JPH0723951U - Charger - Google Patents

Abstract

(57) [Summary] [Object] To provide a charging device capable of significantly reducing power loss by detecting a charging current in a non-contact manner. A charging device 10 for charging a rechargeable battery 7 having a characteristic that a charging current decreases as charging progresses,
The coil means 12 is provided in the charging circuit 11, and the magnetic field detection means 14 is provided in the vicinity thereof. Then, when the charging stopping means 15 recognizes that the detection value by the magnetic field detecting means becomes smaller than the predetermined value, it is determined that the charging is completed, and the charging is stopped. As a result, non-contact current detection can be performed and power loss can be suppressed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a charging device for a storage battery used in a power supply circuit of electronic equipment.

[0002]

[Prior art]

 Generally, in electronic devices such as portable word processors and audio devices, the route of supplying power from an AC power source via an AC adapter and charging / discharging rechargeable batteries are used in consideration of usability of the device. There may be a two-system power route consisting of a power supply route.

An outline of a power supply circuit of such an electronic device will be described with reference to FIG. 3. An alternating current (AC) voltage of 100 V passes through a step-down device 1 made up of a transformer and a rectifier 2 made up of a diode bridge, and a changeover switch 3 From the rectifier 2 to the electronic equipment drive unit 4 and the voltage from the rectifier 2 is boosted by the DC-DC booster 5 to reach the charger 6, which charges the charging battery 7 such as a lithium ion battery. And a route for supplying electric power to the electronic device drive unit 4 by charging. Then, switching between start and stop of charging of the rechargeable battery 7 is performed by the charging switch 8 which is interlocked with the changeover switch 3, and when charging is performed, electric power is supplied from the AC power supply side to the electronic device drive section 4 side. Then, when charging is not performed, electric power is supplied from the rechargeable battery side to the drive section 4 side.

An example of a conventional charging device for charging the rechargeable battery 7 will now be described with reference to FIG. 4. The charger 6 includes a charge switch 8, a rechargeable battery 7, and a resistor 9 for current detection in series. A circuit is connected, and by detecting the voltage of the resistor 9, the charging is stopped in response to the charging current falling below a predetermined value.

[0005]

[Problems to be solved by the device]

 By the way, the control for detecting the decrease in the charging current and stopping the charging as described above is used when charging a charging battery, for example, a lithium ion battery, which has a characteristic that the charging current decreases as the charging progresses. In the charging characteristics of this type of lithium-ion battery, as shown in FIG. 5, the charging voltage indicated by the curve A gradually increases as the charging time elapses, and then becomes constant at about 4.1V. On the other hand, the charging current indicated by the curve B 1 is a constant charging current of about 500 mA at the beginning, but gradually decreases. Normally, when the charging current drops to 50 mA, charging is stopped assuming that the charging is completed. In order to detect 50 mA indicating the end of this charging, the voltage across the resistor 9 for current detection shown in FIG. 4 is detected as described above. In order to prevent overcharging, regardless of the charging current value, the charging is stopped 2 hours after the start of charging.

However, in such a conventional charging device, since the charging current is always passed through the resistor 9 for current detection during charging, jar heat is generated in the resistor 9. It causes power loss. In particular, this power loss becomes extremely large at the beginning of charging with a large charging current. Further, there is a problem that the heat generated by the power loss has a great adverse effect on precision electronic devices.

Further, although the resistance 9 for detecting the current is about 2Ω, the voltage across the resistance 9 becomes 1 V at the beginning of charging when the charging current of 500 mA flows, and the charging current drops to 50 mA. In the latter period, the voltage across the resistor 9 drops to 0.1V. Therefore, assuming that the voltage across the rechargeable battery 7 is 4.1V, the voltage loss is high, that is, the charger 6 must output a maximum voltage of 5.1V, which is a large-scale device. I had no choice but to transform it. In this case, it is conceivable to reduce the value of the resistor 9 for current detection in order to suppress power loss, but this makes it difficult to detect the voltage when the current is minimum, and there is a risk of erroneous detection.

The present invention has been made in view of the above problems and was devised in order to effectively solve them. The purpose is to detect the charging current in a non-contact manner to significantly reduce the power loss. It is to provide a charging device that can be reduced.

[0009]

[Means for Solving the Problems]

 In order to solve the above problems, the present invention provides a charging device for charging a rechargeable battery having a characteristic that the charge current decreases as the charge progresses, and a magnetic field is generated by the charge current provided in the charge circuit of the rechargeable battery. A coil means for generating, a magnetic field detecting means for detecting a magnetic field from the coil means, and a charge stopping means for stopping charging of the rechargeable battery based on an output of the magnetic field detecting means. Is.

[0010]

[Action]

 Since the present invention is configured as described above, when charging of the charging battery is started, a magnetic field is generated in the coil means provided in the charging circuit by the charging current flowing through the coil means. It is detected by the detection means. Receiving the detection signal from now on, the charge stopping means compares the detected value with the reference value, and if the current drops to the reference value, for example, 50 mA, recognizes that the charging is completed and operates to stop the charging. As a result, the resistance for current detection that has been conventionally required is eliminated and the charging current can be detected in a non-contact manner, so that it is possible to eliminate unnecessary power loss due to the resistance.

[0011]

【Example】

 Hereinafter, an embodiment of a charging device according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a circuit configuration diagram showing an example of a charging device according to the present invention, and FIG. 2 is a circuit configuration diagram showing a main part of the circuit shown in FIG. The same parts as those of the conventional device shown in FIG. 4 are designated by the same reference numerals.

The charging device 10 is incorporated in a power supply circuit (see FIG. 3) of an electronic device such as an audio device, like the conventional charging device. That is, in the charging circuit 11 extending from the charger 6, a charging switch 8, a coil means 12, which is a feature of the present invention, and a charging battery 7, which has a characteristic such that the charging current decreases as the charging progresses like a lithium ion battery, are sequentially performed. It is interposed and is configured so that the coil means 12 can generate a magnetic field proportional to the magnitude of the charging current flowing through the charging circuit 11.

The coil means 12 is for strengthening the generated magnetic field, and uses a coil that generates a sufficiently large magnetic field that can be detected by a hole sensor described later. Pattern coils are not enough. Then, for example, a Hall sensor 14 is arranged as magnetic field detecting means in the vicinity of the coil means 12, specifically at one end of the coil means 12, and at the position of the central magnetic field 13 by the coil means 12, and this Hall sensor is used. The output of 14 is input to the charging stopping means 15 which is, for example, a microcomputer.

The charge stopping means 15 has a comparator 16 as shown in FIG. 2, for example, and the output signal from the Hall sensor 14 is input to the + terminal of the comparator 16 via a resistor 17. At the same time, a reference voltage corresponding to the charging current for completion of charging, for example, 50 mA is input to this-terminal, and the reference voltage and the detection signal voltage are compared. Then, in response to the detection signal voltage becoming lower than the reference voltage, that is, in response to the charging current becoming 50 mA or less, the charging stop signal S1 for stopping charging is sent to the charging switch 8 It is configured to output to. In the figure, 18 and 19 are resistors connected to a drive circuit for driving the Hall sensor 14, and 20 is a resistor interposed between the + terminal of the comparator 16 and the ground.

Next, the operation of this embodiment configured as described above will be described. First, when charging the charging battery 7 by the charging device 10, the charging switch 8 is closed as indicated by the solid line, and the charging battery 7 is energized. The charging voltage at this time is low at the beginning of charging as shown by the curve A in the graph of FIG. 5, and gradually increases to become constant at about 4.1 V which is the standard voltage of the rechargeable battery 7. On the other hand, as shown in the curve B, the charging current initially flows at 500 mA for a certain period of time, and then the charging current tends to gradually decrease as the charging time elapses. That is, the constant current is initially applied, and the constant voltage charging is performed from the middle.

When a charging current flows through the coil means 12, a magnetic field 13 proportional to the magnitude of this current is generated in the coil means 12, and this magnetic field is detected by the Hall sensor 14 arranged near the coil. Become. Then, this detected value is input to the charging stopping means 15 and compared with the reference voltage corresponding to 50 mA in the comparator 16 therein.

As a result, when the detection signal voltage indicating the charging current is larger than the reference voltage (corresponding to 50 mA), the charging is insufficient and the charging is continued. When the detection signal voltage indicating is smaller than the reference voltage, it indicates that the charging current has become 50 mA or less, and the charging is completed. Therefore, the charging stop means 15 outputs the charging stop signal S1 for stopping the charging toward the charging switch 8, and the charging switch 8 receiving this signal S1 is opened as shown by the broken line in FIG. In this state, the charging circuit 11 is opened and charging is stopped.

As described above, in this embodiment, the coil means 12 and the hall sensor 14 are used to indirectly provide the charging current in a non-contact manner to detect the charging current. Since it is not necessary to use the detection resistor 9 (see FIG. 4), the power loss due to the charging current flowing through the resistor can be greatly reduced. In this respect, the direct current resistance in the coil means 12 is only about 0.1 to 0.3Ω, and the power loss in this portion is very small.

Further, since the power loss is greatly reduced as described above, it is possible to suppress the amount of heat generation, and therefore it is possible to significantly reduce the adverse effects on electronic devices that are easily affected by heat, such as optical pickups. Can be suppressed. Furthermore, when setting the charging voltage from the charger 6, it is not necessary to consider the voltage drop in the resistor 9 for current detection, which is required in the conventional device. Can be narrowed. In the above-mentioned embodiment, the lithium-ion battery is used as an example of the rechargeable battery 7, but the present invention is not limited to this, and the characteristic that the charging current decreases as the charging progresses (at first, the constant current is constant current). Then, it can be applied to any battery as long as it has a constant voltage from the middle. Furthermore, even a battery of constant current charging can be applied to a quick charging device that initially charges with a large current.

[0020]

[Effect of device]

 As described above, according to the charging device of the present invention, the following excellent operational effects can be exhibited. Since the charging current is obtained by non-contact, it is not necessary to use the resistor for current detection, which was required in the past, and the power loss can be reduced accordingly. Further, since the power loss can be reduced, the amount of heat generation can be suppressed accordingly, and it is possible to prevent the electronic components sensitive to heat from being adversely affected. Furthermore, since it is not necessary to consider the voltage drop in the resistance for current detection, which is conventionally required, the voltage required for charging can be reduced accordingly.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an example of a charging device according to the present invention.

FIG. 2 is a circuit configuration diagram showing a main part of the circuit shown in FIG.

FIG. 3 is a block diagram showing a general power supply circuit of an electronic device.

FIG. 4 is a circuit configuration diagram showing a conventional charging device.

FIG. 5 is a graph showing a relationship between a charging voltage and a charging current when charging a rechargeable battery.

[Explanation of symbols]

7 ... Rechargeable battery, 10 ... Charging device, 11 ... Charging circuit, 12
... Coil means, 14 ... Hall sensor (magnetic field detection means),
15 ... Charging stop means, S1 ... Charging stop signal.

Claims (1)

[Scope of utility model registration request] 1. A charging device for charging a rechargeable battery having a characteristic that the charge current decreases as the charge progresses, and a coil means provided in a charging circuit of the rechargeable battery to generate a magnetic field by the charge current; A charging device comprising magnetic field detecting means for detecting a magnetic field from the battery, and charge stopping means for stopping charging of the rechargeable battery based on the output of the magnetic field detecting means.