JPH07336906A - Charging and discharging control circuit for secondary battery - Google Patents

Abstract

PURPOSE:To prevent memory effect by compulsorily discharging a secondary battery and beginning the next charging when this circuit detects, from a storage means, that the discharging property of a secondary battery has dropped, since the measured operation time was shorter than the specified minimum operation time, when it secondary battery is used after its charging was completed. CONSTITUTION:This control circuit stops a time when the voltage value measured with a battery voltage detecting circuit 7 becomes equal to the terminal voltage. And, if the timer value is smaller than the value equivalent to the minimum operation time stored in a ROM, this judges that the drop of discharging property by memory effect is seen in a secondary battery 1 in use. Next, in the case that AC power adds to it, this changes a changeover circuit 4 over to the side of an AC/DC circuit 2, and turns on a DC/DC circuit 3 so as to supply the main electric circuit 10a with voltage. And, this turns on a charging circuit 5 after finishing compulsive discharge by operating a compulsive discharging circuit 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery charge / discharge control circuit, and more specifically, it is mounted on an AC / DC electronic device that can be operated by an AC power source or a power supply from a secondary battery to charge / discharge the secondary battery. The present invention relates to a secondary battery charge / discharge control circuit for controlling.

[0002]

2. Description of the Related Art In recent years, there has been an increase in the number of electronic devices for both direct and alternating current that use a secondary battery. However, the method of using the secondary battery is limited to one that temporarily backs up when moving the device, or Even if the secondary battery is used continuously, if the warning of the voltage drop of the secondary battery is issued, the operation is stopped immediately and the battery is charged, or the AC power supply operation is switched to the final voltage. There was almost no such thing. Here, the cutoff voltage is a voltage indicating a limit at which discharging or charging is finished, and is a voltage corresponding to a practical use limit. For example, among secondary batteries, Ni-C
In a d battery (NiCd battery), when charging and discharging are repeated at a relatively shallow discharge depth by such a usage method, a deterioration in discharge characteristic called a memory effect phenomenon occurs, and a battery operation time becomes shorter than a normal discharge time. It has been known.

Here, the memory effect means that the discharge curve of the battery becomes smaller than the normal discharge curve by repeating charging and discharging for a short period of time without using the secondary battery (battery) until the cutoff voltage becomes lower than the cutoff voltage. This phenomenon is generally called the memory effect, because once it starts to drop, the voltage characteristic during discharge declines even after the battery is fully charged, and the battery operates as if it remembers partial discharge. I'm out. Also, this memory effect can be resolved by using up the secondary battery once,
Conventionally, the original discharge characteristic is restored by forcibly discharging once and then recharging. Therefore, in the electronic device using the nickel-cadmium battery, although the operation time is often shortened due to the memory effect, there are known means for preventing or eliminating the memory effect as described below.

FIG. 7 is a block diagram showing an example of a conventional secondary battery charge / discharge control circuit. In FIG. 7, AC / DC
The circuit 12 is a circuit that generates a charging voltage for the secondary battery 11 from an AC power source, and serves as a main power source that replaces the secondary battery 11 when the AC power source is operating. The DC / DC circuit 13 is a circuit that generates a direct current constant voltage required to directly operate the electric circuit 18a of the main body of the device, and one having a higher output voltage of the AC / DC circuit 12 or the secondary battery 11 is used. Is the diode D1
1 through D12. In addition, DC on the body side
A power key 18b for turning on / off the / DC circuit 13 is provided. The charging circuit 14 is a circuit for charging the secondary battery 11 via the diode 13 when an AC power source is applied, and the forced discharge circuit 15 is a circuit for forcibly discharging the secondary battery 11 by a resistor provided inside the circuit. Is.

The terminal voltage of the secondary battery 11 is measured by the battery voltage detection circuit 16 and the voltage value is sent to the control circuit 17. The control circuit 17 controls the charging circuit 14 and the forced discharge circuit 15 based on the voltage value measured by the battery voltage detection circuit 16. In the circuit of the prior art shown in FIG. 7, the terminal voltage before and after the final voltage is measured, the forced discharge circuit 15 is operated, and the secondary battery 11 is always additionally discharged until it becomes lower than the final voltage, or before charging. Always discharges to the final voltage to prevent the memory effect from occurring.

As another conventional technique, a final voltage and an over-discharge voltage lower than the final voltage are set when the secondary battery is discharged, and the secondary battery reaching the final voltage is forcibly discharged to the over-discharge voltage. Has been proposed to prevent the deterioration of the discharge characteristic due to the memory effect of the secondary battery (see "Battery Charger" in Japanese Patent Laid-Open No. 2-87938). Further, as another conventional technique, when the battery voltage is close to the final voltage, a method is proposed in which prior to charging, forced discharge is performed until the voltage becomes lower than the final voltage to eliminate the memory effect (JP-A-4-308429). (See "Battery Charger for Secondary Battery" in Japanese Patent Publication). In both cases, a forced discharge circuit composed of a discharge resistor and a switch circuit, etc. is used to obtain a deep discharge depth, and discharge that is not directly related to the operation of the device is performed until the cutoff voltage is reached, It was to restore the characteristics.

[0007] In addition, there is an alternating-current / direct-current electronic device using this type of secondary battery in which the secondary battery is detachable and can be charged by another dedicated charger. In this case, depending on the capacity of the secondary battery, there is a structure in which the user's finger touches the battery terminal on the device side. The one with an insulating structure in which the secondary battery and the switching circuit for AC / DC output are composed of relays, etc.
It is safe to touch the battery terminal because no leakage current occurs, but for example, the switching circuit is composed of semiconductor elements and is not insulated from the secondary battery, especially those that use a Schottky diode Since a large amount of leakage current is generated, when the user touches the battery terminal portion, there is a possibility of electric shock when the leakage current flows out through the human body to the ground.

In order to prevent this electric shock, in the prior art, a shutter mechanism is provided to prevent fingers from entering the entrance of the battery insertion portion, or the battery terminal portion is electrically set to the GND level when the secondary battery is not used. An electric shock protection circuit composed of a switch such as a transistor was provided.

FIG. 8 is a circuit diagram showing an example in which a conventional electric shock protection circuit is used in a power supply circuit of an AC / DC equipment. In FIG. 8, when the secondary battery 11a is not connected, the base of the transistor Q2 becomes LOW level, and Q2 is turned off. If AC power is applied in this state, AC /
The DC voltage is output from the DC circuit 12a, and the diode D
At the same time as being input to the DC / DC circuit 13a through 11a, the base of the transistor Q1 is raised to HIGH level through the resistors R2 and R3, and the transistor Q1 is turned on. When transistor Q1 turns on, diode D1
The reverse current of 2a flows to GND through the resistor R1. Therefore, even if the user touches the battery terminal portions T11 and T12, the human body is not electrically shocked.

[0010]

However, the secondary battery charge / discharge control circuit of the prior art uniformly discharges the secondary battery that has dropped to the vicinity of the final voltage, and therefore, during the forced discharge. Inevitably, the discharge resistor in the circuit generated heat. In addition, there is a problem that extra time is required for forced discharge before charging.

Further, in Japanese Patent Laid-Open No. 2-87938,
If charging and discharging are repeated without decreasing to the final voltage,
In some cases, the forced discharge function does not work and the memory effect cannot be eliminated. On the other hand, if the discharge voltage drops to the final voltage and the number of discharges increases, it is feared that the discharge characteristics of the secondary battery may be deteriorated and the life of the secondary battery may be shortened due to repeated overdischarge.

Further, in Japanese Patent Laid-Open No. 308429/1992, when discharging is performed until a low battery voltage alarm is issued each time, the battery voltage drops to near the end voltage, so that the function works to prevent the occurrence of the memory effect. However, since the forced discharge is performed every time the battery is charged regardless of the presence or absence of the memory effect, the time required for the forced discharge is a substantial extension of the charging time for the user. Further, the forced discharge is a useless power consumption as seen in the heat generation of the discharge resistor, and it is required to reduce the frequency.

FIG. 9 is a graph showing changes in the terminal voltage when the secondary battery is temporarily forcibly discharged to the final voltage.
As shown in FIG. 9, for example, a secondary battery (1.2 Volt Ni
-Secondary battery in which 10 Cd batteries are connected in series) is forcibly and temporarily discharged to the final voltage (10.8 Volt), the final voltage is detected and operation is stopped immediately, and the device is not operated for a while. If left unattended, the terminal voltage of the secondary battery immediately rises and exceeds the cutoff voltage, so the battery is charged without being forcibly discharged, so the memory effect could not be reliably prevented. .

The present invention has been made in consideration of the above circumstances. For example, by limiting the target of forced discharge to only the secondary battery having the memory effect, the charging time is extended and unnecessary power consumption is reduced. Provided is a secondary battery charge / discharge control circuit having a function of minimizing the increase and preventing the occurrence of a memory effect and a function of preventing an electric shock due to a leakage current from a battery terminal by using a forced discharge circuit. It is a thing.

[0015]

The present invention relates to a secondary battery which can be charged and discharged, an AC / DC circuit which is connected to an external AC power source and converts it into a predetermined DC voltage, and an AC / DC circuit. A charging circuit that charges the secondary battery with a DC voltage from the DC circuit, a forced discharge circuit that forcibly discharges the charging voltage charged in the secondary battery, and a final voltage from the terminal voltage of the secondary battery and higher than the final voltage. A battery voltage detection circuit that detects a preset alarm voltage in a voltage range, a switching circuit that switches power supply to a load from the AC / DC circuit to a secondary battery, and control of each circuit In a secondary battery charge / discharge control circuit having a control circuit, when the load is operated by using a secondary battery which has been charged, the terminal voltage of the secondary battery drops to an alarm voltage. Do And operation time storage means for minimum operation time preset by stored in, and measuring means for measuring the operating time up to the voltage of the secondary battery becomes the alarm voltage,
Further provided is a discharge characteristic judging means for judging whether or not the discharge characteristic of the secondary battery is deteriorated by comparing the measured operating time with the set minimum operating time, and a judgment information storing means for storing the judgment result. The control circuit determines that the operating time measured when the fully charged secondary battery is operated is shorter than the preset minimum operating time, and the discharge characteristic of the secondary battery is deteriorated. Is read from the judgment information storage means, the charging circuit is controlled so that the secondary battery is forcibly discharged until the final voltage is once reached by the forced discharge circuit and then the next charging is started. It is a battery charge / discharge control circuit.

According to the above configuration, when the load is operated by using the secondary battery that has been charged, when the operation time until the alarm voltage is reduced is shorter than the preset minimum operation time. The discharge characteristic determination means of the control circuit determines that the memory effect phenomenon is occurring in the secondary battery, and stores the determination result in the determination information storage means, so that the control circuit charges the secondary battery. The stored contents are checked immediately before, and when a memory effect occurs, the forced discharge circuit can perform forced discharge to the final voltage. Therefore, since only the secondary battery exhibiting the memory effect can be the target of forced discharge, unnecessary forced discharge can be avoided. Further, the secondary battery once determined to have the memory effect is stored in the determination result even if the battery voltage rises due to the stop of the operation before charging, so that the forced discharge is reliably performed and the memory effect can be prevented. . The alarm voltage referred to here is a voltage value preset in a voltage range higher than the final voltage of the secondary battery (the voltage indicating the limit at which discharging or charging is terminated), and when the secondary battery discharges, It serves as a reference voltage for detecting the memory effect phenomenon from the discharge characteristics.

While the load is operating by the power supply from the secondary battery side, the control circuit supplies AC power to the AC / DC circuit between the time when the voltage of the secondary battery drops to the alarm voltage and the time when it reaches the final voltage. When the secondary battery reaches the final voltage when the signal applied is applied, the power supply on the secondary battery side is changed to AC / DC.
It is preferable that the switching circuit is controlled to switch to the power supply on the circuit side. According to the above configuration, even if AC power is applied during operation of the secondary battery, the operation of the secondary battery continues to the cutoff voltage, and after a sufficient depth of discharge is maintained, the operation switches to the AC power supply. Therefore, it is not necessary to forcibly discharge the secondary battery before charging.

The control circuit is further provided with a battery terminal to which the secondary battery is attachable and detachable, and the control circuit is forcedly discharged when the battery voltage detection circuit detects a voltage level at which the secondary battery is unloaded. The circuit may be operated to bypass the leakage current generated in the battery terminal via the switching circuit. According to the above configuration, when the secondary battery is not installed, the leakage current generated in the switching circuit (the current flowing from the battery terminal to the earth ground through the human body when the battery terminal is touched) is bypassed through the forced discharge circuit. It is possible to prevent electric shock due to leakage current from a battery terminal without providing a special electric shock prevention circuit. Therefore,
The insertion part of the secondary battery can have a simple structure. Here, the voltage level at which the secondary battery is unloaded is, for example, a terminal voltage due to a leakage current generated in the switching circuit, which is a voltage level lower than the end voltage.

The secondary battery may have an alarm circuit for alarming the voltage drop of the secondary battery. In such a configuration, when the battery voltage detection circuit detects the secondary battery alarm voltage. In addition, the control circuit controls the alarm circuit so as to warn the battery voltage drop based on the detected signal, so that the user can confirm that the secondary battery has dropped to the alarm voltage.

The control circuit may further include a DC / DC circuit for generating a DC constant voltage for directly operating the load. In this case, the control circuit is AC.
Judge whether the power source has been added to the AC / DC circuit, and
Switching between the power supply from the DC circuit and the power supply from the secondary battery is performed by the switching circuit, and the DC power is supplied to the DC / DC circuit. Therefore, it is the power supply from the AC / DC circuit or the power supply from the secondary battery. However, a constant DC voltage can be obtained.

In the present invention, a Ni-Cd battery (NiCd battery) is used as the secondary battery. AC /
The DC circuit is composed of a switching regulator, a transformer, a diode bridge, a smoothing capacitor, a regulator IC, etc., and is converted from an AC power supply to a DC power supply (DC power supply). As a charging circuit,
It consists of a constant current circuit and a switch circuit. The forced discharge circuit is composed of a discharge resistor, a switch circuit composed of transistors and FETs. As the battery voltage detection circuit, for example, a reference voltage generation circuit (alarm voltage, end voltage,
And end-mounted voltage level generation circuit) and comparator IC
Composed of. The switching circuit is composed of a switching circuit. The DC / DC circuit includes a switching regulator and a regulator IC that generate a constant DC voltage suitable for a load (device).

The control circuit includes CPU, ROM, RA
A one-chip microcomputer including an M, a timer, and an I / O port is used. The ROM therein is used as the operating time storage means. A RAM is used as the judgment information storage means. Further, the timer therein is used as the measuring means. A CPU is used as the discharge characteristic determining means, and it functions as the discharge characteristic determining means of the secondary battery charge / discharge control circuit of the present invention according to the control program stored in the ROM. An LCD (liquid crystal display), an LED, a buzzer, or the like is used as the output means of the alarm circuit. Further, as the battery terminal, a conductive plate that press-contacts the electrode of the secondary battery is used.

[0023]

The present invention will be described in detail below based on the embodiments shown in the drawings. The present invention is not limited to this. The present invention is mainly directed to an AC / DC electronic device (for example, product example: which can be operated by either an AC power source or a secondary battery).
It is suitable to be applied to a secondary battery charge / discharge control circuit of a medical bedside monitor), and each constituent element has a function other than achieving the "memory effect detection function of the secondary battery and its generation prevention function" of the present invention. It has the function of preventing electric shock due to leakage current from the battery terminals.

FIG. 1 is a block diagram showing an embodiment of a secondary battery charge / discharge control circuit of the present invention. In FIG. 1, reference numeral 1 denotes a secondary battery composed of a chargeable / dischargeable Ni—Cd battery.
Further, the battery terminal portion T is provided in the insertion portion for setting the secondary battery 1.
1, T2 are provided. Reference numeral 2 is an AC / DC circuit that generates a charging voltage for the secondary battery 1 from an AC power source.
It becomes the main power source instead of the secondary battery 1 when the power source operates. The AC / DC circuit 2 is composed of a switching regulator, a transformer, a diode bridge, a smoothing capacitor, a regulator IC, or the like, and outputs an AC detection signal when AC power is applied. Reference numeral 3 denotes a DC / DC circuit that generates an optimum DC constant voltage for directly operating the device, and is composed of a switching regulator, a regulator IC, and the like.

4 is the output of the AC / DC circuit 2 or the secondary battery 1
It is a switching circuit for switching any one of the above and inputting it to the DC / DC circuit 3. The switching circuit is composed of a switch circuit composed of transistors, FETs, etc., and can be independently ON / OFF controlled (switch controlled). 5 is AC power supply
/ DC circuit 2 is a charging circuit for charging the secondary battery 1 via the diode D3 when being applied, for example,
It is composed of a constant current circuit and a switch circuit. Reference numeral 6 denotes a forced discharge circuit for forcibly discharging the secondary battery 1, which is composed of a discharge resistor and a switch circuit. Reference numeral 7 denotes a battery voltage detection circuit for measuring the terminal voltage of the secondary battery 1, which is composed of an A / D conversion circuit composed of a reference voltage generation circuit (alarm voltage, end voltage generation circuit) and a comparator IC, and the measured voltage. The value is sent to the control circuit 9 described later.

8 is an LCD (liquid crystal display), LE
An alarm circuit composed of output means such as D and a buzzer,
When the measured voltage reaches a preset alarm voltage in the voltage range higher than the final voltage, the control circuit 9 sends a signal to the alarm circuit 8 to warn the voltage drop of the secondary battery 1. Reference numeral 9 is a control circuit, which uses a one-chip microcomputer including a CPU, a ROM, a RAM, a timer, and an I / O port. A power key signal, an AC detection signal,
Based on the voltage value measured by the battery voltage detection circuit 7, D
The C / DC circuit 3, the switching circuit 4, the charging circuit 5, and the forced discharge circuit 6 are controlled.

The CPU of the control circuit 9 composed of a one-chip microcomputer or the like measures the operating time when the secondary battery is used with a timer and stores the preset minimum operating time in the ROM. The measured operating time and the set minimum operating time are compared to determine whether or not the characteristic has deteriorated, and the control program is controlled to store the determination result in the RAM. Control circuit 9
In the RAM of, the diode D1 or the diode D2
Since the power is supplied from the AC / DC circuit 2 or the secondary battery 1 via the capacitor and can be backed up by the capacitor, the judgment result can be always stored and retained. Instead of the RAM, an E ² PROM which is a non-volatile memory may be provided to store the judgment result. Further, the ROM stores a control program for operating the secondary battery charge / discharge control circuit of the present invention. A power key 10b for turning on / off the DC / DC circuit 3 for supplying a DC voltage to the main body electric circuit 10a is provided in the device body, and the power key 10b is turned on / off.
By doing so, a power key signal is sent to the control circuit 9.

2 and 3 are flowcharts showing the operation 1 of the secondary battery charge / discharge control circuit of the present invention. 2 and 3
The operation 1 of the present invention will be described based on the flow. The flow when AC power is not applied is as follows. When the power key is pressed (step S1a),
The presence or absence of the AC detection signal is confirmed (step S2a), and the AC
If no detection signal is input, the battery voltage detection circuit 7
It is checked whether or not the voltage value V _BAT measured in step 3 exceeds the final voltage V ₀ (step S3a). V _BAT is V ₀
If:
Return to a). If V _BAT exceeds V ₀ , the switching circuit 4 is switched to the secondary battery 1 (step S4a), and DC /
The DC circuit 3 is turned on to supply a voltage to the main body electric circuit 10a of the device (step S5a).

At this time, the flag F1 indicating the memory effect occurrence on the RAM is set to "0" (step S6a), and the timer for measuring the operation time is reset and started (step S7a). If the AC detection signal is input in step S2a, the process proceeds to step S21a and subsequent steps in the flow (A) of AC power supply operation. During operation,
The presence or absence of the AC detection signal is confirmed (step S8a), and if the AC detection signal is input, the timer is stopped (step S9a), and the flow proceeds to the AC power supply operation flow (A).

In step S10a, the flag F1 is set to
Check if it is "1" and F1 = "1"
For example, V_BATIs the alarm voltage V_ALMTo check if
(Step S11a). V_BAT= V_ALMIf so, an alarm
A signal is sent to the circuit 8 to warn of low battery voltage (step
(Step S12a), and at the same time, stop the timer (step
S13a). The memory effect phenomenon is seen in the secondary battery 1.
Check whether or not (step S14a), timer
Value T_OPHowever, the minimum motion that was previously stored in ROM
Value T corresponding to work time_MINGreater than or equal to,
The discharge key of the secondary battery 1 is judged to be normal, and the power key
Check whether a signal is input (step S16a),
V _BAT= V₀The operation is continued until it is determined (step S1)
7a).

Further, in step S14a, T _OP is T _MIN
If it is smaller than the above, it is determined that the secondary battery 1 in use has deteriorated discharge characteristics due to the memory effect, the flag F1 is set to "1" (step S15a), and it is checked whether the power key signal is input ( Step S16a), V _BAT = V ₀
The operation is continued until it is determined (step S17a). If V _BAT = V ₀ in step S17a, the flag F1 is set to "0" (step S18a), and DC / DC is set.
The circuit 3 is turned off to stop the operation (step S19).
a).

Next, the case where AC power is applied will be described. If the AC detection signal is input in step S2a, the switching circuit is switched to the AC / DC circuit 2 side (step S21a), the DC / DC circuit 3 is turned on, and the voltage is supplied to the main body electric circuit 10a of the device ( Step S22
a). Next, it is checked whether the flag F1 is "1" (step S23a), and if it is "1", the forced discharge circuit 6
To perform forced discharge of the secondary battery 1 (step S
24a). During forced discharge, the voltage value V _BAT is constantly checked (step S25a), and if V _BAT becomes V ₀ or less, the forced discharge circuit 6 is turned off to end the forced discharge (step S2).
6a), the flag F1 is set to "0" (step S27).
a).

After the forced discharge is completed, the charging circuit 5 is turned on (step S28a) to charge the secondary battery 1. If the flag F1 is not "1" in step S23a, forced discharge is not performed, and the secondary battery 1 is immediately discharged in step S28a.
Start charging. It is checked whether a power key signal is input (step S29a), and unless the power key signal is input, the device continues to operate while charging the secondary battery 1. When the power key signal is input, the charging circuit 5 is turned off.
Then, the charging circuit is turned off (step S30a), and DC /
The DC circuit 3 is turned off to stop the operation (step S3
1a).

Therefore, in the above operation 1, it is possible to detect the deterioration of the discharge characteristic due to the memory effect depending on the operation time of the secondary battery, and to limit the target of the forced discharge. Further, if an AC power source is applied during operation, only the secondary battery having the memory effect is forcibly discharged to prevent the secondary battery having no memory effect from being forcibly discharged.
Minimized extension of charging time and unnecessary power consumption.

4 and 5 are flow charts showing the operation 2 of the secondary battery charge / discharge control circuit of the present invention. 4 and 5
Operation 2 of the present invention will be described based on the flowchart of FIG. When the AC power is not added, it is as follows. When the power key is pressed (step S1b), A
The presence or absence of the C detection signal is confirmed (step S2b), and if the AC detection signal is not input, it is checked whether or not the voltage value V _BAT measured by the battery voltage detection circuit 7 exceeds the end voltage V ₀ ( Step S3b). If V _BAT is V ₀ or less, wait for power key input (step S1)
Return to. If V _BAT exceeds V ₀ , the switching circuit 4 is switched to the secondary battery 1 side (step S4b), and DC / D
Turn on the C circuit 3 to supply voltage to the device (step S
5).

At this time, the flag F2 indicating the low battery voltage warning on the RAM is set to "0" (step S6b). If the AC detection signal is input in step S2b, the process proceeds to step 21b and subsequent steps in the flow (B) of AC power supply operation. During operation, the presence or absence of the AC detection signal is confirmed in step S7b. If the AC detection signal is input, the flow proceeds to AC power supply operation flow (B). Next, in step S8b, it is checked whether the flag F2 is "1", and if F2 = "1", it is checked whether V _BAT has reached the alarm voltage V _ALM (step S9).
b).

If V _BAT = V _ALM , a signal is sent to the alarm circuit 8 to warn of the low battery voltage (step S10).
b), the flag F2 is set to "1" (step S11)
b). Whether the power key is pressed (step S12b),
The operation is continued until it is determined that V _BAT = V ₀ (step S1
3b). If V _BAT = V ₀ in step S13b, the flag F2 is set to "0" (step S14), and D
The C / DC circuit 3 is turned off to stop the operation (step S
15b).

Next, the case where AC power is applied will be described. When the AC detection signal is input to the control circuit 9 (B), it is first checked whether the flag F2 is "1" (step S21b). If the flag F2 is "1", the switching circuit 4 is switched to the secondary battery 1 side (step S22b), the DC / DC circuit 3 is turned on, and a voltage is supplied to the main body electric circuit 10a of the device (step S23).
b). Always check V _BAT during operation (step S2
4b), if V _BAT becomes V ₀ or less, set flag F2 to “0”
(Step S25b), the switching circuit 4 is set to AC / D.
Switching to the C circuit 2 side (step S26b), the charging circuit 5 is turned on to start charging the secondary battery 1 (step S29b).

In step S21b, the flag F2 is "0".
If so, the switching circuit 4 is switched to the AC / DC circuit 2 side (step S27b), the DC / DC circuit 3 is turned on, and the voltage is supplied to the device (step S28b). In step S29b, the charging circuit 5 is turned on to charge the secondary battery 1 while operating the device. It is checked whether or not the power key is input (step S30b), and unless the power key is input, the device continues to operate while charging the secondary battery 1. If the power key is pressed, the charging circuit 5
Is turned off (step S31b), the DC / DC circuit 3 is turned off to stop the operation (step S32b).

Therefore, in the above-mentioned operation 2, when the AC power source is applied during the operation of the secondary battery until the final voltage is reached after the low battery voltage alarm is issued, the operation of the secondary battery is continued until the final voltage. Since the discharge is continued and a sufficient depth of discharge is secured, it is possible to prevent the occurrence of the memory effect. In addition, the need for forced discharge is eliminated, and useless power consumption that is not directly related to the operation of the device can be avoided. It should be noted that, even when the detection function of the memory effect of the operation 1 is added to the operation 2 and it is determined that the memory effect has occurred, even if the AC power is applied to the secondary battery until the final voltage is reduced, By continuing the operation of the secondary battery, deep discharge up to the cutoff voltage can be obtained without performing forced discharge, so there is no need to consume unnecessary power in the forced discharge circuit, and extension of forced discharge is avoided. be able to.

FIG. 6 is a flowchart showing the operation 3 of the secondary battery charge / discharge control circuit of the present invention. Operation 3 of the present invention will be described based on the flowchart of FIG. In the operation 3, it is premised that the secondary battery 1 is removable by the user and the user's finger touches the battery terminal portions T1 and T2. Since the flow chart is the same as that of the operation 1 when the AC power is not applied, the description thereof will be omitted. If the AC detection signal is input to the control circuit 9 (C),
The switching circuit 4 is switched to the AC / DC circuit 2 side (step S21c), the DC / DC circuit 3 is turned on, and voltage is supplied to the device (step S22c).

Next, the secondary battery is inserted into the battery terminal portion T.
1, set to T2, ie V _BAT
Is below the terminal voltage V _MIN when the secondary battery is not attached (step S23c). If V _BAT exceeds V _MIN , the flow from step S24c onward is operated in the same manner as the operation 1. If V _BAT is equal to or lower than V _MIN , the forced discharge circuit 6 is turned on (step S33c), and the operation is continued until the power key signal is input (step S34c).
Therefore, in the above-described operation 3, the leakage current generated in the switching circuit 4 during the operation of the AC power supply is reduced to G
Since it is possible to prevent the user from receiving an electric shock when the battery is poured into the ND and touches the battery terminal portions T1 and T2, the insertion portion of the secondary battery can have a simple structure.

[0043]

According to the present invention, the following effects can be obtained. (1) When the secondary battery of AC / DC equipment has a decrease in discharge characteristics called memory effect due to repeated shallow discharge and charging, the charge / discharge circuit automatically detects the deterioration of the characteristics during battery operation. However, since the detection result is stored and retained regardless of whether the subsequent device state is operating or not, the discharge characteristic of the secondary battery in which the memory effect has occurred can be reliably recovered by the forced discharge before charging. . Further, by limiting the target of forced discharge, useless power consumption and extension of charging time can be minimized. (2) If an alarm for low battery voltage is issued during operation with the secondary battery and the secondary battery operation is automatically continued until the cutoff voltage even if AC power is immediately applied, sufficient discharge is possible. The depth can be secured, and the memory effect can be prevented from occurring. (3) If the secondary battery is a removable device and the memory effect is eliminated by a forced discharge circuit, and the switching circuit between the AC power supply and the secondary battery is composed of a semiconductor such as a Schottky diode, it is special. Since the electric shock due to the leakage current from the battery terminal portion can be prevented without providing a simple electric shock prevention circuit, the insertion portion of the secondary battery can have a simple structure.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a secondary battery charge / discharge control circuit of the present invention.

FIG. 2 is a flowchart showing an operation 1 of the secondary battery charge / discharge control circuit of the present invention.

FIG. 3 is a flowchart showing operation 1 of the secondary battery charge / discharge control circuit of the present invention, which is subsequent to FIG. 2;

FIG. 4 is a flowchart showing an operation 2 of the secondary battery charge / discharge control circuit of the present invention.

FIG. 5 is a flowchart showing Operation 2 of the secondary battery charge / discharge control circuit of the present invention, which is subsequent to FIG. 4;

FIG. 6 is a flowchart showing an operation 3 of the secondary battery charge / discharge control circuit of the present invention.

FIG. 7 is a block diagram showing an example of a conventional secondary battery charge / discharge control circuit.

FIG. 8 is a circuit diagram showing an example in which a conventional electric shock protection circuit is used in a power supply circuit of an AC / DC device.

FIG. 9 is a graph showing changes in the terminal voltage when the secondary battery is temporarily forcibly discharged to the final voltage.

[Explanation of symbols]

 1 Secondary Battery 2 AC / DC Circuit 3 DC / DC Circuit 4 Switching Circuit 5 Charging Circuit 6 Forced Discharging Circuit 7 Battery Voltage Detection Circuit 8 Alarm Circuit 9 Control Circuit 10a Main Electric Circuit 10b Power Key D1 to D3 Diode

Claims (3)

[Claims] 1. A rechargeable secondary battery, and an AC / AC connected to an external AC power source and converting the AC / DC power into a predetermined DC voltage.
DC circuit, a charging circuit for charging the secondary battery with a DC voltage from the AC / DC circuit, a forced discharging circuit for forcibly discharging the charging voltage charged in the secondary battery, and a terminal voltage from the terminal voltage of the secondary battery And a battery voltage detection circuit that detects a preset alarm voltage in a voltage range higher than the cutoff voltage, a switching circuit that switches power supply to the load from the AC / DC circuit to the secondary battery, and In a secondary battery charge and discharge control circuit having a control circuit for controlling each circuit, the control circuit, when the load is operated using a secondary battery that has been charged, the secondary battery An operating time storage means that presets and stores the minimum operating time until the terminal voltage drops to the alarm voltage, and a measuring means that measures the operating time until the voltage of the secondary battery becomes the alarm voltage. Shi Further comprising a discharge characteristic judging means for judging whether or not the discharge characteristic of the secondary battery is deteriorated by comparing the operating time and the set minimum operating time, and a judgment information storing means for storing the judgment result. The control circuit, the operating time measured when the rechargeable secondary battery is operated is shorter than the preset minimum operating time, the discharge result of the secondary battery is determined to have deteriorated. When read from the determination information storage means, the charging circuit is controlled so that the secondary battery is forcibly discharged until the final voltage is once reached by the forced discharging circuit and then the next charging is started. Charge / discharge control circuit. 2. The control circuit controls the AC / DC circuit during the time when the voltage of the secondary battery drops to the alarm voltage and reaches the final voltage while the load is operating by the power supply on the secondary battery side. When the secondary battery reaches the cutoff voltage when it receives a signal with AC power applied, the power supply on the secondary battery side is changed to AC / D.
The secondary battery charging / discharging control electric circuit according to claim 1, wherein the switching circuit is controlled so as to switch the power supply to the C circuit side. 3. The control circuit further comprises a battery terminal that allows a secondary battery to be attached and detached, and when the battery voltage detection circuit detects a voltage level at which the secondary battery is unloaded at the battery terminal. The secondary battery charge / discharge control circuit according to claim 1, wherein a forced discharge circuit is operated to bypass a leakage current generated in a battery terminal via the switching circuit.