초록 ▼

A thermal printer with a fault detection circuit for detecting faults in heating elements of the printer includes a print head containing heating elements and a heating circuit for each heating element and a power supply for supplying power to the heating elements. Power is supplied to the print hea

A thermal printer with a fault detection circuit for detecting faults in heating elements of the printer includes a print head containing heating elements and a heating circuit for each heating element and a power supply for supplying power to the heating elements. Power is supplied to the print head either directly through one terminal of the power supply or indirectly, during a test mode, through a fault detection circuit which is also connected to the print head. The fault detection circuit includes a constant voltage source, preferably formed of series-connected diodes, through which power flows to the print head. Current passing through the constant voltage source activates a photocoupler having an output the voltage of which determines whether a current is or is not flowing into the print head. A CPU which controls overall operations in the printer monitors the photocoupler and selects either a normal printing mode or a print head test mode. In the test mode, the CPU enables sequentially each of the heating circuits to determine their functional integrity.

대표청구항 ▼

A fault detection circuit for a thermal printer, comprising: a print head having heating circuits therein; a testing circuit coupled to the print head for testing its heating circuits; a power supply for supplying electrical power to the print head and a control means for supplying the electrical po

A fault detection circuit for a thermal printer, comprising: a print head having heating circuits therein; a testing circuit coupled to the print head for testing its heating circuits; a power supply for supplying electrical power to the print head and a control means for supplying the electrical power to the print head either directly or indirectly through the testing circuit; and the testing circuit comprising a constant voltage source including a plurality of diodes connected in series with one another for producing a constant voltage across the diodes when current flows through the diodes to the print head, the constant voltage source being connected in series between the power supply and the print head, and the testing circuit further including a photocoupler and said photocoupler including a light emitting diode which is coupled in parallel to and driven by the constant voltage of the constant voltage source, the photocoupler being effective for indicating whether or not current flows from the constant voltage source to the print head.