JPH0226762A - Driver circuit of thermal head - Google Patents

Abstract

PURPOSE:To enable uniform printing by disposing resistance elements among each terminal of input terminals on the power supply side of a plurality of heating elements in a thermal head. CONSTITUTION:Heating elements H1R1-H1R4 and resistors R1-R3 form a resistor network, and currents are made to flow through each heating element through a transistor 3-2 brought to an ON state. When R1=R2=R3=...Rn hold and the resistance values H1R1=H1R2=...=H1Rn of each heating element hold and the values of respective resistance value are set at specified values, only a current value I2 in currents I1-I4 flowing through each heating element H1R1-H1R4 exceeds currents I0 at a printing level, and is changed into the picture element of a printing surface, and the current values of currents flowing through other heating elements are reduced gradually with the lengthening of distances from the heating element H1R2. Consequently, only the heating elements H1R1, H1R3 adjacent to the heating element H1R2 actually conducting printing are heated in an extent capable of ensuring the uniformity of printing. Accordingly, equal printing can be attained regardless of the number of printing picture elements, and wasteful power consumption is lowered.

Description

[Detailed Description of the Invention] [Work Required] An object of the present invention is to perform uniform printing and reduce power consumption, regardless of the number of printed pixels, regarding a drive circuit system for a thermal head used in a thermal printer. A resistive element is arranged between each of the input terminals on the power supply side of the plurality of heating elements in the thermal head.

[Industrial application field]

The present invention relates to a driving circuit system for a heating element in a thermal head used in a thermal printer.

[Conventional technology]

A plurality of thermal heads are normally used in the printing section of a thermal printer, and heating elements of Vt corresponding to pixels on the printing surface are provided within the thermal head, and when printing, the heating elements An electric current is applied to generate heat, melting the wax on the film and printing.

FIG. 4 shows a conventional thermal head drive circuit, in which 51 is a serial/parallel conversion register, 52-1
52-m is a thermal head, 531 to 53-n are heating element selection transistors, 54-1 to 54-m are block selection transistors, a is a serial data manual signal line, SD is a serial data signal, A1 to 8 〇 is a wiring connection symbol (lines with the same symbol in the diagram indicate that they are connected to each other), D, ~D,, are /parallel output data of the real/parallel conversion register 51, H, D~H ,D, ,H,D
, ~H,D,,H,,D, ~H,D,, are diodes in the thermal head, H1R1~H,R,,H,R,
~H,R,,H,R.

~H, R,, is the heating element in the thermal head (H+R1
(represented by ). Thermal head 52-
In order to reduce hardware, the drive circuit for the plurality of heat generating elements H1R1 within 1 to 52-m includes heat generating element selection transistors provided for each array order in the thermal head of each heat generating element, as shown in the figure. 53-1 to 53-n, and block selection transistors 54-1 to 54-n for selecting a thermal head.
With the combination of both transistors using 54n,
The desired heating elements are selected, sequentially scanned and driven, and printed.

For ease of understanding, the operation will be explained using an example of driving the heating element H2R. First, in the first step, the required print data is sent to the register 51 from the signal line a as the serial data signal SD. Input and parallel output data D1~
Printing is performed by turning on the transistor 53-1 and then turning on the block selection transistor 54-2.

In this way, the heating element selection transistors 53-1 to 53-5
3-n and the ON/OFF states of the block selection transistors 541 to 54n, a current is applied to a desired heating element and printing is sequentially performed.

By the way, in a thermal printer using the conventional thermal head drive circuit described above, when printing a small number of pixels such as a straight line on the entire printing surface, the heat of adjacent pixels is lower than when printing a large number of pixels. The effect is small and printing blur occurs. In order to prevent this, if we try to increase the power applied to the element to prevent the printing from becoming blurred, in the case of printing with a large number of printing pixels, the amount of molten wax becomes excessive and the overall density becomes low. Printing with gradation becomes difficult.

In order to solve the above-mentioned problems, other conventional thermal RAD drive circuits as shown in FIG. 5 have been published.

The drive circuit of FIG. 5 is different from the drive circuit of FIG. 4 in that resistors 60-1 to 60-n are attached between the emitter and collector of each of the heat generating element selection transistors 53-1 to 53-n. This is what I did. That is, resistors 60-1 to 60-
For example, by using n, the block selection transistor 54-1 is driven, and when the heat generating element (,R,) in the thermal head 521 is printing, the heat generated by that pond in the thermal head 521 is Resistor 60-
Current flows from the power supply through 1 to 60-n (excluding 60n-1). Therefore, the heating elements H, R, .
Since the elements adjacent to the area are also heated, clear printing is possible.

Thus, according to this conventional example, uniform printing is possible regardless of the number of pixels.

[Problem to be solved by the invention]

In the other conventional thermal head drive circuit explained in FIG. In addition, heating current will also flow to all other heating elements, but there is no need to flow current to heating elements that are farther away than the heating element that is to be printed, which wastes power and is unnecessary. (Causes fever).

The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a thermal head drive circuit system that achieves uniform printing regardless of the number of printed pixels and consumes less power. do.

[Means for Solving the Problems] According to the present invention, the above objects are achieved by the means described in the claims.

That is, the present invention provides a thermal head including a plurality of heat generating elements forming pixels on a printing surface, means for holding a print data signal for the thermal head, and a means for holding a print data signal for the thermal head, and a means for storing a predetermined heat generating element according to output data of the holding means. In a thermal head drive circuit system comprising means for selecting a heating element and means for applying a voltage to a heating element selected by the selection means, the input terminal on the power supply side of a plurality of heating elements in the thermal head is This is a thermal head drive circuit system characterized in that a resistance element is disposed between each terminal.

[For production]

A thermal head used in a thermal printer has several m heating elements inside, and each heating element is heated and driven to form a pixel on a printing surface.

When printing using the heat generating element described above, data to be printed is first sent to the printer, and the printer holds the print data in, for example, a register or the like.

The plurality of heating elements in the thermal head are connected to a heating element selection means composed of an ON10 F F switch such as a transistor, and are heated for printing according to the output data of the F register, etc. The desired heating element is selected.

A voltage from the power supply is applied to the selected heating element via the 0N10FF switch.

In addition, a resistor is connected between the input terminals on the power supply side of the plurality of heating elements in the thermal head, and when a voltage is applied to one heating element, the other heating elements also have the above-mentioned terminals. Current flows through the resistor connected between
A large current flows through heating elements adjacent to the selected heating element within a range that does not cause printing, and the current becomes smaller as the distance from the selected heating element increases.

Therefore, adjacent heating elements of the selected heating element are sufficiently heated to help achieve uniform printing.

Further, the current of a heating element that is far away from the selected heating element becomes smaller, resulting in less wasted power consumption.

Embodiment] FIG. 1 shows a thermal head drive circuit according to an embodiment of the present invention. 1: Real/parallel conversion register, 21 to 2-
m is a thermal head (represented by code 2-1), 3-
1 to 3-n are heating element selection transistors (symbol 3-1
), 41 to 4-m are block selection transistors (represented by 4-i), and 5-1 to 5-n are base terminals of heating element selection transistors 3-1 to 3-n. input resistor to the base terminal of 6-1 to 6-m Haflon 2 selection transistors 4-1 to 4-m, the alphabet a is a serial data input signal line, SD is a serial data signal, A1 to An are wiring connection symbols (on the diagram,
Lines with the same symbol indicate that they are connected to each other), D1
~Dn is parallel output data of serial/parallel conversion register 1, H, D, ~HDn, H2DI ~Hz Dn
, HmDI-HmDn are diodes in the thermal head (represented by symbol HID1), H,R, ~H,Rn
, H*Rl ~H2Rn, HmRt ~HmRn
represents a heating element in the thermal head (represented by the symbol Hi Di), and R, -R, represent resistors connected between the respective collector terminals of the heating element selection transistors 3-1 to 3-n. te゛、）ru.

There are multiple thermal heads 2-1 inside the thermal printer.
~2-m are provided, and each thermal head 2-1~
A plurality of dies τ-dodes HD1 and heat generating elements HiRi are provided in A.

The diode HiDi regulates the direction of current flowing between each heating element to prevent interference.

Serial/parallel conversion register l is serial code SD
is received from the human input signal line a and converted into parallel output data D1 to Dn.

Parallel output data D, -Dn are base resistances 5-1 to 5-n
are connected to the base terminals of the heat generating element selection transistors 3-1 to 3-n through the transistors 3-1 to 3-n.
n's ON10 F F motion is ill? Wholesale. The collector terminals of the transistors 3-1 to 3-n are connected to heating elements in the thermal head in the order in which they are arranged.

That is, the collector terminal of the transistor 3-1 is connected to the X-th heating element H, R, , H2R, .
...HmR, (the diodes H+ Dr, R2Dr...HmD+ are actually inserted between them as shown in the diagram), and the following transistors 93-2~
The collector terminals 3-n are also connected to the corresponding heating elements. The other output terminal of the heating element HiRi is commonly connected to each thermal head, and is connected to the collector terminals of the corresponding block selection transistors 4-1 to 4-m.

Block selection signals 81 to Bm are connected to resistors 6-1 to 6-m.
are connected to the transistors 4-1 to 4-m, respectively, and a thermal head to be driven is selected.

This embodiment is almost the same as the conventional thermal head drive circuit shown in FIG. 4, only that resistors R1 to Rn-1 are newly added to the embodiment shown in FIG. Since the basic steps of the printing operation are the same, only the parts related to the present invention will be explained for ease of understanding.

FIG. 2 is a diagram illustrating a specific operation of an embodiment of the present invention,
This is a partial extraction of the thermal head drive circuit shown in FIG. 1.

That is, when the thermal head indicated by 2-1 is selected by the block selection transistor 4-1, and only the transistor indicated by 3-2 among the heating element selection transistors 3-1 to 3-n is in the ON state. is taken as an example, and transistors that are not related to other operations are omitted from the diagram.

In this example, the heating element H in the thermal head 2-1,
The portion R2 corresponds to the pixel to be printed, and the other heating elements do not perform printing.

FIG. 3 is a comparison diagram of the current flowing through the heating element. The current flowing through the heating elements H, R, in Fig. 2 is Il, and the heating element H
It is a diagram for comparing the currents 1 and -L, where the current flowing through 2R2 is I7, the current flowing through the heating elements H and R is 13, and the current flowing through the heating elements H and R is 14.

The heating elements H, R, ~H, R, and the resistors R1 to R1 form a resistor network, and the transistor 3-2 is in the ON state.
A current flows through each heating element through the heating element. For example, as an example, R,=R2=R3...=Rn, and the resistance value of each heating element H5R"H+ R2=""'・=
If the value of each resistance value is set to a predetermined value as H+Rn, the current 11~ flowing through each heating element F(,R,~H,R,
l.

As shown in the comparison table in Figure 3, only the current value I2 exceeds the printing level current I0 and becomes a pixel on the printing surface, and the current flowing to other heating elements is due to the long distance from the heating elements H and R2. As the current increases, the current value decreases. Therefore, only the heating elements H, R, , H, R, which are adjacent to the heating element H, R2 which actually performs printing, are heated to the extent that uniformity of printing can be guaranteed.

〔Effect of the invention〕

Uniform printing can be achieved regardless of the number of printed pixels, and wasteful power consumption is reduced.

[Brief explanation of the drawing]

FIG. 1 shows a thermal head drive circuit according to an embodiment of the present invention.
Fig. 2 is an explanatory diagram of the operation of one embodiment of the present invention, Fig. 3 is a comparison diagram of the current flowing through each heating element, Fig. 4 is a conventional thermal head drive circuit, and Fig. 5 is a diagram of another conventional example. This is a thermal head drive circuit. 1... Serial/parallel conversion register, 2-1~
2-m... Thermal head (represented by code 2-i), 3-1 to 3-n... Heat generating element selection transistor (represented by code 3-i), 4-1 to 4 -m...Pro1 selection transistor represented by code 4-1),
5-1 to 5-n...Heating element selection transistor 3-
Human resistors to the base terminals of 1 to 3-n, 6-1 to 6-
m...Input resistor to the base terminal of block selection transistors 4-1 to 4-m, alphabet group a...serial data manual signal line, SD...serial data signal, A,
~An...Wiring connection symbol (lines with the same symbol in the diagram indicate that they are connected to each other), D, -Dn...Parallel output data of serial/parallel conversion register 1, H+ DI- H+ Dn%H2DI ~H2Dn, Hm
D, ~HmDn... Diode in the thermal head (
(represented by the symbol Hi Di), HIRl-H5Rn1
H2R1~H2Rn1HmR+~HmRn... Heating element in the thermal head (represented by the symbol Hi Ri)
, ~R,-1... Transistor for selecting heating element 31.3
- resistor connected between adjacent collectors of n

Claims (1)

[Scope of Claims] A thermal head including a plurality of heating elements forming pixels on a printing surface, means for holding print data signals for the thermal head, and controlling a predetermined heating element according to output data of the holding means. A driving circuit system for a thermal head, comprising means for selecting and means for applying a voltage to the heat generating elements selected by the selecting means, the input terminals on the power supply side of the plurality of heat generating elements in the thermal head. A thermal head drive circuit system characterized in that a resistive element is arranged between each terminal of the thermal head.