JPS60237763A - Driving circuit for heating resistor - Google Patents

Abstract

PURPOSE:To perform high-speed recording without spoiling print quality by selecting one of plural strobe signals according to one selection signal, and driving the heating resistance with period print data of the selected strobe signal. CONSTITUTION:One-line serial print data D is inputted to an N-bit shift register 53a from an input terminal 54 synchronously with a clock C and held in a latch circuit 53b with a latch signal L. On the other hand, while the one-line print data D is transferred, selection data SD is inputted to an N-bit shift register 53c synchronously with the clock C and this data is latched in a latch circuit 53d. Here, print data L1-LN in the circuit 53b are connected to bits ''1'' of the heating resistance 51 and selection data SL1-SLN in the circuit 53d are connected to bits ''1''; this heating resistance 51 is powered on only for the on time of the 1st strobe signal S1 from an input terminal 57.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a heat generating resistor drive circuit for driving a heat generating resistor of a thermal head.

[Conventionally good book]

In recent years, thermal recording methods and thermal transfer recording methods have shown remarkable development due to their simplicity, and as a result, high-speed printing and high print quality are required. Various ideas have been made.

Conventionally, there has been a heating resistor drive circuit of this type as shown in FIG. In the figure, numeral 1 denotes N heat generating resistors arranged on a substrate serving as a heat generating resistor, 2 a common electrode to which one end of each of the N heat generating resistors l is connected, and 3 a common electrode provided opposite to the common electrode 2. This is a shift register circuit with a driver connected to the other ends of the N individual heat generating resistors 1, and this is a drive circuit for the heat generating resistors. 4 to 7 are signal input terminals of the drive circuit 3, 4 is an input terminal to which a strobe signal S for controlling ON/OFF of the current flowing through the heating resistor 1 is inputted, and 5 is an input terminal for launching print data D. an input terminal to which a latch signal is input for
is print data D for driving heating resistor 1 to print
7 is an input terminal to which a clock C for synchronization with data D is input.

Next, the operation will be explained. Common electrode 2 has heating resistor 1
are connected to each other, and a common electrode 2 is connected to the heating resistor l.
When a voltage from VH to VH is applied, if the other end of the heat generating resistor 1 on the substrate is grounded, current flows through the resistor 1 and generates heat. This energization corresponds to one line of printing. In the thermal recording method, printing is performed when thermal paper receives this heat generation.

In order to selectively drive the grounding of the N heating resistors l based on one line of print data, a simple method is to control the transistors serving as drivers using the parallel outputs of the shift registers.

■The print data of the line is expressed in two values, I" and '0", and the data DI is output from the signal input terminal 6 in synchronization with the clock C.
, D2. ...Shift register 3 for one line in the order of DN
Enter a.

When the launch signal is applied to the signal input terminal 5,
One line of serial print data Ll, L is stored in latch 3b.
2. ...LN is held, and each print data L1 to LN
is input to the NAND circuit 3c together with the strobe signal S.

Therefore, the print data L1 to L held in the lunch 3b
When N is "1", the heating resistor 1 connected to the output of the NAND circuit 3b only when the strobe signal S is "H"
A current flows through the resistor 1, and the resistor 1 generates heat.

The above timing chart is shown in FIG. Here the second
Figures (a) to (81) show the waveforms of the clock c1 data D1 latch L1 strobe signal S and applied voltage VH, respectively, and in the second FI!J (d), TI is the printing period of one line, and T2 is the printing time ( The ON time of the heating resistor) is shown.

Now, there is usually a delay between the timing of applying a pulse to the heat generating resistor 1 and the timing of its heat generation, and the heat generation and heat dissipation characteristics of the heat generating resistor 1 become an important issue.

That is, if the printing cycle T1 is long enough to radiate heat from the heat generating resistor 1, as shown in FIG.
), the shape of the printed dots printed on the thermal paper is uniform as shown in FIG. 3 fc), and the print quality is satisfactory.

However, as shown in Fig. 4 (Ta), when printing at high speed by shortening the printing cycle T3 as much as possible, there is a heat storage effect of the printing dots on the previous line, and the shape of the printing dots changes, as shown in Fig. 4 (Ta). As shown in FIG. 4 (JC), problems such as gradually increasing the size and ink smearing on the thermal paper occur.

In order to prevent this, - As shown in the timing chart in Figure 5, if there is printing on the previous line, the ON time T5 of heating resistor 1 will be set for the printing of the next line to be the same as when there was no printing on the previous line. It is necessary to make it shorter than the ON time T4. Also, if there is no printing on the previous line, turn on the heating resistor.
It is necessary to restore time T4. It is impossible to perform the control shown in FIG. 5 using only one strobe signal, and the control shown in the timing chart of FIG. 6 is required.

In FIG. 6, the current serial data D1 to be printed is transferred at time T6. At time T7, when the heating resistance data of the previous line is "1", when the current print data is "0", it is "0", when the current print data is "1", it is "o", and for the previous line. When the heating resistance data is "0" and the current print data is "0", it is "0", and when the current print data is "1", it is "0".
1" is transferred as serial data D2. Therefore, the current print line data D1 is determined by the control data D2 indicating whether or not the previous line is printed and whether or not the current line is printed. If the previous line is not printed, the previous line is printed during time T4. In this case, the molding is carried out for a period of time T5, thereby making it possible to perform the same control as shown in FIG.

However, in this control method, it is necessary to transfer data twice for one line of printing, so the period T3 is limited in the case of high-speed printing.

The above explanation assumes that the resistance values of the heating resistors 1 are all the same, but in reality there is a variation of about ±15% of the average value, and even if the control is performed as shown in Figure 5, high printing quality cannot be achieved. No.

Furthermore, when performing gradation recording, for example, if one line requires four gradations, it is necessary to switch the energy applied to the heating resistor into four stages. For this purpose, in the timing chart shown in Figure 6, in addition to transferring 1 line of print data, 3 gradation recording data are transferred for 1 line printing.
need to be transferred twice. Therefore, the data transfer time is 1
The line printing time is limited, and the printing speed is also limited.

The conventional heating resistor drive circuit is configured as described above, and the energization time of each heating resistor is determined by the 08 hours of one strobe signal, which reduces the resistance value variation of the heating resistors. If this is large, uneven printing density will occur, and correction data must be transferred to prevent trailing and blurring of the print due to the heat accumulation effect of previous line printing during high-speed printing.Furthermore, in gradation recording, one line There were drawbacks such as the inability to print at high speed.

[Summary of the invention]

This invention was made to eliminate the drawbacks of the conventional ones as described above, and it is possible to select one of a plurality of strobe signals according to a selection signal for determining the drive time of a heating resistor, and to By driving the heating resistor with the print data for the period of the selected strobe signal, it is possible to reduce the influence of resistance value variations in the heating resistors on printing quality, and high-speed recording can be performed without degrading printing quality.
The object of the present invention is to provide a heating resistor drive circuit that is capable of high-speed gradation recording.

[Embodiments of the invention]

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

FIG. 7 shows a heating resistor drive circuit according to an embodiment of the present invention, and this shows a case where there are two strobe signals and one selection signal. In FIG. 7, reference numeral 51 denotes N heat generating resistors arranged on a substrate serving as heat generating resistors, 52 a common electrode to which one end of each of the N heat generating resistors 51 is connected, and 53 a common electrode facing the common electrode 52. 54 to 59 are signal input terminals of the drive circuit 53, and 56 is a signal input terminal for a latch signal. , 55 is an input terminal for data D for driving the heating resistor, 54 is an input terminal for clock C for synchronizing with data D, 51.
58 turns on/off the current flowing through the heating resistor 51 like a switch.
1st for OFF control. Second strobe signal SL
, S2 input terminal 59 is the first . Selection data SD for selecting one of the second strobe signals 31°S2
This is the input terminal of

In the drive circuit 53, 53a is a shift register into which one line of print data D is stored, 53b is a latch circuit which latches the parallel output output of the shift register 53a, and 53c is a shift register (selection signal input circuit) into which selection data SD is stored. , 53d is a launch circuit that launches the output of the parallel output of the shift register 53c, 53e is an AND circuit that combines the outputs of the launch circuits 53b and 53d and the first strobe signal 3.1, and 531 is an AND circuit of the latch circuit 53b. This is an AND circuit that uses three people to generate the output, an inverted signal of the output of the launch circuit 53d, and the second strobe signal S2, and both AND circuits 53e and 53f serve as strobe selection circuits. 53g is two AND circuits 53e, 5
NOR that uses the output of 3f as 2-man power and drives the heating resistor 1
It is a circuit (driver).

Next, the operation will be explained using the timing chart of FIG. 1 line of serial print data D is input terminal 5
5 to the N-bit shift register 53a in synchronization with the clock C, and is input to the latch circuit 53 by the latch signal.
b, and serves as a signal indicating whether or not to energize the heating resistor 51 in one line. On the other hand, at the same time as one line of print data D is transferred, selection data SD is transferred to clock C.
The data is input to the N-bit shift register 53C in synchronization with the first . Second strobe signal 31. This is a selection signal for selecting which of S2 to use.

Here, the print data L1 to LN of the launch circuit 53b is "1".
” and the selection data SLI to S of the latch circuit 53d
The heating resistor 51 connected to the bit with LN of 1'' is energized only during the ON time of the first strobe signal S1 from the input terminal 57.

Also, the print data L1 to LN of the launch circuit 53b are “1”.
and the selection data SL1 to SLN of the latch circuit 53d
The heat generating resistor 51 connected to the bit with 0'' is energized only during the ON time of the second strobe signal S2 from the input terminal 58.

For example, the period of the first strobe signal S1 is T6 and O
N time is T4, period of second strobe signal S2 is T6
Let us consider the case where the ON time is T5 and N-4. Now, "0", 0'',
Print data L1 to L4 of "1" and "1" are held, and 0", "1", and "0" are stored in the selection data launch circuit 53d.
, "1" selection data SLI to SL4 are held, the heat generating resistors R1 and R2 are not energized, and the heat generating resistors R3 and R4 are heated for a time T5 . It will be made into a temporary die of T4.

The apparatus of this embodiment as described above can provide the following effects.

(i) If the current line printing with previous line printing is controlled with the second strobe signal S2, and the current line printing with no previous line printing is controlled with the first strobe signal S1, the fifth The system shown in the figure.

Compared to the conventional method, data transfer can be completed once without transferring correction data, and the period T6 can be made shorter than the period T3, enabling higher-speed printing. This timing chart is shown in FIG. Here, 1a) to +gl in FIG. 8 are clocks C2, print data D1, and selection data SD, respectively.

The waveforms of the latch L, the first strobe signal SL, the second strobe signal S2, and the applied voltage VH are shown.

(11) In addition, if the resistance value of the heating resistor 51 varies widely, for example, if the resistance value varies by ±15% among the heating resistors R1 to RN, then the heating resistor 51 has a variation of ±15% from the lowest resistance value to 15% to 0%. 51 is assigned to the energization control by the first strobe signal S1, and the heat generating resistor 51 with a high resistance value varying from 0% to +15% is assigned to the energization control by the second strobe signal S2, as shown in the timing chart of FIG. If one line is printed using the control method shown, ±
The printing result is similar to that of a resistance value variation of 7.5%, which means that the drive circuit 53 can reduce resistance value variation.

Above, we have explained the case of two strobe signals and one selection signal, but if we consider the drive circuit shown in Figure 7 as one set of basic configuration, we will use 2m strobe signals and m selection signals. If you expand the case and control the energization of the heating resistor,
Furthermore, in the case of high-speed printing, it is possible to cancel out the heat accumulation effect of printing the line before the previous line or the line before the previous line, further reducing the variation in resistance value, and furthermore enabling high-speed gradation recording. . This timing chart is shown in FIG. Here, Fig. 9 Ca1(b) (cl)~
(cm) (dl (el) ~ (e (2m))
(f) are clock C2 print data D, first to mth selection data SD1 to SDm, latch L, first to second
m strobe signals 31 to S (2m) and applied voltage VH
The waveform of is shown.

In the above embodiment, the latch signal is transmitted to the latch circuit 53b for one line of print data and the latch circuit 53 for selection data.
Although the explanation has been given on the case where the latch signal is connected to d, a separate latch signal may be used in the case of high-speed printing that involves a heat storage effect or aims at high gradation recording.

Further, in the above embodiment, the case of 2m strobe signals and m selection signals has been explained, but the present invention uses a multiplexer to convert one of 2 (2 to the power of i) strobe signals into one The selection may be made using a selection signal, and the same effects as in the above embodiment can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, one of the plurality of strobe signals for determining the driving time of the heating resistor is
Since one of the two strobes is selected according to the selection signal and the heating resistor is driven by the print data for the period of the selected strobe signal, it is possible to reduce the influence of resistance value variations of the heating resistors on printing. It has the effect of enabling high-speed recording without compromising quality, and also enables high-speed gradation recording.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a conventional heating resistor drive circuit, FIG. 2 is a diagram showing a timing chart of input signals in the conventional circuit, and FIGS. Figure 6 shows a timing chart when the influence of heat accumulation is controlled by the energization time when there is heat accumulation.
7 is a diagram showing a timing chart of a conventional method for controlling the influence of heat storage, FIG. 7 is a configuration diagram of a heat generating resistor drive circuit according to an embodiment of the present invention, and FIG. 8 is a timing chart of the heat generating resistor drive circuit. FIG. 9 is a diagram showing a timing chart in another embodiment of the present invention. 51...Heating resistor, 53C...Shift register (
selection signal input circuit), 53e, 53f...AN, D circuit (strobe selection circuit), 53g...NoR circuit (
driver). Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masuo Oiwa Figure 1 Figure 2 (e) □ Figure 3 Figure 4 Figure 5 (C) ... Figure 6 (e) Figure 8 (9) Figure 9 ([- (f) □

Claims (1)

[Claims] (11) A strobe signal generation circuit that generates a plurality of strobe signals for determining the drive time of the heating resistor, and a selection signal input that holds a selection signal for selecting the plurality of strobe signals. a strobe selection circuit that selects one of the plurality of strobe signals according to the output of the selection signal input circuit; and a driver that drives the heat generating resistor with the period print data of the selected strobe signal. A heating resistor drive circuit characterized by comprising: (2) The number of the strobe signals is 2m (m is a positive integer), and the number of selection signals is m. The heating resistor drive circuit described in paragraph 1. (3) The number of the strobe signals is two (l is a positive integer).
2. The heating resistor drive circuit according to claim 1, wherein the selection signal is one.