JP4035941B2 - Battery monitoring device for dual battery type electric vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery monitoring device for a two-battery electric vehicle.
[0002]
[Prior art]
In electric vehicles such as pure electric vehicles, fuel cell vehicles, and hybrid vehicles equipped with a secondary battery, a high voltage having a terminal voltage close to 300 V for transferring power to the vehicle motor to reduce resistance loss and miniaturize the control semiconductor element. It is advantageous to mount a battery (main battery) and a low-voltage battery having a terminal voltage of about 12V for supplying power to a control device, an audio device, and a conventional vehicle electric load.
[0003]
High-energy secondary batteries such as nickel metal hydride batteries and lithium batteries used as the main battery for electric vehicles have weak characteristics against overcharge and overdischarge, but secondary batteries for electric vehicles frequently charge and discharge. Precise capacity management is essential.
[0004]
In order to accurately manage the capacity of the main battery, it is necessary to accurately detect the terminal voltage of each battery block that is cascade-connected to form the main battery. The battery block is composed of one to a plurality of unit cells connected in cascade.
[0005]
Since the reference end (normally low end) potential of each battery block is different from each other, power is supplied to the terminal voltage detection circuit (hereinafter also referred to as voltage detection circuit) of each battery block that detects the potential of the high end with reference to these reference ends. Each power supply circuit that supplies voltage (hereinafter also referred to as a voltage detection circuit power supply circuit) needs to be electrically independent from each other.
[0006]
Since these power supply circuits for the voltage detection circuit only need to output a low voltage, in a two-battery type electric vehicle, an inverter that converts DC power from a low-voltage sub-battery into AC power, and a transformer having a plurality of secondary coils (hereinafter referred to as “secondary coil”) A multi-output type DC-DC converter composed of a rectifier that individually rectifies each secondary coil voltage is employed.
[0007]
[Problems to be solved by the invention]
In the above-described two-battery type electric vehicle, it is desired to supply power to a commercial frequency 100V AC load or a DC load having a voltage different from the sub-battery voltage through, for example, an outlet in order to improve the convenience for the driver. It is rare.
[0008]
This kind of different voltage load is fed from the main battery or sub battery through a DC-DC converter or inverter with a built-in transformer for voltage conversion, but in order to simplify the circuit configuration and reduce the vehicle weight It is easiest to supply power from one secondary coil of the multi-output transformer.
[0009]
In this case, the current supplied to the different voltage load fluctuates greatly due to its opening and closing, etc., and this current fluctuation affects not only the primary coil but also the secondary coil for feeding the voltage detection circuit. Feedback control of the primary current of the multi-output transformer according to the fluctuation of the applied voltage to compensate for the current change of the secondary coil for low voltage load power supply (electromagnetic power supply from the primary coil to the secondary coil for low voltage load power supply) It will be necessary.
[0010]
However, although detailed description of the circuit analysis is omitted, even if such feedback control is performed, the increase or decrease in the feeding current to the different voltage load eventually leads to an increase or decrease in the primary coil voltage of the multi-output transformer, In response to this, other secondary coil voltages are increased or decreased, and as a result, the detection characteristics of the voltage detection circuits are varied, and the voltage detection accuracy of the battery block is lowered.
[0011]
Although it is possible to improve this problem by providing a high-precision constant voltage circuit for each voltage detection circuit, it is not practical in terms of complication of the circuit configuration and increase in power loss.
[0012]
Further, when the different voltage load is short-circuited due to some abnormality, the power supply voltage of each voltage detection circuit is greatly increased. Therefore, it is necessary to add a protection circuit for each voltage detection circuit.
[0013]
The present invention has been made in view of the above problems, and provides a battery monitoring device for a two-battery electric vehicle capable of improving the voltage detection accuracy of the main battery while suppressing the complexity of the circuit configuration. It is aimed.
[0014]
[Means for Solving the Problems]
The battery monitoring device for a two-battery electric vehicle according to claim 1, wherein a high-voltage main battery configured by connecting a plurality of battery blocks in series, a low-voltage sub-battery, and a terminal voltage of each of the battery blocks are individually provided. A plurality of voltage detection circuits to detect, and a power supply voltage supply circuit that is supplied with power from the sub-battery and individually applies a power supply voltage to each of the voltage detection circuits and the low-voltage electric load,
The power supply voltage supply circuit includes: an inverter that converts DC power supplied from the sub battery into AC power; a primary coil that is supplied with the AC power; a plurality of secondary coils that supply voltage detection circuit; and low-voltage load power supply A multi-output transformer having a secondary coil for power supply, and each AC power output from each secondary coil for feeding the voltage detection circuit to individually rectify and feed each voltage detection circuit, and the low-voltage load In a battery monitoring device for a two-battery type electric vehicle, comprising a plurality of rectifiers that rectify AC power output from a secondary coil for power supply and convert it directly or into AC power of a predetermined frequency to supply power to a low-voltage electric load. ,
The electromagnetic coupling coefficient between the primary coil of the multi-output transformer and the secondary coil for feeding the low voltage load is based on the electromagnetic coupling coefficient between the primary coil and the secondary coil for feeding the voltage detection circuit. Is also set to be small.
[0015]
According to this configuration, since the electromagnetic coupling coefficient between the primary coil and the secondary coil for supplying the low voltage load is small (there is a large amount of leakage magnetic flux), the fluctuation of the primary coil current due to the current fluctuation of the low voltage load is reduced. Can do. In addition, the secondary coil for power supply to the voltage detection circuit is coupled to the primary coil with a better electromagnetic coupling coefficient than the secondary coil for low-voltage load power supply, so the power supply efficiency from the secondary battery to each voltage detection circuit is improved. Loss can be reduced.
[0016]
According to a second aspect of the present invention, in the battery monitoring apparatus for a two-battery electric vehicle according to the first aspect, the primary coil and each secondary coil are wound in a radial direction on the core of the multi-output transformer. The primary coil and the secondary coil for supplying the low-voltage load are arranged such that the secondary coil for each voltage detection circuit is sandwiched in the radial direction.
[0017]
According to this configuration, each coil is wound in a radial direction, and the secondary coil for voltage detection circuit power supply is interposed between the primary coil and the secondary coil for low voltage load power supply. The electromagnetic coupling coefficient according to item 1 can be realized.
[0018]
In a preferred embodiment, the primary coil is wound on the outermost side, and the secondary coil for feeding the low-voltage load is wound on the innermost side, or vice versa.
[0019]
According to the configuration of claim 3, in the battery monitoring device for a two-battery electric vehicle according to claim 1, the multi-output transformer further includes the primary coil, the secondary coil for each of the voltage detection circuits, and the low voltage. It is characterized by having a branch magnetic path member for increasing the leakage flux between the secondary coil for power feeding.
[0020]
According to this configuration, the leakage magnetic flux between the primary coil and the secondary coil for each voltage detection circuit and the secondary coil for low-voltage load power supply can be easily increased, and an increase in transformer size can be suppressed. The effect of claim 1 can be increased.
[0021]
In a preferred embodiment, a ferrite tape with a small eddy current loss is wound between the primary coil and the secondary coil for each voltage detection circuit and the secondary coil for low-voltage load power supply. If it does in this way, the electromagnetic coupling coefficient between the primary coil and each voltage detection circuit, the secondary coil, and the secondary coil for low voltage load electric power feeding can be reduced simply and without increasing a physique.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the following examples. However, the present invention is not limited to the configurations of the following embodiments, and can naturally be configured using a replaceable known circuit.
[0023]
[Example 1]
An embodiment of a voltage detection apparatus for a battery pack according to the present invention will be described with reference to FIG.
[0024]
(Circuit configuration)
Reference numeral 1 denotes an ignition switch, 2 denotes a low-voltage sub-battery, 3 denotes a main battery, 4 denotes a battery monitoring ECU, and the main battery 3 transmits and receives power to a travel motor (not shown) through an inverter device (not shown).
[0025]
The battery monitoring ECU 4 includes a smoothing circuit 41, an inverter circuit 42, a CR circuit 43, a multi-output transformer 44, rectifiers 45 to 47, smoothing capacitors 48 to 50, and voltage detection circuits 51 and 52.
[0026]
The inverter circuit 42 includes a source-grounded MOST 422 and a gate control circuit 42 that intermittently controls the MOST 422 at a predetermined frequency in a variable duty ratio.
[0027]
The multi-output transformer 44 includes a primary coil 441 and secondary coils 442 to 444 that are wound around a ferrite core 440 that constitutes a closed magnetic circuit in a radial multiple manner.
[0028]
The primary coil 441 of the multi-output transformer 44 is connected in series with the switching MOST 422, and a CR circuit 43 including a capacitor C and a resistor r connected in series with each other is connected in parallel to both ends of the MOST 422.
[0029]
The voltage of the sub battery 2 is applied to both ends of the primary coil 441 and the MOST 422 through the ignition switch 1 and the smoothing circuit 41.
[0030]
The AC outputs of the secondary coils 442 to 444 of the multi-output transformer 44 are individually rectified by the rectifiers 45 to 47, thereby being electrically insulated from each other and having different reference potentials. The DC voltages output from the rectifiers 45 and 46 fed from the secondary coils 442 and 443 for feeding the voltage detection circuit are individually ripple-removed by the smoothing capacitors 48 and 49 and then passed to the voltage detection circuits 51 and 52. Applied individually as power supply voltage.
[0031]
The DC voltage output from the rectifier 47 fed from the secondary coil 444 for feeding a low-voltage load (which is higher than the secondary battery in this embodiment) is not shown after ripple removal by the smoothing capacitor 50. Applied to external low pressure load.
[0032]
The smoothing capacitors 48 to 50 are each configured by connecting a large capacity electrolytic capacitor and a small capacity film capacitor in parallel. In this embodiment, DC power is supplied to an external low-voltage load, but it is needless to say that an AC load can be driven by interposing an inverter circuit.
[0033]
(Operation)
The operation of the circuit described above will be described.
[0034]
When the ignition switch 1 is turned on and the MOST 422 is turned on and off at a predetermined carrier frequency and a predetermined initial duty ratio, a direct current containing an alternating current component flows through the primary coil 441. An alternating voltage is induced at 444.
[0035]
Each AC voltage output from the secondary coils 442 to 444 is rectified by the rectifiers 45 to 47, smoothed by the smoothing capacitors 48 to 50, and applied to the voltage detection circuits 51 and 52 and an external load (not shown) as a power supply voltage. .
[0036]
The main battery 4 is configured by connecting a number of battery blocks in series, and each battery block is configured by connecting a number of single cells in series.
[0037]
The terminal voltage of each battery block is detected by different voltage detection circuits. However, in FIG. 1, only the voltage detection circuits 51 and 52 for detecting the voltages of the highest and lowest battery blocks are shown. The voltage detection operation of the voltage detection circuits 51 and 52 and the direct-to-parallel conversion operation itself by the inverter circuit 42 are not the gist of the present invention, and there are many variations, and thus description thereof is omitted.
[0038]
When the current supplied to the external low-voltage load by the primary coil 444 changes, the voltage output to the external load changes. This voltage change is fed back to the gate control circuit 421 of the inverter circuit 42 to change the duty ratio of the MOST 422. The voltage fluctuation is reduced by changing the alternating current component flowing through the primary coil 441. When the current flowing through the primary coil 441 increases, the output voltage of the secondary coils 442 to 443 increases.
[0039]
(Structure of multi-output transformer 44)
Therefore, in this embodiment, a multi-output transformer 44 having a unique structure shown in FIG. 2 is adopted.
[0040]
The ferrite core 440 of the multi-output transformer 44 includes a rod-shaped core portion 4401 and a square-shaped frame portion 4402, and constitutes a closed magnetic circuit as a whole. A resin bobbin 445 is fitted on the core portion 4401, and a primary coil 441 and secondary coils 442 to 444 are wound around the resin bobbin 445 so as to overlap in the radial direction.
[0041]
In this embodiment, a secondary coil 444 for supplying a low voltage load is wound on the innermost side, a primary coil 441 is wound on the outermost side, and secondary coils 442 to 443 are wound on the middle. In practice, the required number of secondary coils 442 to 444 are wound. The primary coil 441 and the secondary coil 444 may have opposite configurations.
[0042]
In this way, since the primary coil 441 and the secondary coil 444 for low-voltage load power supply are arranged away from each other in the radial direction, a leakage magnetic flux path is generated between them, and the coils 441 to 443 and 444 are connected to each other. The electromagnetic coupling coefficient between them decreases. For this reason, for example, the current of the primary coil 441 fluctuates due to the influence of the current fluctuation of the external low voltage load connected to the secondary coil 444 for supplying the low voltage load. It is possible to satisfactorily prevent the voltage from fluctuating.
[0043]
(Modification)
As shown in FIG. 3, a cylindrical member 446 in which a half cylinder made of nonmagnetic resin is combined may be interposed between the secondary coil 444 for supplying low-voltage load power and the other coils 441 to 443. In this way, the electromagnetic coupling coefficient between the coils 441 to 443 and 444 can be reduced. The cylindrical member 446 is also effective in improving the electrical withstand voltage between the coils. The cylindrical member 446 may be formed by winding an insulating tape thickly.
[0044]
Further, the cylindrical member 446 may be made of a half cylinder or a tape having a small eddy current loss such as ferrite. In this way, even if the thickness of the cylindrical member 446 is thin, the electromagnetic coupling coefficient between the coils 441 to 443 and 444 can be greatly reduced.
[0045]
Although the description is omitted in the above embodiment, a coil for forming the power supply voltage of the inverter circuit 42 may be additionally wound between the coils 441 and 444.
[0046]
[Example 2]
Another embodiment is shown in FIG.
[0047]
In this embodiment, a primary coil 441 and secondary coils 442 and 443 for feeding a voltage detection circuit are wound around a cylindrical shaft portion of a first ferrite core 100 formed in a bobbin shape. A secondary coil 444 for feeding a low voltage load is wound around a cylindrical shaft portion of a second ferrite core 101 that is combined with the core 100 to form a closed magnetic circuit.
[0048]
In this way, the electromagnetic coupling coefficient between the primary coil 441, the secondary coils 442 to 443, and the secondary coil 444 can be reduced with a simple structure.
[0049]
Further, in this embodiment, since the ferrite core 100 is formed in a bobbin shape, the bobbin can be omitted, and the number of parts can be reduced by that amount, thereby reducing the size and weight. FIG. 5 is a modification of FIG.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a battery monitoring device for a two-battery electric vehicle of Example 1. FIG.
FIG. 2 is a cross-sectional view of the multi-output transformer of FIG.
3 is a cross-sectional view showing a modification of the multi-output transformer of FIG.
4 is a cross-sectional view showing a modification of the multi-output transformer of FIG.
5 is a sectional view showing a modification of the multi-output transformer of FIG.
[Explanation of symbols]
2 Sub battery 3 Main battery 4 Battery monitoring ECU (power supply voltage supply circuit)
44 Multi-output transformer 441 Primary coil 442 Secondary coil 443 for feeding voltage detection circuit Secondary coil 444 for feeding voltage detection circuit Secondary coil 445 for feeding low voltage load Cylindrical member (branch magnetic path member)
51 Voltage Detection Circuit 52 Voltage Detection Circuit 42 Inverter Circuit (Inverter)
45 Rectifier 46 Rectifier 47 Rectifier

Claims (3)

A high-voltage main battery configured by connecting a plurality of battery blocks in series;
With a low-voltage secondary battery,
A plurality of voltage detection circuits for individually detecting the terminal voltage of each of the battery blocks;
A power supply voltage supply circuit for supplying a power supply voltage to each of the voltage detection circuit and the low-voltage electric load by being fed from the sub-battery;
With
The power supply voltage supply circuit includes:
An inverter that converts DC power fed from the sub-battery into AC power;
A multi-output transformer having a primary coil to which the AC power is supplied, a plurality of secondary coils for feeding a voltage detection circuit, and a secondary coil for feeding a low-voltage load;
Each AC power output from each secondary coil for voltage detection circuit power supply is individually rectified and supplied to each voltage detection circuit, and AC power output from the secondary coil for low voltage load power supply A number of rectifiers that rectify and convert directly to AC power of a predetermined frequency to supply low-voltage electric loads;
In a battery monitoring device for a two-battery electric vehicle comprising:
The electromagnetic coupling coefficient between the primary coil of the multi-output transformer and the secondary coil for feeding the low voltage load is based on the electromagnetic coupling coefficient between the primary coil and the secondary coil for feeding the voltage detection circuit. A battery monitoring device for a two-battery type electric vehicle characterized by being set to be smaller. The battery monitoring device for a two-battery electric vehicle according to claim 1,
The primary coil and each secondary coil are wound in a radial direction around the core of the multi-output transformer,
The battery monitoring apparatus for a two-battery type electric vehicle, wherein the primary coil and the secondary coil for low-voltage load power supply are disposed with the secondary coil for each voltage detection circuit sandwiched in a radial direction. The battery monitoring device for a two-battery electric vehicle according to claim 1,
The multi-output transformer includes a branch magnetic path member that increases leakage magnetic flux between the primary coil and the secondary coil for each voltage detection circuit and the secondary coil for low-voltage load power supply. A battery monitoring device for a two-battery electric vehicle.

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