JP2005204421A - Power unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power unit which can downsize its power supply means resulting in the miniaturization of a whole body. <P>SOLUTION: This power unit is provided with a battery 1 which accumulates energy supplied from a motor-cum-generator 5 and supplies the first electric load 3 with it, a capacitor 2 which is connected in series to the battery 1, a DC/DC converter 7 which supplies the capacitor 2 with power, and a diode 8 which is used to switch a power source for supplying power to the second electric load 4 smaller in the tolerance of voltage regulation than the first electric load 3 and switches an energy accumulation source so that the power may be supplied from the battery 1 when the voltage of the battery 1 is at or over a specified value and that the power may be supplied from a series circuit composed of the battery 1 and the capacitor 2 when the voltage of the battery 1 is smaller than the specified value. Since the power is supplied from the battery 1 to the second electric load when the voltage of the battery 1 is at or over a specified value, the necessity of operating the DC/DC converter 7 at all times disappears, and it can be put at short-time rating, therefore the DC/DC converter 7, in its turn the power unit can be downsized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power supply device, and more particularly to an improvement of a power supply device mounted on a vehicle.

  In an idling stop type vehicle that stops an engine when stopped at an intersection or the like, the engine is frequently started when traveling in an urban area. When a large current flows through the battery as when the engine is started, the output voltage is lowered due to the internal impedance of the battery. In particular, when the battery is deteriorated and the internal impedance is high, or when the SOC (State Of Charge) is low and the open circuit voltage of the battery is low, the output voltage is significantly reduced. If the battery voltage decreases, it may cause flickering of headlamps and abnormal operation of in-vehicle devices.

  As a countermeasure, the following power supply device has been proposed. The power supply apparatus includes a battery that includes an engine starter and supplies power to a first load having a large voltage drop allowance rate, and a DC-DC converter that is fed from the battery side and transmits power to a second load having a low voltage drop allowance rate. Switch means for transmitting power from the battery to the second load without going through the DC-DC converter, voltage drop detection means for detecting information relating to the battery voltage drop, and power transmission through the switch means when no battery voltage drop is detected. Power transmission control means for permitting and stopping power transmission through the switch means when detecting a voltage drop of the battery and permitting power transmission through the DC-DC converter.

  That is, when it is assumed that the battery voltage is lowered, the DC-DC converter supplies power from the battery to the second load by boosting the DC-DC converter so that the battery voltage is sufficiently large. When voltage can be applied to the second load, power is supplied through the switch means without going through the DC-DC converter. Thereby, as a DC-DC converter, what is necessary is just to supply electric power only for a short time, and a comparatively small and lightweight thing can be used (for example, refer patent document 1).

Japanese Patent Laying-Open No. 2003-237501 (paragraph number 0007 and FIG. 1)

  The conventional power supply apparatus is configured as described above, and all the power supplied to the second load needs to be supplied from the DC / DC converter. Therefore, the DC / DC converter needs to have an output capacity corresponding to it. It was. Further, since the second load requires a voltage that is about the same as the open circuit voltage of the battery, it is necessary to use a battery voltage plus an alpha breakdown voltage for the elements and capacitor 2 that constitute the DC / DC converter. There was a limit to downsizing the device.

  The present invention has been made to solve the above-described problems, and is a first for supplying electric power to a second electric load having a smaller allowable voltage fluctuation rate than the first electric load. An object of the present invention is to obtain a power supply apparatus that can reduce the size of the power supply means for supplying power to the second energy storage source in the series circuit of the energy storage source and the second energy storage source, and thus can reduce the overall size. And It is another object of the present invention to provide a power supply device that can reduce the withstand voltage of the power supply means and can be further miniaturized.

  In the power supply device according to the present invention, a first energy storage source that stores energy supplied from the generator and supplies power to the first electrical load, and a second energy connected in series to the first energy storage source An energy storage source for supplying electric power to a second electric load having an allowable voltage fluctuation rate smaller than that of the first electric load; When the voltage of the first energy storage source is greater than or equal to a predetermined value, power is supplied from the first energy storage source, and when the voltage of the first energy storage source is less than the predetermined value, the first Switching means for switching to supply power from a series circuit of the energy storage source and the second energy storage source is provided.

  As described above, according to the present invention, the first energy storage source that stores energy supplied from the generator and supplies power to the first electrical load, and the second energy source connected in series to the first energy storage source Energy storage source, power supply means for supplying power to the second energy storage source, and energy for supplying power to the second electric load having a smaller allowable voltage fluctuation rate than the first electric load The storage source is switched. When the voltage of the first energy storage source is equal to or higher than a predetermined value, power is supplied from the first energy storage source, and when the voltage of the first energy storage source is lower than the predetermined value, Switching means for switching to supply power from a series circuit of one energy storage source and a second energy storage source, so that the second energy storage source is the first energy storage source. It is possible to assume also a low voltage, thus can be miniaturized can be those also low-voltage power supply unit. Further, since the power is supplied from the first energy storage source to the second electric load when the voltage of the first energy storage source is equal to or higher than a predetermined value, it is not necessary to always operate the power supply means and the operation time is shortened. As a result, the power supply means can be reduced in size, and the power supply device can be reduced in size.

Embodiment 1 FIG.
1 is a configuration diagram showing a configuration of a power supply device according to Embodiment 1 for carrying out the present invention. FIG. 2 is a flowchart for explaining the operation of the power supply apparatus, and FIG. 3 is an explanatory view for explaining the operation of the power supply apparatus. In FIG. 1, a battery 1 as a first energy storage source is connected to a first electric load 3 (for example, a pump motor) having a large voltage fluctuation tolerance as an in-vehicle device and an inverter 6.

  In this embodiment, the inverter (6) controls the motor (cum generator) 5 to start the engine, drive the wheels, and generate power. In addition, a small capacity capacitor 2 as a second energy storage source is connected in series to the battery 1, and a diode 8 as switching means is connected in parallel with the capacitor 2. A series circuit of the battery 1 and the capacitor 2 is connected to a second electric load 4 (for example, a headlamp) having a small voltage fluctuation allowable rate as an in-vehicle device. The DC / DC converter 7 as the power supply means controls the voltage of the capacitor 2 to an arbitrary voltage by supplying the power of the battery 1 to the capacitor 2.

  Next, the operation will be described. Here, it is assumed that the nominal voltage of the battery 1 is 12V, the voltage fluctuation allowable range of the first electric load 3 is 8 to 16V, and the voltage fluctuation allowable range of the second electric load 4 is 11 to 15V. Note that numerical values such as voltage are merely examples, and are not limited to the illustrated numerical values, unless otherwise specified. When the motor (generator / generator) 5 is generating electricity during normal driving of the vehicle, the voltage of the battery 1 is kept at 13 to 14V, and the first electric load 3 has a voltage of 13 to 14V. Have been supplied. At this time, the DC / DC converter 7 is in an operation stop state, the diode 8 is in an on state, and a voltage of 13 to 14 V is supplied to the second electric load 4. When the voltage of the battery 1 is greatly reduced, such as when the engine is restarted, the DC / DC converter 7 causes the sum of the voltage of the battery 1 and the voltage of the capacitor 2 to be within the allowable voltage range of the second electric load 4. To work.

  When the voltage of the battery 1 at the time of engine restart becomes 8V or less, the DC / DC converter 7 operates so that the voltage of the capacitor 2 becomes 3 to 7V, so that the second electric load 4 has a voltage of 11 to 15V. Can be supplied. In this case, since the capacitor 2 having a low breakdown voltage of about several volts to 10 volts can be used, the capacitor 2 can be reduced in size and loss. Further, when the DC / DC converter 7 is an insulation type DC / DC converter, a low withstand voltage element of 10 V or less can be used as the output semiconductor element, so that the DC / DC converter 7 can be downsized and low loss can be achieved. It becomes possible.

  Next, the operation of the DC / DC converter 7 will be described. The operation of the DC / DC converter 7 may be a constant voltage control of the addition voltage of the battery 1 and the capacitor 2, but the DC / DC converter 7 can be further downsized by performing the control as shown in the flowchart of FIG. . The details of the operation will be described below with reference to FIGS. As an operation start condition of the DC / DC converter 7, an addition voltage (Vb + Vc) (see FIG. 3) of the voltage Vb of the battery 1 and the voltage Vc of the capacitor 2 (see FIG. 3) is from a voltage allowable lower limit (11 V) of the second electric load 4. Is larger than a predetermined first threshold voltage Vth1 (for example, 11.5 V) (step S1), the operation is started (step S2). During the operation of the DC / DC converter 7, constant voltage control is performed so that the added voltage (Vb + Vc) of the battery 1 and the capacitor 2 becomes a predetermined set voltage Vref (step S3). It is set to a value (for example, 13 V) lower than the charging voltage (13.5 to 15 V).

  With the above control, the load current of the battery 1 changes as indicated by the broken line J in FIG. 3, and the voltage of the battery 1 drops as indicated by Vb, but the added voltage obtained by adding the voltages of the battery 1 and the capacitor 2 is a dotted line. (Vb + Vc), and is kept at (11-13V) which is a value within the allowable voltage range (11-15V) of the second electric load 4. By the operation of the DC / DC converter 7, power is supplied to the second electric load 4 from both the DC / DC converter 7 and the capacitor 2. A broken line P in FIG. 3 is an operation amount of the DC / DC converter 7.

The operation stop condition of the DC / DC converter 7 is a second threshold voltage Vth2 (the added voltage (Vb + Vc) of the battery 1 and the capacitor 2 does not exceed the allowable voltage upper limit value (15V) of the second electric load 4). For example, when it exceeds 13.5 V), the operation is stopped (step S4). When the operation of the DC / DC converter 7 is stopped, the operation returns to step S1 and the operation is not started until it becomes lower than the first threshold voltage Vth1 (11.5V) which is the operation start condition of the DC / DC converter 7 again. . By controlling in this way, the DC / DC converter 7 starts operating when the added voltage (Vb + Vc) of the battery 1 and the capacitor 2 falls below 11.5V, and stops operating when it exceeds 13.5V. The DC / DC converter 7 having a short-time rating can be used, and the DC / DC converter 7 can be downsized, and the power supply device itself can be downsized.

  Further, the diode 8 of the semiconductor switch has been described as the switching means, but the same effect can be obtained with a mechanical switch such as a relay or a contactor. Moreover, although the apparatus which combined the motor (generator / generator) 5 and the inverter 6 was demonstrated as an engine starting device or a power generator, it is not restricted to this, The apparatus using a cell motor, an alternator, and a rectifier has the same effect.

Embodiment 2. FIG.
FIG. 4 is a block diagram showing a power supply device according to Embodiment 2 of the present invention. In FIG. 4, a MOSFET 9 as a first opening / closing means is connected in series with the capacitor 7. Since other configurations are the same as those of the first embodiment shown in FIG. 1, the same reference numerals are given to the corresponding components and the description thereof is omitted. The diode 8 as the second opening / closing means may be a parasitic diode of the MOSFET 9. In this case, the loss of the diode 8 can be reduced by operating the MOSFET 9 in a synchronous rectification operation. The first and second opening / closing means constitute the switching means of the present invention.

  Next, the operation will be described. When the motor (cum generator) 5 is performing a power generation operation during normal traveling of the vehicle, the MOSFET 9 is off. Further, the internal resistance of the battery 1 is estimated from information such as the temperature monitor of the battery 1 and the battery control unit, and the voltage drop value of the battery 1 at the time of engine restart is estimated. Based on the estimated voltage drop value of the battery 1, the DC / DC converter 7 is operated to charge the capacitor 2 to a desired voltage.

  There is no particular operation while the vehicle is stopped, and the operation at the time of engine restart is the same as in the first embodiment except that the MOSFET 9 is turned on almost simultaneously with the operation start timing of the DC / DC converter 7. In this embodiment, since the capacitor 2 is charged with a voltage corresponding to the voltage drop of the battery 1, a desired output voltage (the voltage of the battery 1 and the voltage of the capacitor 2 is immediately after the start of the operation of the DC / DC converter 7. The sum of the voltages (Vb + Vc)) can be obtained.

  As described above, according to the second embodiment, the MOSFET 9 as the second switch means is provided in series with the capacitor 2, and the capacitor 2 is initially charged according to the estimated voltage drop of the battery 1, The transient response of the DC / DC converter 7 can be improved, and a stable voltage can be supplied to the second electric load 4. Further, by using a large-capacity capacitor (for example, an electric double layer capacitor) as the capacitor 2, further effects can be obtained. The electric double layer capacitor has a capacitance of several F (farad) to several hundred F, and can output in the order of subseconds to several tens of seconds. While the vehicle is running, the MOSFET 9 is turned off, the large-capacity capacitor 2 is charged little by little by the DC / DC converter 7, and the MOSFET 9 is turned on when the engine is restarted. The rated capacity of 7 can be greatly reduced.

Further, by using an electric double layer capacitor as the voltage compensating capacitor 2, not only the DC / DC converter 7 but also the power of the battery 1 is supplied to the second electric load 4 having a small voltage fluctuation allowable rate. Therefore, the DC / DC converter 7 can be downsized. For example, if the power consumption of the second electric load 4 is 100 W and the voltage of the capacitor 2 is 4 V, the power to be transmitted by the DC / DC converter 7 is 100 × 4 / (4 + 8) = 33.3 W.
Thus, according to the present embodiment, by using a large-capacity electric double layer capacitor as the capacitor 2, the DC / DC converter 7 converter 7 can be further reduced in size.

Embodiment 3 FIG.
FIG. 5 is a block diagram showing a power supply device according to Embodiment 3 of the present invention. In FIG. 5, a second power for connecting a second battery 10 having a smaller capacity than the battery 1 in series with the battery 1 and transmitting power between the battery 1 and the second battery 10 as necessary. A second DC / DC converter 11 as a supply means is connected. The second battery 10 is the third energy storage source in the present invention.

  An inverter 6 for causing the motor (cum-generator) 5 to perform a power running operation and a power generation operation is connected to a series circuit of the battery 1 and the second battery 10. Since other configurations are the same as those of the first embodiment shown in FIG. 1, the same reference numerals are given to the corresponding components and the description thereof is omitted. Such a configuration is a known technique disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-218667 as a technique for increasing the output of a motor. Even in such a configuration in which a plurality of batteries are connected in series, when a large current flows through the battery 1 as when the engine is restarted, the battery voltage is lowered, which may adversely affect the in-vehicle devices connected to the battery 1. There is sex.

In the third embodiment of the present invention, the input power supply of the DC / DC converter 7 is the second battery 10, and the voltage of the capacitor 2 is controlled. With such a configuration, a non-insulated step-down converter can be used as the DC / DC converter 7, and the DC / DC converter 7 can be reduced in size and cost.
Instead of the second battery 10, a large capacity capacitor such as an electric double layer capacitor may be used.

Embodiment 4 FIG.
FIG. 6 is a block diagram showing a power supply device according to Embodiment 4 of the present invention. In FIG. 6, a MOSFET 9 as a first opening / closing means is connected in series with the third battery 22. A DC / DC converter 27 is provided to charge the third battery 22. The diode 8 as the second opening / closing means may be a MOSFET parasitic diode. Since other configurations are the same as those of the second embodiment shown in FIG. 4, the corresponding components are denoted by the same reference numerals and description thereof is omitted.

  The operation is also the same as that shown in FIG. 4, and the MOSFET 9 is turned off when the motor (generator / generator) 5 is performing a power generation operation during normal traveling of the vehicle. Further, the internal resistance of the battery 1 is estimated from information such as a battery temperature monitor and a battery control unit, and a battery voltage drop value at the time of engine restart is estimated. The DC / DC converter 27 is operated based on the estimated battery voltage drop value, and the third battery 22 is charged.

  There is no particular operation while the vehicle is stopped, and the operation at the time of engine restart turns on the MOSFET 9 almost simultaneously with the operation start timing of the DC / DC converter 27. In this embodiment, since the third battery 22 is charged with energy commensurate with the voltage drop of the battery 1, the desired output voltage (battery 1 and third battery is selected immediately after the start of the operation of the DC / DC converter 27. 22). If the capacity of the third battery 22 is increased, it is not necessary to start the operation of the DC / DC converter 27 in response to the input of a large current load such as an engine restart temple for a short time, and at an arbitrary timing. It can also be operated.

  Thus, according to this embodiment, the MOSFET 9 as the first opening / closing means is provided in series with the third battery 22, and the third battery 22 is initially charged according to the estimated voltage drop of the battery 1. Thus, there is no need to ask the transient response of the DC / DC converter 27, and a stable voltage can be supplied to the second electric load 4. Further, the MOSFET 9 is turned off while the vehicle is running, the third battery 22 is charged little by little by the DC / DC converter 27, the MOSFET 9 is turned on when the engine is restarted, and the charging energy of the third battery 22 is used. As a result, the rated capacity of the DC / DC converter 27 can be significantly reduced.

  As described above, according to the present invention, the first energy storage source that stores energy supplied from the generator and supplies power to the first electrical load, and the second energy source connected in series to the first energy storage source Energy storage source, power supply means for supplying power to the second energy storage source, and energy for supplying power to the second electric load having a smaller allowable voltage fluctuation rate than the first electric load The storage source is switched. When the voltage of the first energy storage source is equal to or higher than a predetermined value, power is supplied from the first energy storage source, and when the voltage of the first energy storage source is lower than the predetermined value, Switching means for switching to supply power from a series circuit of one energy storage source and a second energy storage source, so that the second energy storage source is the first energy storage source. It is possible to assume also a low voltage, thus can be miniaturized can be those also low-voltage power supply unit. Further, since the power is supplied from the first energy storage source to the second electric load when the voltage of the first energy storage source is equal to or higher than a predetermined value, it is not necessary to always operate the power supply means, and the operation time is shortened. As a result, the power supply means can be reduced in size, and the power supply device can be reduced in size.

  Since the power supply means supplies power from the first energy storage source to the second energy storage source, power is easily supplied using the first energy storage source. And the device becomes simple.

  Furthermore, the generator has a third energy storage source connected in series with the first energy storage source, and the generator supplies energy to the series circuit of the first energy storage source and the third energy storage source. The power supply means supplies power from the third energy storage source to the second energy storage source, so that power can be supplied from the generator to the third energy source. it can.

  The power supply means operates when the sum of the voltage of the first energy storage source and the voltage of the second energy storage source is less than a predetermined value, and exceeds another predetermined value larger than the predetermined value. Since the operation is sometimes stopped, it is possible to limit the operation time of the power supply means by using the operation start condition and the operation stop condition of the power supply means, and use the one with a short-time rating. Thus, it is possible to reduce the size of the power supply means and thus the power supply device.

  The switching means includes a first opening / closing means and a second opening / closing means. The first opening / closing means is connected in series with the second energy storage source, and the second opening / closing means is the first opening / closing means. Since it is connected in parallel to a series circuit of one switching means and a second energy storage source, the sum of the voltage of the first energy storage source and the voltage of the second energy storage source For example, when the value becomes larger than a predetermined value, the first opening / closing means is opened and the second opening / closing means is closed so that power is directly supplied from the first energy storage source to the second electric load. This makes it possible to apply a stable voltage to the second electric load even when the first energy storage source voltage suddenly increases.

  Further, the second energy storage source is a capacitor, and the switching means is a unidirectional conducting element connected in parallel with the capacitor. Therefore, the second energy storage source and the switching means are simplified. it can.

  In addition, it has voltage drop value estimation means for estimating the voltage drop value of the first energy storage source when the first electric load is loaded, and the power supply means is in accordance with the estimated voltage drop value. Since the power supplied to the capacitor is adjusted, the voltage drop value during the operation of an instantaneous high load such as an engine starter or an electric power steering is calculated from the temperature or internal resistance of the first energy storage source, for example. Estimate the power supplied to the capacitor, that is, the initial charging voltage of the capacitor according to the estimated voltage drop value of the first energy storage source. In addition, a stable voltage can be applied to the second electric load.

  Since the capacitor is an electric double layer capacitor, it is possible to reduce the size of the power supply device by enabling a large electric power to be supplied to the second electric load using the electric double layer capacitor having a large capacity. Is possible.

It is a block diagram which shows the structure of the power supply device which is Embodiment 1 of this invention. 3 is a flowchart for explaining the operation of the power supply device of FIG. 1. It is explanatory drawing for demonstrating operation | movement of the power supply device of FIG. It is a block diagram which shows the structure of the power supply device which is Embodiment 2 of this invention. It is a block diagram which shows the structure of the power supply device which is Embodiment 3 of this invention. It is a block diagram which shows the structure of the power supply device which is Embodiment 4 of this invention.

Explanation of symbols

1 battery, 2 capacitor, 3 first electrical load, 4 second electrical load,
5 Motor (cum generator), 7 DC-DC converter, 8 Diode,
9 MOSFET, 10 second battery, 11 second DC-DC converter,
22 DC-DC converter, 27 3rd battery.

Claims (8)

A first energy storage source for storing energy supplied from the generator and supplying power to the first electrical load; a second energy storage source connected in series to the first energy storage source; and the second energy storage source A power supply means for supplying power to the energy storage source, and an energy storage source for supplying power to the second electric load having an allowable voltage fluctuation rate smaller than that of the first electric load. When the voltage of the first energy storage source is equal to or higher than a predetermined value, power is supplied from the first energy storage source, and when the voltage of the first energy storage source is smaller than the predetermined value, the first energy A power supply device comprising switching means for switching to supply power from a series circuit of a storage source and the second energy storage source. The power supply apparatus according to claim 1, wherein the power supply means supplies power from the first energy storage source to the second energy storage source. A third energy storage source connected in series to the first energy storage source, and the generator supplies energy to a series circuit of the first energy storage source and the third energy storage source The power supply unit according to claim 1, wherein the power supply means supplies power from the third energy storage source to the second energy storage source. The power supply means starts operation when the sum of the voltage of the first energy storage source and the voltage of the second energy storage source is less than the predetermined value. The power supply apparatus according to any one of claims 1 to 3, wherein the operation is stopped when a predetermined value is exceeded. 5. The device according to claim 1, wherein the second energy storage source is a capacitor, and the switching unit is a one-way conductive element connected in parallel with the capacitor. 6. Power supply. The switching means has a first opening / closing means and a second opening / closing means, and the first opening / closing means is connected in series with the second energy storage source, and the second opening / closing means. 5. The power supply device according to claim 1, wherein the power supply device is connected in parallel to a series circuit of the first opening / closing means and the second energy storage source. 6. . It has voltage drop value estimation means for estimating the voltage drop value of the first energy storage source when the first electric load is loaded, the second energy storage source is a capacitor, The power supply device according to claim 6, wherein the power supply means adjusts the power supplied to the capacitor in accordance with the estimated voltage drop value. The power supply device according to claim 6 or 7, wherein the capacitor is an electric double layer capacitor.

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