JPH0336051A - Thermal head - Google Patents

Abstract

PURPOSE:To detect burning of a thermal head automatically by a method wherein a resistor is inserted in parallel to a drive transistor of the thermal head, and a voltage value to be generated in the resistor is read. CONSTITUTION:In the case of no burning in an heating element 2, when voltage is impressed to be the heating element 2, a current flows through the heating element 2 and a resistor 4, and a voltage value devided by each resistance value is outputted as output from the resistor 4. This voltage value is taken as high electric potential. When a drive transistor 3 is turned on, current hardly flows through the resistor 4, and output of the resistor becomes a value akin to ground voltage. This is taken as low electric potential. Then, in the case of burning in the heating element 2, output of the resistor 4 is at low electric potential as it is irrespective of being on or off of the drive transistor 3. Therefore, when voltage is impressed to the heating element 2 under a state in which the drive transistor 3 is off, high electric potential or low electric potential is outputted as output of the resistor 4 depending upon whether burning of the heating element 2 is present or not. A processor 5 reads output voltage of the resistor 4, and detects the presence of burning of the heating element 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal printer, and particularly to a burnout detection circuit for a thermal head.

[Conventional technology]

Conventionally, in this type of printer device, the presence or absence of burnout of the heating element of the thermal head is not detected, but is confirmed by visually checking the print result.

[Problem to be solved by the invention]

For this reason, there is a drawback that burnout of the thermal head cannot be detected without operator intervention.

[Means to solve the problem]

The present invention provides a device capable of detecting burnout of a thermal head by inserting a resistor in parallel with the drive transistor of the thermal head and reading the voltage value generated by the resistor.

[Effect]

The presence or absence of burnout of the thermal head is detected by determining whether the voltage generated in the resistor is a high potential or a low potential.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

In FIG. 1 showing an embodiment of the present invention, the thermal head burnout circuit of the present invention includes a thermal head 1 comprising a heating element 2, a drive transistor 3 for driving the generator, and a resistor 4 inserted in parallel with the drive transistor 3. and a processor 5 that controls the thermal head.

When the heating element 2 is not burnt out, current flows through the heating element 2 and the resistor 4 when a voltage is applied to the heating element 2. At this time, a voltage value divided by each resistance value is outputted from the resistor 4. This voltage value is defined as a high potential. When the drive transistor 3 is turned on, current flows through the drive transistor 3, and almost no current flows through the resistor 4, so that the output of the resistor 4 has a value close to the ground voltage.

This is considered a low potential.

Next, if the heating element 2 is burnt out, no current will flow even if a voltage is applied to the heating element 2, and the output of the resistor 4 will remain at a low potential regardless of whether the drive transistor 3 is on or off.

Therefore, if a voltage is applied to the heating element 2 with the drive transistor 3 turned off, the output of the resistor 4 will be
A high potential or a low potential is output depending on the presence or absence of burnout.

By reading the output voltage, the processor 5 can detect whether or not the heating element 2 is burnt out.

〔Effect of the invention〕

In the present invention, as described above, by additionally inserting a resistor, thermal head burnout can be automatically detected, and there is an effect of preventing erroneous printing due to thermal head burnout.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Thermal head, 2... Heating element, 3... Drive transistor, 4... Resistor, 5... Processor.

Claims (1)

[Claims] A thermal head characterized by arranging a resistor in parallel with a head drive transistor within the thermal head.