JPH07143681A - Battery charger - Google Patents

Abstract

PURPOSE:To prevent the memory effect of a secondary battery by charging the battery affer sufficiently discharging the battery. CONSTITUTION:At the time of charging a secondary battery 21 with electricity, such a voltage that its polarity is opposite to that of the voltage of a secondary battery 21 and the sum of the voltage and the voltage of the battery 21 exceeds the reverse conducting voltage of the controlling rectifier element of a current direction limiting section 26 is applied across the current direction limiting section 26 by detecting the voltage of the battery 21 and inverting the polarity of a positive terminal 14 and negative terminal 15 so that a voltage of the opposite polarity required for discharge can be applied across the battery 21 and, at the same time, the controlling rectifier element of the section 26 can be conducted in the reverse direction and the energy of the battery 21 can be consumed. Thus the battery 21 is discharged. Therefore, the memory effect of the battery 21 can be prevented, since the battery 21 is charged after the battery 21 is deeply discharged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for a secondary battery having a memory effect, such as a nickel-cadmium battery.

[0002]

2. Description of the Related Art Nickel / cadmium batteries and nickel /
It is generally known that a secondary battery such as a hydrogen battery has a so-called memory effect in which the battery capacity gradually decreases when shallow discharge and insufficient charging are repeated.

Many means for preventing such a memory effect have been proposed, for example, Japanese Patent Laid-Open No. 4-26.
There are configurations such as those disclosed in Japanese Unexamined Patent Publication No. 332 and Japanese Unexamined Patent Publication No. 5-182694.

In these devices, a changeover switch for changing over to the charging side or the discharging side is provided in the charging circuit, and the changeover switch is automatically or manually changed over to the discharging side at the time of charging, and the discharging resistance consumes the battery power to discharge the battery. After that, the changeover switch is switched to the charging side for charging. By this means, the secondary battery is fully discharged and then charged, so the memory effect of this type of secondary battery is effectively prevented. can do.

By the way, as shown in FIG. 3, in a device with a built-in secondary battery, in order to prevent the secondary battery 3 from being consumed due to an inadvertent short circuit between the positive and negative electrode connection terminals 1 and 2, a backflow prevention device is provided. There is one in which a backflow prevention circuit 4 including a controlled rectifying element, for example, a diode is connected.

[0006]

In a device with a built-in secondary battery to which such a backflow prevention circuit 4 is connected, a secondary battery is provided by a charger having a changeover switch and a discharge resistance as disclosed in the above-mentioned publication. Even if an attempt is made to discharge the battery, there has been a problem that the backflow prevention circuit 4 in the device containing the secondary battery blocks the flow of the discharge current and thus cannot discharge the battery.

The present invention solves the above-mentioned problems. Even in a device with a built-in secondary battery having a rectifying element for preventing backflow, the secondary battery can be sufficiently discharged, and a changeover switch and a discharge resistor are used. It is an object of the present invention to provide a charging device that can prevent the memory effect by making it unnecessary.

[0008]

In order to achieve the above object, the present invention provides a charging circuit for supplying a charging current to a secondary battery of a device to be charged through positive / negative terminals, and a positive / negative terminal of the charging circuit. A charger having a discharge circuit that reverses the polarity to form a discharge circuit of the secondary battery, a controller that operates the discharge circuit when the secondary battery requires a charging voltage, and the secondary battery and a positive connection Connected between the terminals and forms a charging circuit for the secondary battery when a positive charging voltage is applied,
The charging target device has a current direction limiting unit that forms a discharging circuit of the secondary battery when a voltage having a polarity opposite to the charging voltage is applied.

Further, the current direction limiting section is configured to have a controlled rectifying element. In addition, the configuration includes a control unit that controls the current direction limiting unit according to the voltage and polarity between the positive and negative electrode connection terminals of the device to be charged.

The voltage of the reverse polarity applied to the current limiting section is a voltage whose sum with the open circuit voltage of the secondary battery exceeds the reverse conduction voltage of the controlled rectifying element.

Further, in response to the voltage drop of the secondary battery due to discharging, the voltage drop amount is corrected and a voltage of reverse polarity is applied to the current limiting section.

[0012]

In the above structure, when the device to be charged is connected to the charger and the open circuit voltage of the secondary battery is detected, the control unit of the charger sends a signal to the discharge circuit, and the discharge circuit outputs positive and negative terminals. The polarity is reversed, and a voltage having the opposite polarity and the sum of the open voltage of the secondary battery and the reverse conduction voltage of the controlled rectifying element exceeds the reverse conduction voltage is applied to the current direction limiting unit of the device to be charged. As a result, the voltage of the opposite polarity required for discharging is applied to the secondary battery, the control rectifying element conducts in the opposite direction, the battery energy is consumed, and the secondary battery is discharged.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In the figure, 10 is a charger, which is a charging circuit 1.
1 and a discharge circuit 12, a charging / discharging unit 13, a positive electrode terminal 1
4, a charging terminal unit 16 having 4 and a negative electrode terminal 15, a voltage detection unit 17, and a control unit 18 are incorporated.

The charging circuit 11 includes a positive electrode terminal 14 and a negative electrode terminal 1.
A secondary battery such as a nickel-cadmium battery or a nickel-metal hydride battery (hereinafter referred to as 2
A charging current is supplied to the secondary battery 21).
The voltage detection unit 17 intermittently detects the voltage of the secondary battery 21 during charging / discharging and sends the value to the control unit 18. The control unit 18 reverses the polarities of the positive and negative terminals 14 and 15 of the charging terminal unit 16 when the voltage detected by the voltage detection unit 17 is higher than the final voltage of the secondary battery 21 and is the required charging voltage. When the voltage of the secondary battery 21 reaches the end voltage, the predetermined discharge voltage is applied, and the voltage drop caused by the discharge of the secondary battery 21 is corrected so that the predetermined discharge voltage is applied. Positive and negative terminal 14,1
The discharge circuit 12 is operated so that 5 is rotated in the normal direction.

Next, 20 is a device to be charged, which is a secondary battery 2
1, positive connection terminal 22, negative connection terminal 23, load circuit 2
4, a voltage processing circuit 25, a charge / discharge control unit 29 having a current direction limiting unit 26, a voltage detection unit 27, and a control unit 28 is incorporated.

The positive and negative connection terminals 22 and 23 are connected to the charger 10.
Of the secondary battery 21, the positive electrode connecting terminal 22 is connected to the positive electrode of the secondary battery 21 via the charge / discharge control unit 29, and the negative electrode connecting terminal 23 is the secondary battery 21. Is connected to the negative electrode of. Reference numeral 20 denotes a device to be charged, for example, a cordless telephone, which operates at an appropriate voltage processed by the voltage processing circuit 25. The current direction limiting unit 26 is connected between the positive electrode connection terminal 22 and the positive electrode of the secondary battery 21, applies a charging current at the time of charging, and prevents the reverse flow of the electric energy of the secondary battery 21 at the time of a short circuit. A controlled rectifying element that conducts in the opposite direction during discharge, such as −
It is formed of a directional breakdown diode, a bidirectional breakdown diode, a two-pole bidirectional thyristor, a three-pole bidirectional thyristor, and the like. The voltage detection unit 27 detects the voltage and polarity between the positive and negative connection terminals 22 and 23 and sends the value and polarity to the control unit 28. The control unit 28 causes the control rectifying element to conduct in the reverse direction when the voltage detected by the voltage detecting unit 27 is higher than the reverse conduction voltage of the control rectifying element and the polarity is the polarity inverted by the discharge circuit 12. The current direction limiting unit 26 is operated.

The voltage detector 27 and the controller 28
Can be omitted when the current direction limiting unit 26 uses a controlled rectifying element having no gate.

In the above structure, when the electric energy of the secondary battery 21 is consumed and drops to a predetermined set voltage V ₂ as shown in FIG. 2 (c), it is appropriate that the voltage processing circuit 25 needs charging. You will be notified by various means. When the device to be charged 20 is connected to the charger 10 by this notification, charging of the secondary battery 21 is started.

In this charging, the charged device 20 is positive,
The negative electrode connection terminals 22 and 23 are the positive and negative electrode terminals 1 of the charger 10.
4 and 15, the voltage detection unit 17 of the charger 10 is connected.
Starts the voltage detection operation T ₁ as shown in FIG. Then, it detects that the battery voltage of the secondary battery 21 is the predetermined set voltage V ₂ shown in FIGS. 2B and 2C, and sends the value to the control unit 18. Since the set voltage V ₂ is the required charging voltage which is higher than the final voltage V ₁ of the secondary battery 21, the control unit 18 sends the operation signal to the discharging circuit 12 as shown in FIG. By this signal, the discharge circuit 12 reverses the polarities of the positive and negative terminals 14 and 15 of the charger 10 to the opposite polarities, and the sum of the open voltage of the secondary battery is distributed to the current direction limiting unit 26 of the device 20 to be charged. A predetermined discharge voltage having a value exceeding the reverse conduction voltage of the control rectifying element provided is applied to the inverted positive and negative terminals 14 and 15.

As a result, it is supplied from the discharge circuit 12.
The discharge current is inverted and becomes the positive electrode terminal 15
-Negative electrode connecting terminal 23-Secondary battery negative electrode-Secondary battery positive electrode
-Current direction limiting unit 26-Positive electrode connection terminal 22-Inverted
It flows in the circuit of the positive electrode terminal 14 which becomes the negative electrode, and the secondary battery 21
Voltage is discharged as shown in FIG. ₂
After that the final voltage V₁Descend to. In this discharge,
In the controlled rectifying element provided in the current direction limiting unit 26,
A specified discharge voltage exceeding the reverse conduction voltage is applied.
As a result, the controlled rectifying element conducts in the opposite direction, and
The battery 21 is discharged by a reverse polarity current flowing through it.
It

When a controlled rectifying device having a gate is used in the current direction limiting section 26, the device to be charged 2 is charged.
The zero voltage detection unit 27 detects the polarities and voltages of the positive and negative electrode connection terminals 22 and 23 and sends them to the control unit 28, and the control unit 28 controls the trigger to the gate to move the control rectifying element in the forward or reverse direction. Conduct in the direction. Then, the secondary battery 21 can be discharged by conducting electricity in the opposite direction.

In this discharge, the voltage applied from the discharge circuit 12 is the sum of the open circuit voltage of the secondary battery and the reverse direction of the control rectifying element arranged in the current direction limiting section 26 of the device 20 to be charged. Although the discharge voltage has a predetermined value that exceeds the conduction voltage, the battery voltage may drop as the secondary battery 21 discharges, and the discharge voltage may drop below a predetermined discharge voltage. In such a case, since the voltage detection unit 17 of the charger 10 intermittently detects the voltage, the control unit 18 corresponds to the detected value, that is, the voltage drop of the secondary battery 21. It is possible to operate the discharge circuit 12 to correct the discharge voltage and maintain the discharge voltage at a predetermined discharge voltage.

[0024] Thus, when the secondary battery 21 reaches the end voltages V ₁ is discharged, its value is detected by the voltage detection unit 17 of the charger 10 at the stop voltages V ₁ is time T ₃ control unit 18 is output. The control unit 18 determines that the battery voltage is the final voltage V
_Since it is ₁ , a stop signal is sent to the discharge circuit 12 as shown in FIG. By this signal, the discharge circuit 12 reverses the polarities of the positive and negative terminals 14 and 15 of the charger 10 to the positive polarity and stops the application of the discharge voltage to stop the charging circuit 1.
Switch the circuit to 1. As a result, as shown in FIG. 2D, the charging circuit 11 operates to start charging, and the charging current is as follows: charging circuit 11-positive electrode terminal 14-positive electrode connecting terminal 22-current direction limiting unit 26-secondary battery Positive electrode-Negative electrode of secondary battery-
The voltage of the secondary battery 21 flows through the circuit of the negative electrode connection terminal 23 to the negative electrode terminal 15 and rises as shown in FIG. 2C, and becomes the fully charged V ₃ state after the time T ₄ . This full-charge voltage V ₃ is detected by the voltage detector 17 and the value thereof is sent to the controller 18, as shown in FIG. Since the battery voltage is V ₃ , the control unit 18 stops the charging operation of the charging circuit 11 at time T ₅ as shown in FIG. 2 (d).

During this charging, a forward conduction voltage is applied to the controlled rectifying element arranged in the current direction control unit 26, so that the controlled rectifying element conducts in the forward direction, whereby the secondary battery 21 is positively charged. A sexual current flows to charge the battery.

As described above, according to the charging apparatus of the embodiment of the present invention, the polarities of the positive and negative terminals 14 and 15 of the charger 10 are reversed by the open circuit voltage of the secondary battery 21 detected during charging. Since a voltage having the opposite polarity and the sum of the open voltage of the secondary battery 21 and the reverse conduction voltage of the control rectifying element is applied to the current direction limiting unit 26, the secondary battery 2
A reverse polarity voltage required for discharging is applied to 1 and the control rectifying element conducts in the reverse direction to consume battery energy, and the secondary battery 21 is discharged. As a result, the secondary battery 21 is deeply discharged and then charged,
It is possible to prevent the memory effect peculiar to this type of battery.

[0027]

As is apparent from the above description, according to the present invention, the open circuit voltage of the secondary battery is detected at the time of charging, and the positive and negative terminals of the charger are reversed by the discharge circuit, and the reverse polarity is set to 2 By applying a voltage whose sum of the open-circuit voltage of the secondary battery exceeds the reverse conduction voltage of the controlled rectifying element to the current direction limiting unit, the reverse polarity voltage required for discharging is applied to the secondary battery. And the controlled rectifying element conducts in the opposite direction,
Battery energy is consumed and the secondary battery is discharged. As a result, the secondary battery is deeply discharged and then charged, so that the memory effect peculiar to this type of battery can be prevented.

As described above, according to the present invention, even a device with a built-in secondary battery having a rectifying element for preventing backflow can sufficiently discharge the secondary battery and does not require a changeover switch or discharge resistance. It is possible to provide a charging device capable of preventing the memory effect.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a charging device according to an embodiment of the present invention.

FIG. 2 is a timing chart explaining the same operation.

FIG. 3 is a block circuit diagram of a secondary battery internal device of a conventional charging device.

[Explanation of symbols]

 10 Charger 11 Charge circuit 12 Discharge circuit 14 Positive electrode terminal 15 Negative electrode terminal 18 Control part 20 Charged device 21 Secondary battery 22 Positive electrode connection terminal 23 Negative electrode connection terminal 26 Current direction limiting part 28 Control part

Claims (5)

[Claims] 1. A charging circuit for supplying a charging current to a secondary battery of a device to be charged through positive and negative terminals and a discharge circuit for the secondary battery by reversing the polarities of the positive and negative terminals. A charger having a discharge circuit and a control unit for operating the discharge circuit at a required charging voltage of the secondary battery;
The secondary battery is connected between the secondary battery and the positive electrode connection terminal, and forms a charging circuit for the secondary battery when a positive charging voltage is applied, and the secondary battery when a voltage having a polarity opposite to the charging voltage is applied. And a device to be charged having a current direction limiting unit that forms the discharging circuit of 1. 2. The charging device according to claim 1, wherein the current direction limiting unit includes a controlled rectifying element. 3. The charging device according to claim 1, further comprising a control unit that controls the current direction limiting unit according to the voltage and polarity between the positive and negative electrode connection terminals of the device to be charged. 4. The reverse polarity voltage applied to the current direction limiting section is a voltage whose sum with the open circuit voltage of the secondary battery exceeds the reverse conduction voltage of the controlled rectifying element. The charging device described. 5. The charging device according to claim 4, wherein the charging device responds to a voltage drop of the secondary battery due to discharging, and corrects the voltage drop and applies a voltage of reverse polarity to the current limiting unit.