JP2002354694A - Electronic device having battery charger function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent discharge of a secondary battery in an electronic device having a battery charger function, even if the device is operated during charging the battery. SOLUTION: The secondary battery is charged with a charging current flowing into it, via a diode 3, a switch 4 and a current detecting means 5, when an external power supply is connected to an external power-supply input terminal 2. A control means 8, monitoring the charging current, switches off the switch 4, when the secondary battery 1 is in a fully charged condition, and the charging current becomes a predetermined value or less. When the switch 4 is switched off, discharge of the secondary battery is blocked, since the external power supply and the secondary battery are electrically separated. Consecutively, when the external power supply is connected, the external power supply is made to a load 7 and the control means 8 via a regulator 6, and the fully charged condition of the secondary battery is maintained without discharging it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable telephone, an information terminal, and other electronic devices having a charging function provided with a rechargeable secondary battery.

[0002]

2. Description of the Related Art Generally, electronic devices such as portable telephones and information terminals use a secondary battery as a power source and have a charging function.

FIG. 4 is a block diagram of a conventional mobile phone having a conventional charging function. In FIG. 4, when the secondary battery 1 is charged, an external power source obtained by a known power adapter, charging stand, vehicle-mounted connector, or the like (not shown) is connected to the input terminal 2 of the external power source.

When an external power supply is connected to the input terminal 2, a charging current flows from the external power supply to the secondary battery 1 via the diode 3, the switch means 4, and the current detection means 5, and the charging of the secondary battery 1 is started. You. That is, the switch means 4
It is controlled by the control means 8 and is initially in the ON state.
Therefore, when an external power source is connected, a charging current flows from the external power source to the secondary battery 1 via the switch means 4 and the current detecting means 5, and the charging of the secondary battery 1 is started. While the secondary battery 1 is being charged, the current detecting means 5 detects the charging current, and the control means 8 operates so that the switch means 4 is kept ON by the output.

When the charging of the secondary battery 1 is completed, it is detected by the current detecting means 5 and the switch means 4 is turned off.
Thereafter, only the charged voltage of the charged secondary battery 1 is used as a power source for the load 7 and the control circuit 8 constituting the electronic device via the regulator 6.

As described above, even in a conventional electronic device with a charging function, by connecting an external power supply to the input terminal 2,
The secondary battery 1 is charged, and the load 7, the control means 8, and the like constituting the electronic device can be operated using the charged voltage.

[0007]

However, in the above-mentioned conventional electronic equipment with a charging function, the switch 6 is connected to the secondary battery 4 side, that is, the connection point between the current detecting means 5 and the secondary battery 1 via the regulator 6. Thus, even if the secondary battery 1 is charged and the switch means 4 is completely turned off, the secondary battery 1 is directly supplied to the control means 8 through the regulator 6. The secondary battery 1 is connected to the load 7 and the control means 8 and starts discharging immediately after charging.

Therefore, these electronic devices have a problem that even after charging is completed, discharging starts immediately thereafter, and after a certain period of time, only a certain voltage is applied, and charging has to be performed again. .

This is the same even when the external power supply is kept connected to the input terminal 2. Therefore, in this case, the charge and discharge are repeated at regular intervals. Even if the device is charged on a charging stand or the like for a long time, a considerable discharge is performed at the timing when the device is taken out from the charging stand. there were.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide an electronic device having an excellent charging function which is very rarely automatically discharged after charging is completed. It is assumed that.

[0011]

According to the present invention, in order to achieve the above object, according to the first aspect of the present invention, a load, a control means, and the like constituting an electronic device are connected to an external power supply side of a charging switch means. It was configured to be. Therefore, when the charging is completed and the switch means is turned off, the secondary battery is not automatically discharged thereafter through the load, the control means, etc., and can be used at any time in a sufficiently charged state.

According to the present invention, a detecting means for detecting a current flowing in the secondary battery during charging is provided, and when the completion of charging of the secondary battery is detected based on an output of the detecting means, The charging switch is turned off. Therefore, the completion of charging can be accurately detected by the output of the detecting means for detecting the current flowing through the secondary battery during charging, and the charging can be stopped.

Further, according to the third aspect of the present invention, an external power supply detecting means for detecting the power supply of the external power supply is provided, and when the power supply detecting means detects that there is no power supply by the external power supply, the switch means is forcibly activated. It is configured to be a means to be turned on. Therefore, when there is no power supply from the external power supply, the switch means is forcibly turned on, and the load and control means constituting the electronic device are supplied with power accurately using the secondary battery as a power supply.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.

(First Embodiment) In a first embodiment of the present invention, an external power source is connected to a secondary battery when charging is turned on, an external power source is turned off when charging is completed, and when the external power source is disconnected. This is an electronic device with a charging function that is provided with switch means for turning on and supplies power to a load from a connection point between the external power supply and the switch means.

FIG. 1 is a functional block diagram of an electronic device with a charging function according to a first embodiment of the present invention, and FIG. 2 is an explanatory diagram of the operation of the electronic device.

In FIG. 1, an input terminal 2 of an external power supply is
It is connected to the secondary battery 1 via a backflow preventing diode 3, a switch means 4, and a current detection means 5. A regulator 6 is connected to the external power supply side of the switch means 4, that is, a connection point between the diode 3 and the switch means 4. Is supplied as power.

On the other hand, the output of the current detecting means 5 is supplied to the control means 8, and the output of the control means 8 is supplied to one input terminal of the NOR circuit 9. External power supply input terminal 2
External power supply detecting means 1 via a diode 10
1 is connected, and the output is supplied to the other input terminal of the NOR circuit 9 via the inverter 12.

The switch means 4 is composed of a MOS-FET, a diode, or the like, and is turned ON or OFF by an output signal of the control means 8 supplied through the NOR circuit 4.
It is configured to change to N and OFF states, respectively.

The current detecting means 5 is composed of a resistor having a relatively small value connected between the switch means 4 and the secondary battery 1 and means for monitoring the voltage across the resistor. The control means 8 directly detects the voltage of the secondary battery, and turns on the switch means 4 according to the detection result and the current detection result of the current detection means 5 as described later.
It is configured to output a signal for changing to three states of half ON and OFF.

In the first embodiment, when an external power supply is connected to the external power supply input terminal 2, the external power supply input terminal 2 is connected to the secondary battery 1 via the diode 3, the switch means 4, and the current detection means 5. Charging current flows. At this time,
The switch means 4 is controlled as follows under the control of the control means 8.

That is, it is assumed that a lithium ion battery is used as the secondary battery 1 and is charged. In this case, usually, the external power supply applied to the input terminal 2 is set to 5.
A battery of 8 V or more is used.
It is necessary that the battery voltage does not exceed 4.2V. When a lithium ion battery is used as the secondary battery 1, it is necessary to prevent the charging current from exceeding 700 mA. The switch means 4 is set to a half ON state so as to satisfy such a condition. Controlled.

FIG. 2 shows this state. When the voltage of the secondary battery 1 is extremely low, the control
And a signal having a value sufficient to turn on the switch means 4 is output from the control means 8. Therefore, in this state, the switch means 4 is completely turned on, and a relatively large charging current flows through the rechargeable battery 1. Charging advances 2
When the voltage of the secondary battery 1 gradually increases, the value of the signal output from the control means 8 gradually decreases accordingly, and the switch means 4 is half-ON, and charging is performed in this state. As charging proceeds, the voltage of the secondary battery 1 increases, and the charging current flowing through the secondary battery gradually decreases accordingly.

The charging current flowing through the secondary battery 1 is detected by the charging current detecting means 5 and applied to the control means 8. Here, the resistance constituting the charging current detecting means 5 is 0.1
If a 5 Ω resistor is used, the voltage across the
If it is mV, it means that a charging current of 1 A flows. Therefore, by detecting the voltage across the resistor, the charging current flowing through the secondary battery 1 can be accurately known.

The control means 8 controls the secondary battery 1 in this manner.
Also, when the charging current drops to a certain value, for example, 50 mA, this is sensed and the switch means is controlled to the OFF state.

As described above, when the charging is completed and the switch means 4 is turned off, the charging current no longer flows, and the external power supply and the secondary battery 1 are completely separated. Therefore, in this state, the charge charged in the secondary battery 1 is hardly consumed by the load 7 and the control means 8 via the switch means 4 and the regulator 6. Conversely, if an external power supply is connected to the input terminal 2 in this state, the required power is supplied from the external power supply input terminal 2 to the load 7 and the control means 8 as they are.

The switch means 4 is connected to the M as described above.
It is composed of OS-FET, diode, etc.
In some cases, the state of the FF cannot be obtained, but even in this case, when an external power supply is connected to the input terminal 2, the potential on the input side of the regulator 6 may be lower than the potential of the secondary battery 1. Is impossible, so even in this state, 2
The electric charge charged in the secondary battery 1 is not consumed by the load 7 and the control means 8 via the switch means 4 and the regulator 6, and the necessary power is supplied only from the external power input terminal 2. Therefore, at any time until the electronic device is removed from the charging stand and disconnected from the external power supply,
The secondary battery can be kept fully charged.

Next, the electronic device is removed from the charging stand or the like,
When disconnected from the external power supply, this is
And its output is applied to the other input terminal of the NOR circuit 9 via the inverter 12. Therefore, regardless of the control signal applied from the control means 8 to one input terminal of the NOR circuit 9, the switch means 4 is forcibly turned on, and the electric charge charged in the secondary battery 1 is switched. The power is applied to the load 7 and the control means 8 via the means 4 and the regulator 6.

In the above embodiment, a lithium ion battery is used as a secondary battery. However, the present invention can be similarly applied to a nickel hydrogen battery or another secondary battery. Further, although the current detecting means 5 is provided on the secondary battery 1 side of the switch means 4, it may be provided on the external power supply side. In short, 2
It is sufficient to provide the battery at a position where the charging current to the secondary battery 1 flows.

(Second Embodiment) In the first embodiment, when the external power is not applied, the external energization detecting means 11 is separately provided to detect the external power. In the second embodiment, the control means 8 itself is provided with means for detecting the state of application of the external power.

FIG. 3 is a functional block diagram of an electronic device with a charging function according to the second embodiment of the present invention. FIG.
In the figure, the components denoted by the same reference numerals as those in FIG. 1 indicate the same components as those in FIG. The difference is that a diode 13 is connected to the external power supply 2 and its output side is connected to the control means 8,
The point is that the control means 8 directly detects connection / disconnection of the external power supply. Even in such a configuration, it is easy to forcibly turn on the switch means 4 under the control of the control means 8 when the external power supply is not connected.

In the second embodiment shown in FIG.
Although information as to whether or not an external power supply is connected to the control means 8 is input via the diode 13, the information is applied to the control means 8 even if there is no special route having such a diode 13. If the power supply voltage to be supplied is closely monitored, as in the second embodiment, under the control of the control means 8, when the switch means 4 is not connected to the external power supply, the switch means 4 is forcibly forced. It can be configured to be turned on.

That is, when an external power supply is connected, the power supply voltage applied to the control
Since the voltage is applied through the diode 3 and the regulator 6, a sufficient power supply voltage is applied. On the other hand, when the external power supply is not connected, only the power supply from the secondary battery 1 is received, so that the voltage is slightly lower than when the external power supply is connected. Therefore, if the control means 8 detects this voltage difference, the control means 8 can easily detect whether or not an external power supply is connected.

Therefore, if it is detected from the detection result that the external power supply is connected, the output of the current detection means 5 causes the control means 8 to turn the switch means 4 from ON to half ON and OFF. If it is detected that the external power supply is no longer connected, the control means 8 may automatically turn on the switch means 4.

Further, in the above embodiment, the current detecting means 5 is constituted by the resistance and the means for detecting the voltage between both ends, so that the secondary battery 1 is kept as it is even when the external power supply is not connected.
However, when an external power supply is not connected, both ends of the current detecting means 5 may be automatically short-circuited.

With this configuration, when the external power supply is not connected, the switch 4 and the regulator 6 are connected without the voltage of the secondary battery 1 being dropped by the resistor constituting the current detecting means. The voltage is efficiently applied to the load 7 and the control unit 8 through the control unit 8.

[0037]

As described above, according to the present invention,
When charging, an external power supply is connected to the secondary battery via the charging switch means, and a load constituting the electronic device is connected to the external power supply side of the charging switch means. If the switch means is turned off,
Thereafter, the secondary battery is hardly inadvertently discharged through the load, the control means, and the like, and can be used at any time in a sufficiently charged state.

Further, detecting means for detecting a current flowing to the secondary battery during charging, and when the completion of charging of the secondary battery is detected based on an output of the detecting means, the charging switch means is turned off. Since the control means for controlling the charging switch means is provided, the completion of the charging can be accurately detected by the output of the detecting means for detecting the current flowing through the secondary battery during charging, and the charging can be stopped.

Further, according to the present invention, the external energization detecting means for detecting the energization of the external power supply, and the switch means is forcibly turned ON when the detection means detects that there is no energization by the external power supply. And the means,
The switch means is forcibly turned on when the external power supply detecting means detects that no power is supplied from the external power supply. Therefore, when the electronic device is disconnected from the external power supply, the switch means is always turned on and the secondary power supply is turned on. By using a battery as a power source, it is possible to always accurately supply current to the load and the control means constituting the electronic device.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of an electronic device with a charging function according to a first embodiment of the present invention;

FIG. 2 is an operation explanatory diagram of the electronic device with a charging function according to the first embodiment of the present invention;

FIG. 3 is a functional block diagram of an electronic device with a charging function according to a second embodiment of the present invention;

FIG. 4 is a functional block diagram of a conventional electronic device with a charging function.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Secondary battery 2 External power supply input terminal 3 Diode for backflow prevention 4 Switching means 5 Current detection means 6 Regulator 7 Load 8 Control means 9 NOR circuit 10 Diode 11 External conduction detection means 12 Inverter

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5G003 AA01 BA01 CA03 CA04 CA14 CC02 DA04 DA13 5H030 AS11 BB01 BB27 FF42 FF43

Claims (4)

[Claims] 1. An electronic device with a charging function wherein an external power supply is connected to a secondary battery via a charging switch means during charging, and a load constituting an electronic device is connected to the external power supply side of the charging switch means. . 2. A detecting means for detecting a current flowing through the secondary battery during charging, and a means for turning off the charging switch means when completion of charging of the secondary battery is detected based on an output of the detecting means. The electronic device with a charging function according to claim 1, further comprising: 3. An external power supply detecting means for detecting the power supply of the external power supply, and means for forcibly turning on the switch means when the detection means detects that there is no power supply by the external power supply. The electronic device with a charging function according to claim 2, characterized in that: 4. The electronic device with a charging function according to claim 3, wherein said control means includes means for forcibly turning on said switch means.