JP3074694B2 - Charging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a charging device suitable for detecting a voltage, a charge amount, a charge end, and the like of a secondary battery.

[Summary of the Invention]

The present invention relates to a charging device suitable for use in detecting the voltage of a secondary battery, the amount of charge, the end of charging, and the like, with respect to a charging device that performs constant current charging control and constant voltage charging control on a secondary battery,
A voltage control means for intermittently switching the charging current at a predetermined cycle; an output control means for controlling the charging current to a very small current during the intermittent operation; and a voltage detecting means for detecting the battery voltage during the intermittent operation. The battery charging amount of the secondary battery is set from the voltage value detected by the above, the voltage between the battery voltage before the intermittent state and the battery voltage in the intermittent state is detected, and the voltage difference becomes equal to or less than the predetermined voltage value. A charging device capable of detecting the amount of charge and detecting the end of charging by increasing the accuracy of battery voltage detection by occasionally ending charging is provided.

[Conventional technology]

Generally, in a rechargeable secondary battery or the like, when measuring the charge amount during the charging of the secondary battery, the curve (20) in FIG. 4 is used between the open voltage (V) and the charge amount (%) of the secondary battery. If there is a correlation as shown in), the open-circuit voltages V ₁ , V ₂の of the secondary battery
‥ V ₄ By measuring, it is possible to detect the amount of charge of the secondary battery. Here, as shown in the circuit diagram of FIG. 6A, for example, the output terminal of a charger (21) having a plug (1) inserted into an outlet of a commercial AC power supply should be charged via a switching means (22). To measure the open voltage during charging by connecting the secondary battery (12), set the switching means (22) to the "OFF" state, and use a voltmeter (23) or the like to open the open voltage of the secondary battery (12). Is measured. In general,
When the secondary battery (12) is rapidly charged, constant current charging is performed. For example, in order to supply a relatively large charging current of 1A to 2A to the secondary battery (12), this large current is turned on and off. "
A high-current switch is required as the switching means (22) for making such a switch, and such a switch has a problem that not only the cost is increased but also the reliability is deteriorated. Furthermore, when rapid charging is performed with such a large current, a voltage drop occurs due to wiring resistance, contact resistance between the charger (21) and the secondary battery (12), and the internal resistance of the secondary battery (12). I do. In particular, the secondary battery is housed in a casing and handled as one accessory part. In a video camera or the like, the positive and negative terminals when the battery is attached / detached have a contact structure, and are connected to the charger (21) via the contact structure. The contact resistance of this part is usually 50mΩ ~ 1
Although it is about 00mΩ, the value is 200
It changes to about mΩ. That is, the contact resistance changes each time the secondary battery is attached or detached, and the amount of change in the open-circuit voltage of the secondary battery during charging is:
For example, when the charging current is 2A and the contact resistance is 200mΩ, the voltage is 0.4V. However, when the charging current is 2A and the contact resistance is 100mΩ, the voltage is 0.2V.
The voltage change amount increases. That is, as shown in the charging characteristic curve of FIG. 5, the open-circuit voltage characteristic curve (26) of the secondary battery (12) is different from the battery voltage characteristic curve (25) at the time of quick charging as shown by the broken line. Will occur. Incidentally, (27) shows a charging current characteristic curve at the time of rapid charging. In order to detect the open-circuit voltage without being affected by such a change in the open-circuit voltage, the switch means (22) is turned off as shown in FIG. An adverse effect that requires the switching means (22) occurs. Therefore, as shown in FIG. 6B, a large number of contact groups (13) (14) (13a) (14a) are provided in a casing (24) for accommodating the secondary battery (12).
A secondary battery is connected between the contacts (13) and (14) of the contact group to allow a large current to flow, and a voltmeter (23) is connected between the contacts (13a) and (14a) to detect voltage. Things have also been done.

[Problems to be solved by the invention]

As described in the conventional example, in the charging device having the configuration shown in FIG. 6A, the large current 1A to 2A at the time of rapid charging is turned on and off.
A large-capacity switching means (22) is required for the switching, and a switching means capable of withstanding such a large current has a problem that the cost is high and the reliability is poor. Furthermore, the charging device having the configuration shown in FIG. 6B is disadvantageous not only in terms of space and cost, but also has a problem in that the accuracy of the open-circuit voltage measurement is deteriorated because the measurement is performed while including the internal resistance of the secondary battery.

The present invention has been made in order to solve the above-mentioned problems, and has as its object to detect a voltage at a place where a charging current is small in order to reduce an error due to a voltage drop of the above-described various resistors. Thus, a battery charger with improved battery voltage detection accuracy is obtained.

[Means for solving the problem]

As shown in FIG. 1 and FIG. 2, the charging device of the present invention is a charging device that performs constant current charging control and constant voltage charging control on a secondary battery. And a voltage control means for controlling the charging current to a very small current when intermittent, and a voltage detecting means for detecting the battery voltage during intermittent operation. In addition to setting the battery charge amount of the battery, detecting the voltage between the battery voltage before the intermittent state and the battery voltage in the intermittent state and terminating the charging when the voltage difference falls below a predetermined voltage value. It is.

[Action]

According to the charging device of the present invention, the output current error reference voltage source REF ₁ and the voltage of the secondary battery (12) that is switching to switch control means a reference voltage REF ₂ (10) of the detecting means (17) Is detected, the detection accuracy of the battery open-circuit voltage at the time of this detection is improved, and the charge amount and the charge end can be detected.

〔Example〕

Hereinafter, an embodiment of the charging device of the present invention will be described with reference to FIGS. FIG. 1 shows an overall system diagram of the present embodiment, FIG. 2 is a circuit diagram of a main part of FIG. 1, and is a circuit example when a control circuit for charging is performed by a CPU, and FIG. It is a charge characteristic curve explanatory view of an example.

In FIG. 1, an AC voltage from an AC plug (1) inserted into an outlet of a commercial AC power supply is input through an input filter (2), a rectifier circuit (3), a conversion transformer (4) and a rectifier / smoothing circuit (5). This DC voltage is supplied to the positive terminal (13) where the anode terminal of the secondary battery (12) is connected and charging is performed. Rechargeable battery (12) at negative terminal (14)
Is connected between the negative terminal (14) and the ground, and the charge current detecting resistor (15) is connected to the negative terminal (14). The extracted charging current is supplied to the output control circuit (8). The charging voltage supplied from the smoothing circuit (5) to the secondary battery (12) via the positive terminal (13) is also supplied to the charging voltage detection circuit (9) and detected by the charging voltage detection circuit (9). The detection voltage is supplied to the charge control circuit (10). Charge control circuit (10)
Is connected to the display unit (11). For example, the display unit (11) displays the amount of charge by measuring the battery open voltage as described with reference to FIG. The charging control circuit (10) is constituted by a microcomputer (hereinafter, referred to as CPU) or the like, and controls the output control circuit (8). In the output control circuit (8), a charging current detecting resistor (15)
And a constant current control means for comparing a charging current supplied from the hot terminal with a reference current. The CPU (10) outputs a control signal for switching and controlling the reference voltage of the constant current control means in the output control circuit (8). The output of the output control circuit (8) is supplied to the light emitting element of the photocoupler (7). The light emitted from the light emitting element is converted to an electric signal by a light receiving element and supplied to a PWM (pulse width modulation) control circuit (6), and the DC output supplied from the rectifying circuit (3) to the conversion transistor is converted to a transistor ( 16) Via PWM.

A specific circuit of a main part of the above system diagram will be described with reference to FIG.
Parts corresponding to those in FIG. 1 will be described with the same reference numerals. One end of the primary winding of the conversion transformer (4) is connected to one end of a rectifier circuit (3) and the other end is connected to the collector of an output transistor (16) constituting a PWM control circuit (6), and the emitter is grounded. . The base of the transistor (16) is a PWM control circuit (6)
Connected to the output end of the The input end of the PWM control circuit (6) the collectors of such light-receiving element T _r2 of the phototransistor constituting the photocoupler (7) is connected, the emitter is grounded, the base receives light from the light emitting element CD ₂ . Secondary battery anode of the light emitting element CD ₂ consisting of a light emitting diode or the like constituting a photocoupler (7) for charging (1
Is connected through a resistor R ₁ to the positive terminal of the anode 2) is connected (13), the output current error detecting operational amplifier cathode of the light emitting element CD ₂ constituting the output control circuit (8) (1
7) is connected to the output end. Conversion transformer (4) of the secondary winding side rectifying consisting diode CD ₁ and the capacitor C ₁ and the like, a smoothing circuit (5) is provided. One end of the secondary winding of the converter transformer (4) is grounded, the other end is connected to the anode of the diode CD _1, the secondary battery with the cathode of the diode CD ₁ is connected to one end of the capacitor C ₁ (1
It is connected to the positive terminal (13) to be connected in 2). The other end of the capacitor C ₁ is grounded. The negative terminal (14) to which the cathode of the secondary battery (12) is connected has a resistor (1
5) is connected, and one end of this resistor (15) is grounded. The charging current extracted from the midpoint of the connection between the resistor (15) and the negative terminal (14) is supplied to the non-inverting input terminal of an output current error detecting operational amplifier (17) constituting a constant current control means. The inverting input terminal of the operational amplifier (17) is connected to the movable contact a of the switch SW, and the fixed contacts b,
c is connected to two reference voltage sources REF ₁ and REF _2.
The other end of reference voltage source REF ₁ and REF ₂ are each connected to ground.
Voltage of the reference voltage source REF ₁ and TEF ₂ is not only selected by switching over the switch SW, it may be as provided voltage varying means for varying the voltage of one of the reference voltage source continuously. This switch SW or voltage varying means is controlled by the output of the CPU (10). The CPU (10) includes digital-to-analog conversion means and analog-to-digital conversion means, etc., converts the control signal (10a) for controlling the switch SW into an analog signal and outputs it, and also converts the analog charging current to digital. To the CPU (10).

The operation of this example in the above configuration will be described with reference to the charging characteristic curve diagram of FIG.

In FIG. 1 and FIG. 2, the charging voltage is changed to secondary through the input filter (2), the rectifier circuit (3), the PWM control circuit (6), the conversion transformer (4), the rectifier, and the smoothing circuit (5). Supplied to the battery (12). Operational amplifier (17) compares the charging current flowing through the resistor (15) and the reference voltage source REF _1, flow the output error current to the light emitting element CD ₂ of photocoupler, fast-charge current characteristic curve shown in FIG. 3A ( For example, as shown by the constant current curve (27a) of 27), the constant current drive is performed so that the current becomes 2A.

In the period I (see FIG. 3A) in which the constant current control is performed, the battery voltage characteristic curve (25) and the battery open-circuit voltage characteristic curve (26) of the quick charging time gradually increase the voltage. It becomes constant, and the charging current gradually decreases. Generally, in the I and II regions, the switching regulator performs constant current and constant voltage control.

 In this example, only the constant current control means is shown.

The error signal of the above operational amplifier (17) is supplied to the PWM control circuit (6) via the light-emitting element CD ₂ → light receiving element T _r2 of the photocoupler (7), and conversion transformer (4) to the parallel transistor (16) The output of a charging current (including a charging voltage, not shown) supplied to the secondary battery (12) via the rectification and smoothing circuit (5) is controlled to be constant. When in this example of measuring the battery voltage, and outputs a control signal from the CPU (10) to the switch SW switches the movable contact piece a of the switch SW to the reference voltage source REF ₂ side. Reference voltages V ₁ of the reference voltage source REF ₂ is at the fast charge current characteristic curve (27) and the constant current curves (27a) as shown in FIG. 3B and C of FIG. 3A and the enlarged waveform chart, at the time of switching The constant current is, for example, 0.1 A or less (0
). Battery voltage characteristic curve at the time of quick charge under such 0.1A switching constant current control (25)
The quick-charge 2A battery voltage (25a) of the battery is the battery open-circuit voltage characteristic curve (26) when the battery voltage at the time of 0.1A charging is divided by the battery open-circuit voltage. The voltage of the secondary battery at this time is detected by the charging voltage detection circuit (9), and the detected voltage is supplied to the CPU (10), and the LED (eg, By lighting the display element that displays the 25% charge amount, it is possible to indicate that the 25% charge is completed. Such control signal (10a) fast charge and voltage detecting charging of the reference voltage source REF ₁ and REF ₂ for performing switching according to is carried out in a cycle of about once, for example, between 1 to 5 minutes. Even in the constant voltage control region II, if such a switching is performed, it is possible to detect the charge end state of the battery as shown in FIG. 3C. That is, the voltage difference between the fast-charge 2A battery voltage (25a) and the battery voltage at the time of 0.1A charging (26a) = ΔV is measured, and the charging is terminated when the −ΔV falls below a predetermined voltage value. I just need.

According to such a charging device, the detection accuracy of the battery voltage is greatly improved. In other words, if the minute current is 0.1 A as in the embodiment, even if the contact resistance greatly changes to 200 mΩ, it is 0.1 A × 200 m
Ω = 0.02V, and the detection accuracy of the rechargeable battery voltage can be increased to nearly 20 times compared to the switching of the charging current of 2A.

Further, the large-capacity switch (22) as described with reference to FIG. 6A is not required, so that the size can be reduced, and a charging device capable of displaying the charge amount and detecting the state of completion of charging can be obtained.

It is apparent that the present invention is not limited to the above-described embodiments, but can be variously modified without departing from the gist of the present invention.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to the charging device of this invention, the accuracy of battery voltage detection improves, a circuit becomes simple, and the thing which can display the charge amount and can detect the end of charge is obtained.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of a charging device of the present invention.

FIG. 2 is a circuit diagram of a main part showing an embodiment of the charging device of the present invention.

FIG. 3 is an explanatory diagram of a charging characteristic curve of the present invention.

FIG. 4 is a conventional battery voltage-charge amount characteristic curve diagram.

FIG. 5 is an explanatory diagram of a conventional charging characteristic curve.

FIG. 6 is a configuration diagram of a conventional charging device.

[Explanation of symbols]

7 photocoupler, 8 output control circuit, 9 charging voltage detection circuit, 10 CPU, 11 display unit, 12 rechargeable battery, 17 operational amplifier

Continuation of the front page (56) References JP-A-49-133843 (JP, A) JP-A-63-209436 (JP, A) JP-A-1-162738 (JP, U) (58) Fields studied (Int .Cl. ⁷ , DB name) H02J ^7/ 00-7/10 H02J ⁷ /34-7/35

Claims (2)

(57) [Claims] 1. A charging device for controlling constant current charging and constant voltage charging of a secondary battery, a charging control means for intermittently switching the charging current at a predetermined cycle, and controlling the charging current to a very small current when intermittent. Output control means, and voltage detecting means for detecting a battery voltage at the time of intermittent operation. The battery charge of the secondary battery is set from the voltage value detected by the voltage detecting means, and the battery before the intermittent state is provided. A charging device comprising: detecting a voltage between a voltage and a battery voltage in an intermittent state; and terminating charging when the voltage difference becomes equal to or less than a predetermined voltage value. 2. The charging device according to claim 1, wherein the battery charging capacity obtained by the charging device is displayed on a display unit.