JPH0474190B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for driving a load such as a printer.

(Prior art) For example, in a thermal printer, current is passed through the heating elements of the thermal head to generate heat and print. However, in the case of a multi-head, there are many heating elements, and it is difficult to drive them all at the same time due to the power supply capacity. Because of this difficulty, the total number of heating elements is generally divided into fractions and time-division driving is performed several times.

However, if this is done alone, the printing speed will drop to a fraction of that, so there are some methods that change the number of divisions depending on the number of heating elements that are driven when printing one line. In other words, the number of divisions is increased when the number of heated heating elements to be driven is large, and the number of divisions is decreased when the number of driven heating elements is small, thereby preventing the printing speed from decreasing as much as possible.

(Problems to be Solved by the Invention) In the conventional device described above, time-division driving can be performed according to the number of heating elements to be driven, but the maximum division number N is determined by the configuration of the heating elements of the thermal head. However, if you want to transfer all the data for one row to the head in one data transfer, the power supply capacity will be only 1/N of the case when all the heating elements are driven at the same time. Power capacity cannot be reduced.

The present invention aims to significantly reduce power supply capacity.

(Means for Solving the Problems) The present invention detects the number of loads that are driven simultaneously for each block divided into a plurality of blocks, and calculates the pause time until driving the next block based on the number of loads that are driven simultaneously. The system is controlled accordingly.

(Example) In Fig. 1, 1 is a thermal head, and in this example, 320 heating elements H to H are provided as a load.
This is divided into five blocks. Tr～Tr
is a drive transistor, G to G are gate circuits, L ₁
~ _L5 is a latch circuit that also stores print data, _SR1 ~
_SR5 is a shift register that stores print data for the next line, and _V1 to _V5 are inverters. 2 is
CPU, 3 is an input/output control circuit, 4 is a memory, and the number of heating elements driven within one block of character data and the energization period according to this heating element (described later)
Remember. Numeral 5 is a multiplexer that serially generates print data, and 6 is a timer that measures the energization period for each block. 7 is an energization signal generation circuit that always generates an energization signal with a constant width. 8 is a del multiplexer that distributes the energization signal to each block.

Next, the operation will be explained. Print data for each line is stored in the memory 4, and the print data for the first line is first read out in response to a print command from the CPU 2. This print data is serially output from the multiplexer 5, and the data of the first to fifth blocks are written to shift registers _SR1 to _SR5 , respectively. When the print data is read out from the memory 4, the number of driven heating elements (the number of character data "1") is counted for each block and stored in the memory 4. On the other hand, the print data of shift registers SR ₁ to _{SR 2} is sent to each latch circuit.
Transferred to _L1 to _L5 . Printing is performed using this print data as follows.

First, the energization period from the start of energization of the first block to the start of energization of the second block is selected and read out from the memory 4 in accordance with the number _M1 of heating elements driven in the first block.

Here, the setting of the number of heat generating elements to be driven and the above-mentioned energization period will be explained.

In this example, the number of heating elements in one block is 64, and when the number of driven heating elements m is 0<m≦32, the energization period is T, and when 33≦m≦40, the energization period is T, and when 33≦m≦40, it is 1.25T, and when 41≦
1.5T when m≦48, 1.75T when 49≦m≦56, 57
It is set to be 2T when ≦m≦64.

Now, assuming that the number of heating elements driven in the first block is 32 or less, the energization period T is selected, this is set in the timer 6, and when the timer 6 starts, the energization signal generation circuit 7 outputs a constant width. t (however, it is set to be wide at low temperatures and narrow at high temperatures depending on the temperature of the print head), and this is sent to the gate circuit G of the first block by the demultiplexer 8.
- G as shown in FIG. 2, _SB1 , and the heating elements of the first block are driven. When time T has elapsed since the start of energization, the energization cycle is selected from the memory 4 in accordance with the number of heating elements driven in the second block. For example, the number of heating elements to be driven is 33≦
If m≦40, an energization cycle of 1.25T is selected and set in the timer 6. When the timer 6 starts, an energization signal is generated, which is supplied by the demultiplexer 8 to the gate circuits G to G of the second block as shown in FIG. _2SB2 , and the heating elements of the second block are driven. Ru. At this time, the number of heating elements driven is larger than that of the first block, and the energization period is longer, so the pause time until the start of energization of the third block is longer than that of the first block.

Thereafter, the third, fourth, and fifth blocks are driven in exactly the same manner, and for example, the number of heating elements driven in each is 40≦m≦48, 49≦m≦56.57≦m≦64.
Assuming that, the respective energization cycles are 1.5T, 1.75T, and 2T as shown in Figure 2.

One line of printing is performed as described above, but the energization time is the same for each block.
Since the pause time until the next block is controlled according to the number of heating elements driven, the average current within one energization cycle can be kept small regardless of the number of heating elements driven, and the power supply capacity can be reduced. It is something that can be done.

By the way, although omitted in the above explanation, the first
The print data of the second line is written into the shift registers SR ₁ to SR ₅ during printing of the line, and this operation will be explained. First, while printing of the first block is being performed, print data of the first block of the second row is read from the memory 4 and written to the shift register _SR5 . At this time, the number of driven heating elements is counted and stored in the memory 4. Next, while printing the second block, the second
The print data of the second block of the row is read out and transferred to shift register _SR5 .
The print data of the first block in _SR5 is written to shift register _SR4 . At this time, the number of heating elements driven in the second block is counted and stored in the memory 4.

Thereafter, the print data of the third, fourth, and fifth blocks of the second row are read out in the same manner, and the number of heating elements driven in each block is counted. In this way, the print data of the first to fifth blocks of the second row are written to the shift registers _SR1 to _SR5 , respectively.

In this way, each line is printed one after another.

In the above embodiment, the heating element is divided into five blocks, but the invention is not limited to this.

Further, the setting of the energization cycle can also be changed as necessary.

Furthermore, the present invention is not limited to thermal printers, but can also be applied to printers that divide the load into multiple blocks and drive them in a time-division manner, such as wire printers, discharge breakdown printers, inkjet printers, etc., or devices other than printers. It is something.

(Effects) According to the present invention, the number of loads driven simultaneously is detected for each block, and the pause time until driving the next block is made longer as the number of loads driven simultaneously increases. The average current in one energization cycle from the start of energization of one block to the start of energization of the next block can be kept small, the power supply capacity can be reduced, and weight and cost reductions can be achieved. Moreover, the time required to drive all blocks can be minimized.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention, and FIG. 2 is a time chart for explaining the operation. 2...CPC, 3...Input/output control circuit, 4...
Memory, 6... timer, 7... energization signal generation circuit.

Claims (1)

[Scope of Claims] 1. A load driving method in which a plurality of loads are divided into a plurality of blocks and each block is sequentially driven in a time-sharing manner, in which the number of loads to be simultaneously driven is detected for each block, The driving time of the load in each block is constant, and the rest time until driving the next block is controlled for each block according to the number of loads that are simultaneously driven. A method for driving a load, characterized in that the larger the number, the longer the pause time.