Regulated current source for thermal printhead
US4434356A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 22, 1982 |
| Grant date | Feb 28, 1984 |
| Priority date | — |
| Expiry date | Dec 22, 2002 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB41J2/35
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
A current-drive circuit (FIG. 1) is provided to drive each of forty electrodes 41. Voltage at the electrodes 41 is monitored on line 49 as a control-input to a voltage-regulator circuit (FIG. 2), to produce the drive voltage Vdr. Vdr minus a current-level reference Vlev is applied as the input of a differential amplifier (transistors 3, 15, 51 and 53), thereby applying Vdr-Vlev on line 27. A constant current through the electrode 41 is produced across register 25. As the lowest voltage at all driven electrodes shifts, the regulator circuit (FIG. 2) shifts Vdr the same amount, employing differentially connected transistors 72 and 74, and Zener 120 to set the level of Vdr. Since most of the active elements operated within narrow limits, the circuit can be extensively miniaturized.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.