Fluid printhead
View Patent ↗A fluid printhead including a plurality of heater elements that are driven to nucleate bubbles in fluid so that the fluid is ejected from the printhead in the form of drops, a plurality of drive elements, each drive element selectively driving a corresponding one of the plurality of heater elements in accordance with a printer controller, and a drop detection system that includes a plurality of drop detection cells, each drop detection cell detecting a change in electrical resistance of a corresponding one of the plurality of heater elements that occurs upon drop formation.
1. A fluid printhead, comprising:
a plurality of heater elements that are driven to nucleate bubbles in fluid so that the fluid is ejected from the printhead in the form of drops;
a plurality of drive elements, each drive element selectively driving a corresponding one of the plurality of heater elements in accordance with a printer controller; and
a drop detection system comprising a plurality of drop detection cells, each drop detection cell detecting a change in electrical resistance of a corresponding one of the plurality of heater elements that occurs upon drop formation.
2. The fluid printhead of claim 1 , wherein each of the plurality of drive elements is a MOSFET drive element comprising a gate, a source and a drain.
3. The fluid printhead of claim 2 , wherein each drop detection cell is electrically connected to the drain of a corresponding drive element.
4. The fluid printhead of claim 3 , wherein each drop detection cell detects a voltage slope change at the drain of the corresponding drive element.
5. The fluid printhead of claim 4 , wherein each drop detection cell comprises a controller configured to remove power from the corresponding heater element after detection of the voltage slope change.
6. The fluid printhead of claim 1 , wherein each drop detection cell comprises a sampling circuit and a slope detect circuit.
7. The fluid printhead of claim 6 , wherein the sampling circuit comprises a switched capacitor circuit.
8. The fluid printhead of claim 6 , wherein the sampling circuit comprises an A/D circuit.
9. A method of controlling operation of a plurality of drive elements of a printhead, each drive element selectively driving a corresponding one of the plurality of heater elements to nucleate bubbles in fluid so that the fluid is ejected from the printhead in the form of drops, comprising:
detecting a change in electrical resistance of a corresponding one of the plurality of heater elements that occurs upon drop formation; and
deactivating the corresponding one of the plurality of heater elements based on the detection.
10. The method of claim 9 , wherein each of the plurality of drive elements is a MOSFET drive element comprising a gate, a source and a drain, and the step of detecting comprises detecting a voltage slope change at the drain of the corresponding drive element.