JP3439445B2 - Thermal head temperature measuring voltage detecting circuit and printer having thermal head temperature measuring voltage detecting circuit - 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 head temperature measuring voltage detecting circuit and a printer provided with the thermal head temperature measuring voltage detecting circuit, and more particularly to a thermal head using a reference voltage generating circuit and an operation amplifying circuit. The present invention relates to a temperature detection voltage detection circuit and a printer including the thermal head temperature measurement voltage detection circuit.

[0002]

2. Description of the Related Art Conventionally, in a circuit for observing the resistance value of a heating resistor of a thermal head and measuring the temperature of the heating resistor, a voltage divided by the resistance value of the heating resistor and the resistance value of a detection resistor is used. And, a reference voltage that is always kept constant is provided, the difference from that voltage is amplified by a differential amplifier circuit, and the magnitude of the output voltage determines the resistance value of the heating resistor.
The temperature of the heating resistor was measured.

Since the thermal head and the temperature measuring circuit section are mounted on different substrates, the power source of the heating resistor of the thermal head and the power source of the reference voltage generating circuit for generating the reference voltage are different power sources.

In a thermal head capable of measuring temperature, the heating resistor of the thermal head is divided into two or more blocks and controlled for each block, and printing is performed in one block while the temperature of the heating resistor is controlled in another block. Is measured. When white is printed and then black is printed, a large current suddenly flows through the heating resistor of the thermal head, so that the voltage applied to the heating resistor drops temporarily (instantaneously). Even at this moment, the temperature of the heating resistor is measured in another block, so if the same heating resistor power supply is used for the heating resistor, the detected voltage obtained for temperature measurement will also drop in voltage. Will be done.

[0005]

In the above-mentioned conventional voltage detection circuit for measuring the temperature of the thermal head, in order to improve the accuracy of temperature measurement of the heating resistor, the heating resistor power source is provided with a capacitor having a large capacity as much as possible. There has been a problem that it is necessary to take measures such as suppressing voltage fluctuations or dividing and supplying a heating resistor power source for each of a plurality of blocks in the thermal head.

Further, in the conventional circuit configuration, since the thermal head and the circuit for measuring the temperature of the heating resistor of the thermal head are mounted on different substrates, the path of the electric signal is inevitably long and noise from the outside is generated. Since it jumps in, problems such as deterioration in the temperature measurement accuracy of the heating resistor have occurred.

An object of the present invention is to realize the measurement of the temperature of the heating resistor with higher accuracy while saving the trouble of taking these measures.

[0008]

SUMMARY OF THE INVENTION A thermal head temperature measuring voltage detecting circuit of the present invention is a differential amplifier circuit for measuring the temperature of a heating resistor of a thermal head, and a reference voltage is supplied to the differential amplifier circuit. And a reference voltage generation circuit for
Control the thermal head by sharing the power supply to the reference voltage generation circuit with the power supply to the heating resistor.
Driver IC to be divided into two and one driver IC
Temperature measurement of the other driver IC
It is characterized by a fixed cycle . Thermal of the present invention
The voltage detection circuit for head temperature measurement is
Differential amplifier circuit for measuring temperature of thermal resistor and this difference
A reference voltage generation circuit that supplies the reference voltage to the dynamic amplification circuit.
And heats the power supplied to the reference voltage generation circuit.
The thermal head is shared with the power supply to the resistor.
The driver IC that controls the
Remains when two or more driver ICs are in a heating cycle
Characterized by using a driver IC for temperature measurement cycle
May be

The thermal head temperature measuring voltage detection circuit of the present invention may be mounted on the same substrate as the thermal head.

[0010]

[0011]

The printer of the present invention is a printer that prints images by heating a heating resistor of a thermal head with electric power, and a differential amplifier circuit for measuring the temperature of the heating resistor and a reference to the differential amplifier circuit. a thermal head temperature measurement voltage detection circuit having a reference voltage generating circuit for supplying a voltage to a power supply and a common power supply to the reference voltage generating circuit to the heating resistor, the Samaruhe
The driver IC that controls the driver is divided into two
The other driver I when the driver IC is in the heating cycle
It is characterized in that C is a temperature measurement cycle . The present invention
Printers, the heating resistor of the thermal head is applied with electric power.
In a printer that prints by heating,
Differential amplifier circuit for measuring temperature and this differential amplifier circuit
And a reference voltage generating circuit for supplying a reference voltage to the
Equipped with a voltage detection circuit for measuring the round head temperature,
Supply power to the pressure generating circuit to the heating resistor
A drive that shares the same power supply and controls the thermal head
The IC is divided into 3 or more, and 1 or 2 or more
When the Ivar IC is in the heating cycle, the remaining driver I
It may be characterized in that C is a temperature measurement cycle.

The printer of the present invention may be characterized in that the thermal head and the thermal head temperature measuring voltage detection circuit are mounted on the same substrate.

[0014]

[0015]

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of the first embodiment. Referring to FIG. 1, the first embodiment comprises a personal computer 1 and a printer 2. The personal computer 1 sends the print data to the printer, and the printer 2 prints out the print data.

The printer 2 includes a thermal head 11, a voltage detection circuit section 12, a power supply 13, a paper feed motor 14, a paper position detection sensor 15, an A / D converter 16 and a memory 1.
7, a thermal head controller 21, a paper feed controller 22, an external interface controller 23, and a memory controller 24.

The paper feed motor 14 carries the paper.
The paper position detection sensor 15 detects the position of the paper. A
The / D converter 16 A / D converts the output of the paper position detection sensor 15 in order to send it to the paper feed control unit 22. The thermal head controller 21 sends a thermal head drive signal to the thermal head 11. The paper feed control unit 22 sends a paper feed control signal to the paper feed motor 14. The external interface control unit 23 receives the print data from the personal computer 1. The memory control unit 24 controls the memory 17. Thermal head controller 21, paper feed controller 22, external interface controller 23, memory controller 24
Are controlled by the microcomputer.

FIG. 2 is a block diagram showing the configuration of the thermal head 11 and the voltage detection circuit section 12. The thermal head 11 has a thermistor characteristic in the heating resistor 110, and when power is applied from the heating resistor power source 33, the heating resistor 11
0 heats up. Thermal paper comes into contact with the heating resistor 110,
Alternatively, printing can be performed by contacting the printing paper with the ink ribbon sandwiched therebetween. This series of operations is the same as the printing method of the printer using the existing thermal head. The heating resistor power source 33 is supplied from the power source (13 in FIG. 1).

Further, a heating resistor 1 having thermistor characteristics
When 10 is heated and the temperature rises, the resistance value decreases. By measuring this change and measuring the temperature of the heating resistor 110, the power applied to the heating resistor 110 next can be controlled to obtain a higher quality print.

The voltage detection circuit section 12 is a circuit for measuring the temperature of the heating resistor 110, and includes a detection resistor 111, a buffer amplifier 112, a reference voltage generation circuit 113, and a differential amplifier 1.
It is composed of 14. The detection resistor 111 is the heating resistor 110.
Is connected in series to GND (ground). The partial pressure of the heating resistor 110 and the detection resistor 111 is the buffer amplifier 112.
It is connected to the. The detection resistor 111 has a fixed resistance value,
Since the resistance value of the heating resistor 110 changes depending on the temperature of the heating resistor 110, the voltage input to the buffer amplifier 112 changes depending on the temperature of the heating resistor 110 and has a constant potential at any temperature. Buffer amplifier 112
The potential input to is amplified and sent to the differential amplifier 114.

The reference voltage generating circuit 113 is a heating resistor 11
The same heating resistor power source as 0 is supplied, and a reference voltage is generated and supplied to the differential amplifier 114. The differential amplifier 114 compares the reference voltage supplied from the reference voltage generation circuit 113 with the potential sent from the buffer amplifier 112, and outputs the difference as a detection voltage. The resistance value of the heating resistor 110 can be observed, that is, the temperature of the heating resistor 110 can be measured depending on the magnitude of the detected voltage.

Next, the operation of the first embodiment will be described. FIG. 3 is a circuit diagram of the thermal head 11.

First, the operation of the thermal head 11 will be described with reference to the circuit diagram of FIG. 2n heating resistors 110 are arranged side by side in the thermal head 11, and one heating resistor corresponds to one dot when printed. All the heating resistors 110 are controlled by the driver IC 200 and the driver IC 201. For example, when only the leftmost heating resistor is heated and only one dot is printed, when the leftmost switch of the driver IC 200 is turned on, a current flows through the leftmost heating resistor to generate heat. Printing can be performed by contacting the heating resistor 110 with a printing paper with a thermal paper or an ink ribbon interposed therebetween.

The color density at the time of printing can be controlled by adjusting the temperature of the heating resistor 110. When performing normal printing, the switch 203 and the switch 204 are electrically connected. As a result, one end of all the heating resistors is connected to the heating resistor power source 33, and the other end is connected to GND (ground) via the switch in the driver IC.
The process of performing this printing is called a heating cycle.

Here, in the present embodiment, the driver IC is divided into two, but the driver IC 200 is controlled by the above method, and while the heating resistors 1 to n are printing, the other The heating resistors n + 1 to 2n connected to the driver IC 201 measure the temperature. On the contrary, from the heating resistor n + 1 to the heating resistor 2
While n is printing, heating resistor 1 to heating resistor n
Measures the temperature. Switch 20 in the temperature measurement cycle
3 or switch 204 is turned off. For example, 1
To n in the temperature measurement cycle, when the temperature of one of the heating resistors 110 is measured, the switch in the driver IC 200 connected to the one heating resistor 110 is turned on, Switch 203 is disabled. As a result, the current passing through one heating resistor 110 does not drop to GND (ground) and flows to the voltage detection circuit unit (12 in FIG. 2). Then, in order to measure the temperature of the second heating resistor 110, the switch in the driver IC 200 connected to the above-mentioned first heating resistor 110 is turned off, and the switch is connected to the second heating resistor 110. The switch in the driver IC is turned on. Hereinafter, the temperature measurement of the heating resistor 110 from 3 to n is also realized by the same operation.

FIG. 2 is a block diagram including a voltage detection circuit section when the switch 203 or the switch 204 of FIG. 3 is made non-conductive. As described above, in the temperature measurement cycle, the switch 203 or the switch 204 in FIG. 3 becomes non-conductive and is connected to GND (ground) via the detection resistor 111 in FIG. The resistance value of the detection resistor 111 is fixed,
The resistance value of the heating resistor 110 has a thermistor characteristic and changes depending on the temperature of the heating resistor 110. Therefore, the voltage input to the buffer amplifier 112 is the heating resistor 1
It rises and falls depending on the temperature of 10, and becomes a constant potential at any temperature. That is, if the temperature of the heating resistor 110 is high, the input voltage of the buffer amplifier 112 is high, and if the temperature is low, the input voltage is low. This voltage is applied to the buffer amplifier 11
It is amplified by 2 and transmitted to the differential amplifier 114. Differential amplifier 1
At 14, an arbitrarily set reference voltage generated by the reference voltage generation circuit 113 is compared with the voltage sent from the buffer amplifier 112, and the difference is output. This output is output as a detection voltage and read into a host system or the like using a general device such as an A / D converter.

The power source of the reference voltage generating circuit 113 uses the same heat generating resistor power source 33 as the power source of the heat generating resistor 110, so that even if the voltage of the heat generating resistor power source 33 drops or rises for some reason, Following this, the reference voltage generated by the reference voltage generating circuit 113 similarly drops or rises. For example, as described above with reference to FIG. 3, the thermal head includes the driver IC 200 and the driver IC 20.
The print pattern is controlled by 1 and the driver IC
When the 200 is in the heating cycle, the other driver I
C201 is in a temperature measurement cycle. Assuming that the driver IC 200 prints a white pattern and then a black pattern, the driver IC 20
Since all the switches of 0 are turned on all at once and a current flows through all the heating resistors 110 from 1 to n, the voltage of the heating resistor power source 33 temporarily drops. However, driver IC
N + 1 to 2n heating resistors 110 connected to 201
Is in a temperature measurement cycle, and the heating resistor power supply 33 drops, so that the voltage input to the buffer amplifier 112 also drops. However, since the reference voltage generated by the reference voltage generating circuit 113 also drops in synchronization with the voltage drop of the heating resistor power supply 33, the voltage drops of each other are canceled out, and high-accuracy temperature measurement becomes possible. Through the series of operations described above, it is possible to always measure the temperature stably regardless of the voltage fluctuation of the heating resistor power source 33.

In addition, by mounting the thermal head 11 and the voltage detection circuit section 12 on the same substrate, it becomes possible to wire the heating resistor 110 and the buffer amplifier 112 in the shortest distance, and the wiring can be connected from the outside. Incoming noise can be minimized. This makes it possible to improve the accuracy of temperature measurement of the heating resistor 110.

Next, a second embodiment of the present invention will be described. In the second embodiment, the basic configuration is the first
It is the same as the embodiment of. In the first embodiment, FIG.
Driver IC in the thermal head circuit in
Although two driver ICs, that is, a driver IC 200 and a driver IC 201, are configured, the present invention can function even if the driver ICs have a configuration of three or more driver ICs.

In the second embodiment, there are three driver ICs.
It is made up of individual pieces. In this case, if the driver ICs are block A, block B, and block C, when block A and block B are in a heating cycle, block C is in a temperature measurement cycle, and when block A and block C are in a heating cycle, Block B is in the temperature measurement cycle, and when block B and block C are in the heating cycle, block A is in the temperature measurement cycle.

As described above, it is possible to use three or more driver ICs, some of them (one or two or more) as a heating cycle, and the rest as temperature measuring cycles. However, when a plurality of driver ICs are used in the temperature measurement cycle, a plurality of voltage detection circuit sections (12 in FIG. 2) are required in parallel.

Further, the thermistor characteristic of the heating resistor 110 is not limited to the case where the resistance value decreases as the temperature rises, and the same effect can be expected in the present invention even when the resistance value rises as the temperature rises.

[0034]

As described above, according to the present invention,
By making the heating head power supply common to the thermal head and the power supply for the reference voltage generation circuit, the temperature measurement value of the heating resistor does not fluctuate even if the heating resistor power supply voltage fluctuates. It becomes possible to measure.

Conventionally, a fluctuation of the heating resistor power source was suppressed by inserting a capacitor having a large capacity into the heating resistor power source of the thermal head, but this is no longer necessary.
Only a small-capacity capacitor for the purpose of removing noise is required, which leads to cost reduction of the thermal head unit. Furthermore, by using a small-capacity capacitor, there is a margin in the mounting area of the thermal head substrate.

By mounting the thermal head and the voltage detection circuit section on the same substrate, the current passing through the heating resistor is input to the buffer amplifier in the shortest distance, so that the noise jumping from the wiring path is minimized. Therefore, the temperature measurement accuracy of the heating resistor can be improved.

By mounting the thermal head and the voltage detection circuit section on the same substrate, it is possible to reduce the total number of parts and the mounting cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of the present invention.

FIG. 2 is a block diagram showing a configuration of a thermal head and a voltage detection circuit unit.

FIG. 3 is a circuit diagram of a thermal head.

[Explanation of symbols]

1 PC 2 printer 11 thermal head 12 Voltage detection circuit section 13 power supply 14 Paper feed motor 15 Paper position detection sensor 16 A / D converter 17 memory 21 Thermal head controller 22 Paper feed controller 23 External interface controller 24 Memory controller 33 Heating resistor power supply 110 heating resistor 111 Detection resistor 112 buffer amplifier 113 Reference voltage generation circuit 114 differential amplifier

Claims (6)

(57) [Claims] 1. A differential amplifier circuit for measuring the temperature of a heating resistor of a thermal head, and a reference voltage generation circuit for supplying a reference voltage to the differential amplifier circuit, which are supplied to the reference voltage generation circuit. A driver that controls the thermal head by using a common power supply as the power supply for the heating resistor.
The IC is divided into two and one driver IC is heated
The other driver IC is
A voltage detection circuit for measuring a thermal head temperature, which is characterized by: 2. The temperature of a heating resistor of a thermal head is measured.
For setting the reference voltage
A reference voltage generating circuit for supplying a pressure,
The power supplied to the generator circuit is supplied to the heating resistor.
Driver that controls the thermal head in common with the power source
1 or 2 or more dry by dividing IC into 3 or more
The remaining driver ICs when the IC is in the heating cycle
A voltage detection circuit for measuring the temperature of a thermal head, which has a temperature measurement cycle. 3. The thermal head temperature measuring voltage detecting circuit according to claim 1, wherein the thermal head is mounted on the same substrate as the thermal head. 4. The printer is heated by the power heating resistors of the thermal head performs the printing, supplies a reference voltage to the differential amplifier circuit with the differential amplifier circuit for measuring the temperature of the heating resistor a thermal head temperature measurement voltage detection circuit having a reference voltage generating circuit, a power source for supplying a common power supplied to the reference voltage generating circuit to the heating resistor, for controlling the thermal head dry
The driver IC is divided into two and one driver IC
Temperature measurement cycle of the other driver IC
Printer, characterized in that a. 5. A heating resistor of a thermal head is applied with electric power.
In a printer that prints by heating,
Differential amplifier circuit for measuring temperature and this differential amplifier circuit
And a reference voltage generating circuit for supplying a reference voltage to the
Equipped with a voltage detection circuit for measuring the round head temperature,
Supply power to the pressure generating circuit to the heating resistor
A drive that shares the same power supply and controls the thermal head
The IC is divided into 3 or more, and 1 or 2 or more
When the Ivar IC is in the heating cycle, the remaining driver I
A printer characterized in that C is a temperature measurement cycle . 6. The printer according to claim 4, wherein the thermal head and the thermal head temperature measuring voltage detection circuit are mounted on the same substrate.