JPS5939568A - Supply power controller for thermal head - Google Patents

Abstract

PURPOSE:To eliminate manual adjusting work by providing a thermal head with a heat generating resistor for detecting the same in the resistance value as a heat generating resistor for recording and automatically adjusting supply power of the thermal head indirectly detecting the resistance value thereof. CONSTITUTION:Heat generating resistors 11 for detection with a resistance value R is provided across a heat generating resistor 10 for recording of a thermal head 4. A circuit is provided to adjust a voltage VD to be applied to the heat generating resistor 10 for recording from a constant voltage circuit 1 depending on the resistance value of the resistor 11. When a reference voltage V3 for detection is applied to a reference resistance 14 connected in series to two resistors 11 for detection, divided voltages V1 and V2 develop therein and are applied to input terminals A and B of a voltage adder 5. A signal of the result (V1+V2) is inputted into an A/D converter 6 and converted to a pit parallel logic signal to be inputted into a CPU circuit 8. Based on informations from a PROM12 and an RAM13, a control signal is emitted from the CPU circuit 8 to control the output voltage of the constant voltage power circuit 1 via an A/D converter 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal recording head for a facsimile machine, etc.
In particular, it relates to control of power supply to a thermal head.

A conventional thermal head drive circuit supplies a constant voltage from a constant voltage power supply circuit 1 to a plurality of heat generating resistor groups of a thermal head, as shown in Fig. 1. It is something. That is, the adjusted applied voltage VD from the constant voltage power supply circuit 7 is applied to the drive transistors TRA1°TA2. ......, the voltage application terminal TAI of the thermal head 2 is sequentially connected by TRAn,
TA2, old...

Scanning is applied to TAn. On the other hand, the other end of the heating resistor is connected to a selection transistor T via a diode matrix 3.
It is guided to RB1, TRB2, ~TRBn. Thus, for example, the drive transistor TB.

When A1 is ``ON'' and the selection transistor TRBI is ``ON'', a current flows to the heating resistor marked with a square mark, generating heat, and the thermal recording paper in contact with the heating resistor is heated. Develops color.

The recording quality by such a thermal head is greatly affected by the power supplied to the heating resistor, which is determined by the resistance value R of the heating resistor and the applied voltage VD.

Generally, the resistance value R of the heating resistor is about 100 to 2000, and the resistance value has a slight deviation depending on the thermal head. Therefore, when using a thermal head in a facsimile machine, etc., conventionally, the resistance value R of the heat generating resistor is measured in advance, and depending on the value, a constant voltage power supply is used in one stage with a thermal head drive circuit built into the device. Adjust the voltage VD applied to the thermal head 2 with the output voltage adjustment volume of the circuit 1, or adjust the voltage VD applied to the thermal head 2 with the output voltage adjustment volume of the circuit 1, or
It is customary to set the electric power corresponding to the resistance value of the recording heating resistor by adjusting the width of the thermal head drive pulse applied to l to TRA n.

Therefore, the power supplied to the heat generating resistor must be manually set by the operator when the device is manufactured, which takes time, and the adjustment must be made again when the thermal head is replaced.

Therefore, an object of the present invention is to maintain good recording quality by automatically supplying the optimum recording power to the heating resistor for recording in the thermal head, while at the same time eliminating the conventional manual adjustment of supplied power. It is an object of the present invention to provide a novel thermal head supply power control device that does not require a power supply.

According to the present invention, in a thermal head power supply control method that controls the recording power applied to a plurality of recording heating resistors in a thermal head, a detection heating resistor having the same resistance value as the recording heating resistor is used. a thermal head including a thermal head, a detector that detects a certain output amount proportional to the resistance value of the heating resistor for detection as described in item 9 above, and an analog-to-digital (A/D') converter that digitizes the output of the detector. a control circuit that outputs a control data signal to apply an optimal DC voltage to the thermal head based on the output of the analog-to-digital converter; and a constant DC voltage whose output voltage is adjusted by the analogized control data signal. There is obtained a thermal head power supply control device comprising: a power supply; the power supply to the thermal head is adjusted by the output voltage of the DC constant voltage power supply;

The present invention uses a thermal head consisting of a plurality of heating resistors for recording and two heating resistors for measuring resistance value, and connects the two heating resistors for measuring resistance value through a reference resistor having a constant resistance value. A constant voltage is supplied to the two heating resistors for resistance value measurement, and the divided voltages applied to each of the two heating resistors for resistance value measurement are added and converted into a digital signal by an analog-to-digital converter. Furthermore, the optimal thermal head supply power corresponding to the digital signal value is determined by a microprocessor or logic circuit, and supply power control information is output, thereby automatically adjusting the thermal head supply power.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a circuit diagram showing a first embodiment of the present invention, which includes a recording heating resistor 10 having a resistance value R and a detecting heating resistor 11 having a resistance value R at both ends thereof.
and a control circuit section for adjusting the voltage VD applied from the constant voltage power supply circuit 1 to the recording heat generating resistor 10 according to the resistance value of the detecting heat generating resistor 11. It consists of:

To explain the circuit of FIG. 2 in more detail, one end of the two heating resistors 11 for detection in the thermal head 4 is grounded, and the other end is connected in series with a reference resistor 14 having a constant resistance value Ra. When the reference voltage v8 for detection is applied, divided voltages v1 and v2 determined by the respective resistance values appear at both ends of the two heating resistors 11 for detection. These two types of divided voltages are respectively applied to input terminals A and B of the voltage adder 5 and added, and the addition result (Vt
+Vs) is input to an analog-to-digital (A/D) converter 6. Then, the A/D converter 6 converts it into a bit-parallel logic signal and inputs it to the CPU circuit 8.

The CPU circuit 8 includes a program read-only memory (LL?, ROM) 12 that stores data related to the control of the voltage applied to the thermal head 4, and a random access memory (A, M) 13. is connected, and an average value is calculated from the addition results of the divided voltages Vr and Vt of the two detection heating resistors 110 converted into the bit parallel logic signals, and the result is temporarily stored in the RAM 13, and the average value is The control data written in the FROM 12 corresponding to the above is outputted, and the control data is inputted to the digital/analog (A/D) converter 7. The digital-to-analog converter 7 converts the control data into an analog voltage level and applies it to the output voltage adjustment terminal of the constant voltage power supply circuit 1. Therefore, the output voltage of the constant voltage power supply circuit 1 is adjusted to control the power supplied to the thermal head.

FIG. 3 shows a second embodiment of the present invention, in which the same thermal head as in the first embodiment is used. Two heating resistors 1 for detection inside the thermal head 4
The circuit is the same as the first embodiment until the addition result of the divided voltages Vl and Vt of 1 is input to the A/D converter 6 and a bit-parallel logic signal is output. Read-only memory (ROM) is used as a means of generating control data to control the applied voltage.
9 is used, and control data for controlling the voltage applied to the thermal head is written in advance in this ROM9, so the addition result of the divided voltage of the detection heating resistor converted into a logic signal is stored in the ROM9. The control data for that address is output to the digital/analog (D/A) converter 7.

This D/A converter 7 converts the information from the ROM 9 into an analog voltage level and applies it to the output voltage adjustment terminal of the constant voltage power supply circuit 1, thereby controlling the power supplied to the thermal head.

Note that when applying a DC voltage from the DC constant voltage power supply 1 to the thermal head 4, the drive transistors TRA1. ...
. . , TRAn are sequentially driven, and by further driving the selection transistors TRBI, .

The reason why the heating resistors for detection were provided at both ends of the thermal head in the above two embodiments is to detect the average change in the resistance value of the heating resistor with respect to the change in temperature distribution within the thermal head. Even one heating resistor for
Alternatively, there may be two or more.

The first aspect of the invention described above. The second embodiment merely shows one implementation means of the thermal head supply power control method,
This system is not limited only to the above embodiments. For example, instead of detecting the divided voltage of the detection heating resistor 11, a method of detecting the current value may be used, or a control circuit using a logic element may be used as means for determining the power applied to the thermal head.

As explained above, the present invention provides means for providing a thermal head with a detecting heating resistor having the same resistance value as the recording heating resistor, and indirectly detecting the resistance value of the detecting heating resistor; Since the configuration has a means for outputting control data using a detected value by the controller and a means for adjusting the power supplied to the thermal head using the control data, the adjustment of the power supplied to the thermal head is automated. This eliminates the need for adjustment work that has traditionally been done manually, and has the advantage of always being able to supply optimal power.

[Brief explanation of drawings]

FIG. 1 shows a conventional thermal head drive control circuit, FIG. 2 shows a first embodiment of the thermal head supply power control circuit of the present invention, and FIG. 3 shows a control circuit of the second embodiment. DESCRIPTION OF SYMBOLS 1... Constant voltage power supply circuit, 2... Typical conventional thermal head, 3... Old diode matrix, 4... Thermal head according to the present invention, 5...
...Voltage adder, 6...Analog-to-digital (A/D) converter, 7...Digital
Analog (D/A) converter, 8... CPU circuit, 9... Read only memo + J (ROM
), 1o... heating resistor for recording, 11...
...Heating resistor for detection, 12...Program...
Read-only memory (FROM), 13...10
− °“Random Access Memory (RAM), 14...
...Standard resistance. 11- Procedural amendment (voluntary) 1. Display of incident 1982 Patent Application No. 1503
No. 72 No. 2, Title of the invention: Thermal head applied power control circuit 3, Relationship to the amended case Applicant: 5-33-1 Shiba, Minato-ku, Tokyo (423) NEC Corporation Representative: Tadahiro Sekimoto 4; Agent: Sumitomo Sanda Building, NEC Corporation, 37-8 Shiba 5-chome, Minato-ku, Tokyo 108 (6591) Patent Attorney Susumu Uchihara Telephone Tokyo (0)
3) 456-3111 (main representative) (contact information: Nippon Denku Co., Ltd. Patent Department) 5. Subject of amendment (2) "Title of the invention" column of the specification. (3) "Claims" column. (4) "Detailed description of the invention" column. 6. Correction details: "Power supply control device" is corrected to "Thermal head applied power control circuit". (3) In No. 1 of the same, the "Claims" column is amended as shown in the attached sheet. (4) On page 4, in the first to second lines, ``runner-up'' is corrected to ``defect.'' (5) On page 4, line 7, "power control device" is corrected to "power control circuit." (6) On page 4, line 9, ``Multiple records in the head/throat'' is corrected to ``Records in the head.'' 2- (7) On page 4, line 11, "power control method" is corrected to "power control circuit." (8) From the 4th page, line 11 to the 5th page, line 2 [Thermal head including a heating resistor for detection having the same resistance value as the heating resistor for recording; a detector that detects a certain output amount proportional to the resistance value of the heating resistor;
an analog-to-digital (A/D) converter that digitizes the output of the detector; and a control circuit that outputs a control data signal to apply an optimal DC voltage to the thermal head using the output of the analog-to-digital converter. and a DC voltage power supply whose output voltage is adjusted by the analogized control data signal, and "at the output voltage of the DC voltage power supply" is replaced by "the recording heat generating resistor located near the recording heat generating resistor". a detector that detects a certain output amount proportional to the resistance value of a heating resistor for detection having the same resistance value as the body;
and a control circuit that determines the optimum recording power for the thermal head from the output of the detector and outputs a recording power control signal, and corrects the recording power according to the output of the control circuit. (9) On page 5, line 4, "power control device" is corrected to "power control circuit." a9 On page 5, lines 5 to 6, "Multiple heating resistors for recording and two for measuring resistance values" is corrected to "Heating resistors for recording and two for detecting". Uυ Same page 5, line 7 “For measuring the two resistances”
Corrected to ``for detection purposes''. α Force On page 5, lines 9 to 10, "for measuring the two resistance values" is corrected to "for detecting the two." 4- Claims: “A thermal head supply power control circuit that controls the recording power applied to a recording heating resistor of a thermal head, which is located near the recording heating resistor and is the same as the recording heating resistor. A thermal head supply power control circuit comprising: a detector that detects a certain output amount proportional to the resistance value of a detection heating resistor having a resistance value; and a thermal head supply power control circuit that adjusts pre-power from the output of the detector.

Claims (1)

[Claims] A thermal head supply power control device that controls recording power applied to a plurality of recording heating resistors of a thermal head, the thermal head including a detection heating resistor having the same resistance value as the recording heating resistor; a detector that detects a certain output amount that is proportional to the resistance value of a heating resistor for detection; an analog-to-digital converter that digitizes the output of the detector; It includes a control circuit that outputs a control data signal in order to apply an optimal DC voltage, and a DC constant voltage power supply whose output voltage is adjusted by the analogized control data signal, and the output voltage of the DC constant voltage power supply is adjusted to A thermal head power supply control device that adjusts power supply to a thermal head.