JP2005119244A - Heat transfer printer and power circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power circuit for a heat transfer printer which is designed so that the unusual overheating state thereof does not continue. <P>SOLUTION: In a heat transfer printer, a power block comprises a rectifier circuit 3b which rectifies a source power supply, a DC-DC converter 3c which converts the output dc voltage to a predetermined dc voltage VH, a control circuit 11 which controls operation and non-operation of the converter 3c, a latch circuit 18 which brings the converter 3c to a non-operation state, and an output terminal 3e which supplies the output dc voltage VH of the converter 3c to a head block 2. The power block further comprises an integration circuit 12 which integrates a print control signal 10 from a control circuit block 1, wherein when the output signal of the integration circuit 12 becomes a predetermined voltage, a latch signal 13a is supplied to the latch circuit 18 and the print control signal 10 is made zero level for every predetermined period t1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermal transfer printer and a power supply circuit suitable for use in a thermal transfer printer.

  In general, thermal transfer printers are widespread. In this thermal transfer printer, a heat-melting or sublimating material applied to the ribbon is applied to the head element of the head block by passing a current corresponding to the gradation (the density of the image from white to black) to the head element. The heat sensitive material applied to the medium is colored by the heat of the head element.

FIG. 4 is a schematic diagram of a conventional thermal transfer printer. The thermal transfer printer includes a control circuit block 1, a head block 2, and a power supply block 3.
The control circuit block 1 includes a central control unit (CPU) 1a composed of a microcomputer, and forms a print signal of a pulse width modulation signal of the number of dots on a line, for example, 2048 from image data.

  The npn transistors 2a for driving the number of dots on the line of the image data formed by the control circuit block 1, for example, the number of dots on the line provided with the print signal of 2048 pulse width modulation signals in the head block 2, respectively. Supplied to the base of 2a,.

  The emitters of the transistors 2a, 2a,... With the number of dots are grounded, and the collectors of the transistors 2a, 2a,. Are connected to the power supply terminal 2c.

  Further, a thermistor 2d for detecting the temperature of the head block 2 is provided at a predetermined position of the head block 2, and temperature information detected by the thermistor 2d is supplied to the CPU 1a of the control circuit block 1 via the harness connection 4.

  In the power supply block 3, reference numeral 3a denotes a power plug to which, for example, a commercial power of 100 V and 50 Hz is supplied. 3h is a smoothing capacitor. The output DC voltage of the rectifier circuit 3b is supplied to a DC-DC converter 3c that converts the DC voltage VH to 33V, for example.

  A DC voltage VH of, for example, 33V obtained on the output side of the DC-DC converter 3c is supplied to the output terminal 3e via a connection switch 3d whose on / off is controlled by a print control signal from the CPU 1a of the control circuit block 1. . A DC voltage VH of, for example, 33V obtained at the output terminal 3e is supplied to the power supply terminal 2c of the head block 2 via the harness connection 4. Reference numeral 3f denotes a print control signal input terminal from the control circuit block 1.

  Further, the output signal of the DC-DC converter 3c is supplied to the DC-DC converter 3g, and, for example, 5V and 12V DC power sources are obtained from the output DC voltage of the DC-DC converter 3g.

  In the power supply block 3, reference numeral 3i denotes a protection latch circuit. The latch circuit 3i is a protection signal for various protection circuits such as an overvoltage protection circuit, an overcurrent protection circuit, and an overheat protection circuit of the power supply block 3. When the latch signal is supplied to the latch signal input terminal 3j, the DC-DC converter 3c is deactivated and this inoperative state is latched.

  To release the latched state of the latch circuit 3i, it is necessary to turn off the commercial power supply (unplug the power plug 3a) and discharge the smoothing capacitor 3h.

  In the conventional thermal transfer printer as shown in FIG. 4, the CPU 1 a of the control circuit block 1 generates a print control signal having a length corresponding to the number of prints of the image data, and outputs this print control signal to the print control signal input terminal 3 f of the power supply block 3. To supply.

  As shown in FIG. 5A, the print control signal is a high level “1” signal for n × t1 time when, for example, n sheets are printed when the head energization time required for one print is t1.

  When the high level “1” of the print control signal is supplied to the print control signal input terminal 3f, the connection switch 3d is turned on during that time, and the DC-DC converter 3c is connected to the power supply terminal 2c of the head block 2 as shown in FIG. 5B. For example, a direct current voltage VH of 33V is supplied on the output side.

  At the same time, the CPU 1a of the control circuit block 1 supplies the print signal of the pulse width modulation signal to the bases of the transistors 2a, 2a,... That drive the head elements 2b, 2b,. , 2b,..., Generate heat by applying current to print.

  In the example of FIG. 4, when the head block 2 generates heat abnormally, the thermistor 2 d detects this abnormal heat generation and notifies the CPU 1 a of the control circuit block 1 via the harness connection 4.

When this abnormal heat is generated, the CPU 1a of the control circuit block 1 sets the print control signal to low level “0”, turns off the connection switch 3d, and stops the supply of the DC voltage VH to the power supply terminal 2c of the head block 2. I was doing it. A similar protection configuration is also disclosed in Patent Document 1.
Japanese Patent No. 2960792

  However, the CPU 1a software runaway in the control circuit block 1, the poor connection of the thermistor 2d (so-called top plastic etc.), the disconnection of the harness connection 4 part, the poor connection (so-called top plastic etc.), the driving transistor 2a of the head element 2b. An abnormality occurs for some reason, such as when a defect occurs, and n sheets are printed even if the high-level “1” period of the print control signal indicates n sheets printing (or preheating) as shown in FIG. 6A. When the operation has continued, the DC voltage VH output from the DC-DC converter 3c continues to be supplied as shown in FIG. 6B, and the abnormal overheating state may continue.

  In view of this point, an object of the present invention is to prevent an abnormal overheating state from continuing.

  The thermal transfer printer of the present invention includes a power supply block, a control circuit block, and a head block. In the thermal transfer printer in which the control circuit block and the head block are harness-connected, the power supply block is rectified with a commercial power supply. A rectifier circuit, a DC-DC converter that converts an output DC voltage of the rectifier circuit into a predetermined DC voltage, and a control circuit that controls the operation and non-operation of the DC-DC converter by a print control signal from the control circuit block; A power supply having a latch circuit that causes the DC-DC converter to be in an inoperative state by a latch signal from various protection circuits, and an output terminal that supplies an output DC voltage of the DC-DC converter to the head block In the block, the product that integrates this print control signal from this control circuit block. Provided circuit, the output signal of the integrating circuit is obtained so as to the printing control signal at predetermined intervals zero level supplies a latch signal to the latch circuit when it is a predetermined voltage.

  According to the thermal transfer printer of the present invention, since the integration circuit for integrating the print control signal is provided and the print control signal is set to the zero level for every predetermined print, for example, one sheet, the integration circuit is normally used. It is discharged every printing of a predetermined period, for example, one sheet, and the output signal of the integration circuit does not exceed a predetermined voltage. However, at the time of abnormality, the zero level portion of the printing control signal disappears, and the output signal of the integration circuit is At this time, since the DC-DC converter is inactivated by the latch circuit, the output DC voltage VH cannot be obtained, and the abnormal heating state of the head block is eliminated.

  The power supply circuit of the present invention includes a rectifier circuit for rectifying a commercial power supply, a DC-DC converter for converting an output DC voltage of the rectifier circuit into a predetermined DC voltage, and a control signal from a control signal input terminal. A control circuit for controlling operation and non-operation, a latch circuit for causing the DC-DC converter to be in an inoperative state by a latch signal from various protection circuits, and an output DC voltage of the DC-DC converter as a load In a power supply circuit having a supply output terminal, an integration circuit for integrating the control signal is provided at the control signal input terminal, and a latch signal is supplied to the latch circuit when the output signal of the integration circuit reaches a predetermined voltage. In addition, the control signal is set to a zero level every predetermined period.

  According to such a power supply circuit of the present invention, since the integration circuit for integrating the control signal is provided at the control signal input terminal and the control signal is set to the zero level at every predetermined period, the integration circuit is normally set to the predetermined level. It is discharged every cycle, and the output signal of this integration circuit does not exceed the predetermined voltage, but when there is an abnormality, the zero level part of this control signal disappears and the output signal of this integration circuit becomes the predetermined voltage. Since the DC-DC converter is deactivated by the latch circuit, the abnormal heating state does not continue.

  According to the present invention, abnormal overheating continues even when a CPU software runaway in the control circuit block, thermistor connection failure, harness connection disconnection, connection failure, head element drive transistor failure, etc. occur. There is nothing.

  Examples of the best mode for carrying out the thermal transfer printer and the power supply circuit of the present invention will be described below with reference to FIGS. 1, parts corresponding to those in FIG. 4 are denoted by the same reference numerals.

FIG. 1 is a schematic diagram of a thermal transfer printer according to this example. This thermal transfer printer includes a control circuit block 1, a head block 2, and a power supply block 3.
The control circuit block 1 includes a central control unit (CPU) 1a composed of a microcomputer, and forms a print signal of a pulse width modulation signal having the number of dots on a line, for example, 2048 from image data to be printed.

  The npn transistors 2a and 2a for driving the number of dots on the line of the image data formed by the control circuit block 1, for example, the number of dots on the line provided in the head block 2 with 2048 pulse width modulation signals. ,... Are supplied to the base via the harness connection 4.

  The emitters of the transistors 2a, 2a,... With this number of dots are grounded, and the collectors of the transistors 2a, 2a,. Connect to the power supply terminal 2c through.

  Further, a thermistor 2d for detecting the temperature of the head block 2 is provided at a predetermined position of the head block 2, and temperature information detected by the thermistor 2d is supplied to the CPU 1a of the control circuit block 1 via the harness connection 4.

  In the power supply block 3, reference numeral 3a denotes a power plug to which, for example, a commercial power of 100 V and 50 Hz is supplied. The output side of the rectifier circuit 3b is grounded via a smoothing capacitor 3h.

  The output DC voltage of the rectifier circuit 3b is supplied to a DC-DC converter 3c that converts the DC voltage VH to 33V, for example. A DC voltage VH of, for example, 33V obtained on the output side of the DC-DC converter 3c is supplied to the output terminal 3e. A DC voltage VH of, for example, 33V obtained at the output terminal 3e is supplied to the power supply terminal 2c of the head block 2 via the harness connection 4.

  In the power supply block 3, reference numeral 3 f denotes a print control signal input terminal to which a print control signal 10 from the CPU 1 a of the control circuit block 1 is supplied. In this example, as shown in FIG. 2A, the print control signal 10 supplied to the print control signal input terminal 3f is provided with a zero level period 10a having a width of, for example, several μsec every time one print is completed.

  In this example, the print control signal 10 supplied to the print control signal input terminal 3f is supplied to the on / off control circuit 11. The on / off control circuit 11 activates the DC-DC converter 3c when the print control signal 10 is at a high level "1", and this DC-DC converter when the print control signal 10 is at a low level "0". 3c is set to an inoperative state.

  In this case, since the response speed of the DC-DC converter 3c is not fast during the zero level period of several μSec between the high level “1” of the print control signal 10, it does not become inoperative.

  In this example, the printing control signal input terminal 3f is connected to one input terminal of the comparison circuit 13 via the resistor 12a constituting the integration circuit 12, and the resistor 12a and one of the comparison circuit 13 are connected. The midpoint of connection with the input terminal is grounded via a capacitor 12b constituting the integrating circuit 12.

  When the time constant of the integrating circuit 12 composed of the resistor 12a and the capacitor 12b is set to a predetermined value and the printing control signal 10 required for one printing is integrated, the output voltage 12c of the integrating circuit 12 is as shown in FIG. 2B. Set to Va.

  In this example, a discharging diode 14 for speeding up discharging of the capacitor 12b is connected in parallel with the resistor 12a of the integrating circuit 12.

  Further, as shown in FIG. 2B, the power supply terminal 15 is grounded via a variable resistor 16 that obtains a predetermined reference voltage Vb higher than the voltage Va, and a predetermined reference voltage Vb obtained at the movable element 16a of the variable resistor 16 is supplied. , And supplied to the other input terminal of the comparison circuit 13.

  As shown in FIG. 3, the comparison circuit 13 obtains a latch signal 13a when the output voltage 12c of the integration circuit 12 exceeds the predetermined reference voltage Vb, and this latch signal 13a is supplied to the latch circuit 18 via the resistor 17. The signal is supplied to the latch signal input terminal 18a.

  The latch circuit 18 is in a latch state when the latch signal 13a is supplied to the latch signal input terminal 18a. At this time, the on / off control circuit 11 is controlled, and the on / off control circuit 11 controls the DC-DC converter 3c. Make it inoperative.

  Reference numeral 19 denotes various protection circuits such as an overvoltage protection circuit, an overcurrent protection circuit, and an overheat protection circuit for the power supply block 3. When the various protection circuits 19 require protection, a latch signal 13a is generated as a protection signal. Then, the latch signal 13a is supplied to the latch signal input terminal 18a so that the latch circuit 18 is brought into the latch state.

  Further, the midpoint of connection between the rectifier circuit 3b and the DC-DC converter 3c is grounded via a series circuit of resistors 21 and 22, and the voltage obtained at the connection point of the resistors 21 and 22 is used as the power source of the latch circuit 18. Supply.

  In this case, even if the DC-DC converter 3c becomes inoperative, the latch circuit 18 continues to operate since power is supplied.

  In order to release the latch state of the latch circuit 18, the commercial power supply is turned off (the power plug 3a is removed), and the charge of the smoothing capacitor 3h is discharged.

  Further, the output signal of the DC-DC converter 3c is supplied to the DC-DC converter 3g, and a DC power source of, for example, 5V and 12V is used as a power source for other circuits such as the control circuit block 1 from the output DC voltage of the DC-DC converter 3g. To get.

  The rest of the thermal transfer printer according to this example is configured in the same manner as before.

  Since the thermal transfer printer according to this example is configured as described above, when instructing the number of prints of image data, for example, instructing to print four sheets, the CPU 1a of the control circuit block 1 displays the image data as shown in FIG. 2A. A print control signal 10 having a zero level portion 10a of several μSec is generated between a high level “1” signal of a number corresponding to the number of prints, for example, four times t1 and the high level “1” signal, The print control signal 10 as shown in FIG. 2A is supplied to the print control signal input terminal 3 f of the power supply block 3.

  When the high level “1” signal of the print control signal 10 from the print control signal input terminal 3f is supplied to the on / off control circuit 11, the on / off control circuit 11 sets the high level of the print control signal. The period in which the “1” signal is present, for example, the period in which the high-level “1” signal is present for four times t1, and the DC-DC converter 3c is in the operating state. During this time, for example, a DC voltage VH of 33 V is obtained as shown in 2D, and this DC voltage VH is supplied to the power supply terminal 2c of the head block 2.

  At the same time, the CPU 1a of the control circuit block 1 supplies the print signal of the pulse width modulation signal to the bases of the transistors 2a, 2a,... That drive the resistors 2b, 2b,. .., And generate heat by applying current to the resistors 2b, 2b,.

  In the example of FIG. 1, when the head block 2 generates heat abnormally, the thermistor 2 d detects this abnormal heat generation and notifies the CPU 1 a of the control circuit block 1 of this through the harness connection 4.

  When the thermistor 2d detects abnormal heat generation in the head block 2 and notifies this to the CPU 1a of the control circuit block 1, the CPU 1a of the control circuit block 1 sets the print control signal 10 to the low level “0”. This low level “0” print control signal 10 is supplied to the on / off control circuit 11, which turns off the DC-DC converter 3 c and supplies it to the output side of the DC-DC converter 3 c. The DC voltage VH is not obtained, and the supply of the DC voltage VH to the power supply terminal 2c of the head block 2 is stopped.

  In this example, the print control signal 10 supplied to the print control signal input terminal 3f is supplied to the integration circuit 12.

  In this case, during normal operation, the output signal 12c of the integration circuit 12 is accumulated in the capacitor 12b in the printing period t1 of the printing control signal 10 as shown in FIG. 2B, and then in the capacitor 12b in the zero level portion 10a. The accumulated charge is discharged to the low impedance print control signal input terminal 3f side. At this time, since the discharging diode 14 is connected in parallel to the resistor 12a, this discharging is performed quickly.

  During this normal operation, the output signal 12c of the integration circuit 12 rises to the voltage Va as shown in FIG. 2B, but does not become the predetermined voltage Vb, so that no latch signal appears on the output side of the comparison circuit 13 as shown in FIG. 2C. Absent.

  Further, in this example, the CPU 1a software runaway in the control circuit block 1, the thermistor 2d connection failure (so-called top plate etc.), the harness connection 4 disconnection, the connection failure (so-called top plate etc.), the resistance of the head element. When an abnormality occurs for some reason, such as when a driving transistor 2a of the devices 2b, 2b,... Is defective, the print control signal 10 generated by the CPU 1a is high time “1” as shown in FIG. The zero level portion 10a is removed every t1, and the DC-DC converter 3c continues to operate under the control of the on / off control circuit 11, and continues to output the DC voltage VH to the output side as shown in FIG. 3D.

  However, at this time, as shown in FIG. 3A, the zero level portion 10a of the print control signal 10 is eliminated, so that the output signal 12c of the integrating circuit 12 continues to rise as shown in FIG. 3B and reaches a predetermined voltage Vb determined in advance. At this time, a latch signal 13a is obtained on the output side of the comparison circuit 13 as shown in FIG. 3C.

  At this time, the latch signal 13a is supplied to the latch signal input terminal 18a of the latch circuit 18, and the latch circuit 18 causes the on / off control circuit 11 to become inoperative and the DC-DC converter 3c is inactivated. Set to latched state.

  At this time, since the DC-DC converter 3c is inoperative, the DC voltage VH cannot be obtained on the output side of the DC-DC converter 3c as shown in FIG. 3D, and the DC voltage VH is applied to the power supply terminal 2c of the head block 2. Therefore, an abnormal overheating state does not continue and no DC voltage is present on the output side of the DC-DC converter 3g. Therefore, for example, 5V and 12V DC power supplies as power supplies for other circuits such as the control circuit block 1 are also available. The print control signal 10 disappears as shown in FIG. 3A.

  As described above, according to the present example, the CPU 1a software runaway in the control circuit block 1, the thermistor 2d connection failure, the harness connection 4 disconnection, the connection failure, the resistors 2b, 2b,. When a failure of the driving transistors 2a, 2a,... Occurs, the abnormal overheating state does not continue.

  Of course, the present invention is not limited to the above-described examples, and various other configurations can be adopted without departing from the gist of the present invention.

It is a block diagram which shows the example of the best form for implementing this invention thermal transfer printer. It is a diagram with which it uses for description of this invention. It is a diagram with which it uses for description of this invention. It is a block diagram which shows the example of the conventional thermal transfer printer. It is a diagram with which it uses for conventional description. It is a diagram with which it uses for conventional description.

Explanation of symbols

  1 ... Control circuit block, 1a ... CPU, 2 ... Head block, 2a ... Transistor, 2b ... Resistor, 2c ... Power supply terminal, 2d ... Thermistor, 3 ... Power supply block, 3a ... Power supply Plug, 3b ... Rectifier circuit, 3c, 3g ... DC-DC converter, 3e ... Output terminal, 3f ... Print control signal input terminal, 3h ... Capacitor, 10 ... Print control signal, 10a ... Zero level 11, ON / OFF control circuit, 12, integrating circuit, 12 a, resistor, 12 b, capacitor, 13, comparison circuit, 13 a, latch signal, 14, diode, 16, variable resistance 18 latch circuit

Claims (5)

A rectifying circuit for rectifying a commercial power supply; a DC-DC converter for converting an output DC voltage of the rectifying circuit into a predetermined DC voltage;
A control circuit for controlling operation and non-operation of the DC-DC converter according to a control signal from a control signal input terminal;
A latch circuit in which the DC-DC converter is inactivated by the latch signal from various protection circuits;
In a power supply circuit having an output terminal for supplying an output DC voltage of the DC-DC converter to a load,
An integration circuit for integrating the control signal is provided at the control signal input terminal so that the latch signal is supplied to the latch circuit when the output signal of the integration circuit reaches a predetermined voltage, and the control signal is supplied at a predetermined cycle. A power supply circuit characterized by having a zero level every time. The power supply circuit according to claim 1,
A power supply circuit, wherein the integrating circuit comprises a resistor and a capacitor, and a discharging diode is provided in parallel with the resistor. In a thermal transfer printer that includes a power supply block, a control circuit block, and a head block, and the control circuit block and the head block are connected to each other by a harness.
A rectifier circuit for rectifying the commercial power supply with the power supply block;
A DC-DC converter that converts the output DC voltage of the rectifier circuit into a predetermined DC voltage;
A control circuit for controlling the operation and non-operation of the DC-DC converter by a print control signal from the control circuit block;
A latch circuit in which the DC-DC converter is inactivated by the latch signal from various protection circuits;
In a power supply block having an output terminal for supplying an output DC voltage of the DC-DC converter to the head block,
An integration circuit for integrating the print control signal from the control circuit block is provided, and when the output signal of the integration circuit reaches a predetermined voltage, a latch signal is supplied to the latch circuit and the print control signal is supplied at predetermined intervals. A thermal transfer printer characterized by having a zero level. The thermal transfer printer according to claim 3.
The thermal transfer printer according to claim 1, wherein the print control signal is set to zero level for each print. The thermal transfer printer according to claim 3 or 4,
A thermal transfer printer, wherein the integrating circuit is composed of a resistor and a capacitor, and a discharging diode is provided in parallel with the resistor.

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