JP2017116277A - Plural-voltages determination circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plural-voltages determination circuit for sequentially selecting voltages to be input into a plurality of voltage input sections by a scanning system and determining whether each voltage exceeds a threshold value, the circuit allowing determination using a common comparator if determined threshold values of voltages input into the voltage input sections are different, which reduces the number of components and cost.SOLUTION: Adjusting and controlling the reference voltage of a comparator 41 according to a voltage input section being scanned makes the determination possible for a plurality of voltage input sections with different voltage determination threshold values, using a common current source and comparator 41.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multiple voltage determination circuit that determines whether or not a plurality of voltages generated by supplying a constant current to a load such as a plurality of types of water level electrodes used in a water heater or the like exceeds a threshold value.

  The applicant of the present application includes, for example, the following Patent Document 1 including a multiplexer that selects a water level detection signal input from a plurality of water level electrodes according to a selection control signal output from the control unit and outputs the signal to the control unit. A water level detection signal detection device is disclosed.

  The water level electrode (load) of this conventional detection device outputs, as a water level detection signal, a voltage generated when a constant current (for example, 10 μA) is passed between the water level electrode and ground or ground using water as a conductor (water resistance). Therefore, a plurality of water level electrodes are provided for each location where water level detection is required. As a result, when each water level electrode is immersed in water, the resistance value decreases and the voltage of the water level detection signal also drops, so the comparator determines whether the voltage of the water level detection signal has fallen below a predetermined threshold. By outputting the determination result to the control unit, the control unit can determine whether each water level electrode is immersed in water and its resistance value is smaller than the resistance value determination threshold based on the determination result.

JP 2014-109437 A

  By the way, resistance value detection objects such as antifreezing liquid that serves as a heat medium for heating, drain water that is neutralized by a neutralizer, and hot water for hot water supply often have different resistance values. The voltage generated when a current is passed changes.

  For example, the first water level electrode has a resistance value of 300 kΩ when there is water (when the electrode is immersed in water), and 500 kΩ when there is no water (when the electrode is not immersed in water). Assuming that the water level electrode has a resistance value of 100 kΩ when there is water and 300 kΩ when there is no water, when the constant current is 10 μA, the voltage generated at the first water level electrode is 3 V when there is water and no water On the other hand, the voltage generated at the second water level electrode is 1V when there is water and 3V when there is no water.

  Therefore, the determination threshold value of the voltage generated in the first water level electrode is, for example, 4 V (400 kΩ as the resistance value determination threshold value), and the determination threshold value of the voltage generated in the second water level electrode is, for example, 2 V (200 kΩ as the resistance value determination threshold value). In addition, a constant current source needs to be separately provided for each water level electrode, and a constant current source and a comparator for voltage determination need to be provided for each type of water level electrode.

  However, if a circuit is configured individually for each electrode, the number of parts increases, resulting in an increase in cost.

  Therefore, the present invention provides a multiple voltage determination circuit that determines whether each voltage exceeds a threshold while sequentially selecting voltages input to the plurality of voltage input units by a scan method, and is input to each voltage input unit. It is an object to reduce the number of parts and thus reduce the cost by making it possible to make a determination using a common comparator even when the determination thresholds of the voltages to be detected are different.

  In order to achieve the above object, a control unit, a multiplexer, and a comparison circuit are provided, and the multiplexer is selected from the plurality of voltage input units by a selection control signal from the plurality of voltage input units and the control unit. A voltage output unit that outputs a voltage according to the voltage input to the one voltage input unit, and the comparison circuit determines whether or not the voltage output from the voltage output unit exceeds a predetermined threshold value. In the multi-voltage determination circuit for determining, the present invention takes the following technical means.

  That is, the multiple voltage determination circuit of the present invention is characterized in that the comparison circuit is configured such that the threshold value can be adjusted and controlled by the control unit depending on which voltage input unit is selected. (Claim 1).

  According to the multiple voltage determination circuit of the present invention, even if the voltage determination threshold value is different for each voltage input unit, the determination threshold value of the comparison circuit is adjusted by the control unit depending on which voltage input unit is selected. By controlling, it is possible to accurately determine whether or not the voltage output from the voltage output unit exceeds a threshold corresponding to each voltage input unit using a common comparison circuit, and a constant current source and a comparator By sharing these, the number of parts can be reduced, and the cost can be reduced.

  Preferably, the multiplexer is configured such that one voltage input unit and the voltage output unit selected by the selection control signal are electrically connected, and the other voltage input unit and the voltage output unit are insulated from each other. A load such as a water level electrode is connected to the unit, and the constant current output from the constant current source connected to the voltage output unit is supplied to the load connected to the selected one voltage input unit via the multiplexer. A voltage corresponding to the resistance value of the load can be generated in one voltage input section.

  In the multiple voltage determination circuit of the present invention, the comparison circuit is configured such that the threshold value is adjusted based on a threshold control signal output from the control unit separately from the selection control signal, and the control unit includes: The threshold control signal can be output in accordance with the selection control signal. Preferably, the comparison circuit is configured such that the magnitude of the threshold is adjusted based on the selection control signal. (Claim 2). According to this, it is not necessary to output the threshold control signal separately from the selection control signal, the configuration of the control unit can be simplified, and the control unit can be connected to other products that do not employ the present invention. Sharing can be achieved, and thereby further cost reduction can be achieved.

  Further, at least one voltage input unit among the plurality of voltage input units is a constant voltage input unit to which a predetermined constant voltage is input, and the control unit receives the selection control signal for selecting the constant voltage input unit. Outputting the determination result of the comparison circuit when the comparison circuit is controlled so that the threshold value is larger than the constant voltage, and the selection control signal for selecting the constant voltage input unit and It is configured to determine whether or not a circuit failure has occurred based on whether or not the comparison result of the comparison circuit when the comparison circuit is controlled so that the magnitude of the threshold value is smaller than the constant voltage. (Claim 3). According to this, when the circuit is normal, the determination result of the comparison circuit when the threshold value is changed should be different, but when the determination result is the same, the comparison circuit or a circuit related thereto is faulty. When such a failure determination is made, the failure location can be accurately identified by notifying that the failure is related to the comparison circuit.

  As described above, according to the multiple voltage determination circuit of the present invention, a common constant current source and a comparator are used even when the determination threshold values of the voltages input to the multiple voltage input units are different. Therefore, it is possible to determine whether or not the threshold value is exceeded, and it is possible to reduce the number of parts and thus the cost.

It is a circuit diagram of the multiple voltage determination circuit which concerns on one Embodiment of this invention. It is a circuit diagram of the multiple voltage determination circuit which concerns on another embodiment of this invention. FIG. 3 is a circuit diagram showing a first application example of the circuit shown in FIG. 2. FIG. 3 is a circuit diagram showing a second application example of the circuit shown in FIG. 2. FIG. 6 is a circuit diagram showing a third application example of the circuit shown in FIG. 2. FIG. 6 is a circuit diagram showing a fourth application example of the circuit shown in FIG. 2. FIG. 10 is a circuit diagram showing a fifth application example of the circuit shown in FIG. 2. FIG. 10 is a circuit diagram illustrating a sixth application example of the circuit illustrated in FIG. 2.

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

  FIG. 1 shows a multiple voltage determination circuit according to an embodiment of the present invention, in which resistance values of various water level electrodes (loads) in a hot water supply apparatus similar to that disclosed in Patent Document 1 are determined for each resistance value. Determine whether or not the threshold is exceeded, that is, whether each water level electrode is immersed in water (with water) or not (without water) based on the voltage generated when a constant current is supplied to each water level electrode Therefore, it is preferably used.

  In the illustrated example, three first water level electrodes P1 and one second water level electrode P2 are shown, and the first water level electrode P1 (for example, the level of drain water stored in the neutralizer is monitored). The water level electrode or the like) has a resistance value of 300 kΩ when there is water (when immersed in water) and 500 kΩ when there is no water (when not immersed in water), and the second water level electrode P2 (for example, water leakage) The water level electrode for detection, etc.) has a resistance value of 100 kΩ when there is water and 300 kΩ when there is no water, the resistance value judgment threshold value of the first water level electrode P1 is 400 kΩ, and the resistance value judgment of the second water level electrode P2 The threshold is 200 kΩ. In addition to the water level electrodes P1 and P2, a fixed resistor Ra is connected as a dummy load to an empty port of the multiplexer 3 described later. The above resistance values are merely examples for understanding the present invention, and can be designed as appropriate resistance values.

  The multiple voltage determination circuit of the present embodiment includes a constant current source 1 and a microprocessor 2 as a control unit that outputs a selection control signal for selecting any one of the plurality of loads P1, P2, and Ra. A multiplexer 3 (switching circuit) for supplying a constant current output from the constant current source 1 to the one load selected by the selection control signal, and the one load to which the constant current is supplied And a comparison circuit 4 for determining whether or not the voltage level generated in the circuit exceeds a predetermined threshold value and outputting the determination result signal to the microprocessor 2.

  The constant current source 1 outputs a constant current of, for example, 10 μA. In the illustrated example, the operational amplifier 11, a pnp transistor 12 whose base is connected to the output of the operational amplifier 11, the emitter of the transistor 12, and the power source And an output side load resistor 13 connected to (15V), and the emitter of the transistor 12 is connected to the inverting input terminal (−) of the operational amplifier 11 to constitute a negative feedback circuit. Further, a voltage for setting a predetermined output current output from the voltage dividing circuit 14 is input to the non-inverting input terminal (+) of the operational amplifier 11, and the voltage of the inverting input terminal (−) due to a virtual short circuit of the operational amplifier 11. And the voltage at the non-inverting input terminal (+) become the same potential, whereby the voltage across the output load resistor 13 is determined, the current flowing through the resistor 13 and the transistor 12 is determined, and the constant current is obtained from the collector output of the transistor 12. It is output.

  The microprocessor 2 is also responsible for various types of hot water supply operation control, heating operation control, and reheating operation control of the hot water supply device. FIG. 1 shows only the input / output ports related to the present invention. In the present embodiment, the selection control signal is constituted by a 3-bit logic signal output from three output ports (A output port, B output port, and C output port) of the microprocessor 2, and the selection control signal The signals are respectively input to the corresponding three control signal input ports (A, B, C) of the multiplexer 3.

  The multiplexer 3 may be an analog switch type that is commercially available in the form of a one-chip LSI, or may be configured on a substrate using a general-purpose logic gate circuit. The multiplexer 3 of this embodiment includes eight input / output ports (voltage input units) of Nos. 0 to 7 and one common port COM (voltage output unit), and control signal input ports A, B, C 1 is connected to the common port COM, and the other input / output ports are isolated from the common port COM. It is configured as follows. The three first water level electrodes P1 are connected to the 0-2 input / output ports of the multiplexer 3, and the second water level electrode P2 is connected to the 4th input / output port. A fixed resistor Ra is connected to the seventh input / output port. The input / output port connecting the second water level electrode P2 may be an appropriate port. The load connected to the input / output port selected by the selection control signal (also referred to as “the load selected by the selection control signal” in this specification) has a constant current output from the constant current source 1. Is supplied via the multiplexer 3, a detection voltage corresponding to the resistance value of each load is input to the input / output port to which the load is connected, and the detection voltage is output from the common port COM.

  The comparison circuit 4 includes a comparator 41 and a voltage dividing circuit that outputs a predetermined reference voltage (threshold value) for determination to the negative input terminal of the comparator 41, and is output from the common port COM. The detection voltage is input to the positive input terminal of the comparator 41.

  The voltage dividing circuit includes three resistors R1, R2, and R3 connected in series, and includes an npn transistor Q1 as a switching element that bypasses the resistor R3 when turned on. The transistor Q1 When the transistor Q1 is turned on, a voltage (for example, 2V) obtained by dividing the power supply voltage (15V) by the two resistors R1 and R2 is input to the negative input terminal of the comparator 41 as a reference voltage. A voltage divided by the resistance value of R1 and the combined resistance value of the two resistors R2 and R3 (for example, 4V) is input to the negative side input terminal of the comparator 41. If the voltage output from the common port COM exceeds the reference voltage, the determination signal output from the comparator 41 is a high signal. If the detection voltage output from the common port COM does not exceed the reference voltage, the comparison signal is output. The determination signal output from the device 41 is a Low signal. The determination signal output from the comparator 41 is input to the scan input port of the microprocessor 2.

  The microprocessor 2 switches the content of the selection control signal at predetermined time intervals (for example, several milliseconds to several tens of milliseconds) so as to repeatedly select the input / output ports 0 to 7 sequentially and scan input at each time point. A determination signal input from the port is stored in the storage unit for each input / output port, and the determination signal is used as a parameter for various operation controls. The transistor Q1 of the voltage dividing circuit is configured to be turned on / off by a threshold control signal output from a threshold control signal output port of the microprocessor 2, and the microprocessor 2 has a second water level. The transistor Q1 is turned on when a selection control signal (A: 1, B: 0, C: 0) for selecting the fourth input / output port connected to the electrode P2 is output, and the transistor Q1 is output when other selection control signals are output. Is controlled so that the determination reference voltage (threshold value) of the comparison circuit 4 is set to 2 V when the voltage of the second water level electrode P2 is detected, and the reference voltage is set when the voltages of the first water level electrode P1 and the fixed resistor Ra are detected. Control to 4V.

  With this control, when the water level electrode P1 is selected, a voltage of 300 kΩ × 10 μA = 3 V is output from the common port COM when there is water, and 500 kΩ × 10 μA = 5 V is output from the common port COM when there is no water. A voltage of 300 kΩ × 10 μA = 3 V is output from the common port COM when there is no water, but the voltage determination threshold (reference voltage) of the comparator 41 is controlled appropriately for each of the water level electrodes P1 and P2. Thus, it is determined whether the voltage generated at the water level electrode P1 by the common comparator 41 exceeds the voltage determination threshold value of 4V, and the voltage generated at the water level electrode P2 is set at 2V as the voltage determination threshold value. It is also possible to determine whether or not it has exceeded, thereby simplifying the circuit configuration, reducing the number of parts, and thus reducing costs. Rukoto can.

  Further, in the present embodiment, by connecting the fixed resistor Ra to the input / output port of the multiplexer 3 not connected to the water level electrode, the port scan control by the microprocessor 2 is controlled to be performed for all the input / output ports. The scan control software of the microprocessor 2 can be shared with other products.

  In addition, by using the fixed resistor Ra, an abnormality of the comparison circuit 4 and related circuits (floating of the threshold control signal output port of the microprocessor 2 or defective connection wiring, etc.) may be detected by the control method described below. it can. The abnormality detection control will be described in detail. When the resistance value of the fixed resistor Ra is, for example, 330 kΩ, selection control for selecting any input / output port (constant voltage input unit) to which the fixed resistor Ra is connected. If a signal is output, the input voltage of the input / output port and the output voltage from the common port COM become a constant voltage of 3.3V. Therefore, when the comparison circuit 4 is controlled such that the voltage determination threshold value (reference voltage) of the comparison circuit 4 is 4 V, which is larger than the constant voltage, the comparison circuit 4 becomes a Low output. On the other hand, when the comparison circuit 4 is controlled so that the voltage determination threshold value (reference voltage) of the comparison circuit 4 is 2 V, which is smaller than the constant voltage, the comparison circuit 4 becomes High output.

  However, when an abnormality such as an open failure of the components and wirings constituting the comparison circuit 4 occurs, for example, when the switching element Q1 is open, the voltage determination threshold value of the comparison circuit 4 is fixed at 4 V regardless of the content of the threshold control signal. Therefore, even if the High signal is output to the switching element Q1 as the threshold control signal so that the voltage determination threshold is 2V, the output of the comparison circuit 4 when the fixed resistor Ra is selected is constantly Low output.

  Therefore, the comparison circuit 4 is controlled when the comparison circuit 4 is controlled so that the voltage determination threshold value becomes 4V and the comparison circuit 4 is controlled so that the voltage determination threshold value becomes 2V while the fixed resistor Ra is selected. By configuring the microprocessor 2 so as to determine whether or not there is a circuit failure in the comparison circuit 4 or the like based on whether or not the determination results (output signals) are different, the circuit failure in the comparison circuit 4 or the like is detected. It can be detected accurately.

  In addition, when the switching element Q1 is short-circuited, the voltage determination threshold value of the comparison circuit 4 is fixed at 2V. In this case as well, the determination result of the comparison circuit 4 is constant regardless of the threshold control signal. It can be determined that there is a circuit failure.

  When a plurality of fixed resistors Ra are attached, the voltage determination threshold is controlled to 4V when scanning any one of the fixed resistors Ra, while the voltage determination threshold is 2V when scanning other fixed resistors Ra. It is possible to make a failure determination based on whether or not the determination results of the comparison circuit 4 in each case are different. It is also possible to change the voltage determination threshold at each scan timing for one fixed resistor Ra, and to make a failure determination depending on whether the determination result is different. Further, when one scan time for one fixed resistor Ra is sufficiently long, it is possible to make a failure determination by changing a voltage determination threshold during the one scan.

  FIG. 2 shows a multiple voltage determination circuit according to another embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals and detailed description thereof is omitted. explain.

  In the multiple voltage determination circuit of the present embodiment, each bit of the selection control signal output from the microprocessor 2 is inverted and input to the control signal input ports A to C of the multiplexer 3, respectively. The relationship between the output signal of the processor 2 and the selected input / output port is as shown in the table of FIG.

  Further, in the present embodiment, the input of the comparator 41 of the comparison circuit 4 is inverted from that of the embodiment shown in FIG. 1, the output voltage of the common port COM of the multiplexer 3 is input to the negative input terminal, and the positive input The output voltage of the voltage divider circuit is input to the terminal. The output voltage of the voltage dividing circuit when the switching element Q1 is on (voltage determination threshold of the comparison circuit 4) is 4V, the output voltage of the voltage dividing circuit when the switching element Q1 is off is 7V, The water level electrode P2 exhibits a resistance value of 500 kΩ when there is water, shows a resistance value of 900 kΩ when there is no water, the resistance value determination threshold is 700 kΩ, and a voltage determination threshold as a voltage generated when a current of 10 μA is supplied. Is 7V.

  Based on the selection control signal output from the microprocessor 2, the switching element Q1 of the comparison circuit 4 (in this embodiment, only in the case where the fourth input / output port to which the second water level electrode P2 is connected is selected). FET) is turned off to set the voltage judgment threshold (reference voltage) of the comparison circuit 4 to 7V. When other input / output ports are selected, the switching element Q1 is turned on to set the voltage judgment threshold of the comparison circuit 4 to 4V. The circuit configuration is as follows.

  That is, the control signal input terminal (gate) of the switching element Q1 is connected to the control power supply (5V) via the pull-up resistor R4 and is connected to the ground via the switching element Q3 (FET in the illustrated example). When the switching element Q3 is off, the gate of the switching element Q1 is pulled up and the switching element Q1 is turned on. When the switching element Q3 is on, the gate of the switching element Q1 is grounded and the switching element Q1 is Turn off.

  The control signal input terminal (gate) of the switching element Q3 is connected to the control power supply (5V) via the pull-up resistor R5, and the switching element Q2 (npn type transistor in the illustrated example, preferably a digital transistor). When the switching element Q2 is off, the gate of the switching element Q3 is pulled up to turn on the switching element Q3. When the switching element Q2 is on, the gate of the switching element Q3 is grounded. The switching element Q3 is turned off.

  The gate of the switching element Q3 is connected to the A output port of the selection control signal through the back electromotive voltage prevention diode D1 and the load resistor R6, and is selected through the back electromotive voltage prevention diode D2 and the load resistor R7. It is connected to the B output port of the control signal. As a result, if either the A output port or the B output port is Low output, the gate of the switching element Q3 is grounded through the output port so that the switching element Q3 is turned off and the switching element Q1 is turned on. It has become. Further, the control signal input terminal (base) of the switching element Q2 is connected to the C output port, and is on / off controlled by a signal output from the C output port.

  With this circuit configuration, the switching element Q1 is turned off only when the A output port is High output, the B output port is High output, and the C output port is Low output, that is, only when the fourth input / output port is selected. Thus, the voltage determination threshold value of the comparison circuit 4 becomes 7V. In other cases, the switching element Q1 is turned on and the voltage determination threshold value becomes 4V.

  According to this embodiment, when a selection control signal for selecting a predetermined load (second water level electrode) is output, the voltage determination threshold value of the comparison circuit 4 can be adjusted based on the selection control signal itself. The control configuration of the microprocessor 2 can be simplified, the existing microprocessor 2 can be used as it is, and the voltage determination threshold value can be adjusted only by adding the logic circuit. There is no need to add an output port.

  Further, according to the above circuit configuration, when each input / output port is selected depending on whether each of the switching elements Q2, Q3 and the resistors R6, R7 are mounted on the substrate or not, the switching element Q1 is selected. You can change the variation of turning on.

  For example, as shown in FIG. 3, when neither of the load resistors R6 and R7 is mounted, the switching element Q1 is turned on / off depending only on the on / off of the switching element Q2, so that the C output port has a high output. When the switching element Q1 is ON, the switching element Q1 is turned OFF, and when the C output port is LOW output, the switching element Q1 is OFF. Therefore, in the example shown in FIG. 3, the first water level electrode P1 can be connected to the 0-3rd input / output port, and the second water level electrode P2 can be connected to the 4th-7th input / output port.

  As shown in FIG. 4, when only the load resistor R7 is not mounted, the first water level electrode P1 can be connected to the 0th, third, fifth and seventh input / output ports, and the fourth and sixth input / output ports. To the second water level electrode P2.

  Further, as shown in FIG. 5, when the switching element Q2 and the load resistor R6 are not mounted, the first water level electrode P1 can be connected to the second, third, sixth and seventh input / output ports. The second water level electrode P2 can be connected to the 4th and 5th input / output ports.

  Further, as shown in FIG. 6, when only the load resistor R6 is not mounted, the first water level electrode P1 can be connected to the 0th, 3rd, 6th, and 7th input / output ports, and the 4th, 5th input / output ports. To the second water level electrode P2.

  Further, as shown in FIG. 7, when only the switching element Q2 is not mounted, the first water level electrode P1 can be connected to the 1st, 3rd, 5th and 7th input / output ports, and the 0th and 4th input / output ports. To the second water level electrode P2.

  In addition, as shown in FIG. 8, when the switching element Q2 and the load resistor R7 are not mounted, the first water level electrode P1 can be connected to the first, third, fifth and seventh input / output ports. The second water level electrode P2 can be connected to the 4th and 6th input / output ports.

  In place of not mounting the resistors R6, R7 or the switching element Q2 on the substrate, a circuit configuration substantially similar to the above is provided depending on whether or not each jumper wire is cut by providing jumper wires at appropriate locations. It is also possible.

  The present invention is not limited to the above-described embodiments, and the design can be changed as appropriate. For example, the multiple voltage determination circuit according to the above embodiment can be suitably applied to other appropriate hot water heaters, hot water heaters, and the like in addition to the same hot water supply apparatus as that disclosed in Patent Document 1.

  In the above-described embodiment, the multiplexer 3 is one that can be switched to one of eight input / output ports by a 3-bit selection control signal. However, two or more input / output ports can be switched by an appropriate selection control signal. Anything is acceptable. The multiplexer 3 includes a plurality of voltage input ports (voltage input units) and a common voltage output port, and a voltage (input) corresponding to a voltage input to one voltage input port selected by the selection control signal. Any device that outputs the same voltage as the voltage or a voltage proportional to the input voltage from the common voltage output port, and electrically isolates the selected voltage input port from the output port. In this case, the voltage is derived from the power supply voltage of the multiplexer 3, and the voltage corresponding to the input voltage to the one voltage input port is output from the common voltage output port, and the voltage is supplied to each load. An appropriate circuit configuration can be obtained, for example, by providing a constant current source for generating voltage on the voltage input port side of the multiplexer 3.

2 Control unit 3 Multiplexer 4 Comparison circuit P1 Load (first water level electrode)
P2 load (second water level electrode)
Ra load (fixed resistance)

Claims (3)

A control unit, a multiplexer, and a comparison circuit;
The multiplexer includes a plurality of voltage input units and a voltage output unit that outputs a voltage corresponding to a voltage input to one voltage input unit selected from the plurality of voltage input units by a selection control signal from the control unit. And
In the multiple voltage determination circuit, the comparison circuit determines whether or not the voltage output from the voltage output unit exceeds a predetermined threshold.
The multiple voltage determination circuit, wherein the comparison circuit is configured such that the threshold value can be adjusted and controlled by the control unit depending on which voltage input unit is selected.   2. The multiple voltage determination circuit according to claim 1, wherein the comparison circuit is configured such that the threshold value is adjusted based on the selection control signal.   3. The multiple voltage determination circuit according to claim 1, wherein at least one of the plurality of voltage input units is a constant voltage input unit to which a predetermined constant voltage is input, and the control unit includes A determination result of the comparison circuit when the comparison circuit is controlled so that the selection control signal for selecting a constant voltage input unit is output and the threshold value is larger than the constant voltage, and the constant voltage input unit Based on whether the determination result of the comparison circuit is different when the comparison circuit is controlled so that the selection control signal is selected and the threshold value is controlled to be smaller than the constant voltage. A multi-voltage determination circuit configured to determine whether or not there is a failure.

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