pair is connected to an output node, and the comparator, gate driver, and linear amplifier are integrated in an IC device, with specific terminal placements to minimize noise influence, allowing for accurate feedback signal processing and reduced noise impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a class D amplifier is used to drive the piezoelectric element at high frequency (1 to 8 MHz), then discharge accuracy is improved, but electromagnetic interference (EMI) noise is generated that affects low-voltage circuits
Solution Approach 1:
The driving circuit is divided into separate high-voltage and low-voltage circuit regions on the IC chip. The high-voltage driving circuit (transistor pair, gate driver) is spatially segmented from the low-voltage control circuits (comparator, linear amplifier), with dedicated power source voltage supply lines for each region. This segmentation isolates the EMI-generating high-voltage switching operations from the noise-sensitive low-voltage feedback signal processing paths.
Solution Approach 2:
The high-voltage driving function is extracted as a separate module with its own power source voltage supply line (supplying second power source voltage higher than first power source voltage). The transistor pair and gate driver operate at high voltage to generate the driving signal, while the comparator and linear amplifier operate at low voltage for precise feedback processing. This extraction allows independent optimization of each circuit region's voltage level and noise immunity.
2Device complexity
If high-voltage and low-voltage circuits are integrated in the same IC chip, then device complexity is reduced, but noise from high-voltage circuit disturbs low-voltage circuit operation
Solution Approach 1:
Different regions of the IC chip are assigned different voltage qualities and noise immunity characteristics. The high-voltage driving region tolerates higher noise levels, while the low-voltage feedback region maintains high signal integrity. The power source voltage supply lines are routed to provide appropriate voltage levels to each region, with the second power source voltage (higher) for the driving circuit and first power source voltage (lower) for the control circuit, creating local quality differences that enable coexistence of high and low voltage circuits on the same chip.
3Power
If current amplification is performed before class AB amplifier, then sufficient current is supplied to piezoelectric element, but energy efficiency deteriorates
Solution Approach 1:
The driving circuit uses a class D amplifier topology with switching transistors that operate in saturation/cutoff regions rather than linear regions. The transistor pair switches between on and off states, efficiently transferring power to the piezoelectric element without the continuous power dissipation characteristic of linear amplifiers. This parameter change from linear to switching operation maintains sufficient current supply capability while dramatically improving energy efficiency.
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
The solution effectively reduces noise interference from high-voltage circuits, improving the accuracy of the driving signal and enhancing discharge precision in the liquid discharge apparatus.
Implementation Method 1
A piezoelectric element is provided corresponding to each of a plurality of nozzles in the head unit, each of the piezoelectric elements is driven according to a driving signal, and accordingly, a predetermined amount of ink (liquid) is discharged from the nozzle at a predetermined timing to form dots.
Implementation Method 2
a linear amplifier which amplifies a voltage of an original driving signal by predetermined times and outputs the voltage based on a second feedback signal
Implementation Method 3
a comparator for comparing a voltage of an original driving signal which is an origin of the driving signal with a voltage of a first feedback signal which is a signal fed back from the driving signal
Data Source
AI summary
There is provided a liquid discharge apparatus including: a discharge unit which discharges a liquid by applying a driving signal to a piezoelectric element; and a driving circuit which outputs the driving signal based on an original driving signal, in which the driving circuit includes a transistor pair for outputting the driving signal, a first gate driver which generates a first control signal, and a linear amplifier which amplifies a voltage of the original driving signal, in which a first output terminal from which the first control signal is output, a first input terminal to which a first feedback signal, and a second input terminal to which a second feedback signal, and in which the shortest distance between the first output terminal and the first input terminal is longer than the shortest distance between the first output terminal and the second input terminal.