JP4021894B2 - Thermal printer device - Google Patents

Description

  The present invention relates to a thermal printer apparatus that performs printing using a thermal head.

  For example, there are various types of thermal printer apparatuses that are receipt printers used in POS systems and the like. In Japan, thermal printers are built into the POS main unit (hereinafter referred to as built-in type thermal printers), but when used overseas, the POS main unit becomes a BOX type like a PC. The thermal printer device that is separated from the POS main body (hereinafter referred to as a distributed type thermal printer device) is the mainstream. Such various types of thermal printer apparatuses have been developed exclusively for built-in types or dedicated for distributed types. The built-in type thermal printer apparatus has been developed on the assumption that the power supply is stably supplied by a dedicated power supply.

  On the thermal head, a logic IC called a driver IC that is driven at 5V or 3.3V is mounted. In order to prevent destruction of the thermal head, it is desirable to turn on the drive power of the logic IC before the drive power of the thermal head. For this reason, the thermal printer apparatus has a mechanism for switching the driving power source (usually about 24 V) of the thermal head in accordance with an instruction from the control circuit. For example, the drive power for the thermal head can be turned on / off by a semiconductor switch, and the drive power for the thermal head is turned on after the logic IC drive power is turned on.

There is known a technique for obtaining a pulse width of a control pulse based on the applied voltage value when the applied voltage value during printing of the thermal head is equal to or less than a threshold value (see, for example, Patent Document 1).
JP 2000-326539 A

As described above, there are built-in types and distributed types of thermal printer apparatuses, but a thermal printer apparatus that can be used for either type is desired.
However, if a distributed thermal printer is used for an embedded thermal printer, an inrush current prevention circuit, which was not necessary for the dedicated power supply for the built-in thermal head, is added to the thermal printer to protect the external power supply. It is necessary to provide it. In this case, a voltage drop due to passing through the inrush current prevention circuit is assumed. In the built-in type thermal printer device, the harness used for power supply is as short as about 20 to 30 cm, so that the power supply is stably supplied with relatively little voltage drop. Since the cable used for supply is as long as about 2 to 3 m, the voltage drop amount becomes large. Thus, there are various factors causing voltage drops in the power supply path from the power supply to the thermal head. Therefore, when the built-in type and the distributed type are realized by the same thermal printer device, the voltage applied to the thermal head depending on whether the power is supplied from the POS main unit or the AC adapter. There is a problem in that there is a difference in printing density unevenness.

  As a 24V power source of the thermal head used in the distributed type thermal printer apparatus, various types are assumed, for example, when connected to the POS main body as well as the AC adapter. However, even the POS main body and the AC adapter connected in this way have variations in input voltage, and the extent of this cannot be determined. For this reason, there may be a case where a difference occurs in the voltage applied to the thermal head due to different input voltages.

  Moreover, in what is described in Patent Document 1, the applied voltage of the thermal head is detected during printing, and energization control is performed based on the detected value. However, when an input voltage different from the specification is supplied. Can not respond.

  The present invention has been made in view of the above problems, and its object is to deal with various power supply input forms and to a thermal head in consideration of a voltage drop generated in a voltage path according to the various power supplies. It is an object of the present invention to provide a thermal printer apparatus that can perform energization control.

The thermal printer apparatus of the present invention is connected to the first power source used in the built-in type thermal printer apparatus incorporated in the apparatus main body, and is used in the separation type thermal printer apparatus separated from the apparatus main body. can be connected to a second power supply, there is provided with a thermal head operated by a voltage supplied through the inrush current preventing circuit from the voltage or the second power supplied from the first power supply, said first A semiconductor switch for turning on and off the supply of voltage from one power source or the inrush current prevention circuit to the thermal head, and voltage detection means for detecting a voltage output from the semiconductor switch when the semiconductor switch is turned on; When the first dedicated power source or the second dedicated power source is turned on, the semiconductor switch is turned on to detect the voltage. Caught detected voltage of the unit, and corrects the pulse width of the head control pulses required for the printing operation of the thermal head so as to constantly maintain the value thereof detected voltage value is predetermined, then the initial turning off the semiconductor switch A control unit for processing, and a control unit for normal processing for turning on the semiconductor switch and supplying the corrected head control pulse to the thermal head for printing after completion of the initial processing. Yes.

  According to the present invention, it is possible to provide a thermal printer apparatus that can cope with various power supply input forms and can control energization to the thermal head in consideration of voltage drop that occurs in voltage paths corresponding to the various power supplies. .

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram schematically illustrating a main part of a control configuration of the thermal printer apparatus 1. The thermal printer device 1 has a thermal head 11. The thermal head 11 is, for example, a line thermal head provided with a plurality of heating resistors. Further, the thermal printer device 1 can be connected to both the 24V dedicated power source 2 used in the conventional built-in type and the 24V power source used in the conventional distributed type. Power is supplied from either the 24 V dedicated power source 2 or the 24 V power source 3.

  When the 24V dedicated power supply 2 is connected to the thermal printer apparatus 1, the voltage supplied from the 24V dedicated power supply 2 is supplied to a FET (Field Effect Transistor) switch 12 which is a semiconductor switch. On the other hand, when the 24V power supply 3 is connected to the thermal printer device 1, the voltage supplied from the 24V power supply 3 is supplied to the FET switch 12 via the inrush current prevention circuit 13.

  The FET switch 12 is provided to apply a 24V drive voltage for printing to the thermal head 11 after applying a voltage of a logic IC provided on the thermal head 11 in order to protect the thermal head 11. Yes. ON / OFF of the FET switch 12 is controlled by the CPU 15. The voltage output from the FET switch 12 is supplied to the thermal head 11.

  The voltage detection circuit 14 detects the voltage value after being output from the FET switch 12 and before being supplied to the thermal head 11. The voltage detection circuit 14 transmits voltage value information indicating the detected voltage value to the CPU 15.

The CPU 15 is a control circuit. When the thermal printer apparatus 1 performs a printing operation, the CPU 15 transmits print data to the thermal head 11 by a head control pulse, and turns on the FET switch 12 only at the printing timing. Further, the CPU 15 performs a process of correcting the energization time, which is the pulse width of the head control pulse, based on the voltage value information received from the voltage detection circuit 14 when performing the initial process when the power is turned on. Yes. This correction is performed using the formula T2 = (24 / VD) ² × T1 (1)
Based on. Here, T2 is a post-correction energization time, T1 is a predetermined pre-correction energization time, and VD is a voltage value indicated by voltage value information detected by the voltage detection circuit.

  Next, a flow of processing executed by the CPU 15 in the initial processing when the thermal printer 1 is turned on will be described with reference to FIG.

  First, after detecting the power ON of the thermal printer 1 (ST1), the CPU 15 transmits 0 data as a head control pulse to the thermal head 11 (ST2) and turns on the FET switch 12 (ST3).

  In this state, the CPU 15 receives voltage value information indicating the voltage value VD output from the FET switch 12 detected by the voltage detection circuit 14 (ST4). Subsequently, the CPU 15 corrects the energization time of the head control pulse transmitted to the thermal head 11 using the above-described equation (1) (ST5). Thereby, when the voltage value VD received from the voltage detection circuit 14 is deviated from 24V, the energization time before correction is set so that the energy applied to the thermal head 11 is constant with respect to the error of 24V. The corrected energization time T2 is corrected from T1.

  Then, the CPU 15 turns off the FET switch 12 (ST6). When such initial processing is completed, normal processing for printing that has been conventionally performed is started.

Hereinafter, an operation of the thermal printer apparatus 1 configured as described above will be described.
First, the case where power is supplied from the 24V dedicated power source 2 to the thermal printer 1 will be described. When the power of the thermal printer 1 is turned on, power is supplied to the FET switch 12 via a harness of 20 cm to 30 cm. Then, after 0 data is transmitted to the thermal head 11 and printing is not performed, the FET switch 12 is turned on and a voltage is supplied to the thermal head 11. The voltage detection circuit 14 detects the voltage value VD after being output from the FET switch 12 and before being supplied to the thermal head 11. When the voltage value VD detected by the voltage detection circuit 14 deviates from the voltage value of 24V supplied to the thermal head 11, the energization width of the head control pulse is set to be constant at 24V with respect to the error. The pre-correction energization time T1 is corrected to the post-correction energization time T2. Then, the FET switch 12 is turned OFF, and normal processing for printing is started. In this way, since the energization width (energization time) of the head control pulse can be corrected, even if a voltage drop due to voltage passing through the harness or the FET switch 12 occurs, a constant voltage of 24 V is applied to the thermal head 11. And the occurrence of uneven printing density can be prevented.

  Next, the case where power is supplied from the 24V power source 3 to the thermal printer apparatus 1 will be described. When the power of the thermal printer 1 is turned on, the power is supplied to the FET switch 12 via the cable of 2 to 3 m and the inrush current prevention circuit 13. Then, after 0 data is transmitted to the thermal head 11 and printing is not performed, the FET switch 12 is turned on and a voltage is supplied to the thermal head 11. The voltage detection circuit 14 detects the voltage value VD after being output from the FET switch 12 and before being supplied to the thermal head 11. If the voltage value VD detected by the voltage detection circuit 14 deviates from the voltage value of 24V supplied to the thermal head 11, the energization width of the head control pulse is set to be constant at 24V with respect to the error. The pre-correction energization time T1 is corrected to the post-correction energization time T2. Then, the FET switch 12 is turned OFF, and normal processing for printing is started. In this way, since the energization width (energization time) of the head control pulse can be corrected, the thermal head 11 can be used even if a voltage drop occurs due to the cable, the inrush current prevention circuit 13, and the FET switch 12. In addition, a constant voltage can be supplied at 24V, and the occurrence of uneven print density can be prevented.

  As described above, according to the thermal printer apparatus 1 of this embodiment, the power source to be used is the 24V dedicated power source 2 when connected to the POS main body or the like, or the case where it is connected to the AC adapter or the like. If it is not determined which of the 24V power sources 3 is connected, it is possible to supply a constant voltage of 24V to the thermal head 11 regardless of which power source is connected, and to prevent the occurrence of uneven print density. Can do.

  Further, according to the thermal printer apparatus 1, the voltage detection circuit 14 determines the voltage value output from the FET switch 12 and before being supplied to the thermal head 11 before performing normal processing for printing. Based on the detected voltage value, the energization width of the head control pulse is corrected from the pre-correction energization time T1 to the post-correction energization time T2 so that the error is constant at 24V. Therefore, the thermal printer apparatus 1 can supply power through a relatively short harness such as 20 to 30 cm and the FET switch 12 as in the case of the 24 V power source 2 as in the case of 2 to 3 m as in the case of the 24 V power source 3. Even when the power is supplied via the long cable, the inrush current prevention circuit 13 and the FET switch 12, it is possible to correct the energization width of the head control pulse in consideration of the voltage drop generated in the voltage path.

  In particular, when using a 24V power supply 3 such as an AC adapter, the range of error in the specification of the 24V power supply varies depending on the manufacturer, etc., but even when such errors differ, the error is taken into account. Can be corrected.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage.

The figure which shows schematically the principal part of the control structure of the thermal printer apparatus in embodiment of this invention. The figure which shows the flow of the process in the same embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Thermal printer apparatus, 2 ... 24V exclusive power supply, 3 ... 24V power supply, 11 ... Thermal head, 12 ... FET switch, 13 ... Inrush electric current prevention circuit, 14 ... Voltage detection circuit, 15 ... CPU

Claims (1)

Connection to the first power source used in the built-in type thermal printer device incorporated in the device main body and connection to the second power source used in the separation type thermal printer device separated from the device main body are possible. In a thermal printer apparatus comprising a thermal head that operates by a voltage supplied from the first power supply or a voltage supplied from the second power supply via an inrush current prevention circuit ,
A semiconductor switch for turning on and off the supply of voltage from the first power source or the inrush current prevention circuit to the thermal head;
Voltage detecting means for detecting a voltage output from the semiconductor switch when the semiconductor switch is on;
When the first power source or the second power source is turned on, the semiconductor switch is turned on to capture the detection voltage value of the voltage detection means, and the thermal head is set to a predetermined value. Correcting the pulse width of the head control pulse required for the printing operation, and then controlling means for initial processing for turning off the semiconductor switch;
Normal processing control means for turning on the semiconductor switch for printing after completion of the initial processing and supplying the corrected head control pulse to the thermal head;
A thermal printer apparatus comprising:

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