Liquid Ejector Drive Circuit PWM Sensitivity Adjustment
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Solution Overview
Problem
Existing drive circuits for liquid ejecting devices, such as ink jet printers, face challenges in stably driving piezoelectric actuators as capacitive loads, with issues arising from varying numbers of actuators being driven simultaneously, leading to difficulties in selecting suitable inductance values for PWM drive circuits and resulting in power loss and instability.
Innovation Solution
A drive circuit that includes a load detection circuit to generate load number information, a signal processing circuit to compare and generate a common drive signal based on this information, and a switching circuit to selectively apply the drive signal to actuators, allowing for stable operation regardless of the number of actuators driven, by adjusting the sensitivity of pulse width modulation (PWM) based on the detected load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capacitance value of a stabilizing capacitor is increased to stably drive the actuator, then the driving stability is improved, but power loss becomes large
Solution Approach 1:
The patent applies dynamics by making the PWM sensitivity adjustable based on the number of actuators being driven. The control unit dynamically changes the PWM sensitivity according to the detected load number, optimizing the driving conditions for different scenarios. This resolves the contradiction by allowing the system to achieve stable driving with appropriate capacitor values for each load condition, rather than using a fixed large capacitor value that causes excessive power loss in all cases.
Solution Approach 2:
The patent changes the parameter of PWM sensitivity based on the number of actuators driven. By adjusting the PWM sensitivity parameter according to the load number, the system optimizes the driving waveform for different capacitor values. This allows the system to maintain driving stability while reducing power loss by using appropriate capacitor values matched to the actual load conditions.
2Measurement precision
If PWM sensitivity is increased to improve driving precision, then drive waveform reproducibility is improved, but the system becomes more sensitive to load variations causing instability
Solution Approach 1:
The patent makes PWM sensitivity dynamic by adjusting it according to the number of actuators driven. When fewer actuators are driven, higher PWM sensitivity can be used for precise waveform reproduction. When more actuators are driven, the sensitivity is reduced to maintain stability. This dynamic adjustment resolves the contradiction between precision and stability.
Solution Approach 2:
The control unit changes the PWM sensitivity parameter based on the detected load number. This parameter change allows the system to optimize drive waveform reproducibility for each specific loading condition while maintaining overall driving stability across varying numbers of actuators.
3Device complexity
If a fixed inductance value is used for the PWM drive circuit, then the circuit design is simplified, but it cannot provide suitable performance for both high and low load cases
Solution Approach 1:
The patent applies dynamics by making the PWM sensitivity adjustable based on load conditions. While the inductance value remains fixed, the dynamic adjustment of PWM sensitivity compensates for the fixed inductance limitation, allowing the circuit to adapt to different load conditions without increasing circuit complexity.
Solution Approach 2:
The patent changes the PWM sensitivity parameter according to the number of actuators driven. This parameter change allows a fixed inductance circuit to achieve load-adaptive performance, resolving the contradiction between circuit simplicity and load versatility.
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 solution enables stable and efficient driving of piezoelectric actuators whether a small or large number are active, improving the reproducibility of the drive waveform and reducing power consumption by optimizing PWM sensitivity according to the load size.
Implementation Method 1
The ink is ejected from the nozzle by applying a drive signal to piezoelectric actuators
Data Source
AI summary
A drive circuit for a liquid ejecting device, such as an inkjet print head or the like, includes a load detection circuit to generate load number information corresponding to the number of actuators to be concurrently driven for an intended liquid ejection. A signal processing circuit is configured to compare a common drive waveform to a target common drive waveform, and then generate a common drive signal to drive the actuators based on the load number information and the comparison of the common drive waveform and the target common drive waveform. A switching circuit is configured to selectively apply portions the generated common drive signal to an actuator according to intended output of the liquid ejection device.