JPS6119375A - Detecting circuit for thermal head burn-out - Google Patents

Abstract

PURPOSE:To enable burn-out or a deteriorated condition of the titled device to be judged before printing, by a construction wherein a detecting resistor connected in series with heating elements is provided, and a potential difference generated between both ends of the resistor is detected. CONSTITUTION:The detecting resistor 6 connected in series with the heating elements 1, a potential difference detecting circuit 7, an A/D converter 8 and a microprocessor 9 for totally controlling printing are provided. When detecting burn-out, a printing-controlling circuit 4 cuts off a transformer 3, and a voltage of a power source 5 is impressed on the heating elements 1 through the detecting resistor 6. With an electric current passed to one of the elements 1 by driving a driver 2, a potential difference according to the resistance of the element 1 is generated between both ends of the resistor 6. The potential difference thus detected is converted into a digital quantity by the converter 8, and the quantity is read by the microprocessor 9. The microprocessor 9 compares the read value with preset digital values to judge the current condition to be a normal condition, a deteriorated condition or a burnt-out condition. The judgement is conducted for all of the heating elements, whereby it is possible to detect burn- out in the thermal head. In addition, scatter of resistances of the heating elements can be also detected on the basis of the read values.

Description

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

[Prior art]

Conventionally, this type of printer apparatus has not monitored burnout or deterioration of the head heating element.

[Problem that the invention seeks to solve]

Therefore, there is a drawback that burnout or deterioration of the head heating element is discovered only after missing dots or uneven density occur in the printed results. Therefore, the present invention solves the above-mentioned drawbacks by constantly monitoring the state of burnout and deterioration of the head heating element outside the printing period, and provides an apparatus capable of printing without dot dropout or density unevenness. .

[Failure to solve the problem]

As shown in FIG. 1, the present invention has a thermal head heating element 1.
A detection resistor 6 is connected in series with the detection resistor 6, a potential difference detection circuit 7 detects the potential difference generated across the detection resistor by passing and energizing the head heating element, and an analog value of the detected potential difference is detected. an A/D converter 8 that converts into a digital value;
It has a microprocessor 9 that reads the converted digital value and compares it with a set value to determine whether it is normal, deteriorated, or burnt out.

[Effect]

When the detection resistor 6 inserted in series with the head heating element 1 is energized, a voltage drop occurs in proportion to each resistance value. Of these, the voltage drop that occurs in the detection resistor 6 is detected,
If a certain set voltage drop occurs, the head heating element is considered to be normal. Further, if there is no voltage drop or the voltage is out of the set value, it is assumed that the head heating element is burnt out or deteriorated.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 1, the embodiment of the present invention includes a thermal head heating element 1, a driver 2, a transistor 3, a printing control section 4 that controls these three, and a power source 5 that supplies current to the heating element l. , a detection resistor 6 connected in series to the heating element 1, a potential difference detection circuit 7 that detects the potential difference generated across the resistor, and an A/D converter that converts the detected potential difference into a digital quantity. 8 and a microprocessor 9 that controls the entire printing process.

In the case of normal printing, the printing control circuit 4 is a transistor 3
It operates so that the voltage of the power source 5 is directly applied to the heating element 1. At the same time, when the driver 2 is driven to supply current to the heating element 1 and generate heat, ° printing is performed.

In the case of burnout detection, the printing control circuit 4 cuts off the transistor 3, and the voltage of the power source 5 is applied to the heating element 1 through the detection resistor 6. Here, when the driver 2 is driven to cause a current to flow through the heating element 1, a potential difference is generated between both ends of the detection resistor 6 according to the resistance value of the heating element 1.

If the voltage of the power supply 5 is ■5, the resistance value of the detection resistor 6 is &, the resistance value of the heating element 1 is R□, and the voltage drop inside the driver 2 is ignored, then the voltage across the detection resistor 6 is The potential difference V6 at is R1. Therefore, the potential difference v6 across the detection resistor 6
By detecting , the state of the heating element 1 can be detected. The detected potential difference is converted into a digital quantity by a converter 8 and read by a microprocessor 9. The microprocessor 9 determines normality, deterioration, and burnout based on the read values.

By applying the above method to all head heating elements, it becomes possible to detect thermal head burnout.

Further, it is also possible to detect variations in the resistance value of the heating element using the values read in the same manner.

〔Effect of the invention〕

As described above, the present invention has the effect of preventing missing dots or printing with uneven density because the state of burnout or deterioration of the head can be determined before printing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a circuit configuration according to an embodiment of the present invention. 1... Heating element 2... Driver 3...
Transistor 4・Print control circuit 5...Power supply
6...Detection resistor 7...Potential difference detection circuit 8...A/D converter 9...Microprocessor 4'.

Claims (1)

[Claims] (1) A current detection resistor inserted in series with the thermal head heating element in a thermal printer device, a potential difference detection circuit that detects the potential difference generated at both ends of the resistor when energized, and an analog amount of the detected potential difference. A thermal head burnout detection circuit comprising: an A/D converter for converting into a digital quantity; and a microprocessor for determining the quality of a head heating element based on the read value.