JP2001038943A - Thermal head disconnection self-diagnosis circuit and disconnection self-diagnosis method - Google Patents

Abstract

(57) [Summary] To diagnose a disconnection or non-disconnection of a resistor (heating element) quickly. A current interrupting circuit (Q1) 6 is provided between an input terminal line 16 and one end of a capacitor 3 to diagnose a disconnection of a resistor (heating element) 1 when a capacitor ON / OF is diagnosed.
A current interrupting circuit (Q1) 6 by a signal from the F terminal 10
Is turned off, and the input terminal line 16 and the capacitor 3 are insulated from each other, so that the influence of the capacitor 3 is avoided. When diagnosing disconnection of the resistor (heating element) 1, the current interrupting circuit (Q 2) 12 connected to both ends of the capacitor 3 is connected to the capacitor ON / OFF terminal 14.
From the capacitor 3 to drop the discharge current from the capacitor 3 to the ground side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head disconnection self-diagnosis circuit and a disconnection self-diagnosis method suitable for disconnection diagnosis of a current supply path to a resistance (heating element) of a thermal head.

[0002]

2. Description of the Related Art When printing, a thermal head turns on / off power to a heating element in accordance with dots to be printed.
Thereby, printing is performed by coloring of thermal paper or transfer of a thermal transfer ribbon.

FIG. 2 shows a schematic circuit configuration of a thermal head.

[0004] As shown in FIG.
It includes a resistor (heating element) 1, a NAND gate 2, and a capacitor 3 as a “head body”. Resistance (heating element) 1
Are provided in accordance with the print dots. The NAND gates 2 are provided corresponding to the respective resistors (heating elements) 1. The capacitor 3 compensates for an undervoltage at the time of a voltage drop.

In such a configuration, a current is applied to the resistor (heating element) 1 via the NAND gate 2 in accordance with the dot to be printed. At this time, if the number of dots to be printed increases and a large amount of current is required temporarily, a voltage drop may occur. In this case, the voltage drop is compensated for by the undervoltage by the charging voltage of the capacitor 3.

When diagnosing disconnection of a thermal head having such a configuration, for example, as shown in FIG.
A configuration in which the check terminal 5 is connected to the detection resistor 4 is employed. The resistance of the detection resistor 4 is set higher than that of the resistance (heating element) 1.

The resistors (heating elements) 1 to be diagnosed are energized one by one, and a voltage check is performed via a check terminal 5. In this case, the current supplied to the resistor (heating element) 1 is a constant current.

At this time, if there is no disconnection in the resistance (heating element) 1, most of the current flows through the resistance (heating element) 1, so that the voltage of the check terminal 5 is low. On the other hand, if the resistor (heating element) 1 is disconnected, most of the current flows to the detection resistor 4 side, so that the voltage of the check terminal 5 becomes a high value.

As described above, the resistors (heating elements) 1 to be diagnosed are energized one by one, and the voltage is checked via the check terminal 5, whereby the disconnection of the resistance (heating elements) 1 is diagnosed.

[0010]

However, in the above-described conventional thermal head, as described with reference to FIG. 2, a capacitor 3 is provided to compensate for an insufficient voltage at the time of a voltage drop.

FIG. 4 shows a schematic circuit configuration of the thermal head in this case.

Here, the charging voltage of the capacitor 3 in FIG. 4 gradually decreases to V1 and V2 due to the discharge in FIG.

As described above, a predetermined time is required until the voltage V2 of the check terminal 5 is stabilized by the discharging operation of the capacitor 3, so that it is not possible to quickly diagnose the disconnection or non-disconnection of the resistor (heating element) 1. There is a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and a disconnection self-diagnosis circuit for a thermal head and a disconnection self-diagnosis circuit which can quickly diagnose disconnection or non-disconnection of a resistor (heating element). A method can be provided.

[0015]

According to a first aspect of the present invention, there is provided a thermal head disconnection self-diagnosis circuit comprising a plurality of resistors (heating elements).
An input terminal for supplying a current to the head body, an input terminal line formed from the input terminal toward the head body, and a plurality of resistors provided in accordance with the printing dots and connected in parallel to the input terminal line. (Heating element)
And a capacitor connected in parallel with the resistor (heating element) to the input terminal line to compensate for an undervoltage at the time of voltage drop, and a capacitor connected in parallel to the input terminal line in parallel with the resistor (heating element) and A disconnection self-diagnosis circuit for a thermal head, comprising: a detection resistor having a high resistance value; and a check terminal connected to the detection resistor and performing a voltage check by energizing one resistor (heating element) for disconnection diagnosis one by one. Is connected between the input terminal line and one end of the capacitor, and is turned off when performing a disconnection diagnosis of the resistance (heating element).
A first current interrupting circuit that insulates between an input terminal line and a capacitor, and a first current interrupting circuit that supplies a signal for turning on the first current interrupting circuit during normal printing and turning off the signal during disconnection diagnosis. And a capacitor ON / OFF terminal. In addition, a diode may be connected between the first current interrupting circuit and one end of the capacitor so that the discharge current of the capacitor flows to the input terminal line during printing. A second current interrupting circuit is provided between both ends of the capacitor, which is turned on when performing a disconnection diagnosis of the resistor (heating element) and drops the current due to the discharge of the capacitor to the ground side. Is turned off during normal printing.
The second capacitor ON / OFF terminal for supplying a signal for turning ON at the time of disconnection diagnosis can be connected. In the method of self-diagnosis of disconnection of a thermal head according to the fourth aspect, a plurality of resistors (heating elements) provided in correspondence with dots to be printed temporarily charge a capacitor when a large current is required. When performing a first step of supplementing with a voltage and performing a disconnection diagnosis of a resistor (heating element), an input terminal for supplying a current to the resistor (heating element) is connected to an input terminal line formed toward the resistor (heating element). A second step of supplying a constant current, a third step of energizing one resistor (heating element) to be diagnosed for disconnection, and a detection resistor having a higher resistance value than the resistance (heating element). A fourth step of performing a voltage check via a check terminal, and a first current that is turned off by a signal from a first capacitor ON / OFF terminal between a capacitor and an input terminal line when the voltage check is performed. Interruption Characterized in that it comprises a fifth step of insulating the circuit. Further, the first step includes a sixth step of flowing a discharge current of the capacitor to the input terminal line via a diode connected between the first current interrupting circuit and one end of the capacitor. be able to. In the fifth step,
The seventh step of dropping the current due to the discharge of the capacitor to the ground side by the second current interrupting circuit that is turned on by the signal from the second capacitor ON / OFF terminal can be included. In the thermal head disconnection self-diagnosis circuit and the disconnection self-diagnosis method according to the present invention,
A first current intermittent circuit is provided between the input terminal line and one end of the capacitor to perform a first current intermittent operation by a signal from the first capacitor ON / OFF terminal when diagnosing disconnection of a resistor (heating element). By turning off the circuit and insulating between the input terminal line and the capacitor, the influence of the capacitor is avoided.

[0016]

Embodiments of the present invention will be described below. In the drawings described below, FIGS.
Parts common to those in FIG. 4 are denoted by the same reference numerals.

FIG. 1 is a circuit diagram showing one embodiment of a thermal head disconnection self-diagnosis circuit of the present invention.

As shown in FIG. 1, the thermal head includes a resistor (heating element) 1, a NAND gate 2, a capacitor 3, a detection resistor 4, a check terminal 5, a current interrupting circuit (Q1) 6, a diode 7, and resistors 8, 9. , Capacitor ON / OFF terminal 10, resistor 11, current interrupting circuit (Q2) 12, resistor 13
And capacitor ON / OFF terminal 14, input terminal (DC
+ 24V) 15 and an input terminal line 16.

The current interrupting circuit (Q 1) 6 is provided between the input terminal line 16 and one end of the capacitor 3.
A capacitor ON / OFF terminal 10 is connected to the gate of the current interrupting circuit (Q1) 6 via resistors 8 and 9.

The current interrupting circuit (Q1) 6 serving as a first current interrupting circuit includes a capacitor ON / OFF terminal 10 serving as a first capacitor ON / OFF terminal when diagnosing a disconnection of the resistor (heating element) 1. It is turned off by a signal from. Thereby, when diagnosing the disconnection of the resistor (heating element) 1, the influence of the discharge of the capacitor 3 is avoided.

The diode 7 allows the discharge current of the capacitor 3 to flow to the input terminal line 16 during printing.

A current interrupting circuit (Q 2) 12 as a second current interrupting circuit is connected to both ends of the capacitor 3 via a resistor 11. The second capacitor ON / OFF is connected to the gate of the current interrupting circuit (Q2) 12 via the resistor 13.
A capacitor ON / OFF terminal 14 as a terminal is connected.

The current intermittent circuit (Q2) 12 is used to diagnose the disconnection of the resistor (heating element) 1 when the capacitor ON / OF is detected.
It is turned on by a signal from the F terminal 14. Thus, when the disconnection of the resistor (heating element) 1 is diagnosed, the capacitor 3
Since the current due to the discharge of the electric current is dropped to the ground side, the influence is avoided.

Next, the operation of the disconnection self-diagnosis circuit of the thermal head having such a configuration will be described.

First, during normal printing, the current interrupting circuit (Q1) 6 is turned on. At this time, the current interrupting circuit (Q2) 12 is turned off.

As a result, the current caused by the discharge of the capacitor 3 flows to the input terminal line 16 via the diode 7, so that the number of dots to be printed increases, and even if a large amount of current is needed temporarily, the voltage is not changed. The descent is compensated.

Therefore, stable high-quality printing is performed. Also, a small and inexpensive (low capacity) power supply can be used.

On the other hand, when diagnosing a disconnection of the thermal head, the current intermittent circuit (Q1) 6 is turned off by a signal from the capacitor ON / OFF terminal 10.

The current interrupting circuit (Q2) 12 is turned on by a signal from a capacitor ON / OFF terminal 14.

As a result, since the capacitor 3 is insulated from the input terminal line 16, the input terminal (DC + 24
V) The constant current from 15 does not flow into the capacitor 3 side. Further, the discharge current from the capacitor 3 is dropped to the ground side by turning on the current interrupting circuit (Q2) 12.

Then, the resistors (heating elements) 1 to be diagnosed are turned on one by one, and the voltage is checked via the check terminal 5. In this case, the current supplied to the resistor (heating element) 1 is a constant current as described above.

At this time, if there is no disconnection in the resistance (heating element) 1, most of the current flows through the resistance (heating element) 1, so that the voltage of the check terminal 5 is low. On the other hand, if the resistor (heating element) 1 is disconnected, most of the current flows to the detection resistor 4 side, so that the voltage of the check terminal 5 becomes a high value.

As described above, the resistors (heating elements) 1 to be diagnosed are energized one by one, and the voltage is checked via the check terminal 5, whereby the disconnection of the resistance (heating elements) 1 is diagnosed.

As described above, in the present embodiment, the current interrupting circuit (Q1) 6 is provided between the input terminal line 16 and one end of the capacitor 3 to diagnose the disconnection of the resistor (heating element) 1. Since the current interrupting circuit (Q1) 6 is turned off by a signal from the capacitor ON / OFF terminal 10 and the input terminal line 16 and the capacitor 3 are insulated from each other, the influence of the capacitor 3 is avoided. (Heating element) Diagnosis of disconnection or non-disconnection of 1 can be performed quickly.

As a result, since the capacitor 3 does not affect the diagnosis of the disconnection of the resistor (heating element) 1, it is possible to select the capacity with less restrictions by considering only the printing quality, and thus to select a high quality thermal capacitor. The development of the head becomes easy.

When diagnosing disconnection of the resistor (heating element) 1, the current interrupting circuit (Q 2) 12 connected to both ends of the capacitor 3 is connected to the capacitor ON / OFF terminal 14.
And the discharge current from the capacitor 3 is dropped to the ground side, so that the disconnection can be diagnosed without waiting for the capacitor 3 to be completely discharged.

As a result, even when the number of resistors (heating elements) 1 is large, such as a wide or fine thermal head, the work time for diagnosing a disconnection can be reduced.

[0038]

As described above, according to the thermal head disconnection self-diagnosis circuit and the disconnection self-diagnosis method according to the present invention,
A first current intermittent circuit is provided between the input terminal line and one end of the capacitor to perform a first current intermittent operation by a signal from the first capacitor ON / OFF terminal when diagnosing disconnection of a resistor (heating element). By turning off the circuit and insulating between the input terminal line and the capacitor, the influence of the capacitor is avoided, so that the disconnection or non-disconnection of the resistor (heating element) can be quickly diagnosed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a thermal head disconnection self-diagnosis circuit of the present invention.

FIG. 2 is a diagram showing a schematic circuit configuration of a conventional thermal head.

FIG. 3 is a diagram showing a circuit configuration when diagnosing a disconnection of the thermal head of FIG. 2;

FIG. 4 is a diagram showing a circuit configuration when diagnosing a disconnection of the thermal head of FIG. 2;

FIG. 5 is a waveform chart for explaining a diagnosis of disconnection of the thermal head of FIG. 2;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 resistance (heating element) 2 NAND gate 3 capacitor 4 detection resistor 5 check terminal 6 current interrupting circuit (Q1) 7 diode 8, 9, 11, 13 resistor 10, 14 capacitor ON / OFF terminal 12 current interrupting circuit (Q2) 15 input Terminal (DC + 24V) 16 Input terminal line

Claims (6)

[Claims] 1. An input terminal for supplying a current to a head body having a plurality of resistors (heating elements), an input terminal line formed from the input terminal to the head body, and a plurality of lines corresponding to print dots. A resistor (heating element) connected in parallel with the input terminal line, and a resistance (heating element) connected to the input terminal line in parallel with the resistor (heating element);
A capacitor for compensating for an undervoltage at the time of voltage drop, a detection resistor connected in parallel with the resistor (heating element) to the input terminal line, having a higher resistance value than the resistor (heating element), and being connected to the detection resistor. A self-diagnosis circuit for a disconnection of a thermal head, comprising: a check terminal for conducting a voltage check by energizing the resistors (heating elements) to be disconnected one by one, between the input terminal line and one end of the capacitor. To perform a disconnection diagnosis of the resistor (heating element)
F, the first current interrupting circuit that insulates between the input terminal line and the capacitor, and the first current interrupting circuit are turned on during normal printing, and are turned on during the disconnection diagnosis. And a first capacitor ON / OFF terminal for supplying a signal for turning off the circuit. 2. A diode for flowing a discharge current of the capacitor to the input terminal line at the time of printing is connected between the first current interrupting circuit and one end of the capacitor. A circuit for self-diagnosis of disconnection of a thermal head according to claim 1. 3. A second current interrupting circuit is provided between both ends of the capacitor, which is turned on when performing diagnosis of disconnection of the resistor (heating element) and drops a current due to discharging of the capacitor to the ground side. The second current interrupting circuit is provided with the second current interrupting circuit during normal printing.
3. The circuit for self-diagnosis of disconnection of a thermal head according to claim 1, wherein a second capacitor ON / OFF terminal for supplying a signal for turning on the terminal during the disconnection diagnosis is connected. 4. A first step of compensating for a voltage drop when a large amount of current is temporarily required by a plurality of resistors (heating elements) provided in accordance with dots to be printed by a charging voltage of a capacitor; A second step of supplying a constant current from an input terminal for supplying a current to the resistor (heater) to an input terminal line formed toward the resistor (heater) when performing a disconnection diagnosis of the resistor (heater); A third step of energizing the resistors (heating elements) to be disconnected one by one, and a voltage check via a check terminal connected to a detection resistor having a higher resistance value than the resistors (heating elements). 4th to do
And performing a voltage check to isolate the capacitor and the input terminal line by a first current interrupting circuit that is turned off by a signal from a first capacitor ON / OFF terminal. And a self-diagnosis method for a disconnection of the thermal head. 5. The method according to claim 1, further comprising: flowing a discharge current of the capacitor to the input terminal line via a diode connected between the first current interrupting circuit and one end of the capacitor. 5. The method for self-diagnosis of disconnection of a thermal head according to claim 4, further comprising the step of: 6. A fifth step in which a second current interrupting circuit which is turned on by a signal from a second capacitor ON / OFF terminal drops a current due to discharge of the capacitor to the ground side in the fifth step. 5. The circuit for self-diagnosis of disconnection of a thermal head according to claim 4, wherein: