JPH02192964A - Thermal head drive ic - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal head driving IC, and more specifically, the present invention relates to a thermal head driving IC, and more particularly, to a thermal head driving IC equipped with a driving IC for correcting print density that varies depending on whether adjacent bits are turned on or off. It is related to printers.

[Conventional technology]

A thermal printer realizes recording by converting an electrical recording signal into a corresponding thermal pattern and transmitting it to thermal paper. The printing principle of a thermal printer is that a heat-generating element of an integrated circuit called a print head is brought into contact with thermal paper coated with or impregnated with an organic compound that develops color when heated, and the micro-heating element is instantaneously heated according to the printed information. It prints pixel-shaped characters and symbols.

Therefore, the structure of the mechanical part of the thermal printer is as follows.

The shell consists of a print head, a print head feeder, a thermal paper feeder, etc., although this varies depending on the type and structure of the printhead. Regarding thermal printers, for example, see Ii' Electronic Science, Vol. 28, No. 4, 1978.
It is listed in the publication of Sanpo Publishing on April 1, 2017.

FIG. 3 is a diagram showing an example of the configuration of a general thermal printer.

In FIG. 3, 1 is an electrical interface, 2 is a decoding circuit, 3 is a bell circuit, 4 is a buzzer circuit, 5 is a line feed circuit, 6 is a paper feed mechanism, 7 is a special function circuit, 8 is a data buffer, 9 10 is a print head drive circuit; 11 is a print head; 12 is a forward circuit; 13 is a pattern generation circuit;
1 is a carriage drive mechanism, 14 is a retraction circuit, and 15 is thermal paper.

Here, the line feed circuit 5, paper feed mechanism 6, bell circuit 3, buzzer circuit 4, special function circuit 7, forward circuit 12, backward circuit 14, and carriage drive mechanism 13 are not unique to thermal printers. Therefore, the explanation will be omitted. Print head formats (arrays) include those that scan horizontally with a head that has heat generating elements arranged in a vertical row (7 dots), and those that scan horizontally with a head that has heat generating elements arranged in a horizontal row (10 dots) at intervals. Some print heads scan in a zigzag pattern, some use a 5 x 7 or 7 x 9 dot matrix print head to scan in the horizontal direction, and some use segment-type heating elements lined up in a horizontal row to simply feed the paper. There is. When codes representing each character are sent from the CPU side, the printer receives them at the electrical interface circuit 1 and sequentially stores them in the data buffer 8. The code read from the data buffer 8 is converted into a dot pattern matrix by the pattern generation circuit 9, and transferred row by row to the print head drive circuit 10, where a voltage is applied to each dot of the print head 11. Drive the heating element. As a result, only the driven heating element of the head 11 is heated.
Record thermal paper.

Note that the print head drive circuit 10 in FIG.
Usually integrated into a semiconductor circuit as a driving IC,
The other parts, that is, the pattern generation circuit 9 and the data buffer 8, are built into the system side of the printer, and the print head 1-1 is a thin film type, thick film type, or semiconductor type head and is installed close to the platen and thermal paper. Placed.

FIG. 4 is a diagram showing the internal structure of the driving IC in FIG. 3.

The driving ICl0 is provided with the same number of head drivers 19 as the number of dots, each of which is connected to a heating resistor 18 in the print head 11 via a lead wire. The system side 16 of the printer is connected to the input side of the driver 19, and the input side 17 is connected to the tip of the print head 11, and the terminals corresponding to each heating resistor 18 are turned on and off according to the input. do. Further, the system side 16 of the printer is connected to the input side of the driving ICl0, and conventionally, adjacent dots are corrected within this system.

[Problem to be solved by the invention].

By the way, normally, when printing with a thermal printer, when a certain bit is in an on state, the print density may differ depending on whether the bit adjacent to that bit is on or off. This is because it is affected by the printing heat of adjacent bits. In order to avoid this influence, conventionally, a method has been proposed in which the printer system side compares the data of adjacent bits, correcting the current value of the bit only when the adjacent bit is on, and sending it. There is.

However, if such density correction processing is performed on the system side, the processing circuitry and software on the system side of the printer become increasingly complex.

In addition, similar conditions may occur not only in thermal printers but also in other printing elements and display elements in display devices, and in such cases, the same problem as in the case of "double series" occurs6.Objective of the Present Invention solves these conventional problems and provides a thermal printer with high print quality that eliminates the need for density correction processing on the system side and has a constant density that does not vary depending on whether adjacent bits are turned on or off. There is a particular thing.

[Means for Solving the Problems] In order to achieve the above object, the thermal printer of the present invention operates a plurality of printing elements.

In a driving IC that drives the output of multi-bit parallel data, a circuit is provided for each bit to automatically vary the output current of all bits according to the output state of adjacent bits on both sides. By operating a circuit to reduce the current value of the adjacent bit when the adjacent bit is on, the influence of the adjacent bit is corrected within the driving IC. There are certain characteristics.

[For production]

In the present invention, in an IC for driving multi-bit parallel data output such as a printing element or a display element, the output state of a certain bit is automatically changed according to the output state of the adjacent bit. Drivers that turn on and off depending on the state are connected in parallel for all bits. Thereby, the printing heat for all bits can be made constant regardless of the influence of the printing heat of adjacent bits. Also,
By incorporating a circuit for correcting the influence of adjacent bits into the driving IC, the processing circuit on the system side can be simplified.

〔Example〕

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

FIG. 5 is a comparison diagram of adjacent bit correction methods between a conventional thermal head and a thermal head according to the present invention.

In a device such as a printing element or a display element that outputs multi-bit parallel data, the output state of a certain bit may affect the output state of adjacent bits, as described above. In particular, in the thermal head of a thermal printer, the printing heat of a certain bit affects the printing immersion degree of adjacent bits, so this effect cannot be ignored when performing high-density printing.

As shown in FIG. 5(a), when adjacent bits are not corrected, focusing on the n-th bit and m-th bits 1 to 1, we get
There is no printing at both ends of the n-th bit, and there is printing at both ends of the m-th bit. In this way, when adjacent bits are not corrected, the print density of the m-th bit is 1+β compared to the print density of the n-th bit of 1, and the print is printed darker by +β.

Next, as shown in FIG. 5(b), conventionally, when adjacent bits are corrected on the system side.

In order to equalize the printing density of the n-th bit with no printing on both ends and the m-th bit with printing on both ends, data is compared with adjacent bits, and the printing time of the m-th bit is shortened to 1-β. Similarly, the printing time for the 1m-1th bit and the m+1th bit is shortened to 1-α. This allows the printing energy to match that of the n-th bit, so that the printing density becomes equal.

FIG. 5(C) shows each data value when adjacent bit correction according to the present invention is performed. In the present invention, the driving I
Since adjacent bit correction is performed within C, correction on the system side is not required, and as a result, printing time becomes constant. Since there is no printing on both ends of the n-th bit, there is no need for correction, and the printing density is 1. Since the m-th bit is printed at both ends, the printing density is corrected to 1 by setting the printing current to 1-β.

In this way, the conventional correction method was performed on the system side and shortened the printing time, whereas in the present invention, the correction method is performed within the drive IC and is performed using a method that reduces the printing current. ing.

FIG. 1 is a functional configuration diagram within a driving IC showing a first embodiment of the present invention.

In FIG. 1, 20, 21, and 22 are pre-drivers, and 923 to 31 are drivers each using an N-channel open-drain N-channel MOS transistor. Here, only three bits are shown: the (n-1)th bit, the n-th bit, and the (n+1)th bit, but all other bits are constructed in exactly the same way. Note that the control circuit is not limited to an N-channel type, and it is of course possible to use a P-channel open-drain P-channel MOS transistor. It is also obvious that the structure can be constructed by replacing the N-channel MOS transistor with an NPN bipolar transistor and replacing the P-channel MOS transistor with a PNP bipolar transistor.

The outputs of the drivers from the n-1st bit and the n+1th bit are connected in parallel to the output of the nth bit, and the drivers at both ends and the driver from the nth bit are combined to turn on three types of drivers. The output of the n-th bit is determined by the resistor. Since the output of the n-th bit also contributes to the data of the (n-1)-th bit and the (n+1)-th bit, correction is possible.

FIG. 2 is a detailed circuit diagram of the driving IC shown in FIG. 1.

In FIG. 2, 33 to 38 are amplifiers, respectively.
n, n-1, and n+1 indicate the relevant bit and both adjacent bits.

In this example, the current of the bit is controlled by an output obtained by inverting the voltage of both adjacent bits.

In other words, the n-th driver output current has n+1
Amplifier 35 controlled by the inverted output of the bit-th current
and an amplifier 36 controlled by the inverted output of the current of the n-1th bit are connected in cascade, and when the dots of both adjacent bits are on, the current of the corresponding bit is reduced by that amount. Of course.

When the adjacent bit's dot is off, the amount decremented is zero. Thereby, it is possible to reduce the current of the bit to 1-β.

FIG. 6 is a functional configuration diagram within a driving IC showing a second embodiment of the present invention.

In FIG. 6, 41 to 43 are predrivers, 44 to 4
6 is an N-channel MoS transistor (driver), 47
49 is a modulation circuit that modulates the ON resistance of the driver.

In this embodiment, the output of the (n-1)th bit and the output of the (n+1)th bit are connected to the modulation circuit 48 of the n-th bit, and the modulation circuit 48 performs three-value level conversion.
Create three types of gate voltages at N time.

FIG. 7 shows a modulation circuit in the driving IC of FIG. 6.

In this embodiment, a modulation circuit 48 that controls the output of the n-th bit
The output of the n-1th bit is connected to the transistor T1, and the output of the n+1th bit is connected to the transistor T2.
connected to.

For example, when the (n-1)th bit driver 1- is turned on, the transistor T□ is turned off, a voltage drop occurs due to the resistor R, and the supplied voltage level is lowered. Further, when the n-1th bit is off, the transistor T□ is on, and no voltage drop occurs due to the resistor R1.

Similarly, when the (n+1)th bit is on, a voltage drop occurs due to the resistor R2, and when it is off, no voltage drop occurs.

Also, when the n-L bit and n+1 bit dots are turned on at the same time, the voltage drop due to resistor R1 and the voltage drop due to resistor R2 are added, so a lower voltage is generated than when they are alone. .

In this way, three types of ON gate voltages of the driver 45 can be created and applied.

Therefore, by appropriately setting the values of R□ to R3,
By correcting the print current when an adjacent bit is applied, the bit can be set to 1-β as shown in FIG. 5(C).

〔Effect of the invention〕

As described above, according to the present invention, since the influence of adjacent bits is corrected within the driving IC, no processing is required on the system side, and the printer system is significantly simplified.

[Brief explanation of the drawing]

FIG. 1 is an internal configuration diagram of a driving IC showing a first embodiment of the present invention, FIG. 2 is a detailed circuit diagram of FIG. 1, FIG. 3 is a block configuration diagram of a general thermal printer, and FIG. 4 3 is a diagram of the drive IC and other internal configurations, FIG. 5 is a comparison diagram of the conventional correction method of a thermal printer and the correction method of the present invention, and FIG. 6 is a drive IC showing a second embodiment of the present invention. The functional configuration diagram in FIG. 7 is a modulation circuit in the driving IC of FIG. 6. 8: Data buffer, 9: Pattern generation circuit, 10: Driving IC111 print head, 15: Thermal paper, 16
: Printer system, 17: Print voltage common electrode, 18
Two heating resistors, 19: Driver, 20-22: Pre-driver, 23-31: N-channel open drain N-channel MOS transistor driver, 33-38: Amplifier, 41-43: Pre-driver, 44-46 Two N channels MOS transistor (driver), 47 to 49: modulation circuit. Patent Applicant Rico Co., Ltd. Representative Patent Attorney Masatoshi Isomura

Claims (1)

[Claims] (1) In order to operate multiple printing elements, in a drive IC that drives the output of multi-bit parallel data, the output current of all bits is automatically adjusted according to the output state of adjacent bits on both sides. A variable circuit is provided for each bit, and the variable circuit is operated to reduce the current value of the bit when the adjacent bit is on, thereby correcting the influence of the adjacent bit within the driving IC. A thermal head driving IC characterized by: