JP2001333501A - Battery monitor for two-battery electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery monitor for two-battery-type electric vehicles which enables enhancement in the accuracy of detecting the voltage of a main battery, without complication of the circuitry thereof. SOLUTION: The battery monitor comprises a main battery 3 of higher voltage, a sub-battery 2 of lower voltage, voltage detection circuits 51 and 52, and a supply voltage supplying circuit 3 that is supplied with power from the sub-battery 3 and supplies the voltage detection circuits 51 and 52 with power. The supply voltage supplying circuit 3 comprises an inverter 42, a multiple output-type transformer 44, and rectifiers 45 to 47. The coefficient of electromagnetic coupling between the primary coil 441 of the multiple output-type transformer 44 and the secondary coil 444 for power supply to low-voltage load is set to a value smaller than the coefficient of electromagnetic coupling between the primary coil 441 and the secondary coils 442 and 443 for power supply to voltage detection circuit. Therefor, the fluctuation in the supply voltage of the voltage detection circuits 51 and 52 due to the fluctuation in the current in the secondary coil 444 for power supply to low-voltage load is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery monitoring device for a two-battery electric vehicle.

[0002]

2. Description of the Related Art In an electric vehicle such as a pure electric vehicle, a fuel cell vehicle, and a hybrid vehicle on which a secondary battery is mounted, close to 300 V which exchanges electric power with a vehicle traveling motor in order to reduce resistance loss and downsize a control semiconductor element. It is advantageous to mount a high-voltage battery (main battery) having a terminal voltage and a low-voltage battery having a terminal voltage of about 12 V to supply power to a control device, an audio device, or a conventional vehicle electric load.

[0003] High-energy secondary batteries such as nickel-metal hydride batteries and lithium batteries used as main batteries of electric vehicles have characteristics that are susceptible to overcharge and overdischarge, but secondary batteries of electric vehicles frequently repeat charge and discharge. Therefore, precise capacity management is indispensable.

In order to precisely control the capacity of the main battery, it is necessary to precisely detect the terminal voltage of each battery block which is cascaded and constitutes the main battery. The battery block is 1
Or a plurality of cells connected in cascade.

Since the reference end (normally lower end) potential of each battery block is different from each other, a terminal voltage detection circuit (hereinafter, also referred to as a voltage detection circuit) of each battery block for detecting a higher end potential based on these reference ends. ) Must be electrically independent from each other (hereinafter, also referred to as a voltage detection circuit power supply circuit).

Since the power supply circuit for the voltage detection circuit only needs to output a low voltage, a two-battery electric vehicle has an inverter for converting DC power from a low-voltage sub-battery into AC power, and a plurality of secondary coils. A transformer (hereinafter, also referred to as a multi-output transformer) and a multiple-output DC-DC converter composed of a rectifier for individually rectifying each secondary coil voltage are employed.

[0007]

In the two-battery electric vehicle described above, for example, a 100 V AC load of a commercial frequency or a DC load of a voltage different from the sub-battery voltage is used to improve the driver's convenience. It is desired to supply power through outlets and the like.

[0008] This kind of different voltage load is supplied with power from a main battery or a sub-battery through a DC-DC converter or an inverter having a built-in transformer for voltage conversion, but the circuit configuration is simplified and the vehicle weight is reduced. For this purpose, it is easiest to supply power from one secondary coil of the multi-output transformer described above.

In this case, the power supply current to the different voltage load fluctuates greatly due to switching and the like, and this current fluctuation affects not only the primary coil but also the secondary coil for power supply of the voltage detection circuit. Feedback control of the primary current of the multi-output transformer according to the fluctuation of the voltage applied to the load to compensate for the current change of the secondary coil for low voltage load power supply (from the primary coil to the secondary coil for low voltage load power supply, Power supply).

[0010] However, although a detailed description of the circuit analysis is omitted, even if such feedback control is performed, the increase or decrease of the supply current to the different voltage load will eventually increase or decrease the primary coil voltage of the multi-output type transformer. Accordingly, the voltage of another secondary coil is increased or decreased in response to this, and as a result, the detection characteristics of each voltage detection circuit fluctuate and the voltage detection accuracy of the battery block is reduced.

Although it is possible to solve this problem by providing a high-precision constant voltage circuit for each of the voltage detection circuits, it is not practical in terms of a complicated circuit configuration and an increase in power loss.

Further, when the abnormal voltage load is short-circuited due to some abnormality, the power supply voltage of each voltage detecting circuit is greatly increased. Therefore, it is necessary to add a protection circuit for each voltage detecting circuit. occured.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a battery monitoring apparatus for a two-battery electric vehicle capable of improving the accuracy of detecting the voltage of a main battery while suppressing the complexity of the circuit configuration. That is the purpose.

[0014]

According to a first aspect of the present invention, there is provided a battery monitoring apparatus for a two-battery type electric vehicle, comprising: a high-voltage main battery, a low-voltage sub-battery configured by connecting a plurality of battery blocks in series; A plurality of voltage detection circuits that individually detect terminal voltages of the battery block, and a power supply voltage supply circuit that is supplied with power from the auxiliary battery and individually applies a power supply voltage to each of the voltage detection circuits and the low-voltage electric load. A power supply voltage supply circuit, an inverter for converting DC power supplied from the sub-battery into AC power, a primary coil to which the AC power is supplied, a plurality of secondary coils for supplying a voltage detection circuit, and a low voltage load. A multi-output type transformer having a secondary coil for power supply, and each AC power output from the secondary coil for power supply is individually rectified and supplied to each of the voltage detection circuits. A battery for a two-battery electric vehicle comprising: a plurality of rectifiers that rectify the AC power output from the secondary coil for supplying the low-voltage load and directly or convert the AC power to a predetermined frequency to supply power to the low-voltage electric load. In the monitoring device, the electromagnetic coupling coefficient between the primary coil of the multi-output type transformer and the secondary coil for supplying the low-voltage load is a value between the primary coil and the secondary coil for supplying the voltage detection circuit. It is characterized in that it is set smaller than the electromagnetic coupling coefficient.

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 can be reduced. Can be reduced. Also, since the secondary coil for supplying the voltage detection circuit is coupled to the primary coil with a better electromagnetic coupling coefficient than the secondary coil for supplying the low voltage load, the power supply efficiency from the secondary battery to each voltage detection circuit is improved. Thus, the loss can be reduced.

According to a second aspect of the present invention, in the battery monitoring device for a two-battery electric vehicle according to the first aspect, the primary coil and each of the secondary coils are radially connected to a core of the multi-output transformer. The primary coil and the secondary coil for supplying a low-voltage load are stacked and wound, and are arranged so as to sandwich the secondary coil for each of the voltage detection circuits in the radial direction.

According to this configuration, each coil is wound one on another in the radial direction, and the secondary coil for supplying the voltage detection circuit is interposed between the primary coil and the secondary coil for supplying the low voltage load. The electromagnetic coupling coefficient according to claim 1 can be realized by the structure.

In a preferred embodiment, the primary coil is wound on the outermost side and the secondary coil for supplying a low-voltage load is wound on the innermost side, but vice versa.

According to a third aspect of the present invention, in the battery monitoring device for a two-battery electric vehicle according to the first aspect, the multi-output type transformer further comprises a secondary coil for the primary coil and each of the voltage detection circuits. And a branch magnetic path member for increasing the leakage magnetic flux between the secondary coil for supplying the low voltage load.

According to this configuration, it is possible to easily increase the leakage magnetic flux between the primary coil and the secondary coil for each voltage detection circuit and the secondary coil for supplying the low-voltage load, and to increase the size of the transformer. The effect described in claim 1 can be increased.

In a preferred embodiment, a ferrite tape with small eddy current loss is wound between the primary coil and the secondary coil for each voltage detection circuit and the secondary coil for supplying a low-voltage load. In this way, the electromagnetic coupling coefficient between the primary coil and each voltage detection circuit, and between the secondary coil and the low voltage load power supply secondary coil can be reduced simply without increasing the physical size.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the following examples. However, the present invention is not limited to the configuration of the following embodiment, and it is obvious that the present invention can be configured using a replaceable known circuit.

[0023]

[Embodiment 1] An embodiment of a voltage detecting device for an assembled battery according to the present invention will be described with reference to FIG.

(Circuit configuration) 1 is an ignition switch, 2 is a low-voltage sub-battery, 3 is a main battery, 4 is a battery monitoring EC.
U, and the main battery 3 exchanges power with a traveling motor (not shown) through an inverter device (not shown).

The battery monitoring ECU 4 comprises a smoothing circuit 41, an inverter circuit 42, a CR circuit 43, a multi-output type transformer 44, rectifiers 45 to 47, smoothing capacitors 48 to 50,
It has voltage detection circuits 51 and 52.

The inverter circuit 42 has a source grounded MO.
ST 422 and a gate control circuit 42 that performs intermittent duty ratio variable control at a predetermined frequency.

The multi-output type transformer 44 has a primary coil 441 and secondary coils 442 to 444 wound around a ferrite core 440 constituting a closed magnetic circuit in a radially multiple manner.

Primary coil 4 of multi-output type transformer 44
Reference numeral 41 is connected in series with the switching MOST 422. Both ends of the MOST 422 are connected in parallel to a CR circuit 43 including a capacitor C and a resistor r connected in series with each other.

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.

Secondary coil 4 of multi-output type transformer 44
The AC outputs of 42-444 are individually rectified by rectifiers 45-47 so that each rectifier 45-47 is electrically isolated from one another and can have different reference potentials. Each DC voltage output from the rectifiers 45 and 46 supplied from the secondary coils 442 and 443 for supplying the voltage detection circuit is subjected to ripple removal individually by the smoothing capacitors 48 and 49.
The voltage is individually applied to the voltage detection circuits 51 and 52 as a power supply voltage.

The DC voltage output from the rectifier 47 supplied from the secondary coil 444 for supplying a low-voltage load (in this embodiment, the voltage is higher than that of the sub-battery), after the ripple is removed by the smoothing capacitor 50, Are applied to an external low-pressure load (not shown).

Each of the smoothing capacitors 48 to 50 is constituted 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. However, it is a matter of course that an AC load can be driven by interposing an inverter circuit.

(Operation) The operation of the above-described circuit will be described.

When the ignition switch 1 is turned on, the MO
When ST422 is intermittently performed at a predetermined carrier frequency and a predetermined initial duty ratio, a DC current including an AC current component flows through primary coil 441, and an AC voltage is induced in secondary coils 442 to 444 by a change in the AC current component. You.

Each AC voltage output from the secondary coils 442 to 444 is rectified by rectifiers 45 to 47, smoothed by smoothing capacitors 48 to 50, and supplied to the voltage detection circuits 51 and 52 and an external load (not shown) as a power supply voltage. Applied.

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 cells in series.

The terminal voltage of each battery block is detected by a different voltage detection circuit. However, FIG. 1 shows only the voltage detection circuits 51 and 52 that detect the voltages of the highest and lowest battery blocks. Voltage detection circuit 5
The voltage detection operations 1 and 52 and the cross-conversion operation itself by the inverter circuit 42 are not the gist of the present invention, and there are many variations, so the description is omitted.

When the current supplied from the primary coil 444 to the external low-voltage load changes, the voltage output to the external load fluctuates. This voltage fluctuation is fed back to the gate control circuit 421 of the inverter circuit 42 and the MOST 422
, And the AC current component flowing through the primary coil 441 is changed to reduce the voltage fluctuation.
When the current flowing through the primary coil 441 increases, the output voltage of the secondary coils 442 to 443 increases.

(Structure of Multi-Output Type Transformer 44) In this embodiment, a multi-output type transformer 44 having a unique structure shown in FIG. 2 is employed.

The ferrite core 440 of the multi-output type transformer 44 is composed of a rod-shaped core 4401 and a rectangular frame 4402, and constitutes a closed magnetic circuit as a whole. A resin bobbin 445 is fitted into the core 4401,
The resin bobbin 445 includes a primary coil 441 and a secondary coil 4.
42 to 444 are wound so as to overlap in the radial direction.

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 in the middle. Actually, the required number of secondary coils 442 to 444 are wound. Primary coil 441 and secondary coil 444
May be reversed.

With this arrangement, since the primary coil 441 and the secondary coil 444 for supplying a low-voltage load are arranged apart from each other in the radial direction, a leakage magnetic flux path is generated therebetween, and the coils 441 to 443 are connected to each other. 444 decreases. Therefore, 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, and the power supply of the voltage detection circuits 51 and 52 is influenced by these influences. Variations in voltage can be suppressed well.

(Modification) As shown in FIG. 3, a secondary coil 444 for supplying a low-voltage load and other coils 441 to 443 are provided.
And a cylindrical member 446 formed by combining half-cylinders made of non-magnetic resin. By doing so, the electromagnetic coupling coefficient between the coils 441 to 443 and 444 can be reduced. The cylindrical member 446 is also effective for improving the electric withstand voltage between the coils. This cylindrical member 446 may be formed by winding an insulating tape thickly.

Further, the cylindrical member 446 may be made of a half-split cylinder or tape such as ferrite having a small eddy current loss. In this way, even if the thickness of the cylindrical member 446 is small, the electromagnetic coupling coefficient between the coils 441 to 443 and 444 can be significantly reduced.

Although the description has been omitted in the above embodiment, a coil forming the power supply voltage of the inverter circuit 42 may be additionally wound between the coils 441 and 444.

[0046]

Embodiment 2 Another embodiment is shown in FIG.

In this embodiment, the primary coil 441 and the secondary coils 442, 44 for feeding the voltage detection circuit are mounted on the cylindrical shaft of the first ferrite core 100 formed in a bobbin shape.
3 and the second ferrite core 1 combined with the first ferrite core 100 to form a closed magnetic circuit.
01, a secondary coil 44 for supplying a low-voltage load to the cylindrical shaft portion.
4 is wound.

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.

In this embodiment, the ferrite core 1
Since 00 is formed in a bobbin shape, the bobbin can be omitted, the number of parts can be reduced by that much, and the size and weight can be reduced. 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 according to a first embodiment.

FIG. 2 is a cross-sectional view of the multi-output type transformer of FIG.

FIG. 3 is a sectional view showing a modification of the multi-output type transformer of FIG.

FIG. 4 is a cross-sectional view showing a modification of the multi-output type transformer of FIG.

FIG. 5 is a sectional view showing a modification of the multi-output type transformer of FIG.

[Explanation of symbols]

 2 Secondary battery 3 Main battery 4 Battery monitoring ECU (power supply voltage supply circuit) 44 Multi-output type transformer 441 Primary coil 442 Secondary coil for power supply of voltage detection circuit 443 Secondary coil for power supply of voltage detection circuit 444 For power supply of low voltage load Secondary coil 445 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)

[Claims] 1. A high-voltage main battery configured by connecting a plurality of battery blocks in series, a low-voltage sub-battery, a plurality of voltage detection circuits for individually detecting terminal voltages of the respective battery blocks, A power supply voltage supply circuit that is supplied from a 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 converts DC power supplied from the sub-battery into AC. An inverter for converting power, a primary coil to which the AC power is supplied, a multi-output type transformer having a plurality of secondary coils for supplying a voltage detection circuit and a secondary coil for supplying a low-voltage load, and each of the voltage detection circuits Each AC power output from the power supply secondary coil is individually rectified and supplied to each of the voltage detection circuits, and the AC power output from the low voltage load power supply secondary coil is regulated. And a plurality of rectifiers for directly or directly converting to a predetermined frequency of AC power and supplying power to a low-voltage electric load, a battery monitoring device for a two-battery electric vehicle, comprising: the primary coil of the multi-output transformer and the low voltage. A secondary battery, wherein an electromagnetic coupling coefficient between the secondary coil for power supply to the load and an electromagnetic coupling coefficient between the primary coil and the secondary coil for power supply to the voltage detection circuit is set to be smaller. Monitoring device for portable electric vehicles. 2. The battery monitoring device for a two-battery electric vehicle according to claim 1, wherein the primary coil and each of the secondary coils are wound around a core of the multi-output type transformer in a radial direction. A battery monitoring device for a two-battery electric vehicle, wherein the coil and the secondary coil for supplying a low-voltage load are arranged so as to radially sandwich the secondary coil for each of the voltage detection circuits. 3. The battery monitoring device for a two-battery electric vehicle according to claim 1, wherein the multi-output transformer includes a secondary coil for the primary coil and each of the voltage detection circuits and a secondary coil for supplying the low-voltage load. A battery monitoring device for a two-battery electric vehicle, comprising a branch magnetic path member for increasing leakage magnetic flux between the secondary coil and the secondary coil.