JP2015001423A - Insulation status detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique which realizes an insulation status detection device capable of properly operating even during step-up operation.SOLUTION: A ground fault sensor 11 includes: a flying capacitor C1; first and second switches SW1, SW2 selectively connecting both poles of the flying capacitor C1 to a positive pole and a negative pole of a high voltage DC power supply B; third and fourth switches SW3, SW4 selectively connecting both poles of the flying capacitor C1 to a control part (micro-computer) 15 and a ground potential part; a current direction selection circuit 30; and a high voltage selection circuit 20 on the upstream side of the first and second switches SW1, SW2. The high voltage selection circuit 20 has primary and secondary selection diodes arranged in parallel, having both cathode sides connected, and is communicated to the first switch SW1, while an anode of the primary selection diode is connected to a primary side high voltage positive pole. Further, the anode of the secondary selection diode is connected to a secondary side high voltage positive pole of a booster 3.

Description

  The present invention relates to an insulation state detection device that detects a ground fault or an insulation state with respect to a ground potential based on a state of charge of a flying capacitor.

  Electric vehicles and PHVs (plug-in hybrid vehicles) have been put into practical use, and various types of vehicles have been put on the market. In such a vehicle, electric power is used as a power source. In that case, for example, it is necessary to insulate the DC power source whose voltage is increased to 200 V from the vehicle body. And the insulation state detection apparatus which detects the ground fault and insulation state with respect to the grounding potential part of such DC power supply plays an important role. As this type of insulation state detection device, a device using a flying capacitor charged by a DC power source is known. This insulation state detection device detects a ground fault resistance or insulation state on the positive side or negative side by charging a flying capacitor with a positive potential or negative potential of a DC power source and measuring the charging voltage with a microcomputer or the like. .

  By the way, as described above, in a vehicle that uses electric power as propulsion energy, the positive potential of the DC power supply may be boosted and supplied to the load in order to increase the drive efficiency of the load. In such a case, it is necessary to detect a ground fault or an insulation state with respect to the ground potential portion for each of the primary side before boosting and the secondary side after boosting.

  In this case, it is desirable to place a ground fault sensor on the primary side in consideration of the breakdown voltage of components, the voltage detection backup of the high voltage battery, and the like. Depending on the boosted secondary voltage and ground fault resistance value, an abnormal potential wraparound from the secondary side may occur, and various countermeasure techniques have been proposed. For example, there is a technique for performing control to stop the ground fault measurement operation during boosting (for example, see Patent Document 1). In addition, in the configuration of the primary side, a negative potential measurement circuit is provided, and due to the relationship between the secondary side positive potential obtained by boosting the positive potential of the DC power source insulated from the ground potential portion and the ground fault resistance, There is also a technique that enables the charging voltage of the flying capacitor to be measured by the measuring means even when the flying capacitor is charged with the reverse polarity by the secondary side positive potential during charging with the positive potential of the DC power supply (for example, Patent Document 2). reference).

JP 2010-239822 A JP 2011-017586 A

  By the way, in the technique disclosed in Patent Document 1, there is a problem that a period during which the measurement operation is temporarily stopped is generated, and thus the period during which the measurement can be performed is limited. Further, in the technique disclosed in Patent Document 2, there is a tendency that an additional circuit becomes large, and the design burden of an application (software) for dealing with it is large, and another technique is required.

  The object of the present invention is made in view of such a situation, and is to provide a technique for solving the above-described problems.

The present invention provides a flying capacitor charged with a voltage corresponding to a ground fault resistance by a DC power source insulated from a ground potential portion, and the flying capacitor insulated from the DC power source after being charged by the DC power source, A measuring circuit for measuring a charging voltage of the flying capacitor and a measuring circuit connected in series between the ground potential section, and boosting a positive potential of the DC power supply to supply to a load on a primary side of the boosting power supply circuit; An insulation state detection device that is connected and detects an insulation state of the boost power supply circuit based on a measurement result of a charging voltage of the flying capacitor by the measurement unit, the primary side positive electrode and the secondary side positive electrode And a high voltage selection circuit that configures a circuit that guides a direct current to the flying capacitor. The high voltage selection circuit is connected to the primary side A primary selection unit that is connected to the pole and functions to prevent current from flowing to the primary-side positive electrode during at least a boost operation; and a secondary selection unit that is connected to the secondary-side positive electrode .
The primary selection unit and the secondary selection unit flow current from the primary-side positive electrode and the secondary-side positive electrode, and from the high-voltage selection circuit, the primary-side positive electrode and the secondary-side positive electrode. Rectifying means connected so as not to flow current to the positive electrode may be used.
The primary selection unit and the secondary selection unit may be switching means that is controlled to be turned on / off, and the primary selection unit may be controlled to be turned off during a boost operation.

  According to the present invention, it is possible to realize an insulation state detection device that can operate properly even during a boost operation.

FIG. 3 is a diagram of a boost power supply circuit including a ground fault sensor according to an embodiment of the invention. 1 is a diagram of a high voltage selection circuit according to an embodiment of the invention. It is a figure of the step-up power supply circuit which shows the 1st charge state at the time of a booster stopping based on embodiment of invention. It is a figure of the step-up power supply circuit which shows the 2nd charge state at the time of a booster stopping according to embodiment of invention. It is a figure of the step-up power supply circuit which shows the 3rd charge state at the time of a booster stopping based on embodiment of invention. It is a figure of the step-up power supply circuit which shows the 1st charge state at the time of operation | movement of the booster based on embodiment of invention. It is a figure of the step-up power supply circuit which shows the 2nd charge state at the time of operation | movement of the booster based on embodiment of invention. It is a figure of the step-up power supply circuit which shows the 3rd charge state at the time of operation | movement of the booster based on embodiment of invention. It is a figure explaining the abnormal sneak in the voltage in the step-up power supply circuit including the ground fault sensor not including the high-voltage selection circuit according to the embodiment of the invention. It is a figure of the modification of the high voltage | pressure selection circuit based on embodiment of invention.

  Hereinafter, modes for carrying out the invention (hereinafter referred to as “embodiments”) will be described with reference to the drawings.

  FIG. 1 is a circuit diagram of a boost power supply circuit 1 using a ground fault sensor 11 according to the present embodiment as an insulation state detection device. As shown in the figure, the boosting power supply circuit 1 boosts the positive potential of the primary high-voltage DC power supply B insulated from the ground potential portion by the booster 3 and supplies the boosted voltage to the secondary load 5. The ground fault and insulation state of the boost power supply circuit 1 are detected by a ground fault sensor 11 connected between the positive electrode and the negative electrode of the high-voltage DC power supply B.

  In addition, the code | symbol RLp in a figure is a primary side ground fault resistance (primary side + ground fault resistance), and a code | symbol RLn is a primary side negative side ground fault resistance (primary side-ground fault resistance). RLp2 indicates a secondary side ground fault resistance (secondary side + ground fault resistance), and RLn2 indicates a secondary side negative ground fault resistance (secondary side-ground fault resistance).

  The ground fault sensor 11 includes a bipolar flying capacitor C1, first and second switches SW1 and SW2 that selectively connect both poles of the flying capacitor C1 to the positive electrode and the negative electrode of the high-voltage DC power supply B, and the flying capacitor C1. From the third and fourth switches SW3, SW4, the current direction selection circuit 30, and the first and second switches SW1, SW2 that selectively connect the two electrodes to the control unit (microcomputer) 15 and the ground potential unit. And a high voltage selection circuit 20 on the upstream side (positive electrode side of the high voltage DC power supply B).

  In addition, since the basic measurement principle of the ground fault sensor 11 of this embodiment is the same as a general measurement principle, in the following description, it demonstrates paying attention to the characteristic point in this embodiment, and is general. The description of such principles is omitted as appropriate. In addition, the ground fault sensor 11 is provided with a switch for short-circuiting both poles of the flying capacitor C1 through a resistor for discharging, or one pole (upper pole in the figure) and a fourth switch SW4 described later are simultaneously provided. Control to discharge when on may be performed.

  The control unit 15 is constituted by a microcomputer and functions as a measuring device, and is operated by a predetermined low-voltage power supply (not shown) lower than the high-voltage DC power supply B. The high-voltage DC power source B is also insulated from the ground potential portion of the control unit 15. The first to fourth switches SW <b> 1 to SW <b> 4 are configured by, for example, optical MOSFETs, insulated from the high-voltage DC power supply B and controlled to be turned on / off by the control unit 15. The fifth switch SW5 is a power relay circuit for supplying high-voltage power to the ground fault sensor 11.

  A connection point between the control unit 15 and the third switch SW3 is grounded via the third resistor R3. A fourth resistor R4 is connected between the fourth switch SW4 and the ground potential portion. The first and third switches SW1 and SW3 on one end side of the flying capacitor C1 are connected in series, and a current direction switching circuit 30 is connected between the connection point T1 and one end of the flying capacitor C1. Yes.

  The current direction switching circuit 30 is a parallel circuit, one of which is a series circuit of a diode D0 and a first resistor R1 that are forwardly directed from the first and third switches SW1 and SW3 toward one end of the flying capacitor C1. The other is composed of a series circuit of a diode D1 and a second resistor R2 that are forward from one end of the flying capacitor C1 toward the first and third switches SW1 and SW3.

  Moreover, the high voltage | pressure selection circuit 20 is arrange | positioned upstream from 1st switch SW1, and is connected to 5th switch SW5 and a secondary side high voltage positive electrode as an upstream connection. The high voltage selection circuit 20 is connected to the first switch SW1 as a downstream connection.

  As shown in FIG. 2, the specific configuration of the high-voltage selection circuit 20 is such that primary and secondary selection diodes D21 and D22 are arranged in parallel as two diodes, both cathode sides are connected, and the first switch SW1 is connected to the first switch SW1. Connected. On the other hand, the anode of the diode D21 is connected to the primary high voltage positive electrode (fifth switch SW5). The anode of the second selection diode D22 is connected to the secondary high-voltage positive electrode of the booster 3. Therefore, no current flows from the ground fault sensor 11 to the primary side and secondary side high-voltage positive electrodes.

  Operations and processing for detecting a ground fault and an insulation state with the above configuration will be described with reference to FIGS. First, the case where the booster 3 is stopped will be described with reference to FIGS.

  In the boosting power supply circuit 1 in the first charging state (when the booster 3 is stopped) shown in FIG. 3, in order to detect a ground fault or an insulation state, first, the control unit 15 first and second switches SW1, SW2 And the third and fourth switches SW3 and SW4 are turned off. Accordingly, from the positive electrode of the high-voltage DC power supply B, the high-voltage selection circuit 20 (primary selection diode D21), the first switch SW1, the diode D0, the first resistor R1, the one end of the flying capacitor C1, the other end, A charging circuit that reaches the negative electrode of the high-voltage DC power supply B through the second switch SW2 is formed.

  In this charging circuit, the flying capacitor C1 charges a charge amount corresponding to the voltage of the high-voltage DC power supply B. By this charging, one end of the flying capacitor C1 becomes a positive electrode and the other end becomes a negative electrode.

  Subsequently, the control unit 15 turns off the first and second switches SW1 and SW2 and turns on the third and fourth switches SW3 and SW4. Thereby, the flying capacitor C1 is connected in parallel to the series circuit of the second resistor R2, the third resistor R3, and the fourth resistor R4. The potential corresponding to the difference between the voltages at both ends of the third resistor R3, which is obtained by dividing the charging voltage of the flying capacitor C1 by the second, third, and fourth resistors R2, R3, R4, is It is input to a predetermined A / D conversion port and measured. The controller 15 measures the charging voltage of the flying capacitor C1 from this measured value and the voltage dividing ratio of the second, third, and fourth resistors R2, R3, R4. Therefore, in the present embodiment, a measurement circuit is formed by the diode D1, the second resistor R2, the third switch SW3, the third resistor R3, the fourth switch SW4, and the fourth resistor R4.

  Then, the control unit 15 forms a discharge circuit to discharge the flying capacitor C1. Specifically, for example, the control unit 15 simultaneously turns on a predetermined switch (not shown) and a fourth switch SW4 provided between one end (positive electrode) of the flying capacitor C1 and the ground potential unit. The discharge is performed by discharging the first switch SW3 and the fourth switch SW4 at the same time.

  Next, the control unit 15 turns on the first and fourth switches SW1 and SW4 so as to be the second boosted power circuit 1 in the second charging state (when the booster 3 is stopped) shown in FIG. Then, the third switches SW2 and SW3 are turned off. Thereby, from the positive electrode of the high-voltage DC power supply B, the high-voltage selection circuit 20 (primary selection diode D21), the first switch SW1, the diode D0, the first resistor R1, the one end of the flying capacitor C1, the other end, A charging circuit that reaches the negative electrode of the high-voltage DC power source B is formed through the switch SW4, the fourth resistor R4, (ground potential part), and the negative-side ground fault resistor RLn.

  In this charging circuit, the flying capacitor C1 is charged with a charge amount corresponding to the negative-side ground fault resistance RLn. By this charging, one end of the flying capacitor C1 becomes a positive electrode and the other end becomes a negative electrode.

  Subsequently, the control unit 15 turns off the first and second switches SW1 and SW2 and turns on the third and fourth switches SW3 and SW4, so that the flying capacitor C1 according to the voltage of the high-voltage DC power supply B is turned on. The same measurement circuit as that for charging voltage measurement is formed. And the control part 15 measures the charging voltage of the flying capacitor C1 using this measuring circuit.

  When the measurement is completed, the control unit 15 forms a discharge circuit as described above to discharge the flying capacitor C1.

  Next, the control unit 15 turns on the second and third switches SW2 and SW3 and turns on the first power supply circuit 1 in the third charging state (when the booster 3 is stopped) shown in FIG. The fourth switches SW1 and SW4 are turned off. Thereby, from the positive electrode of the high-voltage DC power supply B, the positive side ground fault resistance RLp, (ground potential part), the third resistance R3, the third switch SW3, the diode D0, the first resistance R1, and the flying capacitor C1 A charging circuit that reaches the negative electrode of the high-voltage DC power supply B through one end, the other end, and the second switch SW2 is formed. In this charging circuit, the flying capacitor C1 is charged with a charge amount according to the positive-side ground fault resistance RLp. By this charging, one end of the flying capacitor C1 becomes a positive electrode and the other end becomes a negative electrode.

  Subsequently, the control unit 15 turns off the first and second switches SW1 and SW2 and turns on the third and fourth switches SW3 and SW4, so that the flying capacitor C1 according to the voltage of the high-voltage DC power supply B is turned on. The same measurement circuit as that at the time of measurement of the charging voltage or the measurement of the charging voltage of the flying capacitor C1 according to the negative ground fault resistance RLn is formed. And the control part 15 measures the charging voltage of the flying capacitor C1 using this measuring circuit.

  When the measurement is completed, the control unit 15 forms a discharge circuit as described above to discharge the flying capacitor C1.

  The charging voltage of the flying capacitor C1 according to the voltage of the high-voltage DC power source B, the charging voltage of the flying capacitor C1 according to the negative ground fault resistance RLn, and the positive ground fault resistance RLp measured as described above. By calculating the predetermined measurement theoretical formula using the charging voltage of the flying capacitor C1 according to the control unit 15, the control unit 15 is based on the values of the positive side ground fault resistance RLp and the negative side ground fault resistance RLn. The ground fault and insulation state of the high-voltage DC power source B can be detected.

  Next, a case where the booster 3 is operating will be described with reference to FIGS.

  In the boost power supply circuit 1 in the first charging state (when the booster 3 is operating) shown in FIG. 6, first, the control unit 15 turns on the first and second switches SW1 and SW2, and the third and fourth switches. SW3 and SW4 are turned off. Thereby, from the positive electrode (secondary high voltage positive electrode) of the booster 3, the high voltage selection circuit 20 (secondary selection diode D22), the switch SW1, the diode D0, the first resistor R1, the one end and the other end of the flying capacitor C1, In addition, a charging circuit that reaches the negative electrode of the high-voltage DC power supply B through the second switch SW2 is formed. At this time, as indicated by a broken line, the charging circuit by the high-voltage DC power source B shown in FIG. 3 is simultaneously formed.

  In the charging circuit using the booster 3, the flying capacitor C <b> 1 charges a charge amount corresponding to the boosted voltage of the booster 3. By this charging, one end of the flying capacitor C1 becomes a positive electrode and the other end becomes a negative electrode.

  Subsequently, the control unit 15 turns off the first and second switches SW1 and SW2 and turns on the third and fourth switches SW3 and SW4, and performs the measurement circuit in the same manner as when the booster 3 is stopped. Once formed, the charging voltage is measured. Then, after the measurement, the control unit 15 forms a discharge circuit and discharges the flying capacitor C1 in the same manner as when the booster 3 is stopped.

  Next, the control unit 15 turns on the first and fourth switches SW1 and SW4 so as to be the second boosted power circuit 1 in the second charging state (when the booster 3 is operating) shown in FIG. Then, the third switches SW2 and SW3 are turned off. Accordingly, from the positive electrode of the booster 3, the high voltage selection circuit 20 (secondary selection diode D22), the first switch SW1, the diode D0, the first resistor R1, the one end, the other end, and the fourth switch of the flying capacitor C1. A charging circuit that reaches the negative electrode of the high-voltage DC power supply B through SW4, the fourth resistor R4, (ground potential part), and the secondary-side negative ground fault resistor (secondary side-ground fault resistor) RLn2. Form. At this time, as indicated by a broken line, the charging circuit by the high-voltage DC power source B shown in FIG. 4 is simultaneously formed.

  In this charging circuit, the flying capacitor C1 is charged with a charge amount corresponding to the secondary-side negative ground fault resistance (secondary-ground fault resistance) RLn2. By this charging, one end of the flying capacitor C1 becomes a positive electrode and the other end becomes a negative electrode.

  Subsequently, the control unit 15 turns off the first and second switches SW1 and SW2 and turns on the third and fourth switches SW3 and SW4, and performs the measurement circuit in the same manner as when the booster 3 is stopped. Once formed, the charging voltage is measured. Then, after the measurement, the control unit 15 forms a discharge circuit and discharges the flying capacitor C1 in the same manner as when the booster 3 is stopped.

  Next, the control unit 15 turns on the second and third switches SW2 and SW3 and turns on the first power supply circuit 1 in the third charging state (when the booster 3 operates) shown in FIG. The fourth switches SW1 and SW4 are turned off. Thereby, from the positive electrode (secondary high voltage positive electrode) of the booster 3, the secondary side ground fault resistor RLp2, (ground potential part), the third resistor R3, the third switch SW3, the diode D0, A charging circuit is formed that reaches the negative electrode of the high-voltage DC power supply B through the first resistor R1, one end and the other end of the flying capacitor C1, and the second switch SW2. In this charging circuit, the flying capacitor C1 is charged with a charge amount corresponding to the secondary side ground fault resistance RLp2. By this charging, one end of the flying capacitor C1 becomes a positive electrode and the other end becomes a negative electrode.

  Subsequently, the control unit 15 turns off the first and second switches SW1 and SW2 and turns on the third and fourth switches SW3 and SW4, and performs the measurement circuit in the same manner as when the booster 3 is stopped. Once formed, the charging voltage is measured. Then, after the measurement, the control unit 15 forms a discharge circuit and discharges the flying capacitor C1 in the same manner as when the booster 3 is stopped.

  The charging voltage of the flying capacitor C1 according to the voltage boosted by the booster 3 and the charging voltage of the flying capacitor C1 according to the negative ground fault resistance RLn2 on the secondary side, measured as described above, and 2 By calculating a predetermined measurement theoretical formula using the charging voltage of the flying capacitor C1 corresponding to the secondary positive ground fault resistance RLp2, the control unit 15 can calculate the secondary positive ground fault resistance. It is possible to detect the ground fault or the insulation state of the booster 3 based on the values of RLp2 and the negative ground fault resistance RLn2 on the secondary side.

  Further, since the high voltage selection circuit 20 is provided, when the booster 3 operates, an abnormal potential wraparound from the secondary side occurs depending on the boosted secondary side voltage and the ground fault resistance value. However, this phenomenon can be prevented. For example, as described in Patent Document 2 described above, in the case of the boost power supply circuit 100 having the configuration of FIG. 9 in which the high voltage selection circuit 20 is not provided, the secondary side positive side and negative side ground fault resistors RLp2 When the potential VRL corresponding to the voltage division ratio of RLn2 exceeds the positive potential of the high-voltage DC power source B on the primary side, an abnormal potential wraparound from the secondary side occurs. However, the rectification directions of the primary and secondary selection diodes D21 and D22 constituting the high voltage selection circuit 20 are changed from upstream (primary high voltage positive electrode side) to downstream (first switch SW1 side in the ground fault sensor 11). Since it is set, the abnormal potential wraparound as described above does not occur.

  Moreover, the above-mentioned functions and effects can be realized only by adding a simple high-voltage selection circuit 20 composed of primary and secondary selection diodes D21 and D22, and existing circuits can be used as they are. Can reduce the actual investment burden. In addition, since the measurement principle and the like are not significantly changed, an effective boosting power supply circuit 1 (ground fault sensor 11) can be realized without substantially developing a control program.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it is understood by those skilled in the art that various modifications can be made to each of those components and combinations thereof, and such modifications are also within the scope of the present invention.

  For example, in the above-described embodiment, as the high-voltage selection circuit 20, a circuit including the primary and secondary selection diodes D21 and D22 is used, but the present invention is not limited to this. For example, as shown in FIG. 10, a high voltage selection circuit 20a having a configuration in which primary and secondary selection switches SW21 and SW22 are arranged in place of the primary and secondary selection diodes D21 and D22 may be employed.

  In this case, the primary and secondary selection switches SW21 and SW22 are controlled by the control unit 15. That is, when the booster 3 is stopped, the primary selection switch SW21 is controlled to be on and the secondary selection switch SW22 is controlled to be off. Further, when the booster 3 is in operation, the primary selection switch SW21 is turned off and the secondary selection switch SW22 is turned on.

  By adopting such a configuration, it is possible to select a high voltage with an intention according to the purpose and situation. Therefore, for example, by comparing the measured value of the high voltage on the selected side with the measured value of the cell voltage sensor 2 or the voltage value indicated by the booster 3, the failure detection of each circuit on the primary side and the secondary side can be performed. It becomes possible. Further, the high voltage selection circuit 20 may be configured by a switch in which one is a diode and the other is controlled by the control unit 15. Further, since it is not assumed that the high voltage selection circuit 20 goes around to the secondary side positive electrode of the booster 3, the boost power supply circuit 1 has a secondary selection diode D 22 that is a secondary selection unit of the high voltage selection circuit 20 and a secondary selection diode. The switch SW22 may not be provided.

DESCRIPTION OF SYMBOLS 1,100 Boost power supply circuit 2 Cell voltage sensor 3 Booster 11 Ground fault sensor 15 Control part 20, 20a High voltage selection circuit 30 Current direction selection circuit B High voltage DC power supply C1 Flying capacitor D0, D1 Diode D21 Primary selection diode D22 Secondary Selection diodes R1 to R4 First to fourth resistors SW1 to SW5 First to fifth switches SW21 Primary selection switch SW22 Secondary selection switch

Claims (3)

The flying capacitor charged with a voltage corresponding to a ground fault resistance by a DC power source insulated from a ground potential unit, and the flying capacitor insulated from the DC power source after being charged by the DC power source are charged to the flying capacitor. A measuring circuit for measuring voltage and a measuring circuit connected in series between the ground potential unit, and connected to a primary side of a boosting power supply circuit that boosts the positive potential of the DC power supply and supplies it to a load; An insulation state detection device that detects an insulation state of the boost power supply circuit based on a measurement result of a charging voltage of the flying capacitor by the measurement unit,
A high-voltage selection circuit that configures a circuit that is connected to the positive electrode on the primary side and the positive electrode on the secondary side through a separate path and guides a direct current to the flying capacitor;
The high-voltage selection circuit is connected to the primary-side positive electrode and is connected to the primary-side selection unit that functions to prevent a current from flowing to the primary-side positive electrode at least during the boosting operation, and to the secondary-side positive electrode. An insulation state detecting device.   The primary selection unit and the secondary selection unit allow current to flow from the primary side positive electrode and the secondary side positive electrode, and from the high voltage selection circuit to the primary side positive electrode and the secondary side positive electrode. The insulation state detection device according to claim 1, wherein the insulation state detection device is a rectifying unit connected so as not to pass a current.   The insulation state according to claim 1, wherein the primary selection unit and the secondary selection unit are switching means that are controlled to be turned on and off, and the primary selection unit is controlled to be turned off during a boosting operation. Detection device.

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