JP2018133665A - Input signal erroneous determination prevention circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an input signal erroneous determination prevention circuit of simple circuitry, in which a microcomputer prevents erroneous determination of the state of a switch according to an inputted signal.SOLUTION: An input signal erroneous determination prevention circuit 10 includes a comparison circuit 11 for comparing the power supply voltage V of a power supply 3 with a voltage threshold L, and outputting a voltage drop signal Sa when the power supply voltage V goes below the voltage threshold L, a holding circuit 12 receiving a voltage signal S1 continuously from a switch 5, and when receiving the voltage drop signal Sa outputted from the comparison circuit 11, holding the voltage signal S1, received before receiving the voltage drop signal Sa, as a holding signal S2, and a changeover circuit 13 for receiving the voltage signal S1 and the holding signal S2, outputting the voltage signal S1 to a microcomputer 2 when the power supply voltage is normal, and outputting the holding signal S2 to the microcomputer 2 during when power supply voltage drop when the voltage drop signal Sa is outputted.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an input signal misjudgment prevention circuit applied to an electronic control device that controls the operation of a controlled object in accordance with connection / disconnection of a switch.

  Conventionally, for example, a vehicle-mounted control device disclosed in Patent Document 1 below is known. In this conventional vehicle-mounted control device, the switch input circuit periodically samples the ON / OFF state of the external switch in accordance with an instruction from the microcomputer. Further, the microcomputer determines that the battery voltage has dropped and stops sampling of the external switch by the switch input circuit when the battery voltage drops.

  Conventionally, for example, a latch device and a latch method disclosed in Patent Document 2 below are also known. This conventional latch device includes a first latch circuit, a filter circuit, an invalidation circuit, and a second latch circuit. The first latch circuit latches input data in accordance with the first latch signal. The filter circuit outputs a third latch signal generated by passing a second latch signal delayed from the first latch signal through a low-pass filter. The invalidation circuit invalidates the second latch signal when a drop in the power supply voltage is detected. The second latch circuit latches the output data of the first latch circuit in accordance with the third latch signal.

JP 2002-347541 A JP 2010-246074 A

  However, in the above-described conventional vehicle-mounted control device, it takes time until the microcomputer (microcomputer) determines that the battery voltage (power supply voltage) has decreased and holds the signal indicating the ON / OFF state of the external switch (delayed). There is a case. In this case, in the above-described conventional vehicle-mounted control device, there is a possibility that the ON / OFF state of the external switch may be erroneously determined according to the signal input by the microcomputer when an instantaneous power supply voltage drop occurs. . Further, the conventional latch device needs to include a first latch circuit, a filter circuit, an invalidation circuit, and a second latch circuit, and the configuration of the device (circuit) is complicated.

  The present invention has been made to solve the above problems. That is, an object of the present invention is to provide an input signal misjudgment prevention circuit that has a simple circuit configuration and prevents erroneous judgment of the state of a switch in accordance with a signal input by a microcomputer.

  In order to solve the above-mentioned problem, the motor control device according to claim 1 inputs a signal accompanying connection / disconnection of a switch connected to a power source, and the microcomputer controls the operation of the controlled object according to the input signal. Input signal misjudgment prevention applied to electronic control devices to control, preventing the microcomputer from misjudging the connection / disconnection of the switch according to the signal input from the switch due to the fluctuation of the power supply voltage of the power supply A comparison circuit that compares a power supply voltage of a power supply with a preset voltage threshold of the power supply voltage and outputs a voltage drop signal when the power supply voltage becomes less than the voltage threshold, A voltage signal indicating the magnitude of the voltage output from the switch is continuously input from the switch, and when the voltage drop signal output from the comparison circuit is input, the voltage drop signal is input. A holding circuit that holds a previously input voltage signal as a holding signal, a voltage signal output from a switch, and a holding signal output from a holding circuit are input, and the power supply voltage is equal to or higher than a voltage threshold value and a comparison circuit And a switching circuit that outputs a voltage signal to the microcomputer when the power supply voltage is normal and from which no voltage drop signal is output, and outputs a holding signal to the microcomputer when the power supply voltage drops when the voltage drop signal is output.

  According to this, the structure of the input signal error determination prevention circuit can be simplified by using the comparison circuit, the holding circuit, and the switching circuit. In the input signal error determination prevention circuit, when the power supply voltage is lowered, the comparison circuit can immediately output a voltage drop signal to the holding circuit and the switching circuit. As a result, the holding circuit to which the voltage drop signal is input immediately holds the voltage signal before the voltage drop signal is input and outputs the hold signal to the switching circuit. Further, the switching circuit to which the voltage drop signal is input can immediately supply the holding signal output from the holding circuit to the microcomputer. As a result, for example, when the power supply voltage fluctuates instantaneously due to vehicle cranking or the like and the power supply voltage decreases, that is, in a situation where there is a high possibility that the microcomputer erroneously determines the voltage signal input from the switch. It is possible to prevent the microcomputer from erroneously determining that the connection / disconnection state of the switch has changed although the connection / disconnection state of the switch has not changed.

It is the schematic which shows the structure of the electronic controller provided with the input signal erroneous determination prevention circuit. FIG. 2 is a circuit diagram illustrating an input signal error determination prevention circuit of FIG. 1. It is a time chart which shows the action | operation of the input signal misjudgment prevention circuit of FIG. 3 is a flowchart of a switch operation validity / invalidity determination program executed by the microcomputer of FIG. 1.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, an electronic control device 1 to which an input signal error determination prevention circuit 10 is applied includes a microcomputer 2. The microcomputer 2 has a CPU, ROM, RAM, timer, input / output port, and the like as main components, and inputs various signals described later to execute various programs including programs described later. The microcomputer 2 is supplied with a power supply voltage supplied from a power supply 3 mounted on a vehicle (not shown) via a power supply circuit 4. The power supply 3 outputs a power supply voltage V of about 24V, for example. The power supply circuit 4 steps down the power supply voltage V output from the power supply 3 to about 5 V, for example, and supplies it to the microcomputer 2.

  The microcomputer 2 operates the actuator 6 to be controlled in response to the connection / disconnection of the switch 5 connected to the power source 3. Here, the switch 5 is, for example, a shift switch provided in an automatic transmission mounted on the vehicle, and the actuator 6 is, for example, an electric motor or solenoid provided in an automatic transmission mounted on the vehicle. It is. In this case, the microcomputer 2 (that is, the electronic control unit 1) inputs a signal accompanying connection / disconnection of the switch 5 (for example, shift switch), and operates the actuator 6 (for example, solenoid) according to the input signal. Control.

  The microcomputer 2 is connected to an ON / OFF sensor 7 that detects the connection / disconnection state of the switch 5. The ON / OFF sensor 7 outputs a signal corresponding to the disconnection state (OFF state) and the contact state (ON state) of the switch 5 to the microcomputer 2. Furthermore, a voltage sensor 8 that detects the power supply voltage V of the power supply 3 is connected to the microcomputer 2. The voltage sensor 8 detects the magnitude of the power supply voltage V and outputs a signal representing the magnitude of the power supply voltage V to the microcomputer 2.

  The electronic control device 1 includes an input signal erroneous determination prevention circuit 10 connected between the microcomputer 2 and the switch 5. Hereinafter, the input signal error determination prevention circuit 10 will be described in detail.

  As shown in FIG. 2, the input signal error determination prevention circuit 10 includes a comparison circuit 11, a holding circuit 12, and a switching circuit 13. In the present embodiment, the comparison circuit 11 is a comparator circuit that outputs an inverted output signal obtained by inverting the output when the power supply voltage drops when the power supply voltage V becomes less than the voltage threshold L as the voltage drop signal Sa. The comparison circuit (comparator circuit) 11 compares the power supply voltage V of the power supply 3 with a preset voltage threshold L of the power supply voltage V, and when the power supply voltage V becomes less than the voltage threshold L, the voltage drop signal Sa Is output to the holding circuit 12 and the switching circuit 13.

  The comparison circuit (comparator circuit) 11 is connected to the power supply 3 via a resistance voltage dividing circuit including a first resistor 11a and a second resistor 11b, and the power supply voltage V is proportional (for example, about 1/5). Supplied. The comparison circuit 11 is configured such that the voltage threshold L is set by the connected constant voltage diode 11c (or other reference reference voltage (for example, about 1.8V)). Here, the magnitude of the voltage threshold L is set to about 9 V (1.8 V × 5 = 9 V), for example, based on a voltage drop when the vehicle is cranked.

  In the present embodiment, the holding circuit 12 is a latch circuit, for example, a one-stage latch circuit or a flip-flop circuit (including a multi-stage latch circuit). The holding circuit (latch circuit) 12 is continuously input from the switch 5 with a voltage signal S <b> 1 indicating the magnitude of the voltage output from the switch 5 in connection with the connection / disconnection. Here, the switch 5 is supplied with the power supply voltage V (high voltage) from the power supply 3. For this reason, the voltage signal S1 output from the switch 5 is passed through the resistance voltage dividing circuit 14 and the buffer IC 15. The resistance voltage dividing circuit 14 includes a first resistor 14a and a second resistor 14b, and steps down the power supply voltage V (for example, about 24V) to about 5V, for example. The buffer IC 15 adjusts and outputs the voltage signal S1 stepped down by the resistance voltage dividing circuit 14 to a high state (ie, 5V) or a low state (ie, 0V). Therefore, the voltage signal S1 input by the holding circuit 12 is in a high state or a low state.

  When the voltage drop signal Sa (inverted output signal) output from the comparator circuit (comparator circuit) 11 is input, the holding circuit (latch circuit) 12 before (before) the voltage drop signal Sa (inverted output signal) is input. Is held as a hold signal S2. Then, the holding circuit (latch circuit) 12 outputs a holding signal S2 to the switching circuit 13.

  In the present embodiment, the switching circuit 13 is a multiplexer circuit that switches one of the voltage signal S <b> 1 input from the switch 5 and the holding signal S <b> 2 input from the holding circuit 12 and outputs it to the microcomputer 2. The switching circuit (multiplexer circuit) 13 includes a voltage signal S1 output from the switch 5, more specifically, a voltage signal S1 output via the resistance voltage dividing circuit 14 and the buffer IC 15, and a holding circuit (latch circuit) 12. The output holding signal S2 is input. The switching circuit (multiplexer circuit) 13 receives the voltage drop signal Sa (inverted output signal) from the comparison circuit (comparator circuit) 11.

  Then, the switching circuit (multiplexer circuit) 13 is connected to the voltage when the power supply voltage V is equal to or higher than the voltage threshold L and the voltage drop signal Sa (inverted output signal) is not output from the comparison circuit (comparator circuit) 11. The signal S1 is output to the microcomputer 2. Further, the switching circuit (multiplexer circuit) 13 outputs the holding signal S2 to the microcomputer 2 when the power supply voltage drops when the voltage drop signal Sa (inverted output signal) is output. That is, when the voltage drop signal Sa (inverted output signal) is input from the comparison circuit (comparator circuit) 11, the switching circuit (multiplexer circuit) 13 outputs the holding signal S 2 from the state in which the voltage signal S 1 is output to the microcomputer 2. Switch to state.

  Next, the operation of the input signal error determination prevention circuit 10 will be described with reference to the time chart shown in FIG.

  When the power supply voltage V of the power supply 3 is normal or higher than the voltage threshold L (voltage threshold or higher), the comparison circuit (comparator circuit) 11 does not output the voltage drop signal Sa (inverted output signal) (Low state). . In this case, since the power supply voltage V is equal to or higher than the voltage threshold L (voltage threshold or higher), the voltage signal S1 output from the switch 5 has a high voltage (for example, 5 V) even if it is stepped down by the resistance voltage dividing circuit 14. . Therefore, the voltage signal S1 output via the buffer IC 15 is output to the holding circuit (latch circuit) 12 and the switching circuit (multiplexer circuit) 13 as a High state (for example, 5 V). Since the voltage drop signal Sa (inverted output signal) is not output from the comparison circuit (comparator circuit) 11, the holding circuit (latch circuit) 12 does not hold the voltage signal S1, and the switching circuit (multiplexer circuit) 13 The voltage signal S1 output from the switch 5 is output to the microcomputer 2. In this case, since the power supply voltage is normal and the switch 5 is in the contact state (ON state), the microcomputer 2 determines whether the actuator 6 is in response to the voltage signal S1 (High state) output from the switching circuit 13. Control the operation.

  When the power supply voltage is normal, for example, when the vehicle starts cranking from the idling stop state at time t1, the power supply voltage V may be lower than the voltage threshold L (less than the voltage threshold). When the power supply voltage drops, the comparator circuit (comparator circuit) 11 immediately outputs the voltage drop signal Sa (inverted output signal) to the holding circuit (latch circuit) 12 and the switching circuit (multiplexer circuit) 13 at time t1. In the holding circuit (latch circuit) 12, the voltage signal S1 is continuously input. Accordingly, when the holding circuit (latch circuit) 12 receives the voltage drop signal Sa (inverted output signal), the holding circuit (latch circuit) 12 immediately before inputting the voltage drop signal Sa (inverted output signal), that is, in terms of time from time t1. The voltage signal S1 input at the time of going back (in other words, when the power supply voltage is normal) is held as the holding signal S2. Then, the holding circuit (latch circuit) 12 immediately outputs the holding signal S2 (High state) to the switching circuit (multiplexer circuit) 13. When the voltage drop signal Sa (inverted output signal) is input, the switching circuit (multiplexer circuit) 13 immediately switches from the state of outputting the voltage signal S1 to the state of outputting the holding signal S2. Thereby, the switching circuit (multiplexer circuit) 13 outputs the holding signal S2 (High state) output from the holding circuit (latch circuit) 12 to the microcomputer 2 as an output signal.

  Here, for example, the voltage signal S1 output from the switch 5 when the power supply voltage is reduced during the cranking is such that the power supply voltage V is less than the voltage threshold L (less than the voltage threshold) and the resistance voltage is divided. Since the power supply voltage V is further stepped down (for example, stepped down to about 3V) by the circuit 14, it is output as a Low state via the buffer IC15. That is, in this case, although the switch 5 is in the contact state (ON state), the voltage signal S1 output from the switch 5 is in the Low state indicating that the switch 5 is in the off state (OFF state). Accordingly, when the microcomputer 2 inputs the voltage signal S1 (Low state) output from the switch 5 when the power supply voltage is lowered, the microcomputer 2 switches the switch 5 from the connected state (ON state) to the disconnected state (OFF state). There is a possibility of misjudging that it has been switched. In other words, due to the fluctuation of the power supply voltage V of the power supply 3, there is a possibility that the microcomputer 2 erroneously determines the connection / disconnection of the switch 5 according to the voltage signal S1 input from the switch 5.

  In contrast, the input signal error determination prevention circuit 10 outputs the holding signal S2 to the microcomputer 2 as an output signal when the power supply voltage is lowered. In this case, the output hold signal S2 matches the actual connection / disconnection state of the switch 5, that is, the contact state (ON state) of the switch 5. Therefore, it is possible to prevent the microcomputer 2 from erroneously determining the connection / disconnection state of the switch 5 due to the fluctuation of the power supply voltage V of the power supply 3. The microcomputer 2 controls the operation of the actuator 6 according to the contact state (ON state) of the switch 5 even when the power supply voltage is temporarily reduced due to, for example, cranking.

  Thus, for example, when cranking is completed from the state in which the switching circuit (multiplexer circuit) 13 of the input signal error determination preventing circuit 10 outputs the hold signal S2 to the microcomputer 2 when the power supply voltage is lowered, the time t2 The power supply voltage V of the power supply 3 returns to the voltage threshold L or higher. When the power supply voltage returns to normal, the comparison circuit (comparator circuit) 11 does not output the voltage drop signal Sa (inverted output signal). That is, the voltage drop signal Sa (inverted output signal) is in a low state. As a result, the switching circuit (multiplexer circuit) 13 switches from a state in which the holding signal S2 is output to the microcomputer 2 to a state in which the voltage signal S1 output from the switch 5 is output to the microcomputer 2.

  Here, an ON / OFF sensor 7 and a voltage sensor 8 are connected to the microcomputer 2. In the microcomputer 2, the switch 5 is in a contact state (ON state) based on a signal output from the ON / OFF sensor 7, and based on a signal output from the voltage sensor 8, for example, by cranking the vehicle, When the power supply voltage V continues to decrease for a time T or longer that the power supply voltage V is expected to continue to decrease, the operation of the switch 5 is invalidated. That is, the microcomputer 2 executes the “switch operation validity / invalidity determination” program shown in FIG. 4 to determine whether the operation of the switch 5 is valid or invalid. Hereinafter, the “switch operation validity / invalidity determination” program will be described.

  When the switch 5 is in the contact state (ON state) based on the signal output from the ON / OFF sensor 7, the microcomputer 2 performs “switch operation valid / invalid determination” at a predetermined short time interval in step S10. "Run the program repeatedly. In subsequent step S11, the microcomputer 2 acquires a detection signal representing the power supply voltage V of the power supply 3 from the voltage sensor 8, inputs the power supply voltage V, and proceeds to step S12. In step S12, the microcomputer 2 determines whether or not the time during which the power supply voltage V input in step S11 has decreased below the preset voltage threshold L continues for a preset time T or more. judge. Here, as described above, the voltage threshold L is set to about 9 V, for example. The time T is set based on, for example, the time for which cranking is continued, and is set to about 5 seconds, for example.

  In step S12, if the time during which the power supply voltage V is less than the voltage threshold L is equal to or longer than the time T, the microcomputer 2 determines “Yes” and proceeds to step S13. In step S13, the microcomputer 2 determines that the contact state (ON state) that is the connection / disconnection state of the switch 5 is invalid, proceeds to step S15, and temporarily ends the execution of the “switch operation validity / invalidity determination” program. Here, when the microcomputer 2 executes the “switch operation validity / invalidity determination” program and determines that the contact state (ON state) of the switch 5 is invalid, there is a state in which the power supply voltage V of the power supply 3 has decreased for some reason. Since the operation continues, for example, the operation of the actuator 6 is stopped.

  On the other hand, in step S12, the microcomputer 2 determines “No” if the power supply voltage V is equal to or higher than the voltage threshold L or the time during which the power supply voltage V is less than the voltage threshold L is less than the time T. Then, the process proceeds to step S14. In step S14, the microcomputer 2 determines that the contact state (ON state) that is the connection / disconnection state of the switch 5 is valid, proceeds to step S15, and temporarily ends the execution of the “switch operation validity / invalidity determination” program. Here, when the microcomputer 2 executes the “switch operation validity / invalidity determination” program and determines that the contact state (ON state) of the switch 5 is valid, the power supply voltage V is normal or the power supply voltage V of the power supply 3 is temporarily Therefore, the control of the operation of the actuator 6 is continued according to the voltage signal S1 or the hold signal S2 input via the input signal error determination prevention circuit 10.

  As can be understood from the above description, the input signal erroneous determination prevention circuit 10 of the present embodiment inputs a signal associated with connection / disconnection of the switch 5 connected to the power supply 3, and the microcomputer 2 according to the input signal. Is applied to the electronic control device 1 that controls the operation of the actuator 6 that is a control target, and the switch 5 according to the signal input from the switch 5 by the microcomputer 2 due to the fluctuation of the power supply voltage V of the power supply 3. An input signal misjudgment prevention circuit that prevents misjudgment of connection / disconnection of the power source 3 and compares the power source voltage V of the power source 3 with a preset voltage threshold value L of the power source voltage V. A comparison circuit (comparator circuit) 11 that outputs a voltage drop signal Sa when it becomes less than L, and a voltage signal S1 that represents the magnitude of the voltage that is output from the switch 5 in connection with the connection / disconnection are switched. 5, when the voltage drop signal Sa output from the comparator circuit (comparator circuit) 11 is input, the input voltage signal S1 is held as the hold signal S2 before the voltage drop signal Sa is input. Holding circuit (latch circuit) 12, voltage signal S1 output from switch 5, and holding signal S2 output from holding circuit (latch circuit) 12, and power supply voltage V is equal to or higher than voltage threshold L The voltage signal S1 is output to the microcomputer 2 when the power supply voltage is normal and the voltage drop signal Sa is not output from the comparator circuit (comparator circuit) 11. The hold signal is output when the power supply voltage is reduced when the voltage drop signal Sa is output. And a switching circuit (multiplexer circuit) 13 for outputting S2 to the microcomputer 2.

  According to this, the input signal erroneous determination prevention circuit 10 can be configured with a simple structure using the comparison circuit (comparator circuit) 11, the holding circuit (latch circuit) 12, and the switching circuit (multiplexer circuit) 13. . In the input signal misjudgment prevention circuit 10, the comparison circuit (comparator circuit) 11 immediately outputs a voltage drop signal Sa to the holding circuit (latch circuit) 12 and the switching circuit (multiplexer circuit) 13 when the power supply voltage drops. can do. As a result, the holding circuit (latch circuit) 12 to which the voltage drop signal Sa is input immediately holds the voltage signal S1 before the voltage drop signal Sa is input and outputs the hold signal S2 to the switching circuit (multiplexer circuit) 13. . Further, the switching circuit (multiplexer circuit) 13 to which the voltage drop signal Sa is input can immediately supply the holding signal S2 output from the holding circuit (latch circuit) 12 to the microcomputer 2. As a result, for example, a situation where the power supply voltage V fluctuates instantaneously due to vehicle cranking or the like, that is, the power supply voltage V decreases, that is, the voltage signal S1 input from the switch 5 by the microcomputer 2 may be erroneously determined. In a high situation, it is possible to prevent the microcomputer 2 from erroneously determining that the connection / disconnection state of the switch 5 has changed even though the connection / disconnection state of the switch 5 has not changed.

  In this case, the comparator circuit 11 can be a comparator circuit that outputs an inverted output signal obtained by inverting the output when the power supply voltage drops as the voltage drop signal Sa.

  According to this, since the comparison circuit 11 can be a comparator circuit with a simple structure, the structure of the input signal erroneous determination prevention circuit 10 can also be simplified. Further, since the structure can be simplified, the input signal error determination preventing circuit 10 can be downsized.

  In these cases, the holding circuit 12 can be a latch circuit (flip-flop circuit) that holds the voltage signal S1 input before the voltage drop signal Sa is input.

  According to this, the holding circuit 12 can be a latch circuit with a simple structure. In this case, the latch circuit only holds the voltage signal S1 prior to the input of the voltage drop signal Sa as the holding signal S2, so that it is not affected by fluctuations in the power supply voltage V. Therefore, for example, it is not necessary to configure the latch circuit in multiple stages in order to ensure stability. Thereby, the structure of the input signal error determination prevention circuit 10 can be simplified, and the input signal error determination prevention circuit 10 can be downsized.

  Further, in these cases, the switching circuit 13 may be a multiplexer circuit that switches to one of the voltage signal S1 input from the switch 5 and the holding signal S2 input from the holding circuit (latch circuit) 12 and outputs it to the microcomputer 2. it can.

  According to this, since the switching circuit 13 can be a multiplexer circuit with a simple structure, the structure of the input signal erroneous determination prevention circuit 10 can also be simplified. Further, since the structure can be simplified, the input signal error determination preventing circuit 10 can be downsized.

  In carrying out the present invention, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, in the above embodiment, the comparison circuit 11 is a comparator circuit, the holding circuit 12 is a latch circuit, and the switching circuit 13 is a multiplexer circuit. In this case, it is needless to say that the comparison circuit 11, the holding circuit 12, and the switching circuit 13 are not limited to the above circuits, and can be configured using other circuits. Even when another circuit is used, when the comparison circuit 11 outputs the voltage drop signal Sa and the holding circuit 12 inputs the voltage drop signal Sa, the voltage signal S1 is held as the holding signal S2 immediately, and the switching circuit 13 If the holding signal S2 can be output to the microcomputer 2 immediately after the voltage drop signal Sa is input, the same effect as in the above embodiment can be obtained.

  Further, in the above embodiment, the switch 5 is, for example, a shift switch of an automatic transmission, and the actuator 6 to be controlled is, for example, an electric motor or solenoid provided in the automatic transmission. Instead of this, the switch 5 may be, for example, a brake switch of a brake device, and the actuator 6 to be controlled may be, for example, an electric motor (pump) or solenoid provided in the brake device. Even in this case, the input signal error determination prevention circuit 10 can prevent the microcomputer 2 from erroneously determining the connection / disconnection state of the switch 5 (brake switch) when the power supply voltage is lowered.

DESCRIPTION OF SYMBOLS 1 ... Electronic control device, 2 ... Microcomputer, 3 ... Power supply, 4 ... Power supply circuit, 5 ... Switch, 6 ... Actuator, 7 ... ON / OFF sensor, 8 ... Voltage sensor, 10 ... Input signal misjudgment prevention circuit, 11 Reference circuit 11a: First resistor 11b: Second resistor 11c: Constant voltage diode 12: Holding circuit 13: Switching circuit 14: Resistance voltage divider circuit 14a: First resistor 14b: Second resistor , 15 ... Buffer IC, V ... Power supply voltage, L ... Voltage threshold, Sa ... Voltage drop signal, S1 ... Voltage signal, S2 ... Holding signal

Claims (4)

Input a signal associated with connection / disconnection of a switch connected to a power source, and the microcomputer is applied to an electronic control device that controls the operation of a controlled object according to the input signal,
An input signal misjudgment prevention circuit that prevents the microcomputer from misjudging the connection / disconnection of the switch according to the signal input from the switch due to fluctuations in the power supply voltage of the power supply. And
A comparison circuit that compares a power supply voltage of the power supply with a preset voltage threshold of the power supply voltage, and outputs a voltage drop signal when the power supply voltage becomes less than the voltage threshold;
When the voltage signal indicating the magnitude of the voltage output from the switch in connection with the connection / disconnection is continuously input from the switch, and the voltage drop signal output from the comparison circuit is input, the voltage A holding circuit that holds the voltage signal input before the input of the decrease signal as a holding signal;
The voltage signal output from the switch and the holding signal output from the holding circuit are input, and the power supply voltage is equal to or higher than the voltage threshold and the voltage drop signal is not output from the comparison circuit A switching circuit that outputs the voltage signal to the microcomputer when the voltage is normal and outputs the holding signal to the microcomputer when the power supply voltage is reduced when the voltage drop signal is output. Judgment prevention circuit. The comparison circuit is
The input signal error determination prevention circuit according to claim 1, which is a comparator circuit that outputs an inverted output signal obtained by inverting an output when the power supply voltage is lowered as the voltage drop signal. The holding circuit is
The input signal error determination prevention circuit according to claim 1, wherein the input signal error determination prevention circuit is a latch circuit that holds the voltage signal input before inputting the voltage drop signal. The switching circuit is
4. The multiplexer circuit according to claim 1, wherein the multiplexer circuit is switched to one of the voltage signal input from the switch and the holding signal input from the holding circuit and is output to the microcomputer. 5. Input signal misjudgment prevention circuit.

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