JP3132769B2 - Thermal printer controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer control device for performing printing by energizing a thermal head based on print data.

[0002]

2. Description of the Related Art Generally, a thermal printer is suitable as a print output device of a portable electronic device because it can print a high-definition dot pattern and has a simple mechanism.

A portable electronic device, unlike a stationary electronic device using, for example, a commercial power supply, must operate using a battery as a power supply, and has a large variation in environmental temperature during use. Therefore, the thermal printer control device must be designed according to the usage form and purpose of the portable electronic device. That is, in the thermal printer, the print density greatly changes depending on the energy applied to each heating element of the thermal head and the ambient temperature. Therefore, conventionally, the energy applied to the thermal head is controlled by controlling the power supply time width of each heating element, the power supply time width is controlled according to the battery voltage, and the ambient temperature is detected to correct the power supply time width. Like that.

[0004]

When designing a portable electronic device, the type and capacity of the battery are designed according to the load characteristics. For example, the capacity of the battery is determined by the product of the target use time and the load current. However, the load current is not always constant, and the capacity varies depending on the discharge rate of the battery. Therefore, in the case of a secondary battery, it may be necessary to charge the battery before it reaches the design use time. In particular, in the case of a line thermal printer, the load current increases as the printing rate (selectivity per line) of the heating element provided on the thermal head increases.

[0005] For this reason, if printing with a high printing rate is performed in a state where the battery capacity is reduced and the internal resistance is increased, the power supply voltage is greatly reduced. Will be suspended. Further, for example, when a secondary battery such as a nickel-cadmium battery is used as a power supply, even when the battery has a relatively large remaining capacity,
For example, when all the heating elements of the thermal head are driven at the same time, the power supply voltage drops rapidly, and a low voltage warning is issued. In such a usage method where charging is performed in a state where the remaining capacity is relatively large, shallow charging / shallow discharging will be repeated, and the battery capacity will decrease due to the so-called memory effect, and the usable time will increase. Will be shorter.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal printer control device capable of using a battery having a limited capacity to extend the operation time as much as possible.

[0007]

According to the present invention, there is provided a register for inputting print data for each heating element of a line thermal head, and a heating element to be energized according to the state of each bit output of the register. In a thermal printer control device having a heating element driving circuit driven as a group, a gate circuit for each group for selectively outputting the contents of the register by grouping a plurality of bits and a gate circuit for each group according to the number of print divisions. divisionally selects a dividing print control means for printing one line, a voltage measuring means for measuring the applied voltage or the battery voltage to the common electrode side of the line Thermal <br/> heads or others, the voltage measurement Measuring power by means
Printing is the ratio of pressure and the number of selected dots per line
And when the measured voltage is lower than a predetermined value,
The print division number increases, and the print ratio is higher than a predetermined value.
Print division so that the number of print divisions increases
And a division number switching means for switching the number.

[0008]

In the thermal printer control device according to the present invention, the group-by-group gate circuit groups the contents of the register for inputting the print data into a plurality of bits and selectively outputs the result. The divided print control means selects one of the gate circuits for each group in a time-division manner according to the number of print divisions, and prints one line. The voltage measuring means measures the voltage applied to the common electrode side of the thermal head or the battery voltage, and switches the number of divisions.
Means for dividing the print when the measured voltage is lower than a predetermined value;
When the number increases and the printing rate becomes higher than a predetermined value,
The print division number is switched so that the print division number increases.
Therefore, as the voltage applied to the common electrode of the thermal head and the battery voltage decrease, the number of print divisions increases, and the heating elements for one line are divided into a plurality of groups, and printing is performed in a time-division manner. Therefore, the maximum number of heating elements that are simultaneously energized is reduced, and when the voltage applied to the common electrode side of the thermal head or the battery voltage is reduced, the load current for the battery is limited, and the voltage drop is suppressed. As a result, printing control is performed within a range in which the power supply voltage does not fall below the allowable lower limit even when the remaining capacity is low. Conversely, when the remaining capacity is sufficient and the power supply voltage is high, the number of print divisions decreases, and for example, the selected heating elements for one line are printed simultaneously,
High-speed printing becomes possible. However, even in such a state,
The ratio of the number of selected drive dots per line (printing rate)
If it is higher than the fixed value, the number of print divisions increases and the
Is not too high, and the battery discharge rate is reduced.
And its life is extended.

[0009]

FIG. 1 is a circuit diagram showing a configuration of a thermal printer control device according to an embodiment of the present invention. In FIG. 1, a CPU 1 includes a ROM, a RAM, and an A / D converter, and performs thermal print control. The shift register 2 serially inputs print data from the CPU 1. The latch register 3 receives the latch signal and latches the contents of the shift register 2. The gate circuit 4 outputs a strobe signal (S
TB1 to STB4), the driving transistor 5 is selectively driven according to the contents of the latch register 3.
The number shown in the gate symbol of the gate circuit 4 is the number of the corresponding heating element to be selected. In the case of the connection shown in FIG.
When the strobe signal STB1 is valid, among the print data of one line set in the latch register 3, the heating elements of the heating element numbers 1 to 128 are selectively selected according to the bit data of the heating element numbers 1 to 128. Is energized. When the strobe signal STB2 is valid, among the print data for one line set in the latch register 3, the heating elements of the heating element numbers 129 to 192 are selectively selected according to the bit data of the heating element numbers 129 to 192. Is energized. Similarly, when the strobe signal STB3 is valid, the heating elements of the heating element numbers 193 to 256 are selectively energized, and when the strobe signal STB4 is valid, the heating element number 2 is selected.
The heating elements 57 to 384 are selectively energized. In FIG. 1, reference numeral 6 denotes a heating element that constitutes each dot of the line thermal head, and is composed of a heating element for 384 dots.
VP is a power supply voltage applied to the common electrode side of the heating element 6 of the thermal head. For example, a battery voltage is directly applied via a p-channel FET. The resistors R1 and R2 divide the head drive voltage VP at a predetermined division ratio. The CPU 1 reads the divided voltage value from the analog input port A1 and measures the head drive voltage VP.

Next, FIGS. 2 to 5 show the processing procedure of the CPU as flowcharts, and FIG. 6 shows a timing chart of each output signal.

FIG. 2 and FIG. 3 show an overall processing procedure for performing print control in response to externally applied data such as a master CPU. The CPU first inputs a code from a master CPU (not shown), but stores a character code in an internal register (n1 → n2 → n3 →) until a CR (carriage return) code or an end code is input.
n4 → n1 ...). After receiving the character code for one line and receiving the CR code, the line number LN is set to the initial value 0 (n5). The line number LN is a counter indicating which line of a certain character is to be printed. Thereafter, the print data for one line is decoded by the character code string for one line and the line number LN (n6). Then, the printing rate (the ratio of the selected dots) of the line is counted (n7). And the decoded 1
The data for the line is transferred to the shift register 2 shown in FIG. 1, and is latched by the latch register 3 after the transfer (n8 → n).
9). Then, the process proceeds to the process shown in FIG. In FIG. 3, D
Is the number of print divisions, and the head drive voltage V
The value of D is determined by P. If the predetermined division number D is 1 (collective printing), it is determined whether the printing rate exceeds 50% (n10 → n11). 50
If it is less than%, one line is simultaneously printed by the processing described later (n12). Thereafter, the paper feed motor for the printing paper is driven by a predetermined number of steps to convey the printing paper by one line (n13). Then, the line number LN is incremented, the LN-th print data is obtained again from the character code string for one line and the line number LN, and the same processing is performed (n14 → n15 → n6 →...).
Even if the printing division number D is 1, the printing rate of the line is 5
If it exceeds 0%, two-part printing is forcibly performed (n
11 → n17). If the number D of print divisions is 2, undivided printing is performed unconditionally (n16 → n17). If the print division number D is 3, three-part print is performed unconditionally (n18 → n
19). If the print division number D is 4, a low voltage warning is issued and the printing process is interrupted (n18 → n20 → EN).
D). When printing of one line is completed normally, the character code string of the next line is received (n14 → n1 → n2 → n3).
→ n4 → n1 ...). Thereafter, an end code is received, and a series of printing processes is ended (n3 → END).

FIG. 4 shows a specific processing procedure of step n12 in FIG. First, the strobe signals STB1, STB2,
All of 3 and 4 are set to “H” (valid), and a strobe signal is applied to the gate circuit 4 shown in FIG. As a result, all the contents of the latch register 3 are simultaneously supplied to the drive transistor 5 (n30). In this state, the head drive voltage VP is measured (n31). After that, the print division number of the next line is determined according to the VP. For example, VP is 4.4V
If this is the case, 1 is set for the print division number D (n32 → n
33). Subsequently, the energization time is calculated based on the head drive voltage VP and the ambient temperature, and the energization time is set in a counter for counting the energization time (n37 → n38). Thereafter, the counter is started, and when the counter reaches a predetermined value and detects the end of the energization time, all of the strobe signals STB1, STB2, STB3, and ST4 are set to "L", and the energization of the heating element is ended (n39). → n40 → n41). If the head drive voltage VP is a value of 4.2 V or more and less than 4.4 V, 2 is set as the print division number D (n32 → n34). If the head drive voltage VP is 4.0 V or more and less than 4.2 V, the number D of print divisions is set to 3 (n32 → n35). If the head drive voltage VP is less than 4.0 V, the print division number D is set to 4 (n32 → n36). Therefore, if the value of D is 1, the next line is printed collectively, if D = 2, the next line is printed in two parts, and if D = 3, the next line is printed in three parts. If D = 4, a low voltage warning is issued and printing is interrupted when printing the next line.

FIG. 5 shows a processing procedure of step n17 in FIG. First, only the strobe signals STB1 and STB2 are set to "H" (n50). As a result, the heating element numbers 1 to 192 of the gate circuit 4 shown in FIG. In this state, the head drive voltage VP is measured (n51). After that, the print division number of the next line is determined according to the VP. For example, VP is 4.4V
If this is the case, 1 is set for the print division number D (n52 → n
53). If VP is not less than 4.2 V and less than 4.4 V, 2 is set as the print division number D (n52 → n54). If VP is equal to or higher than 4.0 V and lower than 4.2 V, 3 is set as the print division number D (n52 → n55). If VP is less than 4.0 V, 4 is set as the print division number D (n52 → n56).
Subsequently, the energizing time is calculated based on the head drive voltage VP and the ambient temperature, and the energizing time is set in a counter for counting the energizing time (n57 → n58). Thereafter, the counter is started. When the counter reaches a predetermined value and detects the end of the energization time, the strobe signal STB
By setting 1 and 2 to "L", the energization of the heating element is terminated (n59).
→ n60 → n61). Subsequently, the strobe signal STB3,
4 is set to "H" (n62). As a result, in the gate circuit 4 shown in FIG. 1, the heating elements of the heating element numbers 193 to 384, that is, the heating elements in the right half are selectively energized based on the contents of the latch register 3. . Then, the counter for counting the energization time is set to step n.
The energization time obtained in 57 is set (n63). afterwards,
The counter is started, and when the counter reaches a predetermined value and detects the end of the energization time, the strobe signal ST
B3 and 4 are set to "L" to terminate the energization of the heating element (n6
4 → n65 → n66).

The same applies to the three-part printing in step n19 shown in FIG. 3. The strobe signal STB1 is made valid to perform printing of the left one-third of one line, and then the strobe signals STB2 and 3 are made valid. Then, the center 1/3 of one line is printed, and the strobe signal 4 is made valid to print the right 1/3 of the line. Then, the head drive voltage VP may be measured during any printing (during energization), and the value of the print division number D may be set according to the measured voltage.

FIG. 6 is a diagram showing the timing of each signal output from the CPU. At time t1, transfer of one line of print data to the shift register 2 is started, and after outputting a latch signal, the strobe signal is output at t2. The signals STB1 to STB4 are all set to “H”. At t2 to t3, power is supplied to the selected heating element. In the case of two-segment printing, t5 to t
As shown in FIG. 7, first, during the period from t5 to t6, the heating element selected for the left half of one line is energized, and from t6 to t7.
During the period, the heating element selected for the right half of one line is energized. Also, in the case of three-division printing, first, as shown at t9 to t12, the left one-third of one line is
Power is supplied to the heating element selected for
During the period of 11, power is supplied to the heating element selected for the center 1/3 of one line, and during the period from t11 to t12, power is supplied to the heating element selected for the right 1/3 of the line.

Since the number of print divisions increases as the power supply voltage decreases, the printing rate per one print decreases as the power supply voltage decreases. For this reason, the voltage drop rate is reduced, and printing control can be performed without significantly lowering the power supply voltage even when using a battery with a small remaining capacity. In addition, even when the power supply voltage is high, if the printing rate is high, printing is forcibly performed in two parts, so that the discharge rate of the battery as the power source is suppressed, and the life of the battery can be maintained long.

[0017]

According to the thermal printer control apparatus of the present invention, even when printing the same contents, the current consumption is suppressed as the power supply voltage decreases, so that the voltage drop due to the internal resistance of the battery is reduced. The power supply voltage can be maintained at a certain level or higher, and long-term operation using a thermal printer can be performed. Further, when the battery capacity is still sufficient and the power supply voltage is high, the number of print divisions is small (for example, batch printing), so that high-speed printing can be performed. In addition, even in such a state,
If the ratio of the number of selected drive dots (printing ratio) is higher than a predetermined value,
In this case, the number of print divisions increases and the energizing current becomes too high.
Battery life, the battery's discharge rate is reduced,
Extend. When the thermal printer control device of the present invention is incorporated in an electronic device using a secondary battery as a power source, the secondary battery can be used until the secondary battery is discharged to a necessary and sufficient amount. Is performed, so-called memory effect is eliminated, the secondary battery can be always maintained in a good state, and the life of the secondary battery can be maintained long.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a thermal printer control device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a processing procedure of a main part of the thermal printer control device according to the embodiment of the present invention.

FIG. 3 is a flowchart showing a processing procedure of a main part of the thermal printer control device according to the embodiment of the present invention.

FIG. 4 is a flowchart illustrating a processing procedure of batch printing.

FIG. 5 is a flowchart illustrating a processing procedure for two-part printing.

FIG. 6 is a diagram showing timings of various signals output from a CPU.

[Explanation of symbols]

 4-gate circuit 6-heating element VP-head drive voltage STB1-STB4-strobe signal

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/35-2/37

Claims (1)

(57) [Claims] A register for inputting print data for each heating element of a line thermal head, and a heating element drive circuit for driving a heating element to be energized in accordance with the state of each bit output of the register with a battery as a power supply. A thermal printer controller comprising: a group-by-group gate circuit for grouping and selectively outputting the contents of the register for each of a plurality of bits; and Division print control means for printing lines , voltage measurement means for measuring the applied voltage or battery voltage to the common electrode side of the line thermal head, measurement voltage by the voltage measurement means,
Based on the print ratio, which is the ratio of the number of selected drive dots,
When the measured voltage is lower than a predetermined value, the number of print divisions increases.
And when the printing rate is higher than a predetermined value,
A thermal printer control device comprising: a division number switching unit that switches the print division number so as to increase the character division number .