Capacitive Load Driving Circuit Ground Segmentation for Noise Reduction
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Solution Overview
Problem
In liquid discharging apparatuses like ink jet printers, high oscillation frequencies in class-D amplifiers lead to noise interference, affecting discharge accuracy and waveform quality, while traditional component layouts fail to adequately mitigate noise.
Innovation Solution
A configuration where the gate driver and boosting circuit are connected to a common ground terminal, with reduced wiring impedance between the ground terminal and the gate driver, minimizing noise influence and allowing precise voltage control of piezoelectric elements, and using a charge pump circuit as the boosting circuit to suppress noise generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high oscillation frequency (1 MHz to 8 MHz) is used in class-D amplifier, then discharge accuracy and waveform quality are improved, but noise interference increases
Solution Approach 1:
The patent segments the ground connection paths for different circuit blocks (gate driver, boosting circuit, transistor) by providing separate ground terminals for each block. This segmentation isolates noise sources and prevents noise coupling between high-frequency switching circuits and sensitive control circuits, thereby reducing noise interference while maintaining high oscillation frequency operation.
Solution Approach 2:
The patent introduces ground terminals as intermediary connection points between different circuit blocks and the common ground. These ground terminals act as mediators that provide controlled impedance paths for noise currents, preventing noise from coupling into sensitive signal paths while allowing high-frequency operation to proceed.
2Loss of energy
If class-D amplifier is used instead of class-AB amplifier, then power efficiency is improved, but discharge accuracy deteriorates due to noise
Solution Approach 1:
By segmenting the ground connections and providing separate ground terminals for the gate driver and boosting circuit, the patent isolates the noise generated by the class-D amplifier's high-frequency switching from the piezoelectric element control signals. This allows the class-D amplifier to maintain its power efficiency while the segmented ground structure prevents noise from degrading discharge accuracy.
Solution Approach 2:
The patent applies different ground connection qualities to different circuit blocks: low-impedance ground connections for high-current switching circuits (transistor, boosting circuit) and controlled-impedance ground connections for sensitive control circuits (gate driver). This local differentiation of ground quality allows noise tolerance in power circuits while protecting sensitive circuits from noise, enabling accurate discharge control with class-D amplification.
3Device complexity
If common ground terminal is used for gate driver and boosting circuit, then circuit complexity is reduced, but noise coupling increases
Solution Approach 1:
The patent segments the common ground connection into multiple separate ground terminals (first ground terminal for gate driver, second ground terminal for boosting circuit, third ground terminal for transistor). While the terminals are ultimately connected to a common ground potential, the segmentation provides separate current paths that prevent noise coupling between circuits, maintaining low complexity while reducing noise interference.
Solution Approach 2:
The patent resolves the noise coupling problem by adding a spatial dimension to the ground connection architecture. Instead of a single-point ground connection, the patent distributes ground terminals across different locations in the circuit layout, creating separate ground paths that diverge and converge in space. This dimensional approach allows common ground potential while preventing noise coupling through separate current return paths.
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 discharge accuracy and waveform quality by reducing noise interference and improving voltage control, achieving high-frequency operation without deteriorating power efficiency or generating excessive heat.
Implementation Method 1
a piezoelectric element which is displaced as the driving signal is applied
Implementation Method 2
a charge pump circuit as the boosting circuit
Data Source
AI summary
There is provided a driving circuit for a capacitive load including: a modulation portion which generates a modulation signal pulse-modulated from a source signal; a gate driver which generates an amplification control signal based on the modulation signal; a boosting circuit which boosts and supplies a voltage to the gate driver; a transistor which generates an amplification modulation signal amplified from the modulation signal based on the amplification control signal; a low pass filter which demodulates the amplification modulation signal and generates a driving signal; and in which a wiring impedance between the ground terminal and the gate driver is smaller than a wiring impedance between the ground terminal and the boosting circuit.