JP2018085810A - Auxiliary power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an auxiliary power supply device which is capable of stably starting an engine under a state where a battery voltage is low and reducing burdens upon a step-up circuit and a battery by stepping up the battery voltage.SOLUTION: An auxiliary power supply device 1 comprises: a step-up circuit 4 which steps up an input voltage from a battery; a step-up control part 5 which controls a step-up operation of the step-up circuit 4; and a START voltage detection part 6 which detects the input voltage from the battery. The step-up control part 5 starts the step-up operation in a case where the input voltage detected by the START voltage detection part 6 rises and the input voltage becomes higher than a first voltage, and stops the step-up operation in the case where the input voltage detected by the START voltage detection part 6 falls and the input voltage becomes lower than a second voltage, the second voltage being lower than the first voltage.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an auxiliary power supply apparatus having a function of boosting a voltage of a battery mounted on a vehicle or the like.

  Since the voltage of a battery mounted on a vehicle or the like tends to decrease during engine cranking (starting), there is a possibility that the operation of the on-vehicle electronic device cannot be guaranteed due to power reduction. In view of this, a technique has been proposed in which an engine can be started stably by using an auxiliary power supply device including a booster circuit that boosts the battery voltage (for example, Patent Document 1).

JP 2009-75725 A

  The output of a battery also decreases due to deterioration over time or use in a low temperature environment. In that case, the battery voltage during engine cranking is very low. However, if the auxiliary power supply device is configured so that an extremely low battery voltage (for example, less than 5 V) can be boosted at all times, the input current to the booster circuit increases and the temperature of the booster circuit increases. As a result, the load on the booster circuit and the battery is increased, and there is a possibility that the deterioration of the booster circuit and the battery is accelerated.

  The present invention has been made to solve the above problem, and by boosting the battery voltage, the engine can be stably started under a low battery voltage, and the booster circuit and the battery It is an object of the present invention to provide an auxiliary power supply device that has a low burden on the user.

  An auxiliary power supply apparatus according to the present invention is made to solve the above-described problem, and includes a booster circuit that boosts an input voltage from a battery, and a boost control unit that controls a boost operation of the booster circuit. The auxiliary power supply device further includes a voltage detection unit that detects an input voltage from the battery, and the boosting control unit detects that the input voltage is a first voltage when the input voltage detected by the voltage detection unit is increased. The step-up operation is started when the voltage becomes higher, and the step-up operation is stopped when the input voltage becomes lower than the second voltage when the input voltage detected by the voltage detection unit drops. The voltage is lower than the first voltage.

  In the auxiliary power supply device, it is preferable that the boost control unit operates the boost circuit only when an engine connected to the battery is started.

  In the auxiliary power device, for example, the first voltage is 5V and the second voltage is 3.5V.

  According to the present invention, it is possible to provide an auxiliary power supply apparatus that can stably start an engine under a low battery voltage by boosting the battery voltage and that places less burden on the booster circuit and the battery. Can do.

It is a block diagram which shows the structure of the auxiliary power supply which concerns on one Embodiment of this invention. It is a circuit diagram which shows an example of a structure of the START voltage detection part of the said auxiliary power supply. It is a graph which shows an example of the input-output characteristic of the booster circuit of the said auxiliary power supply device. It is a figure which shows an example of each waveform of the input voltage and output voltage of the said auxiliary power supply device.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a configuration of an auxiliary power supply device 1 according to an embodiment of the present invention. The auxiliary power supply device 1 includes three input terminals + B_IN, ACC_IN, START_IN, three output terminals + B_OUT, ACC_OUT, START_OUT, and a ground terminal GND as connection terminals to the outside. Input terminals + B_IN, ACC_IN, and START_IN of the auxiliary power supply device 1 are connected to output terminals of a battery mounted on a vehicle or the like. The output terminals + B_OUT, ACC_OUT, and START_OUT of the auxiliary power supply 1 are connected to a load such as an engine or electrical equipment.

  The input terminal + B_IN is constantly supplied with power for power from the battery, and the power is output from the output terminal + B_OUT. The power for accessory power supply is input from the battery to the input terminal ACC_IN, and the power is output from the output terminal ACC_OUT. The power for starting the engine is input from the battery to the input terminal START_IN, and the power is output from the output terminal START_OUT. Since the three input terminals + B_IN, ACC_IN, and START_IN are connected to the same battery, the input voltages to these input terminals are equal to each other. Therefore, hereinafter, each input voltage from the battery input to the input terminals + B_IN, ACC_IN, and START_IN may be referred to as a battery voltage.

  Further, the auxiliary power supply device 1 includes a protection circuit 2, an ACC voltage detection unit 3, a boost circuit 4, a boost control unit 5, and a START voltage detection unit 6 in the casing. The protection circuit 2 is a circuit that protects the booster circuit and the booster controller from overvoltage, overcurrent, reverse connection, and the like. In the present embodiment, the protection circuit 2 is configured to operate when the ACC voltage detection unit 3 detects that the battery voltage from the input terminal ACC_IN has reached a predetermined value. The protection circuit 2 is not a configuration essential to the present invention, and is provided as necessary. The ACC voltage detection unit 3 can be configured by a hysteresis comparator similar to the START voltage detection unit 6 described later.

  The booster circuit 4 is a circuit having a function of boosting the input voltage. The specific circuit configuration of the booster circuit 4 is not particularly limited, and a known circuit configuration such as a chopper circuit can be employed. The booster circuit 4 has an input terminal connected to the input terminal + B_IN via the protection circuit 2, and boosts the battery voltage from the input terminal + B_IN to a predetermined voltage. The output terminal of the booster circuit 4 is connected to the output terminals + B_OUT, ACC_OUT, and START_OUT, and the power boosted by the booster circuit 4 can be output from the output terminals + B_OUT, ACC_OUT, and START_OUT.

  The output terminals ACC_OUT and START_OUT are connected to the booster circuit 4 via the switch SW, and the boosted power is output from the output terminals ACC_OUT and START_OUT only when the switch SW is ON. The switch SW can be composed of a bipolar transistor or the like, and conducts when an output signal from a START voltage detector 6 described later is at a high level.

  The step-up control unit 5 has a function of controlling the step-up operation of the step-up circuit 4 and is constituted by an integrated circuit in this embodiment. The step-up control unit 5 can detect the output of the step-up circuit 4 and perform feedback control. Thereby, the booster circuit 4 can maintain the output voltage during the boosting operation at a desired voltage (for example, 12 V) regardless of the fluctuation of the battery voltage from the input terminal + B_IN.

  The START voltage detector 6 is a circuit that detects the battery voltage from the input terminal START_IN, and corresponds to the voltage detector described in the claims. The boost control unit 5 controls the start and stop of the boost operation of the boost circuit 4 according to the value of the battery voltage detected by the START voltage detection unit 6. Specifically, the boost control unit 5 starts the boost operation when the battery voltage is higher than the first voltage when the battery voltage is increased, and the battery voltage is the second voltage when the battery voltage is decreased. The step-up operation is stopped when the voltage becomes lower, and the second voltage is lower than the first voltage. The values of the first voltage and the second voltage are not particularly limited, but in the present embodiment, the first voltage is 5V and the second voltage is 3.5V.

  As shown in FIG. 2, in the present embodiment, the START voltage detection unit 6 is configured as a hysteresis comparator having an operational amplifier AMP and three resistors R1 to R3. The non-inverting input terminal of the operational amplifier AMP is connected to the input terminal START_IN via the resistor R1, and the connection point between the resistor R1 and the non-inverting input terminal of the operational amplifier AMP is grounded via the resistor R2. The output terminal of the operational amplifier AMP is connected to the boost control unit 5 and is connected to the non-inverting input terminal of the operational amplifier AMP via the resistor R3. A constant reference voltage VREF is input to the inverting input terminal of the operational amplifier AMP. A comparison signal output from the output terminal of the operational amplifier AMP is input to the boost control unit 5 and the switch SW as an output signal of the START voltage detection unit 6.

  With such a circuit configuration, the START voltage detector 6 switches the output signal from the low level to the high level when the input voltage exceeds 5 V when the input voltage increases, and changes the output signal from the high level to the low level when the input voltage decreases. Switch. The step-up control unit 5 controls the step-up circuit 4 to start the step-up operation when the input signal from the START voltage detection unit 6 is at a high level. At the same time, since the switch SW shown in FIG. 1 is turned on, the power boosted by the booster circuit 4 is output from the output terminals + B_OUT, ACC_OUT, and START_OUT.

  Note that the hysteresis comparator may be configured so that the polarity of the output signal of the START voltage detector 6 is opposite to that described above. In this case, the boost control unit 5 controls the boost circuit 4 to perform a boost operation when the output signal from the START voltage detection unit 6 is at a low level.

  As shown in FIG. 1, the input terminals + B_IN, ACC_IN, and START_IN are bypass-connected to the output terminals + B_OUT, ACC_OUT, and START_OUT, respectively, via backflow prevention diodes. As a result, even when the booster circuit 4 is not performing a boosting operation, the powers input to the input terminals + B_IN, ACC_IN, and START_IN are output as they are from the output terminals + B_OUT, ACC_OUT, and START_OUT, respectively.

  As a result, the output voltage of the booster circuit 4 changes as shown in FIG. 3 according to the input voltage from the battery (input terminal START_IN). That is, until the input voltage reaches from 0V to 5V, the booster circuit 4 does not perform the boosting operation, so that the output voltage is equal to the input voltage. Thereafter, when the input voltage reaches 5V, the booster circuit 4 starts the boosting operation and the output voltage becomes 12V. Further, when the input voltage rises and exceeds 12V, the output voltage becomes equal to the input voltage. In addition, once the boosting operation by the boosting circuit 4 is started, the boosting circuit 4 continues the boosting operation due to the hysteresis characteristic of the START voltage detecting unit 6 even if the input voltage becomes 5 V or less thereafter, and the output voltage is It is maintained at 12V. Thereafter, when the input voltage drops below 3.5V, the booster circuit 4 stops the boosting operation, and the output voltage becomes equal to the input voltage.

  FIG. 4 is a diagram illustrating an example of waveforms of the input voltage to the input terminal + B_IN, ACC_IN, and START_IN and the output voltage from the output terminal + B_OUT, ACC_OUT, and START_OUT of the auxiliary power supply device 1 illustrated in FIG. When the vehicle equipped with the auxiliary power supply 1 and the battery is not driven, the battery voltage is input only to the power supply input terminal + B_IN. Further, since the booster circuit 4 does not perform the boosting operation, the battery voltage (hereinafter referred to as + B voltage) input to the input terminal + B_IN is output from the output terminal + B_OUT as it is via the bypass path. In the present embodiment, the rated output voltage of the battery is 12V. However, since the ambient environment temperature of the vehicle is low, the initial battery voltage is assumed to be reduced to 6V.

  Thereafter, when the user starts driving the vehicle, a battery voltage (hereinafter referred to as ACC voltage) is input to the input terminal ACC_IN at time t0, and a battery voltage (hereinafter referred to as START voltage) is input to the input terminal START_IN at time t1. Entered. Although the actual rise and fall slopes of the battery voltage are not vertical, for convenience of explanation, the rise and fall waveforms of the ACC voltage are shown vertically.

  At time t0, since the booster circuit 4 is not performing a boosting operation, the ACC voltage is directly output from the output terminal ACC_OUT via the bypass path.

  Thereafter, at time t1, the START voltage starts to rise, but since the booster circuit 4 is not performing a boosting operation, the START voltage is output as it is from the output terminal START_OUT via the bypass path.

  Thereafter, at time t2, the START voltage becomes higher than 3.5 V (second voltage). However, even at that time, because the START voltage detector 6 maintains the output signal to the boost controller 5 at a low level due to the hysteresis characteristic, the booster circuit 4 does not start the boost operation.

  Thereafter, when the START voltage becomes higher than 5 V (first voltage) in time, the START voltage detection unit 6 switches the output signal to the boost control unit 5 to a high level. As a result, the booster circuit 4 starts the boost operation, and as a result, the output voltage of the booster circuit 4 becomes 12V. Further, since the switch SW shown in FIG. 1 is also conducted, a voltage of 12 V is output from all the output terminals + B_OUT, ACC_OUT, and START_OUT. Thereby, even when the battery voltage is low, it is possible to supply the voltage necessary for starting the engine.

  Further, since the battery voltage becomes unstable during engine cranking, the waveforms of the + B voltage, the ACC voltage, and the START voltage are repeatedly decreased and increased. For this reason, the battery voltage may temporarily be a very low voltage of less than 5V. On the other hand, in this embodiment, even if the START voltage drops below 5 V at time t4, the START voltage detection unit 6 maintains the output signal to the boost control unit 5 at a high level due to the hysteresis characteristics. . Therefore, the booster circuit 4 continues the boosting operation, and the output voltage of the booster circuit 4 is maintained at 12V. Therefore, the engine can be started stably.

  Thereafter, when the start of the engine is completed, the START voltage falls. When the START voltage becomes lower than 3.5 V at time t5, the START voltage detection unit 6 switches the output signal to the boost control unit 5 to a low level. As a result, the booster circuit 4 stops the boosting operation, and the + B voltage, the ACC voltage, and the START voltage are output from the output terminals + B_OUT, ACC_OUT, and START_OUT, respectively, via the bypass path. Therefore, the boost control unit 5 can operate the booster circuit 4 only when the engine is started (in the present embodiment, the period from t3 to t5).

  Thereafter, the alternator starts generating power by rotating the engine, and the electric power is supplied to the battery. As a result, the battery voltage rises and reaches 12V and stabilizes at time t6. Thereafter, when the user stops driving the vehicle, at time t7, the ACC voltage falls and only the + B voltage is output from the output terminal + B.

  As described above, in the auxiliary power supply device 1 according to the present embodiment, once the START voltage becomes 5 V or more and the booster circuit 4 starts the boosting operation at the time of engine cranking, the START voltage subsequently decreases to less than 5 V. However, as long as the voltage is not lower than 3.5 V, the booster circuit 4 continues the boosting operation. Therefore, the engine can be stably started even when the battery voltage is low (for example, 5 V or more and less than 12 V) due to the aging of the battery or use in a low temperature environment.

  In addition, if the auxiliary power supply device is configured such that an extremely low battery voltage (for example, less than 5V) can be boosted at all times, the input current to the booster circuit may increase, and the booster circuit and the battery may deteriorate more rapidly. On the other hand, in the auxiliary power supply device 1 according to the present embodiment, in a state where the booster circuit 4 is not performing a boosting operation, the booster circuit 4 does not reach 5V even if the START voltage rises to 3.5V or higher. Does not start the boost operation. Therefore, when the battery voltage before driving the engine is extremely low, the engine is not started. Thereby, the burden on the booster circuit 4 and the battery can be reduced.

  As described above, the auxiliary power supply device 1 according to the present embodiment can stably start the engine under a low battery voltage, and can reduce the burden on the booster circuit 4 and the battery. .

  In the present embodiment, the first voltage and the second voltage that are the reference for starting / stopping the boosting operation of the booster circuit 4 are set to 5 V and 3.5 V, respectively, but the present invention is not limited to this. The first voltage and the second voltage can be appropriately changed according to the voltage required for starting the engine, the characteristics of the battery voltage with respect to temperature and aging, the boosting capability of the booster circuit, and the like.

  In the present embodiment, the boost control unit 5 controls the start / stop of the boost operation of the boost circuit 4 based on the change in the START voltage of the battery voltage. However, the present invention is not limited to this. The battery voltage serving as a reference for starting / stopping the boosting operation may be an ACC voltage or a + B voltage. However, as in the present embodiment, by setting the battery voltage that is the reference for starting / stopping the boost operation as the START voltage, the boost control unit 5 causes the boost circuit 4 to perform the boost operation only when the engine is started. Control. As a result, the boosting operation of the booster circuit 4 can be minimized.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  The auxiliary power supply according to the present invention can be applied not only to a vehicle having wheels, but also to a device that does not have wheels driven by an engine.

DESCRIPTION OF SYMBOLS 1 Auxiliary power supply device 2 Protection circuit 3 ACC voltage detection part 4 Boosting circuit 5 Boosting control part 6 START voltage detection part (voltage detection part)

Claims (3)

A booster circuit that boosts the input voltage from the battery;
A step-up control unit for controlling the step-up operation of the step-up circuit;
An auxiliary power supply device comprising:
A voltage detection unit for detecting an input voltage from the battery;
The boost control unit includes:
When the input voltage detected by the voltage detector rises, the boost operation is started when the input voltage becomes higher than the first voltage,
When the input voltage detected by the voltage detection unit drops, the boost operation is stopped when the input voltage becomes lower than the second voltage,
The auxiliary power supply device, wherein the second voltage is lower than the first voltage.   The auxiliary power supply device according to claim 1, wherein the boost control unit operates the boost circuit only when an engine connected to the battery is started.   The auxiliary power supply device according to claim 1 or 2, wherein the first voltage is 5V and the second voltage is 3.5V.

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