JP2019004553A - Erroneous connection detection circuit - Google Patents

Abstract

To provide an erroneous connection detection circuit capable of detecting an erroneous connection of a feed line in a system where multiple different power supply voltages coexist.SOLUTION: An erroneous connection detection circuit 100 comprises: a first resistor R1 which is connected in series between a first voltage system load group driven by a first voltage and a first power source 11 for supplying power to the first voltage system load group; protection means 15 which is connected in parallel with a second voltage system load group driven by a second voltage lower than the first voltage, between the second voltage system load group and a second power source 13 for supplying power to the second voltage system load group, passes a current when a third voltage higher than the second voltage is applied, and protects the second voltage system load group; and determination means 16 which determines whether or not the third voltage is applied to the protection means 15.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an erroneous connection detection circuit.

  2. Description of the Related Art Conventionally, an apparatus that can prevent an incorrect connection of a power feeding path between a power source and a load is known. For example, in Patent Document 1, a primary side connection part and a secondary side connection part can be easily connected by an opening / closing means, and when an overcurrent flows between the two connection parts, the opening / closing means is forced A circuit breaker that can be opened to prevent damage to the device is disclosed.

JP 2009-163963 A

  The circuit breaker disclosed in Patent Document 1 is based on the premise that there is only one type of power supply voltage of the connected load. For this reason, it cannot be applied to a system in which a plurality of different power supply voltages are mixed.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an erroneous connection detection circuit capable of detecting an erroneous connection of a power feeding path in a system in which a plurality of different power supply voltages are mixed.

In order to achieve the above object, an erroneous connection detection circuit according to the present invention includes:
A first resistor connected in series between a first voltage system load group driven by a first voltage and a first power supply for supplying power to the first voltage system load group;
In parallel with the second voltage system load group between a second voltage system load group driven by a second voltage lower than the first voltage and a second power source for supplying power to the second voltage system load group. Protection means connected to protect the second voltage system load group by passing a current when a third voltage higher than the second voltage is applied;
Determination means for determining whether or not the third voltage is applied to the protection means;
Is provided.

  According to the present invention, it is possible to determine whether or not an overvoltage is applied while protecting a load group from an overvoltage. Therefore, in a system in which a plurality of different power supply voltages are mixed, an erroneous connection of a power supply path is detected. be able to.

The block diagram showing the example of 1 structure of the misconnection detection circuit which concerns on Embodiment 1 of this invention The figure showing the internal structural example of the determination means which concerns on Embodiment 1. FIG. The figure explaining the change of the voltage in the measurement point VC in the misconnection detection circuit based on Embodiment 1, and the determination result by a determination means. The figure explaining the case where a misconnection arises in one structural example of the misconnection detection circuit which concerns on Embodiment 1. FIG. The figure explaining the change of the voltage in the measurement point VC, and the determination result by a determination means when an incorrect connection arises in the incorrect connection detection circuit which concerns on Embodiment 1. FIG. FIG. 6 is a diagram for explaining an equivalent circuit when an erroneous connection occurs in the configuration example of the erroneous connection detection circuit according to the first embodiment. The block diagram showing the example of 1 structure of the misconnection detection circuit based on Embodiment 2 of this invention The figure explaining the equivalent circuit when the misconnection has arisen in the structural example of the misconnection detection circuit which concerns on Embodiment 2. FIG. The block diagram showing the example of 1 structure of the misconnection detection circuit which concerns on the modification 2 of this invention

  Hereinafter, an erroneous connection detection circuit according to an embodiment of the present invention will be described in detail with reference to the drawings. In this case, the same or corresponding parts are denoted by the same reference numerals in the drawings.

(Embodiment 1)
As shown in FIG. 1, the erroneous connection detection circuit 100 according to the first embodiment of the present invention includes a first resistor R1, a 12V power supply 13 and a 12V connected in series between a 24V power supply 11 and a 24V system load 12. A second resistor R2 connected in series with the system load 14 and a protection unit 15 and a determination unit 16 connected in parallel with the 12V system load 14 are provided. Here, 24V is also referred to as a first voltage, and 12V is also referred to as a second voltage. The negative terminal of the first power source and the negative terminal of the second power source are connected to a common ground. The ground can be considered as a reference potential = 0 V. In this case, the potential value at any point in the circuit and the voltage between the point and the ground have the same value, and thus the present specification. Then, the potential is also referred to as voltage.

  The 24V power supply 11 is a DC power supply that supplies a voltage of 24V to the 24V system load 12. The 24V power supply 11 is also called a first power supply. As shown in FIG. 1, an arbitrary number of 24V system loads 12 can be connected in parallel, and the plurality of 24V system loads 12 are referred to as a 24V system load group or a first voltage system load group. The 24V system load 12 is an arbitrary circuit or device driven by 24V. In addition, the circuit by 24V power supply 11 and 24V system load group is called a 24V system circuit or a 1st voltage system circuit.

  The 12V power supply 13 is a DC power supply that supplies a 12V voltage to the 12V system load 14. The 12V power supply 13 is also called a second power supply. As shown in FIG. 1, any number of 12V system loads 14 can be connected in parallel, and the plurality of 12V system loads 14 are referred to as a 12V system load group or a second voltage system load group. The 12V system load 14 is an arbitrary circuit or device driven by 12V. Note that a circuit composed of the 12V power supply 13 and the 12V system load group is referred to as a 12V system circuit or a second voltage system circuit.

  The first resistor R1 is a resistor connected in series between the 24V power supply 11 and the 24V system load 12. When an erroneous connection occurs between the first voltage system circuit and the second voltage system circuit, the value of the current flowing into the protection unit 15 is suppressed by the first resistor R1 to prevent the protection unit 15 from being destroyed. The second resistor R <b> 2 is a resistor connected in series between the 12V power supply 13 and the 12V system load 14. When an erroneous connection occurs between the first voltage system circuit and the second voltage system circuit, the value of the current flowing back to the 12V power supply 13 is suppressed by the second resistor R2, and the 12V power supply 13 is prevented from being destroyed.

  Due to the voltage drop caused by the first resistor R1 and the second resistor R2, the voltages applied to the 24V load group and the 12V load group are lower than 24V and 12V, respectively. However, if the current consumption of the 24V system load group and the 12V system load group is small, this voltage drop is small, so that there is not much problem. For example, when the resistance value of the first resistor R1 is 100Ω and the current consumption of the 24V system load group is 1 mA, the voltage drop due to the first resistor R1 is 100Ω × 1 mA = 0.1V. The voltage drop due to the second resistor R2 is also affected by the current consumption of the protection means 15 and the determination means 16, but as will be described later, when no erroneous connection occurs, the current consumption of the protection means 15 is also determined by the determination means. The current consumption of 16 can also be considerably reduced. Therefore, when no erroneous connection occurs, the voltage drop due to the second resistor R2 is small when the current consumption of the 12V system load group is small, as in the first resistor R1.

  When a high voltage (for example, 24V) is applied to the 12V system load 14, the protection unit 15 keeps (clamps) the voltage applied to the protection unit 15 by allowing a current to pass therethrough. Protect the load 14. Here, the constant voltage is referred to as a third voltage. The third voltage is higher than the second voltage (12V) and lower than the first voltage (24V), but is preferably set to about 14V in consideration of protection of the 12V system load 14. Here, the third voltage is 14V. The protection means 15 can be realized by using a Zener diode whose Zener voltage is the third voltage. When the protection means 15 is realized by a Zener diode, when the voltage less than the third voltage is applied to the 12V system load 14, almost no current flows through the Zener diode, so that the consumption current of the protection means 15 is regarded as 0. Can do.

  The determination unit 16 determines whether or not the third voltage is applied to the protection unit 15. Since the determination unit 16 is connected in parallel with the protection unit 15, this determination is the same as the determination of whether or not the third voltage is applied to the determination unit 16. As shown in FIG. 2, the determination unit 16 includes a comparison unit 161 and a display unit 162. The comparison unit 161 compares the voltage applied to the determination unit 16 with the threshold voltage. The threshold voltage is set to a value higher than the second voltage (12V) and lower than the third voltage (14V). Here, this threshold voltage is set to 13V. By setting the threshold voltage in this way, it is possible to stably detect the presence or absence of a misconnection even if there is some variation in the clamp voltage by the protection means 15.

  The display part 162 displays the comparison result by the comparison part 161 by light emission of LED (Light Emitting Diode). The user can know whether or not a misconnection has occurred by the light emission of the LED of the display unit 162.

  The comparison unit 161 can be realized by a comparator circuit that compares the voltage applied to the determination unit 16 with a threshold voltage (13 V). The comparison unit 161 functions as a comparison unit. Further, when the voltage applied to the determination unit 16 by the comparator circuit is determined to be equal to or higher than the threshold voltage (13V), the display unit 162 causes the red LED to emit light, and when the voltage is determined to be less than the threshold voltage (13V). This can be realized by a circuit for emitting a green LED. The display unit 162 functions as a display unit.

  In order to suppress the current consumption of the determination means 16 when no erroneous connection occurs, the display unit 162 emits a red LED only when an erroneous connection occurs, and emits an LED when no erroneous connection occurs. You don't have to. If the LED is not caused to emit light when there is no erroneous connection, the current consumed by the determination means 16 when there is no erroneous connection is only the current consumed by the comparator circuit. Although the current consumption of the comparator circuit depends on how the comparator circuits are assembled, for example, by using a low power consumption comparator IC, it can be suppressed to about several tens of μA.

  In the above circuit, the 24V system circuit operates at 24V, the 12V system circuit operates at 12V, and the 24V system circuit and the 12V system circuit are independent. Accordingly, the voltage at the measurement point VC in FIG. 1 is the second voltage (12V), no current flows through the protection means 15, and the display unit 162 of the determination means 16 causes the green LED to emit light (or does not cause the LED to emit light). ). As shown in FIG. 3, the voltage at the measurement point VC after power-on at this time rises from 0V to 12V as indicated by the solid line L1, and the erroneous connection determination result by the determination means 16 is as indicated by the solid line L2. It is determined that there is no erroneous connection. In practice, the voltage at the measurement point VC is smaller than 12 V due to the voltage drop caused by the second resistor R2. However, here, the current consumption of the 12V system load 14, the protection means 15, and the determination means 16 are all very small, and the voltage drop due to the second resistor R2 can be ignored.

  Then, as shown in FIG. 4, when an erroneous connection due to the conductive wire 17 occurs between the 24V system circuit and the 12V system circuit, the first voltage of 24V is applied to the 12V system load 14. Then, the voltage at the measurement point VC in FIG. 4 rises more steeply than the solid line L1 and rises above 12V, as shown by the solid line L3 in FIG. If the protection means 15 is not present, the voltage at the measurement point VC increases toward 24V as shown by the dotted line L4, but the voltage at the measurement point VC is clamped to 14V by the protection means 15 as shown by the solid line L5. When the voltage at the measurement point VC becomes 13 V or more, the erroneous connection determination result by the determination means 16 is determined as “incorrect connection” as indicated by the solid line L6. At this time, the display unit 162 of the determination unit 16 causes the red LED to emit light. In the same manner as described above, the voltage applied to the 12V system load 14 when an erroneous connection due to the conducting wire 17 actually occurs is smaller than 24V due to the voltage drop caused by the first resistor R1. However, here, the current consumption of the 24V system load 12 is also very small like the current consumption of the 12V system load 14, the protection unit 15 and the determination unit 16, and the voltage drop due to the first resistor R1 can be ignored.

When the current consumption of the 24V system load 12, the 12V system load 14 and the determination unit 16 is very small, the current flowing into the 24V system load 12, the 12V system load 14 and the determination unit 16 even when the lead wire 17 is erroneously connected is Very little. Therefore, FIG. 6 shows an equivalent circuit at the time of erroneous connection when it is assumed that the current flowing into them is small enough to be ignored. In FIG. 6, the voltage VP at the measurement point VC when no current flows into the protection means 15 can be expressed by the following equation (1). In the following equations and description, the resistance value of the first resistor R1 is represented by R1, and the resistance value of the second resistor R2 is represented by R2.
VP = 12V + (24V-12V) × R2 / (R1 + R2) (1)

  Then, if VP <14V, no current flows through the protection means 15, and the voltage at the measurement point VC becomes VP. If VP ≧ 14V, a current flows through the protection means 15 and the voltage at the measurement point VC is clamped at 14V.

In FIG. 6, a reverse current I2 flows through the 12V power supply 13. When VP <14V, the value of the current I2 can be expressed by the following formula (2).
I2 = (24V-12V) / (R1 + R2) (2)

Further, when VP ≧ 14V, the voltage of the measurement point VC is clamped to 14V by the protection means 15, and therefore the value of the current I2 can be expressed by the following equation (3).
I2 = (14V-12V) / R2 (3)

  It is desirable that the resistance values of the first resistor R1 and the second resistor R2 are as small as possible in that the voltage drop due to these resistors can be minimized. However, if these resistance values are too small, the value of the current I2 becomes large, which adversely affects the 12V power supply 13. In order to minimize the adverse effect on the 12V power supply 13, the resistances of the first resistor R1 and the second resistor R2 so that VP ≧ 14V in the equation (1) so that a current flows through the protection means 15 at the time of incorrect connection. It is necessary to set a value. In the equation (3), it is necessary to set the resistance value of the second resistor R2 so that the current I2 is as small as possible.

  For example, if the 12V power supply 13 can withstand reverse current up to 0.1 A without any problem, the resistance value of the second resistor R2 needs to be set to 20Ω or more based on the equation (3). For example, when the resistance value of the second resistor R2 is set to 20Ω, the resistance value of the first resistor R1 is set to 12V + (24V−12V) × 20Ω / (R1 + 20Ω) ≧ 14V based on the formula (1). Must be set to 100Ω or less. When the resistance value of the first resistor R1 is set to 100Ω, a current of (24V−14V) /100Ω=0.1A flows into the protection means 15 at the time of erroneous connection. Therefore, if the withstand current value of the protection means 15 is less than 0.1 A, the value of 10 V / R1 is equal to or less than the withstand current value of the protection means 15 while satisfying VP ≧ 14 V in the above equation (1). In addition, it is necessary to increase the resistance values of the first resistor R1 and the second resistor R2.

  The user configures the erroneous connection detection circuit 100 by setting the resistance values of the first resistor R1 and the second resistor R2 as described above. Then, even if an erroneous connection occurs between the 24V system circuit and the 12V system circuit, the 12V system load 14 is protected by the protection means 15 of the erroneous connection detection circuit 100, and an erroneous connection occurs by the determination means 16. Is detected. The user can know whether or not an erroneous connection has occurred by turning on the LED of the display unit 162 included in the determination unit 16.

  FIG. 4 illustrates a case where the right end of a 24V system load group in which a plurality of 24V system loads 12 are connected in parallel and the right end of a 12V system load group in which a plurality of 12V systems loads 14 are connected in parallel are erroneously connected. doing. However, it is obvious that the same situation occurs when an arbitrary location of the conducting wire to which the 24V system load group is connected and an arbitrary location of the conducting wire to which the 12V system load group is connected are erroneously connected. Therefore, the erroneous connection detection circuit 100 can detect that an erroneous connection has occurred regardless of the location of the erroneous connection. Further, the erroneous connection detection circuit 100 can detect an erroneous connection regardless of the number of 24V system loads 12 and the number of 12V system loads 14.

(Modification 1)
In the first embodiment described above, only a voltage lower than 12V is applied to the 12V system load 14 due to the voltage drop caused by the second resistor R2. The voltage drop can be ignored if the current consumption of the multiple connected 12V system loads 14 is small, but the voltage drop can be ignored if there is one 12V system load 14 having a large current consumption. There is a possibility of disappearing. In this case, the voltage drop value Vr2 at the second resistor R2 may be calculated based on the current consumption of the entire 12V system load group, and the output voltage of the 12V power supply 13 may be set to 12V + Vr2. In this way, 12V can be supplied to the 12V system load 14 even if there is a voltage drop due to the second resistor R2.

  However, when the value of 12V + Vr2 is equal to or higher than the threshold voltage in the determination unit 16, there is a possibility that the determination unit 16 determines that “there is an incorrect connection” although no erroneous connection has occurred. Therefore, it is desirable that the value of Vr2 is about 80% of the difference between the threshold voltage and the second voltage at the maximum. For example, when the threshold voltage is 13V, the value of Vr2 is desirably about 0.8V at the maximum.

(Embodiment 2)
In the first embodiment, the 12V power supply 13 is protected by the second resistor R2. However, the 12V power supply 13 can be protected also by using a diode instead of the second resistor R2. Therefore, a second embodiment of the present invention using a diode instead of the second resistor R2 will be described.

  As shown in FIG. 7, the erroneous connection detection circuit 101 according to the second embodiment of the present invention includes a first resistor R1, a 12V power supply 13 and a 12V connected in series between a 24V power supply 11 and a 24V system load 12. A diode D1 connected in series with the system load 14 in the forward direction, and a protection unit 15 and a determination unit 16 connected in parallel with the 12V system load 14 are provided. The diode D1 is a backflow prevention means for preventing a reverse current from flowing into the 12V power supply 13.

  As can be seen from a comparison between FIG. 1 and FIG. 7, a circuit in which the second resistor R2 of the erroneous connection detection circuit 100 according to the first embodiment is replaced with a diode D1 is the erroneous connection detection circuit 101 according to the second embodiment. . Except for this point, the erroneous connection detection circuit 101 according to the second embodiment is the same as the erroneous connection detection circuit 100 according to the first embodiment.

  In the erroneous connection detection circuit 101, when no erroneous connection occurs, the voltage drop due to the diode D1 becomes a constant value determined by the characteristics of the diode D1. For example, if the diode D1 is a silicon diode, the value of this voltage drop is about 0.6V to 0.7V. In addition, when a connection error occurs, the voltage applied to the diode D1 becomes a reverse bias, so that no current flows through the diode D1, and no reverse current flows through the 12V power supply 13.

  As in the first embodiment, FIG. 8 shows an equivalent circuit at the time of erroneous connection by the conducting wire 17. Since the diode D1 is present, the reverse current I3 does not flow through the 12V power supply 13. And the electric current which flows into the protection means 15 becomes (24V-14V) / R1. For example, when the resistance value of the first resistor R1 is set to 100Ω, the current flowing through the protection unit 15 is (24V−14V) /100Ω=0.1A. When the withstand current value of the protection means 15 is less than 0.1 A, it is necessary to increase the resistance value of the first resistor R1 so that the value of 10V / R1 is equal to or less than the withstand current value of the protection means 15. In this case, unlike the first embodiment, it is not necessary to consider the resistance value of the second resistor R2, so that the circuit design becomes easier.

  Further, the value of the forward voltage drop caused by the diode D1 is a constant value determined by the type of the diode. Therefore, assuming that this constant value is VF, by setting the output voltage of the 12V power supply 13 to 12V + VF, 12V can be supplied to the 12V system load 14 even if there is a voltage drop due to the diode D1. That is, the voltage drop due to the diode D1 can be compensated by increasing the output voltage of the 12V power supply 13 by the voltage drop due to the diode D1.

  However, when the value of 12V + VF is equal to or higher than the threshold voltage in the determination unit 16, there is a possibility that the determination unit 16 determines that “there is an incorrect connection” although no erroneous connection has occurred. Therefore, it is desirable that the value of VF is about 80% of the difference between the threshold voltage and the second voltage at the maximum. For example, when the threshold voltage is 13V, the value of VF is desirably about 0.8V at the maximum. However, when the diode D1 is a silicon diode, the value of VF falls within the range of about 0.6V to 0.7V, so this problem does not occur.

(Modification 2)
In the embodiment described above, the second resistor R2 or the diode D1 is provided in order to prevent an excessive reverse current from flowing into the 12V power supply 13. However, in the case where the 12V power supply 13 includes a protection circuit for preventing a reverse current therein, as shown in FIG. 9, the erroneous connection detection circuit 102 does not have a problem even if it does not include the second resistor R2 and the diode D1. Operate. This can be considered as a form in which the diode D1 of the second embodiment is incorporated in the 12V power supply 13.

(Modification 3)
In the embodiment described above, only a voltage lower than 24V is applied to the 24V load 12 due to the voltage drop caused by the first resistor R1. The voltage drop can be ignored when the current consumption of a plurality of 24V system loads 12 connected is small, but the voltage drop can be ignored when there is at least one 24V system load 12 with large current consumption. There is a possibility of disappearing. In this case, the voltage drop value Vr1 at the first resistor R1 may be calculated based on the current consumption of the entire 24V system load group, and the output voltage of the 24V power supply 11 may be set to 24V + Vr1. In this way, even if there is a voltage drop due to the first resistor R1, 24V can be supplied to the 24V system load 12.

  As described above, in both the first embodiment and the second embodiment, the erroneous connection detection circuits 100, 101, 102 can be configured adjacent to the power supply, and the number of loads and the location of the erroneous connection can be determined. It is possible to detect a misconnection without depending on it.

  Various embodiments and modifications can be made to the present invention without departing from the broad spirit and scope of the present invention. The above-described embodiments are for explaining the present invention and do not limit the scope of the present invention. In other words, the scope of the present invention is shown not by the embodiments but by the claims. Various modifications within the scope of the claims and within the scope of the equivalent invention are considered to be within the scope of the present invention.

11 24V power supply, 12 24V system load, 13 12V power supply, 14 12V system load, 15 protection means, 16 determination means, 17 conductor, 100, 101, 102 Misconnection detection circuit, 161 comparison section, 162 display section, D1 diode, I2, I3 current, L1, L2, L3, L5, L6 Solid line, L4 dotted line, R1 first resistance, R2 second resistance, VC measurement point

Claims (6)

A first resistor connected in series between a first voltage system load group driven by a first voltage and a first power supply for supplying power to the first voltage system load group;
In parallel with the second voltage system load group between a second voltage system load group driven by a second voltage lower than the first voltage and a second power source for supplying power to the second voltage system load group. Protection means connected to protect the second voltage system load group by passing a current when a third voltage higher than the second voltage is applied;
Determination means for determining whether or not the third voltage is applied to the protection means;
An erroneous connection detection circuit comprising: The determination means includes display means for displaying whether or not the third voltage is applied to the protection means.
The erroneous connection detection circuit according to claim 1. The determination unit includes a comparison unit that compares a threshold voltage higher than the second voltage and lower than the third voltage with a voltage applied to the protection unit,
If the comparison means finds that the voltage applied to the protection means is greater than or equal to the threshold voltage, it is determined that the third voltage is applied to the protection means;
The erroneous connection detection circuit according to claim 1 or 2. A second resistor connected in series between the second voltage system load group and the second power source;
The erroneous connection detection circuit according to any one of claims 1 to 3. A backflow prevention means connected in series between the second voltage system load group and the second power supply;
The erroneous connection detection circuit according to any one of claims 1 to 3. The second power supply supplies a voltage higher than the second voltage by the amount of voltage drop caused by the backflow prevention means.
The erroneous connection detection circuit according to claim 5.

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