JPH07231573A - Battery charging circuit - Google Patents

Abstract

PURPOSE:To determine a defective cell accurately by starting the charging operation when a battery voltage measured during forcible discharge exceeds a threshold level, stopping the charging operation when a fully charged voltage is reached and notifying that the battery is defective when the battery voltage is lower than the threshold level. CONSTITUTION:In a circuit for discharging a battery at a predetermined time interval and charging the battery after the battery voltage is checked, a battery 1 to be charged and a circuit 3 for discharging the battery 1 forcibly by connecting a dummy resistor across the battery are provided. Battery voltage is detected when the circuit 3 discharges the battery forcibly. If the battery voltage thus measured is higher than a threshold value, charging operation is started, and when a full charge voltage is reached, charging operation is stopped. A charging circuit 2 repetitively notifies that the battery 1 is defective when the battery voltage is lower than the threshold value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charging circuit for discharging a battery every predetermined time to check the battery voltage and then charging the battery.

[0002]

2. Description of the Related Art Information equipment loses data when the power supply is cut off. Backing up the power supply with a battery to avoid this has been rapidly increasing in recent years.

Since the battery naturally discharges and its capacity gradually decreases, it is necessary to charge the battery without using it.
For this reason, conventionally, as shown in FIG. 8, constant charging is continuously performed, and when a battery voltage check period is reached, a dummy resistor is connected and discharged, and the voltage at this time is checked to determine whether the battery can be used. If it is OK, the charging is restarted again. On the other hand, when the battery is found to be unusable, an alarm is displayed to inform the user that the battery should be replaced. The configuration and operation of FIG. 8 will be briefly described below.

FIG. 8 is an explanatory view (1) of the prior art. FIG. 8A shows the relationship between the battery charging period and the check period and the cell voltage. Here, the charging period of the battery is a period of charging the battery with a constant voltage. The check period is a period in which a dummy resistor is connected to discharge the battery and it is determined whether the battery can be used or not according to the voltage at that time.

Next, the operation of the configuration of FIG. 8A will be briefly described with reference to the flowchart of FIG. 8B. Figure 8
In (b) of S, S61 starts charging the battery at a constant voltage. This starts charging the battery at a constant voltage, as described as the battery charging period in FIG. 8A.

[0006] S62 is for checking the battery voltage,
After stopping the charging, the battery is discharged for a predetermined time and the voltage is detected. When it is determined that the battery can be used, the discharge voltage after this discharge becomes equal to or higher than the predetermined threshold and the discharge voltage is OK, and the process returns to S61. On the other hand, if the discharge voltage NG indicates that the battery cannot be used, ALM
(Alarm) is displayed and charging is stopped.

Further, when the battery is charged with a constant voltage, even if the battery is charged at an optimum charging voltage at room temperature,
When the temperature changes, the internal impedance of the battery changes, resulting in a deviation from the optimum charging voltage as shown in FIG. The configuration and operation of FIG. 9 will be briefly described below.

FIG. 9 is an explanatory view (No. 2) of the prior art. FIG. 9A shows how the battery is charged at normal temperature and high temperature. Here, charging current characteristics at room temperature (optimum value)
Shows the state when the charging voltage is set so as to perform optimum charging. The charge current characteristic at high temperature (overcharge) shows the state when the charge voltage is set so that optimal charging is performed at room temperature and the temperature becomes high.

Next, the operation of the configuration of FIG. 9A will be briefly described with reference to the flowchart of FIG. 9B. Figure 9
In (b) of S, S71 starts charging the battery at a constant voltage. This starts charging the battery with a constant voltage, as shown in FIG.

In step S72, it is determined whether the battery life period has elapsed. For example, it is determined whether three years have passed since the start of using the battery. If the battery has reached the end of life (in the case of NG), the battery replacement is prompted in S74, and S71 is repeated after the battery replacement. On the other hand, if the battery life is not reached (OK), the process proceeds to S73.

In step S73, it is determined whether a backup operation has occurred due to a power failure. When the backup is normally completed, the process returns to S71 and is repeated. On the other hand, if the backup cannot be performed (NG), the backup cannot be performed and the ALM (alarm) is displayed and sounded to inform the user.

A plurality of batteries are connected in series and used as an input backup for high voltage (for example, 30V to 240V). At this time, when the voltage drop is monitored, the voltage drop of each battery is not confirmed, but the accumulated drop amount of the high voltage is detected as shown in FIG. There was a circuit to do this. The configuration and operation of FIG. 10 will be briefly described below.

FIG. 10 is an explanatory view (No. 3) of the prior art. In FIG. 10, the battery is a battery in which a plurality of cells are connected in series.

COMP is a comparator for comparing the reference voltage with the voltage obtained by dividing the battery voltage by the resistors R1 and R2, and detecting that the battery voltage has dropped below the reference voltage. When the voltage drops below the reference voltage, an ALM (alarm) signal is output.

The forced discharge circuit connects a dummy resistor to the battery to forcibly discharge it. Next, FIG.
The operation of the configuration will be briefly described.

(1) When the forced discharge circuit is OFF,
The voltage obtained by dividing the battery voltage by the resistors R1 and R2 is compared with the reference voltage. Normally, the divided voltage is higher, so ALM (alarm) is not output.

(2) While the forced discharge circuit is ON, the voltage obtained by dividing the battery voltage by the resistors R1 and R2 is compared with the reference voltage. If the divided voltage is lower than the reference voltage, ALM (alarm) is output.

[0018]

In the case described above with reference to FIG. 8, since the battery is constantly charged with a constant voltage, the battery may be overcharged and the positive electrode of the battery expands. There is a problem that the active material is peeled off and the electrolysis station is vaporized and leaks out of the case to accelerate the deterioration of the battery.

Further, in the case described with reference to FIG. 9 described above, the internal impedance of the battery becomes small at a high temperature and overcharge occurs even if the optimum charging is performed at room temperature by the constant voltage. However, there was a problem that the change in charging due to temperature was not taken into consideration.

Further, in the case described with reference to FIG. 10 described above, in a battery in which a plurality of cells are connected in series,
When detecting a voltage drop such as between the full charge voltage and the discharge voltage of the battery, the voltage change of the entire battery was detected, so the voltage drop amount of one defective battery is compared with the full voltage. It was small and difficult to detect.

The present invention solves these problems.
Constant voltage when the battery is forcibly discharged and above a specified voltage,
Switching to a constant current after the constant current or the initial constant voltage and then stopping when the full charge voltage is reached, or detecting the voltage drop of the battery by extracting the voltage change using a capacitor, The purpose is to optimally set the charging current during floating charging of the battery and to measure the voltage drop during discharging with high sensitivity.

[0022]

FIG. 1 shows a block diagram of the principle of the present invention. In FIG. 1, a battery 1 is a battery to be charged.

The charging circuit 2 starts charging when the battery voltage when the battery is forcibly discharged is equal to or higher than a threshold value, stops charging when the battery voltage reaches a full charge voltage, and stops charging when the battery voltage is equal to or lower than the threshold value. It outputs the fact of the failure of.

The forced discharge circuit 3 connects dummy resistors to both ends of the battery 1 for forced discharge. Power supply 4
Is for supplying a DC power source such as the charging circuit 2.

In the voltage detection circuit 5, a capacitor and a resistor are connected in series at both ends of the battery 1, and the voltage V changed when the capacitor is forcibly discharged at the connection point of the capacitor and the resistor is a threshold value or more. At some times, it is determined that the battery 1 is defective, and when it is below the threshold value, it is determined as normal.

[0026]

According to the present invention, as shown in FIG.
When a dummy resistor is connected to both ends of the battery 1 for forced discharge, the charging circuit 2 starts charging when the battery voltage measured at the time of this forced discharge is equal to or higher than the threshold value and reaches a full charge voltage. The charging is stopped at that time, and when it is below the threshold value, the fact that the battery 1 is defective is output.

At this time, after the battery 1 is held in the self-discharged state for a predetermined time or longer, the forced discharge circuit 3 connects the dummy resistors to both ends of the battery 1 to discharge it, and the charging circuit 2 measures the battery voltage at this time. , It is designed to measure the battery voltage quickly by eliminating the operation delay of chemical reaction.

When the measured battery voltage is above the threshold value, constant voltage charging or constant current charging is started, and when the full charge voltage is reached, the charging is stopped. Is output.

Further, when the measured battery voltage is equal to or higher than the threshold value, the constant voltage charging is initially performed, and the charging is performed when the full charge voltage is reached by switching to the constant current charging characteristic at a predetermined current or less or after a lapse of a predetermined time. I'm trying to stop.

When a capacitor and a resistor are connected in series to both ends of the battery 1 and the forced discharge circuit 3 is forcibly discharged, the voltage detection circuit 5 detects the voltage V at the connection point between the capacitor and the resistor. Measured, this measured voltage V
Is output above the predetermined threshold value, the fact that the battery 1 is defective is output.

Therefore, the floating charge of the battery 1 is set to a constant voltage,
Switching to a constant current after the constant current or initially constant voltage and then stopping when the full charge voltage is reached, or detecting the voltage drop of the battery by extracting the voltage change using a capacitor This makes it possible to always charge the battery at the optimum charging current without being affected by temperature and chemical reaction delay during floating charging of the battery, and to accurately measure the voltage drop of a battery consisting of multiple cells to identify defective cells. It becomes possible.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the construction and operation of an embodiment of the present invention will be described in detail with reference to FIGS.

FIG. 2 is a diagram (No. 1) for explaining the operation of the present invention. Here, the horizontal axis represents time and the vertical axis represents the cell voltage of the battery. In FIG. 2, the check period is a period in which the battery 1 is forcibly discharged and is determined to be normal when the battery voltage at that time is equal to or higher than a predetermined threshold value, and is defective when the battery voltage is equal to or lower than a predetermined threshold value. This check period is usually several hundred milliseconds for a battery mounted on a portable computer.

The charging period is a period in which the battery 1 is charged to the full charge voltage when it is determined to be normal during the check period. This charging period is typically a few seconds for batteries that are installed in portable computers.

The charging suspension period is a period in which charging is suspended. This charging suspension period is usually 2 to 4 hours in the case of a battery attached to a portable computer. Figure 3
FIG. 3 is a flowchart (No. 1) for explaining the operation of the present invention. This explains the operation procedure in the operation explanatory view of FIG.

In FIG. 3, S1 starts battery charging (constant current). This starts charging the battery 1 with a constant current during the charging period of FIG. In S2, charging is stopped when the full charge voltage is reached. This is because the charging circuit 2 is S1
The battery voltage at that time starts to be charged at, and the battery voltage at that time is the full charge voltage (the voltage at which the battery 1 is completely charged)
Stop charging when reaching.

In S3, the battery self-discharges. This is because the charging was stopped when the full charge voltage was reached in S2, and the battery self-discharges thereafter (charging stop period in FIG. 2). In S4, for battery voltage check, after charging is stopped, the battery is discharged for a predetermined time and the voltage is detected. This is because the forced discharge circuit 3 forcibly discharges the battery 1 by connecting the dummy resistor after the charge suspension period in FIG. 2, for example, 2 to 4 hours, and the battery voltage at that time is detected. When the detected battery voltage is equal to or higher than the threshold value and the discharge voltage is OK, the capacity of the battery 1 is determined to be normal.
Return to and repeat. On the other hand, when the detected battery voltage is below the threshold value and the discharge voltage is NG, the battery 1
Since the capacity of was smaller than the specified value and it was found to be defective,
ALM (Aream) stop (displays and sounds when the battery is defective, informs the operator to prompt replacement, and stops recharging).

As described above, when the battery 1 is floatingly charged, it is forcibly discharged, and when the voltage at that time is equal to or higher than the threshold value, it is determined to be normal, and the battery 1 is charged. Then, after the lapse of a predetermined charging stop period, the forced discharge is repeated again to charge the battery 1 to the full-charge voltage and stop it, thereby eliminating overcharge. In addition, there is a charge suspension period before the forced discharge, and it is necessary to perform the forced discharge for many times until the stable state is reached due to the delay in the chemical reaction when switching from the conventional constantly charged state to the forced discharge. However, since the charging suspension period is provided in the present invention, it is possible to measure the stable voltage drop of the battery 1 with the minimum forced discharge time, and to reduce the amount of charge due to the small amount of forced discharge, thereby shortening the life of the battery 1. It is possible to extend it to the maximum.

FIG. 4 shows a block diagram of another embodiment of the present invention. This shows a circuit diagram when constant voltage charging is performed at the beginning of the charging period and constant current charging is performed at or below a predetermined current value or after a predetermined time has elapsed.

FIG. 4A shows a circuit diagram. In FIG. 4A, AMP1 is an operational amplifier, which holds an output voltage or an output current constant.

The AMP 2 is an operational amplifier which detects a charging current for charging the battery 1 and makes the charging current constant. COMP1 is a comparator, which outputs an L level signal when the charging current for charging the battery 1 is equal to or higher than the reference voltage, and uses AMP1 as negative feedback to control the charging voltage for charging the battery 1 at a constant level. , When the charging current for charging the battery 1 becomes equal to or lower than the reference voltage, an H level signal is output, and A
Negative feedback is provided by the output signal from MP3, and battery 1
The charging current for charging the battery is constantly controlled (see FIG. 5).

FIG. 4B shows the charging voltage when the voltage is constant (indicates the charging voltage when the COMP1 output is at the L level). The charging voltage for charging the battery 1 is initially a constant voltage. The charging voltage at this time is given by the following shown in the circuit diagram of FIG.

[0043] Here, R1, R2, and R3 are resistance values of resistors having the same symbols on the circuit diagram of FIG.

The reference voltage of AMP1 is A in FIG.
It is a reference voltage input to the + terminal of MP1. FIG. 4C shows the charging voltage when the COMP1 output is at the H level (indicates the charging voltage at the constant current). Battery 1
The charging voltage for charging is initially constant voltage, and when it becomes less than a predetermined current, it is switched to a constant current for charging. The charging voltage at this constant current is given by the following shown in the circuit diagram of FIG.

[0045] Here, R1, R2, and R3 are resistance values of resistors having the same symbols on the circuit diagram of FIG.

The reference voltage of AMP1 is A in FIG.
It is a reference voltage input to the + terminal of MP1. The output resistance of AMP2 is the output resistance value at the output end of AMP2 in FIG.

Operation when the circuit of FIG. 4 (a) initially charges the battery 1 at a constant voltage using FIG. 5 and FIG. Will be described in detail.

FIG. 5 is a diagram (No. 2) for explaining the operation of the present invention. This is because the battery 1 is initially charged with a constant voltage, and the battery 1 is charged with a constant current characteristic when the current value becomes equal to or lower than a predetermined current value at the charge switching point. This prevents the harmful effects of overcharging when the battery voltage drops.

Next, the operation of the configuration of FIG. 4 will be described in detail according to the order shown in the flowchart of FIG. 6 with reference to FIG. In FIG. 6, S11 starts charging the battery 1 at a constant voltage.

In step S12, near full charge, switching to constant current charging, which has a slow response, is performed. This is to switch to charging with a constant current characteristic when the charging switching point in FIG. 5, that is, COMP1 in FIG. 4 becomes H level and the charging current becomes equal to or less than a predetermined value.

In step S13, it is determined whether the battery has reached the end of life. This determines whether or not the battery 1 has been used, for example, for three years or more and has reached the end of its life. In the case of NG after the expiration of the life, the operator is prompted to replace the battery 1 in S16, and after the replacement, the process returns to S11 and is repeated. On the other hand, if OK before the expiration of the life period, the process proceeds to S14.

In step S14, it is determined whether a backup operation has occurred due to a power failure. When the backup operation is completed normally, the process returns to S11. On the other hand, in the case of NG, the backup operation cannot be performed in S15, and an ALM (alarm) is displayed and sounded to notify the operator of that fact.

As shown in FIGS. 4 to 6, the battery 1 is initially charged with a constant voltage, and when the battery 1 has a predetermined current value or less, the battery 1 is charged with a constant current characteristic. It has become possible to eliminate the phenomenon that the internal impedance of the battery 1 becomes small and the battery 1 is overcharged and the battery 1 is deteriorated at an early stage.

FIG. 7 shows a block diagram of another embodiment of the present invention. This is when the voltage V changed when the capacitor 1 and the resistor are connected in series to both ends of the battery 1 and the forced discharge circuit 3 causes a current to flow from the battery 1 to the dummy resistor to discharge the voltage V is equal to or more than a threshold value. In addition, the ALM output is sent out by the COMP (comparator) to detect with good sensitivity that one of the cells of the battery including a plurality of cells is defective.

In FIG. 7, the voltage detection circuit 5 is connected to both ends of the battery 1 with a capacitor and a resistor connected in series, and changes when the forced discharge circuit 3 connects a dummy resistor to the battery 1 for forced discharge. When the applied voltage V is equal to or higher than a predetermined threshold value, the ALM is output.

Next, the operation will be described. (1) When the forced discharge circuit 3 is in the open state and is not forcedly discharged, the battery 1 is fully charged by the charging circuit 2 (not shown). In this state, the battery 1 is charged through the capacitor, the resistor R2, and the diode to both ends of the capacitor approximately equal to the voltage of the battery 1.

(2) When the forced discharge circuit 3 is forcibly discharged in the closed state, the battery 1 is forcibly discharged by the dummy resistor, and the voltage of the battery 1 drops. Only this reduced voltage V causes the voltage at the other end of the capacitor, here the side to which the resistors R1 and R2 are connected, to be the reduced voltage V.
Only drops. When this lowered voltage V becomes equal to or lower than the reference voltage of COMP, the ALM output is sent, and it is sent that one of the cells of the battery 1 including a plurality of cells is defective.

[0058]

As described above, according to the present invention,
Floating charging of the battery 1 is performed at a constant voltage, a constant current, or an initial constant voltage and then switched to a constant current to stop when the full charge voltage is reached, or a voltage change amount is extracted by using a capacitor to charge the battery. Since the configuration for detecting the amount of voltage drop is adopted, the battery 1 is always charged with an optimum charging current without being affected by the temperature or the delay of the chemical reaction when the battery 1 is floating-charged, or is composed of a plurality of cells. The voltage drop of the battery can be accurately measured to determine the defective cell.

[Brief description of drawings]

FIG. 1 is a principle block diagram of the present invention.

FIG. 2 is an operation explanatory diagram (1) of the present invention.

FIG. 3 is a flowchart (No. 1) for explaining the operation of the present invention.

FIG. 4 is a configuration diagram of another embodiment of the present invention.

FIG. 5 is an operation explanatory diagram (2) of the present invention.

FIG. 6 is a flowchart (No. 2) for explaining the operation of the present invention.

FIG. 7 is a configuration diagram of another embodiment of the present invention.

FIG. 8 is an explanatory diagram (1) of a conventional technique.

FIG. 9 is an explanatory diagram (2) of the conventional technique.

FIG. 10 is an explanatory diagram (part 3) of the conventional technique.

[Explanation of symbols]

 1: Battery 2: Charging circuit 3: Forced discharge circuit 4: Power supply 5: Voltage detection circuit

Claims (5)

[Claims] 1. A battery charging circuit for charging a battery after discharging the battery every predetermined time and checking the battery voltage, and forcibly connecting a battery (1) to be charged and a dummy resistor to both ends of the battery (1). A forced discharge circuit (3) for discharging and a battery voltage when the forced discharge circuit (3) is forcibly discharged are measured, and when the measured battery voltage is equal to or higher than a threshold value, charging is started to reach a full charge voltage. When the battery level becomes less than the threshold, the battery is stopped (1)
A battery charging circuit, comprising: a charging circuit (2) that repeats the output of the defect of (1) every predetermined time. 2. The battery voltage is measured when the battery (1) is held in a self-discharged state for a predetermined time or more and then discharged by connecting the dummy resistor to eliminate a delay in the chemical reaction and to obtain a rapid battery voltage. The battery charging circuit according to claim 1, wherein 3. The battery charging circuit according to claim 1, wherein the charging is constant voltage charging or constant current charging. 4. Initially constant voltage charging is performed as the charging,
2. The battery charging circuit according to claim 1, wherein the battery charging circuit is switched to constant current charging after a predetermined current or a predetermined time has elapsed. 5. A battery in which a capacitor and a resistor are connected in series to both ends of the battery (1) and the voltage at the connection point between the capacitor and the resistor is changed when the battery is forcibly discharged by the forced discharge circuit (3). The voltage detection circuit (5) according to claim 1, further comprising a voltage detection circuit (5) for measuring V and outputting a signal indicating that the battery (1) is defective when the measured voltage V is equal to or higher than a predetermined threshold value. Battery charging circuit.