JPH02196668A - Thermal printing drive system - Google Patents

Abstract

PURPOSE:To form the capacity of a drive power source in approx. capacity necessary in average to provide a practical thermal print driving system by delaying a next printing timing until a power source voltage is recovered after the fact that the power source voltage is lowered to a predetermined value or less is detected by voltage drop detecting means. CONSTITUTION:A drive power source 2 for the internal connection of parallel thermal heads 1 is provided to supply a current of 0.25 A, and power from the drive power source 2 is connected to the common terminal of heat generating resistance elements of the thermal head 1 and one input terminal of a comparator 4. On the other hand, a reference voltage Vs of a reference voltage setter 5 is input to the comparator 4. In the drive circuit, the voltage of the drive power source 2 is compared with the reference voltage Vs to detect a voltage drop. If it is extremely lower than the reference voltage Vs, i.e., if the voltage drop is large, next printing timing, i.e., a strobe signal is output after the margin of the time up to the recovery, i.e., the delay time. On the other hand, if a black ratio is low so that the voltage drop is not so large, the delay time is relatively shortened, and shifted to next printing. Thus, the drive power source 2 can be reduced to a small capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a thermal printing control method for a parallel thermal head in which a plurality of heating resistive elements are connected in parallel and print simultaneously.

(b) Conventional technology In general, a parallel thermal head has a plurality of heat-generating resistive elements arranged in a row on a substrate, and prints are recorded by simultaneously passing a drive current through these heat-generating resistive elements. is shown in Figure 3. In FIG. 3, the parallel thermal rad 1 includes a plurality of heating resistive elements R-+r.
, R-Iz, R-Iz,... R-IN to R-R
1, R-nt, R-R3, . . . R-RN resistance elements are connected in parallel, and in order to supply data for energizing each of these resistance elements, the print data is connected to D-11 and D, respectively.
-1! ,D-Iz ,...D-IN S"'% D
-111% D-nt s D-1%3% ”'5D-
nN, and these data are input to the gate G −+
+, G-It,, G-11,..., G-IN%...
・,c-nt,G1□,G-,,3,...,G,,,
On the other hand, the strobe signal 1 from the drive strobe generator 3 is input to the IM, G-, . . . , C-, .
In the same way, strobe 2, strobe 3, etc. are input sequentially to N gates, and strobe n signals are input to the last gate (, 1, . . . , c-nN, respectively). has been input.Moreover, the drive'![
2, the drive voltage is input to the common connection terminal of the heat generating resistor elements.

In this parallel thermal head drive circuit, the fourth
As shown in the figure, when a start signal is input to the drive strobe generator 3, the drive strobe generator 3 sequentially outputs time-sequential strobe signals of strobe 1, strobe 2, . . . strobe n, and on the other hand, Data D-1
1..., D-7, are input at the same time, first the strobe 1 signal is input to the gates G-,...
, at the timing when input to G-IN, data D-1,
..., among D-I N, only the signal printed in black is "1"
is input, the corresponding R-91,
..., the heating resistor element of R-I N is energized and a thermal printing operation is performed, and then the corresponding black printing is performed by inputting the strobe signals of strobe 2, ..., strobe n, and finally, the strobe G-111 with n signal
,...G-nN gates are driven, and the heating resistor element R
-71, . . . , R-nN are printed.

(c) Problem to be solved by the invention Simultaneous printing of parallel thermal head, that is, N is
Normally, the number of resistors is 100 to 400, and these heating resistive elements are energized and driven to print at the same time. The higher the black ratio of the printed figure (the ratio of the number of heating resistors that are in the "ON" state to the whole), the thicker the drive current (black ratio 100
%, that is, all rONJ is 5 amperes, and if the black ratio is 0%, it is naturally O amperes). Conventionally, a drive power source 2 is provided that can supply a maximum current of, for example, 5 amperes. However, since the average black ratio was less than 5%, there was a problem in that the power supply capacity was wasted most of the time.

In this way, it is wasteful in terms of cost and space to prepare a drive power source with a capacity 20 times greater than that required for the thermal head. low cost,
The aim is to provide a practical thermal printing drive system that takes up a small space.

(d) Means and operation for solving the problem The thermal printing drive method of the present invention selectively inputs print data to each heating resistor element of a thermal head in which a large number of heating resistive elements are arranged in a row, In a thermal printing device that performs printing by simultaneously energizing heating resistive elements to which printing data has been inputted from a driving power source at the arrival of time-sequential printing timing, it is detected that the voltage of the driving power source has decreased to a predetermined value or less. The present invention is characterized in that it includes a voltage drop detection means, and when the voltage drop detection means detects that the power supply voltage has dropped below a predetermined value, the next printing timing is delayed until the power supply voltage is recovered.

Therefore, in the thermal printing drive method of the present invention, when the black ratio is low in the current printing, the current flowing through each heating resistor element is smaller than the drive power supply, so if the voltage drop of the power supply is small, the next The timing moves to the next thermal printing operation, but if the black ratio is large and the drive current is large, the voltage of the drive power supply will naturally drop significantly, and if the voltage falls below the predetermined voltage value, the current will further increase after this printing is completed. When the current stops, the next printing timing is delayed until the voltage is restored. Therefore, by setting the timing time from this thermal printing timing to the next printing timing to be longer as the voltage drop increases, that is, as the black printing ratio increases, the parallel thermal head can be operated normally with a smaller capacity power supply than before. Can be printed.

(e) Examples Hereinafter, the present invention will be explained in more detail with reference to Examples.

FIG. 1 is a circuit diagram showing a drive circuit for a parallel thermal head according to an embodiment of the present invention.

In the figure, the connections of 9B of the parallel thermal head 1 are the same as those shown in FIG. Just drive power supply 2
is designed to supply a current of 0.25A, and the drive power supply 2
The power supply from the parallel thermal head 1 is connected to the common terminal of each heat generating resistor element, and is also connected to one input terminal of the comparator 4, while the power supply from the comparator 4 is connected to the reference voltage of the reference voltage setting device 5. 3 is input.

The comparator 4 is configured such that the supply voltage of the drive power source 2 is set to a reference voltage setter 5.
When the voltage drops below the reference voltage Vs, it outputs a high level output and inputs it to the drive strobe generator 3, and when the signal from the comparator 4 changes from high to low, the signal from the drive strobe generator 3 It is configured so that it increments by one.

Therefore, when the drive strobe generator 3 receives the start signal, it first outputs the strobe 1 signal, and then
Next, the strobe 2 signal is output in synchronization with the time when the output of the comparator 4 falls from high to low.

In this embodiment circuit, as shown in FIG. 2, the output from the drive power supply 2, that is, the drive voltage, varies depending on the black ratio of the parallel thermal head 1 at each print timing. ! The pressure is different. In other words, when the black ratio is large, the voltage drop is large, and the power supply voltage of the drive power supply 2 is therefore reduced.On the other hand, when the black ratio is small, the current flowing is small, so the voltage of the drive power supply 2 is reduced. There is little decline.

Therefore, the power supply voltage will vary depending on the black ratio.

Now, assuming that the voltage v3 shown by the broken line in FIG. Then, the strobe 1 signal is input to the parallel thermal head 1 in response to this, current flows through the corresponding heating resistor element in accordance with the black data, and the drive power source 2
A current is applied and a printing operation is performed. In this case, as shown in the timing following the first start signal in Figure 2, when the black ratio at the first printing timing is high, the drive power supply voltage is large and drops beyond the reference voltage ■1, so the recovery In this case, it takes time to
After a predetermined period of time, the next strobe 2 signal is generated after a relatively long period of time.

If the black ratio happens to be low in the printing operation of the next strobe 2 signal, the strobe 3 signal is generated and the next printing is performed without waiting too long for the next strobe signal. Next, for example, if the black ratio is medium in printing with strobe 3, the printing operation starts after a medium period of time when the fourth strobe signal is applied manually.

In this way, this drive circuit detects a voltage drop by comparing the voltage of the drive power supply with the reference voltage V, and if it is extremely lower than the reference voltage V, that is, if the voltage drop is large, recovery is performed. With a margin of time, that is, a delay time,
Outputs the next printing timing, that is, the strobe signal,
On the other hand, if the black ratio is low and there is not much voltage drop,
Move to the next print with a relatively small delay time.

In this way, if the black ratio is small, printing can be continued without much delay time, and the voltage drop is usually small, so the power supply has plenty of leeway. There's no need.

Only when the current is large, that is, when the black ratio is high, it is only necessary to recover after a period of time, so the drive power source 2 can have a very small capacity.

In the above embodiment, a comparator is used to detect the voltage drop of the drive amount R2, but the voltage drop of the drive amount R2 is detected without using a comparator.
The black ratio of the input data is checked at the stage of serial shifting, and if the black ratio is greater than a predetermined value, the strobe signal of the drive strobe generator is activated according to the count value of the black ratio data. The occurrence of this may be delayed.

(F) Effects of the Invention According to the present invention, a drop in the voltage of the drive power source is detected and the next printing timing is determined based on the degree of recovery corresponding to the degree of drop, so that the black ratio is relatively low. During small, normal printing, printing can be continued at the specified printing timing even if the drive power supply is small, and if the black ratio happens to be large and a large current flows, The voltage drop is small, and even if it becomes large, it can be counteracted by waiting that amount of time and delaying the printing timing. Therefore, the capacity of the drive power supply can be reduced on average, resulting in lower cost and smaller size of the entire device. It has the advantage of being able to be used in a variety of ways.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a drive circuit for a parallel thermal head according to an embodiment of the present invention, FIG. 2 is a signal waveform time chart for explaining the operation of the drive circuit of the embodiment, and FIG. FIG. 4 is a diagram showing a conventional thermal head drive circuit, and FIG. 4 is a signal waveform diagram for explaining the operation of the conventional drive circuit. 1: Parallel thermal 2: Drive power supply, 3: Drive strobe generator, 4: Comparator, 5: Reference voltage setter. Patent issuer Shimadzu Corporation Agent Patent attorney Shigenobu Nakamura

Claims (1)

[Claims] (1) Print data is selectively input to each heat generating resistor element of a thermal head in which a large number of heat generating resistive elements are arranged in a row, and the print data is input from the drive power source when the time-sequential printing timing arrives. A thermal printing device that performs printing by energizing resistive elements all at once, comprising a voltage drop detection means for detecting that the voltage of the driving power source has decreased below a predetermined value, and the voltage drop detection means detects when the power supply voltage has decreased to a predetermined value. A thermal printing drive method that is characterized by delaying the next printing timing until the power supply voltage recovers after detecting that the voltage has dropped below the specified value.