KR20060003284A - Charge control device and method for backup battery of portable computer - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a charging control device and method for a backup battery, in particular capable of controlling overcharging and overdischarging of a backup battery.

An apparatus for controlling charging of a backup battery of a portable computer according to an embodiment of the present invention includes a main battery for supplying main power of a system; A backup battery which discharges when the main battery is removed or falls below a predetermined level to supply a power voltage to the load; An overcharge control means connected between the main battery and a backup battery and outputting a signal for controlling the overcharge when a power supply voltage supplied to the backup battery by the main battery is detected as a first voltage level; And an over-discharge control means for blocking the discharge current of the backup battery when the second voltage level is detected after detecting the level of the power supply voltage discharged by the backup battery.

Computer, backup battery, charge, discharge

Description

Charging control apparatus and method of backup battery of portable computer

1 is a block diagram showing a conventional backup battery charging device.

Figure 2 is a block diagram showing a backup battery charging control device according to an embodiment of the present invention.

Figure 3 is a detailed circuit diagram of the present invention Figure 2;

Figure 4 is a view showing the operation of each part of the present invention Figure 3;

5 is a view showing a charge control level of a backup battery according to an embodiment of the present invention.

6 is a flowchart illustrating a charging control method of a backup battery according to an exemplary embodiment of the present invention.

7 is a flowchart illustrating a discharge control method of a backup battery according to an exemplary embodiment of the present invention.

8 is a diagram illustrating a time transition diagram of a backup battery according to an exemplary embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

100 ... AC input 110 ... Main battery charger

120 ... main battery 130 ... backup battery                 

140.Backup battery charger 150 ... First voltage detector

160 ... second voltage detector 170 ... DC-DC converter

180 ... Drive 190 ... Memory

200 ... Supplementary voltage charging part 210 ... Discharge cutoff part

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a charging control device and method for a backup battery, in particular capable of controlling overcharging and overdischarging of a backup battery.

In general, a personal computer is a term referring to a low-cost computer system that is developed for one user and made easy to use for personal office work, education, and entertainment. Personal computers include desktop computers that are placed on a desk according to their size, portable laptop computers that travelers can use on their laps, and thin and small for carrying in a briefcase. Notebook book computers, palm top computers that are smaller enough to fit on the palm of your hand.

On the other hand, a handheld personal computer (HPC), in a narrow sense, refers to a computer the size of a palm with Windows CE as an operating system. In addition, a personal digital assistant (PDA) is a device for inputting information while being carried by a user. A personal digital assistant (PDA) refers to a terminal that operates by using a battery and processes information at a remote location using wireless communication.

Typically, portable computers are powered from a battery to provide portability. When a battery is first made, it has a constant electrical capacity that is determined by the characteristics of the battery. The electrical capacity of a battery is either current or power, which is also known as ampere-hours, which is determined by multiplying the current the battery outputs by the amount of time it can be used. Also called (watt-hour), it is determined by the product of the power the battery can output and the time it can use. Since the power is determined by the product of the current and the voltage, it can be converted between the current and the power, and once the device to use the battery is determined, the other value can be known by measuring only one of the current and the power. This capacitance is the basis for determining how long a battery can last for a given device.

The electrical capacity varies depending on the time of use and the environment. In general, when a battery is used in an electric device, a low battery that is difficult to use the electric device when the electric capacity of the battery is about 5% of the rated electric capacity. ) State. In this case, you need to replace it with another charged battery or recharge the rechargeable battery so that it does not interfere with the use of the electric device. At this time, the criteria of the low battery state may vary depending on the type of electric device and the rechargeable battery used. Electrical devices that require precision, such as portable computers, have strict standards for low battery conditions. Therefore, the portable computer includes a main battery and a backup battery. When the voltage of the main battery falls below a predetermined level, the portable computer receives power from the backup battery and performs a work in a suspended state such as data backup.

The conventional backup battery charger is shown in FIG. 1. As shown in FIG. 1, the backup battery 30 is charged through the main battery 20, and the main battery 10 is charged when AC power is supplied through the main battery charging unit 10.

In addition, when the main battery 20 is discharged or a new battery is to be replaced, the backup battery 30 discharges and supplies a current for a predetermined time to maintain a load, that is, data in the memory.

However, according to the related art, when a portable computer has many tasks to perform in a suspended state or a long duration thereof, a backup battery having a large capacity is required. In addition, there is a problem that the charging operation of the backup battery must be charged through the main battery.

In addition, there is no means to prevent the capacity of the backup battery falls below a certain amount, and when the backup battery is fully discharged, there is an inconvenience of having to charge and discharge 2-3 times for maximum capacity.

It is a first object of the present invention to provide a backup battery charging control apparatus and method for a portable computer which can block current flow from a main battery after charging a backup battery to a predetermined level, that is, a level close to a full charge level.                         

It is a second object of the present invention to provide a backup battery charging control device and method for a portable computer that enables full charging through supplemental charging of a backup battery when an AC adapter or a serial bus (USB) is connected.

A third object of the present invention is to provide an apparatus and method for controlling a backup battery charge of a portable computer which can block a full discharge of a backup battery.

A fourth object of the present invention is a backup battery charge control device of a portable computer, which allows charging of a backup battery via the AC adapter or serial bus (USB) simultaneously with charging of the main battery when the AC adapter or USB is connected. And providing a method.

Backup battery charging control device of a portable computer according to the present invention for achieving the above object,

A main battery for supplying main power to the system;

A backup battery which discharges when the main battery is removed or falls below a predetermined level to supply a power voltage to the load;

An overcharge control means connected between the main battery and a backup battery and outputting a signal for controlling the overcharge when a power supply voltage supplied to the backup battery by the main battery is detected as a first voltage level;

And an over-discharge control means for blocking the discharge current of the backup battery when the second voltage level is detected after detecting the level of the power supply voltage discharged by the backup battery.

Preferably, the overcharge control means is connected between the main battery and the backup battery and a first voltage detector for outputting a high signal when the first level is detected after the level of the power supply voltage supplied from the main battery is higher than the first battery; And a backup battery charger which charges the battery and is turned off by the high signal of the first voltage detector.

Preferably, the over-discharge control means detects a level of the power supply voltage discharged from the backup battery and then outputs a disable signal when a second voltage level is detected, and the power discharged by the backup battery. A DC-DC converter which converts a voltage into a constant DC voltage and supplies it to a load, and is turned off by a disable signal of the second voltage detector, controls charging and discharging of the backup battery, and turns off the DC-DC converter. It characterized in that it comprises a discharge blocking unit for blocking the discharge of the backup battery.

Preferably, when the backup battery is connected to an AC adapter or a serial bus, the backup battery performs a supplementary charging operation up to a full charge level higher than the current charge level.

Preferably, the backup battery performs a trickle charge operation up to a first voltage level.

On the other hand, the backup battery charge control method of a portable computer according to the present invention,                     

Charging a backup battery with a power supply voltage supplied from a main battery when power is supplied to the system;

After the charging step, cutting off the current supplied from the main battery to the backup battery when the charge level of the backup battery becomes higher than a reference high level;

And after the current blocking step, supplementing and charging the backup battery to a reference high level or higher when an external supplemental power is supplied.

Preferably, when the main battery is removed, discharging the backup battery to supply to the load; And disabling the discharge operation of the backup battery when the discharge level of the backup battery is lower than the reference low level when the backup battery is discharged.

Preferably, the backup battery is trickle-charged to a first voltage level, and fast charging is performed during supplementary charging.

Hereinafter, a backup battery charge control apparatus of a portable computer system according to the present invention will be described with reference to FIG. 2.

Referring to FIG. 2, an AC input unit 100 that supplies an AC power voltage, a main battery charging unit 110 that receives an AC power input from the AC input unit 100, and charges the main battery 120 with the main battery 120. A backup battery charging unit 140 connected to an output terminal of the battery 110 to charge the backup battery 130 with the power voltage discharged from the main battery 120, and a power supply voltage discharged from the main battery 120. The first voltage detector 150 turns off the backup battery charger 140 when the level is detected and reaches the first voltage level, and detects a power supply voltage discharged from the backup battery 130 when the main battery is removed. When the level is detected, the second voltage detector 160 outputting the disable signal, the DC-DC converter 170 supplying a power voltage supplied from the batteries 120 and 130 at a constant DC level, and the DC-DC converter ( 170) The supplementary voltage charging unit 200 which replenishes and charges the backup battery 130 for full charging using the driving unit 180 for switching and outputting the DC level to the memory 190 and the power voltage input from the AC input unit 100. And a discharge blocking unit 210 for blocking the discharge of the backup battery 210.

The charging control device for a portable computer according to an exemplary embodiment of the present invention configured as described above will be described with reference to the accompanying drawings.

First, referring to FIG. 2, the main battery charger 110 is a charger and receives AC power to supply the main battery to charge the main battery 120. The main battery 120 may be removed or mounted from the system.

The backup battery charger 140 charges the backup battery 130 through the discharge blocking unit 210 using the power voltage charged from the main battery 120.

Here, the backup battery 130 uses Ni-MH or Ni-cd and the like, and a method for charging includes a method of fast charge and trickle charge. In this case, the full charge voltage of the battery becomes high and the battery can be charged in a short time. The trickle charging method takes a low voltage and takes a long time to charge when fully charged.                     

The first voltage detector 150 detects the charging voltage supplied from the main battery 120 to the backup battery 130, and when the first voltage is higher than or equal to the reference high level, that is, the first voltage is greater than or equal to the first voltage, the backup battery charging unit 140 is detected. Off Here, when the capacity charged in the backup battery 140 is above a certain level, the state is charged up to a level near a full charge, and a lot of time is consumed and current consumption occurs to charge to the full charge level. . That is, the backup battery performs trickle charge up to the first voltage level.

To this end, the first voltage detector 150 detects the first voltage and turns off the backup battery charger 140 when the backup battery is charged to a predetermined voltage or more, thereby preventing the overcharge current flowing into the backup battery 120. Block it. Accordingly, damage to the main battery 130 is prevented.

Here, as shown in FIG. 5, when the charging capacity of the backup battery 130 is charged using the main battery in a normal charging state, the first battery Vh is charged by trickle charging and charged to the first voltage. Blocks the backup battery from charging anymore. For example, the first voltage level Vh is 1.38V and the full charge voltage Vf is 1.42V.

 Meanwhile, since the backup battery 120 is not yet fully charged but is charged to the first voltage level, the backup battery 120 cannot fully utilize the battery capacity.

To this end, the supplementary voltage charging unit 200 is connected to the charging circuit, and the AC power input from the AC input unit 100 is supplemented to the backup battery 130 via the discharge blocking unit 130 through the supplementary voltage charging unit 200. Charge with Supplementary charge. At this time, the backup battery 130 is fully charged by performing a quick charge. Here, the supplementary voltage charging unit 200 includes any one of an AC adapter or a serial bus (USB).

Meanwhile, when the main battery 120 is discharged and the backup battery 130 is also discharged, the power supply voltage supplied from the AC input unit 100 may supply the main battery charging unit 110 and the supplementary voltage charging unit 200. Both batteries can be charged simultaneously.

As such, the main battery 120 supplies a normal power supply voltage to the system. In this case, when the main battery 120 is below a predetermined voltage or removed to replace the main battery 120, the backup battery 130 starts discharging to supply power to the system.

The power supply voltage discharged by the backup battery 130 is converted into a constant DC voltage by the DC-DC converter 170 via the discharge blocking unit 130, and is switched by the driving unit 180, thereby outputting the load-side memory. Supply the required DC voltage to 190.

Thereafter, the second voltage detector 160 detects a power supply voltage discharged from the backup battery 130 and outputs a signal to turn off the DC-DC converter 170 when the second voltage VL level is detected. As the DC-DC converter 170 is turned off and the driver 180 is turned off, the input terminal of the memory 190 becomes a low level. Here, the second voltage V _L is, for example, about 0.9V.

The voltage supply to the memory 190 is cut off and the discharge blocking unit 210 is turned off to prevent over discharge of the backup battery 130. As the discharge blocking unit 210 is turned off, the current discharged from the backup battery 130 is cut off.

Here, as shown in FIG. 5, since the capacity of the backup battery is prevented from being over-discharged below a predetermined voltage (V _L ), the performance of the backup battery is prevented, and the self-capacitance is restored during charging after full discharge. To solve the problem of self discharging that performs two to three charges and discharges for retention.

3 is a circuit configuration diagram of a charging control device for a backup battery of a portable computer, and FIG. 4 is a state diagram of each part of FIG. 3.

As shown in FIG. 3 and FIG. 4, the charging operation of the backup battery is as follows. The main battery 120 is charged through the main battery charger 110. The backup battery charger 140 charges the backup battery 140 by turning on the first switching device Q1 by the power voltage supplied from the backup battery 120.

Here, the first switching element Q1 is a P-ch FET whose source S and gate G stages are connected to each other. The gate terminal of the first switching element Q1 receives a low signal, which is an output P1 of the first voltage detector 150, and is turned on. The output voltage of the first switching element Q1 is a diode ( After rectifying through D13, the backup battery 130 is charged by turning on the second switching element Q2 and the third switching element Q3 of the discharge blocking unit 210.

As such, the charging operation of the backup battery 130 is performed when the system is operating normally, that is, supplying all power or in the suspend mode. Therefore, by supplying power to each part of the system from the main battery 120, power is always supplied to the memory 130.

When power is supplied to the memory 130, the gate terminal of the third switching element Q3 becomes the high signal H. When the third switching element Q3 switches, the second switching element Q2 is turned on. It is on. Through this, the backup battery 130 may be charged and discharged.

If the backup battery 130 is not a condition to be charged, the power is not supplied to the backup battery 130, and thus the backup battery 120 may never be discharged because there is no power in the memory 190. However, a portable computer system such as a PDA has a memory (no matter what) except for a power off (e.g., 3 Burton reset) and a full discharge of the main battery 120 due to a natural discharge and a full discharge of the backup battery 130. 190 is powered. Therefore, the second switching element Q2 is not turned off when the power is supplied to the memory 190.

Meanwhile, when the high voltage detect operation is performed, the first voltage detector 150 detects a power supply voltage charged in the backup battery 130 and outputs a low signal when the first voltage Vh is less than or equal to the first voltage Vh. 1 Turn on the switching element Q1.

However, when the capacity of the backup battery 130 is greater than or equal to a certain level, the voltage detected by the first voltage detector 150 exceeds the first voltage VH. At this time, the first voltage detector 150 outputs a high signal to the output terminal P1 to turn off the first switching element Q1, and when the first switching element Q1 is turned off, the first voltage detector 150 backs up from the main battery 120. The charging current flowing to the battery 130 is cut off.

In addition, when the backup battery 130 is charged to a predetermined voltage level, when the user mounts an AC adapter or connects a serial bus (USB) to charge the main battery 120, the main battery 120 is the main battery. Charging is performed through the charging unit 110. In this case, a power supply voltage is supplied through an AC adapter or a serial bus (USB) of the supplemental voltage charging unit 200 to charge the backup battery 130 through the discharge blocking unit 210.

In this case, as illustrated in FIG. 5, the backup battery 130 starts replenishment charging at the first voltage Vh to perform fast charging up to the full charge Vf state.

Here, when the system is operating normally, power is supplied from the main battery 120 to the memory 190, and the power from the backup battery 130 is supplied to the switching elements Q4 and Q5 of the driving unit 180. Is blocked by.

That is, the output of the backup battery 130 is supplied to the output of the DC-DC converter 180, and the output terminal of the DC-DC converter 180 is the source S of the fourth switching element Q4 of the driving unit 180. The source terminal and the gate terminal of the fourth switching device Q4 are connected to each other. Accordingly, in a situation where the system is normally operated by the main battery 120, a low signal is applied to the gate terminal of the fifth switching element Q5 to turn off the fourth switching element Q4.

However, when the main battery 120 is replaced, the driving unit 180 turns on / off the switching elements Q4 and Q5 by the control signal CTL. In this case, the fifth switching element 180 is turned on. A high signal (CTL = high) is applied to the gate terminal of the fifth switching element (Q5) is turned on, the fourth switching element (Q4) is turned on by the fifth switching element (Q5) drive unit 180 Output P4 is applied with a high signal, and the third switching element and the second switching element of the discharge blocking unit 210 are turned on by the output high signal of the driving unit 180, so that the DC-DC converter 180 is turned on. The voltage of the backup battery 130 is applied to the output P3 of the. Here, the fourth switching element Q4 is composed of a P-ch FET, and the fifth switching element Q5 is composed of an N-ch FET.

On the other hand, when the main battery 120 is less than or equal to one voltage (swap), the backup battery 130 discharges a predetermined voltage through the DC-DC converter 170 through the discharge blocking unit 210. If this situation persists for a long time, the voltage of the backup battery 130 will drop in stages.

Here, when the second voltage detector 160 detects the discharge voltage of the backup battery 130 and the discharge voltage is less than or equal to the second voltage VL, the output P2 of the second voltage detector 160 is a DC-DC converter. The low signal L for disabling the 170 is output. Then, the DC-DC converter 170 is turned off by the disable signal, the output P3 of the DC-DC converter 170 is at a low level, the driver 180 is turned off, and the driver 18 is Since the output terminal P4 of the transistor becomes the low level L, the gate terminal of the third switching element Q3 of the discharge blocking unit 210 falls to the low level.

Accordingly, the third switching element Q3 of the discharge blocking unit 210 is turned off. When the third switching element Q3 is turned off, the gate terminal and the source terminal of the second switching element Q2 are turned off. The second switching element Q2 is turned off because the high level state is connected to each other. Accordingly, the backup battery 130 is discharged. Here, the second switching element Q2 is composed of a P-ch FET, and the third switching element Q3 is composed of an N-ch FET.

Accordingly, when the backup battery 130 is below a predetermined voltage (VL) as shown in FIG. 5, the backup battery 130 blocks further discharge from the backup battery 130 as the discharge blocking unit 210 is turned off, thereby backing up the backup battery 130. This prevents the battery 130 from being completely discharged.

6 is a flowchart illustrating a charging control method of a backup battery according to the present invention.

Referring to FIG. 6, when power is supplied to the portable computer system (S101), the charging voltage level Vc of the backup battery is detected, and the charging voltage level is compared with a preset reference low level V _L ( S103). As a result of the comparison of S103, when the charge level of the backup battery is higher than or equal to the reference low level, trickle charge is performed (S105).

During the trickle charging of the backup battery, it is compared whether the voltage level Vc charged in the backup battery is greater than or equal to a preset reference high level V _H (S107). As a result of the comparison of S107, when the charged voltage level Vc is higher than or equal to the reference high level, the trickle charging of the backup battery is stopped (S117). If the charged voltage level Vc is lower than or equal to the reference high level, the trickle charging is continued (S109).

When the supplementary power is supplied through the AC adapter or the serial bus (USB) after the trickle charge of the backup battery is stopped (S119), the supplementary charging is performed (S113), and the full charging operation of the backup battery is terminated. (115).

In addition, when the supplementary power is supplied through the AC adapter or the serial bus even during trickle charging of the backup battery (S111), the supplementary charging operation is performed to perform the charging operation to a full charge level in a shorter time (S113, S115). Here, the replenishment charging operation is a quick charging operation, which is largely different from the trickle charging.

7 is a flowchart illustrating a discharge control method of a backup battery according to the present invention.

Referring to FIG. 7, when power is supplied to the portable computer, it is checked whether the supplementary voltage is supplied (S123). When the replenishment power is supplied as a result of the checking of S123, replenishment charging is performed to complete the full charging (S125 and S127).

As a result of the checking in step S123, if the supplementary power is not supplied, the trickle charging is performed using the power supply voltage supplied from the main battery when the voltage level charged in the backup battery is equal to or higher than the preset reference low level (V _L ) (S131, S129). ). At this time, after confirming that the main battery has been removed, if the main battery is removed (Exclusion), the backup battery starts to discharge (S133, S135), and when the main battery is installed, the backup battery performs trickle charging again (S137). , S139).

However, as a result of checking in S133, when the main battery is not removed and the backup battery is trickle charged, the charging voltage of the backup battery is detected and the currently charged voltage is compared with a preset reference high level (S141). At this time, as a result of the comparison of S141, if the charging voltage of the backup battery is lower than the reference high level, after confirming whether the supplementary power is supplied (S147), and performing supplementary charging when supplementary power is supplied (S125). As a result of S147, when the supplemental power is not supplied, the trickle charge is continued to the reference high level V _L (S131).

When the charging voltage of the backup battery exceeds the reference high level, the comparison result of S141 confirms whether the supplementary power is supplied (S143). When the supplementary power is supplied, supplementary charging is performed, and if the supplementary power is not supplied, the main battery is supplied. After checking whether or not the (S145), if the main battery is removed, the process proceeds to step S135 and the backup battery is discharged (S145).

8 is a state transition diagram of a backup battery according to the present invention.

Referring to FIG. 8, in the normal charging state 300 of the backup battery, the charging completion state 310 is charged to a reference high level by the power voltage supplied from the main battery (S301), and when the main battery is removed ( S305) The backup battery is in the discharge state 330.

When the charging voltage of the backup battery is high voltage detection state 310, when an AC adapter or a serial bus (USB) is installed (S302), the charging state of the backup battery is 320, and when the main battery is replaced in the supplementary charging state. Proceeding to the discharge state 330 (S303).

In addition, when the charging voltage of the backup battery is a high voltage detection state 310, the main battery is immediately discharged when the main battery is replaced.

In the discharge state 330 of the backup battery, when the discharge continues (S306), the discharge state 340 is discharged to the reference low level. In this state, when the AC adapter or the serial bus is installed in the reference low level state or the main battery is replaced (S328), the charging proceeds to the normal charging state 300 through this.

However, when the backup battery is discharged while the reference low level is detected, the discharge state is a self discharge state 350, and when the AC adapter or the serial bus is installed or the main battery is replaced (S328), the battery proceeds to the normal charging mode. do.

As described above, in the present invention, the backup battery performs a constant charging operation to the reference high level while the main battery is operating, and when the reference high level is reached, cuts off the electrical circuit between the main battery and the backup battery, and after a predetermined time, the supplementary power supply. At this point in time, the battery is fully charged, thereby minimizing battery damage.

Then, the backup battery can be prevented from being completely discharged.

So far, the present invention has been described with reference to the preferred embodiments, and those skilled in the art to which the present invention pertains to the detailed description of the present invention and other forms of embodiments within the essential technical scope of the present invention. Could be implemented. Here, the essential technical scope of the present invention is shown in the claims, and all differences within the equivalent range will be construed as being included in the present invention.

As described above, the present invention provides a charging control device and method for a portable computer, in order to reduce the current consumption of the main battery, the backup battery stops charging when the charging level rises to a certain level, thereby reducing the current consumption of the main battery and reducing the effective time of the main battery. There is an effect that can increase.

In addition, when the backup battery reaches a certain low level, it completely blocks the discharge, thereby preventing the discharge by blocking the leakage current of the battery which is not used by the PDA.

In addition, it is possible to charge the main battery and the backup battery at the same time using the external charging unit.

Claims (8)

A main battery for supplying main power to the system; A backup battery which discharges when the main battery is removed or falls below a predetermined level to supply a power voltage to the load; An overcharge control means connected between the main battery and a backup battery and outputting a signal for controlling the overcharge when a power supply voltage supplied to the backup battery by the main battery is detected as a first voltage level; And an over-discharge control means for disconnecting the discharge current of the backup battery when a second voltage level is detected after detecting the level of the power supply voltage discharged by the backup battery. . The method of claim 1, The overcharge control means is connected between the main battery and the backup battery and a first voltage detector for outputting a high signal when the first level is higher than the first level after detecting the level of the power supply voltage supplied from the main battery to charge the backup battery And a backup battery charging unit which is turned off by a high signal of the first voltage detection unit. The method of claim 1, The over-discharge control means detects the level of the power supply voltage discharged from the backup battery, and when a second voltage level is detected, a second voltage detector for outputting a disable signal and a power supply voltage discharged by the backup battery. A DC-DC converter which is converted to a DC voltage and supplied to a load, and is turned off by a disable signal of the second voltage detector, and controls charging and discharging of the backup battery and a backup battery due to the DC-DC converter being turned off. The backup battery charging control device of a portable computer, characterized in that it comprises a discharge blocker for blocking the discharge of. The method of claim 1, When the backup battery is connected to an AC adapter or a serial bus, the backup battery charge control device of a portable computer, characterized in that the supplementary charging operation to a full charge level higher than the current charge level. The method of claim 1, And the backup battery performs a trickle charging operation to a first voltage level. Charging a backup battery with a power supply voltage supplied from a main battery when power is supplied to the system; After the charging step, cutting off the current supplied from the main battery to the backup battery when the charge level of the backup battery becomes higher than a reference high level; And after the current blocking step, supplementing and charging the backup battery to a reference high level or higher when an external supplemental power is supplied. The method of claim 6, Discharging the backup battery and supplying the load to the load when the main battery is removed; And disabling a discharge operation of the backup battery when the discharge level of the backup battery is less than or equal to the reference low level when the backup battery is discharged. The method of claim 6, And trickle charge the backup battery to a first voltage level, and perform charging with fast charging from the first voltage level to a full charge.

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