Fluid printhead
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;
a plurality of drive elements, each drive element comprising a transistor having a gate, a source, and a drain, and each drive element selectively driving a corresponding one of the plurality of heater elements; and
a plurality of drop detection cells coupled to the plurality of drive elements, each drop detection cell detecting a voltage slope change at the drain of a corresponding one of the plurality of drive elements.
2. The fluid printhead of claim 1 , wherein each of the plurality of drive elements is a MOSFET drive element.
3. The fluid printhead of claim 1 , wherein each detection cell comprises a circuit that outputs a control signal deactivating the corresponding one of the plurality of drive elements upon detecting the voltage slope change.
4. The fluid printhead of claim 1 , wherein each detection cell comprises a controller that determines whether the detected voltage slope change matches one or more of a preset value and time.
5. The fluid printhead of claim 1 , wherein each drop detection cell comprises a sampling circuit and a slope detect circuit.
6. The fluid printhead of claim 5 , wherein the sampling circuit comprises a switched capacitor circuit.
7. The fluid printhead of claim 5 , wherein the sampling circuit comprises an A/D circuit.
8. A method of controlling operation of a plurality of drive elements of a printhead, each drive element comprising a transistor having a gate, a source, and a drain and each selectively driving a corresponding one of a plurality of heater elements, the method comprising:
detecting a voltage slope change at the drain of one of the plurality of drive elements; and
deactivating the one drive element based on the detecting.
9. The method of claim 8 , wherein the deactivating comprises outputting a control signal to deactivate the one drive element upon detecting the voltage slope change.