JP2002181853A - Voltage detecting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage detecting circuit capable of detecting the abnormality of the voltage in plural voltage sources at a low cost. SOLUTION: This voltage detecting circuit comprises a detecting part 5 having npn-type first transistors 51 respectively mounted on each capacitor 2, inputting a voltage corresponding signal corresponding to the voltage of the capacitor 2 at its base terminal, and being connected to a bias power source at its collector terminal, and ppn-type second transistors inputting the voltage corresponding signal at its base terminal, and being connected to an emitter terminal of the first transistor 51 at its emitter terminal, a first connecting wire 6 connecting the emitter terminals of the first resistors 51 of the detecting parts 5, a second connecting wire 7 connecting the collector terminals of the second transistors 52 in the detecting parts 5, and an abnormality detecting terminal 8 connected to the second connecting wire 7. This voltage detecting circuit detects the abnormality in the voltage balance in plural capacitors 2 connected in series.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage detecting circuit for detecting an abnormal voltage balance in a plurality of voltage sources connected in series.

[0002]

2. Description of the Related Art Conventionally, as a voltage detecting circuit for connecting a plurality of voltage sources in series and detecting the voltages of the voltage sources, the voltage source is a battery as described in Japanese Patent Application Laid-Open No. H11-233154. The voltage detection line is pulled out from both ends of each battery connected in series, the voltage detection line is input to the differential amplifier, the output voltage of the differential amplifier is detected, and the voltage of each battery is individually detected. Are known.

[0003]

However, the voltage detection circuit described above can detect the voltage state of each voltage source, but cannot detect whether the voltage state is abnormal. In order to detect abnormalities in the voltage state, for example, that the voltages of the batteries connected in series are non-uniform using the voltage detection circuit, the output voltages of the differential amplifiers are compared and detected using a comparator It is possible. However, when there are many voltage sources to be detected, a comparator is required for each voltage source, so that the voltage detection circuit becomes expensive.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a voltage detection circuit capable of detecting a voltage abnormality in a plurality of voltage sources at low cost. .

[0005]

That is, a voltage detecting circuit according to the present invention is provided for each voltage source in a voltage detecting circuit for detecting an abnormal voltage balance in a plurality of voltage sources connected in series. An npn-type first transistor having a terminal to which a voltage-corresponding signal corresponding to the voltage of the voltage source is input and a bias power supply connected to a collector terminal;
A detecting unit having a pnp-type second transistor whose voltage corresponding signal is input to the base terminal and whose emitter terminal is connected to the emitter terminal of the first transistor, and a detecting unit that connects between the emitter terminals of the first transistor in each detecting unit. It is characterized by comprising one connection line, a second connection line connecting between the collector terminals of the second transistors in each detection unit, and an abnormality detection terminal connected to the second connection line.

According to the present invention, while having a simple structure in which an npn-type first transistor and a pnp-type second transistor are main components, any one of a plurality of voltage sources such as capacitors connected in series is used. When the voltage difference is on, the base-emitter voltage VF1 of the first transistor
When the voltage becomes equal to or higher than the sum of (VF1 + VF2) and the base-emitter voltage VF2 of the second transistor, it is possible to detect that the voltage balance of the voltage source is abnormal. That is, it is possible to detect an abnormality in the voltage balance of the voltage sources connected in series with a simple structure, and to realize the abnormal voltage detection at low cost.

Further, since the emitter terminal of each first transistor is connected to the first connection line, a reverse voltage may be applied between the emitter and base of the first transistor.
When the reverse voltage exceeds VF2, the second transistor is turned on and the reverse voltage between the emitter and the base of the first transistor does not exceed VF2. That is, in this voltage detection circuit, the second transistor functions as a protection circuit for the first transistor. Therefore, the first transistor can be prevented from exceeding the maximum rating, and the first transistor can be prevented from being damaged.

In the voltage detection circuit according to the present invention, the detection section may include a potential difference generating means for generating a predetermined potential difference between a base terminal of the first transistor and a base terminal of the second transistor. Features.

According to the present invention, since the second transistor is easily turned on, an abnormality can be detected even when the voltage difference between the voltage sources connected in series is small.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In each of the drawings, the same elements are denoted by the same reference numerals, and redundant description will be omitted. Also, the dimensional ratios in the drawings do not always match those described.

(First Embodiment) FIG. 1 shows a voltage detection circuit according to this embodiment.

As shown in FIG. 1, a voltage detecting circuit 1 according to the present embodiment is a circuit for detecting an abnormal voltage balance in a plurality of capacitors 2 connected in series. The capacitor 2 serves as a voltage source for a certain load,
Multiple connections are made. As the capacitor 2, an ultracapacitor, a power capacitor cell, or the like is used.

For the whole series connected capacitors,
The generators 3 are connected in series. The generator 3 is a charging unit that applies a voltage to the entire capacitor 2 at a time to charge each capacitor 2. For example, a generator that receives a brake load of a vehicle and generates power is used. In this case, the voltage detection circuit 1 is mounted on the vehicle together with the generator 3.

A voltage / current conversion circuit (V / I conversion circuit) 4 is provided for each capacitor 2. The voltage-current conversion circuit 4 is a voltage conversion unit that converts the voltage of the capacitor 2 into a current. Both ends of the capacitor 2 are connected to the input terminal of the voltage-current conversion circuit 4, and a current i corresponding to the voltage value of the capacitor 2 is output from the voltage-current conversion circuit 4. The voltage-current conversion circuit 4 allows the voltages of the capacitors 2 having different potentials to be handled as signals having the same potential.

As a voltage conversion means for converting the voltage of the capacitor 2, a photocoupler or the like may be used.

On the output side of the voltage-current conversion circuit 4, a detection unit 5 is provided. The detection unit 5 is a detection unit that detects the voltage of the capacitor 2, receives a current output from the voltage-current conversion circuit 4, and receives the current from the capacitor 2 according to the current.
Detects the voltage state of

A plurality of detectors 5 are provided corresponding to the capacitors 2 and the voltage-current converter 4. Detector 5
Includes a first transistor 51, a second transistor 52, and a resistor 53. The resistor 53 is provided between the input terminal of the detection unit 5 and the ground. The resistance 53 has the same resistance value in each detection unit 5.

The current i output from the voltage-current conversion circuit 4
Most flows through the resistor 53, and a voltage corresponding to the current i, that is, a voltage (voltage corresponding signal) corresponding to the voltage of the capacitor 2 is generated between both ends of the resistor 53.

The first transistor 51 is an npn-type transistor, and has a base terminal connected to one end of the resistor 53. Therefore, the voltage generated at the resistor 53 is input to the base terminal. The collector terminal of the first transistor 51 is connected to a constant voltage bias power supply.

The second transistor 52 is a pnp transistor, and has a base terminal connected to one end of the resistor 53. Therefore, the voltage generated at the resistor 53 is input to the base terminal. The emitter terminal of the second transistor 52 is connected to the emitter terminal of the first transistor 51.

The voltage detection circuit 1 is provided with a first connection line 6 and a second connection line 7. The first connection line 6 is a wiring that connects between the emitter terminals of the first transistor 51 in each detection unit 5. A resistor 61 is provided between the first connection line 6 and the ground.

The second connection line 7 is a wiring connecting between the collector terminals of the second transistors 52 in the respective detection units 5. A resistor 71 is provided between the second connection line 7 and the ground. An abnormality detection terminal 8 is connected to the second connection line 7. The abnormality detection terminal 8 is a terminal that detects an abnormality in the voltage balance of the plurality of connected capacitors 2.

Next, the operation of the voltage detection circuit according to this embodiment will be described.

In FIG. 1, when a predetermined charging voltage is applied to the entire capacitor 2 by the generator 3, each capacitor 2 is charged and the voltage of each capacitor 2 rises. At this time, the voltage of each capacitor 2 is
Is input to

The voltage-current conversion circuit 4 outputs a current i corresponding to the voltage value of the capacitor 2 by the voltage input of the capacitor 2. The current i output from each voltage-current conversion circuit 4 is input to the detection unit 5. Then, the current i flows through the resistor 53 of the detection unit 5 and a voltage V corresponding to the current i.
gives rise to i. This voltage Vi is applied to the first transistor 5
1 and the base terminal of the second transistor 52.

With the input of the voltage Vi, the voltage V51 at the emitter terminal of the first transistor 51 becomes Vi-VBE. VBE is a voltage between the base terminal and the emitter terminal of the first transistor 51.

However, since the emitter terminal of the first transistor 51 of each detection unit 5 is connected by the first connection line 6, the first connection of the detection unit 5 corresponding to the capacitor 2 having the maximum voltage among the capacitors 2 is performed. Assuming that the emitter terminal voltage of the transistor 51 is V51MAX, the emitter terminal voltage of the first transistor 51 of each detection unit 5 becomes V51MAX through the first connection line 6.

At this time, only the first transistor 51 of the detector 5 corresponding to the capacitor 2 having the maximum voltage is turned on, and the first transistor 51 and the second transistor 52 are turned on.
Assuming that the base-emitter voltages in the ON state are VF1 and VF2 (about 0.6 V), VBE of the first transistor 51 becomes VF1. The first transistors 51 of the detection unit 5 corresponding to the other capacitors 2 are not turned on, and the V BE of those first transistors 51 becomes VF1 or less.

On the other hand, in the detecting section 5, since the emitter terminal of the first transistor 51 and the emitter terminal of the second transistor 52 are directly connected, the voltage V51MAX is input to the collector terminal of each second transistor 52. Further, a voltage Vi is input to the base terminal of the second transistor 52 in accordance with the state of charge of the capacitor 2.

At this time, if the voltage Vi input to the base terminal of the second transistor 52 is equal to or less than the voltage (V51MAX-VF2) obtained by subtracting VF2 from the voltage V51MAX input to the emitter terminal of the second transistor 52, The two transistors 52 are turned on. This is capacitor 2
Means that a voltage difference of VF1 + VF2 or more has occurred in the voltage i of any of the detection units 5 due to the difference in the charging voltages.

When the second transistor 52 of one of the detection units 5 is turned on, a current is output from the collector terminal of the second transistor 52 and flows to the resistor 71. As a result, the output of the abnormality detection terminal 8 becomes high (H).

When the output of the abnormality detection terminal 8 becomes high, the difference between the charging voltages of the capacitors 2 becomes larger than a predetermined voltage value, and the voltage balance of the capacitors 2 connected in series is abnormal. I understand.

On the other hand, in each of the detectors 5, the voltage Vi input to the base terminal of the second transistor 52 is changed to the voltage V input to the emitter terminal of the second transistor 52.
When the voltage is higher than the voltage obtained by subtracting VF2 from 51MAX (V51MAX-VF2), none of the second transistors 52 is turned on. This is because even if there is a difference in the charging voltage of the capacitor 2, the difference in the voltage i in the detecting unit 5 is equal to VF1 + V
It means smaller than F2.

The second transistor 5 of each detection unit 5
Since 2 is not turned on, no current is output from the collector terminal of the second transistor 52, and no current flows through the resistor 71. Therefore, the output of the abnormality detection terminal 8 becomes low (L).

When the output of the abnormality detection terminal 8 becomes low, the difference between the charging voltages of the capacitors 2 is equal to or less than a predetermined voltage value, and it is understood that there is no particular abnormality in the voltage balance of the capacitors 2 connected in series. .

As described above, according to the voltage detection circuit 1 of this embodiment, the npn-type first transistor 51 and p
The base of the first transistor 51 and the base of the second transistor 52 when one of the voltage differences in the plurality of capacitors 2 connected in series is in the ON state while having a simple structure including the np type second transistor 52 as a main component. When the voltage becomes equal to or higher than the voltage obtained by adding the voltage between the emitters (VF1 + VF2), it is possible to detect that the voltage balance of the capacitor 2 is abnormal. That is, it is possible to detect an abnormality in the voltage balance of the voltage sources connected in series with a simple structure, and to realize the abnormal voltage detection at low cost.

In the voltage detection circuit 1 according to the present embodiment, since the emitter terminal of the first transistor 51 is connected to the first connection line 6, a reverse voltage is applied between the emitter and the base of the first transistor 51. There are cases. However, when the reverse voltage exceeds VF2, the second transistor 52 is turned on and the emitter-
The reverse voltage between the bases does not exceed VF2. That is, in the voltage detection circuit 1, the second transistor 52 functions as a protection circuit for the first transistor 51. Therefore, a voltage exceeding the maximum rating can be prevented from being applied to the first transistor 51, and the first transistor 51 can be prevented from being damaged.

(Second Embodiment) Next, a voltage detection circuit according to a second embodiment will be described.

FIG. 2 shows a voltage detection circuit according to this embodiment. As shown in the figure, the voltage detection circuit 1a differs from the voltage detection circuit 1 of the first embodiment in the configuration of the detection unit 5. The detecting unit 5 of the voltage detecting circuit 1a includes a first transistor 51 and a second transistor 52 as potential difference generating means for generating a predetermined potential difference between the base terminal of the first transistor 51 and the base terminal of the second transistor 52.
Two diodes 54 and 55 and two resistors 56 and 57 are additionally provided in the input part on the base side of the.

The diodes 54 and 55 are disposed between the base terminal of the first transistor 51 and the resistor 53, and are connected in series in the forward direction toward the resistor 53. Resistance 5
Reference numerals 6 and 57 are connected in series between the base terminal of the first transistor 51 and the resistor 53, and are provided in the order of the resistors 56 and 57 from the base terminal side of the first transistor 51. A wiring portion between the resistor 56 and the resistor 57 is connected to a base terminal of the second transistor 52.

According to such a voltage detection circuit 1a, the base-emitter voltages when the first transistor 51 and the second transistor 52 are in the ON state are VF1 and VF, respectively.
F2, the forward voltage of the diodes 54 and 55 is VF (about 0.6 V), the resistance of the resistor 56 is Ra, and the resistance of the resistor 57 is Rb. Is VF1 + VF2-2
When VF · (Rb / (Ra + Rb)) or more, it is detected that the voltage balance of the capacitor 2 is abnormal.

Here, if VF1 + VF2 = 2 · VF,
In the voltage detection circuit 1a, any one of the voltage differences between the capacitors 2 connected in series is (VF1 + VF2).
When (Ra / (Ra + Rb)) or more, it is detected that the voltage balance of the capacitor 2 is abnormal.
Therefore, the voltage detection circuit 1 according to the first embodiment, which detects an abnormality when the voltage difference of the capacitor 2 is equal to or more than VF1 + VF2,
In the voltage detection circuit 1a according to the present embodiment, a smaller voltage difference ((VF1 + VF2) ・ (Ra / (Ra + R
Even if b))) occurs, abnormality detection becomes possible.

The resistance values Ra, Rb of the resistors 56, 57
Is changed, the capacitor 2 to be arbitrarily detected can be changed.
Can be set.

(Third Embodiment) In the voltage detection circuits according to the first embodiment and the second embodiment, a voltage detection circuit for detecting an abnormal voltage balance in a plurality of capacitors 2 connected in series has been described. The voltage detection circuit according to the present invention is not limited to such a circuit, and may detect a voltage balance abnormality of a voltage source when a plurality of other voltage sources such as batteries are connected in series.

[0045]

As described above, according to the present invention, an abnormality in the voltage balance of the voltage sources connected in series can be detected with a simple structure, and the voltage abnormality can be detected at low cost.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a voltage detection circuit according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a voltage detection circuit according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Voltage detection circuit 2 ... Capacitor (voltage source) 5 ... Detection part 6 ... First connection line 7 ... Second connection line 8 ... Abnormality detection terminal 51 ... First transistor 52 ... Second transistor

Claims (2)

[Claims] 1. A voltage detection circuit for detecting an abnormal voltage balance in a plurality of voltage sources connected in series, provided for each of the voltage sources, and a voltage corresponding signal corresponding to the voltage of the voltage source at a base terminal. And a pnp-type second transistor having a collector terminal connected to a bias power supply and a voltage-corresponding signal input to a base terminal and an emitter terminal connected to the emitter terminal of the first transistor. A detection unit having a transistor; a first connection line connecting between the emitter terminals of the first transistor in each of the detection units; and a second connection connecting between the collector terminals of the second transistor in each of the detection units. A voltage detection circuit comprising: a connection line; and an abnormality detection terminal connected to the second connection line. 2. The device according to claim 1, wherein the detection unit includes a potential difference generating unit that generates a predetermined potential difference between a base terminal of the first transistor and a base terminal of the second transistor. 2. The voltage detection circuit according to 1.