JPS59138478A - Controlling method for thermal printer - Google Patents

Abstract

PURPOSE:To appropriately detect a driving voltage, appropriately control printed density with a small consumption of electric power without lowering printing speed and obtain a high print quality, by providing a reference voltage with a variation corresponding to that of the driving voltage. CONSTITUTION:A reference voltage forming circuit 7 adds the variation of the driving voltage Vp (e.g., by impressing it onto an adding circuit) to a fixed voltage VDD impressed from a regulator 2, and supplies the resultant voltage to a driving voltage detecting circuit 8 as a reference voltage VREF. Accordingly, when using as a power source 1 a small-type AC adapter of the type in which an AC ripple is incorporated into the driving voltage Vp, the reference voltage VREF is varied in the same manner as the driving voltage Vp corresponding to the ripple of the driving voltage Vp. Therefore, in the circuit 8, the potential difference between the reference voltage VREF and the driving voltage Vp is constantly fixed. Accordingly, since the value of the driving voltage Vp detected becomes costant irrespectively of the detecting timing with respect to the ripple, a heat pulse width for a thermal head determined on the basis of the detected value, namely, printed density becomes constant irrespectively of the detecting timing.

Description

TECHNICAL FIELD The present invention relates to a thermal printer control method, and more particularly to a thermal printer control method that detects the drive voltage of a print head of a thermal printer and changes the heat pulse width of the head in accordance with the detection result.

Conventional thermal printers are widely used as output printing devices for various electronic devices, and are equipped with a thermal head having a plurality of heating elements.According to a printing command, a driving voltage is applied to these heating elements to generate heat. Printing is performed on printing paper on thermal paper or via thermal transfer tape.

In this case, the print density depends on the driving voltage level and its application time (
(hereinafter referred to as heat pulse width). That is,
The higher the drive voltage, the darker the print density, and the longer the heat pulse width, the darker the print density. Furthermore, if the drive voltage is extremely high and the heat pulse width is long, the head may burn out.

Therefore, in devices that use a thermal printer as an output device and whose driving voltage changes, for example electronic devices such as calculators that use batteries or small AC adapters as the driving voltage power source, the print density may change due to fluctuations in the driving voltage. To prevent variations, the heat pulse width is controlled according to the drive voltage level.

The conventional control method is to detect the drive voltage by comparing the drive voltage with a certain reference voltage once per printing line or once per line, and if the detected drive voltage is high, the heat pulse width is This was a control method that determined the length of the curve, and the shorter it was if it was lower.

However, according to such a control method, in the case of a device that uses a small AC adapter as a power source for the drive voltage, the print density will vary.

This is because in such a case, as shown in Figure 1, AC voltage fluctuations of 50 Hz or 5 Q Hz, so-called ripples, are added to the drive voltage Vp, whereas when compared with a constant reference voltage VREF, This is because since detection is performed, the detected value differs depending on the timing of detection.

For example, in Fig. 1, the driving voltage Vp is the minimum value Vpm.
If the detection is performed at the time of in and the heat pulse width is set to be long corresponding to the minimum value Vpmin, the print will become dark when the drive voltage Vp is around the maximum value Vpmax during actual printing. Moreover, in the opposite case, the printing becomes faint.

In order to eliminate the above-mentioned drawbacks, a conventional control method has been proposed in which the interval at which the drive voltage Vp is detected is reduced to absorb the influence of ripples. However, this control method has the disadvantage that the number of detections is large, resulting in a decrease in printing speed and an increase in power consumption.

Furthermore, as another method for eliminating the influence of ripples, a control method has been proposed in which the drive voltage Vp is detected multiple times and the heat pulse width is determined based on the average value of the detected values. However, even with this method, detection is performed multiple times to determine the average value, resulting in a large number of detections.
This results in a decrease in printing speed and an increase in power consumption.

Purpose The present invention has been made in view of the above points, and it is possible to achieve impressive print density without reducing printing speed and with low power consumption even when using a power supply with alternating current ripples in the supplied drive voltage. The purpose of the present invention is to provide a thermal printer control method that can be obtained.

EXAMPLES The present invention will be described in detail below based on examples shown in the drawings. FIG. 2 shows the main structure of a link electronic desk calculator (hereinafter abbreviated as calculator) to which the method of the present invention is applied.

Only the parts relevant to the present invention are shown here.

The reference numeral 1 is the power source for the calculator, which in this case is either a dry battery or an AC adapter. A regulator 2 is connected to the power supply 1 and supplies a constant voltage VDD to the LSI 3 from the wide input voltage of the power supply.

The LSI 3 controls the entire operation of the calculator including the printing operation, and a thermal head driver 6 for driving the thermal head 5 of the thermal printer 4 is connected to the LSI 3. The thermal head driver 6 is also connected to the power source 1, and its driving voltage Vp is applied thereto. In accordance with the thermal head drive signal from the LSI 3, the thermal head driver 6 applies a drive voltage Vp to the thermal head 5. Thereby, the thermal paint 6 is heated and printing is performed.

On the other hand, what is indicated by the reference numeral 7 is a reference voltage generation circuit,
The driving voltage V is added to the voltage VDD applied from the regulator 2.
P fluctuation is added to the LSI using it as the reference voltage
The voltage is supplied to the drive voltage detection circuit 8 in 3.

The drive voltage detection circuit 8 converts the drive voltage Vp into a reference voltage VRKF.
This circuit provides a detection output to the LSI 3, and the LSI 3 controls the heat pulse width of the thermal head 5 according to this output.

The configuration of the drive voltage detection circuit 8 is as shown in FIG. At the time of detection, the driving voltage Vp of the power supply 1 is applied to one input terminal of each of comparators 1 to KIn, and the reference voltage VREF supplied from the reference voltage generation circuit 7 is applied to the other input terminal of the comparator. After the voltage is divided through the gates 01 to Gm, it is applied sequentially through the gates 01 to Gm. Drive voltage Vp and divided reference voltage VRKF
are sequentially compared by comparators 1 to h, and the LSI 3 detects the drive voltage Vp based on the output of the comparator K1-Km.

The LSI 3 determines the heat pulse width of the thermal head 5 according to the detection result.

In the above configuration, the reference voltage generation circuit 7 supplies the applied voltage VRKF from the regulator 2 to the drive voltage detection circuit 8 as described above. Therefore, if a small AC adapter with an AC ripple on the drive voltage Vp is used as the power supply 1, the reference voltage VREF will fluctuate in the same way as the drive voltage Vp in response to the ripple of the drive voltage Vp, as shown in Figure 4. do.

Therefore, in the drive voltage detection circuit 8, the reference voltage VREF
The potential difference between the drive voltage Vp and the drive voltage Vp is always constant. Since the comparator Kl-Km outputs by comparing the potential difference,
The detected value is constant regardless of the timing of detection with respect to ripple.

For example, in FIG. 4, whether the drive voltage is detected at the maximum value Vpmax or the minimum value Vp min, the potential difference between the drive voltage Vp and the reference voltage VRKF at the inner point is are the same, so the detected values of the driving voltages Vp are the same.

Since the value of the drive voltage Vp detected in this way is constant regardless of the timing of detection for ripples, the heat pulse width of the thermal head, that is, the print density determined from the detected value, is constant regardless of the timing of detection. .

As described above, according to the method of the present invention, the influence of ripples on the drive voltage can be eliminated in the detection of the drive voltage, so there is no need to detect the rise of the drive power source more times than necessary.

In the above embodiments, the method of the present invention was applied to a calculator, but it goes without saying that the method of the present invention can be widely applied to other devices equipped with a thermal printer.

Effects As is clear from the above explanation, the method of the present invention applies fluctuations corresponding to fluctuations in the driving voltage to the reference voltage for detecting the driving voltage of levers and thermal printers, and the driving voltage is determined by comparison with the reference voltage. Since the configuration is configured to detect the heat pulse width of the head of the thermal printer according to the detection result, the drive voltage can be appropriately detected regardless of the timing of detection with respect to fluctuations in the drive voltage. Therefore, even if the drive voltage of the thermal printer contains alternating current ripples, it is possible to eliminate the influence of ripples on detection, and there is no need to perform detection multiple times, so printing speed does not decrease and consumption is small. It is possible to appropriately control print density using electricity and obtain high print quality.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the state of the drive voltage and reference voltage in drive voltage detection using the conventional method, FIG. 2 is a block diagram showing the configuration of a calculator to which the method of the present invention is applied, and FIG.
FIG. 4 is a circuit diagram showing the configuration of the drive voltage detection circuit shown in the figure, and FIG. 4 is a diagram showing the states of the drive voltage and reference voltage in the detection of the drive voltage by the method of the present invention. ]...Power supply 2...Regulator 3
...LSI 4...Thermal printer 5...Thermal head 7...Reference voltage creation circuit 8...Drive voltage detection circuit Vp...Drive voltage VREF...Reference voltage Figure 1 Special 1978-138478 (4) Figure 3

Claims (1)

[Claims] A thermal printer control method in which a driving voltage of a print head of a thermal printer is detected by comparing it with a reference voltage, and a heat pulse width of the head is changed according to the detection result, wherein a fluctuation corresponding to a fluctuation in the driving voltage is applied to the reference voltage. A thermal printer control method characterized in that: