JP2007209143A - Power supply unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply unit capable of suppressing a large voltage drop of a low-voltage system power source, even if electric power is supplied from the low-voltage system power source to a high-voltage one when an increase of a consumed current of a high-voltage system load causes the reduction of a the charged capacity of the high-voltage system power source. <P>SOLUTION: This power supply unit 1 is provided with the low-voltage system power source 3 that supplies electric power to a low-voltage system load 2, the high-voltage system power source 5 that supplies electric power to the high-voltage system load 4, a DC-DC converter 6 that connects the low-voltage system power source 2 to the high-voltage system one 4 in such a way as to make it possible for them to receive or give electric power, and a control means 7 that controls the DC-DC converter 6 so as to supply electric power from the low-voltage system power source 3 to the high-voltage system one 5 when the charged capacity of the high-voltage system power source 5 is equal to or lower than a first prescribed capacity. When the high-voltage system power source 5 discharges electricity, the control means 7 limits an output current of the DC-DC converter 6 to a predetermined value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric power supply device that supplies electric power to in-vehicle devices such as passenger cars, buses, and trucks.

  In recent vehicles, an electric power steering device (EPS) is often equipped for the purpose of reducing a driver's operating force. The electric power steering device is provided with a torque sensor such as a torsion bar on the steering shaft, detects the operating force of the driver's steering wheel by the torque sensor, drives the electric motor according to the operating force, and operates It is a force assist.

  In addition, recent vehicles are equipped with an electronically controlled brake system (ECB) to instantly and finely control the optimum braking force for each wheel based on vehicle information such as the driver's brake pedal operation amount and wheel speed. In some cases, an electric stabilizer (STB) for performing finer vehicle attitude control may be provided.

  Since these electric power steering devices (EPS), electronically controlled brake systems (ECB), electric stabilizers (STB), etc. are high-voltage loads that require a large amount of electric power during operation, vehicles on which these devices are mounted Will be equipped with a power supply device that combines a normal low-voltage power supply with a high-voltage power supply.

As such a power supply device, there is one as described in Patent Document 1, and is configured by connecting a low-voltage power supply and a high-voltage power supply as described above so as to be able to transmit and receive power by a DC / DC converter. . In such a power supply device, when the power consumption of the high voltage system load increases and the charge amount of the high voltage system power supply decreases, the DC / DC converter is controlled to supply power from the low voltage system power supply to the high voltage system power supply. The Of course, when the electric power of the high-voltage power supply is supplied from the low-voltage power supply, the DC / DC converter performs boosting simultaneously.
JP 2002-176704 A

  However, in such a power supply device, the power consumption of the high-voltage load is caused by a sudden operation of the high-voltage load such as an electric power steering device (EPS), an electronically controlled brake system (ECB), or an electric stabilizer (STB). When power is supplied from the low-voltage power supply to the high-voltage power supply by the DC / DC converter when the charging amount of the high-voltage power supply decreases, there arises a problem that the voltage drop of the low-voltage power supply becomes large.

  If the voltage drop of the low-voltage power supply becomes large, problems such as the flashing of bulb-type lamps such as headlights and interior lights will occur. To prevent this, power generation by an alternator connected in parallel to the low-voltage power supply If the amount is increased, the engine load may become too large, leading to an engine stall.

  In view of the above problems, the present invention provides a low-voltage power supply even when power is supplied from the low-voltage power supply to the high-voltage power supply when the current consumption of the high-voltage load increases and the charge amount of the high-voltage power supply decreases. It aims at providing the electric power supply apparatus which can suppress that the voltage drop of becomes large.

In order to solve the above problems, a power supply device according to the present invention includes a low-voltage power supply that supplies power to a low-voltage load, a high-voltage power supply that supplies power to a high-voltage load, the low-voltage power supply, and the high-voltage power supply. A DC / DC converter for connecting a system power supply so as to be able to transmit and receive power, and a power supply from the low voltage system power supply to the high voltage system power supply when the charge amount of the high voltage system power supply is equal to or less than a first predetermined amount. A power supply device comprising a control means for controlling a DC / DC converter,
When the high-voltage power supply is discharged, the control means limits the output current of the DC / DC converter to a predetermined value.

  Here, when the amount of charge of the high-voltage system power supply cannot be supplied to the high-voltage system load only by the high-voltage system power supply, the high-voltage system power supply is charged in order to give priority to the power supply to the high-voltage system load. If the amount is less than or equal to the second predetermined amount, the control means does not limit the output current of the DC / DC converter. The second predetermined amount is smaller than the first predetermined amount.

  Here, in order to limit the output current of the DC / DC converter with simpler control, the control means sets the DC / DC converter so that the predetermined value is the charging current value of the high-voltage power supply immediately before the discharging. It is preferable to feedback control the DC converter.

  According to the present invention, when the power consumption of the high voltage system load increases and the charge amount of the high voltage system power supply decreases, even if power is supplied from the low voltage system power supply to the high voltage system power supply, the voltage drop of the low voltage system power supply Can be prevented from becoming large.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing an embodiment of a power supply apparatus according to the present invention.

  The power supply apparatus 1 according to the present embodiment includes a first battery 3 as a low-voltage power supply that supplies power to the low-voltage load 2, a second battery 5 as a high-voltage power supply that supplies power to the high-voltage load 4, The DC / DC converter 6 that connects the first battery 3 and the second battery 5 so as to be able to exchange power, and the first battery 3 to the second battery 5 when the second battery 5 alone cannot supply power to the high-voltage load 4. And an ECU 7 as a control means for controlling the DC / DC converter 6 so as to supply electric power. In addition, a current sensor 8a, a voltage sensor 8b, and a temperature sensor 8c for detecting the charging / discharging current, voltage, and temperature of the lithium battery 5 are provided. These sensors are connected to the ECU 7 and are connected to the positive electrode side of the first battery 3. A positive electrode side of an alternator 9 driven by an engine (not shown) is connected.

  The first battery 3 as a low-voltage system power source is configured by a rechargeable power source such as a well-known Pb battery, for example, and supplies power to the low-voltage system load 2 and is charged by the alternator 9 while the engine (not shown) is driven. Is done. The second battery 5 as the high-voltage power supply is composed of a secondary battery such as a lithium battery that is excellent in charging performance and easy to detect the state of charge, for example. Of course, the low voltage side power source and the high voltage side power source are not limited to this combination as long as they can be charged. In particular, the high-voltage power supply can be a capacitor or an electrolytic double layer capacitor.

  Further, the DC / DC converter 6 has a well-known configuration in which, for example, a choke coil (not shown) and a switching element are combined, and when power is supplied from the low voltage system power source to the high voltage system power source, the output current and output voltage are charged to the choke coil. It is controlled by changing the ratio of time to discharge time and their alternating repetition period.

  The charge / discharge current, voltage, and temperature signals of the second battery 5 detected by the current sensor 8a, voltage sensor 8b, and temperature sensor 8c are input to the ECU 7, and the charge / discharge current, voltage, and temperature of these second batteries 5 are input. The ECU 7 calculates the charge amount of the second battery 5 using the above as a parameter, and if the charge amount is equal to or less than the first predetermined amount, the ECU 7 determines that the second battery 5 alone cannot supply power to the high-voltage load 4. The ECU 7 controls the DC / DC converter 6 so as to supply electric power from the first battery 3 which is a low-voltage power supply to the second battery 5 which is a high-voltage power supply. In this state, when the current sensor 8a detects the discharge of the second battery 5 as the high-voltage power supply, the ECU 7 limits the output current of the DC / DC converter 6 to a predetermined value.

  According to this, when the power consumption of the high voltage system load 4 such as EPS increases and the amount of charge of the second battery 5 as the high voltage system power supply decreases, the second battery 5 from the first battery 3 as the low voltage system power supply decreases. Even if power is supplied to the battery 5 by the DC / DC converter 6, the output current of the DC / DC converter 6 is limited to a predetermined value, so that the voltage drop of the first battery 3, which is a low-voltage power supply, increases. Can be suppressed.

  Here, as described above, it is preferable that the ECU 7 feedback-controls the DC / DC converter 6 so that the predetermined value becomes the charging current value of the high-voltage power supply 5 immediately before discharging. According to this, as will be described below, the present invention can be implemented with simpler control, and the control is performed as described below as compared with the feedback control by detecting the state of the low-voltage power supply and the alternator. Performance can be increased.

  Hereinafter, specific control results realized by the above-described power supply apparatus according to the present invention will be described with reference to the drawings. FIG. 2 is a time chart showing each current waveform of the power supply apparatus according to the present invention. In FIG. 2, the DC / DC converter is denoted as DDC.

  When the charge amount of the second battery 5 as the high-voltage power supply becomes equal to or less than the first predetermined amount at time α, power is supplied from the first battery 3 to the second battery 5 by the DC / DC converter 6 under the control of the ECU 7. start. As the charging of the second battery 5 proceeds, the second battery charging current 10 decreases, and accordingly, the ECU 7 controls the DC / DC so that the output current 12 of the DC / DC converter 6 becomes equal to the second battery charging current. The converter 6 is feedback controlled.

  At time β, the high-voltage load 4 starts to operate, and the discharge of the second battery 5 starts. At the same time, the ECU 7 controls the DC / DC converter 6 so that the output current of the DC / DC converter 6 becomes equal to the charging current of the second battery 5 immediately before discharging, and the output current of the DC / DC converter is Perform current limit. This current limitation continues until time γ when the operation of the high-voltage load 4 ends, and the current limit value is fixed from time β to time γ.

  At time γ, when the high voltage system load 4 ends its operation and the discharge current of the second battery is switched to the charging current, the ECU 7 controls the DC / DC converter 6 so as to gradually increase the current limit value. (2) The current limit value is gradually increased until the time δ when the charging current of the battery 5 reaches a peak. Here, the reason why the current limit value is gradually increased is to suppress the voltage drop of the first battery 3 even from the time γ to the time δ. After the time δ, as the charging of the second battery 5 progresses, the charging current of the second battery 5 gradually decreases due to the constant control of the output voltage of the DC / DC converter 6. The output current of the DC / DC converter 6 is also subjected to feedback control so as to be equal to the charging current of the second battery 5 and gradually decreases.

  This will be described below with reference to a flowchart for realizing the control result described above. FIG. 3 is a flowchart showing the control contents of the power supply apparatus according to the present invention. In FIG. 3, the DC / DC converter is represented as DDC.

  In S1, the current sensor 8a, the voltage sensor 8b, and the temperature sensor 8c detect the charge / discharge current, voltage, and temperature of the second battery 5, respectively, and the ECU 7 calculates the charge amount of the second battery 5 based on these parameters. The state is detected, and in S2, the ECU 7 compares the amount of charge with a second predetermined amount, and determines whether or not the second battery 5 can supply power to the high-voltage load. If it is determined that the amount of charge is larger than the second predetermined amount and power can be supplied, the process proceeds to S3. In S3, the initial value of the current limit value of the output current of the DC / DC converter 6 is set to the value of the second battery 5. The ECU 7 controls the DC / DC converter 6 so as to be equal to the charging current value immediately before discharging. If it is determined in S2 that the charge amount is smaller than the second predetermined amount and power cannot be supplied, the process proceeds to S10, and the current limitation of the output current of the DC / DC converter 6 is not performed. In this case, priority is given to power supply to the high-voltage load, and the voltage drop of the low-voltage power supply is allowed in reverse.

  When S3 and S10 are completed, the process proceeds to S4, where the ECU 7 again detects the state of the second battery 5 (charge / discharge current, voltage, temperature, and the charge amount calculated from these), and in S2, the second battery is based on the charge amount. Whether or not it is possible to supply power to the high-voltage load 4 with only 5 is determined. If it is determined that the amount of charge is greater than the second predetermined amount and power can be supplied, the process proceeds to S6. If it is determined that the amount of charge is less than the second predetermined amount and power cannot be supplied, the process proceeds to S11. The output current of the DC / DC converter 6 is not limited.

  In S6, it is determined by the ECU 7 whether the second battery 5 is being charged. If the battery is being charged, the process proceeds to S7, and if not, the process proceeds to S12. Further, the ECU 7 determines whether or not the previous value of the charging / discharging current of the second battery 5 detected at a predetermined sampling period in S7 is a charging current. If it is a charging current, the process proceeds to S8, and the DC / DC converter 6 is a value obtained by adding a predetermined additional value ε to the charging current of the second battery 5. If the previous value of the charge / discharge current of the second battery is not the charge current, the process proceeds to S12.

  That is, when it is determined in S6 that the second battery 5 is discharging, and in S7, it is determined that the previous value of the charging / discharging current of the second battery 5 detected at a predetermined sampling period is not a charging current. In this case, in S12, the output current of the DC / DC converter 6 is fixed to the previous value of the charge / discharge current of the second battery.

  When the process of any of S11, S12, and S8 is finished and it is determined in S9 that the ignition key is off, the control is finished. If the ignition key is not off, the process returns to S4 and only the second battery 5 is returned again. Thus, the ECU 7 determines whether power can be supplied to the high-voltage load 4. Thereafter, a control loop is configured based on the determinations of S5, S6, and S7.

  When these processes are applied to the time chart shown in FIG. 2, since it is determined that power cannot be supplied to the high voltage system load 4 only by the second battery 5 in S5 shown in FIG. The process is executed, the DC / DC converter 6 does not limit the output current, and the second battery 5 is charged.

  At the instant of time β, it is determined in S5 that only the second battery 5 can supply power to the high voltage system load 4, it is determined in S6 that the second battery 5 is being charged, and in S7, the second battery 5 is being charged. 2 Since it is determined that the previous value of the charge / discharge current of the battery 5 is the charge current, the process of S8 is executed, and the current limit value of the output current of the DC / DC converter 6 is set to the charge current of the second battery 5. The added value ε is added.

  From time β to time γ, it is determined in S5 that power can be supplied to the high voltage system load 4 only by the second battery 5, and in S6, it is determined that the second battery 5 is not being charged. The process of S12 shown in FIG. 3 is executed, and the current limit value of the output current of the DC / DC converter 6 is fixed to the previous current limit value.

  From time γ to time δ, it is determined in S5 that only the second battery 5 can supply power to the high-voltage system load 4, and it is determined in S6 that the second battery 5 is being charged, and in S7 Since it is determined that the previous value of the charge / discharge current of the second battery 5 is the charge current, the process of S8 shown in FIG. 3 is executed, and the current limit value of the output current of the DC / DC converter 6 is the second battery 5. The charging current is repeatedly set to a value obtained by adding the predetermined additional value ε, and the output current of the DC / DC converter 6 gradually increases. By gradually increasing the output current from time γ to time δ, the voltage drop of the low-voltage power supply can be suppressed even during this period.

  In this way, the output current of the DC / DC converter 6 is feedback controlled by the charge / discharge current of the second battery 5 which is a high-voltage power supply, and the output of the DC / DC converter is output while the second battery 5 is discharged. By limiting the current as a charging current value (predetermined value) immediately before the second battery 5 is discharged, the control result shown in FIG. 2 is realized. This is because the failure timing of the first battery 3 and the alternator 9 cannot be predicted as compared with the case where the feedback control is performed by detecting the state of the first battery and the alternator 9 as the low-voltage power supply. Thus, even if the output current of the DC / DC converter 6 is limited after the first battery 3 and the alternator 9 have failed, the problem that the control is not in time when the processing time communication delay in the ECU 7 is assumed is eliminated. Can do.

  Further, the DC / DC converter 6 is controlled by the charge / discharge current of the second battery 5 even during a period when the current limitation of the DC / DC converter 6 is not performed (a period when the high-voltage system load 4 does not operate and the second battery 5 is not discharged). By performing feedback control, it is possible to suppress an increase in the voltage drop of the low-voltage power supply by minimizing the power taken out from the first battery 3 that is the low-voltage power supply even during a period when current limitation is not performed. it can.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions are made to the above-described embodiments without departing from the scope of the present invention. be able to.

  The present invention relates to a power supply device of a dual power supply system that combines a low-voltage power supply and a high-voltage power supply, and is effective when applied to a vehicle equipped with the above-described high-voltage load such as EPS, ECB, and STB. It can be applied to various vehicles such as passenger cars, trucks, buses, etc., because the effect of suppressing the voltage drop of the low-voltage power supply can be obtained by adding relatively minor devices and changing the control contents. . Of course, the present invention can also be applied to a hybrid vehicle that can include an inverter and a generator motor as a high-voltage load.

It is a circuit diagram which shows one Example of the electric power supply apparatus which concerns on this invention. It is a time chart which shows each current waveform of the electric power supply apparatus which concerns on this invention. It is a flowchart which shows the control content of the electric power supply apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power supply apparatus 2 Low voltage system load 3 1st battery 4 High voltage system load 5 2nd battery 6 DC / DC converter 7 ECU
8a Current sensor 8b Voltage sensor 8c Temperature sensor 9 Alternator

Claims (3)

A low-voltage system power source that supplies power to the low-voltage system load; a high-voltage system power source that supplies power to the high-voltage system load; a DC / DC converter that connects the low-voltage system power source and the high-voltage system power source so as to be able to exchange power; And a control means for controlling the DC / DC converter so as to supply electric power from the low-voltage power supply to the high-voltage power supply when a charge amount of the high-voltage power supply is equal to or less than a first predetermined amount. And
When the high-voltage power supply is discharged, the control means limits the output current of the DC / DC converter to a predetermined value.   2. The power supply device according to claim 1, wherein when the charge amount of the high-voltage power supply is equal to or less than a second predetermined amount, the control unit does not limit the output current of the DC / DC converter. .   3. The power supply apparatus according to claim 1, wherein the control unit performs feedback control of the DC / DC converter so that the predetermined value is a charging current value of a high-voltage power supply immediately before the discharge.

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