JP2015050694A - Relay control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control an operating state of each relay to a desired state even when a specific output port, in which a control signal for controlling the relay appears, becomes a high-impedance state.SOLUTION: In a relay control device controlling on and off of a plurality of relays 1, 2, 11, and 12 connecting between a high-voltage-system circuit and a low-voltage-system circuit, pull-down circuits 31 to 34 are connected so that input potentials of buffer circuits 6a, 6b, 16a, and 16b approach a constant potential when output ports P1 to P4 of a CPU 20 become high impedance. Even when a microcomputer does not operate, on and off states of each relay can be surely controlled, thereby preventing flow of a high-voltage current from a high-voltage system to a low-voltage system after the plurality of relays simultaneously turn on. The combination of a pull-down circuit 41 and a pull-up circuit 42 surely performs discharging of charges of a flying capacitor 9 at the time of stop of the CPU 20.

Description

  The present invention relates to a relay control device for appropriately controlling a plurality of relays in an electric circuit including a high voltage system and a low voltage system.

  A conventional technique related to the present invention is disclosed in Patent Document 1. Further, by using the apparatus having the configuration shown in FIG. 3 of Patent Document 1, it is possible to measure a ground fault resistance in a power supply circuit on a vehicle that handles a high voltage, for example.

  In such an apparatus for measuring the ground fault resistance, it is necessary to use a capacitor called a flying capacitor and charge the flying capacitor from the output of the high-voltage circuit, and then discharge the flying capacitor. A plurality of relays are used to charge and discharge the flying capacitor. The plurality of relays include a relay for performing a charging operation and a relay for performing a discharging operation. In the charging operation, the former relay is turned on and the latter relay is turned off. Further, during the discharging operation, the former relay is turned off and the latter relay is turned on.

  In the above configuration, if the former relay and the latter relay are simultaneously turned on, a high-voltage current flows from the high-voltage circuit to the low-voltage circuit via a plurality of relays that are turned on. However, there is a high possibility that the low-pressure circuit is destroyed. Therefore, control must be performed so that both the relay for performing the charging operation and the relay for performing the discharging operation are not turned on at the same time.

  Therefore, in Patent Document 1, a light emitting diode (LED) that controls a relay for performing a charging operation and a light emitting diode that controls a relay for performing a discharging operation are connected in parallel in opposite directions. doing. As a result, the relay for performing the charging operation and the relay for performing the discharging operation can be prevented from being simultaneously turned on, and the high-voltage current is prevented from flowing directly from the high-voltage circuit to the low-voltage circuit. it can.

JP 2010-28711 A

  By the way, in the apparatus which measures ground fault resistance, a voltage is measured with charging / discharging of a flying capacitor, and predetermined calculation is performed based on a measurement result, and ground fault resistance is calculated | required. For example, by using a microcomputer, it is possible to individually control on / off of a plurality of relays, measure voltages, and calculate a ground fault resistance from a measurement result.

  On the other hand, an output port that can be used by a general microcomputer to output various control signals is often configured as an output of a three-state circuit so that it can be connected to various bus lines. This configuration includes a high-potential side switching element that connects one output port to a high-potential side line, and a low-potential side switching element that connects the same output port to a low-potential side line.

  Therefore, the microcomputer can output a high-potential signal by controlling the high-potential side and low-potential side switching elements of the corresponding output port to be on and off, respectively. Further, a low potential signal can be output by controlling the switching elements on the high potential side and the low potential side to be off and on, respectively. Further, by simultaneously turning off both the high-potential side and low-potential side switching elements, the corresponding output port can be brought into an open state, i.e., a state of high impedance, which is not connected to anywhere. . Therefore, there are three types of states (three-state or tri-state) as one output port state: a high-potential state, a low-potential state, and a high-impedance state.

  In a device for measuring ground fault resistance, when a plurality of relays are controlled by a microcomputer, each relay is turned on or off by outputting a high potential or low potential control signal to an output port of the microcomputer. Can be switched. However, when the output port of the microcomputer is in a high impedance state, the state of the control signal is not determined, so the on / off operation of the relay is not determined. Therefore, when controlling on / off of a load such as a relay, the microcomputer generally controls the output port so as not to use the high impedance state.

  However, for example, when a reset signal is applied to the microcomputer by turning on the power, when the power is turned off, or when a reset signal is forcibly generated due to some abnormality, the state of the microcomputer itself is initialized. Therefore, all the output ports are temporarily in a high impedance state.

  For example, in the apparatus shown in FIG. 3 of Patent Document 1, when the output port of the microcomputer is in a high impedance state, the operating states of all the relays connected to the periphery of the flying capacitor are not determined. The connection status of is not determined. Therefore, for example, in the initial state when starting measurement of ground fault resistance, the operation of discharging the charge of the flying capacitor to reduce the measurement error in consideration of the possibility that the charge has already accumulated in the flying capacitor. Must be implemented as initialization. Therefore, extra time is required for preparation (initialization) from when the power of the apparatus is turned on to when measurement is actually started.

  Even in the case of a logic circuit that does not use a microcomputer, for example, when the relay is controlled using a logic circuit including a three-state output buffer, the same occurrence may occur.

  The present invention has been made in view of the above-described circumstances, and its purpose is to provide each relay even when a specific output port in which a control signal for controlling the relay appears is in a high impedance state. It is an object of the present invention to provide a relay control device that can control the operation state of the device to a desired state.

In order to achieve the above-described object, a relay control device according to the present invention is characterized by the following (1) to (4).
(1) High-voltage and low-voltage electric circuits;
A first relay for opening and closing an electrical connection between the high voltage system and a predetermined intermediate point;
A second relay for opening and closing an electrical connection between the low pressure system and the intermediate point;
A control signal generator including a plurality of output ports that can change to any of three states of high level, low level, and high impedance;
A driving unit that drives the first relay and the second relay based on the high / low potentials of the first control signal and the second control signal appearing in the plurality of output ports;
A first initial potential control unit that brings an initial potential of the first control signal close to a predetermined high potential or a predetermined low potential;
A second initial potential control unit for bringing the initial potential of the second control signal close to a predetermined high potential or a predetermined low potential;
Having prepared.
(2) A relay control device configured as described in (1) above,
The first initial potential control unit and the second initial potential control unit bring the potential in the initial state closer to a high potential or a low potential equivalent to each other;
about.
(3) A relay control device configured as described in (1) above,
One of the first initial potential control unit and the second initial potential control unit brings the potential in the initial state closer to a predetermined high potential,
The other of the first initial potential control unit and the second initial potential control unit brings the potential in the initial state closer to a predetermined low potential.
about.
(4) A relay control device configured as described in (3) above,
The first initial potential control unit and the second initial potential control unit are configured to set the potential in the initial state to a predetermined value so that the first relay is opened and the second relay is closed in the initial state. Close to a high potential or a predetermined low potential,
about.

According to the relay control device having the above configuration (1), when the output port of the control signal generating unit is in a high impedance state, the first initial potential control unit outputs the first control signal to a predetermined high potential or Since the second initial potential control unit brings the second control signal close to a predetermined high potential or low potential close to the low potential, the state of each relay can be fixed to a desired state.
According to the relay control device having the configuration of (2) above, when the output port of the control signal generation unit is in a high impedance state, the first initial potential control unit and the second initial potential control unit function, Both the first relay and the second relay can be initialized to a state where the circuit connection is cut off.
According to the relay control device having the configuration of (3) above, when the output port of the control signal generation unit is in a high impedance state, the first initial potential control unit and the second initial potential control unit function. The first relay and the second relay can be initialized to be turned on.
According to the relay control device having the configuration of (4) above, when the output port of the control signal generation unit is in a high impedance state, the first initial potential control unit and the second initial potential control unit function, Only the second relay can be turned on. Thereby, for example, in the configuration shown in FIG. 3 of Patent Document 1, the charge of the flying capacitor can be discharged.

  According to the relay control device of the present invention, even if a specific output port in which a control signal for controlling the relay appears is in a high impedance state, the operation state of each relay is controlled to a desired state. It is possible.

  The present invention has been briefly described above. Further, the details of the present invention will be further clarified by reading through a mode for carrying out the invention described below (hereinafter referred to as “embodiment”) with reference to the accompanying drawings. .

FIG. 1 is an electric circuit diagram showing a configuration of a ground fault resistance measuring apparatus according to the first embodiment. FIG. 2 is an electric circuit diagram showing a configuration of a ground fault resistance measuring apparatus according to the second embodiment.

  Specific embodiments relating to the relay control device of the present invention will be described below with reference to the drawings.

<First Embodiment>
<Overview>
In the present embodiment, it is assumed that the relay control device of the present invention is mounted on the ground fault resistance measuring device 100A shown in FIG.

  A ground fault resistance measuring device 100A shown in FIG. 1 is mounted on a vehicle such as an electric vehicle or a hybrid car, for example, and electrodes 101 and 102 on the output side of a high-voltage power supply 3 for supplying electric energy for propulsion of the vehicle; Used in a connected state. The ground fault resistance measuring apparatus 100A includes a ground fault resistance RL + between the positive electrode 101 and the ground (earth such as a vehicle body) G, and a ground fault resistance RL− between the negative electrode 102 and the ground G. Can be measured.

  The ground fault resistance measuring apparatus 100A shown in FIG. 1 includes five relays (1, 2, 11, 12, 13) in order to control charging and discharging of the flying capacitor 9. These relays are controlled by the relay control device of the present invention.

<Description of configuration>
The ground fault resistance measuring apparatus 100A shown in FIG. 1 includes a flying capacitor 9, optical MOS semiconductor relays 1, 2, 11, 12, and 13, buffer circuits 6a, 6b, 16a, and 16b, a low-pass filter (LPF) 14, and a microcomputer. (CPU) 20, a power supply unit 25, pull-down circuits 31, 32, 33, 34, resistors R1, R2, R3, R4, R5, R6, R7, R8, and diodes D1, D2.

  The optical MOS semiconductor relay 1 is a device in which a switching element 1b composed of a MOS transistor (FET) and a light emitting diode (LED) 1a for control are integrated. Actually, a light receiving element (not shown) such as a photodiode is connected to the gate electrode of the MOS transistor, and the light receiving element and the light emitting diode 1a form a photocoupler. That is, a signal indicating whether or not the light emitting diode 1a emits light is applied to the gate electrode of the switching element 1b, and the on / off state of the switching element 1b is changed by this signal. Therefore, although the light emitting diode 1a and the switching element 1b are electrically separated (insulated), the on / off state of the switching element 1b can be controlled using an optical signal. By using the optical MOS semiconductor relay 1, the switching element 1b that handles high voltage and the light emitting diode 1a connected to the low voltage circuit can be electrically separated.

  The other optical MOS semiconductor relays 2, 11, 12, and 13 have the same configuration as the above-described optical MOS semiconductor relay 1.

  As shown in FIG. 1, the switching element 1b is connected to a position where the electrical connection between the positive electrode 101 of the high-voltage power supply 3 and the positive terminal of the flying capacitor 9 can be turned on / off (closed / opened). Yes. The switching element 2b is connected to a position where the electrical connection between the positive terminal of the flying capacitor 9 and the resistor R4 connected to the ground G can be turned on and off.

  The switching element 11b is connected to a position where the electrical connection between the negative electrode 102 of the high-voltage power supply 3 and the negative terminal of the flying capacitor 9 can be turned on / off. The switching element 12b is connected to a position where the electrical connection between the negative terminal of the flying capacitor 9 and the resistor R5 connected to the ground G can be turned on and off. The switching element 13b is connected to a position where a circuit path for discharging the electric charge of the flying capacitor 9 to the ground G through the resistor R6 having a relatively small resistance value can be turned on and off.

  In the circuit shown in FIG. 1, if the two switching elements 1b and 2b are turned on at the same time, a high voltage current flows directly from the high voltage side to the low voltage side circuit, and the low voltage side circuit may be destroyed. In order to prevent this, the light-emitting diode 1a of the optical MOS semiconductor relay 1 and the light-emitting diode 2a of the optical MOS semiconductor relay 2 are connected in parallel with their polar directions reversed. That is, as shown in FIG. 1, the anode electrode of the light emitting diode 1a and the cathode electrode of the light emitting diode 2a are connected, and the cathode electrode of the light emitting diode 1a and the anode electrode of the light emitting diode 2a are connected.

  Similarly, the light emitting diode 11a of the optical MOS semiconductor relay 11 and the light emitting diode 12a of the optical MOS semiconductor relay 12 have opposite polarities so that the two switching elements 11b and 12b are not turned on simultaneously. Connected in parallel. That is, as shown in FIG. 1, the anode electrode of the light emitting diode 11a and the cathode electrode of the light emitting diode 12a are connected, and the cathode electrode of the light emitting diode 11a and the anode electrode of the light emitting diode 12a are connected.

  The light emitting diode 1a of the optical MOS semiconductor relay 1 and the light emitting diode 2a of the optical MOS semiconductor relay 2 are connected to the outputs of the buffer circuits 6a and 6b composed of NAND gates. In addition, a resistor R1 is inserted at the output of the buffer circuit 6b to limit the current.

  Therefore, for example, when the output of the buffer circuit 6a becomes a high level H and the output of the buffer circuit 6b becomes a low level L, a current flows through the light emitting diode 2a and no current flows through the light emitting diode 1a. 2 switching element 2b is turned on, and switching element 1b of optical MOS semiconductor relay 1 is turned off. On the contrary, when the output of the buffer circuit 6a becomes low level L and the output of the buffer circuit 6b becomes high level H, current flows through the light emitting diode 1a and no current flows through the light emitting diode 2a. The switching element 2b is turned off. When the output of the buffer circuit 6a and the output of the buffer circuit 6b are at the same level, no current flows through both the light emitting diodes 1a and 2a, so that the switching elements 1b and 2b are turned off.

  The light emitting diode 11a of the optical MOS semiconductor relay 11 and the light emitting diode 12a of the optical MOS semiconductor relay 12 are connected to the outputs of buffer circuits 16a and 16b formed of NAND gates. A resistor R8 is inserted at the output of the buffer circuit 16b to limit the current.

  Therefore, for example, when the output of the buffer circuit 16a becomes a high level H and the output of the buffer circuit 16b becomes a low level L, a current flows through the light emitting diode 12a and no current flows through the light emitting diode 11a. The 12 switching elements 12b are turned on, and the switching element 11b of the optical MOS semiconductor relay 11 is turned off. On the contrary, when the output of the buffer circuit 16a becomes low level L and the output of the buffer circuit 16b becomes high level H, current flows through the light emitting diode 11a and no current flows through the light emitting diode 12a. The switching element 12b is turned off. When the output of the buffer circuit 16a and the output of the buffer circuit 16b are at the same level, no current flows through both the light emitting diodes 11a and 12a, so that the switching elements 11b and 12b are turned off.

  The inputs of the four buffer circuits 6a, 6b, 16a, and 16b are connected to output ports P1, P2, P3, and P4 of the microcomputer 20, respectively. Therefore, the microcomputer 20 can switch on / off of the optical MOS semiconductor relays 1 and 2 via the buffer circuits 6a and 6b by controlling H / L of the signals output to the output ports P1 and P2. Further, the microcomputer 20 can switch on / off of the optical MOS semiconductor relays 11 and 12 via the buffer circuits 16a and 16b by controlling H / L of signals output to the output ports P3 and P4.

  A light emitting diode 13a is connected to the output port P5 of the microcomputer 20 via a resistor R7. Therefore, the microcomputer 20 can control the on / off of the optical MOS semiconductor relay 13 by the control signal output to the output port P5.

  Incidentally, each of the output ports P <b> 1 to P <b> 4 of the microcomputer 20 is configured as a three-state output circuit inside the microcomputer 20. That is, there are three types of signal states appearing at the output ports P1 to P4: a high level H state, a low level L state, and a high impedance state. In the high impedance state, the signal potential is indeterminate, and the potential can change depending on the situation.

  When the microcomputer 20 executes its own program, for example, as an initialization process, the operation mode can be determined so that each of the output ports P1 to P4 can be used only as an output port. By selecting such a mode, it is possible to prevent a high impedance state from occurring.

  However, there is a possibility that the output ports P1 to P4 may be in a high impedance state when the microcomputer 20 is in an operation state different from the normal state, such as when the program has not yet been executed. Specifically, immediately after the power of the apparatus is turned on and power is supplied from the power supply unit 25 to the power supply line Vcc (for example, +5 V), the reset signal RST is input to the microcomputer 20 to set the operation mode to the initial state. When returning, the output ports P1 to P4 are in a high impedance state. Similarly, the operation mode returns to the initial state when the power of the apparatus is turned off, or when a reset signal is forcibly generated due to an abnormality such as runaway in the operation of the microcomputer 20. The output ports P1 to P4 are in a high impedance state.

  In the circuit shown in FIG. 1, one resistor constituting the pull-down circuit 33 is connected between the input terminal of the buffer circuit 6a and the ground G. The pull-down circuit 33 functions to determine the signal potential when the output port P1 of the microcomputer 20 is in a high impedance state. Further, a resistor having a relatively large resistance value (for example, 50 kΩ) is used for the pull-down circuit 33 so as not to greatly affect the potential of the signal output from the microcomputer 20 in a state other than high impedance.

  That is, when the output port P1 of the microcomputer 20 is in a high impedance state, the input terminal of the buffer circuit 6a is grounded via the resistor of the pull-down circuit 33, so the signal potential at the input of the buffer circuit 6a is low. It becomes level L (potential close to 0V).

  Similarly, one resistor constituting the pull-down circuit 34 is connected between the input terminal of the buffer circuit 6b and the ground G. This pull-down circuit 34 functions to bring the signal potential at the input end of the buffer circuit 6b close to 0 V when the output port P2 of the microcomputer 20 is in a high impedance state.

  Further, one resistor constituting the pull-down circuit 31 is connected between the input terminal of the buffer circuit 16a and the ground G. The pull-down circuit 31 functions to bring the signal potential at the input end of the buffer circuit 16a close to 0 V when the output port P3 of the microcomputer 20 is in a high impedance state.

  Further, one resistor constituting the pull-down circuit 32 is connected between the input terminal of the buffer circuit 16 b and the ground G. This pull-down circuit 32 functions to bring the signal potential at the input end of the buffer circuit 16b close to 0 V when the output port P4 of the microcomputer 20 is in a high impedance state.

  Therefore, when the four output ports P1 to P4 of the microcomputer 20 are in a high impedance state, the input of the buffer circuits 6a, 6b, 16a, and 16b is caused by the action of the pull-down circuits 31, 32, 33, and 34, respectively. Low level L. In that case, since the outputs of the buffer circuits 6a, 6b, 16a, and 16b are at a high level H, no current flows through any of the light emitting diodes 1a, 2a, 11a, and 12a, and the switching elements 1b, 2b, 11b and 12b are all turned off.

  On the other hand, the analog signal input port P 6 of the microcomputer 20 is connected to the output terminal of the low-pass filter 14. The input end of the low-pass filter 14 is connected to the output end of the switching element 2b. Therefore, when the switching element 2b is turned on, an analog signal is input via the diode D2, the resistor R3, the switching element 2b, and the low-pass filter 14 to the signal corresponding to the potential at the positive side terminal of the flying capacitor 9. Input to port P6. The microcomputer 20 can sample the signal of the analog signal input port P6, perform A / D conversion, and measure the potential.

<Description of operation>
The basic measurement operation of the ground fault resistance measuring apparatus 100A is the same as that of the conventional technique such as Patent Document 1. Therefore, only the minimum necessary basic operations will be described below.

  The microcomputer 20 switches the optical MOS semiconductor relays 1, 2, 11, and 12 to measure the three types of voltages while controlling the charging and discharging of the flying capacitor 9, and calculates the ground fault by calculation based on these measurement results. Find resistance. In addition, if a charge has already been accumulated before the charging of the flying capacitor 9 is started, a measurement error occurs. Therefore, the discharging operation is usually performed before the charging is started.

  Measurement of the power supply voltage V0 of the high-voltage power supply 3 is performed as one of the three types of voltages. In this case, under the control of the microcomputer 20, the switching elements 1b and 11a are first turned on and the switching elements 2b, 12b and 13b are turned off. Thus, the electrode 101 is connected to the positive terminal of the flying capacitor 9 via the switching element 1b, the diode D1, and the resistor R2, and the electrode 102 is connected to the negative terminal of the flying capacitor 9 via the switching element 11b. Connected. Therefore, the charge corresponding to the voltage of the high voltage power supply 3 is charged in the flying capacitor 9.

  Next, under the control of the microcomputer 20, the switching elements 1b, 11b, and 13b are turned off and the switching elements 2b and 12b are turned on. Thereby, the connection between the electrodes 101 and 102 side and the flying capacitor 9 is cut off. Further, the positive terminal of the flying capacitor 9 is connected to the ground G through the diode D2, the resistor R3, the switching element 2b, and the resistor R4, and the negative terminal of the flying capacitor 9 is connected to the switching element 12b and the resistor. It is connected to the ground G through the device R5. Further, the voltage between the terminals of the resistor R4 is applied to the analog signal input port P6 of the microcomputer 20 via the low pass filter 14. Therefore, the microcomputer 20 can measure the power supply voltage V 0 as the charging voltage of the flying capacitor 9.

  In addition, as one of the three types of voltages, the voltage Vn that is affected by the resistance value of the ground fault resistance RL− is measured. In this case, under the control of the microcomputer 20, the switching elements 1b and 12b are turned on and the switching elements 2b, 11b and 13b are turned off. Thereby, the electrode 101 is connected to the plus side terminal of the flying capacitor 9 via the switching element 1b, the diode D1, and the resistor R2, and the electrode 102 is connected to the ground fault resistance RL−, the ground G, the resistor R5, and It is connected to the negative terminal of the flying capacitor 9 via the switching element 12b. Therefore, the charge affected by the resistance value of the ground fault resistance RL− is charged in the flying capacitor 9.

  After the charging of the flying capacitor 9 is completed, the switching elements 1b, 11b, and 13b are turned off again, and the switching elements 2b and 12b are turned on. Thereby, the microcomputer 20 measures the charging voltage of the flying capacitor 9, that is, the voltage Vn affected by the resistance value of the ground fault resistance RL−, using the same path as that for measuring the power supply voltage V0. Can do.

  In addition, as one of the three types of voltages, the voltage Vp affected by the resistance value of the ground fault resistance RL + is measured. In this case, under the control of the microcomputer 20, the switching elements 2b and 11b are turned on, and the switching elements 1b, 12b and 13b are turned off. As a result, the electrode 101 is connected to the positive terminal of the flying capacitor 9 via the ground fault resistance RL +, the ground G, the resistor R4, the switching element 2b, the diode D1, and the resistor R2, and the electrode 102 is switched. It is connected to the negative terminal of the flying capacitor 9 via the element 11b. Therefore, the charge affected by the resistance value of the ground fault resistance RL + is charged in the flying capacitor 9.

  After the charging of the flying capacitor 9 is completed, the switching elements 1b, 11b, and 13b are turned off again, and the switching elements 2b and 12b are turned on. Thereby, the microcomputer 20 can measure the voltage Vp affected by the charging voltage of the flying capacitor 9, that is, the resistance value of the ground fault resistance RL +, using the same path as that for measuring the power supply voltage V0. it can.

<Description of functions of pull-down circuits 31-34>
In the circuit shown in FIG. 1, pull-down circuits 33, 34, 31, and 32 are connected to the input terminals of the buffer circuits 6a, 6b, 16a, and 16b. Therefore, when the output ports P1 to P4 of the microcomputer 20 are in a high impedance state, the input terminals of the buffer circuits 6a, 6b, 16a, and 16b can be maintained at the low level L. For this reason, when each of the output ports P1 to P4 is in a high impedance state, the switching elements 1b, 2b, 11b, and 12b are all turned off, and the inflow of a high voltage current from the high voltage circuit to the low voltage circuit can be reliably prevented.

  When the pull-down circuits 33, 34, 31, and 32 are not present, the potentials at the input terminals of the buffer circuits 6a, 6b, 16a, and 16b are unstable when the output ports P1 to P4 are in a high impedance state. become. For example, when some electrical noise is applied from the outside, there is a high possibility that the potentials of the input terminals of the buffer circuits 6a, 6b, 16a, and 16b fluctuate irregularly under the influence of the noise.

  In the circuit shown in FIG. 1, two light emitting diodes 1a and 2a of two optical MOS semiconductor relays 1 and 2 that are not desired to be turned on at the same time are connected in parallel with opposite polarities. For this reason, even if the input level and the output level of the buffer circuits 6a and 6b are repeatedly fluctuated due to the influence of noise, a state where the two optical MOS semiconductor relays 1 and 2 are turned on at the same time probably does not occur. Conceivable.

  However, when, for example, a mechanical relay is adopted instead of the optical MOS semiconductor relays 1 and 2, the two relays are turned on simultaneously even if they are temporary due to the influence of the operation delay of the mechanical contacts, for example. There is a possibility. The same applies to the other two optical MOS semiconductor relays 11 and 12.

  By connecting the pull-down circuits 33, 34, 31, and 32 to the respective input terminals of the buffer circuits 6a, 6b, 16a, and 16b, the buffer circuits 6a, 6b, 16a, and 16b can be used even in a high impedance state. Therefore, even if a time delay occurs in the operation of the relay, unintended simultaneous operation of the relay can be avoided. Therefore, the inflow of high voltage current from the high voltage circuit to the low voltage circuit can be reliably prevented.

Second Embodiment
The configuration of the ground fault resistance measuring apparatus 100B according to the present embodiment is shown in FIG. Most of the configuration and operation of the ground fault resistance measuring apparatus 100B shown in FIG. 2 are the same as those of the ground fault resistance measuring apparatus 100A shown in FIG.

  That is, in the ground fault resistance measuring apparatus 100B shown in FIG. 2, pull-down circuits 41 and 43 and pull-up circuits 42 and 44 are connected instead of the pull-down circuits 31 to 34 in FIG. Other configurations are the same as those of the ground fault resistance measuring apparatus 100A.

  As shown in FIG. 2, a pull-down circuit 43 is connected to the input terminal of the buffer circuit 6a, and a pull-up circuit 44 is connected to the input terminal of the buffer circuit 6b. A pull-down circuit 41 is connected to the input terminal of the buffer circuit 16a, and a pull-up circuit 42 is connected to the input terminal of the buffer circuit 16b.

  The pull-down circuit 43 is composed of one resistor having one end connected to the input of the buffer circuit 6a and the other end connected to the ground G. The pull-up circuit 44 is composed of one resistor having one end connected to the power supply line Vcc and the other end connected to the input of the buffer circuit 6b. Therefore, when the output ports P1 to P4 of the microcomputer 20 are in a high impedance state, the pull-down circuit 43 brings the input terminal of the buffer circuit 6a close to a low level L potential (for example, 0 V), and the pull-up circuit 44 inputs the buffer circuit 6b. The end is brought close to a high level H potential (for example, 5 V). As a result, the output of the buffer circuit 6a becomes high level H and the output of the buffer circuit 6b becomes low level L, so that the switching element 2b is turned on and the switching element 1b is turned off.

  Similarly, the pull-down circuit 41 is composed of one resistor having one end connected to the input of the buffer circuit 16a and the other end connected to the ground G. The pull-up circuit 42 is composed of one resistor having one end connected to the power supply line Vcc and the other end connected to the input of the buffer circuit 16b. Therefore, when the output ports P1 to P4 of the microcomputer 20 are high impedance, the pull-down circuit 41 brings the input terminal of the buffer circuit 16a close to a low level L potential (for example, 0V), and the pull-up circuit 42 is input to the buffer circuit 16b. The end is brought close to a high level H potential (for example, 5 V). As a result, the output of the buffer circuit 16a becomes high level H and the output of the buffer circuit 16b becomes low level L, so that the switching element 12b is turned on and the switching element 11b is turned off.

  That is, when the output ports P1 to P4 of the microcomputer 20 are high impedance, the switching elements 1b and 11b are turned off, so that the flying capacitor 9 is reliably disconnected from the high-voltage power supply 3. Since the switching elements 2b and 12b are turned on, the positive terminal of the flying capacitor 9 is connected to the ground G via the diode D2, the resistor R3, the switching element 2b, and the resistor R4. 9 is connected to the ground G via the switching element 12b and the resistor R5. As a result, a path for discharging is formed, so that the charge accumulated in the flying capacitor 9 is reliably discharged to the ground G.

  For example, when the power supply of the ground fault resistance measuring device 100B is cut off, the microcomputer 20 is reset, so that the output ports P1 to P4 become high impedance. At this time, since the discharge path of the flying capacitor 9 is formed by the action of the pull-down circuits 41 and 43 and the pull-up circuits 42 and 44, the electric charges can be discharged reliably.

  If the high-voltage charge is accumulated in the flying capacitor 9 when the power supply of the ground fault resistance measuring device 100B is cut off, there is a risk that a user's hand or the like touches the circuit and receives an electric shock. However, in the ground fault resistance measuring apparatus 100B of FIG. 2, the pull-down circuits 41 and 43 and the pull-up circuits 42 and 44 are controlled so as to discharge the charge of the flying capacitor 9 when the power is cut off, so that an electric shock can be prevented.

  Further, when the ground fault resistance measuring device 100B measures the ground fault resistance, if a charge is accumulated in the flying capacitor 9, a measurement error occurs. Therefore, in the case of a general device, before starting the measurement. Therefore, it is necessary to discharge the flying capacitor 9. However, in the ground fault resistance measuring apparatus 100B, the pull-down circuits 41 and 43 and the pull-up circuits 42 and 44 control so that the electric charge of the flying capacitor 9 is discharged when the power is cut off. The charge of the flying capacitor 9 has already been discharged when. Therefore, immediately after the power is turned on, no measurement error occurs even if measurement is started immediately after omitting the process of discharging the charge. Therefore, the waiting time from when the apparatus is turned on to when the measurement is started can be greatly shortened.

<Possibility of deformation>
In the ground fault resistance measuring apparatus 100A shown in FIG. 1, pull-down circuits 31 to 34 are connected to the inputs of the buffer circuits 6a, 6b, 16a and 16b, respectively. It may be replaced with a pull-up circuit. That is, if the input of the buffer circuit 6a and the input of the buffer circuit 6b are at the same potential, the switching elements 1b and 2b can be reliably turned off, and the input of the buffer circuit 16a and the input of the buffer circuit 16b are the same. If it is a potential, the switching elements 11b and 12b can be reliably turned off.

  Further, in the ground fault resistance measuring apparatus 100A shown in FIG. 1, the optical MOS semiconductor relays 1, 2, 11, 12, and 13 are employed as relays. However, these are replaced with general mechanical relays. Is also possible.

Here, the features of the embodiment of the relay control device according to the present invention described above are briefly summarized and listed in the following [1] to [4], respectively.
[1] High-voltage and low-voltage electric circuits;
A first relay (optical MOS semiconductor relay 1) that opens and closes an electrical connection between the high-voltage system and a predetermined intermediate point;
A second relay (optical MOS semiconductor relay 2) that opens and closes an electrical connection between the low-voltage system and the intermediate point;
A control signal generation unit (a microcomputer 20 including output ports P1 to P4) including a plurality of output ports that can change to any of three states of high level, low level, and high impedance
Drive units (buffer circuits 6a, 6b, 6a, 6b, 6b) that drive the first relay and the second relay based on the high / low potentials of the first control signal and the second control signal appearing in the plurality of output ports. 16a, 16b)
A first initial potential control unit (pull-down circuits 31, 33) for bringing the initial state potential of the first control signal close to a predetermined high potential or a predetermined low potential;
A second initial potential control unit (pull-down circuits 32 and 34) for bringing the initial potential of the second control signal close to a predetermined high potential or a predetermined low potential;
A relay control device comprising:
[2] The first initial potential control unit and the second initial potential control unit bring the potential in the initial state closer to a high potential or a low potential equivalent to each other.
The relay control device according to [1], wherein
[3] One of the first initial potential control unit (pull-down circuits 41 and 43) and the second initial potential control unit (pull-up circuits 42 and 44) sets the potential in the initial state to a predetermined high potential. Close
The other of the first initial potential control unit and the second initial potential control unit brings the potential in the initial state closer to a predetermined low potential.
The relay control device according to [1], wherein
[4] The first initial potential control unit and the second initial potential control unit are configured to detect the potential in the initial state so that the first relay is opened and the second relay is closed in the initial state. To a predetermined high potential or a predetermined low potential,
[3] The relay control device according to [3].

1, 2, 11, 12, 13 Optical MOS semiconductor relays 1a, 2a, 11a, 12a, 13a Light emitting diodes 1b, 2b, 11b, 12b, 13b Switching element 3 High voltage power supplies 6a, 6b, 16a, 16b Buffer circuit 9 Flying capacitor 14 Low-pass filter 20 Microcomputer 25 Power supply unit 31, 32, 33, 34 Pull-down circuit 41, 43 Pull-down circuit 42, 44 Pull-up circuit 100A, 100B Ground fault resistance measuring device 101, 102 Electrode G Ground Vcc Power line D1, D2 Diode R1, R2, R3, R4, R5, R6, R7, R8 Resistors RL +, RL- Ground fault resistance

Claims (4)

High-voltage and low-voltage electric circuits;
A first relay for opening and closing an electrical connection between the high voltage system and a predetermined intermediate point;
A second relay for opening and closing an electrical connection between the low pressure system and the intermediate point;
A control signal generator including a plurality of output ports that can change to any of three states of high level, low level, and high impedance;
A driving unit that drives the first relay and the second relay based on the high / low potentials of the first control signal and the second control signal appearing in the plurality of output ports;
A first initial potential control unit that brings an initial potential of the first control signal close to a predetermined high potential or a predetermined low potential;
A second initial potential control unit for bringing the initial potential of the second control signal close to a predetermined high potential or a predetermined low potential;
A relay control device comprising: The first initial potential control unit and the second initial potential control unit bring the potential in the initial state closer to a high potential or a low potential equivalent to each other;
The relay control device according to claim 1. One of the first initial potential control unit and the second initial potential control unit brings the potential in the initial state closer to a predetermined high potential,
The other of the first initial potential control unit and the second initial potential control unit brings the potential in the initial state closer to a predetermined low potential.
The relay control device according to claim 1. The first initial potential control unit and the second initial potential control unit are configured to set the potential in the initial state to a predetermined value so that the first relay is opened and the second relay is closed in the initial state. Close to a high potential or a predetermined low potential,
The relay control device according to claim 3.

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