JP2012257355A - Power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply device that can suppress variation of an output voltage even when a secondary battery has large voltage drop due to self discharge.SOLUTION: A power supply device has a secondary battery 8, a first switch 9, a charging circuit 10, a DCDC converter 11 and an output terminal 12 which are successively connected to the positive potential output side of the secondary battery 8 in series, a capacitor 14 having a positive potential terminal connected between the charging circuit 10 and the DCDC converter 11 and a negative potential terminal connected to the ground, a capacitor voltage detecting circuit 15 connected between the positive potential terminal of the capacitor 14 and the positive potential output side of the secondary battery 8, and a second switch 16 which is connected between the input side of the charging circuit 10 and the positive potential output side of the secondary battery 8 and controlled on the basis of a signal from the capacitor voltage detecting circuit 15. The power supply device is provided with a normal startup mode, an extraordinary startup mode and a standing mode.

Description

  The present invention relates to a power supply device used for auxiliary power supply when various vehicles are started.

  Hereinafter, a conventional power supply device will be described with reference to the drawings. FIG. 4 is a block diagram showing a configuration of a conventional power supply apparatus. In this power supply device, when a predetermined voltage is applied from the storage battery 1 to the load 2, the voltage of the storage battery 1 is detected in advance by the voltage detector 4 with the load side switch 3 being disconnected, and the voltage is applied to the load 2. When the load 2 is an appropriate value for operating, the load side switch 3 is connected.

  Further, if the voltage 2 is insufficient and low for the load 2 to operate when the voltage is applied to the load 2, an instruction is issued from the voltage detector 4 to the DCDC converter 5 and the converter side switch 6. The voltage due to the electric charge stored in the capacitor 7 is changed to an arbitrary superposition voltage by the DCDC converter 5 and the converter side switch 6 is connected. The voltage applied to the load 2 is set to an appropriate value after the superposition of the load side switch 3. It was to be connected.

  For example, Patent Document 1 is known as prior art document information relating to the invention of this application.

JP 2003-158831 A

  In the conventional power supply device, when the storage battery terminal voltage drops due to the storage battery 1 being left for a long period of time, particularly when the voltage drop is a large value, only the absolute value of the voltage drop is required. In consideration of the fact that the fluctuation range of the voltage drop also varies greatly from time to time, it is necessary to change the constant of the capacitor 7 and the setting of the boosting width of the DCDC converter 5 to correspond to the fall range. However, this is very difficult to control, and as a result, it is also difficult to set the voltage applied to the load 2 to an appropriate value.

  Therefore, the present invention provides a power supply device that can supply a stable voltage even when a storage battery undergoes a large voltage drop due to self-discharge.

  In order to achieve this object, the power storage device of the present invention includes a storage battery, a first switch, a charging circuit, a DCDC converter, an output terminal, and the charging circuit that are serially connected in series to the positive potential output side of the storage battery. And a capacitor having a positive potential terminal connected between the DCDC converter and a negative potential terminal connected to the ground, and a voltage detection connected between the positive potential terminal of the capacitor and the positive potential output side of the storage battery And a second switch connected between the input side of the charging circuit and the positive potential output side of the storage battery and controlled by a signal from the voltage detection circuit, and the output voltage of the storage battery is stored in the storage battery When the voltage output to the output terminal is requested when the value is greater than or equal to the threshold value, the first switch is connected and the second switch is opened. A normal start mode in which the DCDC converter is short-circuited while charging a capacitor, and the first switch when a voltage output to the output terminal is requested when the output voltage of the storage battery is less than or equal to the storage battery threshold. In the emergency start mode in which the potential of the capacitor is boosted by the DCDC converter, and at any time other than the normal start mode and the emergency start mode, the potential of the positive potential terminal of the capacitor is equal to or lower than the capacitor first threshold value. When the voltage detection circuit detects that the second switch is short-circuited, a stand-by mode is provided in which the capacitor is charged until the potential at the positive potential terminal of the capacitor becomes equal to or higher than the capacitor second threshold. It is a feature.

  According to the present invention, even when the storage battery undergoes a large voltage drop due to self-discharge or the like, it is possible to supply a voltage necessary for starting the vehicle from the power supply device, and when the storage battery is not charged over a long period of time. Can start the vehicle stably.

The block diagram of the power supply device in one Embodiment of this invention FIG. 3 is a relationship diagram of time and voltage during operation of the power supply device according to the embodiment of the present invention. The block diagram of the DCDC converter part in the power supply device in one Embodiment of this invention Block diagram of a conventional power supply

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment)
FIG. 1 is a circuit block diagram showing the configuration of the power supply device of the present invention. Here, the storage battery 8 and a series connection circuit including a first switch 9, a charging circuit 10, a DCDC converter 11, and an output terminal 12 are sequentially connected to the positive potential output side of the storage battery 8 and output to the load 13. A voltage is applied. A capacitor 14 is connected between the charging circuit 10 and the DCDC converter 11, the positive potential terminal side of the capacitor 14 is connected between the charging circuit 10 and the DCDC converter 11, and the negative potential terminal side is grounded. ing. A capacitor voltage detection circuit 15 is provided between the positive potential terminal side of the capacitor 14 and the positive potential output side of the storage battery 8, and a second voltage is provided between the input side of the charging circuit 10 and the positive potential output side of the storage battery 8. Each of the switches 16 is connected, and the connection and release of the second switch 16 are controlled by a signal from the capacitor voltage detection circuit 15.

  And said circuit structure will operate | move by the following individual function modes.

  First, the normal activation mode in which the output voltage of the storage battery 8 is equal to or higher than the storage battery threshold will be described. Here, in the normal start mode, when a signal instructing start-up is input to the power supply start instruction terminal 17, the storage battery voltage detection circuit 18 operates simultaneously with this, and the voltage of the storage battery 8 is changed to the storage battery by the storage battery voltage detection circuit 18. The operation in a state where it is detected that the value is equal to or greater than the threshold value is shown. The storage battery threshold value is a value at which the output voltage at which the load 13 operates can be taken out from the output terminal 12 when the storage battery 8 has the voltage, and this threshold value is arbitrarily set according to the characteristics of the load. That's fine.

  And when it detects that the voltage of the storage battery 8 is more than a storage battery threshold value, the 1st switch 9 which was an open state until the start was instruct | indicated was made into a connection state, and this voltage was provided in the inside of the charging circuit 10 The voltage is dropped by a voltage dividing circuit (not shown), and the voltage after the drop is input to the DCDC converter 11. At this time, the DCDC converter 11 is controlled by a control signal from the storage battery voltage detection circuit 18 so as to be in a short circuit state having no voltage conversion function, and the voltage from the charging circuit 10 is directly output to the load 13 as the output voltage of the output terminal 12. Will be applied. Here, at the same time, the capacitor 14 is charged by the voltage from the charging circuit 10 as charge accumulation.

  The capacitor voltage detection circuit 15 controls the second switch 16 to be in an open state by detecting that the capacitor 14 is in a charged state or detecting that the voltage of the storage battery 8 is equal to or higher than the storage battery threshold. is doing. Furthermore, the first switch 9 and the second switch 16 are not short-circuited at the same time, and the second switch 16 is always open in the normal startup mode.

  Here, in the charging circuit 10, for example, when the standard value voltage of the storage battery 8 is 12 (V), the voltage is dropped so that the voltage on the output side of the charging circuit 10 becomes 5 (V). ) Is applied from the output terminal 12 to the load 13. Further, the constant of the capacitor 14 may be determined so that the charging voltage to the capacitor 14 becomes an upper limit value that is lower than the voltage on the output side of the charging circuit 10 described above. The constant or charging voltage of the capacitor 14 here may be determined according to the degree of boosting during the operation of the DCDC converter 11 to which the charging voltage of the capacitor 14 is applied and the stable operation range of the DCDC converter 11.

  Next, an emergency start mode that is used when the output voltage of the storage battery 8 is equal to or lower than the storage battery threshold will be described. Here, in the emergency start mode, when a signal instructing start-up is input to the power supply start instruction terminal 17, the storage battery voltage detection circuit 18 operates simultaneously with this, and the voltage of the storage battery 8 is changed by the storage battery voltage detection circuit 18 to the storage battery. The operation in a state where it is detected that the value is equal to or less than the threshold is shown. The storage battery threshold is the same as described above.

  When it is detected that the voltage of the storage battery 8 is equal to or less than the storage battery threshold value, the first switch 9 that has been in the open state until the activation is instructed continues to be in the open state and the DCDC converter 11 is in the operating state. It is controlled by a control signal from the storage battery voltage detection circuit 18, and the charging voltage in the capacitor 14 is boosted by the DCDC converter 11, so that an output voltage that enables the load 13 to operate is supplied to the output terminal 12. That is, the storage battery 8 and the load 13 are in a disconnected state, and direct power supply from the storage battery 8 to the load 13 is not performed. Even in the emergency start mode, the second switch 16 is always open.

  Here, the pre-charging of the capacitor 14 corresponding to the voltage to be boosted by the DCDC converter 11 is a charge accumulation performed in parallel with the supply of power to the load 13 in the normal startup mode described above. Either the case of applying or the case of applying charge accumulation performed in the neglected mode described below is applied.

  However, in practice, the period in which the charge accumulation performed in parallel with the supply of power to the load 13 in the normal startup mode is applied as it is. This is only when there is sufficient charge left when the power supply device was operating normally before performing the emergency start mode operation, and the capacitor voltage detection circuit detects the voltage of the capacitor 14. This is the period until the voltage shortage is detected by the detecting operation. On the other hand, the period during which charge accumulation performed in the neglected mode described below is applied is much longer than the above period.

  Here, the neglected mode, which is a state other than the normal startup mode and the emergency startup mode described above, will be described. Here, the neglected mode refers to a mode in which the power activation instruction terminal 17 is left without any signal instructing activation. In particular, it is an important function that the storage battery 8 precharges the capacitor 14 when the first switch 9 is opened at that time and the second switch 16 is connected according to the timing. It has become.

  In this state, the capacitor voltage detection circuit 15 detects the voltage of the storage battery 8 and the potential of the positive potential terminal of the capacitor 14 continuously or at regular intervals. Therefore, when it is detected that the potential of the positive potential terminal of the capacitor 14 is equal to or lower than the capacitor first threshold value, the capacitor 14 is charged by switching the second switch 16 that was initially open to a short-circuited state. Circuit connection is used. For the capacitor 14, the second potential is detected until the capacitor voltage detection circuit 15 detects that the potential of the positive potential terminal becomes a capacitor second threshold value that is higher than the capacitor first threshold value. The switch 16 is short-circuited to continue charging the capacitor 14. In practice, this charging is performed instantaneously. Therefore, there is no problem even if the power required for the detection operation is suppressed by setting the charging time without detecting the capacitor second threshold value. In this operation, when the voltage of the storage battery 8 holds a value higher than the capacitor second threshold value, it is naturally possible to charge the capacitor 14 until it reaches the capacitor second threshold value.

  Here, as described above, the capacitor first threshold value may be set to a value higher than the lower limit value at which the operation for the constant voltage output in the DCDC converter 11 to which the charging voltage of the capacitor 14 is applied is possible. The capacitor second threshold value may be a value that is higher than the capacitor first threshold value, equal to or less than the rated voltage value of the capacitor 14, and capable of a constant voltage output operation in the DCDC converter 11. Alternatively, when the charging of the capacitor 14 cannot reach the capacitor second threshold value, that is, when the voltage of the storage battery 8 is lowered to the capacitor second threshold value or less, the charging voltage value of the capacitor 14 is the storage battery 8 at that time. It may be a chargeable upper limit value that is equivalent to the above voltage. Even if it is detected that the potential of the positive potential terminal of the capacitor 14 is equal to or lower than the capacitor first threshold value, it is detected that the voltage of the storage battery 8 is lower than the potential of the positive potential terminal of the capacitor 14. The second switch 16 is opened and the storage battery 8 and the capacitor 14 are not connected.

  Here, the criterion for determining the necessity of charging for the voltage of the capacitor 14 has been described here by setting two values of the capacitor first threshold value and the capacitor second threshold value, but this value is a single value. As described below, the capacitor voltage detection circuit 15 may determine whether the value is equal to or less than this value. However, as described below, the voltage of the capacitor 14 is detected at regular intervals. It is desirable that the two values be different in order to reduce power consumption and thereby make the characteristics of the neglected mode effective. And about these determinations, what is necessary is just to determine the space | interval of two values according to the self-discharge characteristic of the storage battery 8. FIG. Then, the charge stored in the capacitor 14 in this neglected mode can be applied as electric power in the emergency start mode.

  In addition, the operation of the capacitor voltage detection circuit 15 in the neglected mode is desirably performed periodically with a certain time interval, rather than continuously performing the detection operation. Although this is weak, since the operation of the capacitor voltage detection circuit 15 and the operation of the second switch 16 can be performed by receiving power supply from the storage battery 8, the viewpoint of extending the life of the storage battery 8 is achieved. But it is better to do it at regular intervals. Here, for convenience of explanation, although the capacitor voltage detection circuit 15 and the storage battery voltage detection circuit 18 are shown as separate detection circuits, they may be configured by a single detection circuit, but the storage battery voltage detection circuit 18 Since it is a part connected to the accessory switch in the vehicle which is the power activation instruction terminal 17, it is desirable to have an independent function with a function for dealing with noise resistance and inrush signals. Similarly, it is desirable that the capacitor voltage detection circuit 15 has a characteristic that can cope with a small electric power compared with the storage battery voltage detection circuit 18 and can cope with a voltage fluctuation of the capacitor 14 with high sensitivity.

  Also, it is desirable that the first switch 9 and the second switch 16 are not used as a single switch element but are used separately. Here, the first switch 9 is connected (operated) when the storage battery 8 is in a state equal to or higher than a storage battery threshold that can be normally operated, and thereafter, a generator (not shown) that supplies power to the storage battery 8 is used. Since the connection is continuously performed in the state of continuous operation of the operating power supply device, the power consumption may be larger than that of the second switch 16 as long as it can handle a large current. Absent. Since the second switch 16 is connected to the capacitor 14 having a limited time and capacity when the storage battery 8 is below the storage battery threshold value, the power consumption is small and the second switch 16 can be operated in a short time. It may be of any current and power capacity possible.

  In this discharge mode, the capacitor 14 is charged by the limited electric power from the storage battery 8, so that the voltage dividing circuit (not shown) is not connected in the charging circuit 10, and the voltage dividing circuit is not connected. Corresponding parts (not shown) are short-circuited to reduce the power loss as much as possible.

  With the above configuration, each of the normal startup mode and the emergency startup mode does not obtain a necessary voltage by superimposing a plurality of voltages, but receives supply of energy from different power storage elements corresponding to each mode. The voltage is output. As a result, the voltage supply source in each mode is independent, and in the normal startup mode, the voltage dividing ratio is set in an appropriate voltage dividing circuit (not shown) in the charging circuit 10, or in the emergency startup mode, the capacitor is set. By making the fluctuation range of the charging voltage 14 within an allowable range for the constant pressure output in the DCDC converter 11, it becomes possible to obtain the output voltage value with high accuracy and an easy circuit configuration in any case. Is.

  Further, since the capacitor 14 can be in a state in which sufficient charge for operating the DCDC converter 11 and supplying a desired voltage to the output terminal 12 is accumulated for a long period of time compared to the storage battery 8, Compared to the startup mode, the emergency startup mode can be handled after being left for a long time.

  In general, when the above-described normal startup mode operation is not performed, which corresponds to a state in which the power supply device is left unattended for a long period of time, the storage battery 8 undergoes self-discharge, so that the storage battery voltage curve shown in FIG. In addition, the voltage gradually decreases. As this state continues, at any time, the storage battery threshold, which is the lower limit of the voltage to be supplied to the load 13 shown in FIG. 1, falls below the point shown in FIG. 2 (point A in the figure). However, even if the voltage of the storage battery 8 shown in FIG. 1 falls below the storage battery threshold, the capacitor 14 stores a charging voltage that can supply a voltage sufficient to operate the load 13 by boosting the voltage by the DCDC converter 11. Will be.

  2, when the storage battery voltage is equal to or lower than the capacitor second threshold value as described above, the capacitor voltage value may be a chargeable upper limit value corresponding to the storage battery voltage at that time (B in the figure). point). The charging operation is not performed after the time when the storage battery voltage falls below the capacitor first threshold (point C in the figure). These are controlled by operating the capacitor voltage detection circuit 15 and the storage battery voltage detection circuit 18 shown in FIG.

  That is, even after the self-discharge of the storage battery 8, the power supply device can be activated by the energy stored in the capacitor 14 as long as the voltage is at least the operation lower limit value of the DCDC converter 11. In addition to this, after the self-discharge of the storage battery 8, the capacitor 14 accumulates in the capacitor 14 for a longer period by the charging operation of the capacitor 14 accompanying the detection operation of the capacitor voltage detection circuit 15 with respect to the voltage of the capacitor 14 at regular intervals. The power supply device can be activated with the energy that is generated in response to an activation instruction signal corresponding to an accessory switch in the vehicle. When a voltage is applied to the load 13 by the activation instruction signal, the electric power supplied there is, for example, about 5 (V), 200 (mA), and the time is short, so the capacitor 14 is used as a charging element. It is desirable to apply an electric double layer capacitor that hardly causes self-discharge with a withstand voltage of 2 to 3 (V) and a capacity of 30 to 40 (F).

  This will be described with reference to FIG. 2. The period in which the storage battery voltage is higher than the storage battery threshold (VB) is a period in which the normal activation mode can be used, and the storage battery voltage is lower than the storage battery threshold (VB). A period from T1 to T4 when the capacitor voltage becomes lower than the DCDC converter operation lower limit (VD) is a period in which the emergency start mode can be used. A series of operations and periods in which the potential drop due to the self-discharge of the capacitor in T1 to T2 is stored by charging from the storage battery voltage corresponds to the operation in the neglected mode. Further, a period in which the capacitor voltage after T2 becomes higher than the storage battery voltage is also a period in which the determination is performed under the neglected mode. Although the curve is shown here as being simplified, in particular, when the interval between the capacitor first threshold value and the capacitor second threshold value is small, in actuality, the capacitor voltage is periodically applied several times during the period from T1 to T2. Is very likely to be repeatedly charged and discharged. As for the interval between the capacitor first threshold value and the capacitor second threshold value, when the stable operation range of the DCDC converter 11 shown in FIG. 1 is wide, the interval between the capacitor first threshold value and the capacitor second threshold value shown in FIG. At the same time, the detection operation period with respect to the capacitor voltage can be set longer, and the power can be further reduced.

  As described above, by providing the neglected mode, it is possible to extend the correspondence period of the emergency start mode from T1 to T4 to T1 to T4.

  In order to maintain this function, the slope of the self-discharge curve of the capacitor 14 shown in FIG. 1 is made smaller than the slope of the self-discharge curve of the storage battery 8, that is, the capacitor 14 has a higher degree of progress of self-discharge. Needless to say, it is necessary to make it slower than the storage battery 8. Strictly speaking, as shown in FIG. 2, the slope of the self-discharge of the capacitor from the capacitor second threshold value to the capacitor first threshold value is smaller than the slope of the self-discharge in the storage battery after it has decreased to the capacitor second threshold value. is necessary.

  Although the activation of the power supply device is described here, the generator (not shown) and the like are naturally also activated by the activation of the entire power supply device shown in FIG. 1 and the activation of the entire vehicle system. As a result, the storage battery 8 whose voltage has been lowered is charged to the original reference voltage, and the entire power supply apparatus is shifted to the initial state. And the capacitor 14 should just have the capacity | capacitance which stores instantaneous electric power for shifting to the state which starts said generator (not shown) by supplying electric power via the DCDC converter 11. FIG.

  Further, as described above, the emergency start mode is a state in which the voltage of the storage battery 8 is lowered, that is, the start-up is in a state where the power is insufficient, and therefore, when starting the DCDC converter 11 as shown in FIG. In addition, for example, low voltage start-up and low power start of about 0.4 (V) are required. Here, a voltage for operating the control unit 19 that controls the operation of the DCDC converter 11 is obtained from outside the DCDC converter 11 and is once input to the booster circuit unit 20. Is the operating voltage for the control unit 19. Thereby, the burden on the storage battery 8 shown in FIG. 1 can be suppressed, and even if the voltage after the self-discharge of the storage battery 8 is reduced, the DCDC converter 11 can be operated by the voltage.

  The power supply device of the present invention has an effect of enabling stable start-up in a vehicle power supply and is useful in various vehicles.

DESCRIPTION OF SYMBOLS 8 Storage battery 9 1st switch 10 Charging circuit 11 DCDC converter 12 Output terminal 13 Load 14 Capacitor 15 Capacitor voltage detection circuit 16 2nd switch 17 Power supply starting instruction terminal 18 Storage battery voltage detection circuit

Claims (6)

A storage battery,
A first switch, a charging circuit, a DCDC converter, and an output terminal connected in series to the positive potential output side of the storage battery;
A capacitor having a positive potential terminal connected between the charging circuit and the DCDC converter and a negative potential terminal grounded;
A voltage detection circuit connected between the positive potential terminal of the capacitor and the positive potential output side of the storage battery;
A second switch connected between an input side of the charging circuit and a positive potential output side of the storage battery and controlled by a signal from the voltage detection circuit;
When the voltage output to the output terminal is requested when the output voltage of the storage battery is equal to or higher than the storage battery threshold, the first switch is connected and the second switch is opened. A normal startup mode in which the DCDC converter is short-circuited while charging a capacitor;
When the voltage output to the output terminal is requested when the output voltage of the storage battery is less than or equal to the storage battery threshold, the first switch is opened and the potential of the capacitor is boosted by the DCDC converter Start mode and
When the voltage detection circuit detects that the potential of the positive potential terminal of the capacitor is equal to or lower than the capacitor first threshold at all times other than the normal activation mode and the emergency activation mode, the second switch is short-circuited. A power supply device provided with a leaving mode in which charging is performed until a potential of a positive potential terminal of the capacitor becomes equal to or higher than the first threshold value of the capacitor. The power supply apparatus according to claim 1, wherein the capacitor voltage is detected by the voltage detection circuit in a periodic intermittent operation. In the neglected mode, when the voltage detection circuit detects that the potential of the positive potential terminal of the capacitor is equal to or lower than the first threshold value of the capacitor, the second switch is short-circuited and the potential of the positive potential terminal of the capacitor is changed to the first capacitor potential. The power supply device according to claim 1, wherein charging is performed until the capacitor becomes equal to or greater than a second threshold value set as a threshold value. In the neglected mode, when the voltage detection circuit detects that the potential of the positive potential terminal of the capacitor is equal to or lower than the first threshold value of the capacitor, the second switch is short-circuited and the potential of the positive potential terminal of the capacitor is set to the capacitor. The power supply device according to claim 1, wherein the power supply device is charged until it is equal to or higher than a first threshold value or reaches an output potential of the storage battery. The power supply device according to claim 1, wherein the second switch consumes less power than the first switch. The power supply apparatus according to claim 1, wherein the DCDC converter control unit that controls the DCDC converter is supplied with power from a booster circuit unit that boosts a voltage obtained from the outside of the DCDC converter.

Images