Capacitive Load Driving Circuit Noise Suppression

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Solution Overview

Problem

In liquid discharging apparatuses like ink jet printers, high oscillation frequencies required for accurate ink discharge lead to noise interference, affecting the precision of piezoelectric element operation, which is not adequately addressed by existing amplifiers.

Innovation Solution

A circuit configuration with a low voltage system block and a second high voltage system block that does not perform switching operations, positioned between a first high voltage system block that performs switching, to suppress noise and enhance modulation signal accuracy, thereby improving voltage control over piezoelectric elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If high oscillation frequency (1 MHz to 8 MHz) is used in class-D amplifier for ink jet, then discharge accuracy of liquid is improved, but noise interference increases

Engineering Contradiction:

Improvedischarge accuracyVSAvoidnoise interference

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The circuit is divided into separate low voltage system circuit block and high voltage system circuit block. The low voltage block contains the modulation portion that generates modulation signals, while the high voltage block contains switching elements. This segmentation isolates the noise-generating switching operations from the sensitive signal generation circuits, allowing high oscillation frequency operation for accurate discharge while preventing noise from degrading signal quality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A second high voltage system circuit block is introduced as an intermediary between the low voltage system circuit block and the first high voltage system circuit block. This intermediate block acts as a buffer that prevents direct noise coupling from the switching operations to the modulation signal generation circuits, enabling the system to operate at high frequencies with improved discharge accuracy while maintaining low noise levels.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of energy

If class-D amplifier is used instead of class-AB amplifier, then energy efficiency is improved, but discharge accuracy deteriorates due to noise

Engineering Contradiction:

Improveenergy efficiencyVSAvoiddischarge accuracy

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The amplifier is segmented into distinct low voltage and high voltage circuit blocks with separate functional responsibilities. The low voltage block handles precise signal modulation while the high voltage block performs power amplification and switching. This segmentation allows the system to achieve both the energy efficiency of class-D amplification and the discharge accuracy of precision signal control by preventing noise from the power stage from affecting the signal stage.

Inventive Principle:

Principle #1Segmentation

3Power

If switching operation is performed in high voltage circuit block, then power amplification is achieved, but noise is generated that affects low voltage circuit block

Engineering Contradiction:

Improvepower amplificationVSAvoidnoise interference

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The circuit architecture segments power amplification functions into a dedicated high voltage system circuit block separated from the low voltage signal generation block. This segmentation allows aggressive switching operations for efficient power amplification while physically and electrically isolating the noise from the sensitive low voltage circuits.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second high voltage system circuit block serves as an intermediary that decouples the noise-generating switching operations from the signal-sensitive low voltage circuits. This intermediate stage allows power amplification to proceed with full switching action while preventing noise from propagating to the modulation portion, thereby maintaining both power efficiency and signal integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 improves the discharge accuracy of liquid droplets by reducing noise interference and ensuring precise voltage control, optimizing the frequency range of 1 MHz to 8 MHz for effective ink discharge.

Implementation Method 1

a piezoelectric element which is displaced as the driving signal is applied

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS9522528B2Liquid discharging apparatus, head unit, integrated circuit device for capacitive load driving, and capacitive load driving circuit

Publication Date: 2016.12.20 SEIKO EPSON CORP

AI summary

There is provided a liquid discharging apparatus including: a low voltage system circuit block including a modulation portion which generates a modulation signal pulse-modulated from a source signal; a transistor which generates an amplification modulation signal amplified from the modulation signal; a first high voltage system circuit block which receives the signal from the low voltage system circuit block and performs a switching operation; a second high voltage system circuit block which does not perform the switching operation; a low pass filter which demodulates the amplification modulation signal and generates a driving signal; and a piezoelectric element which is displaced as the driving signal is applied, in which the second high voltage system circuit block is disposed between the low voltage system circuit block and the first high voltage system circuit block.