JP2006020382A - Dc voltage supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the cell voltage of each lithium ion battery appropriately through simple circuitry without relying upon a software. <P>SOLUTION: The DC voltage supply comprises circuits provided for individual batteries connected in series and bypassing the charging current when the cell voltage of the battery is not lower than a reference voltage, a means for supplying the charging current to the battery and stabilizing the series voltage of the battery to the reference voltage, and a means for generating the reference voltage by dividing the stabilized voltage level at a ratio of n:1 wherein the bypass circuit detects the difference between the cell voltage of the battery and the reference voltage and then bypasses the charging current of the battery based on that difference. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a DC voltage supply apparatus that connects batteries in series and supplies a desired DC voltage.

  Conventionally, a sealed lead-acid battery is mainly used as a backup for a power supply system that supplies power to a load device such as a communication device. This sealed lead-acid battery has been widely used for communication equipment, in addition to being inexpensive, it can be maintained at a constant voltage so that it can be maintained and recharged after a power failure. This is because there was a merit in configuration.

  On the other hand, in recent years, there is a demand for downsizing the power supply system and shortening the backup time. However, in the conventional sealed lead-acid battery, the current value during current discharge is limited, so the size of the battery is reduced. There were limits. Moreover, in order to reduce the size of the sealed lead-acid battery, it is effective to apply a secondary battery that has a high energy density and can withstand a large current discharge. And has the characteristic of being suitable for constant voltage charging like a sealed lead-acid battery.

  Therefore, a small-sized and high-capacity DC voltage supply device has been realized using a lithium ion battery. However, since the lithium ion batteries used in the DC voltage supply device have different potentials, the potentials of the bypass circuits for stabilizing the voltage are different from each other.

  In addition, since the bypass circuit operates using the full charge voltage of each lithium ion battery as a reference voltage, if the full charge voltage of the lithium ion battery is fixed, the reference voltage can be generated in each bypass circuit. However, if it is desired to vary the full charge voltage of the lithium ion battery, an isolated reference voltage must be generated for each bypass circuit.

  Furthermore, in a system equipped with a DC voltage stabilization circuit that stabilizes the voltage value of the lithium ion batteries connected in series, the cell voltage at the time of full charge of the lithium ion batteries connected in series is the DC voltage stabilization circuit. Same as output voltage. Therefore, the cell voltage of each lithium ion battery is controlled to a voltage value obtained by dividing the output voltage of the DC voltage stabilizing circuit by the number of lithium ion batteries (number of cells) so that the charging voltage of each lithium ion battery does not vary. There is a need to. Similarly, each bypass circuit needs to be supplied with a reference voltage corresponding to a voltage value obtained by dividing the output voltage of the DC stabilizing circuit by the number of cells.

  In response to such a problem, a technique as shown in FIG. 4 has been proposed (see, for example, Patent Document 1). In this technology, voltage detectors 2a, 2b, and 2c including isolation amplifiers that detect cell voltages of the lithium ion batteries 3a, 3b, and 3c, and charging current values flowing through the lithium ion batteries 3a, 3b, and 3c are calculated. It includes current detectors 16a, 16b, 16c composed of hall elements to detect, etc., and each detected cell voltage and charging current value is taken into a microprocessor and required for each lithium ion battery 3a, 3b, 3c. Calculate the appropriate bypass current.

The calculation result in the microprocessor is supplied to the drive circuit via a photocoupler or the like because the cell voltages of the lithium ion batteries 3a, 3b, and 3c are different. Thereby, the cell voltage of each lithium ion battery 3a, 3b, 3c is controlled by controlling the charging current of each lithium ion battery 3a, 3b, 3c.
JP-A-9-182307

  However, in the above-described technology, although the cell voltage of each lithium ion battery can be appropriately controlled, the cell voltage and charging current of the lithium ion battery are individually detected and arithmetically controlled by the microprocessor. This complicates the circuit configuration. In addition, there is a problem that new software corresponding to such control is required.

  Therefore, the present invention has been made in view of the above-described problems, and provides a DC voltage supply device that can appropriately control the cell voltage of each lithium ion battery with a simple circuit configuration that does not depend on software. With the goal.

  The invention according to claim 1 is a direct-current voltage supply device for supplying a series voltage of n (n is an integer of 2 or more) batteries connected in series to the outside, and for each of the batteries connected in series A bypass circuit that bypasses a charging current when the cell voltage of the battery is equal to or higher than a reference voltage, and supplies a charging current to the n batteries (n is an integer of 2 or more) connected in series, Voltage stabilizing means for stabilizing the series voltage of the batteries connected in series to a predetermined voltage value, and a reference voltage generating unit that divides the stabilized voltage value by a ratio of n: 1 to generate a reference voltage Differential voltage detecting means for detecting a difference between the cell voltage of the battery and the reference voltage, and bypass means for bypassing the charging current of the battery based on a detection value of the differential voltage detecting means. , Characterized by having It proposes a flow voltage supply.

  According to the present invention, the differential voltage between the cell voltage of each battery and the reference voltage generated in the reference voltage generation unit is detected by the operation of the bypass circuit, and when the cell voltage of the battery is equal to or higher than the reference voltage, the charging current By maintaining the constant voltage by the reference voltage, an overvoltage state is avoided.

  According to a second aspect of the present invention, there is provided a DC voltage supply device according to the first aspect, wherein the DC voltage supply device is connected in series to the charging current supply path of the battery, and switching means for opening and closing the charging current supply path; A DC voltage supply device comprising overvoltage control means for comparing the voltage with a predetermined voltage value and controlling the switching means to open when there is a battery whose cell voltage is higher than the voltage value is suggesting.

  According to the present invention, when the bypass voltage is operated due to the operation of the overvoltage control means, there is a battery whose cell voltage is higher than the predetermined voltage value among the batteries connected in series for some reason. Then, the switching means is operated to open the charging current supply path. As a result, when there is a failed battery due to some factor, it is possible to detect the failed battery and prevent the charging current from being supplied to the battery with a simple configuration.

  The invention according to claim 3 is the DC voltage supply device according to claim 2, wherein the cell voltage of each battery is compared with a predetermined voltage value, and the switching is performed when the cell voltage is lower than the voltage value. A DC voltage supply device is provided, characterized in that it is provided with overdischarge control means for controlling the means to open.

  According to the present invention, when there is a battery in which the cell voltage of the battery is lower than the predetermined voltage value due to some factor due to the operation of the overdischarge control means, the switching means is operated to open the charging current supply path. As a result, when there is a failed battery due to some factor, it is possible to detect the failed battery and to prevent the charging current from being supplied to all the batteries including the battery with a simple configuration.

  According to the present invention, there is an effect that the cell voltage of the lithium ion battery can be appropriately controlled by using the voltage corresponding to 1 / n of the output voltage of the DC voltage stabilizing circuit as the reference voltage without using software. . This reference voltage can be easily generated by impedance voltage division and is linked to the output voltage of the DC voltage stabilization circuit. Therefore, if you want to change the charging voltage of the lithium ion battery, each lithium ion connected in series This can be easily realized by changing only the output voltage of the DC voltage stabilizing circuit without manipulating the reference voltage of the battery.

  Hereinafter, a DC voltage supply apparatus according to an embodiment of the present invention will be described in detail with reference to FIGS.

  As shown in FIG. 1, the DC voltage supply apparatus according to the present invention includes resistors 1a, 1b, and 1c, voltage detectors 2a, 2b, and 2c, and lithium ion batteries 3a and 3b that constitute a reference voltage generator 1. 3c, a bypass circuit 4, a differential amplifier 5 provided in the bypass circuit 4, a switch 6, a current limiting circuit 7, and a DC voltage stabilizing circuit 20.

  The reference voltage generation unit 1 arranges resistors 1a, 1b, and 1c in series with the DC voltage stabilizing circuit 20, and generates a divided value thereof, that is, a voltage across the resistor 1a as a reference voltage. The ratio of the resistance value of the resistor 1a to the combined resistance value of the resistors 1b and 1c is a value corresponding to the number of cells of the lithium ion batteries 3a, 3b, and 3c connected in series.

  In addition, by using at least one of the resistors 1a, 1b, and 1c as a variable resistor, it absorbs variations caused by environmental conditions such as individual variations, temperature, and humidity, and generates an optimum reference voltage. You can also

  The voltage detectors 2a, 2b, and 2c supply the reference voltage generated in the reference voltage generation unit 1 to the differential amplifier 5 in the bypass circuit 4. Since the cell voltages of the lithium ion batteries 3a, 3b, and 3c have different potentials, isolation amplifiers or the like are used for the voltage detectors 2a, 2b, and 2c.

  Lithium-ion batteries have the advantages of high voltage, high energy density, no memory effect, long cycle life, rapid discharge, good storage characteristics, and high output. It is used not only for mobile phones but also as a power supply source for electric vehicles.

  The bypass circuit 4 is provided in parallel to each of the lithium ion batteries 3a, 3b, and 3c, detects the cell voltage of each of the lithium ion batteries 3a, 3b, and 3c, and supplies the reference voltage supplied from the reference voltage generation unit 1 And the drive circuit operates the FET or the like in the unsaturated region and bypasses the charging current based on the difference value.

  Specifically, when the detected voltage value is higher than the reference voltage, the drive circuit is activated to bypass the charging current, and when the detected voltage value is lower than the reference voltage, the drive circuit is not activated, Each battery prompts charging by the charging current supplied from the DC voltage stabilizing circuit 20.

  The switch 6 is opened when at least one of the lithium ion batteries 3a, 3b, 3c detects an overvoltage state or an overdischarge state, and charges the lithium ion batteries 3a, 3b, 3c connected in series. Switching means for disconnecting from the supply path.

  Specifically, the DC voltage supply apparatus according to the present invention includes an abnormality detection unit as shown in FIG. 2, and the abnormality detection unit includes an overvoltage detection unit 8, an overdischarge detection unit 9, and a photocoupler 10. It consists of and. When the overvoltage detection unit 8 or the overdischarge detection unit 9 detects that the at least one lithium ion battery 3a, 3b, 3c is in an overvoltage state or an overdischarge state, the abnormality detection unit receives the information from the photocoupler 10. Is transmitted as an optical signal, and the opening and closing of the switch 6 is controlled. The reason why the optical signal is used for transmitting the detection signal is that the potential of the cell voltage in each of the lithium ion batteries 3a, 3b, 3c is different.

  Here, as shown in FIG. 3, the overvoltage detection unit 8 or the overdischarge detection unit 9 includes resistors 11a, 11b, and 11c, a constant voltage diode 12, and a comparator 13, and each lithium ion battery. The divided voltage values of the cell voltages 3a, 3b, and 3c are compared with a predetermined voltage value generated from the resistor 11c and the constant voltage diode 12, and the divided voltage value of the cell voltage exceeds the predetermined voltage value. If it is, it is determined that an overvoltage state is present.

  On the other hand, when the divided voltage value of the cell voltage obtained by the resistors 11a and 11b exceeds the predetermined voltage value, it is determined that the battery is overdischarged, and a signal corresponding to this is supplied to the photocoupler 10. . As shown in FIG. 3, the photocoupler 10 includes an LED 14 and phototransistors 15a and 15b. The photocoupler 10 converts an optical signal into an electrical signal, and drives the relay, for example, to control the opening and closing of the switch 6 using the electrical signal. .

  The voltage value that operates as an overvoltage is, for example, 4.5 V, and the voltage value that operates as an overdischarge is, for example, 3.0 V. Moreover, as a reference voltage value, 4.0V etc. are mentioned, for example. Since these voltage values vary depending on the type of lithium ion battery to be used, an appropriate value corresponding to the lithium ion battery to be used may be set. The return operation when the switch 6 is operated is, for example, manual return in the case of overvoltage, and automatic return in the case of overdischarge.

  Since the overvoltage detector 8 or the overdischarge detector 9 can monitor the cell voltage of each lithium ion battery 3a, 3b, 3c, the cell voltage exceeds the safe range of the lithium ion batteries 3a, 3b, 3c during charging. In such a case, by detecting this and opening the switch 6, it is possible to ensure the safety of the lithium ion batteries 3a, 3b, 3c.

  The current limiting circuit 7 monitors the charging current flowing through the lithium ion batteries 3a, 3b, and 3c connected in series, and when the current value exceeds a predetermined threshold value, the current is supplied to the battery by a certain amount. Limit to. The DC voltage stabilizing circuit 20 uses an AC-DC converter or a DC-DC converter that outputs DC as a power source, stabilizes the output voltage to the load device, and connects the lithium ion batteries 3a, 3b, 3c connected in series. In contrast, a charging current is supplied.

Next, a method for controlling the cell voltage of each lithium ion battery 3a, 3b, 3c in the DC voltage supply apparatus of the present invention will be described.
In the DC voltage supply apparatus of the present invention, the number of lithium ion batteries 3a, 3b, 3c connected in series and the full charge voltage or the current capacity necessary for charging all the lithium ion batteries 3a, 3b, 3c are set. As a result, the specification of the DC voltage stabilizing circuit 20 is determined. For example, when the number of lithium ion batteries 3a, 3b, and 3c is set to 3 and the full charge voltage is set to 4.0V, the output voltage of the DC voltage stabilizing circuit 20 is determined to be 12V.

  On the other hand, in this case, since the number of lithium ion batteries 3a, 3b, and 3c is 3, the ratio of the resistance values of the resistors 1a, 1b, and 1c constituting the reference voltage generating unit 1 in FIG. Thus, reference voltage = full charge voltage. At this time, the resistance constituting the reference voltage generation unit 1 may be two, and the ratio of the resistance values may be 1: 2. Furthermore, when high-precision control is performed without using high-precision resistors and resistors with excellent temperature characteristics, one of these resistors is configured with a variable resistor, and the divided voltage value is monitored. However, the constant can be adjusted.

  In the case of this example, the reference voltage of 4.0 V is input to the differential amplifier 5 in the bypass circuit 4 via the voltage detectors 2a, 2b, and 2c. On the other hand, the cell voltage of each lithium ion battery 3a, 3b, 3c is also input to the differential amplifier 5, and the difference value between the two is detected.

  The detection value is supplied to the drive circuit, and when the cell voltage of each lithium ion battery 3a, 3b, 3c is higher than the reference voltage, the drive circuit operates the transistor in the unsaturated region to bypass the charging current, When the cell voltage of the ion batteries 3a, 3b, and 3c is lower than the reference voltage, charging of the lithium ion batteries 3a, 3b, and 3c is prompted with the transistor turned off. Therefore, the cell voltage of each lithium ion battery 3a, 3b, 3c can be optimally controlled.

As described above, according to this embodiment, the reference voltage for controlling the cell voltage of each of the lithium ion batteries 3a, 3b, and 3c is generated by resistance voltage division, so that accurate control can be performed with a simple circuit configuration. .
Further, the overvoltage detection unit 8 or the overdischarge detection unit 9 individually monitors the cell voltage of each lithium ion battery 3a, 3b, 3c, and the cell voltage of each lithium ion battery 3a, 3b, 3c during charging is a predetermined value. When the range is exceeded, an abnormality is detected and the switch 6 is opened, so that the safety of each of the lithium ion batteries 3a, 3b, 3c can be ensured.

  The embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to these embodiments, and includes design changes and the like without departing from the scope of the present invention. . For example, in the present embodiment, an example in which the reference voltage is generated by the voltage dividing circuit including the resistor has been described. However, the present invention is not limited thereto, and any element that can generate a divided voltage may be used. In addition, the reference voltage generation method in this embodiment can also be used for a charger.

It is a block diagram of the present invention. It is a block diagram of the abnormality detection part of this invention. It is a block diagram of the overvoltage detection part and overdischarge detection part of this invention. It is a block diagram of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reference voltage generation part, 1a, 1b, 1c, 11a, 11b, 11c ... Resistor, 2a, 2b, 2c ... Voltage detector, 3a, 3b, 3c ... Lithium ion battery, DESCRIPTION OF SYMBOLS 4 ... Bypass circuit, 5 ... Differential amplifier, 6 ... Switch, 7 ... Current limiting circuit, 8 ... Overvoltage detection part, 9 ... Overdischarge detection part, 10 ... Photocoupler, 12 ... Constant voltage diode, 13 ... Comparator, 14 ... LED, 15a, 15b ... Phototransistor, 16a, 16b, 16c ... Current detector, 20 ... DC voltage Ballast circuit

Claims (3)

A DC voltage supply device for supplying a series voltage of n batteries (n is an integer of 2 or more) connected in series to the outside,
A bypass circuit that is provided for each battery connected in series and bypasses a charging current when the cell voltage of the battery is equal to or higher than a reference voltage;
Voltage stabilization means for supplying a charging current to the n (n is an integer of 2 or more) batteries connected in series, and stabilizing the series voltage of the batteries connected in series to a reference voltage;
A reference voltage generator that divides the stabilized voltage value at a ratio of n: 1 and generates a reference voltage;
Differential voltage detection means for detecting a difference between the cell voltage of the battery and the reference voltage by the bypass circuit;
Bypass means for bypassing the charging current of the battery based on the detection value of the differential voltage detection means;
A direct-current voltage supply device comprising: Switching means connected in series to the charging current supply path of the battery and opening and closing the charging current supply path;
An overvoltage control means for comparing the cell voltage of each battery with a predetermined voltage value and controlling the switching means to open when there is a battery whose cell voltage is higher than the voltage value is provided. Item 4. The DC voltage supply device according to Item 1. 3. An overdischarge control means for comparing the cell voltage of each battery with a predetermined voltage value and controlling the switching means to open when the cell voltage is lower than the voltage value. DC voltage supply device described in 1.

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