JPH1050353A - Charge circuit and charging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent over-charging and perform full charging, in a charge circuit incorporated in an electronic device. SOLUTION: A timer TMR permitted for time counting and counting discharge time of a charge type battery 12 is provided in a duration time in which an operation current is supplied from the charge-type battery 12 to a main circuit 11. Here, when voltage from an external power source 20 is supplied, a circuit 17 decides whether or not the timer TMR has reached a specified value. According to the results of this decision only when the timer TMR reaches the specified value, is a charge current supplied from a charge control circuit 14 to the charge-type battery 12. When the circuit 17 detects full charge of the charge-type battery 12, the charge current to the charge type battery 12 is stopped, and the tamer TMR is initiated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a charging circuit and a charging method suitable for being incorporated in an electronic device.

[0002]

2. Description of the Related Art Portable electronic devices such as portable CD players generally use a rechargeable battery (2) as a power source.
Battery). Some devices have a built-in charging circuit for the rechargeable battery so that they can be charged without removing the rechargeable battery from the device.

[0003]

However, in many cases, even with a charging circuit built in a device, charging of a rechargeable battery is started as it is when an input voltage is supplied from an AC adapter. , The battery may be overcharged.

[0004] Some rechargeable batteries have little problem even if they are slightly overcharged. For example, in the case of nickel-metal hydride batteries, if overcharged, the life is shortened. Further, in a nickel-based rechargeable battery, if the battery is charged while remaining, the effective battery capacity is reduced due to a so-called memory effect.

Accordingly, the terminal voltage of the battery is checked immediately before charging, and charging is performed only when the voltage is below a specified value.
Charging circuits that prevent overcharging have been considered. However, even with such a charging circuit, overvoltage cannot be reliably prevented because the terminal voltage varies due to individual differences between batteries.

[0006] The present invention is to solve the above problems.

[0007]

According to the present invention, there is provided a charge control circuit for forming a charge current of a rechargeable battery from a voltage from an external power supply, and a period during which an operating current is supplied from the rechargeable battery to a main body circuit. A timer for measuring the discharging time of the rechargeable battery, and a detecting means for detecting when a voltage is supplied from the external power supply; and a detecting means for detecting the voltage from the external power supply. A circuit for determining whether or not the timer has reached a specified value when detecting that the battery has been supplied, and a circuit for detecting full charge of the rechargeable battery, wherein the specified value is the rechargeable battery. It is a value corresponding to the time from when the battery is fully charged to when it is necessary to charge the battery.When a voltage is supplied from the external power supply, the circuit that determines the timer causes the timer to reach the specified value. Is The charging control circuit supplies a charging current to the rechargeable battery from the charging control circuit only when the timer has reached the specified value according to the result of the determination. When the full charge is detected, the charging current to the rechargeable battery is stopped, and the timer is initialized.

Therefore, charging is performed only when the rechargeable battery is discharged to a state requiring charging, and
The charge is assumed to be fully charged.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 10 denotes a portable electronic device, for example, a portable CD player.
Reference numeral 20 denotes an AC adapter. In this case, the AC adapter 20 functions as an external power supply of the player 10, and
The commercial AC voltage is converted into a predetermined DC voltage and output to the plug 29. The plug 29 is connected to the power jack 19 of the player 10.

On the other hand, the player 10 has a main body circuit 11 and
And a rechargeable battery 12 for power supply. In this case, the main body circuit 11 is a main part of the player 10, and includes a reproducing circuit and a reproducing mechanism for reproducing an audio signal from a CD. The battery 12 is, for example, a nickel-metal hydride battery, and its output voltage is 2.4V.

Further, the player 10 includes a power supply circuit 13.
And a charge control circuit 14. And the power supply circuit 1
3 has a DC-DC converter and the like (not shown),
The power supply circuit 13 is connected to a switch 15 that is turned on and off in conjunction with a power supply jack 19 to generate an operating voltage required for each circuit of the player 10.

The power supply circuit 13 includes the switch 1
5, the output voltage of the AC adapter 20 and the voltage of the battery 12 are selected and output. When the plug 29 is inserted into the jack 19, the DC voltage from the plug 29 is applied to the main circuit. 11 is supplied as the operating voltage thereof, and a DC voltage which is the charging voltage of the battery 12 is output. When the plug 29 is not inserted into the jack 19, the output voltage of the battery 12 is supplied to the main circuit 11 as the operating voltage. Is what you do.

A switch circuit 1 for a power switch is provided between the power supply circuit 13 and a power supply line of the main body circuit 11.
6 are provided. Further, the charging control circuit 14 converts a DC voltage output from the power supply circuit 13 into a charging current (charging voltage) for the battery 12 and supplies the converted current to the battery 12 during charging.

Further, the player 10 has a microcomputer 17 for system control and various operation keys (operation switches) 18. The microcomputer 17 has various routines for controlling the player 10, and as a part of the routine, for example, a discharge timer routine 100 shown in FIG.
And a charging routine 200. These routines 1
Although details of 00 and 200 will be described later, the routine 100 is executed when the player 10 is set to the reproduction mode or the like, and the routine 200 is executed when the AC adapter 20 is connected to the player 10.

The microcomputer 17 also has a software timer TMR for measuring the discharge time of the battery 12. Further, the microcomputer 17
Is supplied with the operating voltage from the power supply circuit 13, but when the player 10 is not operating, the sleep mode (power down mode) is set to reduce the current consumption.

In such a configuration, when the player 10 is in the stop mode, the microcomputer 17
Is in sleep mode. The switch circuit 16 is turned off by the microcomputer 17. Therefore, as the power source, the battery 14 and the AC adapter 20
Is used, the current consumption is almost 0, that is, the power is off.

However, when, for example, a reproduction key among the keys 18 is pressed, the microcomputer 17 rises from the sleep mode to the normal mode, and the microcomputer 17 turns on the switch circuit 16.
The output voltage of the power supply circuit 13 is supplied to the main circuit 11 via the switch circuit 16 as its operating voltage. Therefore, the player 10 is in the reproduction mode.

In this case, if the AC adapter 20 is connected to the player 10, the DC voltage from the AC adapter 20 is used as the operating voltage of the main body circuit 11 and the microcomputer 17 according to the output of the switch 15. . However, if the AC adapter 20 is
If not, the DC voltage from the battery 12 is used as the operating voltage of the main body circuit 11 and the microcomputer 17 in accordance with the output of the switch 15.

In this case, the microcomputer 100 executes the routine 100 by pressing the reproduction key. That is, the processing of the CPU (not shown) of the microcomputer 17 starts from step 101 of the routine 100, and then, in step 102, the output of the switch 15 is checked.
It is determined whether the battery 12 is used as a power supply.

When the battery 12 is being used, the process proceeds from step 102 to step 103,
In this step 103, the counting of the timer TMR is permitted, and then the processing proceeds to step 104, where the routine 10
Exit 0.

In step 102, the battery 12
Is not used (when the AC adapter 20 is used), the process skips step 103 from step 102, proceeds to step 104, and ends this routine 100.

Further, by operating the key 18,
When the player 10 changes from the stop mode to the operation mode in which the current is consumed similarly to the reproduction mode, the routine 100
Is executed, and when the battery 12 is used as a power source, the timer TMR is permitted to measure time.

Although the processing routine is not shown, when the key 18 is operated to enter the stop mode,
Alternatively, when an operation mode in which no current is consumed, such as the stop mode, is entered, the timer TMR is prohibited from timing.

Therefore, according to the routine 100, when the battery 12 is used, its use time, that is, the battery 1
The discharge time of No. 2 is measured by the timer TMR.

On the other hand, when the plug 29 of the AC adapter 20 is inserted into the jack 19, a routine 200 is executed in the microcomputer 17 according to the output of the switch 15. That is, the processing of the CPU of the microcomputer 17 is performed in step 201 of the routine 200.
And then in step 202, the battery 1
It is checked whether charging of No. 2 is possible.

When it is determined that the battery 12 can be charged, the process proceeds from step 202 to step 203, and in this step 203, the timer TM
It is checked whether the measured discharge time of R exceeds the specified value TLIM. In this case, the specified value TLIM is a value corresponding to the time from when the battery 12 is fully charged to when the battery 12 needs to be charged. That is, it is considered that the current consumption of the player 10 is substantially constant in any operation mode, and when the battery 12 is used based on the average current consumption, the value corresponds to the time when the battery 12 needs to be charged. .

Therefore, when the discharge time measured by the timer TMR exceeds the specified value TLIM, it means that charging is necessary, and the process proceeds from step 203 to step 204. In this step 204, the microcomputer 17 Control signal 1 by the control signal of
4 is controlled so that the charging control circuit 14 supplies a constant current charging current to the battery 12, for example.

Subsequently, the process proceeds to step 205. In this step 205, it is checked whether or not the battery 12 is fully charged. If the battery 12 is not fully charged, this step 205 is repeated, and I will be waiting. In this case, for example, the terminal voltage of the battery 12 is supplied to an A / D converter (analog input port) A / D of the microcomputer 17 through the charge control circuit 14, and full charge is detected from a change in the terminal voltage of the battery 12. . Alternatively, when the charging current is a constant current, full charging is determined from the charging time. Alternatively, both of them are checked at the same time, and when either one shows full charge, it is determined that the battery is fully charged.

When the battery 12 is fully charged, the process proceeds from step 205 to step 206. In this step 206, the microcomputer 17 controls the charge control circuit 14 to terminate the charge. Next, the process proceeds to step 207, in which the timer TMR is initialized.
08, this routine 200 ends.

In step 202, the battery 12
If it is determined that the battery cannot be charged because the battery has been removed, the processing proceeds from step 202 to step 208.
And ends this routine 200. Further, in step 203, when the discharge time measured by the timer TMR does not exceed the specified value TLIM, charging is unnecessary, so the process proceeds from step 203 to step 208, and this routine 200 ends.

Therefore, according to the routine 200, charging is executed only when the battery 12 is discharged to a state requiring charging based on the result of the timer TMR.

Thus, according to this charging circuit, the battery 1
2 is measured, and only when the discharge time reaches a state where the battery 12 needs to be charged, the specified amount of charge is performed. Therefore, the battery 12 is not overcharged. Is not damaged by overcharging or its life is shortened. In addition, since the timing of charging can be appropriately controlled, it is particularly effective when charging is performed with a large charging current, for example, a charging current of 1C.

Further, by charging the battery while there is a remaining amount, the memory effect is not caused and the effective battery capacity is not reduced. Moreover, since charging is performed based on the actual amount of discharge by measuring the discharge time, overcharging can be prevented even if the terminal voltage of the battery 12 varies.

In the above description, when the current consumption greatly differs depending on the operation mode of the main body circuit 11, the timer
The timing speed of the TMR may be changed in proportion to the amount of current consumption. In the above description, whether or not a voltage is supplied from the AC adapter 20 is detected by the switch 15 linked to the jack 19. For example, a detection circuit is connected to the jack 19 and the voltage is supplied from the AC adapter 20. Can also be detected.

[0035]

According to the present invention, the rechargeable battery can be prevented from being overcharged, so that the rechargeable battery is not damaged by the overcharge or its life is shortened.
This is particularly effective when charging is performed with a large charging current.

Further, by charging the battery while there is a remaining amount, there is no possibility that a memory effect is caused and the effective battery capacity is reduced. Moreover, even if the terminal voltage of the rechargeable battery varies, overcharging can be prevented.

[Brief description of the drawings]

FIG. 1 is a system diagram illustrating one embodiment of the present invention.

FIG. 2 is a flowchart illustrating one embodiment of the present invention.

[Description of Signs] 10 CD player, 11 body circuit, 12 rechargeable battery, 13 power supply circuit, 14 charge control circuit, 15 switch for detecting external input, 17 microcomputer, 19 power supply Jack, 20 ... AC adapter, 29 ...
electrical plug

Claims (4)

[Claims] A charge control circuit for forming a charge current of a rechargeable battery from a voltage from an external power supply; and a timer for allowing time measurement during a period in which an operating current is supplied from the rechargeable battery to a main body circuit. A timer for measuring the discharge time of the battery; and a detecting means for detecting when the voltage is supplied from the external power supply; and when the detecting means detects that the voltage is supplied from the external power supply, A circuit for determining whether or not the timer has reached a prescribed value; and a circuit for detecting full charge of the rechargeable battery, wherein the prescribed value is obtained by using the rechargeable battery from a fully charged state. When the voltage is supplied from the external power supply, the circuit for determining whether or not the timer has reached the specified value is determined by the circuit for determining. result Therefore, only when the timer has reached the specified value, the charging control circuit supplies a charging current to the rechargeable battery, and when the detecting circuit detects a full charge of the rechargeable battery, A charging circuit configured to stop the charging current to the rechargeable battery and initialize the timer. 2. The charging circuit according to claim 1, wherein when a voltage is supplied from said external power supply according to a detection result of said detection means, an operating voltage of said main body circuit is formed from said voltage. A charging circuit for supplying to a main body circuit, wherein when no voltage is supplied from the external power supply, an operating voltage of the main body circuit is formed from the voltage of the rechargeable battery and supplied to the main body circuit. 3. A period in which an operating current is supplied from the rechargeable battery to the main body circuit, a timer is permitted to measure time to measure a discharge time of the rechargeable battery, and when a voltage is supplied from an external power supply, The timer determines whether or not the timer has reached a value corresponding to the time from when the rechargeable battery is fully charged to the time when it is necessary to recharge the battery. Only when the value has reached the value, the charging current is formed from the voltage from the external power supply to charge the rechargeable battery. When the charging is fully charged, the charging is stopped and the timer is initialized. Charging method 4. The charging method according to claim 3, wherein when a voltage is supplied from the external power supply, an operating voltage of the main circuit is formed from the voltage and supplied to the main circuit. A method of forming an operating voltage of the main circuit from the voltage of the rechargeable battery and supplying the operating voltage to the main circuit when no voltage is supplied from the rechargeable battery.