Inkjet Printhead Driver Circuit with Segmented Inductors
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Solution Overview
Problem
High-speed, high-volume piezo electric printheads face energy wastage and cooling issues due to significant power dissipation in rapidly charging and discharging capacitance, leading to reduced resolution and increased printing time, and non-uniformity in ink ejection.
Innovation Solution
A drive circuit with separate switching elements and inductors for charge and discharge phases, allowing precise control and energy recovery, which enables higher pulse repetition rates and stable operation by avoiding resistive losses and parasitic capacitance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single inductor is used in the drive circuit for energy recovery, then energy can be recycled between inductor and capacitor, but unwanted ringing occurs and pulse repetition rate is adversely affected
Solution Approach 1:
The single inductor is segmented into two separate inductors: a first inductor for the charge path and a second inductor for the discharge path. This segmentation allows independent optimization of charge and discharge operations, eliminating the ringing and pulse repetition rate issues caused by using a single shared inductor.
2Loss of energy
If inductance is added to the drive circuit for energy recovery, then energy can be recycled, but uniformity of print is reduced due to voltage fluctuations
Solution Approach 1:
The drive circuit is segmented into separate charge and discharge paths with dedicated inductors and switching elements. This segmentation isolates the energy recovery function from the voltage control function, allowing stable voltage delivery to the printhead while still achieving energy recovery, thereby maintaining print uniformity.
Solution Approach 2:
The first and second switching elements act as intermediaries that control the flow of current through the respective inductors. These switching elements precisely regulate the charging and discharging processes, preventing voltage fluctuations that would otherwise cause print uniformity issues while enabling energy recovery.
3Productivity
If rapid charging and discharging is achieved to increase printing speed, then productivity improves, but significant power is dissipated leading to cooling problems
Solution Approach 1:
Instead of dissipating the energy stored in the capacitor when discharging the printhead, the circuit recovers this energy using the second inductor and second switching element. The recovered energy is returned to the power supply, enabling rapid charging and discharging cycles for high-speed printing while minimizing power dissipation and eliminating cooling requirements.
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 achieves high pulse repetition rates, reduces energy wastage, and maintains printing stability and uniformity by allowing precise control over charge and discharge phases, even with varying capacitance, thus enhancing the efficiency and performance of piezo electric printheads.
Implementation Method 1
a first switching element connected to couple a drive connection of the printhead to a first connection of a power supply via a first inductor to provide a charge path for current to charge the capacitance
Implementation Method 2
a second switching element connected to couple a drive connection of the printhead to a second connection of the power supply via a second inductor to provide a discharge path for current to discharge the capacitance
Implementation Method 3
Printheads for ink jet printers are typically piezo electric. Piezo electric elements have capacitance and energy is typically dissipated in rapidly charging and discharging the capacitance to a desired voltage
Data Source
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AI summary
A drive circuit for repetitively energising a printhead (10) to eject drops of ink and a method of operating the drive circuit are described. The printhead has multiple nozzle channels each having a respective capacitance. The drive circuit includes a first switching element (S1) connected to couple a drive connection of the printhead to a first connection of a power supply (V1) via a first inductor (L1) to provide a charge path for current to charge the capacitance of at least one nozzle channel to a desired operating voltage. The drive circuit further includes a second switching element (S2) connected to couple a drive connection of the printhead to a second connection of the power supply (V1)via a second inductor (L2) to provide a discharge path for current to discharge the capacitance of said at least one nozzle channel to a desired inter-pulse voltage.