JP2017036938A - Voltage detection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage detection circuit with which it is possible to suppress current consumption when not detecting voltages and easily send electricity for voltage detection with greater reliability when detecting voltages.SOLUTION: First conduction path 11 and second conduction path 12 of a voltage detection circuit 1 are branched off from a prescribed conduction path 3, with a P-channel MOSFET 21 and an N-channel FET 22 provided, respectively. A control unit 7 exercises off control for turning both of the P-channel MOSFET 21 and the N-channel FET 22 off, first on control for setting the potential of a first input path 61 so that the P-channel MOSFET 21 goes on when the potential of the conduction path 3 exceeds a threshold potential, and second on control for setting the potential of a second input path 62 so that the N-channel FET 22 goes on when the potential of the conduction path 3 is at least below a threshold potential.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a voltage detection circuit.

  Many voltage detection circuits conventionally provided have a configuration in which a minute current is caused to flow through a path branched from a conductive path that is a voltage detection target, and a voltage state at a detection target position is grasped based on the minute current. As this type of voltage detection circuit, for example, a technique such as Patent Document 1 has been proposed. In this technique, a voltage dividing resistor is formed by connecting a voltage dividing resistor in series from a conductive path connected to a positive electrode of a battery. The circuit is branched, and a current is continuously supplied to the branch circuit. Then, by comparing the voltage at the connection point, which is an intermediate position between the two voltage dividing resistors, with a reference voltage, it is determined whether or not the battery voltage exceeds a predetermined voltage.

Japanese Patent Laid-Open No. 2002-296306

  However, as in the technique of Patent Document 1, in the configuration in which a very small current is always allowed to flow through the branched path, there is a problem that an increase in current consumption is unavoidable and a problem due to an increase in current consumption is likely to occur.

  For example, in FIG. 2, a general voltage detection circuit 101 similar to the technique of Patent Document 1 is simply shown. In this voltage detection circuit 101, a voltage dividing circuit in which resistors R11 and R12 are connected in series branches from a conductive path 101B connected to one electrode of the power storage unit C1, and this voltage dividing circuit is A minute current is continuously flowing. And in such an energized state, the voltage value output from the connection point which is an intermediate position between the resistors R11 and R12 is detected by the voltage detection unit 101A, thereby grasping the charging voltage of the power storage unit C1. However, in this configuration, since a minute current always flows from the power storage unit C1 to the voltage dividing circuit, the power storage unit C1 is continuously discharged, and the voltage of the power storage unit C1 is likely to decrease.

  As a configuration for solving this problem, for example, a configuration as shown in FIG. In the configuration of FIG. 3, a voltage dividing circuit in which resistors R21 and R22 are connected in series is branched from a conductive path 102B connected to the electrode of the power storage unit C1. A P-channel MOSFET 102D is provided as an element for turning on and off the current supply to the voltage dividing circuit.

  In the voltage detection circuit 102 shown in FIG. 3, the switch element Tr1 is controlled to be in the ON state by the control circuit 102C when the voltage is detected. At this time, when the current flows through the resistor R23, the gate potential of the MOSFET 102D becomes lower than the source potential (the potential of the conductive path 102B), and if the absolute value of the gate-source voltage Vgs is secured to some extent, the MOSFET 102D is turned on. Become. When the MOSFET 102D is thus turned on, a current flows through the voltage dividing circuit branched from the conductive path 102B, and a voltage value corresponding to the potential of the conductive path 102B is input to the voltage detection unit 102A. On the other hand, when no voltage is detected, the switch element Tr1 is controlled to be turned off by the control circuit 102C. At this time, the gate potential of the MOSFET 102D is kept substantially the same as the source potential (the potential of the conductive path 102B), so that the MOSFET 102D is turned off. Therefore, no current flows through the voltage dividing circuit branched from the conductive path 102B, and current consumption is suppressed.

  However, in the configuration of FIG. 3, when the charge amount of the power storage unit C1 decreases and the potential of the conductive path 102B becomes very small, the gate-source voltage Vgs of the MOSFET 102D cannot be sufficiently secured, and the MOSFET 102D is turned on. Can not. For example, in the configuration of FIG. 3, when the potential of the positive electrode of the power storage unit C1 is close to 0 V, the absolute value of the gate-source voltage Vgs of the MOSFET 102D does not reach a level at which the MOSFET 102D is turned on. Therefore, the voltage cannot be detected.

  On the other hand, in the voltage detection circuit 103 in FIG. 4, a voltage dividing circuit in which resistors R31 and R32 are connected in series branches from a conductive path 103B connected to the electrode of the power storage unit C1. An N-channel MOSFET 103D is provided as an element for turning on and off the current supply to the voltage dividing circuit.

  In the voltage detection circuit 103 shown in FIG. 4, when the voltage is detected, the switch element Tr2 is controlled to be turned on by the control circuit 103C, and a signal having a predetermined potential higher than the ground potential is input to the gate of the MOSFET 103D. Become. In this configuration, even if the charge amount of the power storage unit C1 becomes very low and the potential of the conductive path 103B becomes close to the ground potential, the MOSFET 103D can be turned on if the gate-source voltage Vgs is sufficiently secured. it can. Therefore, it can be said that it is easy to cope with the potential drop of the power storage unit C1.

  However, the MOSFET 103D used in the configuration of FIG. 4 is a high-side switch in which a load (voltage dividing circuit) is connected to the source side, and the source potential is substantially equal to the potential of the conductive path 103B when the MOSFET 103D is turned on. It has become. For this reason, at the time of ON control, the gate potential of the MOSFET 103D needs to be higher than the potential of the conductive path 103B. For this purpose, an external power supply VB is required in the gate driver. In particular, in order to surely turn on the MOSFET 103D even when the positive electrode potential of the power storage unit C1 is the maximum potential, the power source potential of the external power source VB is set to the maximum potential of the power storage unit C1 in order to sufficiently secure the gate-source voltage Vgs. Must be set high enough. For this reason, a booster circuit or the like for generating a signal with a high potential is required, which tends to increase the size and complexity of the circuit configuration.

  The present invention has been made based on the above-described circumstances, and provides a voltage detection circuit that can suppress current consumption when voltage is not detected and that can easily perform energization for voltage detection when voltage is detected. It is intended.

The voltage detection circuit of the present invention is
A first branch conductive path that branches from a predetermined conductive path that conducts to the power storage unit;
A second branch conductive path branched from the predetermined conductive path and provided in parallel with the first branch conductive path;
When the potential of the first input path is in a predetermined low potential state lower than the potential of the predetermined conductive path, the switch is turned on. A first switch element that energizes the first branch conductive path and turns off the first branch conductive path when the predetermined low potential state is released; and
When the potential of the second input path is in a predetermined high potential state higher than the potential of the predetermined conductive path, it is turned on when it is interposed in the second branch conductive path and connected to the second input path. A second switch element that turns on the second branch conductive path and turns off the second branch conductive path when the predetermined high potential state is released;
OFF control for setting the potential of the first input path and the second input path to be set to turn off both the first switch element and the second switch element, and the potential of the first input path. The first on-control that is set to generate the predetermined low potential state when the potential of the predetermined conductive path exceeds a threshold potential, and the potential of the second input path is at least equal to the potential of the predetermined conductive path A control unit that performs second on control that is set to cause the predetermined high potential state when the threshold potential is equal to or lower than the threshold potential;
A current flowing through at least one of the first branch conductive path and the second branch conductive path when at least one of the first branch conductive path and the second branch conductive path is energized. A detection unit for detecting a state of a voltage applied to the predetermined conductive path based on
Have

  In the present invention, two different types of switch elements (first switch element and second switch element) are used to switch each of the first branch conductive path and the second branch conductive path between an energized state and a non-energized state. Used. The control unit is configured to perform off control for turning off both the first switch element and the second switch element. When this off control is performed, the first branch conductive path and the second branch conductive path are both in a non-energized state, so that current consumption is suppressed compared to a configuration in which current always flows through the branch conductive path. It becomes easy to do.

  Further, the control unit sets the first input path potential so as to generate a predetermined low potential state when the potential of the predetermined conductive path exceeds the threshold potential, and the potential of the predetermined conductive path is The second ON control is performed to set the potential of the second input path so as to generate a predetermined high potential state at least when the potential is equal to or lower than the threshold potential. With such a configuration, when the potential of the predetermined conductive path exceeds the threshold potential, at least the first ON control is executed, a “predetermined low potential state” occurs, and the first switch element is turned on. Therefore, a current can be passed through the first branch conductive path. Further, when the potential of the predetermined conductive path is equal to or lower than the threshold potential, if the second on control is executed, a “predetermined high potential state” is generated, and the second switch element is turned on. A current can flow through the branch conductive path. That is, even if there is a voltage fluctuation in the predetermined conductive path, if two types of on-control are performed, a current can be reliably passed through one of the branch conductive paths. Therefore, it is possible to avoid the undetectable state due to the fact that the detection current cannot flow, and it becomes easier to detect the voltage state of the predetermined conductive path more reliably.

FIG. 3 is a circuit diagram schematically illustrating a voltage detection circuit according to the first embodiment. 5 is a circuit diagram schematically illustrating a voltage detection circuit of Comparative Example 1. FIG. 10 is a circuit diagram schematically illustrating a voltage detection circuit of a comparative example 2. FIG. 10 is a circuit diagram schematically illustrating a voltage detection circuit of Comparative Example 3. FIG.

Hereinafter, desirable modes of the present invention will be exemplified.
In the present invention, the control unit may be connected to a power supply conductive path having a predetermined power supply potential and a reference conductive path having a reference potential lower than the power supply potential. The threshold potential may be lower than the power supply potential and higher than the reference potential. Furthermore, the power supply potential may be lower than the potential of the predetermined conductive path when the power storage unit is fully charged.

  In this way, if the output of the external power supply (the power supply that determines the power supply potential of the power supply path) is suppressed, you can enjoy the benefits of suppressing the output of the external power supply, but when the power storage unit is nearly fully charged, a special boost If no means or the like is used, the “predetermined high potential state in which the potential of the second input path is higher than the potential of the predetermined conductive path connected to the power storage unit” cannot be generated. That is, the second switch element cannot be turned on when the power storage unit is nearly fully charged. However, in such a case, since the first switch element can be reliably turned on by the first on control, a detection current can be reliably passed through the first branch conductive path. As described above, the configuration capable of stably detecting the voltage can be realized in a form in which the output of the external power source is suppressed, which is particularly advantageous in designing and configuring the external power source. And this effect becomes so remarkable that the voltage output from an electrical storage part at the time of a full charge is high. On the other hand, when the potential of the predetermined conductive path becomes close to the reference potential due to the output decrease of the power storage unit, “a predetermined low potential state in which the potential of the first input path is lower than the potential of the predetermined conductive path connected to the power storage unit "Is not likely to occur. That is, the first switch element may not be turned on. However, in such a case, since the second switch element can be reliably turned on by the second on control, even if the potential of the predetermined conductive path connected to the power storage unit approaches the reference potential, the detection current Can be reliably flowed, and voltage can be detected stably.

  In the present invention, the control unit may perform the first on control and the second on control together at least for a predetermined time. In this case, the detection unit detects a state of a voltage applied to the predetermined conductive path based on a current flowing through at least one of the first branch conductive path and the second branch conductive path in the predetermined time. It is desirable that the configuration be

  A control method in which the first on-control and the second on-control are performed at a time difference if both the first on-control and the second on-control are performed in a predetermined time and the voltage state is grasped from the current flowing during the predetermined time. In comparison, the detection time can be easily shortened.

  The present invention may have a common conductive path. The first switch element is interposed between the predetermined conductive path and the common conductive path in the first branch conductive path, and the predetermined conductive path and the common conductive path are disposed in the second branch conductive path. The structure which the said 2nd switch element intervened between the paths may be sufficient. In this way, when the first branch conductive path and the second branch conductive path are connected to the common conductive path, the detection unit performs the predetermined conductive based on the current flowing through the common conductive path. It is desirable to have a configuration that detects the state of the voltage applied to the path.

  If the two types of on-control described above are performed, the certainty of current flowing through at least one of the branch conductive paths is increased, and a current reflecting the voltage state of the predetermined conductive path flows through the common conductive path. That is, if the common conductive path is monitored during the two types of ON control, the certainty that the voltage state of the predetermined conductive path can be detected increases. In particular, in this configuration, since it is not necessary to provide a voltage detection unit for each branch conductive path, it is easy to simplify and miniaturize a circuit for generating and acquiring a detection value from a current flowing through the branch conductive path.

<Example 1>
Hereinafter, Example 1 which is an example in which the present invention is embodied will be described.
The voltage detection circuit 1 shown in FIG. 1 is configured as, for example, a vehicle-mounted voltage detection circuit, and functions as a circuit that detects a voltage at a predetermined part of the vehicle-mounted device. In the example of FIG. 1, the voltage detection target conductive path 3 (hereinafter also referred to as the conductive path 3) is connected to the positive electrode of a power storage unit 90 formed of a vehicle-mounted capacitor or other secondary battery. Reference numeral 1 denotes a circuit for detecting the voltage of the conductive path 3. Since the voltage of the conductive path 3 reflects the charging voltage of the power storage unit 90, it can be said that the voltage detection circuit 1 is a circuit that detects the charging voltage of the power storage unit 90. In the configuration of FIG. 1, the negative electrode of the power storage unit 90 is connected to the ground.

  As shown in FIG. 1, the voltage detection circuit 1 includes a first branch conductive path 11 that branches from the voltage detection target conductive path 3, a branch from the conductive path 3, and a parallel connection with the first branch conductive path 11. Second branched conductive path 12. The first branch conductive path 11 and the second branch conductive path 12 are portions that can function as energization paths for flowing a current to a voltage dividing circuit 33 described later.

  P-channel MOSFET 21 (hereinafter also referred to as MOSFET 21) corresponds to an example of a first switch element, and is configured as a known P-channel MOSFET (metal-oxide-semiconductor field-effect transistor). The gate of the MOSFET 21 is connected to one end of a resistor 34, which will be described later, and the collector of an NPN transistor 42 (hereinafter also referred to as transistor 42) in a conductive manner, and the source is connected to the conductive path 3 in a conductive manner. Further, the drain of the MOSFET 21 is connected in a conductive manner to a common conductive path 30 described later. Note that the gate of the MOSFET 21 corresponds to an example of a first control terminal to which a signal is input. The source of the MOSFET 21 corresponds to an example of a first conduction terminal that conducts to the conductive path 3 that is a voltage detection target.

  The MOSFET 21 is turned on when the potential of the gate (first control terminal) is “predetermined low potential state” lower than the potential of the source (first conduction terminal), and the first branch conductive path 11 is turned on. Is energized. Specifically, when the absolute value of the gate-source voltage Vgs1 of the MOSFET 21 exceeds a predetermined threshold value Vth1, the MOSFET 21 is turned on, and the first branch conductive path 11 is turned on. Further, the MOSFET 21 is turned off when the “predetermined low potential state” is released, that is, when the absolute value of the gate-source voltage Vgs1 of the MOSFET 21 is equal to or lower than the predetermined threshold Vth1, and the first branch conductive path 11 is in a non-energized state.

  The N-channel MOSFET 22 (hereinafter also referred to as MOSFET 22) corresponds to an example of a second switch element, and is configured as a known N-channel MOSFET (metal-oxide-semiconductor field-effect transistor). The MOSFET 22 has a gate connected to one end of a resistor 36, which will be described later, and a collector of a PNP transistor 44, and a drain connected to the conductive path 3. Further, the source of the MOSFET 22 is connected in a conductive manner to a common conductive path 30 described later. Note that the gate of the MOSFET 22 corresponds to an example of a second control terminal to which a signal is input. The drain of the MOSFET 22 corresponds to an example of a second conduction terminal that conducts to the conductive path 3 to be detected.

  The MOSFET 22 is turned on when the potential of the gate (second control terminal) is “predetermined high potential state” higher than the potential of the drain (second conduction terminal), and the second branch conductive path 12 is operated. Is energized. Specifically, the MOSFET 22 is a high-side switch connected to a higher potential side than a voltage dividing circuit 33 described later, and the source potential is substantially equal to the drain potential during the on-operation. Since the MOSFET 22 is turned on when the gate-source voltage Vgs2 exceeds the predetermined threshold Vth2, the MOSFET 22 is in a “predetermined high potential state” when the potential difference between the gate and the drain exceeds the predetermined threshold Vth2. Turns on. Further, the MOSFET 22 is turned off when the “predetermined high potential state” is released, that is, when the potential difference between the gate and the drain becomes lower than the predetermined threshold value Vth2, and the second branch conductive path 12 is turned off. Turn off the power.

  One end of a common conductive path 30 (hereinafter also referred to as a conductive path 30) is connected to the first branch conductive path 11 and the second branch conductive path 12. The other end side of the conductive path 30 is connected to the ground. In this conductive path 30, a voltage dividing circuit 33 is configured in such a manner that two voltage dividing resistors 31, 32 are connected in series, and an intermediate portion connecting the voltage dividing resistors 31, 32 is a voltage detecting unit 5 described later. Connected to the input terminal.

  In the configuration of FIG. 1, the MOSFET 21 is interposed between the conductive path 3 for voltage detection and the common conductive path 30 in the first branch conductive path 11, and the drain of the MOSFET 21 is electrically connected to the conductive path 30. In the second branch conductive path 12, the MOSFET 22 is interposed between the conductive path 3 and the conductive path 30, and the source of the MOSFET 22 is conducted to the conductive path 30. With such a configuration, the first branch conductive path 11 and the second branch conductive path 12 are connected to the common conductive path 30, and the current flowing through the first branch conductive path 11 and the second branch conductive path 12 flow. The current flows through the conductive path 30.

  For example, if the first branch conductive path 11 and the second branch conductive path 12 are both energized, a current that is the sum of the currents flowing through both the conductive paths flows through the conductive path 30. Further, if the first branch conductive path 11 is in an energized state and the second branch conductive path 12 is in a non-energized state, a current flowing through the first branch conductive path 11 flows in the conductive path 30. Conversely, if the second branch conductive path 12 is in the energized state and the first branch conductive path 11 is in the non-energized state, the current flowing through the second branch conductive path 12 flows through the conductive path 30. In other words, if at least one of the first branch conductive path 11 and the second branch conductive path 12 is energized, a current corresponding to the potential of the conductive path 3 flows through the common conductive path 30. .

  The control unit 7 includes a control circuit 8 that can output a signal, a switching circuit 9A that switches a gate potential of the MOSFET 21 in accordance with a signal from the control circuit 8, and a gate potential of the MOSFET 22 in accordance with a signal from the control circuit 8. And a switching circuit 9B for switching.

  The control unit 7 is connected to a power supply conductive path 46 having a predetermined power supply potential and a reference conductive path 48 having a reference potential lower than the power supply potential, and specifically, at least a switching circuit. 9B is connected to the power supply conductive path 46. Further, at least the switching circuits 9A and 9B are connected to the reference conductive path 48. The power supply conductive path 46 is configured as a power supply conductive path to which a power supply voltage is applied from an external power supply V1 configured by a voltage generation circuit (a known booster circuit or the like), and is maintained at a constant power supply potential. The reference conductive path 48 is configured as a ground conductive path, and is maintained at a constant ground potential (0 V).

  The control circuit 8 is constituted by a microcomputer, other drive circuits, and the like. For each of the signal lines 51 and 52, a high level signal (for example, a signal of 5V) having a constant potential and a low level signal having a constant potential are provided. (For example, a 0 V signal) can be output.

  The switching circuit 9A includes a resistor 34 and an NPN transistor 42 (hereinafter also referred to as transistor 42). The resistor 34 is connected between the conductive path 3 and the gate of the MOSFET 21. The transistor 42 has a collector connected to the gate of the MOSFET 21 and one end of the resistor 34, and an emitter connected to a reference conductive path 48 (conductive path for ground) and is grounded. The base of the transistor 42 is electrically connected to the first output port of the control circuit 8 via the signal line 51. In the switching circuit 9A, a high level signal or a low level signal is input from the control circuit 8 to the base of the transistor 42, and the transistor 42 is turned on and off in accordance with the signal input to the base. The base potential of the MOSFET 21 is switched by switching the transistor 42 on and off.

  The switching circuit 9B includes a resistor 36 and a PNP transistor 44 (hereinafter also referred to as transistor 44). One end of the resistor 36 is connected to the gate of the MOSFET 22 and the collector of the transistor 44, and the other end is connected to the reference conductive path 48 (ground conductive path) and grounded. The transistor 44 has an emitter connected to the power supply conductive path 46 and a collector connected to the gate of the MOSFET 22 and one end of the resistor 36. The base of the transistor 44 is electrically connected to the second output port of the control circuit 8 through the signal line 52. In the switching circuit 9B, a high level signal or a low level signal is input from the control circuit 8 to the base of the transistor 44, and the on / off state of the transistor 44 is switched according to the signal input to the base. Then, the base potential of the MOSFET 22 is switched by switching the transistor 44 on and off. In this configuration, the power supply potential of the power supply conductive path 46 connected to the emitter of the transistor 44 is smaller than the potential of the positive electrode when the power storage unit 90 is fully charged, and the power storage unit 90 is fully charged. It is smaller than the potential of the conductive path 3 at this time.

  The voltage detection unit 5 corresponds to an example of a detection unit, and is configured as an integrated circuit including, for example, an AD converter that converts an analog voltage value into digital data, a CPU that performs arithmetic processing, a memory, and the like. The voltage detection unit 5 detects the voltage based on the current flowing through at least one of the branch conductive paths when at least one of the first branch conductive path 11 and the second branch conductive path 12 is energized. The state of the voltage applied to the target conductive path 3 is detected. Specifically, if either of the MOSFETs 21 and 22 is in an on state, a current corresponding to the voltage applied to the conductive path 3 flows through the common conductive path 30. The state of the voltage applied to the conductive path 3 is detected based on the flowing current. In the example of FIG. 1, the voltage dividing circuit 33 is configured in the common conductive path 30, and when at least one of the MOSFETs 21 and 22 is in the ON state, the conductive portion (connection point) between the two voltage dividing resistors 31 and 32. ) Is proportional to the potential of the conductive path 3. And the voltage detection part 5 becomes a structure which detects the electric potential of this electroconductive part (connection point) as an input value.

Next, the operation of the voltage detection circuit 1 will be described.
In the voltage detection circuit 1 of FIG. 1, the off control is performed by the control unit 7 when voltage detection is not performed. Specifically, the control circuit 8 outputs a low level signal to the signal line 51 and outputs a high level signal to the signal line 52. The NPN transistor 42 is continuously turned off by continuously outputting a low level signal from the control circuit 8 to the signal line 51. As a result, the gate and the source of the P-channel type MOSFET 21 are at the same potential, and the MOSFET 21 is kept off. Further, the PNP transistor 44 is turned off by continuing to output a high level signal from the control circuit 8 to the signal line 52. As a result, the gate potential of the N-channel MOSFET 22 becomes low level (ground potential), and the MOSFET 22 continues to be turned off. When such an off-control is performed, since both the first branch conductive path 11 and the second branch conductive path 12 are in a non-energized state, as compared with a configuration in which current always flows through the branch conductive path. It becomes easy to suppress current consumption.

  On the other hand, at the timing of voltage detection, the control unit 7 issues a first on-control command to the MOSFET 21 and a second on-control command to the MOSFET 22. The first on-control command and the second on-control command may be out of timing or may be performed at the same timing. Hereinafter, an example in which the control unit 7 performs both the first on-control command and the second on-control command at least for a predetermined time will be described as a representative example.

  In this configuration, the first input path 61 is connected to the gate of the MOSFET 21, and the first input path 61 is a conductive path maintained at the same potential as the gate of the MOSFET 21. Based on such a configuration, the control unit 7 sets the potential of the first input path 61 so as to generate a “predetermined low potential state” when the potential of the conductive path 3 exceeds the first potential. (First ON control) is performed. Specifically, the control unit 7 causes the base current to flow through the base of the transistor 42 by causing the control circuit 8 to output a high level signal to the signal line 51 for a predetermined time, thereby turning on the transistor 42. By this operation, a current is passed through the resistor 34, and the potential of the first input path 61, that is, the gate potential of the MOSFET 21 is switched to a potential lower than the potential of the conductive path 3 by the voltage drop across the resistor 34. The gate potential switching control performed by the control unit 7 in this way is “first on control”. When such control is performed, the MOSFET 21 is turned on when the potential of the conductive path 3 exceeds the first potential. The first potential is higher than the potential of the reference conductive path 48 (ground potential) and lower than the potential of the power supply conductive path 46 (power supply potential), and corresponds to the threshold potential.

  Specifically, the MOSFET 21 is turned on when the absolute value of the gate-source voltage Vgs1 is larger than the threshold value Vth1, and is turned off when the absolute value of Vgs1 is less than or equal to the threshold value Vth1. That is, the “first potential” (threshold potential) is the potential of the conductive path 3 when the absolute value of the gate-source voltage Vgs1 of the MOSFET 21 becomes the threshold Vth1 when the transistor 42 is turned on. If the potential of the conductive path 3 is high enough to exceed the “first potential” (threshold potential), the MOSFET 21 is turned on.

  Further, the second input path 62 is connected to the gate of the MOSFET 22, and the second input path 62 is a conductive path that is kept at the same potential as the gate of the MOSFET 22. Based on such a configuration, the control unit 7 is based on the second input path 62 so as to generate a “predetermined high potential state” when at least the potential of the conductive path 3 is equal to or lower than the first potential (threshold potential). (Second ON control) is set. Specifically, the control unit 7 outputs a low level signal to the signal line 52 at “predetermined time” when the control circuit 8 outputs a high level signal to the signal line 51. Thus, by outputting a low level signal from the control circuit 8 to the signal line 52, a base current is caused to flow through the base of the transistor 44, and the transistor 44 is turned on. By this operation, a current is passed through the resistor 36, and the potential of the second input path 62, that is, the gate potential of the MOSFET 22 is switched to a constant potential higher than the ground potential. The gate potential switching control performed by the control unit 7 in this way is the “second ON control”. When such control is performed, the MOSFET 22 is turned on when the potential of the conductive path 3 is lower than the predetermined second potential. The second potential is lower than the potential of the power supply conductive path 46 (power supply potential) and higher than the potential of the reference conductive path 48 (ground potential), and is set higher than the “first potential” (threshold potential). Yes. That is, when the potential of the conductive path 3 is equal to or lower than the first potential (threshold potential), the potential of the conductive path 3 is always lower than the second potential, and the MOSFET 22 is turned on. .

  Specifically, the MOSFET 22 is turned on when the gate-source voltage Vgs2 is larger than the threshold value Vth2, and is turned off when Vgs2 is less than or equal to the threshold value Vth2. That is, the “second potential” is a potential of the conductive path 3 when the gate-source voltage Vgs2 of the MOSFET 22 becomes the threshold value Vth2 when the transistor 44 is turned on. In this configuration, the resistance value of the resistor constituting the voltage dividing circuit 33 is sufficiently larger than the on-resistance of the MOSFET 22, and the drain and the source of the MOSFET 22 have substantially the same potential when the MOSFET 22 is on. Therefore, the potential of the conductive path 3 when the potential difference between the drain and gate of the MOSFET 22 substantially matches the threshold value Vth2 is the “second potential”, and the potential of the conductive path 3 is low enough to be lower than the “second potential”. In this case, the MOSFET 21 is turned on.

  Based on the current flowing through the common conductive path 30 during the “predetermined time” when both the first on-control command and the second on-control command are performed by the control unit 7 as described above, the voltage detection unit 5 The state of the voltage applied to the conductive path 3 is detected. Specifically, when both the first on-control command and the second on-control command are issued at the “predetermined time”, at least one of the MOSFET 21 and the MOSFET 22 is turned on, and in this case, the common conductive path A current corresponding to the potential of the conductive path 3 flows through 30.

  In the voltage dividing circuit 33 configured by the common conductive path 30, the resistance values of the voltage dividing resistors 31 and 32 are sufficiently larger than the ON resistances of the MOSFETs 21 and 22. For this reason, if either of the MOSFETs 21 and 22 is in the on state, the potential of the conductive portion (connection point) between the two voltage dividing resistors 31 and 32 becomes a value substantially proportional to the potential of the conductive path 3, and voltage detection The unit 5 detects this value as an input value. Thereby, the voltage detector 5 can grasp the voltage of the conductive path 3.

  As described above, the voltage detection circuit 1 shown in FIG. 1 can perform two types of ON control for the MOSFETs 21 and 22 provided in parallel. For this reason, when the potential of the conductive path 3 to be voltage-detected is high enough to exceed the first potential, the P-channel MOSFET 21 is turned on by at least the first on control to flow a current through the first branch conductive path 11. be able to. On the other hand, when the potential of the conductive path 3 to be voltage detected is low enough to be lower than the second potential, the N-channel MOSFET 22 is turned on by at least the second on control to pass a current through the second branch conductive path 12. be able to. In other words, even if there is a voltage fluctuation in the conductive path 3 to be detected, if two types of on-control are performed, the possibility that a current flows through one of the branched conductive paths is increased. Therefore, it becomes easy to avoid the undetectable state due to the fact that the detection current cannot be passed, and as a result, it becomes easier to detect the voltage state of the conductive path 3 to be detected with more certainty.

  Specifically, the first potential that is a condition for performing the first on control is lower than the second potential that is a condition for performing the second on control. In this configuration, the MOSFET 22 can be turned on when the potential of the conductive path 3 is equal to or lower than the first potential. Further, when the potential of the conductive path 3 exceeds the first potential and is lower than the second potential, both the MOSFETs 21 and 22 can be turned on. When the potential of the conductive path 3 is equal to or higher than the second potential, the MOSFET 21 can be turned on. In other words, the current can be reliably passed through the voltage dividing circuit 33 in a range from the state where the positive electrode potential of the power storage unit 90 is close to 0 V to the maximum potential (potential at full charge), and voltage detection can be performed in a wider range. It can be carried out.

  Further, in this configuration, the power supply potential of the power supply conductive path 46 is lower than the positive electrode potential when the power storage unit 90 is fully charged. For this reason, the configuration capable of stably detecting the voltage even when the conductive path 3 to be voltage-detected becomes a high potential in a form that suppresses the output of the external power source V1 (the power source that determines the power source potential of the power source conductive path 46). In particular, this is advantageous in designing and configuring the external power supply V1. And this effect becomes so remarkable that the positive electrode electric potential at the time of a full charge is high.

  In addition, as described above, the first on-control command and the second on-control command are issued together at a predetermined time, and the current flowing through the branch conductive path at the predetermined time (that is, the common conductive path 30 at the predetermined time). If the voltage state is grasped from the flowing current), the detection time can be easily shortened. For example, in the control method in which the first on-control and the second on-control are performed with a time difference, it takes twice as long, but the configuration in FIG. 1 is a configuration that enables these to be performed at the same time. It is easy to shorten the voltage detection time.

  Further, in this configuration, the voltage state of the conductive path 3 can be grasped from the current flowing through the common conductive path 30 regardless of whether the first on-control or the second on-control is performed. There is no need to provide a voltage detector. For this reason, it becomes easy to simplify and miniaturize a circuit for generating and acquiring a detection value from the current flowing through the branch conductive path.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In the above-described embodiment, the example in which the first on-control and the second on-control are performed at the same time has been shown. However, the timing is shifted and detection by the voltage detection unit 5 is performed at each timing. May be.
(2) In the above-described embodiment, the configuration in which the signal is output from the control circuit 8 to the two paths (signal lines 51 and 52) is shown, but the present invention is not limited to this example. For example, the signal line 52 may be omitted and a circuit for inverting the output of the signal line 51 may be provided so that the output from the signal line 51 is inverted and applied to the base of the transistor 44. In this way, the signal output port of the control circuit 8 can be reduced.
(3) In the above-described embodiment, the configuration for detecting the voltage of the conductive path 3 connected to the positive electrode of the power storage unit 90 has been exemplified. However, the part to be the voltage detection target is not limited to this, and various circuits and components The various parts can be voltage detection targets.
(4) In the above-described embodiment, the voltage detection is performed by providing the voltage dividing circuit 33 in the common conductive path 30, but the first branch conductive path 11 and the second branch conductive path 12 are separately divided. A voltage circuit may be provided, and voltage detection may be performed separately in each voltage dividing circuit.

DESCRIPTION OF SYMBOLS 1 ... Voltage detection circuit 3 ... Conduction path (predetermined conduction path) of voltage detection object
5 ... Voltage detector (detector)
DESCRIPTION OF SYMBOLS 7 ... Control part 11 ... 1st branch conductive path 12 ... 2nd branch conductive path 21 ... P channel MOSFET (1st switch element)
22 ... N-channel MOSFET (second switch element)
DESCRIPTION OF SYMBOLS 30 ... Common conductive path 46 ... Power supply conductive path 48 ... Reference | standard conductive path 61 ... 1st input path 62 ... 2nd input path 90 ... Power storage part

Claims (4)

A first branch conductive path that branches from a predetermined conductive path that conducts to the power storage unit;
A second branch conductive path branched from the predetermined conductive path and provided in parallel with the first branch conductive path;
When the potential of the first input path is in a predetermined low potential state lower than the potential of the predetermined conductive path, the switch is turned on. A first switch element that energizes the first branch conductive path and turns off the first branch conductive path when the predetermined low potential state is released; and
When the potential of the second input path is in a predetermined high potential state higher than the potential of the predetermined conductive path, it is turned on when it is interposed in the second branch conductive path and connected to the second input path. A second switch element that turns on the second branch conductive path and turns off the second branch conductive path when the predetermined high potential state is released;
OFF control for setting the potential of the first input path and the second input path to be set to turn off both the first switch element and the second switch element, and the potential of the first input path. The first on-control that is set to generate the predetermined low potential state when the potential of the predetermined conductive path exceeds a threshold potential, and the potential of the second input path is at least equal to the potential of the predetermined conductive path A control unit that performs second on control that is set to cause the predetermined high potential state when the threshold potential is equal to or lower than the threshold potential;
A current flowing through at least one of the first branch conductive path and the second branch conductive path when at least one of the first branch conductive path and the second branch conductive path is energized. A detection unit for detecting a state of a voltage applied to the predetermined conductive path based on
A voltage detection circuit. The control unit is connected to a power supply conductive path having a predetermined power supply potential and a reference conductive path having a reference potential lower than the power supply potential,
The threshold potential is a potential lower than the power supply potential and higher than the reference potential,
The voltage detection circuit according to claim 1, wherein the power supply potential is lower than the potential of the predetermined conductive path when the power storage unit is in a fully charged state. The control unit performs the first on control and the second on control together at least for a predetermined time,
The detection unit is configured to detect a state of a voltage applied to the predetermined conductive path based on a current flowing through at least one of the first branch conductive path and the second branch conductive path in the predetermined time. The voltage detection circuit according to claim 1 or claim 2. Have a common conductive path,
The first switch element is interposed between the predetermined conductive path and the common conductive path in the first branch conductive path, and the predetermined conductive path and the common conductive path in the second branch conductive path The first branch conductive path and the second branch conductive path are connected to the common conductive path in a configuration in which the second switch element is interposed between
4. The voltage detection according to claim 1, wherein the detection unit is configured to detect a state of a voltage applied to the predetermined conductive path based on a current flowing through the common conductive path. 5. circuit.

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