JP5417257B2 - Detection circuit - Google Patents

Description

  The present invention relates to a detection circuit, for example, a detection circuit having a switch that shuts off in a normal state and conducts in an abnormal state to detect the abnormality.

  A detection circuit that detects opening and closing of a cover such as a housing is used. For example, Patent Document 1 describes a detection circuit that uses a switch to detect whether the printer is in a normal state or an abnormal state, such as opening or closing a cover.

JP-A-5-262011

  When a normal state or an abnormal state is detected using a switch, in a method in which the switch is conductive when normal, a current flows through the switch in a normal state and power consumption deteriorates. On the other hand, in the case of a method in which the switch is cut off in the normal state, power consumption can be suppressed, but disconnection of a connection line or the like connected to the switch cannot be determined as abnormal.

  The present invention has been made in view of the above problems, and an object of the present invention is to detect a disconnection of a connection line in a detection circuit that detects a normal abnormality by using a switch that shuts off at a normal time and conducts at the time of abnormality and detects the abnormality. To do.

  The present invention has one end and the other end, and shuts off in a normal state and conducts in an abnormal state and detects an abnormality, a first terminal connected to one end of the switch via a first connection line, and the first terminal A first resistor having one end and the other end connected between a first node between the first connection line and the first constant potential power source, and a connection between the other end of the switch and a second connection line A second resistor having one end and the other end connected between the second terminal, a second node between the second terminal and the second connection line, and a second constant potential power source, A third resistor having one end and the other end connected between the second node and the third constant potential power source, and a fourth resistor connected in parallel with the switch between the one end and the other end of the switch One end of the switch and a third node between the other end of the switch and the second connection line, and the other end of the switch and the third constant voltage And a fourth node between the power source and the third resistor, but is a detection circuit, characterized by comprising a fifth resistor connected through the third connection line, the. According to the present invention, a disconnection of a connection line can be detected in a detection circuit that detects a normal abnormality by using a switch that shuts off at a normal time and conducts at an abnormal time and detects the abnormality.

  In the above configuration, a first connector connected between the first connection line and the first node, a second connector connected between the second connection line and the second node, and the first connector And a third connector connected between the three connection lines and the fourth node. According to this configuration, it is possible to detect disconnection of a connection line or a connector.

  In the above configuration, based on the voltage of the first terminal and the second terminal, detection at normal time or abnormality, disconnection of the first connection line or the first connector, disconnection of the second connection line or the second connector And a controller that detects disconnection of the third connection line or the third connector.

  In the above configuration, the circuit board includes the control unit, the first resistor, the second resistor, and the third resistor, and the first connector, the second connector, and the third connector are connected to the circuit substrate. It can be set as the structure provided in.

  In the above configuration, the potential of the third constant potential power source may be lower than that of the first constant potential power source and the second constant potential power source. In the above configuration, the third constant potential power supply may be a ground.

  In the above configuration, the cover may be closed during the normal time, and the cover may be open during the abnormality. The cover may be a printer cover.

  According to the present invention, a disconnection of a connection line can be detected in a detection circuit that detects a normal abnormality by using a switch that shuts off at a normal time and conducts at an abnormal time and detects the abnormality.

FIG. 1 is a block diagram of the printer according to the first embodiment. 2A and 2B are cross-sectional views showing a printer cover. FIG. 3 is a diagram illustrating a detection circuit according to a comparative example. FIG. 4 is a diagram illustrating the detection circuit according to the first embodiment. FIG. 5 is a diagram showing the potential of each terminal. FIG. 6 is another diagram showing the potential of each terminal. FIG. 7 is a diagram showing the results of measuring the potential of each terminal.

  Hereinafter, a printer will be described as an example of an embodiment of the present invention.

  FIG. 1 is a block diagram of the printer according to the first embodiment. The printer 100 includes a machine unit 20 and a control unit 10. The machine unit 20 includes a thermal head, a printing paper discharge roller, a cover, and the like. The switch 34 is a switch that detects opening and closing of the cover of the mechanical unit 20. The control unit 10 controls the machine unit 20 to print on printing paper. Further, the signal of the switch 34 is received via the connector 18. Based on the signal from the switch 34, it is determined whether the cover is opened or closed. The control unit 10 is formed on a circuit board 12 such as a printed circuit board, and a signal from the machine unit 20 is input from the connector 18 to the control unit 10 via a connection line 16 such as an FPC (Flexible Printed Circuit) or a wire harness. .

  2A and 2B are cross-sectional views showing a printer cover. 2A shows a state in which the cover is open, and FIG. 2B shows a state in which the cover is closed. As shown in FIG. 2A, the printer 100 is provided with covers 21 and 22. The cover 22 houses a printer paper roller 24. The printer paper 26 is fed by the rotation of a rubber roller 28, for example. Printing is performed on the printer paper 26 by a thermal head. The printed printer paper 26 is discharged from the discharge hole 27. The shaft 30 of the roller 28 is fitted into a bearing 32 formed on the cover 21. Thereby, the cover 22 is closed. A switch 34 is provided on the bearing 32. When the cover 22 is closed, the switch 34 is pressed by the shaft 30.

  As shown in FIG. 2B, by opening the cover 22, for example, the printer paper roller 24 in the cover 22 can be replaced. The covers 21 and 22 are mechanically connected to each other at a location 25 by, for example, a hinge. When the cover 22 is opened, the shaft 30 is detached from the bearing 32. Thereby, the switch 34 is opened. As described above, in the first embodiment, the switch 34 is pressed when the cover 22 is closed, and the switch 34 is opened when the cover 22 is opened.

FIG. 3 is a diagram illustrating a detection circuit according to a comparative example. A switch 34 is provided in the machine unit 20. A control unit 10 is provided on the circuit board 12. A connector 18 is provided on the circuit board 12. The switch 34 is electrically connected to the circuit board 12 at the connector 18 via a connection line 16 such as an FPC or a wire harness. One end of the switch 34 is connected to the terminal T of the control unit 10 via the connection line 16 and the connector 18. On the circuit board 12, a resistor R is connected between a node between the connector 18 and the terminal T and the DC power supply _VDD . The other end of the switch 34 is connected to the ground of the control unit 10 via the connection line 16 and the connector 18.

Table 1 shows that in the comparative example shown in FIG. 3, when the cover is closed (when the printer is in a normal state in which the printer can be used), the switch 34 is turned on (turned on), and when the cover is open (the printer). Is a table showing the potential of the terminal T when the switch 34 is cut off (in an off state). The terminal T is low when the cover is closed, and the terminal T is high when the cover is open. For example, when the connector 18 or the like is disconnected, the terminal T becomes high. In the example of FIGS. 2A and 2B, when the cover 22 is open (in an abnormal state), or when the connector 18 or the like is disconnected, the terminal T becomes high, and the control unit 10 It can be determined that any part of the printer is abnormal. However, in the example of Table 1, when the cover on which the printer 100 is operating is closed (in a normal state), a current flows through the resistor R, increasing power consumption.

Table 2 shows a case where the switch 34 is shut off when the cover is closed (in a normal state) and the switch 34 is turned on when the cover is open (in an abnormal state) in the comparative example illustrated in FIG. 6 is a table showing the potential of a terminal T. The terminal T is high when the cover is closed, and the terminal T is low when the cover is open. When the connector 18 or the like is disconnected, the terminal T becomes high. When the cover is closed (in a normal state), no current flows through the resistor R, and power consumption can be reduced. However, the terminal T is also high when the connector 18 or the like is disconnected. Therefore, the control unit 10 cannot detect the disconnection abnormality of the connector 18 or the like.

  FIG. 4 is a diagram illustrating the detection circuit according to the first embodiment. Referring to FIG. 4, the machine unit 20 is provided with a switch 34, a fourth resistor R <b> 4, and a fifth resistor R <b> 5. A first resistor R1, a second resistor R2, and a third resistor R3 are provided on the circuit board 12 together with the control unit 10. A detection signal is input to the control unit 10 from the first terminal T1 and the second terminal T2. The circuit board 12 is provided with a first connector C1, a second connector C2, and a third connector C3. The machine part 20 and the first connector C1, the second connector C2, and the third connector C3 are connected by a first connection line L1, a second connection line L2, and a third connection line L3, respectively. The first connection line L1, the second connection line L2, and the third connection line L3 are, for example, an FPC or a wire harness.

The switch 34 is a switch for detecting opening and closing of the cover 22 and has one end and the other end. The switch 34 is cut off at the normal time and is turned on at the time of abnormality to detect the abnormality. The first terminal T1 is connected to one end of the switch 34 via the first connection line L1. One end and the other end of the first resistor R1 are respectively connected between the first node N1 between the first terminal T1 and the first connection line L1 and the first constant potential power source _VDD1 . The second terminal T2 is connected to the other end of the switch 34 via the second connection line L2. One end and the other end of the second resistor R2 are respectively connected between the second node N2 between the second terminal T2 and the second connection line L2 and the second constant potential power source _VDD2 .

  The third resistor R3 has one end and the other end connected between the second node N2 between the second terminal T2 and the second connection line L2 and the third constant potential power supply Gnd. The fourth resistor R <b> 4 is connected in parallel with the switch 34 between one end and the other end of the switch 34. The fifth resistor R5 has one end connected to the third node N3 between the other end of the switch 34 and the second connection line L2, and between the other end and the third constant potential power supply Gnd and the third resistor R3. The fourth node N4 and the fourth node N4 are connected via the third connection line L3.

  The first connector C1 is connected between the first connection line L1 and the first node N1. The second connector C2 is connected between the second connection line L2 and the second node N2. The third connector C3 is connected between the third connection line L3 and the fourth node N4.

  The control unit 10 includes an AD (Analog Digital) converter and a microcomputer. The AD converter converts the voltage at the first terminal T1 and the second terminal T2 into a digital signal. Based on the digital signal, the microcomputer determines whether the cover 21 is in the normal normal state or the connection line 16 or the connector 18 is disconnected.

FIG. 5 is a diagram showing the potential of each terminal. The voltage of the first constant potential power supply V _DD1 and the second constant potential power supply V _DD2 is V _DD , the third constant potential power supply is ground (potential is 0 V), and the resistance values of the first resistor R1 to the fifth resistor R5 are R1 to R5. It was. At this time, the potentials of the first terminal T1 and the second terminal T2 when the cover is closed (normal normal state), the cover is open (abnormal state), and the connector is not connected (connectors C1 to C3 are not connected) are shown. . Thus, the switch 34 is in a cut-off state when the cover is closed, and the switch 34 is in a conductive state when the cover is open. That is, in the normal state (cover closed), no current flows through the switch 34, and power consumption can be suppressed. As shown in FIG. 5, the control unit 10 can detect a normal state (cover closed), an abnormal state (cover open), and a connector unconnected state by measuring the potentials of the first terminal T1 and the second terminal T2. it can.

FIG. 6 is another diagram showing the potential of each terminal. Similarly to FIG. 5, the voltage of the first constant potential power supply V _DD1 and the second constant potential power supply V _DD2 is V _DD , the third constant potential power supply is ground, and the resistance values of the first resistor R1 to the fifth resistor R5 are R1 R5. At this time, when the first connection line L1 or the first connector C1 is disconnected, when the second connection line L2 or the second connector C2 is disconnected, when the third connection line L3 or the third connector C3 is disconnected, The potentials of the first terminal T1 and the second terminal T2 when the cover is closed (normal state) and the cover is open (abnormal state) are shown. As shown in FIG. 6, when the control unit 10 measures the potentials of the first terminal T1 and the second terminal T2, the first connection line L1 or the first connector C1 to the third connection line L3 or the third connector C3. It is also possible to detect which connection line or connector is disconnected.

FIG. 7 is a diagram showing the results of measuring the potential of each terminal. The voltage at the first terminal T1 and the second terminal T2 was measured by setting V _DD to 3.3 V and the resistance values R1 to R5 of the first resistors R1 to R5 to 1 kΩ, respectively. When the cover is closed (normal state) and the cover is open (abnormal state) when the connector 18 is not disconnected, the third connection line L3 or the third connector C3 is disconnected from the first connection line L1 or the first connector C1. For each time, measurements were taken with the cover closed and the cover open. In actual measurement, there is a resistance component other than the first resistance R1 to the fifth resistance R5. Therefore, in FIG. 7, the voltages at the first terminal T1 and the second terminal T2 are as calculated values in FIGS. It is not a value. However, when the control unit 10 measures the voltages of the first terminal T1 and the second terminal T2, the control unit 10 can detect opening / closing of the cover and disconnection of the connection line or connector. The resistors R1 to R5 are 1 kΩ, but other resistors may be used. Moreover, you may have a different resistance value for every resistance R1-R5.

  As described above, according to the first embodiment, the control unit 10 detects the normal time or the abnormality, the first connection line L1 or the first connector C1 based on the voltages of the first terminal T1 and the second terminal T2. The disconnection, the disconnection of the second connection line L2 or the second connector C2, and the disconnection of the third connection line L3 or the third connector C3 can be detected. Even when the first connector C1 to the third connector C3 are not provided, the disconnection of the first connection line L1 to the third connection line L3 can be detected.

  The first connector C1 to the second connector C3 may be a connection portion in one connector. The first connection line L1 to the third connection line L3 may be connection lines in one FPC.

  Further, the circuit board 12 is mounted with the control unit 10, the first resistor R1, the second resistor R2, and the third resistor R3. The first connector C1, the second connector C2, and the third connector C3 are provided on the circuit board 12. It has been. Thus, when the output of the mechanical unit 20 is input to the circuit board 12 via the connector 18 to the circuit board 12, disconnection at the connector is likely to occur. According to the first embodiment, such disconnection can be detected.

  The potential of the third constant potential power source is preferably lower than that of the first constant potential power source and the second constant potential power source. Alternatively, the potential of the third constant potential power source may be higher than that of the first constant potential power source and the second constant potential power source. Further, the third constant potential power source is not necessarily a ground as long as it is a constant potential power source, but a ground can be used as a simple constant potential.

  In the first embodiment, the case where the cover 21 is closed in the normal state and the cover 21 is open in the abnormal state has been described as an example. However, the switch 34 that shuts off in the normal state and conducts in the abnormal state and detects the abnormality. If so, a normal state or an abnormal state other than the opening / closing of the cover may be detected.

  Moreover, although the example of the cover of the printer 100 has been described as the cover 21, it may be a cover of an electronic device other than the printer.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Control part 12 Circuit board 20 Machine part 34 Switch C1 1st connector C2 2nd connector C3 3rd connector L1 1st connection line L2 2nd connection line L3 3rd connection line R1 1st resistance R2 2nd resistance R3 3rd resistance R4 4th resistance R5 5th resistance V _DD1 1st constant potential power supply V _DD2 2nd constant potential power supply Gnd 3rd constant potential power supply

Claims (8)

A switch having one end and the other end, which shuts off at normal time and conducts at abnormal time to detect abnormality;
A first terminal connected to one end of the switch via a first connection line;
A first resistor having one end and the other end connected between a first node between the first terminal and the first connection line and a first constant potential power supply;
A second terminal connected to the other end of the switch via a second connection line;
A second resistor having one end and the other end connected between a second node between the second terminal and the second connection line and a second constant potential power supply;
A third resistor having one end and the other end connected between the second node and a third constant potential power source;
A fourth resistor connected in parallel with the switch between one end and the other end of the switch;
One end is connected to a third node between the other end of the switch and the second connection line, and the other end and a fourth node between the third constant potential power source and the third resistor are A fifth resistor connected via three connecting lines;
A detection circuit comprising: A first connector connected between the first connection line and the first node;
A second connector connected between the second connection line and the second node;
The detection circuit according to claim 1, further comprising a third connector connected between the third connection line and the fourth node.   Based on the voltage of the first terminal and the second terminal, detection at normal time or abnormality, disconnection of the first connection line or the first connector, disconnection of the second connection line or the second connector, and the first The detection circuit according to claim 2, further comprising a control unit that detects disconnection of the three connection lines or the third connector.   A circuit board on which the control unit, the first resistor, the second resistor, and the third resistor are mounted; and the first connector, the second connector, and the third connector are provided on the circuit board. The detection circuit according to claim 3.   5. The detection circuit according to claim 1, wherein a potential of the third constant potential power source is lower than that of the first constant potential power source and the second constant potential power source.   6. The detection circuit according to claim 5, wherein the third constant potential power source is a ground.   The detection circuit according to claim 1, wherein the cover is closed during the normal time and the cover is open during the abnormality.   8. The detection circuit according to claim 7, wherein the cover is a cover of a printer.

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