JP2644403B2 - IC and its temperature alarm control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IC having a built-in temperature rise detecting circuit for detecting a temperature rise inside the IC and a method for controlling a temperature alarm of the IC. The present invention relates to an alarm control method.

[0002]

2. Description of the Related Art Various types of serial printers include a print head, a space (SP) motor for moving the print head in the width direction of a print medium, and a line feed (LF) motor for controlling feed of the print medium. Actuators are mounted, and these actuators are driven and controlled by individually provided drive circuits.

Conventionally, these drive circuits are composed of discrete components. In recent years, however, due to improvement in semiconductor technology, a monolithic IC in which a logic circuit of an input stage and a power transistor circuit of an output stage are integrated into one chip, and a small number of external circuits. It is composed of mounting parts. Monolithic driver IC
In the case of (1), the number of components can be reduced and the mounting area can be reduced, so that cost reduction can be expected. On the other hand, since heat dissipation due to power loss of the driver IC itself increases, control in consideration of heat generation is required.

FIG. 5 is a circuit diagram showing a conventional example of a control system for a temperature alarm of a driver IC. In the figure, the driver IC13 which drives the various actuators is TSD (thermal shutdown) circuit 14 which operates to be equal to or higher than a predetermined temperature (on) internal power supply by the output terminal 15 is the resistance R ₀ ( 5V) and a microprocessor (hereinafter μCPU)
2) input port P1.

A reset input terminal (pin) 16 of a logic circuit of an input stage (not shown) of the driver IC 13 is
It is pulled up to the power supply (5V) by the resistance R _1. The reset input terminal 16 has a RESET-P
The signal is input as a RESET-N signal when the polarity of the signal is inverted by the transistor TR.

[0006] The μCPU 2 sends a drive signal to the driver IC 13 and monitors the state of the input port P 1 at regular intervals. When the level of the input port P1 is “H” level (power supply level), the μCPU 2 continuously sends out a drive signal because the TSD circuit 14 in the driver IC 13 is in an inactive (off) state. When the level of the port P1 is "L" level (ground level), it is recognized that the TSD circuit 14 in the driver IC 13 is operating (ON), the driver IC 13 has become high temperature and a temperature alarm has been issued, The transmission of the drive signal is stopped.

[0007] When the temperature of the driver IC 13 decreases due to the drive stop, the TSD circuit 14 is disabled again (OFF).
State. As a result, the level of the input port P1 becomes high, so that the μCPU 2 restarts sending the drive signal to the driver IC 13 which has been stopped.

[0008]

However, in the above-described conventional temperature alarm control method, a dedicated output pin (output terminal 15) for deriving the output of the TSD circuit 14 is used.
Are required for the driver IC 13, and the μCPU 2 also requires an input port P1 for detection. Therefore, as the number of driver ICs 13 increases, μ
It is necessary to increase the number of the input ports P1 of the CPU 2, and accordingly, there is a problem that the number of circuits such as a level comparator externally connected to the input port P1 also increases.

On the other hand, a method without the TSD circuit 14 is also conceivable. In such a method, although the circuit can be reduced, a heat sink is required to keep the temperature of the driver IC 13 from becoming high. The problem that this occurs will occur.

Therefore, the present invention does not require increasing the number of pins of the IC itself, and even if the number of ICs increases, the μCPU
It is an object of the present invention to provide an IC that does not need to increase the number of input ports and a temperature alarm control method for the IC.

[0011]

SUMMARY OF THE INVENTION An IC according to the present invention has
The output terminal of the temperature rise detection circuit for detecting the temperature rise inside C is shared with the reset circuit input terminal inside the IC. Further, in the temperature alarm control method according to the present invention, in the IC having the above configuration, the input terminal for the reset circuit is connected to the input terminal for the A / D converter of the μCPU.
The level of the A / D converter input terminal is monitored at regular intervals by the μCPU.

[0012]

In an IC having a built-in temperature rise detection circuit for detecting a temperature rise inside the IC, the input terminal for the reset circuit which is not used in the driving state and the output terminal of the temperature rise detection circuit are shared, so that the temperature of the IC itself rises. There is no need to provide an output terminal (pin) dedicated to the detection circuit.
By detecting the state of the temperature rise detection circuit using the input terminal for D converter, even if the number of ICs increases, the μCPU
There is no need to increase the number of pins and the associated circuits.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. The configuration in which a μCPU 2, a driver IC 13, and a TSD circuit 14 as a temperature rise detection circuit are provided is the same as that of the conventional example. The output of the TSD circuit 14 is an open collector output, a reset input terminal of the driver IC13 and an output terminal via a resistor R ₂ (pins) 16
To share the pins.

[0014] reset input terminal 16 is pulled up to the power supply (5V) by the resistance R _1. A RESET-N signal obtained by inverting the polarity of a RESET-P signal, which is a reset input, by a transistor TR is applied to the reset input terminal 16 as in the conventional example. At the same time, this RESET-N signal is also applied to the A / D converter input terminal (pin) 17 of the μCPU 2.

Next, the circuit operation of such a configuration will be described. While the reset circuit (not shown) is operating after the power of the printer is turned on, the RESET-P signal is generated. When the RESET-P signal is applied to the base and the transistor TR is turned on, the RESET-P signal is generated. The N signal is input to the reset input terminal 16 of the driver IC 13. This RESET-N signal is also input to the A / D converter input terminal 17 of the μCPU 2, but during resetting, the μCPU 2 itself is also reset.
The low level input, which is a signal, can be ignored.

After the reset is released, the driver I
C13 is no temperature rise, since TSD circuit 14 is in the inoperative (OFF) state, MyuCPU2 from that the A / D converter input terminal 17 is pulled up to the power supply (5V) by the resistance R ₁ " H level (≒ 5 V) is detected. In this state, the μCPU 2 is connected to the driver IC 1
3, a drive signal can be sent to the control unit 3 as in the conventional example.
The input level of the A / D converter input terminal 17 is monitored at regular intervals.

During driving of the driver IC 13, when the temperature of the driver IC 13 rises and the TSD circuit 14 operates (turns on), the input level of the input terminal 17 for the A / D converter of the μCPU 2 changes the power supply voltage (5 V) to a resistance. R ₁
A and dividing the value by the resistor _{R 2 (5 × R 2 /} (R 1 + R 2)). For example, when R ₁ = R ₂ is set, the partial pressure level is 2.5V.

When the μCPU 2 detects the input level of the input terminal 17 for the A / D converter, it recognizes that the driver IC 13 has issued a temperature alarm at a high temperature, stops sending the drive signal, and lowers the temperature of the driver IC 13. Wait for When the temperature of the driver IC 13 decreases, the TSD circuit 1
4 is turned off, and the input level of the A / D converter input terminal 17 of the μCPU 2 is again set to the “H” level (# 5
V), the μCPU 2 restarts driving the driver IC 13.

As described above, since the A / D converter input terminal 17 is used as an input port for monitoring a temperature alarm, the state of the driver IC 13, that is, the state of the driver IC 13 without an external circuit such as a level comparator is provided. It can be determined whether or not the IC 13 has issued a temperature alarm.

In this example, only a temperature alarm is issued by a single partial pressure level. However, since the A / D converter can identify a plurality of levels, for example, a binary partial voltage level is set. It is also possible to issue a warning alarm before issuing a temperature alarm depending on the partial pressure level of the alarm. According to this, before the driving of the driver IC 13 is stopped, a corresponding measure can be taken.

FIG. 2 shows the configuration of a control system of a serial printer using the driver IC 13 as a drive circuit for various actuators. In FIG. 1, a bus line 1 includes a μCPU 2, a read only memory (ROM) 3, a random access memory (RAM) 4, an interface (I / F) controller 5, a head drive circuit 6, an SP motor drive circuit 7, and an LF. The motor drive circuits 8 are respectively connected. The driver IC 13 according to the present invention is applied to the head drive circuit 6, the SP motor drive circuit 7, and the LF motor drive circuit 8.

The .mu.CPU 2 is a circuit for performing calculations for controlling the printer, and the ROM 3 is a memory for storing its operation program and the like. The RAM 4 is a memory for storing various data necessary for operations such as operations. The I / F control unit 5 is a circuit that receives serial data from the host computer via the I / F connector 9 and sends out predetermined information to the host computer via the I / F connector 9.

The head drive circuit 6 controls the print head 10
The SP motor drive circuit 7 drives the print head 10 to perform predetermined printing under the control of the CPU 2, and the space (S) for moving the print head 10 in the width direction of the print medium.
P) A circuit for controlling the motor 11. The LF motor drive circuit 8 is a circuit that controls a line feed (LF) motor 12 that controls the feeding of a print medium.

FIG. 3 is a circuit diagram showing an embodiment in which the present invention is applied to an apparatus having a plurality of drive circuits as described above. The basic circuit configuration is the same as that of FIG. In the present embodiment, the T of the _n driver ICs 13 _{1 to} 13 _n is
Resistors R _{2-1 to} R _2-1 inserted between the output terminals of the SD circuits 14 _{1 to} 14 _n and the reset input terminals 16 _{1 to} 16 _n.
Each resistance value of _2-n is different. Note that, in principle, the driver ICs 13 _n can be connected to the A / D converter input terminal 17 by the number corresponding to the resolution of the A / D converter.

As described above, by changing the resistance values of the resistors R _{2-1 to} R _2-n , each of the driver ICs 13 _{1 to} 13 _{n is changed.}
When one of the TSD circuits 14 _{1 to} 14 _n is turned on, the input level of the A / D converter input terminal 17 of the μCPU ₂ is 5 × R _2-n / (R ₁ +
R _2-n ), each driver IC 13 _{1 -1}
Since the level is different every 3 _n, it is possible to determine which driver IC has issued the high temperature alarm.

Next, a processing procedure for determining which driver IC has issued the high temperature alarm in the configuration of FIG. 3 will be described with reference to the flowchart of FIG. This process is executed by the μCPU 2 at regular intervals. The μCPU 2 first takes in the input level Vin of the A / D converter input terminal 17 (step S1), and determines whether or not this input level Vin is approximately 5 V (power supply level) (step S2).
If Vin ≒ 5V, this process ends.

If Vin ≒ 5V, the input level V
in the resistance of each driver IC13 ₁ ~13 _n R _2-1
By comparing the respective level V ₁ ~V _n determined by the resistance value of the to R _2-n, which driver IC is to determine very hot (Step S3 ₁ ~S3 _n), determines the driver IC Is determined to have issued a high temperature alarm, and the driving of the driver IC is stopped (step S4).
_{1 to} S4 _n ).

In the above embodiment, the driver I
Although the case where the present invention is applied to C has been described, the present invention can be applied not only to a driver IC but also to a logic IC that wants to detect a high temperature state.

[0029]

As described in detail above, according to the present invention, the input terminal of the reset circuit and the output terminal of the TSD circuit which are not used in the driving state are shared in the IC, so that the IC itself is dedicated to the TSD circuit. It is not necessary to provide an output terminal (pin). Further, since the state of the TSD circuit is detected using the input terminal for the A / D converter of the μCPU, even if the number of ICs increases, the μCP
Since it is not necessary to increase the number of pins of U and the circuits associated therewith, the temperature alarm control of the IC can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram of a control circuit of the serial printer.

FIG. 3 is a circuit diagram showing another embodiment of the present invention.

FIG. 4 is a flowchart showing a processing procedure for determining which of a plurality of driver ICs has issued a high temperature alarm.

FIG. 5 is a circuit diagram showing a conventional example.

[Explanation of symbols]

2 μCPU (microprocessor) 6 Head drive circuit 7 SP motor drive circuit 8 LF motor drive circuit 10 Print head 11 SP (space) motor 12 LF (line feed) motor 13, 13 _{1 to} 13 _n Driver IC 14, 14 ₁ to 14 _n TSD (thermal shutdown) circuit 16, 16 _{1 to} 16 _n Reset input terminal 17 A / D converter input terminal

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tadashi Kasai 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (56) References JP-A-2-59630 (JP, A)

Claims (2)

(57) [Claims] 1. An IC incorporating a temperature rise detection circuit for detecting a temperature rise inside the IC, wherein an output terminal of the temperature rise detection circuit is shared with an input terminal for a reset circuit inside the IC. 2. The IC temperature alarm control method according to claim 1, wherein the reset circuit input terminal is connected to an A terminal of a microprocessor.
A temperature alarm control method for an IC which is connected to an input terminal for an A / D converter and monitors the level of the input terminal for the A / D converter at regular intervals by the microprocessor.