JPH0474191B2 - - 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, but in the case of a multi-head, there are many heating elements, and driving them all at the same time is difficult 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, this alone will reduce the printing speed to a fraction of what it used to be.
Therefore, the number of divisions is changed 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 all the data for one row is transferred to the head in one data transfer, the power supply capacity is only 1/N of that when all the heating elements are driven at the same time, and the power supply capacity is no more than that. Capacity cannot be reduced.

The present invention aims to significantly reduce power supply capacity.

(Means for solving the problem) The present invention detects the average value of the number of loads simultaneously driven within one block over all blocks,
The pause time until the next block is driven is controlled according to the average value.

(Example) In FIG. 1, 1 is a thermal head, and in this example, 320 heating elements are provided as a load, and this is divided into five blocks. Tr to Tr are drive transistors, G to G are gate circuits, L ₁ to L ₅ are latch circuits that also store print data, SR ₁ to _{SR 5} are shift registers that store the next row's character data,
_V1 to _V5 are inverters. 2 is a CPU, 3 is an input/output control circuit, and 4 is a memory, which includes print data, the number of heating elements driven in one block, the average value of the number of loads driven simultaneously over all blocks, and the energization corresponding to this average value. Store the period (described later).
Numeral 5 is a multiplexer that serially generates print data, and 6 is a timer that measures the energization cycle. Reference numeral 7 denotes an energization signal generating circuit which always generates an energization signal having a constant width depending on the temperature of the head. 8 is a demultiplexer 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 print data "1") _M1 to _M5 is counted for each block and stored in the memory 4. On the other hand, the print data in shift registers SR ₁ to _{SR 5} are transferred to latch circuits L ₁ to L ₅ , respectively. Printing is performed using this print data as follows.

First, the average value of the number of driven heating elements over all blocks = (M ₁ +M ₂ +M ₃ +M ₄ +M ₅ )/5
is calculated and stored in the memory 4. In accordance with this average value, the energization cycle from the start of energization of one block to the start of energization of the next block is selected and read out from the memory 4.

Here, the setting of the average value and the energization cycle will be explained. In this example, the number of heating elements in one block is
There are 64 wires, and when the average value M is 0<≦32, the energization cycle is T, and when 33≦≦40, it is 1.25T, and 41≦48.
1.5T when , 1.75T when 49≦≦56, 57≦≦
It is set so that it becomes 2T when it is 64.

Now, if the average value is 41≦≦48,
An energization cycle of 1.5T is selected, set in timer 6, and timer 6 starts. At the same time, the energization signal generation circuit 7 generates an energization signal with a constant width t (depending on the temperature of the print head, it is set to be wide at low temperatures and narrow at high temperatures), and this is applied to the demultiplexer. 8 to the gate circuits G to G of the first block as shown in FIG. ₂ , and the heating elements of the first block are driven.
When a time period of 1.5T has elapsed since the start of energization, the average value from the memory 4 is set in the timer 6 again. When the timer 6 starts, an energizing signal is generated, which is sent to the gate circuits G to G of the second block by the demultiplexer 8 as shown in _FIG.
The heating element shown in the block of FIG. 2 is driven.

Thereafter, in exactly the same manner, the heating elements of the third, fourth, and fifth blocks are driven at an energization period of 1.5T.

When the average value M of the next row is, for example, 0<≦32, the energization cycle is T, and each block is driven at the energization cycle T as shown in FIG.

Printing is performed as described above,
The energization time is always constant across all blocks, and the pause time until the next block is controlled according to the average value, so the average current consumption can be kept low and the power supply capacity can be reduced. be.

By the way, although it was omitted in the above explanation, while printing the first line, the print data of the second line is transferred to the shift register.
This is to write to SR ₁ to _{SR 5} , 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 print data of the second block in the second row is read out, and this data is transferred to shift register _SR5 from the previous shift register.
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. At this time, an average value is calculated and stored in the memory 4.

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 time 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 average value of the number of loads simultaneously driven in one block over all blocks is detected, the driving time of one block is constant, and the rest time until the next block is driven is determined. is set to a constant value according to the above average value over all blocks, and the above rest time is made longer as the above average value becomes larger. Therefore, the average current can be reduced, the power supply capacity can be reduced, and the power supply is lightweight. and cost reduction. Moreover, even if the driven load is concentrated in one block, if the overall average value is small, the energization period of all blocks can be made small, and the driving speed will not be reduced. For example, in printers, it is rare for the average value to be 50% or more, so this is particularly effective.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are time charts for explaining the operation. 2...CPU, 3...I/O control circuit, 4...
Memory, 6... timer, 7... energization signal generation circuit.

Claims (1)

[Scope of Claims] 1. In 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-division manner, the average number of loads simultaneously driven within one block over all blocks. The driving time of the load in each block is constant, and the rest time until driving the next block is constant over all blocks, and is a value corresponding to the above average value. , A method for driving a load, characterized in that the larger the average value is, the longer the pause time is.