JPH03153367A - Thermal head - Google Patents

Abstract

PURPOSE:To simplify circuits for obtaining a low cost thermal head which is compact in shape and easily controllable, by a method wherein block driving pulse signals are output on receipt of serial pulses input from a counter. CONSTITUTION:Heating resistance bodies R1 - R2048 to which a voltage VH is applied are driven by drivers IC1 - IC32 which are divided into eight blocks each containing 256 drivers, for example. A counter CT counts driving pulses input from a STROBE signal terminal, and sequentially outputs (C,B,A)=(0,0,0) to (1,1,1) for three bit output A, B, C. On receipt of this output, a decorder DC selects signals ST1 - ST8 and makes them active in turn, and the drivers IC1 - IC32 drive the heating resistance bodies R1 - R2048 in eight divisions.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a thermal head used as a print head of a printer, for example.

(b) Conventional technology Traditionally, line-type thermal heads have a large number of heating resistors, and when printing one line at the same time, a large amount of current flows, and a very large-capacity power source is required. In order to reduce the power supply capacity, the heating resistor is divided into sliding blocks and driven in a time-division manner.

FIG. 3 is an example of a block diagram of a thermal head that performs eight-division driving. 2048 heating resistors R1 to R204
8 is driven by 32 drivers ICI to IC32, but these drivers are divided into 4 blocks of 8ffl each, and each block is 5TROBEI-8T.
[Eight division driving is performed by eight block drive pulse signals of 10BE8.

FIG. 4 is a basic circuit diagram of one of the drivers IC1 to IC32, and includes a 64-bit shift register 11 and a 64-bit shift register 11.
It consists of a bit latch circuit 12, an output protection circuit 13, a gate circuit 14, and a 64-bit driver element 15. DA which is the output terminal of the 64-bit shift register 11
The TA OUT terminal 16 is connected to the DATA 1N terminal 21 which is the input terminal of the shift register of the next stage driver, and as shown in FIG. 5, 32 64-bit shift registers in 32 drivers are serially connected.

In addition, 17 is a drive voltage VH input terminal, 18 is B, E, 0
Signal terminal, 19 is 5TROBE signal terminal, 20 is LAT
This is a CH signal terminal.

FIG. 5 is a timing chart during 8-division driving. The following describes the printing procedure for one line according to FIG. 5. First, data for 2048 dots is sent from the DATA IN terminal 21 to all shift registers in synchronization with the CLOCK signal, and the LATCH signal is activated to print data for the 2048 dots. The print data is latched by the latch circuit 12. Next, after activating the B, E, and O signals to make the heating resistor drivable, 8
The block drive pulse signals 5TROBEI to STROBEg are sequentially activated in a time-sharing manner for each divided block to drive the heating resistor, thereby printing 1942 minutes. Here, the signal 5TROBEI-8TROBE
The eight signal lines of No. 8 are connected to the outside by connectors.

(c) Problems to be solved by the invention However, in such a conventional thermal head,
There are many signal lines for driving the thermal head from the outside, the dimensions of the connectors and the like that serve as the joining means are large, and the control side circuits are also complicated and expensive.

This invention was made in consideration of these circumstances,
By simplifying the circuit, it is possible to provide an inexpensive thermal head that is compact in shape and can be easily controlled.

(d) Means for Solving the Problems This invention counts and outputs input serial pulses in a thermal head that divides a plurality of heating resistors corresponding to printed dots into a plurality of blocks and drives them in a time-division manner. A thermal device comprising a drive pulse counter and a decoder that receives an output of the counter and outputs a block drive pulse signal, and drives each block of the heating resistor in a time division manner using the block drive pulse signal output from the decoder. It is the head.

In this invention, since the period of the serial pulse can be set to the driving pulse width of the heating resistor, the printing density can be controlled by changing this period. Therefore, if the thermal head is provided with a temperature detection element such as a thermistor, and the period of the serial pulse is changed according to the temperature detection output, it is possible to print with uniform density even if the temperature of the thermal head fluctuates.

(E) The action counter counts and outputs manually input serial pulses, and the decoder receives the output of this counter and selectively generates a plurality of block drive pulse signals. Therefore t
A plurality of heat generating resistor blocks can be driven in a time-division manner using the serial pulse input terminal of the Ut, and there is less damage to the connection line between the thermal head and the external control block.

(f) Example Embodiments of the invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention,
The heating resistors R1 to R2048 to which voltages v and l are applied are driven by a driving driver ICI A-IC32 divided into 891 blocks of 256 each. Counter CT! 9 Counts the drive pulses input from the TROBE signal terminal and outputs 3 bits A, B.

In C (C, B, A) = (0, O, O) ~ (1, l.

l) are output sequentially. Upon receiving this output, the decoder DC selects the signals STI to ST8 and sequentially activates them, and the drivers IC1 to IC32 activate the heating resistors R1 to R1 to ST8.
Drive R2048 in 8 parts.

Figure 2 shows the drive pulse input signal 5TROBE, counter output signals A, B, C, and decoder output signals STI to ST8.
3 is a timing chart showing B, E, and O signals.

In the driver, as shown in Figure 5, DATA I is synchronized with the CLOCK signal in the same way as before.
After inputting print data from the II terminal 21 and causing the latch circuit 12 of the driver to latch the print data using the LATCH signal, input of the drive pulse input signal 5TROBE is started. At the same time, B, E, and O signals that enable driving of the heating resistor are given. These B, E, and O signals are also input to the counter CT and decoder DC as shown in FIG. It also plays the role of positive logic). Therefore, when the B, E, and O signals become "H", it is immediately after the counter reset is released, so the counter output (C, B, A) = (0, 0, 0)
Therefore, only the decoder output signal STI becomes active (negative logic). If the period of the 5TROBE pulse is T, then after the signal STI is active for a time T,
At the rising edge of the next 5 TROBE pulse, the output of the counter CT becomes (C, B, A)=(0,0°l), so the signal ST2 is switched to active.

Thereafter, signals ST3 to ST8 are similarly switched while maintaining the time width T in synchronization with the rising edge of the 5TROBE pulse. Finally, the B, E, and O signals are set to "L" to complete printing by 8-division drive for one line.

In the above, the counter CT started from (C, B, A) = (0, 0, 0) in the reset state by the B, E, and O signals, but if the counter CT is an octal counter, it is not necessarily (C , B, A) = There is no need to start from (0, 0, 0). Further, by changing the period T of the 5 TROBE pulse, the pulse widths of the signals 1 to ST8 can be changed, so that it is also possible to control the printing density.

By adding a relatively simple circuit as described above,
The thermal head can be driven in a time-division manner by a single drive signal line to drive a plurality of heat generating resistor blocks.

Incidentally, in the above embodiment, the description has been given of driving the thermal head in eight divisions, but the present invention is not limited thereto. Further, the number of heating resistors and driver ICs is not limited to the above.

(G) Effects of the Invention According to this invention, multiple heat generating resistor blocks can be easily time-divisionally driven using a single drive signal line using a simple and inexpensive circuit provided uniquely to the thermal head. , the circuit for controlling the thermal head and the connection structure are simplified, thereby providing a thermal head driving device that is inexpensive and compact in total.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a thermal head showing an embodiment of the present invention, FIG. 2 is a timing chart for driving one line of the thermal head shown in FIG. 1, and FIG. 3 is a diagram showing a conventional thermal head. Figure 1 corresponds to Figure 4, Figure 3 corresponds to Figure 3.
FIG. 5 is a circuit diagram showing the main parts of the figure, and FIG. 5 is a timing chart showing the operation of the conventional example shown in FIG. wt2rttx Rl-R2048... Heating resistor, tct-
IC32 resistor driver, CT...Pulse counter, DC...Decoder. (C)

Claims (1)

[Claims] 1. In a thermal head that divides a plurality of heating resistors corresponding to printed dots into a plurality of blocks and drives them in a time-division manner, there is a drive pulse counter that counts and outputs input serial pulses, and a drive pulse counter that receives the output of the counter. 1. A thermal head comprising: a decoder that outputs a block drive pulse signal, and each block of a heating resistor is driven in a time division manner by the block drive pulse signal output from the decoder.