JP2010178528A - Energy storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the possibility of voltage generation in a current detection circuit by malfunction. <P>SOLUTION: The energy storage device includes: an energy storage unit 33 in which electric power of a main power supply 15 is stored; a charging circuit 29 and the current detection circuit 31 which are connected between the main power supply 15 and the energy storage unit 33; a step-up circuit 47 connected to the energy storage unit 33; a selecting circuit 81 by which a higher voltage out of an output voltage Vout of the step-up circuit 47 and a voltage Vb of the main power supply 15 is output as a driving voltage Vcc of the current detection circuit 31; and a control circuit 71 connected to the charging circuit 29, the current detection circuit 31 and the step-up circuit 47. When charging the energy storage unit 33, a control circuit 71 operates the step-up circuit 47 if the voltage Vb of the main power supply 15 becomes equal to or higher than a prescribed voltage Vbr, and also controls the charging circuit 29 so that a current output I of the current detection circuit 31 becomes a prescribed current Ir, and a voltage Vc of the energy storage unit 33 reaches a charging completion voltage Vcs. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power storage device as an auxiliary power source that stores power in a power storage unit and discharges it when necessary.

  Conventionally, for example, Patent Document 1 proposes a power storage device that stores power in a plurality of power storage elements as an auxiliary power source for backup. FIG. 3 is a block circuit diagram of such a power storage device. As the plurality of power storage elements 101, for example, large-capacity electric double layer capacitors are used. In the example of FIG. 3, three power storage elements 101 are connected in series. The storage element 101 is connected to a series circuit of a charging element 103 for controlling the charging and a charging current detecting means 105 for detecting a charging current. A DC power source 107 as a main power source is connected to this series circuit. Furthermore, a discharge element 109 that controls the discharge is connected to the power storage element 101. A load (not shown) is connected to the discharge element 109. Each power storage element 101 is connected to a voltage detection means 111 for detecting the voltage.

The charging current value and the voltage value detected by the charging current detection unit 105 and the voltage detection unit 111 are input to the control unit 113. The control unit 113 controls the charging element 103 and the discharging element 109 based on the input value. That is, the control unit 113 charges the storage element 101 so that the charging current is constant at the beginning of charging, and when the storage element 101 reaches a preset voltage, the charging element is set so that the storage element 101 becomes a constant voltage. 103 is controlled. Further, the control unit 113 controls the discharge element 109 when the DC power source 107 is abnormal to discharge the power of the power storage element 101 and back up the power to the load.
JP 2006-320170 A

  According to the power storage device described above, the power of the power storage element 101 can be supplied to the load when the main power supply is abnormal, so that the load can be stably operated. There has been a problem that the charging current output value of the means 105 may become abnormal.

  That is, the charging current detection means 105 is mainly composed of a shunt resistor and an operational amplifier, the output of the operational amplifier is output as a charging current value, and the driving power for the operational amplifier is supplied from the DC power supply 107. In the case where it is necessary at the same time that the full charge voltage of the entire storage element 101 is substantially equal to the voltage of the DC power source 107, the above-described problem may occur. The reason why this problem occurs is as follows.

  When the full charge voltage of the entire storage element 101 becomes substantially equal to the voltage of the DC power supply 107, the voltage input to the operational amplifier becomes substantially equal to the voltage of the DC power supply 107. On the other hand, the driving voltage of the operational amplifier is equal to the voltage of the DC power source 107. Therefore, when the power storage element 101 is nearly fully charged, the driving voltage of the operational amplifier and the voltage input thereto are almost equal.

  Under such a state, the output of the operational amplifier becomes a voltage that is equal to the vicinity of the drive voltage, and there is a possibility that a charging current value larger than the current value that actually charges the storage element 101 is output. It was. This is because the voltage input to the operational amplifier is obtained by subtracting a voltage drop width (specifically, for example, about 1.5 V) determined by a semiconductor element in an internal circuit constituting the operational amplifier from the driving voltage of the operational amplifier. This is because the operational amplifier operates normally when the value is smaller than the value. Therefore, if the input voltage of the operational amplifier is larger than the above-described subtraction value, the operation of the operational amplifier becomes indefinite, and in the range until the input voltage of the operational amplifier becomes substantially equal to the drive voltage, as described above, The driving voltage is output from the operational amplifier, and when the input voltage of the operational amplifier exceeds the driving voltage, the output of the operational amplifier becomes zero.

  From the above, depending on the configuration of the charging current detection unit 105, its drive voltage, and the full charge voltage of the entire storage element 101, a malfunction voltage occurs in the charging current detection unit 105, and the charging current value becomes an abnormal value. There was a problem that it might become.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a power storage device capable of reducing the possibility of malfunction voltage generation in a current detection circuit and performing highly accurate charge control.

  In order to solve the conventional problem, a power storage device of the present invention is a power storage device electrically connected between a main power source and a load, and the power storage device stores power of the main power source. A series circuit including a charging circuit electrically connected between the main power supply and the power storage unit, and a current detection circuit, a main power supply voltage detection circuit electrically connected to the main power supply, and the power storage The higher one of the output voltage (Vout) of the booster circuit and the voltage (Vb) of the main power supply is the drive voltage of the current detector circuit, and the booster circuit electrically connected to the unit A selection circuit that outputs as (Vcc), and a control circuit connected to the charging circuit, current detection circuit, booster circuit, main power supply voltage detection circuit, and power storage unit voltage detection circuit, the current detection circuit, A shunt resistor and the shunt resistor An operational amplifier having input terminals connected to both ends of the resistor, and an output of the selection circuit is connected to the operational amplifier, and the control circuit, when charging the power storage unit, When the main power supply voltage (Vb) detected by the main power supply voltage detection circuit becomes equal to or higher than a predetermined voltage (Vbr), the booster circuit is operated and the current output (I) of the current detection circuit is set to a predetermined current ( The charging circuit is controlled such that the voltage (Vc) of the power storage unit detected by the power storage unit voltage detection circuit reaches the charge completion voltage (Vcs).

  According to the power storage device of the present invention, the booster circuit is connected to the power storage unit, and the higher one of the output voltage (Vout) of the booster circuit and the voltage (Vb) of the main power supply is the drive voltage (Vcc) of the current detection circuit. Is selected, and when the voltage (Vb) of the main power source is equal to or higher than the predetermined voltage (Vbr), the booster circuit is operated to charge the power storage unit. As a result, the drive voltage (Vcc) of the current detection circuit when detecting the current value is always equal to or higher than the predetermined voltage (Vbr), and the charging of the power storage unit proceeds and the voltage (Vc) increases as the voltage (Vc) increases. When the output voltage (Vout) of the circuit exceeds the voltage (Vb) of the main power supply, the output voltage (Vout) of the booster circuit is applied to the current detection circuit by the selection circuit. Therefore, the drive voltage (Vcc) of the current detection circuit increases as the power storage unit is charged, so that it does not approach the voltage (Vc) of the power storage unit, and the possibility of malfunction voltage generation can be reduced. Therefore, there is an effect that a power storage device capable of controlling charging with high accuracy can be obtained.

The best mode for carrying out the present invention will be described below with reference to the drawings. Here, a case where the power storage device is used as an auxiliary power source for vehicle backup will be described.
(Embodiment)
FIG. 1 is a block circuit diagram of a power storage device according to an embodiment of the present invention. FIG. 2 is a time characteristic diagram of various voltages during charging of the power storage device according to the embodiment of the present invention. In FIG. 1, thick lines indicate power system wiring, and thin lines indicate signal system wiring.

  In FIG. 1, the power storage device 11 is electrically connected between a main power supply 15 and a load 17. The main power source 15 is a vehicle battery, and the load 17 is an electrical component mounted on the vehicle. Therefore, in the power storage device 11, a large current flows through the load 17, an abnormality of the main power supply 15 itself, or an abnormality such as a disconnection or a ground fault occurs in the surrounding power system wiring. When the voltage Vb decreases and sufficient power cannot be supplied to the load 17, the stored power is supplied to the load 17 to continue the operation. Although not shown, the main power supply 15 is also electrically connected to a generator that generates power with an engine.

  The power storage device 11 has the following configuration. First, the main power supply voltage detection circuit 21 is electrically connected to the output of the main power supply 15 via the input terminal unit 19. Thereby, the electrical storage apparatus 11 can monitor the voltage Vb of the main power supply 15, and can detect the voltage fall. In addition, the anodes of the first diode 23 and the second diode 25 are electrically connected to the input terminal portion 19, respectively. Here, the cathode of the first diode 23 is electrically connected to the output terminal portion 27. Since the load 17 is connected to the output terminal portion 27, the voltage Vb of the main power supply 15 is within a normal range (for example, from 10.5V that is the lowest drive voltage of the load 17 to 14V that is the power generation voltage of the generator). If present, power is supplied from the main power supply 15 to the load 17 via the input terminal unit 19, the first diode 23, and the output terminal unit 27.

  On the other hand, the cathode of the second diode 25 is electrically connected to the power storage unit 33 through a series circuit including a charging circuit 29 and a current detection circuit 31. Therefore, the series circuit is configured to be electrically connected between the main power supply 15 and the power storage unit 33. Here, the second diode 25 is provided so that the power of the power storage unit 33 is not supplied to the main power supply 15 side when the power stored in the power storage unit 33 is supplied to the load 17.

  The charging circuit 29 is a circuit that charges the power storage unit 33 with the power of the main power supply 15 by a control circuit, which will be described later. Specifically, the charging circuit 29 is charged by controlling the gate voltage of a field effect transistor (hereinafter referred to as FET) (not shown). The current and charging voltage are controlled.

  The current detection circuit 31 includes a shunt resistor 35, an operational amplifier 37 having input terminals connected to both ends thereof, and a resistor 39 connected between the output of the operational amplifier 37 and the ground. Therefore, the operational amplifier 37 detects a voltage drop in the shunt resistor 35 caused by the current flowing when the power storage unit 33 is charged, amplifies the current to a predetermined multiple, and converts it into a voltage value to obtain a current output I. .

  The power storage unit 33 is configured by connecting a plurality of power storage elements (here, electric double layer capacitors are used) in series. In the present embodiment, six power storage elements having a rated voltage of 2.5 V are connected in series so that the charging completion voltage Vcs of the power storage unit 33 is 13 V. In this case, the voltage of each power storage element at the completion of charging is about 2.17 V, so the design is designed to incorporate a margin with respect to the rated voltage. The power storage unit 33 may appropriately change the number of the power storage elements according to the power required by the load 17 or may have a series-parallel configuration.

  The power storage unit 33 is electrically connected to the output terminal unit 27 via the discharge circuit 41 and the third diode 43. The discharge circuit 41 is also configured by an FET as in the charging circuit 29. However, in order to directly supply the electric power of the power storage unit 33 to the load 17 during discharging, the FET is used as a switch in the present embodiment. I have control. Further, the discharge circuit 41 has a function of connecting the positive electrode of the power storage unit 33 to the ground via a built-in discharge resistor (not shown). Thereby, the electrical storage part 33 can be completely discharged as needed. The third diode 43 is configured such that an anode is connected to the discharge circuit 41 side and a cathode is connected to the output terminal portion 27 side. Thereby, when the main power supply 15 is normal, the backflow in which the power supplied from the main power supply 15 to the load 17 is also supplied to the power storage unit 33 via the discharge circuit 41 is avoided.

  A power storage unit voltage detection circuit 45 is electrically connected to the power storage unit 33. As a result, the voltage Vc of the power storage unit 33 can be detected, so that the power storage unit 33 is charged by controlling the charging circuit 29 so that the voltage Vc reaches the charge completion voltage Vcs.

  Further, a booster circuit 47 is electrically connected to the power storage unit 33. The booster circuit 47 has a function of boosting and outputting the voltage Vc of the power storage unit 33. Specifically, as shown in FIG. 1, the resistor 49 includes a first transistor 51, a second transistor 53, a third transistor 55, a capacitor 57, and a fourth diode 59. As the step-up operation, the first transistor 51 performs an on / off operation in accordance with a pulse signal PLS input from a control circuit described later. Accordingly, the second transistor 53 and the third transistor 55 perform an on / off operation in which they are inverted from each other. Thereby, when the third transistor 55 is on, the power of the power storage unit 33 is charged to the capacitor 57 via the fourth diode 59. At this time, the voltage of the capacitor 57 is lower than the voltage Vc of the power storage unit 33 by a voltage drop (total of about 1.5 V) due to the fourth diode 59 and the third transistor 55. Thereafter, when the second transistor 53 is on, a voltage obtained by subtracting the voltage drop (about 0.75 V) due to the second transistor 53 from the sum of the voltages of the power storage unit 33 and the capacitor 57 is output as the output voltage Vout. By repeating such an operation, the voltage Vc of the power storage unit 33 input to the booster circuit 47 can be boosted and output as the output voltage Vout.

  The output of the booster circuit 47 is input to the selection circuit 61. Here, the selection circuit 61 has a function of outputting the higher one of the two input voltages. Specifically, the selection circuit 61 includes a first selection diode 63 and a second selection diode 65. The connection point becomes the output of the selection circuit 61. In the present embodiment, as shown in FIG. 1, the output of the booster circuit 47 is connected to the anode of the first selection diode 63. On the other hand, the anode of the second selection diode 65 is electrically connected to the connection point of the second diode 25 and the charging circuit 29. Therefore, the selection circuit 61 is configured to output the higher one of the output voltage Vout of the booster circuit 47 and the voltage Vb of the main power supply 15. Since the voltage Vb of the main power supply 15 is input to the second selection diode 65 via the second diode 25, the voltage drop caused by the second diode 25 from the voltage Vb of the main power supply 15 (precisely) The higher of the voltage obtained by subtracting about 0.75 V) and the output voltage Vout is output from the selection circuit 61.

The output of the selection circuit 61 is supplied as the drive voltage Vcc of the current detection circuit 31. Here, the output of the selection circuit 61 is connected to the operational amplifier 37 built in the current detection circuit 31. Therefore, the operational amplifier 37 is configured such that the higher one of the output voltage Vout of the booster circuit 47 and the voltage Vb of the main power supply 15 is applied as the drive voltage Vcc. Here, in the present embodiment, the operational amplifier 37 having a maximum allowable voltage of 32 V in the drive voltage Vcc is used.
A smoothing capacitor 67 is electrically connected to the output of the selection circuit 61. Thereby, the variation of the output voltage Vout based on the on / off operation of the booster circuit 47 is smoothed and applied to the operational amplifier 37.

  A control circuit 71 is electrically connected to a connection point between the second diode 25 and the charging circuit 29 via a regulator 69. As a result, the control circuit 71 is driven by the power of the main power supply 15. The control circuit 71 includes a microcomputer and peripheral circuits, and a regulator 69 generates an operating voltage Vecu that drives them. Here, the operating voltage Vecu was 5V.

  The control circuit 71 is also connected to the main power supply voltage detection circuit 21, the charging circuit 29, the current detection circuit 31, the discharge circuit 41, the power storage unit voltage detection circuit 45, and the booster circuit 47 through signal system wiring. Thereby, the control circuit 71 outputs the voltage Vb of the main power supply 15 from the main power supply voltage detection circuit 21, the current output I when charging the power storage unit 33 from the current detection circuit 31, and the power storage unit from the power storage unit voltage detection circuit 45. The voltage Vc of 33 is taken in, respectively. The control circuit 71 controls these circuits by outputting a charge control signal Ccont to the charge circuit 29, a discharge control signal Dcont to the discharge circuit 41, and a pulse signal PLS to the booster circuit 47, respectively. . Furthermore, the control circuit 71 is also electrically connected to a vehicle-side control circuit (not shown) through a data terminal unit 73 by signal system wiring. As a result, the control circuit 71 communicates various data with the vehicle-side control circuit using the data signal data.

  The ground of the control circuit 71 is electrically connected to the ground terminal portion 75 together with other grounds in the power storage device 11. Since the ground terminal portion 75 is connected to the ground of the vehicle, the ground in the power storage device 11 is electrically connected to the ground of the vehicle.

  Next, the operation of the power storage device 11 will be described. Since the power storage device 11 is a backup power supply for the voltage drop of the main power supply 15, in order to be able to back up whenever the voltage drop of the main power supply 15 occurs, the operation of charging the power storage unit 33 first when starting the vehicle I do. Details thereof will be described with reference to FIG. In FIG. 2, the horizontal axis indicates time t, and the vertical axis indicates voltage (unit: V).

  The driver turns on an ignition switch (not shown) of the vehicle at time t0 in FIG. At this time, since the engine has not yet been started, the voltage Vb of the main power supply 15 is 12V, which is the rated voltage, as shown by the short broken line in FIG. Further, since the power storage unit 33 is discharged after the use of the vehicle in order to ensure its life, the voltage Vc of the power storage unit 33 is 0 V as shown by a thin solid line in FIG. Further, the control circuit 71 is applied with the operating voltage Vecu by adjusting the voltage Vb of the main power supply 15 to 5 V by the regulator 69. Accordingly, the control circuit 71 starts operation at time t0. However, since the charging operation to the power storage unit 33 is not performed at this time, the output voltage Vout of the booster circuit 47 is 0 V as shown by the long broken line in FIG. Therefore, 0V is applied to the anode of the first selection diode 63 in the selection circuit 61, and the voltage drop (0.75V) of the second diode 25 from the voltage Vb of the main power supply 15 is applied to the anode of the second selection diode 65. 11.25V is applied after subtracting. Therefore, since the selection circuit 61 outputs the higher one of the two input voltages, the output of the selection circuit 61, that is, the drive voltage Vcc of the operational amplifier 37 is a voltage corresponding to the voltage Vb of the main power supply 15. Specifically, since the voltage drop of the second selection diode 65 occurs, 11.25V−0.75V = 10.5V becomes the drive voltage Vcc. Therefore, as shown by the thick solid line in FIG. 2, the driving voltage Vcc is 10.5 V at time t0.

  The reason why charging of the power storage unit 33 is not started at time t0 is as follows. When the driver turns on the starter (not shown) and starts the engine, a large current flows from the main power supply 15. If the power storage unit 33 is further charged in this state, an excessive burden is placed on the main power supply 15. Therefore, in order to reduce the burden on the main power supply 15, the power storage unit 33 is not charged before the engine is started.

  Next, the driver turns on the starter at time t1. As a result, as described above, a large current flows from the main power supply 15 to the starter, and the voltage Vb of the main power supply 15 greatly decreases as shown by the short broken line in FIG. Along with this, the drive voltage Vcc is also greatly reduced. However, since the power storage unit 33 is not charged at this time, the control circuit 71 does not need to detect the current output I of the current detection circuit 33. Therefore, even if the operation of the operational amplifier 37 becomes unstable due to a decrease in the drive voltage Vcc, the overall control of the power storage device 11 is not affected.

  Thereafter, the decrease width of the voltage Vb of the main power supply 15 becomes the maximum at time t2. Since the value of the voltage Vb at this time is about 6V, the voltage input to the regulator 69 is about 5.25V obtained by subtracting the voltage drop of the second diode 25. However, since the output voltage of the regulator 69 is 5V which is the drive voltage Vecu of the control circuit 71, it is lower than the voltage input to the regulator 69. Therefore, even if the voltage of the main power supply 15 is reduced due to the starter driving, the control circuit 71 continues to operate.

  When the decrease in the voltage Vb of the main power supply 15 is further increased and the voltage Vb becomes smaller than the drive voltage Vecu (= 5 V), the control circuit 71 is reset by a built-in voltage monitoring circuit (not shown). I try to do it. Also in this case, since the charging of the power storage unit 33 has not yet started, the overall control of the power storage device 11 is not affected.

  After the time t2, as the engine is started, the voltage Vb of the main power supply 15 increases as shown by the short broken line in FIG. The control circuit 71 detects this voltage change by the main power supply voltage detection circuit 21. Thereafter, when the voltage Vb of the main power supply 15 becomes equal to or higher than the predetermined voltage Vbr at time t3, charging of the power storage unit 33 is started. Here, the predetermined voltage Vbr is determined as follows.

  As described above, at time t2, the voltage Vb of the main power supply 15 decreases to about 6V. Since the voltage input to the regulator 69 at this time is about 5.25 V, it is slightly higher than the drive voltage Vecu of the control circuit 71. In this case, although the operation of the control circuit 71 can be continued, the control circuit 71 may be reset if the voltage Vb decreases even slightly. If charging of the power storage unit 33 is started in such an unstable state, the charging may be interrupted when the control circuit 71 is reset. Therefore, in the present embodiment, a power storage unit is added until 8 V higher than the lowest voltage (= 6 V) of the main power supply 15 is applied to the operational amplifier 37 as the drive voltage Vcc, with a margin added in order to perform stable charging. The charging of 33 is not started. Here, when the voltage of the main power supply 15 for setting the drive voltage Vcc to 8 V, that is, the predetermined voltage Vbr is obtained, the second diode 25 and the second diode 25 are connected to the power system wiring path from the main power supply 15 to the operational amplifier 37. Since the two-select diode 65 is arranged, the voltage of the main power supply 15 must be high by the total voltage drop (= 1.5 V) due to these. Therefore, the predetermined voltage Vbr is determined as 8V + 1.5V = 9.5V.

  In the present embodiment, the operating voltage Vecu (= 5 V) of the control circuit 71 is set to be lower than the predetermined voltage Vbr (= 9.5 V). Thus, since control circuit 71 can operate before charging of power storage unit 33, operation of charging circuit 29 and booster circuit 47 can be controlled without delay at time t3.

  As described above, since the current detection circuit 31 operates normally at time t3, charging of the power storage unit 33 is started. The specific charging operation is as follows. At time t3, since the voltage Vc of the power storage unit 33 is 0 V, the control circuit 71 controls the charging circuit 29 so that the current output I of the current detection circuit 31 becomes the predetermined current Ir. The predetermined current Ir may be appropriately determined according to a period necessary for fully charging the power storage unit 33, a capacity value of the power storage unit 33, and the like. In the present embodiment, the predetermined current Ir is determined to be 5 A so that the full charge is completed in about 2 minutes. By controlling in this way, the power storage unit 33 is charged with the predetermined current Ir, and the voltage Vc of the power storage unit 33 increases with time as shown by a thin solid line in FIG. 2 after time t3. As charging control by the charging circuit 29, charging is basically performed by the above-described predetermined current Ir, but in order to reduce the possibility that the power storage unit 33 is overcharged beyond the charging completion voltage Vcs, the control circuit 71 also monitors the voltage Vc of the power storage unit 33 detected by the power storage unit voltage detection circuit 45. As a result, the constant voltage control is performed when the charging approaches completion so that the voltage Vc of the power storage unit 33 reaches the charging completion voltage Vcs. Therefore, when these controls are summarized, the control circuit 71 completes charging so that the current output I of the current detection circuit 31 becomes the predetermined current Ir and the voltage Vc of the power storage unit 33 detected by the power storage unit voltage detection circuit 45 is charged. The charging circuit 29 is controlled to reach the voltage Vcs, and the power storage unit 33 is charged.

  At time t3, the control circuit 71 outputs a pulse signal PLS to operate the booster circuit 47. Accordingly, charging of the power storage unit 33 is started after time t3, and when the voltage Vc increases with time, the output voltage Vout of the booster circuit 47 also increases with time. In the vicinity of time t3, the voltage Vc of power storage unit 33 is low, so that a sufficient boost ratio cannot be achieved. Therefore, as shown by the long broken line in FIG. 2, the output voltage Vout has a period lower than the voltage Vc of the power storage unit 33. Thereafter, as the voltage Vc of the power storage unit 33 increases, the output of the booster circuit 47 The voltage Vout is higher. In the vicinity of time t3, as shown in FIG. 2, the voltage Vb of the main power supply 15 is sufficiently higher than the output voltage Vout, so that the power output from the selection circuit 61 is supplied from the main power supply 15.

  Thereafter, the engine start is completed at time t4. At this time, since the generator also starts power generation by the engine, the voltage Vb of the main power supply 15 is stabilized at 14 V, which is the output voltage of the generator, as shown by the short broken line in FIG. Even at this time, the voltage Vb is sufficiently higher than the output voltage Vout of the booster circuit 47, so that the power output from the selection circuit 61 is continuously supplied from the main power supply 15.

  After time t4, as the power storage unit 33 is charged, the voltage Vc of the power storage unit 33 and the output voltage Vout of the booster circuit 47 rise over time, and eventually the main power supply 15 input to the selection circuit 61 at time t5. The voltage corresponding to the voltage Vb is equal to the output voltage Vout of the booster circuit 47. That is, at the time t5, the anode voltage of the second selection diode 65 is 13.25 V, which is lower than the voltage Vb of the main power supply 15 by the voltage drop of the second diode 25, while the output voltage Vout of the booster circuit 47 is also 13. 25V. Thereafter, since the output voltage Vout increases with time, the second selection diode 65 is turned off, the first selection diode 63 is turned on, and the power output from the selection circuit 61 is supplied from the booster circuit 47. Become. As a result, the drive voltage Vcc rises as a voltage lower than the output voltage Vout of the booster circuit 47 by the voltage drop of the first selection diode 63, as shown by the thick solid line in FIG.

  Thereafter, when voltage Vc of power storage unit 33 reaches charging completion voltage Vcs (= 13 V) at time t6, control circuit 71 controls charging circuit 29 so that voltage Vc of power storage unit 33 maintains charging completion voltage Vcs. . As a result, the voltage Vc of the power storage unit 33 is always substantially equal to the charge completion voltage Vcs after time t6, so that power can be sufficiently backed up for the load 17 even when the voltage Vb of the main power supply 15 is reduced. Since the voltage Vc of the power storage unit 33 becomes constant, the output voltage Vout of the booster circuit 47 becomes constant (23.75V), and the drive voltage Vcc of the current detection circuit 31 is stabilized at 23V.

  Here, the reason why the output voltage Vout of the booster circuit 47 becomes 23.75 V after time t6 is as follows. Since the charge completion voltage Vcs of the power storage unit 33 is 13V, the capacitor 57 of the booster circuit 47 has a voltage drop (1.5V) of the fourth diode 59 and the third transistor 55 from the charge completion voltage Vcs (13V), A low voltage, i.e. 11.5V, is applied. Therefore, when this is discharged, 23.75 V obtained by subtracting the voltage drop of the second transistor 53 from 24.5 V, which is the sum of the voltage Vc of the power storage unit 33 and the voltage applied to the capacitor 57, is the output of the booster circuit 47. The voltage becomes Vout. As a result, the drive voltage Vcc of the current detection circuit 31 that is the output of the selection circuit 61 becomes 23 V obtained by subtracting the voltage drop of the first selection diode 63 from the output voltage Vout (23.75 V).

  From the above description, as shown in FIG. 2, the drive voltage Vcc of the current detection circuit 31 is always higher than the voltage Vc of the power storage unit 33 after time t3. Therefore, even if the voltage Vc of the power storage unit 33 increases, the possibility of approaching the drive voltage Vcc is reduced, and the current detection circuit 31 can detect the current with high accuracy.

  Note that the booster circuit 47 continues to operate even after charging of the power storage unit 33 is completed (after time t6). As a result, a sufficient drive voltage Vcc is always applied to the current detection circuit 31. Therefore, even when the power storage unit 33 is recharged after power is backed up to the load 17 by the power storage device 11, the erroneous detection is reduced. Accurate current detection is possible.

  Next, the operation of power storage device 11 during normal vehicle use after time t6 will be described.

  The control circuit 71 constantly monitors the voltage Vb of the main power supply 15 by the main power supply voltage detection circuit 21. If the voltage Vb falls below the minimum drive voltage of the load 17 (10.5 V as described above) due to an abnormality in the main power supply 15 and its peripheral circuits or the load 17 consuming a large current, the control circuit 71 Immediately stops charging the power storage unit 33 and supplies the power of the power storage unit 33 to the load 17 by the discharge circuit 41 for backup. Thereby, even if the voltage Vb of the main power supply 15 falls, the load 17 can be continuously driven. At this time, the power of the power storage unit 33 does not flow to the main power supply 15 due to the first diode 23 and the second diode 25.

Thereafter, when the voltage Vb of the main power supply 15 returns to a normal range, the control circuit 71 controls the discharge circuit 41 to stop the discharge from the power storage unit 33 to the load 17. Thereafter, in order to prepare for the next drop in voltage Vb, power storage unit 33 is recharged. This operation is the same as that after time t3 in FIG.
By repeating such an operation, the load 17 can be backed up even if the voltage Vb of the main power supply 15 decreases.

  The control circuit 71 controls to stop the charging circuit 29 and then stop the booster circuit 47 when stopping the charging of the power storage unit 33. By controlling in this way, the booster circuit 47 is always operating while the charging circuit 29 is operating. Therefore, the current detection circuit 31 can also output a current value without erroneous detection. From this, it is possible to reduce the possibility of controlling charging with a current value erroneously detected by stopping the booster circuit 47 first.

  Next, the operation after the use of the vehicle will be described. When the driver turns off the ignition switch, the information is transmitted from the vehicle side control circuit to the control circuit 71 by the data signal data. In response to this, the control circuit 71 performs an operation of stopping the charging of the power storage unit 33 described above. Thereafter, the control circuit 71 completely discharges the power storage unit 33 by the discharge resistor built in the discharge circuit 41. Thereby, the voltage application of the electrical storage part 33 at the time of vehicle non-use is avoided, and lifetime improvement can be achieved. In addition, the discharge period by the discharge circuit 41 is obtained in advance in a memory built in the control circuit 71 by obtaining a period until the power storage unit 33 is completely discharged from the fully charged state. Therefore, when the discharge period has elapsed, the control circuit 71 stops discharging the power storage unit 33 by the discharge circuit 41 and ends the operation of the power storage device 11.

  With the above configuration and operation, the power storage device 11 capable of reducing the error of the current output I caused by the drive voltage Vcc of the current detection circuit 31 approaching the voltage Vc of the power storage unit 33 and capable of highly accurate charge control is realized. it can.

  Note that a DC / DC converter may be used as the booster circuit 47 in the present embodiment. In this case, the driving voltage Vcc of the operational amplifier 37 is a voltage obtained by adding a voltage drop (1.5 V as described above) due to the internal circuit of the operational amplifier 37 to the charging completion voltage Vcs (= 13 V) of the power storage unit 33. (= 14.5V) and lower than the maximum allowable voltage (32V) of the operational amplifier 37, it is necessary to set the output voltage of the DC / DC converter to a voltage from 14.5V to 32V. is there. However, since the current for driving the operational amplifier 37 is about several milliamperes, when a DC / DC converter is used for the booster circuit 47, the loss becomes larger. Therefore, the configuration of the booster circuit 47 of the present embodiment is desirable.

  Further, in the present embodiment, the power storage unit 33 is completely discharged by the discharge circuit 41 after the use of the vehicle is finished. This is because the voltage Vc of the power storage unit 33 is higher than the voltage Vb of the main power supply 15. A dark current may be supplied. Thereby, the waste of the electric power of the electrical storage part 33 can be reduced. However, in the present embodiment, as shown in FIG. 2, the charging completion voltage Vcs of the power storage unit 33 is 13V, and the voltage Vb of the main power supply 15 when the ignition switch is off is 12V. ) Can only supply dark current to the load 17. Therefore, since the amount of electric power that can be supplied is small, the electric power of the power storage unit 33 is completely discharged by the discharge circuit 41 after the ignition switch is turned off so that the control is facilitated in the present embodiment.

  In the present embodiment, the electric double layer capacitor is used as the electric storage element in the electric storage unit 33. However, this may be another capacitor such as an electrochemical capacitor or a secondary battery.

  In the present embodiment, the case where the power storage device 11 is applied to a backup auxiliary power source for a vehicle has been described. However, the present invention is not limited to this, and the power storage device 11 can also be applied to a power regeneration or emergency auxiliary power source.

  Since the power storage device according to the present invention enables highly accurate charge control, it is particularly useful as a power storage device or the like as an auxiliary power source that supplies power from the power storage unit when the voltage of the main power source drops.

1 is a block circuit diagram of a power storage device in an embodiment of the present invention. Time-dependent characteristic chart of various voltages during charging of the power storage device according to the embodiment of the present invention Block diagram of a conventional power storage device

11 power storage device 15 main power supply 17 load 21 main power supply voltage detection circuit 29 charging circuit 31 current detection circuit 33 power storage unit 35 shunt resistor 37 operational amplifier 45 power storage unit voltage detection circuit 47 booster circuit 61 selection circuit 71 control circuit

Claims (4)

A power storage device electrically connected between a main power source and a load,
The power storage device includes a power storage unit that stores power of the main power source,
A charging circuit electrically connected between the main power source and the power storage unit, and a series circuit including a current detection circuit;
A main power supply voltage detection circuit electrically connected to the main power supply;
A booster circuit electrically connected to the power storage unit, and a power storage unit voltage detection circuit;
A selection circuit for outputting the higher one of the output voltage (Vout) of the booster circuit and the voltage (Vb) of the main power supply as the drive voltage (Vcc) of the current detection circuit;
A control circuit connected to the charging circuit, a current detection circuit, a booster circuit, a main power supply voltage detection circuit, and a storage unit voltage detection circuit;
The current detection circuit includes a shunt resistor,
An operational amplifier having input terminals connected to both ends of the shunt resistor; and
The output of the selection circuit has a configuration connected to the operational amplifier,
The control circuit operates the booster circuit when the main power supply voltage (Vb) detected by the main power supply voltage detection circuit is equal to or higher than a predetermined voltage (Vbr) when charging the power storage unit.
The current output (I) of the current detection circuit becomes a predetermined current (Ir), and the voltage (Vc) of the power storage unit detected by the power storage unit voltage detection circuit reaches a charge completion voltage (Vcs). A power storage device that controls the charging circuit. The power storage device according to claim 1, wherein the booster circuit continues to operate even after charging of the power storage unit is completed. The power storage device according to claim 1, wherein an operating voltage (Vecu) of the control circuit is lower than the predetermined voltage (Vbr). 2. The power storage device according to claim 1, wherein when the charging to the power storage unit is stopped, the control circuit first stops the charging circuit and then stops the booster circuit. 3.

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