JPH0832457B2 - Thermal head control circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit of a thermal printer, and more particularly to a density control circuit of its heat generating element.

[Prior Art] Conventionally, various proposals have been made to correct print density in a thermal printer.

As an example, the heating element is increased at both ends of the thermal head to increase the amount of heat generation, or the applied energy at both ends is increased to increase the amount of heat generated by the head, as in JP-A-51-145325 or JP-A-60-260357. There has been proposed a method of flattening the temperature distribution of (1) by suppressing heat generation in the central part.

[Problems to be Solved by the Invention] In all of these conventional examples, it is completely meaningless when printing is performed, that is, when only a specific range of heating elements arranged in a row is intensively used. There was an important defect.

For example, in a serial printer, it is common to print characters in a 24 x 24 matrix in the text mode and 16 dots in the bit image mode. Areas will be different.

Also, which area is frequently used in a facsimile or the like depends on the transmitted image data and cannot be predicted at all.

That is, the conventional method of fixedly increasing the heat generation amount at both ends of the thermal head or at the end of each block has a drawback that it cannot flexibly cope with the above situation.

The present invention has been made in view of such disadvantages, and its object is to increase the heat generation amount at both ends of any heat generating element that is heated in parallel at the same time, and by always averaging the print density, It is to provide a thermal printer with good print quality.

Another object of the present invention is to reduce the load on a processing device such as a CPU by consolidating the functions of automatically detecting heat generation data along with the head control circuit and automatically increasing the heat generation amount at both ends. The purpose of the present invention is to provide a head control IC for a thermal printer, which can be used for a wide range of purposes and can perform similar control even with a line type head having a large number of heat generating elements.

[Means for Solving the Problems] In order to solve the above problems, the present invention relates to a storage circuit that stores drive data corresponding to a plurality of heat generating elements and a first strobe input that defines an energization time to the heat generating elements. And a first gate circuit that outputs a logical product of adjacent heating elements on both sides of an arbitrary heating element of the plurality of heating elements,
An input terminal of a second strobe input for changing the energization time to any heating element according to the output of the first gate circuit, a first strobe input, a second strobe input, and a first strobe input. A second gate circuit that determines the energization time to the plurality of heat generating elements from the output of the gate circuit and the output of the memory circuit, and the drive data of an arbitrary number of adjacent heat generating elements that are simultaneously driven by the heat generating elements. Is a head control circuit for a thermal printer, which is configured to increase the energization time of both ends of an arbitrary number of adjacent heat generating elements when the energization data are simultaneously supplied.

[Embodiment] FIG. 1 is a schematic view of an embodiment of a thermal printer using a head control circuit according to the present invention.

1 is a thermal head in which a plurality of heat generating elements 1a are arranged, 2
Is a latch circuit which is a kind of storage circuit for temporarily storing the drive data output from the CPU 5, and 4 is a head drive circuit for turning on and off the energization of the heat generating elements of the thermal head.

Reference numeral 12 is an AND circuit of the first gate circuit that outputs a logical product of drive data at both ends of an arbitrary heating element. This output is passed through the inverter 13 to the AND circuit 1 which is the second gate circuit.
Entered in 1. The AND circuit 11a corresponds to the heat generating elements at both ends and does not have this input terminal because there is no corresponding AND circuit 12 at the end.

7 is an input terminal of the first strobe input for setting the energization time when outputting the drive data, and 8 is a second strobe input for increasing or decreasing the energization time depending on the adjacent drive data of an arbitrary heating element. Input terminals are shown respectively.

Reference numeral 3 is a gate circuit group for mixing the energization time signal input from the input terminals of the first and second strobe inputs, a logical product output of adjacent data, and drive data output to output energization data to the head drive circuit 4. .

A head control circuit is formed by the latch circuit 2 and the gate circuit group 3 and is integrated with a head drive circuit to form a head control IC 10.

Reference numeral 6 is an energization width control circuit that produces an energization time signal to the input terminals of the first and second strobe inputs.

The energization width control circuit 6 includes resistors 21, 22, 24, 25, 26, a transistor 27, a capacitor 30, a thermistor 23, comparators 28, 29, an inverter 33, an AND circuit 34, load resistors 31, 3.
It consists of two. T in synchronization with the CPU5 energization timing
When RIG is output, the charging time of the capacitor is output from comparators 28 and 29.

The output time of the comparator 28 is TW1, and the output time of the comparator 29 is TW2. The inverter 33 and the AND circuit 34 make the output time of TW1-TW2 = TW3. Pulse width TW2
Is the main energization time, and the pulse width TW3 is input to the gate circuit group 3 as the sub-energization section.

The AND circuit 12 mixes the AND signal of the energization signal of the sub-energization section TW3 and both sides of arbitrary drive data with the logical product, and this output is further input to the AND circuit 11 which obtains the logical product output via the inverter 13. It The AND circuit 11 is arranged corresponding to the output terminal of the stored drive data, and the main energization section TW2
With the energization signal of and the output signal of the inverter 13 as input,
A head drive signal corresponding to drive data of an arbitrary heat generating element and drive data of an adjacent heat generating element is output.

FIG. 2 is an explanatory diagram showing a driving method and operation of the thermal headed control circuit according to the present invention.

Reference numeral 41 indicates dots formed by energization, shaded areas indicate energized dots, and white circles indicate non-energized dots.

In the example of FIG. 2, the drive data H1 to H8 and H11 to H16 are energizing dots. 42 shows the head drive signal at this time, and the energization time is the main energization section TW2 + the sub-energization section TW13 value at both ends that are energized side by side at the same time, that is, H1, H8, H11, and H16. It becomes a value.

Reference numeral 43 shows the temperature distribution of the thermal head, in which the temperatures of the heat generating portions at both ends tend to be slightly higher, but the density is almost uniform.

Further, the thermistor 23 of the energization width control circuit 6 is installed to feed back the ambient temperature of the thermal head or the substrate temperature to the energization time, and the ratio of the main energization section to the sub energization section to the total pulse width TW1 is calculated by the comparator. It becomes almost constant at all times and the uniformity of concentration is maintained against temperature fluctuations.

By combining the thermal head control circuit according to the present invention and the past drive data and combining it with the history control method of suppressing the energy applied to each heat generating element, the print density can be made more uniform.

In the present embodiment, only one adjacent dot is reflected in the energization time, but by further using the adjacent dot as a gate circuit to increase the strobe input terminals, the uniformity of density can be further maintained.

[Effects of the Invention] According to the present invention, it is possible to make the print density of the heating elements arranged in a row in a uniform manner regardless of the print pattern, which is extremely useful.

Compared to the conventional general data processing that uses a CPU or other processing device, a gate circuit that directly detects the state of adjacent dots is provided in the drive data storage circuit for any heating element. Moreover, since the strobe input for setting the energization time is applied to this gate circuit, the desired processing is automatically executed after the drive data is output, which greatly contributes to the speeding up of printing. be able to.

In addition, memory circuit, gate circuit, head drive circuit
By integrating it as an IC, it can be realized at almost the same cost as a head drive IC that has been used conventionally, and if it is mounted on a thermal head, a device using a thermal printer can be made compact and the printing quality can be improved. It is extremely useful because it can be achieved at the same time.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a thermal head control circuit according to the present invention. FIG. 2 is an explanatory view showing the driving method and operation of the thermal head control circuit of the present invention. 1 ... Thermal head 2 ... Memory circuit 4 ... Head drive circuit 7 ... Input terminal for first strobe input 8 ... Input terminal for second strobe input 10 ... Thermal head control IC 11 ... Gate circuit 2 ... 1st gate circuit

Claims (2)

[Claims] 1. A thermal head control circuit for driving a plurality of heating elements arranged side by side in a row, a storage circuit for storing drive data corresponding to the plurality of heating elements, and an energization time to the heating elements. An input terminal of a first strobe input for defining the above, a first gate circuit for outputting a logical product of heating elements adjacent to both sides of any heating element of the plurality of heating elements, and the first gate circuit. An input terminal of a second strobe input for changing the energization time to the arbitrary heat generating element according to the output of the first strobe input, the first strobe input, the second strobe input, and the output of the first gate circuit. And a second gate circuit that determines the energization time to the plurality of heat generating elements from the output of the memory circuit, and the driving data of an arbitrary number of adjacent heat generating elements that are simultaneously driven of the heat generating elements are simultaneously output. Communication When data adjacent any of the thermal head control circuit, characterized in that the energizing time of the both end portions of the heat generating element having been configured to increase. 2. The head drive circuit for driving the heat generating element is integrated with the memory circuit, the first gate circuit and the second gate circuit as an integrated circuit (IC). The thermal head control circuit described in the item.