JP2010200580A - Secondary battery power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery power supply having a backflow prevention circuit capable of manufacturing it with a low power loss; requiring no expensive components such as a comparator, a microcomputer, an IC, and the like, and achieving it at low cost and with less components. <P>SOLUTION: The secondary battery power supply includes a set of secondary batteries 1 constituted by connecting two secondary batteries 1a, 1b in parallel, and a backflow prevention circuit 4. The backflow prevention circuit 4 is interposed in between a charger 2 and the set of the secondary batteries 1 and has a PNP transistors 41a, 41b interposed between the respective positive terminals 6a, 6b for charging the secondary batteries 1a, 1b and a connecting terminal 8a to the positive terminal of the charger 2. The base currents in the PNP transistors 41a, 41b are regulated by the resistance value of a base-current regulating resistor 43 arranged between the bases of the PNP transistors 41a, 41b and negative terminals 7a, 7b in the set of the secondary batteries 1 so as to prevent the charging current from exceeding a rated current value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a secondary battery power supply device configured by connecting a plurality of secondary batteries, or secondary battery blocks, or secondary battery packs in parallel, and in particular, the charging current has a rated current value due to backflow during charging. The present invention relates to a secondary battery power supply device having a function of controlling so as not to exceed.

  When connecting multiple rechargeable batteries or rechargeable battery packs in series and charging them simultaneously with a single charger, there is a difference in charge rate between the rechargeable batteries or rechargeable battery packs when connected to the charger. The rechargeable battery or rechargeable battery pack with the highest charging rate will be fully charged first, and if recharging continues, the rechargeable battery or rechargeable battery pack that has been fully charged may fall into overcharge. is there. Therefore, serial charging is possible when the rated capacity of the secondary battery or the secondary battery pack is equal and the remaining amount at the start of charging is complete. Further, in order to prevent overcharging, it is necessary to provide an advanced protection circuit that monitors and controls the voltage of each secondary battery or secondary battery pack.

  Further, when a plurality of secondary battery packs are charged in series, if one secondary battery pack is removed, the current path is cut off, so that the charging current to the remaining secondary battery packs is also cut off. In order to prevent this, a detection circuit for detecting the presence or absence of the secondary battery pack and an advanced switching circuit for connecting between the terminals where the secondary battery pack is not inserted are required.

  On the other hand, when charging by connecting a plurality of secondary battery packs in parallel, even if the charging rate and rated capacity differ between the secondary battery packs when connected to the charger, It will not be charged beyond the rated charging voltage of the secondary battery pack, and even if one of the secondary battery packs is removed during charging, charging to the other secondary battery pack will not stop. Therefore, the configuration of the charging circuit can be simplified.

  However, since secondary batteries with different charging rates have different voltages, when secondary batteries with different voltages are connected in parallel, the voltage tends to be equalized, so that a secondary battery with a high voltage is changed to a secondary battery with a low voltage. Charging current will flow. For example, since the voltage of a lithium ion secondary battery is generally used in the range of about 3.0 V to 4.2 V per cell, the secondary battery with a voltage of 4.2 V in a fully charged state, When batteries having a voltage of 3.0 V are connected in parallel, and each internal resistance is 50 mΩ, a current of (4.2 V−3.0 V) / (0.05Ω × 2) = 12 A, It flows from a secondary battery having a high voltage to a secondary battery having a low voltage. When the value exceeds the rating of the secondary battery, both secondary batteries may be adversely affected.

  For this reason, when a plurality of secondary batteries are connected in parallel and charged, a means for inserting a backflow prevention circuit using a diode as a backflow protection element between the charger and the secondary battery is generally known. FIG. 3 is a circuit diagram showing an example of a secondary battery power supply device using a conventional backflow prevention circuit, and charging terminals 6a and 6b and chargers for the secondary batteries 1a and 1b connected in parallel. Diodes 31a and 31b are connected to the connection terminal 8a to 2 to prevent backflow. In addition, although not shown in figure, the positive electrode terminal for discharge of the secondary batteries 1a and 1b is provided separately.

  However, in order to pass a forward current through the diode, a forward voltage of Vf = 0.6 V is required, and power loss occurs in the diode. Therefore, if a large current is passed, there is a concern that heat corresponding to the generated current is generated and the secondary battery is deteriorated.

  In order to prevent this, in Patent Document 1, in a device that uses secondary batteries connected in parallel, a switching element using a field effect transistor (FET) is installed in parallel with a diode for preventing backflow, and a reverse bias voltage is detected. A means has been proposed for detecting a reverse flow using a comparison circuit and reducing the loss generated in the diode by turning on the switch element when there is no reverse flow.

JP-A-9-140065

  However, in the means described in Patent Document 1, an expensive component such as a reverse bias detection circuit is used in addition to the diode that is a reverse current protection element, and the number of mounted components increases greatly. There is a problem to say. In addition, since diodes and FETs cannot directly limit current, if some secondary batteries are removed while simultaneously charging multiple secondary batteries in parallel, the remaining secondary batteries Depending on the setting of the output current of the charger, the secondary battery may be charged with a current value exceeding the rating of the secondary battery.

  Therefore, the object of the present invention is to provide a backflow prevention circuit that is less loss than a backflow prevention circuit using a conventional diode, does not require expensive parts such as a comparison circuit, a microcomputer, and an IC, and that is inexpensive and can be realized with few parts It is in providing the secondary battery power supply device provided.

  In order to solve the above-described problems, a secondary battery power supply apparatus according to the present invention includes a secondary battery group configured by connecting a plurality of secondary battery constituents each including at least one secondary battery in parallel and a backflow prevention. A secondary battery power supply device including a circuit, wherein the backflow prevention circuit is inserted between a charger for charging the secondary battery group and the secondary battery group, and It has a PNP transistor inserted between the positive electrode terminal and the positive electrode terminal of the charger.

  Here, the backflow prevention circuit limits the base current of the PNP transistor so that the charging current supplied to the secondary battery constituent exceeds the rated current value of the secondary battery and the secondary battery constituent. For example, the base current of the PNP transistor may be limited by the resistance value of a resistor inserted between the base of the PNP transistor and the negative terminal of the secondary battery group.

  In addition, the backflow prevention circuit preferably has no active circuit components such as a comparison circuit, a microcomputer, and an IC other than the PNP transistor.

  In the secondary battery power supply device of the present invention, the backflow prevention circuit prevents the backflow current to flow to the charger side when the voltage of the secondary battery is lower than the voltage of the charger, and the voltage between the secondary batteries. When there is a difference, it is possible to prevent a reverse flow in which a charging current flows from a secondary battery having a high voltage to a secondary battery having a low voltage. When charging, the voltage drop due to the transistor used in the present invention is lower than the forward voltage of the diode used in the conventional backflow prevention circuit, so that loss and heat generation in the backflow prevention circuit can be reduced. it can.

  Further, in the backflow prevention circuit used in the present invention, the charging current supplied to the secondary battery can be controlled by the current amplification function of the transistor, so that some of the batteries have been removed during the charging. However, it is possible to prevent the remaining secondary battery connected to the charger from being charged with a large current exceeding the rated value.

  In addition, since the backflow prevention circuit used in the present invention does not require a comparison circuit like the backflow prevention circuit of Patent Document 1, the backflow prevention circuit can be easily reduced in size and cost.

  As described above, according to the present invention, the backflow prevention can be realized with less loss and less cost than a conventional backflow prevention circuit using a diode, without requiring expensive parts such as a comparison circuit, a microcomputer, and an IC. A secondary battery power supply device having a circuit is obtained.

The circuit diagram which shows 1st embodiment of the secondary battery power supply device by this invention. The circuit diagram which shows 2nd embodiment of the secondary battery power supply device by this invention. The circuit diagram which shows an example of the secondary battery power supply device using the conventional backflow prevention circuit.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit diagram showing a first embodiment of a secondary battery power supply device according to the present invention. In FIG. 1, a secondary battery group 1 configured by connecting two secondary batteries 1 a and 1 b in parallel and a backflow prevention circuit 4 are provided. The backflow prevention circuit 4 is used for charging the secondary battery group 1. A connecting terminal 8a that is inserted between the charger 2 and the secondary battery group 1 and is connected to the positive terminals 6a and 6b for charging the secondary batteries 1a and 1b and the positive terminal of the charger 2. PNP transistors 41a and 41b inserted between the two. In addition, although not shown in figure, the positive electrode terminal for discharge of the secondary batteries 1a and 1b is provided separately.

  Further, in the secondary battery power supply device of the present embodiment, the backflow prevention circuit 4 limits the base currents of the PNP transistors 41a and 41b so that the charging current supplied to the secondary batteries 1a and 1b can be reduced. More specifically, the base current limiting resistor 43 inserted between the bases of the PNP transistors 41a and 41b and the negative terminals 7a and 7b of the secondary battery group 1 is controlled. The base current of the PNP transistors 41a and 41b is limited by the resistance value.

  Next, detailed operation of the present embodiment will be described. In FIG. 1, the backflow prevention circuit 4 connects PNP transistors 41a and 41b as backflow prevention elements to the charging path. Even if the positive terminals 6a and 6b and the negative terminals 7a and 7b of the secondary batteries 1a and 1b are connected to the backflow prevention circuit 4, if the charger 2 is not connected, the emitter-base of the PNP transistors 41a and 41b Since no current is supplied between them, the PNP transistors 41a and 41b of the backflow prevention circuit 4 are in an OFF state, and even if there is a voltage difference between the secondary batteries 1a and 1b, the secondary batteries 1a and 1b are charged. It is possible to prevent discharge.

  When the charger 2 is connected to the backflow prevention circuit 4 with the secondary batteries 1a and 1b connected, a potential difference is generated between the emitter and base of the PNP transistor by the voltage dividing resistor 42, and current is supplied from the emitter to the base. Therefore, current can flow from the connection terminal 8a to the positive terminals 6a and 6b between the emitters and collectors of the PNP transistors 41a and 41b, respectively. However, due to the characteristics of the PNP transistor, current cannot flow from the collector to the emitter, that is, from the positive terminals 6a and 6b of the secondary battery to the positive terminal of the charger. Therefore, even if there is a voltage difference between the two secondary batteries 1a and 1b, it is possible to prevent a reverse flow in which a charging current flows from a secondary battery having a high voltage to a low secondary battery or a reverse flow from the secondary battery to the charger. .

  The voltage of the secondary battery 1a is E1a, and the voltage of the secondary battery 1b is E1b. When two secondary batteries are connected to the backflow prevention circuit 4 and the charger 2 is connected, when E1a> E1b, charging is performed only to the secondary battery 1b having the lower voltage. Thereafter, when the voltage of the secondary battery 1b rises as charging progresses and E1a = E1b, both the secondary batteries are charged. That is, there is a characteristic that the voltages of a plurality of battery packs can be prepared by charging using this circuit.

  The current value supplied to the secondary battery can be limited by the base current limiting resistor 43. Since the current value Ib supplied from the emitters of the PNP transistors 41a and 41b to the base is determined by the value of the base current limiting resistor 43, the current value flowing from the emitter to the collector, that is, the current value charged in the secondary battery is , Ib and the DC current gain hFE of the transistor is the maximum value. Therefore, even if one of the secondary batteries is removed during charging, it is possible to prevent a current exceeding the rated value from flowing through the remaining secondary batteries connected to the charger.

  Next, the power loss generated in the backflow prevention circuit 4 used in this embodiment and the conventional backflow prevention circuit 3 shown in FIG. 3 is compared.

Assuming that the charging current is Ichg = 3A, when a conventional diode is used, the forward voltage Vf of the diode is Vf = 0.6 V, so that the power loss of one diode is
Pd1 = 3A × 0.6V = 1.8W
It becomes.

On the other hand, when a PNP transistor is used as in the present embodiment, the consumed voltage between the emitter and the collector is VEC = 0.1 V, so the power loss between the emitter and the collector is
P1 = 3A × 0.1V = 0.3W
It becomes. If the amplification factor of the power transistor PNP transistor is hFE = 30, the base current required for 3A energization is Ib = 3A / hFE = 0.1A, and the forward voltage of the PN junction diode between the emitter and base is Since VEB = 0.6, the loss due to the base current is
P2 = 0.1A × 0.6V = 0.06W
It becomes. Therefore, the power loss of one whole PNP transistor is
Pd2 = P1 + P2 = 0.36W
Thus, the power loss Pd1 when the above diode is used can be reduced to one fifth.

  FIG. 2 is a circuit diagram showing a second embodiment of the secondary battery power supply device according to the present invention. In FIG. 2, a secondary battery group 11 configured by connecting N secondary batteries 1 a 1 to 1 a N in parallel and a backflow prevention circuit 5 are provided, and the backflow prevention circuit 5 charges the secondary battery group 11. Connection terminal which is inserted between the battery charger 12 and the secondary battery group 11 and is connected to the positive terminals 6a1 to 6aN for charging the secondary batteries 1a1 to 1aN and the positive terminal of the charger 12. And N PNP transistors 41a1 to 41aN inserted between them.

  Also in the secondary battery power supply device of the present embodiment, the resistance value of the base current limiting resistor 43 inserted between the bases of the PNP transistors 41a1 to 41aN and the negative terminals 7a1 to 7aN of the secondary battery group 11 depends on the resistance value. The base current of the PNP transistors 41a1 to 41aN is limited.

  Here, N is an integer of 3 or more, and can be selected according to the required battery capacity. The operation of the secondary battery power supply device of the present embodiment is also the same as that of the first embodiment, and even if there is a voltage difference between any of the secondary batteries, It is possible to prevent a reverse flow in which the charging current flows to the battery and a reverse flow from the secondary battery to the charger.

  As described above, according to the present invention, it is possible to obtain a secondary battery power supply device including a backflow prevention circuit with a lower loss than the conventional one. Further, the backflow prevention circuit has an active circuit component other than the PNP transistor as described above. By using a circuit that does not, it can be realized at a lower cost and with fewer parts.

  In the above embodiment, each of the secondary battery components is composed of one secondary battery, which is connected in parallel to form a secondary battery group, but a plurality of secondary batteries are connected. The secondary battery block configured as a secondary battery structure may be connected in parallel to form a secondary battery group, and the secondary battery pack may be used as one unit. The secondary battery group may be configured by being connected to the. Further, not only one PNP transistor is used for each secondary battery structure, but also a backflow prevention circuit may be configured by PNP transistors connected in multiple stages. It is also possible to replace the current limiting resistor with a component having a constant current circuit function.

DESCRIPTION OF SYMBOLS 1,11 Secondary battery group 1a, 1b, 1a1-1aN Secondary battery 2, 12 Charger 3, 4, 5 Backflow prevention circuit
6a, 6b, 6a1-6aN Positive terminal 7a, 7b, 7a1-7aN Negative terminal 8a, 8b, 18a, 18b Connection terminal 31a, 31b Diode 41a, 41b, 41a1-41aN PNP transistor 42 Voltage dividing resistor 43 Base current limiting resistor

Claims (4)

A secondary battery power supply device comprising a secondary battery group configured by connecting a plurality of secondary battery constituents composed of at least one secondary battery in parallel and a backflow prevention circuit,
The backflow prevention circuit is inserted between a charger for charging the secondary battery group and the secondary battery group, and between the positive terminal of the secondary battery component and the positive terminal of the charger. A secondary battery power supply device comprising an inserted PNP transistor.   The backflow prevention circuit limits the base current of the PNP transistor so that the charging current supplied to the secondary battery constituent does not exceed the rated current values of the secondary battery and the secondary battery constituent. The secondary battery power supply device according to claim 1, wherein the secondary battery power supply device is controlled.   The reverse current prevention circuit limits the base current of the PNP transistor by a resistance value of a resistor inserted between a base of the PNP transistor and a negative terminal of the secondary battery group. Secondary battery power unit.   The secondary battery power supply device according to claim 1, wherein the backflow prevention circuit has no active circuit components other than the PNP transistor.

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