JP2013014071A - Printing device, method of controlling the same, and program - Google Patents

Abstract

An abnormal power supply to a thermal head is quickly detected and the power supply to the thermal head is stopped.
In a printing apparatus using a thermal head in which a plurality of heating resistors are arranged, thermal power is supplied during printing on a recording medium by supplying power to the heating resistors in accordance with an input data signal. A pause period in which power supply to the head should be paused is provided at a predetermined cycle, and a current supplied to the thermal head is detected by the current detection unit, and the detected current includes a predetermined period including at least one pause period. Over the current threshold value, the power supply to the thermal head is stopped.
[Selection] Figure 1

Description

  The present invention relates to a printing apparatus using a thermal head, a control method therefor, and a program.

  A printer using a thermal head performs a printing operation by supplying electric power to a heating resistor existing in the head and transferring a recording agent as an image onto a recording medium using thermal energy generated thereby. In the thermal head, a plurality of heating resistors are arranged in one row at every minute interval. A predetermined number of heating resistors arranged in one row are configured as one channel. For example, the total number of heating resistors included in the thermal head is 1280, 128 is one channel, and 10 channels are configured. In addition, circuits for driving the heating resistors are configured as driver ICs by the number of channels, and data signals to the driver ICs also exist in the number of channels.

  For example, Patent Document 1 discloses the structure of a thermal head as described above. As shown in Patent Document 1, wiring terminals (generally, FFC) for supplying power and signals to the thermal head and connecting terminals on the thermal head connected by solder are also generally at a minute interval. Is. In a printer using such a thermal head, if there is a defect in the heating resistor or its surroundings, the thermal energy generated by the heating resistor becomes higher than expected, and the printing agent or recording medium is deformed and printed. May seriously affect the image.

  With this background, various methods have been proposed for detecting anomalies around the thermal head (see, for example, Patent Document 2). In Patent Document 2, a low resistance is provided in series with a plurality of heating resistors existing in the thermal head, a current flowing through the heating resistor is detected from a voltage generated at the low resistance, and an abnormality of the heating resistor is detected based on the detection result. Is disclosed.

JP 2006-62146 A JP 2000-326535 A

  In the above-described conventional technology, since a low resistance is inserted in series with the heating resistor, the consumption current varies depending on the number of driven elements among the plurality of heating resistors, and is applied to the heating resistor itself. Voltage varies. Therefore, there has been a problem that unevenness occurs due to a change in printing density due to a change in current consumption.

  In addition, since a defect in the heating resistor itself is detected, an abnormality occurs in the control signal to the thermal head, and heat is generated even when power is supplied to the heating resistor that is not intended by the controlling side. Since the resistor was normal, no abnormality could be detected. For example, in the configuration where the data line and the power supply line are adjacent to each other at the connection part of the thermal head and the FFC, the data line and the power supply line to a specific channel are short-circuited due to foreign matter, water droplets, etc. This is a case where power is supplied to the body. When such a state occurs irregularly, that is, suddenly during printing, and the state continues, there is a problem that the recording agent or the recording medium is seriously damaged. In addition, such an abnormality may occur at various timings and is difficult to detect.

  The present invention has been made in view of such a problem, and an object thereof is to quickly detect an abnormal power supply to a thermal head and to stop the power supply to the thermal head.

  A printing apparatus according to the present invention includes a thermal head in which a plurality of heating resistors are arranged, supplies power to the heating resistors in accordance with an input data signal and prints on a recording medium, and power to the thermal head A power supply unit that supplies power; a control unit that controls power supply to the thermal head by the power supply unit; and a current detection unit that detects a current supplied to the thermal head. A pause period during which power supply to the thermal head should be paused is provided for each predetermined cycle, and the control means includes a predetermined period in which the current detected by the current detection means includes at least one pause period. If the current threshold value is larger than the current threshold, the power supply to the thermal head by the power supply means is stopped.

  According to the present invention, it is possible to quickly detect an abnormal power supply to the thermal head, stop the power supply to the thermal head, and prevent damage to the recording medium or the like.

1 is a diagram illustrating a configuration example of a printing apparatus according to a first embodiment. FIG. 2 is a diagram illustrating a circuit configuration example of a functional unit related to abnormality detection of the printing apparatus illustrated in FIG. It is a figure which shows the structural example of the thermal head in 1st Embodiment. 3 is a timing chart illustrating an example of an input signal to the thermal head in the first embodiment. It is a figure which shows the example of the operation waveform at the time of the normal printing in 1st Embodiment. It is a figure which shows the example of the operation | movement waveform at the time of the abnormal condition in 1st Embodiment. It is a figure for demonstrating the time of the highest density printing in 1st Embodiment. It is a figure for demonstrating the time of abnormality generation in 1st Embodiment. 10 is a flowchart illustrating an example of a control operation of the printing apparatus according to the second embodiment.

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

(First embodiment)
A first embodiment of the present invention will be described.
FIG. 1 is a block diagram illustrating a configuration example of a printing apparatus (thermal printer) according to the first embodiment. FIG. 1 illustrates a configuration relating to power supply to a thermal head and detection of abnormality thereof in a printing apparatus (thermal printer), and other configurations are omitted.

  In FIG. 1, 10 is a current detection unit, 20 is a DC / DC converter, 30 is a thermal head, 40 is a comparison circuit, 50 is a reference circuit, 60 is a timer circuit, and 70 is an ASIC (Application Specific Integrated Circuit).

  The current detection unit 10 converts the consumed current (current flowing through the power supply path to the thermal head 30) into a voltage and outputs the voltage. The voltage converted from the consumed current and output from the current detection unit 10 is hereinafter also referred to as “conversion voltage”. The DC / DC converter 20 receives a power supply voltage (24 V in this example) supplied through a current detection unit 10 from a voltage source (not shown), converts it to a voltage suitable for the thermal head 30 (for example, 18 V), and outputs it. . The DC / DC converter 20 is controlled by a drive signal from the ASIC 70. For example, the DC / DC converter 20 is turned on when a recording medium (not shown) such as recording paper is in contact with the thermal head 30, and is otherwise turned off.

  The thermal head 30 has a plurality of heating resistors (heating elements) arranged in a line at minute intervals. The thermal head 30 receives the voltage output from the DC / DC converter 20 as a drive source for the internal heating resistor, and supplies the power to the heating resistor (energizes the heating resistor) to record the recording agent. Transfer to media as image. The thermal head 30 receives a data signal line by line from the ASIC 70 and controls on / off of the heating resistor in accordance with the received data signal (controls power supply / cutoff to the heating resistor).

  The comparison circuit 40 receives the conversion voltage output from the current detection unit 10 and the reference voltage output from the reference circuit 50. The comparison circuit 40 compares the input conversion voltage with a reference voltage and outputs the comparison result to the timer circuit 60. When the comparison circuit 40 determines that the conversion voltage is greater than the reference voltage, the comparison circuit 40 outputs the output signal to the timer circuit 60 at a low level (“L”) indicating an enable state. On the other hand, when the comparison circuit 40 determines that the converted voltage is smaller than the reference voltage, the comparison circuit 40 outputs the output signal to the timer circuit 60 at a high level (“H”) indicating a disabled state. The reference circuit 50 generates and outputs a reference voltage used for comparison with the converted voltage in the comparison circuit 40.

  The timer circuit 60 performs a timer operation when the signal output from the comparison circuit 40 is at a low level, and resets the timer operation when the signal is at a high level. When the state in which the output signal from the comparison circuit 40 is at a low level is continued for a predetermined time (for example, 10 ms), the timer circuit 60 sets the output signal to a high level indicating an abnormal state and outputs it to the ASIC 70. The ASIC (control circuit) 70 includes a microprocessor and other logic units. The ASIC 70 controls each function of the printing apparatus (thermal printer) according to an operation program stored therein. For example, when the ASIC 70 receives a high level output signal indicating an abnormal state from the timer circuit 60 during printing by the thermal head 30, the ASIC 70 determines that an abnormality has occurred and stops the DC / DC converter 20 and the thermal head 30.

  FIG. 2 is a circuit diagram illustrating a circuit configuration example of the current detection unit 10, the comparison circuit 40, the reference circuit 50, and the timer circuit 60 illustrated in FIG.

  The current detection unit 10 includes a detection resistor R11, an operational amplifier 12, and resistors R12, R13, R14, R15, and R16. The detection resistor R11 is connected in series to a power supply line that supplies a power supply voltage to the DC / DC converter 20 from a voltage source (not shown). The operational amplifier 12 receives a potential corresponding to one end and the other end of the detection resistor R11, amplifies the potential difference, and outputs it. The current detection unit 10 functions as a differential amplifier circuit that amplifies the voltage across the detection resistor R11 by 25 times.

  The reference circuit 50 includes a shunt regulator 51 and resistors R51, R52, and R53. The reference circuit 50 generates and outputs a reference voltage corresponding to a predetermined threshold current (current threshold). In this example, the reference voltage is 1.25V.

  The comparison circuit 40 includes a comparator 41 and resistors R41 and R42. The reference voltage that is the output of the reference circuit 50 is input to the non-inverting input of the comparator 41 via the resistor R41, and the converted voltage that is the output of the current detection unit 10 is input to the inverting input of the comparator 41 via the resistor R42. . The output of the comparator 41 is output as the output signal of the comparison circuit 40. The comparison circuit 40 outputs a low level signal when the inverting input is large in the comparator 41, that is, when the conversion voltage from the current detection unit 10 is larger than the reference voltage. The comparison circuit 40 outputs a high-level signal when the non-inverting input in the comparator 41 is large, that is, when the conversion voltage from the current detection unit 10 is smaller than the reference voltage.

  The timer circuit 60 includes a transistor 61, a capacitor 62, a comparator 63, a constant voltage source 64, and resistors R61 and R62. The timer circuit 60 operates as a timer by charging and discharging the capacitor 62 when the transistor 61 is turned on / off by an output signal from the comparison circuit 40.

  The operation of the circuit configuration shown in FIG. 2 will be described. Here, it is assumed that the resistance value of the detection resistor R11 is 0.1Ω.

  For example, assuming that the current flowing through the current detection resistor R11 is 0.4 A, the voltage at both ends of the detection resistor R11 is 0.04 V, and a voltage 1 V obtained by converting this voltage value by 25 times is converted into a current detection unit. 10 is output. In this case, the non-inverting input is 1.25 V and the inverting input is 1 V, and the comparison circuit 40 outputs a high level signal to the timer circuit 60. Therefore, the transistor 61 of the timer circuit 60 is turned on (conducted), and the capacitor 62 is not charged, so the timer is reset.

  On the other hand, for example, if the current flowing through the current detection resistor R11 is 0.6A, the voltage across the detection resistor R11 is 0.06V, and the voltage 1.5V obtained by converting this voltage value by 25 times is The converted voltage is output from the current detection unit 10. In this case, the non-inverting input is 1.25 V and the inverting input is 1.5 V, and the comparing circuit 40 outputs a low level signal to the timer circuit 60. Thus, the transistor 61 of the timer circuit 60 is turned off (non-conducting), the capacitor 62 is charged, and the timer operation starts.

  The comparator 63 in the timer circuit 60 has one input connected to the capacitor 62 and the other input connected to the constant voltage source 64. Here, it is assumed that the voltage value of the constant voltage source 64 is 2V. Further, it is assumed that the resistors R61 and R62 are set so that the voltage across the capacitor 62 (voltage between the electrodes) reaches 2V at 10 mS when the transistor 61 is off. When the voltage across the capacitor 62 becomes 2 V or higher, the comparator 63 (timer circuit 60) outputs a high level signal indicating an abnormal state. When the transistor 61 is turned on, the electric charge stored in the capacitor 62 is instantaneously discharged.

To summarize the above,
When the current flowing through the current detection resistor R11 is greater than 0.5A, the timer circuit 60 performs a timer operation, and when 10 ms elapses from the timer operation start of the timer circuit 60, a high level signal indicating an abnormal state is output to the ASIC 70. The
Even when the timer circuit 60 is operating, if the current flowing through the current detection resistor R11 becomes smaller than 0.5 A, the timer operation is reset.

  The time until the timer circuit 60 outputs a high level signal indicating an abnormal state (10 ms in the above example) is adjusted by the time constant determined by the capacitance value and resistance value of the capacitor 62 and resistors R61 and R62. Can be set arbitrarily. However, a time longer than the time obtained by subtracting the pause period (one) from the one-dot printing time, in other words, a length of time including at least one pause period during the printing operation is set. The pause period is a period during which power supply to the thermal head provided at every predetermined cycle (every dot printing time) should be paused during printing by the thermal head. Further, the threshold voltage (voltage threshold) to be compared with the voltage across the capacitor 62 can be arbitrarily set by using a constant voltage source 64 having a desired voltage value. The circuit configuration example illustrated in FIG. 2 is an example, and the internal configurations of the current detection unit 10, the comparison circuit 40, the reference circuit 50, and the timer circuit 60 are not limited thereto.

The above operation will be described in relation to the structure of the thermal head and the actual printing operation.
FIG. 3 is a diagram illustrating a configuration example of the thermal head 30. In FIG. 3, 32 is a heating resistor (heating element) in the thermal head 30, and 31-1 to 31-10 are driver ICs. The heating resistors 32 are arranged in a row in the thermal head 30. Each of the ten driver ICs 31-1 to 31-10 is connected with 128 heating resistors 32. The driver ICs 31-1 to 31-10 are connected to the data signal 33, the latch signal 34, the clock signal 35, the strobe signal 36, and the power supply line 37. The driver ICs 31-1 to 31-10 control on / off of the current flowing through the heating resistor (power supply to the heating resistor 32) according to the data supplied by the data signal 33.

  For example, the driver IC 31-1 is connected to a 1-bit signal DATA1 as a data signal, and the data for 128 connected resistors is connected to the 1-bit data line as shown in FIG. Via the ASIC 70. As shown in FIG. 4, 128-bit serial data corresponding to the 128 heating resistors 32 connected is transmitted from the ASIC 70 to the driver IC 31-1 in synchronization with the clock signal 35, and is latched by the latch signal 34. It is latched by the driver IC 31-1. If the latched data is “0”, no current flows through the heating resistor 32 (no power is supplied), and a white image is obtained. If the latched data is “1”, the heating resistor A current flows through 32 (power is supplied) and a black image is obtained.

  Further, in a printing apparatus (thermal printer) using the thermal head 30, for example, gradation is realized by repeating printing a plurality of times within one line of 300 dpi. That is, in order to realize 256 gradations, the thermal head 30 repeats reception and printing of data at least 256 times in one line. Also, the ASIC 70 transmits white data intended for a pause period in addition to 256 or more pieces of print data in one line during normal printing. Here, as described above, in the abnormal state in which the data signal line DATA1 and the power supply line 37 shown in FIG. 3 are short-circuited, even if the request from the ASIC 70 is white data, the data signal line DATA1 is always high. It becomes a level. Therefore, current continues to flow through all 128 heating resistors 32 connected to the driver IC 31-1, and black data is printed over several lines.

  FIG. 5 is a diagram illustrating an example of an operation waveform during normal printing, and FIG. 6 is a diagram illustrating an example of an operation waveform during an abnormal state. 5 and 6, (a) is a waveform of a current flowing through the current detection resistor R11, (b) is an output signal of the comparison circuit 40, (c) is a charge voltage (voltage between electrodes) of the capacitor 62, (d ) Is an output signal of the timer circuit 60.

  In the normal state shown in FIG. 5 (during normal printing), when the current flowing through the detection resistor R11 exceeds the threshold current (current threshold) 0.5 A as shown in (a), it is shown in (b). Thus, the output signal from the comparison circuit 40 is enabled. Then, the timer circuit 60 starts a timer operation, and the voltage across the capacitor 62 increases as shown in (c). In the normal state, the current flowing through the detection resistor R11 continues to be in a state exceeding 0.5 A and becomes lower than 0.5 A at least during the rest period before a predetermined time (10 ms in the above example) elapses. Therefore, the timer circuit 60 is reset, the voltage across the capacitor 62 becomes 0V, and the output signal of the timer circuit 60 shown in (d) maintains a low level indicating a normal state.

  On the other hand, in the abnormal state shown in FIG. 6, the current flowing through the detection resistor R11 exceeds 0.5 A for a predetermined time (10 ms in the above example). Therefore, as shown in (c), the voltage across the capacitor 62 reaches the threshold voltage (threshold voltage), and as shown in (d), the output signal of the timer circuit 60 changes from a low level to a high level indicating an abnormal state. To change. Then, the ASIC 70 stops the DC / DC converter 20 and the thermal head 30.

  As described above, during normal operation, the current flowing through the detection resistor R11 is controlled to be lower than the predetermined value before the voltage of the capacitor 62 included in the timer circuit 60 reaches the predetermined voltage. This will be described with reference to FIGS.

  FIG. 7 is a diagram for explaining the maximum density printing. 7A shows a dot pattern group when printing is performed at the maximum density, and FIG. 7B shows a waveform of a current flowing through the current detection resistor R11 at that time. In FIG. 7, a combination of the pattern 100 and the pattern 110 is one dot of 300 dpi. In this embodiment, the same number of heating resistors as those driven in the resistor arrangement direction, for example, 1280 dots are printed as one line, and the printing operation is repeated in the printing direction. Even at the highest density printing, the white data pattern 110 corresponding to the pause period is added together with the actual printing pattern 100 within one dot printing time. As a result, a pause period 120 occurs in which the power supply to the thermal head 30 is paused during printing, as in the current waveform shown in FIG.

  Further, the magnitude of the current amount shown in (b) is proportional to the number of dots simultaneously printed in the resistance arrangement direction by the actual printing pattern 100. In this case, since all 1280 dots are printed, the current amount becomes the maximum value, which greatly exceeds the threshold current of 0.5 A. However, as described above, the timer circuit 60 is repeatedly reset due to the pause period 120, and a high-level signal indicating an abnormal state is not output from the timer circuit 60.

  On the other hand, for example, when a foreign substance adheres to the thermal head 30 and an abnormal state in which a specific channel among a plurality of channels is fixed to an on state (black data), a white image with the lowest density is printed. An example of this is shown in FIG. Also in FIG. 8, (a) shows the dot pattern group to be printed, and (b) shows the waveform of the current flowing through the current detection resistor R11 at that time. FIG. 8 shows an example in which the first channel is fixed to the on state. At this time, as shown in FIG. 8, from 1 dot to 128 dots is turned on, and there is no white pattern corresponding to the pause period. Also, since 129 dots to 1280 dots are white images, they are not printed.

  Therefore, the current waveform shown in (b) has a lower amplitude than that at the time of printing the maximum density, but always exceeds the threshold current of 0.5 A. Therefore, as described with reference to FIG. 6, since the threshold current is exceeded and there is no current rest period, the voltage across the capacitor 62 eventually reaches the threshold voltage, indicating a high level indicating an abnormal state. Is output from the timer circuit 60. Upon receiving a high level signal indicating an abnormal state from the timer circuit 60, the ASIC 70 stops the DC / DC converter 20 and the thermal head 30. As a result, abnormal power supply (occurrence of abnormal current) to the thermal head 30 that can occur irregularly can be detected quickly, and power supply to the thermal head 30 can be stopped, resulting in damage to the recording medium or the like. Can be minimized.

  In the above description, abnormal power supply (occurrence of abnormal current) caused by a foreign object has been described as an example. However, the present invention is not limited to this. For example, even in the case of abnormal power supply (occurrence of abnormal current) caused by an abnormality in the heating resistor of the thermal head 30, it can be quickly detected in the same manner and the power supply can be stopped. In the present embodiment, it is possible to detect a current flowing through the thermal head 30 over an unpredictable time, that is, an abnormal power supply, regardless of the cause phenomenon.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.
In the first embodiment described above, when a high level signal indicating an abnormal state is output from the timer circuit 60, the ASIC 70 immediately stops the related function. In the second embodiment described below, the timing at which a high level signal indicating an abnormal state is output from the timer circuit 60 is examined, and the power supply related to the printing operation is controlled. In the second embodiment, if a high-level signal indicating an abnormal state is output just before the end of printing (for example, if the time until the end of printing is shorter than a predetermined time), there is a problem even if printing is continued. It is determined that there is no print, and the printing operation is performed.

  Note that the configuration of the printing apparatus (thermal printer) according to the second embodiment is the same as that of the printing apparatus (thermal printer) according to the first embodiment, and a description thereof will be omitted. The printing apparatus according to the second embodiment is different from the first embodiment in control by the ASIC 70 when a high level signal indicating an abnormal state is output from the timer circuit 60.

  FIG. 9 is a flowchart illustrating an example of a control operation by the ASIC 70 in the printing apparatus according to the second embodiment. The control operation shown in FIG. 9 is realized by the ASIC 70 executing a program stored in the ASIC 70. The flowchart shown in FIG. 9 explains that the print operation is stopped upon receipt of print data transmission from the ASIC 70 to the thermal head 30 and a high level signal indicating an abnormal state.

  When the printing apparatus starts a printing operation in step S1, in step S2, the ASIC 70 sets the number of printing operations (number of printing lines) in the line counter. For example, if the length of the recording medium to be printed is 6 inches and the resolution of the printing apparatus is 300 dpi, 1800 is set in the line counter. Thereafter, the ASIC 70 transmits data for one line to the thermal head 30 in step S3, and decrements the value of the line counter by 1 in step S4.

  Next, in step S5, the ASIC 70 determines whether or not the output signal from the timer circuit 60 is at a high level indicating an abnormal state. As a result of the determination, if the output signal from the timer circuit 60 is at a low level, it is determined that the ASIC 70 is normal, the process returns to step S3, and the processes of steps S3 and S4 described above are repeated.

  As a result of the determination in step S5, if the output signal from the timer circuit 60 is at a high level, the ASIC 70 determines that an abnormal state has occurred, and checks the number of remaining print lines in step S6. As a result, if the number of remaining print lines is five or more, the ASIC 70 determines that it is necessary to immediately stop printing, and proceeds to step S9 to urgently stop the printing operation. On the other hand, if the number of remaining print lines is 5 or less, the ASIC 70 determines that there is no problem even if the print operation is continued as it is, and proceeds to step S7. In step S7, the ASIC 70 checks the value of the line counter, repeats the processing from step S3 until the number of remaining lines becomes zero, and continues the printing operation. If the value of the line counter becomes zero, the step ASIC The print operation is terminated.

  In this manner, similarly to the first embodiment, abnormal power supply (occurrence of abnormal current) to the thermal head 30 that can occur irregularly can be detected quickly, and power supply can be stopped. , Damage to the recording medium or the like can be minimized. Even if an abnormal power supply (occurrence of abnormal current) to the thermal head 30 is detected, the printing operation can be continuously executed if the printing is about to end.

(Other embodiments of the present invention)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

10: current detection unit, 20: DC / DC converter, 30: thermal head, 40: comparison circuit, 50: reference circuit, 60: timer circuit, 70: ASIC

Claims (7)

A thermal head in which a plurality of heating resistors are arranged, supplying power to the heating resistors in accordance with an input data signal and printing on a recording medium;
Power supply means for supplying power to the thermal head;
Control means for controlling power supply to the thermal head by the power supply means;
Current detecting means for detecting a current supplied to the thermal head,
A pause period for stopping power supply to the thermal head during printing by the thermal head is provided at predetermined intervals,
The control means stops the power supply to the thermal head by the power supply means when the current detected by the current detection means is larger than a current threshold over a predetermined period including at least one pause period. A printing apparatus characterized by being caused to perform. Comparison means for comparing the current detected by the current detection means with the current threshold;
As a result of the comparison by the comparison means, a timer operation is performed when the current detected by the current detection means is larger than the current threshold, and a timer operation is performed when the current detected by the current detection means is smaller than the current threshold. 2. A printing apparatus according to claim 1, further comprising timer means for resetting.   3. The printing according to claim 1, wherein when the time until the end of printing by the thermal head is shorter than a predetermined time, the control unit continues power supply to the thermal head until the end of printing. apparatus.   3. The control unit according to claim 1, wherein when the number of lines until the end of printing by the thermal head is less than a predetermined number of lines, the power supply to the thermal head is continued until the end of printing. Printing device.   The printing apparatus according to claim 1, wherein the power supply unit is disposed between the thermal head and the current detection unit. A control method for a printing apparatus, comprising: a thermal head in which a plurality of heating resistors are arranged; and a power supply means for supplying power to the thermal head,
A current detection step of detecting a current supplied to the thermal head;
A printing process in which a pause period in which power supply to the thermal head should be stopped during printing is provided for each predetermined period, and power is supplied to the heating resistor in accordance with an input data signal to perform printing on a recording medium; ,
A control step of stopping power supply to the thermal head by the power supply means when a current larger than a current threshold value is detected in the current detection step over a predetermined period including at least one pause period; A control method for a printing apparatus, comprising: A program for causing a computer to execute a control method of a printing apparatus having a thermal head in which a plurality of heating resistors are arranged and power supply means for supplying power to the thermal head,
A current detection step of detecting a current supplied to the thermal head;
A printing step in which a pause period in which power supply to the thermal head should be stopped during printing is provided every predetermined period, and power is supplied to the heating resistor in accordance with an input data signal to print on a recording medium; ,
A control step of stopping power supply to the thermal head by the power supply means when the current detection step detects a current greater than a current threshold over a predetermined period including at least one pause period; A program that causes a computer to execute.

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