JP2005017289A - Switching circuit, and voltage measuring circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flying capacitor circuit and a voltage measuring circuit capable of using a semiconductor switch excellent in a cost, a size, durability, a response speed and the like, as a change-over switch. <P>SOLUTION: A minus side of a unit cell V<SB>m-1</SB>and a plus side of a unit cell V<SB>m</SB>connected to the minus side of the unit cell V<SB>m-1</SB>are connected to a capacitor via the common change-over switch S<SB>m</SB>. The change-over switch S<SB>m</SB>is constituted of two electric field effect transistors Q1, Q2 connected in series to make source drain directions reverse-directional each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a switching circuit and a voltage measuring circuit, and more particularly to a switching circuit that connects both ends of a battery connected in series to a capacitor and a voltage measuring circuit including the switching circuit.

As the conventional switching circuit described above, for example, the one shown in FIG. 5 has been proposed (for example, Patent Documents 1 and 2). As shown in the figure, the switching circuit includes one capacitor C for a plurality of unit cells V _{1 to} V _n connected in series, and both ends of the unit cells V _{1 to} V _n . A plurality of change-over switches S _{1 to} S _{n + 1} for sequentially connecting to both ends are provided. In FIG. 5, the unit cells V _{1 to} V _n are each composed of one battery.

There are (n + 1) changeover switches S _{1 to} S _{n + 1} for n unit cells V _{1 to} V _n . Thus, for example, the plus side of the unit cell V _1, and the negative side of the unit cell V ₂ which is connected to the positive side of the unit cell V _1, is connected to the capacitor C via a common changeover switch S ₂ It has become so. In addition, as shown in FIG. 6, a switching circuit in which two switches S _{1 to} S _2n are provided on both sides of each unit cell V _{1 to} V _n has also been proposed (for example, Patent Document 3).
Japanese Patent Laid-Open No. 11-248755 JP 2002-156392 A JP-A-11-248757

In the conventional switching circuit shown in FIGS. 5 and 6, relay switches are used as the changeover switches S _{1 to} S _{n + 1} and S _{1 to} S _2n . However, the relay switch has problems in terms of cost, size, durability, and response speed. For this reason, there has been a demand for using semiconductor switches that are excellent in these aspects as the changeover switches S _{1 to} S _{n + 1} and S _{1 to} S _2n .

However, since the semiconductor switch has a parasitic diode between the source and the drain, even if the changeover switches S _{1 to} S _{n + 1} and S _{1 to} S _2n are turned off, a current may flow through the parasitic diode. The unit cells V _{1 to} V _n and the capacitor C cannot be completely insulated.

  Accordingly, the present invention pays attention to the above-described problems, and provides a switching circuit and a voltage measurement circuit that can use a semiconductor switch excellent in cost, size, durability, response speed, etc. as a changeover switch. The issue is to provide.

  In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that both ends of each unit cell of an assembled battery formed by connecting a plurality of unit cells made of a capacitor and a battery in series are sequentially connected to the capacitor. A switching circuit comprising a plurality of changeover switches, wherein the changeover switch has two semiconductor switches connected in series so that the source-drain directions are opposite to each other Exist.

  According to the first aspect of the present invention, the change-over switch has two semiconductor switches connected in series so that the source-drain directions are opposite to each other. Therefore, by connecting two semiconductor switches so that the source-drain directions are opposite to each other, the forward directions of the parasitic diodes generated in the source-drain direction are opposite to each other. Thereby, when the semiconductor switch is off, no current flows through the parasitic diode.

  The invention according to claim 2 is the switching circuit according to claim 1, wherein the minus side of one unit cell and the plus side of the two unit cells connected to the minus side of the unit cell are The switching circuit is connected to the capacitor via the common changeover switch.

  According to the second aspect of the present invention, in the case of a switching circuit in which the negative side of one unit cell and the positive side of the second unit cell are connected to a capacitor via a common switch, Needs to pass bidirectional current. Therefore, by using two semiconductor switches whose source-drain directions are connected in opposite directions as the changeover switch, a current can flow in both directions, and the current flows through the parasitic diode when turned off. Nor.

  The invention according to claim 3 is the switching circuit according to claim 1 or 2, wherein a logic circuit that outputs a control signal instructing on / off of the semiconductor switch, and a level shift of the control signal, the semiconductor switch And a level shift circuit for outputting to the gate of the switching circuit.

  According to the invention described in claim 3, the logic circuit outputs a control signal instructing on / off of the semiconductor switch. The level shift circuit shifts the level of the control signal and outputs it to the gate of the semiconductor switch. Therefore, if the control signal is level-shifted by the level shift circuit, it is possible to control on / off of the semiconductor switch in which a high voltage is applied to the source by using the control signal output from the low-voltage logic circuit, which is expensive. It is not necessary to use a simple photo MOS.

  Invention of Claim 4 is the switching circuit of Claim 1 or 2, Comprising: The resistance element provided between the source-gate of the said semiconductor switch, the capacitor | condenser for drive connected to the both ends of this resistance element, and the said The switching circuit includes an oscillation circuit that applies an AC voltage to both ends of the resistance element via a drive capacitor.

  According to the fourth aspect of the present invention, when an AC voltage from the oscillation circuit is applied to the resistance element via the drive capacitor, a bias is applied between the source and gate of the semiconductor switch to turn on the two semiconductor switches. Can do. According to the above configuration, since the oscillation circuit and the assembled battery can be galvanically isolated by the drive capacitor, the oscillation circuit can use a low-voltage power supply different from the assembled battery as a power source.

  The invention according to claim 5 is the switching circuit according to claim 4, wherein a drive switch provided between the oscillation circuit and the drive capacitor, and a control signal for instructing on / off of the drive switch are provided. And a logic circuit for output.

  According to the fifth aspect of the present invention, when the drive switch is turned on, the AC voltage from the oscillation circuit is applied to the resistance element via the drive capacitor. The drive switch is controlled to be turned on / off by a control signal from a logic circuit. According to the above configuration, a single oscillation circuit can be provided for a plurality of changeover switches.

  The invention according to claim 6 is the switching circuit according to any one of claims 1 to 5, wherein the semiconductor switch connected to the plus side of the unit cell on the highest voltage side among the changeover switches is Pch. The other semiconductor switches are Nch. It exists in the switching circuit characterized by being.

  According to the invention described in claim 6, among the changeover switches, the semiconductor switch included in the changeover switch connected to the positive side of the unit cell on the highest voltage side is Pch. The other switch has a semiconductor switch Nch. It is. Therefore, Pch. If the semiconductor switch is not used, an inexpensive Nch. Except for the semiconductor switch connected to the positive terminal of the unit cell on the highest voltage side that cannot be turned on. The semiconductor switch can be used.

  A seventh aspect of the present invention is the switching circuit according to any one of the first to sixth aspects, wherein the voltage measuring means measures the voltage across the capacitor, and between the both ends of the capacitor and the voltage measuring means. The voltage measurement circuit further includes two semiconductor switches connected in series so that the source-drain directions are opposite to each other.

  According to the seventh aspect of the present invention, the measurement switch provided between the capacitor and the voltage measuring means has two semiconductor switches connected in series so that the source-drain directions are opposite to each other. Therefore, by connecting two semiconductor switches so that the source-drain directions are opposite to each other, the forward directions of the parasitic diodes generated in the source-drain direction are opposite to each other. As a result, when the semiconductor switch is off, no current flows through the parasitic diode.

  As described above, according to the first aspect of the present invention, the order of the parasitic diodes generated in the source-drain direction is established by connecting the two semiconductor switches so that the source-drain directions are opposite to each other. The directions are opposite to each other. Thus, when the semiconductor switch is off, no current flows through the parasitic diode, so that a switching circuit that can use the semiconductor switch as the change-over switch can be obtained.

  According to the second aspect of the present invention, by using two semiconductor switches whose source-drain directions are connected in opposite directions as the change-over switch, it is possible to pass a current in both directions, and it is parasitic when off. Since no current flows through the diode, a switching circuit in which a semiconductor switch can be used as the changeover switch can be obtained.

  According to the third aspect of the present invention, if the control signal is level-shifted by the level shift circuit, the semiconductor switch in which a high voltage is applied to the source is turned on / off using the control signal output from the low-voltage logic circuit. Since there is no need to use an expensive photo MOS or the like, a switching circuit with reduced costs can be obtained.

  According to the fourth aspect of the invention, since the oscillation circuit and the assembled battery can be galvanically isolated by the drive capacitor, the oscillation circuit can use a low-voltage power supply different from the assembled battery as a power source. Therefore, the configuration is simple, and a low-cost and high-performance switching circuit can be obtained.

  According to the fifth aspect of the present invention, since a single oscillation circuit can be provided for a plurality of changeover switches, a switching circuit with a simple configuration and reduced costs can be obtained.

  According to the invention of claim 6, Pch. If the semiconductor switch is not used, an inexpensive Nch. Except for the semiconductor switch connected to the positive terminal of the unit cell on the highest voltage side that cannot be turned on. Therefore, a switching circuit with reduced cost can be obtained.

  According to the seventh aspect of the present invention, by connecting two semiconductor switches so that the source-drain directions are opposite to each other, the forward directions of the parasitic diodes generated in the source-drain direction are opposite to each other. Become. As a result, when the semiconductor switch is off, no current flows through the parasitic diode, so that a voltage measurement circuit that can use the semiconductor switch as the measurement switch can be obtained.

First Embodiment Hereinafter, a switching circuit and a voltage measuring circuit according to the present invention in a first embodiment will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of a voltage measuring circuit incorporating a flying capacitor circuit as a switching circuit of the present invention. As shown in the figure, the voltage measuring circuit includes a single capacitor C for an assembled battery in which a plurality of unit cells V _{1 to} V _n including two batteries are connected in series.

Further, the voltage measuring circuit includes a plurality of changeover switches S ₁₁ to S 1 for sequentially connecting each ends of the unit cells V ₁ ~V _n to both ends of the capacitor C _{(n + 1),} the changeover switch S _{11 to} S _{1 (n + 1)} and resistors R _{11 to} R _{1 (n + 1)} connected in series. The changeover switches S _{11 to} S ₁ (n + 1) are provided for (n + 1) _n unit cells V _{1 to} V _n . The above-described change-over switches S _{11 to} S _{1 (n + 1)} and the capacitor C constitute a switching circuit. Further, both ends of the capacitor C are connected to a measurement circuit 10 that measures the charging voltage of the capacitor C via measurement switches S ₂₁ and S ₂₂ .

The operation of the voltage measuring circuit incorporating the above-described flying capacitor circuit will be described below. First, a logic circuit (not shown) turns on the changeover switches S ₁₁ and S ₁₂ to connect both ends of the unit cell V ₁ to both ends of the capacitor C. Thereby, the charging voltage of the capacitor C becomes a value corresponding to the voltage across the unit cell V ₁ . Next, the logic circuit turns off the switches S ₁₁ and S ₁₂ to disconnect the unit cell V ₁ from the capacitor C, and turns on the measurement switches S ₂₁ and S ₂₂ to charge the capacitor C by the measurement circuit 10. Let the voltage be measured. By measuring the charging voltage of the capacitor C, the voltage across the unit cell V ₁ can be measured.

Further, the logic circuit turns on the changeover switches S ₁₂ and S ₁₃ to connect both ends of the unit cell V ₂ to both ends of the capacitor C. Hereinafter, the logic circuit performs on / off control of the changeover switches S _{11 to} S _{1 (n + 1)} and the measurement switches S ₂₁ and S ₂₂ as described above. As a result, both ends of the unit cells V _{1 to} V _n are sequentially connected to the capacitor C, and the charging voltage of the capacitor C having a value corresponding to the voltage across the unit cells V _{1 to} V _n by the connection is measured. Let me measure.

As apparent from these operations, the changeover switch S ₁₂ to S _1n connected between the unit cells V ₁ ~V _n is shared by two unit cells V ₁ ~V _n. To be specific, for example, the plus side of the unit cell V _1, and the negative side of the unit cell V ₂ which is connected to the positive side of the unit cell V ₁ was, via a common changeover switch S ₁₂ capacitor Connected to C. Therefore, the changeover switch S ₁₂ to S _1n in between the unit cells V ₁ ~V _n, so that the bidirectional current flows.

Next, the detailed configuration of the above-described changeover switches S _{11 to} S _{1 (n + 1)} will be described with reference to FIGS. Figure 2 is a circuit diagram showing an optional changeover switch S _m of the changeover switch _{S 12 ~S 1 (n + 1} ), FIG. 3 is connected to the positive side of the unit cell V ₁ to the highest voltage and a circuit diagram showing the changeover switch S ₁₁ are.

First, the changeover switches S _{12 to} S _{1 (n + 1)} will be described with reference to FIG. As shown in the figure, the changeover switch S _m, the source - as drain direction is opposite to each other, Nch as two semiconductor switches connected in series. Field effect transistors (= FETs) Q1 and Q2. For this reason, the forward directions of the parasitic diodes D1 and D2 generated between the source and drain of the FETs Q1 and Q2 are opposite to each other.

The gates of the FETs Q1 and Q2 described above are connected between the collector of the transistor Tr1 and the resistor Rb. The emitter of the transistor Tr1 is connected to the plus side of the unit cell V _m−1 via resistors Ra and R _{1 (m−1)} , and is connected to the base via a resistor Rc. On the other hand, the resistance Rb is connected to the negative side of the unit cell V _m.

  The base of the transistor Tr1 is connected to the collector of the transistor Tr2 via the resistors Rd and Re. The emitter of this transistor Tr2 is connected to the ground. On the other hand, the base is connected to a logic circuit (not shown) via a resistor Rf, and is connected to an emitter via a resistor Rg.

Thus, when a 5V control signal is supplied from the 5V logic circuit to the base of the transistor Tr2, the transistor Tr2 is turned on. When the transistor Tr2 is turned on, a current flows in the order of the resistors R _{1 (m−1)} , Ra, Rc, Rd, and Re. At this time, the voltage generated in the resistor Rc applies a bias between the emitter and base of the transistor Tr1, so that the transistor Tr1 is also turned on.

When the transistor Tr1 is turned on, the total value of the voltage across the unit cell _Vm and the unit cell _Vm-1 is divided by the resistors R1 _(m-1) , Ra and the resistor Rb at the gates of the FETs Q1 and Q2. A pressed voltage is applied. As a result, a bias voltage higher than that of the source is applied to the gates of the FETs Q1 and Q2, and the FETs Q1 and Q2 are turned on. As is apparent from the above, the resistors Ra to Rg and the transistors Tr1 and Tr2 function as a level shift circuit that shifts the level of the 5V control signal and applies it to the gates of the FETs Q1 and Q2.

Will now be described changeover switch S ₁₁ with reference to FIG. As shown in the figure, the changeover switch S _11, like the changeover switch _{S 12 ~S 1 (n + 1} ), the source - as drain direction is opposite each other, two series-connected Pch. It consists of FETs Q1 and Q2. For this reason, the forward directions of the parasitic diodes D1 and D2 generated between the source and drain of the FETs Q1 and Q2 are reversed.

The gates of the FETs Q1 and Q2 described above are connected between one end of the resistor Rh and one end of the resistor Ri. The other end of the resistor Rh is connected to the unit cell V ₁ through a resistor R ₁₁ . On the other hand, the other end of the resistor Ri is connected to the ground via the collector-emitter of the transistor Tr3. The base of the transistor Tr3 is connected to a logic circuit (not shown) through a resistor Rj and is connected to the emitter through a resistor Rk.

Thus, when a 5V control signal is supplied from the 5V logic circuit to the base of the transistor Tr3, the transistor Tr3 is turned on. When the transistor Tr3 is turned on, the gate of the FETQ1 and Q2, the positive side of the resistor voltage R ₁₁ of the unit cell V _1, and the resistor Rh, divided voltage is applied by the resistance Ri. Thereby, a bias voltage lower than the source is applied to the gates of the FETs Q1 and Q2, and the FETs Q1 and Q2 are turned on. As is apparent from the above, the resistors Rh to Rk and the transistor Tr3 function as a level shift circuit that shifts the level of the 5V control signal and applies it to the gates of the FETs Q1 and Q2.

According to the voltage measuring circuit incorporating the above flying capacitor circuit, the change-over switches S _{11 to} S _{1 (n + 1)} include two FETs Q 1 connected in series so that the source-drain directions are opposite to each other. Q2 is composed of each. Therefore, if an FET is used as the changeover switches S _{11 to} S _{1 (n + 1)} , a current can flow in both directions.

Moreover, by connecting the two FETs Q1 and Q2 so that the source-drain directions are opposite to each other, the forward directions of the parasitic diodes D1 and D2 generated in the source-drain direction are opposite to each other. As a result, when the FETs Q1 and Q2 are off, it is possible to prevent the current from flowing in the direction opposite to the current direction when the FET is on through the parasitic diodes D1 and D2. FETS _{11 to} S _{1 (n + 1)} which are semiconductor switches having excellent response speed can be used.

  Further, according to the voltage measurement circuit described above, the control signal is level-shifted by the level shift circuit and applied to the gates of the FETs Q1 and Q2. With this level shift circuit, it is possible to control on / off of FETs Q1 and Q2 whose sources are connected to a high voltage by using a control signal output from a 5V logic circuit, and there is no need to use an expensive photo MOS or the like. Cost reduction can be achieved.

Incidentally, since the FETQ1 and Q2 of the switch S ₁₁ is connected to the positive side of the unit cell V ₁ is the highest voltage, it is not possible to apply a higher source voltage to the gate, Nch. FET cannot be used. Therefore, as the voltage measuring circuit described above, the highest voltage side expensive Pch the FETQ1 and Q2 changeover switch S ₁₁ has connected to the positive side of the unit cell V ₁ in. The other change-over switches S _{12 to} S _{1 (n + 1)} are Nch. If the FET is used, the cost can be reduced.

Further, as described above, by using the FETQ1 and Q2 as measured switches S ₂₁ and S _22, it is possible to flow a bidirectional current to the measurement switch S ₂₁ and S _22. Moreover, as with the change-over switches S _{11 to} S _{1 (n + 1)} , parasitics generated in the source-drain direction by connecting the two FETs Q1 and Q2 so that the source-drain directions are opposite to each other. The forward directions of the diodes D1 and D2 are opposite to each other. As a result, even if the FETs Q1 and Q2 are off, it is possible to prevent current from flowing in the reverse direction.

In the embodiment described above, for the changeover switches S ₁₁ and S _{1 (n + 1),} the source - drain direction were using two FETQ1 and Q2 connected in series so as to be opposite to each other. However, the changeover switch S ₁₁ and _{S1 (n + 1),} since only flow unidirectional current, it is considered to use a unidirectional switch such as a transistor.

Second Embodiment Next, a switching circuit and a voltage measuring circuit according to the present invention in a second embodiment will be described with reference to the drawings. FIG. 4 is a circuit diagram showing an embodiment of a voltage measuring circuit incorporating a flying capacitor circuit as a switching circuit of the present invention. In the figure, the same parts as those in the first embodiment described above with reference to FIGS.

The difference from the first embodiment is the drive circuit of the changeover switches S _{11 to} S _{1 (n + 1)} . In the first embodiment, it had gained the gate voltage of FET Q1, Q2 constituting the selector switch _{S 11 ~S 1 (n + 1} ) the voltage of the assembled battery divides, in the second embodiment as follows It is composed. As shown in FIG. 4, the drive circuit of the FETs Q1 and Q2 includes a resistor Rdr (= resistive element) provided between the gate and source of the FETs Q1 and Q2, and capacitors Cr1 and Cr2 provided at both ends of the resistor Rdr. (= Capacitor for driving) and an oscillation circuit 20 that applies an AC voltage to both ends of the resistor Rdr via capacitors Cr1 and Cr2.

  Further, the drive circuit includes a drive switch SW provided between the oscillation circuit 20 and the capacitor Cr2, and a logic circuit 30 that outputs a control signal instructing on / off of the drive switch SW.

  The operation of the drive circuit of the voltage measuring apparatus having the above configuration will be described below. The oscillation circuit 20 described above constantly oscillates and outputs an alternating voltage. Now, when the logic circuit 30 outputs a control signal to the drive switch SW, the drive switch SW is turned on, and the AC voltage from the oscillation circuit 20 is applied to both ends of the resistor Rdr. As a result, a bias is applied between the source and gate of the FETs Q1 and Q2, and the two FETs Q1 and Q2 can be turned on. On the other hand, when the logic circuit 30 stops outputting the control signal to the drive switch SW, the drive switch SW is turned off and the AC voltage supply path is cut off, so that the FETs Q1 and Q2 are turned off.

  According to the above configuration, since the oscillation circuit 20 and the assembled battery can be galvanically insulated by the capacitors Cr1 and Cr2, the oscillation circuit 20 and the logic circuit 30 are different from the assembled battery, for example, a low voltage of 5V system. The source can be a power source. For this reason, for example, the drive switch SW provided between the oscillation circuit 20 and the capacitor Cr2 does not require a high breakdown voltage, and a safe device can be obtained at low cost.

Further, by providing a drive switch SW for turning on and off the AC voltage applied to the resistor Rdr and a logic circuit 30 for controlling the drive switch SW, a plurality of changeover switches S _{11 to} S _{1 (n + 1)} are provided. On the other hand, one oscillation circuit 20 can be provided, and there is no need to provide each oscillation switch 20 for each changeover switch S _{11 to} S _{1 (n + 1)} . For this reason, a structure becomes simple and it can aim at cost reduction.

  In the second embodiment, a capacitor may be provided in parallel with the resistor Rdr. With such a configuration, the resistor Rdr and the capacitor function as a filter, and it is possible to prevent the FETs Q1 and Q2 from being inadvertently turned on due to noise or the like.

It is a circuit diagram which shows the voltage measurement circuit incorporating the flying capacitor circuit as a switching circuit of this invention in 1st Example. FIG. 2 is a detailed circuit diagram showing changeover switches S _{12 to} S _{1 (n + 1)} constituting the voltage measurement circuit of FIG. Is a detailed circuit diagram of the selector switch S ₁₁ constituting the voltage measurement circuit of FIG. It is a circuit diagram which shows the voltage measurement circuit incorporating the flying capacitor circuit as a switching circuit of this invention in 2nd Example. It is a circuit diagram which shows an example of the conventional flying capacitor circuit. It is a circuit diagram which shows an example of the conventional flying capacitor circuit.

Explanation of symbols

C capacitor Cr1, Cr2 drive capacitor _{S 11 ~S 1 (n + 1} ) change-over switch S _21, S ₂₂ Measurement switch S ₂₁₁ to S _21n measuring switch S ₂₂₁ to S _22n measurement switch SW Drive switch V ₁ ~V _n Unit cell Q1, Q2 Field effect transistor (semiconductor switch)
Rdr resistance element 20 oscillation circuit 30 logic circuit

Claims (7)

In a switching circuit comprising a capacitor and a plurality of changeover switches for sequentially connecting both ends of each unit cell of an assembled battery configured by connecting a plurality of unit cells made of a battery in series,
The switching switch includes two semiconductor switches connected in series so that the source-drain directions are opposite to each other. The switching circuit according to claim 1,
The negative side of one unit cell and the positive side of the second unit cell connected to the negative side of the unit cell are connected to the capacitor via the common changeover switch. Switching circuit. The switching circuit according to claim 1 or 2,
A logic circuit that outputs a control signal instructing on / off of the semiconductor switch;
A switching circuit further comprising: a level shift circuit that shifts the level of the control signal and outputs the level to the gate of the semiconductor switch. The switching circuit according to claim 1 or 2,
A resistance element provided between a source and a gate of the semiconductor switch;
A drive capacitor connected to both ends of the resistance element;
A switching circuit comprising: an oscillation circuit that applies an AC voltage to both ends of the resistance element via the drive capacitor. A switching circuit according to claim 4, wherein
A drive switch provided between the oscillation circuit and the drive capacitor;
A switching circuit comprising: a logic circuit that outputs a control signal instructing on / off of the drive switch. A switching circuit according to any one of claims 1 to 5,
Of the changeover switches, the semiconductor switch connected to the positive side of the unit cell on the highest voltage side is Pch. The other semiconductor switches are Nch. A switching circuit characterized by A switching circuit according to any one of claims 1 to 6,
Voltage measuring means for measuring the voltage across the capacitor;
A measuring switch provided between both ends of the capacitor and the voltage measuring means;
The voltage measurement circuit according to claim 1, wherein the measurement switch includes two semiconductor switches connected in series so that the source-drain directions are opposite to each other.

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