Actuator Drive Circuit Trim Control for Printhead Thermal Efficiency
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Solution Overview
Problem
Existing printhead circuits, particularly in cold switching environments, face challenges in trimming drop velocity and volume on a per-actuator nozzle basis, which affects image quality due to manufacturing variability, crosstalk, and environmental factors, while also requiring reduced power dissipation and silicon area to maintain thermal efficiency.
Innovation Solution
A drive circuit that generates a common drive waveform and uses a switching circuit and timing circuit to trim the drive pulse by controlling the duration of a step in the pulse, allowing for independent adjustment of the step duration and height, and optionally decoupling during flat portions to reduce thermal impact and silicon area usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a common drive waveform is used in cold switching environment, then power dissipation in print head is reduced, but individual actuator trimming capability is lost
Solution Approach 1:
The drive circuit is segmented into common waveform generation (external) and individual actuator control (local trim circuits). Each actuator receives the common drive waveform but can apply independent trim signals to adjust pulse width or voltage level, enabling individual trimming while maintaining the energy efficiency of common waveform generation.
Solution Approach 2:
Local trim circuits are implemented at each actuator or actuator bank to provide individualized waveform modification. These circuits adjust specific parameters (pulse width, voltage level) for each actuator based on its characteristics, while the overall drive waveform remains common to all actuators.
2Manufacturing precision
If individual trim circuits are added to each actuator, then trimming precision is improved, but silicon area and circuit complexity increase
Solution Approach 1:
A single trim circuit design is made universal and can be applied to multiple actuators or actuator banks. The trim circuit performs multiple functions (pulse width modulation, voltage level adjustment) using the same hardware components, reducing the per-actuator silicon area requirement while maintaining trimming precision.
Solution Approach 2:
Trim circuits for multiple actuators are merged into shared resources where possible. For example, a single trim circuit can serve multiple actuators in a bank, or trimming functions are combined with existing actuator control logic, reducing overall silicon area while preserving individual trimming capability.
3Speed
If pulse width modulation is used for trimming, then droplet velocity control is improved, but thermal dissipation in print head increases
Solution Approach 1:
Trimming adjustments are made in advance during manufacturing or initialization by applying test pulses and measuring droplet characteristics. The optimal trim values are stored and applied automatically during normal operation, eliminating the need for continuous active trimming that would generate heat during printing.
Solution Approach 2:
Instead of continuous pulse width modulation during printing, the system uses periodic recalibration or trim updates. The trim circuits are activated only when needed for calibration or compensation, rather than continuously modulating pulse widths during normal print operation, reducing thermal dissipation.
Data Source
AI summary
A drive circuit (100) for driving actuators of a printhead (97) from a common drive waveform has a switching circuit (32) for coupling the common drive waveform to an actuator (1,2), and a timing circuit (10) to control the switching circuit to form a drive pulse from the common drive waveform. The drive pulse is trimmed by controlling a duration (TTRIM) of a step at an intermediate level (VHOLD) in the drive pulse. This can improve the trade-off between available range of trimming and thermal efficiency because the voltage drop across the switching circuit can be reduced, compared to trimming only the height. Decoupling during a flat portion of the common drive waveform can enable the timing of the decoupling to be more relaxed compared to decoupling during a slope. Such relaxing can enable costs, complexity and thermal loading to be reduced.