JPH047713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thermal recording device that can record at a stable density even when using a commercial power source with large voltage fluctuations.

Conventional configuration and its problems In a thermal recording device that uses a thermal head in which a plurality of heating resistive elements are arranged to apply electricity in accordance with image information to color a thermal recording medium, the recording device is connected to a commercial power supply. By using it as an input, an inexpensive recording device can be constructed. In this case, the voltage of the commercial power source is stepped down by a transformer, rectified by a diode, and smoothed by a capacitor and used as the input to the recording device, but voltage fluctuations occur due to changes in the load, and the recording voltage applied to the heating resistor element also fluctuates. In order to optimize the recording density, optimization control becomes necessary.

FIG. 1 is a diagram showing the configuration of a conventional thermosensitive recording device. 1 is a transformer for commercial power supply, 2 is a diode that rectifies the output of transformer 1 to make it a pulsating current TV, 3 is a capacitor that smoothes the pulsating current TV and makes it a recording voltage RV.
Reference numeral 4 indicates a plurality of heat generating resistive elements arranged in the thermal head; 5 indicates a drive circuit which corresponds one-to-one with the heat generating resistor element 4 and supplies current to the heat generating resistor element 4; and 6 indicates a drive circuit which corresponds one-to-one with the drive circuit 5. 5 is a gate circuit that operates; 7 is a shift register that converts the serial image signal PIX input from the terminal 13 into parallel and outputs it to the gate circuit 6; 8 is a shift register that opens the gate circuit 6 according to the content of the image signal PIX. Output recording pulse PLS
RS flip-flop; 9 is a squaring circuit that squares the recording voltage RV and converts it into electric power; 10 is an integrating circuit that calculates the electric power INT from the output of the squaring circuit 9; 11
12 is a level detection circuit that detects when the electric power INT reaches a certain level, and 12 is a recording start trigger.
TRG input terminal, 13 is the image signal PIX input terminal,
14 is an input terminal for the image signal and sample clock CLK.

FIG. 2 is a timing chart of a conventional thermosensitive recording device. The operation of a conventional thermal recording device will be explained with reference to FIGS. 1 and 2.

The serial image signal PIX input from terminal 13 is
It is written into the shift register 7 by the image signal sample clock CLK at the terminal 14. After the writing is completed, the image signal PIX is converted into parallel signals and outputted to one input side of the gate circuit 6. Next, a recording start trigger TRG is inputted from the terminal 12, and at the same time as the integrating circuit 10 is reset, the RS flip-flop 8 is set, the recording pulse PLS is turned on, and energization to the heating resistor element 4 is started.

The integration circuit 10 outputs the electric power INT to the level detection circuit 11 while the recording pulse PLS is on. When the electric power INT reaches a certain level, the level detection circuit 11 resets the RS flip-flop 8, turns off the recording pulse PLS, and stops energizing the heating resistor element 4.

However, as a result of experiments with the above-mentioned conventional thermosensitive recording device, the following has become clear.

In other words, in order to keep the recording density constant, as shown in Figure 3, when the power is small, such as below the power _P The effective power decreases, and the characteristic shown in line b is shown instead of line a, and the smaller the electric power is, the larger the amount of electric power must be supplied.

On the other hand, the recording power varies due to the use of a commercial power source as an input to the recording apparatus or due to variations in the resistance value of the heat generating resistor element 4 to be driven. For this reason, in conventional thermal recording devices designed on the premise of always recording with a constant amount of power, the amount of power is always kept constant as shown by straight line a in Figure 3, despite this power fluctuation. If the power P is less than ₀ , the recording density level will decrease.
This will cause variations in concentration.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned problems, and aims to provide a thermal recording device that can record at a stable density even when a commercial power source that causes voltage fluctuations is used as input to the recording device.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a drive circuit for energizing a plurality of heat-generating resistor elements, a means for calculating the amount of electric power to be supplied to the heat-generating resistor elements, and a drive circuit for energizing a plurality of heat-generating resistor elements. A means for detecting that the electric energy has reached a preset reference electric energy level, and a voltage corresponding to the electric power value that can produce the same recording density level when a certain amount of electric power is supplied as the reference voltage level. The device has a means for comparing the reference voltage with the recording voltage, and repeats the operation of energizing when the recording voltage is above the reference voltage level and not energizing when it is less than the reference voltage level, thereby setting the heating resistor element to the reference power level. It is designed so that the amount of electricity is supplied.

That is, the present invention constantly monitors a recording voltage range in which the recording density is constant with a constant amount of power, and when the recording voltage supplied from the power supply falls below the above voltage range, the power amount is calculated and recorded. This achieves the above objective by interrupting the generation of pulses.

DESCRIPTION OF EMBODIMENTS FIG. 4 is a block diagram of a thermal recording apparatus which is an embodiment of the present invention. In FIG. 4, 21 is a commercial power supply transformer, 22 is a diode that rectifies the output of the transformer 21 to make it into a pulsating current, 23 is a plurality of heating resistance elements arranged in a summer head, and 24 is a heating resistance element 24. A drive circuit 25 corresponds one-to-one with the drive circuit 24 and operates the drive circuit 24;
26 is a serial image signal PIX input from terminal 32
35 is a comparator circuit that turns on and outputs an output signal ENB when the recording voltage is higher than the reference voltage, and turns off when the recording voltage is less than the reference voltage. , 34 is the output signal of the comparison circuit 35
This gate circuit outputs the recording pulse P, which is the output of the RS flip-flop 27, to the gate circuit 25 as a recording pulse PLS when ENB is on. The reference voltage level of the comparator 35 is set to a voltage corresponding to a power value that produces the same recording density level when a certain amount of power is supplied.

28 is means for converting recording voltage into electric power, that is,
This is a voltage/power conversion circuit that converts the recording voltage RV into electric power, and operates only while the output signal ENB of the comparison circuit 35 is on.

Reference numeral 29 designates means for calculating the amount of power supplied to the heating resistor element, that is, an integrating circuit that integrates the power and calculates the amount of power, and is connected to the terminal 31.
It is reset when the recording start trigger TRG is input from .

Reference numeral 30 denotes means for detecting that the amount of supplied power has reached a preset reference power amount level, that is, a level detection circuit, and a signal is output to the RS flip-flop 27.

Reference numeral 35 denotes means for setting, as a reference voltage level, a voltage corresponding to a power value that can produce color at the same recording density level when the same amount of electric power is supplied, and comparing it with the recording voltage, that is, a comparison circuit. Resistor 36a,
Input the reference voltage level V _nio obtained by dividing the power supply voltage V _cc applied to 36b and the recording voltage RV,
Outputs a recording enable signal ENB that turns on when the recording voltage RV is equal to or higher than the reference voltage level V _nio . The reference voltage level is set to a voltage corresponding to a power value that can produce the same recording density when the same amount of power is supplied to the heating resistive element 23.

31 is the input terminal of the recording start trigger TRG, 32
3 is an input terminal for the image signal PIX, and 33 is an input terminal for the image signal sample clock CLK.

FIG. 5 is a timing chart of the thermal recording apparatus of this embodiment. The operation of the thermal recording apparatus of this embodiment will be explained using FIGS. 4 and 5.

The commercial power supply voltage is converted and supplied as a recording voltage RV to the heating resistance element 23, the comparison circuit 35, and the voltage/power conversion circuit 28.

The serial image signal PIX input from terminal 32 is the image signal sample clock input from terminal 33.
CLK to the shift register 26.
The image signal PIX after writing is converted into parallel,
It is output to one input side of the gate circuit 25. Next, the recording start trigger TRG is input from the terminal 31, and at the same time the integrating circuit 29 is reset, the RS
Set the flip-flop 27 and write the recording pulse P.
Turn on. When the recording valid interval signal ENB and the recording pulse P are both on, the recording pulse PLS is output from the gate circuit 34 and the heating resistor element 23
is energized. On the other hand, the recording valid section signal ENB,
Alternatively, when the recording pulse P is off, the heating resistor element 23 is not energized. Then, until the power supply to the heating resistor element 23 reaches the reference power level set by the level detection circuit 30,
The above energization is repeatedly turned on and off. When the reference power level is reached, the RS flip-flop 27 is reset, the recording pulse PLS is turned off, and the current supply is stopped.

Note that, although the explanation is omitted in this embodiment, the same effects as the present invention can be obtained in the following items as well.

(1) When recording voltage is digitized and processed using an A/D converter.

(2) When setting the reference voltage level using a switch by making the voltage dividing resistor variable or by digitizing the comparator circuit.

(3) When the output of the shift register is stored in a single latch.

(4) When the heating resistor element is divided into multiple blocks and recorded in block units.

(5) When using half-wave rectification instead of full-wave rectification for the recording device input.

Effects of the Invention According to the present invention, there is an effect that even if a power source in which voltage fluctuations easily occur is input, recording can be performed at a constant density without reducing the recording density level.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a conventional thermal recording device, Fig. 2 is a timing chart of a conventional thermal recording device, Fig. 3 is a characteristic diagram of recording power and supplied power amount when recording density is constant, and Fig. 4 is FIG. 5 is a configuration diagram of a heat-sensitive recording device showing an embodiment of the present invention, and FIG. 5 is a timing chart of the heat-sensitive recording device showing an embodiment of the present invention. 23...Heating resistance element, 24...Drive circuit, 2
8... Voltage/power conversion circuit, 29... Integrating circuit,
30...Level detection circuit.

Claims (1)

[Claims] 1. A drive circuit for energizing a plurality of heating resistor elements, a conversion means for converting recording voltage into electric power,
a calculation means that inputs the output from the conversion means and calculates the amount of power supplied to the heat generating resistor element from the electric power; and a reference power level at which the output from the calculation means is input and the amount of power supplied is set in advance. level detection means for detecting that the amount of power supplied reaches a reference power amount level and stopping energization to the heating resistor element when the amount of power supplied reaches a reference power amount level; a comparison means for setting a voltage corresponding to a power value capable of coloring the density level as a reference voltage level and comparing the recording voltage and the reference voltage level; and a comparison means for determining that the recording voltage is equal to or higher than the reference voltage level. If the recording voltage is determined to be lower than the reference voltage level, the calculation of the electric energy is interrupted and the power supply to the heating resistor element is stopped. A thermosensitive recording device comprising a control means for controlling the temperature.