JPH04205120A - Portable electronic device - Google Patents

Abstract

PURPOSE:To prevent the usable capacity of a battery from decreasing by completely discharging the battery when the chargeable battery voltage drops below a constant value, and then charging the battery. CONSTITUTION:When the voltage of the Ni-Cd battery constituting the battery 11 drops below the constant value, a CPU 10 controls a discharge control circuit 13 in response to an operator's instruction to turn ON a transistor TR. Consequently, a discharging circuit 12 conducts, so the battery 11 begins to be discharged and its discharging current flows to a resistance R. When the battery 1 is completely discharged, the CPU 10 controls the discharge control circuit 13 in response to an operator's indication to turn OFF the transistor TR, so that the discharging of the battery 11 is stopped. Then the battery 11 is charged for reuse. Thus, the battery 11 is completely discharged to suppress memory effect and the usable capacity after charging is prevented from decreasing.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a portable computer powered by a rechargeable battery, such as a portable computer, desktop type or desktop word processor. related to type electronic devices.

(Prior Art) As a rechargeable battery, for example, a Ni--Cd (nickel-cadmium) battery is used to drive the above-mentioned portable electronic device.

Since it is inevitable for such battery-powered portable electronic devices to gradually decrease the battery voltage, they can be driven by repeated charging. This charging cycle is
Although the battery can be used for one to several days with one charge, in many cases, the battery is charged once a day, regardless of the actual usage time. In other words, batteries are increasingly being used while repeatedly shallowly discharging and charging.

Furthermore, when using such a battery, it is necessary to constantly detect this voltage and know the extent of the voltage drop. FIG. 7 shows an example of a detection circuit used for this purpose.
A parallel circuit of a first voltage detecting element 8 and a second voltage detecting element 9 made of C or the like is connected, and each element 8.9 monitors the battery voltage at a certain voltage point.

This prevents the battery from being depleted to the point where it is over-discharged and cannot be recharged, and measures such as issuing a warning to the user are taken when the battery voltage falls below a certain value.

Measures have also been taken, such as setting voltage points in detail to issue detailed alarms and limiting some functions to reduce current consumption.

In FIG. 7, for example, if the normal voltage of the battery 11 is 6 EV], the detection voltages of the first and second voltage detection elements 8°9 are 5 [■] and 4. 5 It is set to [V]. Note that each of these sensing elements 8 and 9 has an error accuracy of about 3%. In this way, when a voltage fixed type element is used as each detection element 8.9, it is often used because it has advantages such as small size, low current consumption, and no adjustment.

(Problems to be Solved by the Invention) However, in conventional portable electronic devices, there is a problem in that the usable capacity after charging gradually decreases due to an inappropriate battery charging method.

That is, when a battery is used by repeatedly shallowly discharging and charging as in the past, its dischargeable capacity gradually decreases due to an effect called the memory effect.

Furthermore, in a conventional portable electronic device, when the battery voltage is detected by a detection circuit as shown in FIG. 7, the detection error becomes large based on the error accuracy of each detection element 8.9.

For example, if each sensing element 8.9 has an error accuracy of 3%, if the first sensing element has a negative error, its sensing output will be 4.85 [V], and the second sensing element will have a negative error. If the detection element has a positive error, its detection output is 4.64
[V], and the difference between both detection outputs is 0. 21 [V]
becomes. This value may be less than half the allowable error range of the normal design value, and the current consumption is twice that of one sensing element.

The present invention has been made in response to the above-mentioned problems.
It is an object of the present invention to provide a portable electronic device that prevents a decrease in usable capacity.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention provides a portable electronic device whose components are driven by a rechargeable battery.
The battery is characterized by comprising a discharge circuit that completely discharges the battery, and a discharge control circuit that operates the discharge circuit when the voltage of the battery decreases.

(Function) When the battery voltage falls below a certain value, the discharge control circuit operates the discharge circuit to completely discharge the battery.

By charging the battery after completely discharging it, you can suppress the memory effect.
It is possible to recover the decreased dischargeable capacity.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 6 shows the external appearance of a portable electronic device 1 according to an embodiment of the present invention. This portable electronic device 1 includes a rectangular parallelepiped-shaped device main body 2 of a portable size, and an LCD (liquid crystal display) 3 with a backlight is disposed at the center of the upper surface of the device main body 2. Also, at the bottom of the LCD 3, there are tinkeys, function keys, and various mode switching keys.

A keyboard 4 is arranged, which includes a correction key, a cancellation key, a surface scroll key, a space key, an input key, and the like. Further, above the LCD 3, a printer 5 for printing various character information on paper 6 is arranged.

Although not shown in FIG. 6, the main body 2 of the device is provided with a slot for installing an IC card or memory card as an external storage element, as well as a built-in buzzer and the like, as well as a battery. A rechargeable battery such as N1-CD is built-in.

Next, a battery control circuit according to a first embodiment of the present invention will be described with reference to FIG.

10 is a CPU (central processing unit) and a program memory of the portable electronic device 1 including a battery control circuit.

It controls the control operations of components such as the data memory, display device, and key-powered device, and particularly monitors the voltage of the battery 11. Taking the example of using Ni--Cd as the battery 11, this Ni--Cd battery is normally designed to drive the portable electronic device 1 with a voltage of 6 [V]. Ni-
When the voltage of the Cd battery drops below a certain value, CPU10 performs a control operation to discharge the battery 11.

A discharge circuit 12 consisting of a series circuit of a resistor R and a transistor TR is connected to the battery 11.
R operates under the control of the discharge control circuit 13 under the control of the CPU I O.

Next, the operation of this embodiment will be explained.

When the voltage of the Ni-Cd battery constituting the battery 11 drops below a certain value, CPUl0
controls the discharge control circuit 13 to turn on the transistor TR. As a result, the discharge circuit 12 is made conductive, so that the battery 11 starts discharging and a discharge current flows through the resistor R. When the battery 11 has finished completely discharging, based on the operator's instructions,
The CPU 10 controls the discharge control circuit 13 to turn off the transistor TR. As a result, the conduction of the discharge circuit 12 is cut off, so that the battery 11 stops discharging.

Subsequently, the battery 11 is charged to prepare it for reuse.

FIG. 2 is a flowchart showing the above series of operations. First, as in step A, if it is confirmed whether the voltage of the battery 11 has decreased below a certain value, then in step B the discharge of the battery 11 is started under the control of the CPU 10. Next, in step C, when the battery 11 is completely discharged, in step D, the discharge of the battery 11 is stopped under the control of CPU10. Subsequently, in step E, this battery 11 is charged.

According to this embodiment, when the voltage of the battery 11 drops below a certain value when the battery 11 is used, the battery 11 is controlled to always start discharging, and the discharge is stopped when the battery 11 is completely discharged. . As a result, when the battery voltage does not drop below a certain value, it is used as is, and when it falls below a certain value, it is completely discharged and then charged, so shallow discharge and charging are not repeated as in the past. It disappears.

By completely discharging the battery 11 once in this manner, it becomes possible to suppress the occurrence of the memory effect, so that the usable capacity after charging can be recovered and its reduction can be prevented.

FIG. 3 shows a battery control circuit according to a second embodiment of the invention.

The battery 11 is made of Ni-Cd or the like and operates as a main power source. A discharge circuit 12 consisting of a series circuit of a resistor R1 and a transistor TRI is connected to the battery 11, and the transistor TRI is controlled by a discharge control circuit 13 under the control of the CPU 10.

The battery 14 is made of a rechargeable Ni-Cd battery like the battery 11, and operates as a backup power source.

A charging circuit 15 consisting of a series circuit of a resistor R3 and a transistor TR2 is connected to the battery 14, and the transistor TR2 is controlled by a discharge control circuit 13. Further, a resistor R2 is connected in parallel to the transistor TR2, and a diode D is connected between the resistors R2 and R1.

16 is a voltage detection circuit that detects the battery 14 under the control of CPU10.
Detects the voltage of

In order to check whether the battery 14 can function as a backup power source, its voltage is detected in advance by the voltage detection circuit 16, and if the voltage has dropped to such an extent that it cannot function as a backup power source. At this time, the battery 11, which is the main power source, is activated under the control of the CPUI O.
It is configured so that charging is performed from

Next, the operation of this embodiment will be explained.

When the voltage of the battery 11 drops below a certain value, the discharge of the battery 11 is started under the control of the CPUl0 based on an instruction from the operator, or prior to this, the voltage detection circuit 16 starts discharging the battery 11 under the control of the CPUl0. Power supply battery 14
A voltage check is performed. If this battery 14 is not sufficiently charged, it will not be able to function as a backup power source, and there is a risk that the memory will be destroyed and programs and data will be lost.

Therefore, in that case, the transistor TR2 is turned on by the discharge control circuit 13 under the control of the CPUI O, thereby shorting the resistor R2 and rapidly charging the battery 14 from the battery 11 of the main power source via the diode D and the charging circuit 15. Let it charge.

When the voltage of the battery 14 has recovered sufficiently to function as a backup power source, this is checked by the voltage detection circuit 16, so that the CPU 10
controls the discharge control circuit 13 to turn off the transistor TR2 and turn on the transistor TRI. This makes the discharge circuit 12 conductive, so that the battery 11 starts discharging. When the battery 11 is completely discharged, CP
Ul0 controls the discharge control circuit 13 and the transistor TR
Since I is turned off, the discharge stops.

If the battery 14 is initially sufficiently charged, the battery 11 immediately starts discharging due to the control operation described above.

FIG. 4 is a flowchart showing the above series of operations. First, as in step A, when it is confirmed that the voltage of the main power battery 11 has decreased below a certain value, in step B, the voltage detection circuit 16 detects the voltage of the backup battery 14 under the control of the CPU10. A check is performed.

If the voltage is not normal, the flow advances to step C, where charging of the backup power battery 14 is started under the control of CPU10, and when the voltage is restored to normal, the backup power battery 14 is charged as shown in step D. Charging will be stopped.

Next, as in step E, discharging of the main power battery 11 is started under the control of the CPU IO. If the backup power supply voltage is normal in step B, the process immediately jumps to step E.

Next, when the main power battery 11 completes discharge as in step F, the discharge of the main power battery 11 is stopped in step G under the control of the CPU10.

Subsequently, in step H, the main power battery 11 is charged.

In this way, according to this embodiment, the battery 1 serving as the main power source
Even in the case where a two-system power supply consisting of a battery 14 which serves as a backup power source together with a battery 14 is provided, the same effects as in the embodiment described above can be obtained.

Furthermore, even when three or more power sources are provided, similar effects can be obtained by changing the circuit configuration.

FIG. 5 shows a third embodiment of the present invention, and shows a battery voltage detection circuit.

In this embodiment, one voltage detection element 8 made of an IC or the like is used in the configuration shown in FIG. 7, and is connected to a battery 11 made of Ni--Cd or the like via a resistor RIO. In addition, the battery 11 includes a resistor RIO, a resistor R20, and a transistor TR.
A series circuit of l0 is connected, and a resistor R30 and a transistor T are connected to a resistor R20 and a transistor TR10.
A series circuit with R20 is connected in parallel. Voltage detection element 8. Transistor TRl0. TR20 is CPU10
controlled by

Here, the input impedance of the voltage sensing element 8 is sufficiently high, and the transistor TRl0. Ignoring the collector-emitter voltage of TR20, the detection voltage V when the transistor TRl0 is turned on. The T-work is shown as the following formula. However, VD is the detection voltage of the voltage detection element 8.

Also, the detection voltage V when the transistor TR20 is turned on
. 1□ is expressed as in the following equation.

In this embodiment, the resistors RIO, R20, and R30 are generally commercially available with an error accuracy of 0. 1% to 0.
It can be constructed using a material as low as about 5%.

Next, the operation of this embodiment will be explained.

When monitoring the voltage of the battery 11, the CPU 10 controls and turns on the transistor TR10 or TR20 as necessary, thereby making it possible to obtain two types of voltage points as output. For example, transistor TR
When l0 is turned on, V as shown in equation (1) above. A1
A voltage with a value of is output. Next, when the transistor TR20 is turned on, the condition (2) shown in the above equation (2) occurs. A voltage with a value of T2 is output.

Therefore V. Two different voltage points, □ and VDT□, can be monitored.

According to such an embodiment, each resistor RIO, R20, R
As 30, one with low error accuracy can be used, so when multiple voltage points are obtained by a combination of a series circuit of resistor R20 and transistor TR10 or a series circuit of resistor R30 and transistor TR20, and voltage detection element 8. Even if an element with the same error accuracy as the conventional one is used as the voltage detection element 8, the degree of cumulative variation in the detected voltage will be reduced due to the lower error accuracy of each resistor, so the voltage point can be set to the normal design value. It can be kept within the tolerance range. Further, current consumption can also be reduced accordingly.

Furthermore, by connecting a series circuit of other resistors and transistors, it becomes possible to detect three or more types of voltage points.

In this embodiment, an example using Ni-Cd as a rechargeable battery has been described, but the present invention is not limited to this and can be applied to other batteries as well.

[Effects of the Invention] As described above, according to the present invention, when the rechargeable battery voltage falls below a certain value, the battery is completely discharged and then charged, which reduces the usable capacity of the battery. Is it possible to prevent this?

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram of a battery control circuit showing a first embodiment of the present invention, FIG. 2 is a flowchart explaining the operation of the first embodiment, and FIG. 3 is a diagram showing a second embodiment of the present invention. Wiring diagram shown,
Fig. 4 is a flowchart explaining the operation of the second embodiment, Fig. 5 is a wiring diagram showing the third embodiment of the present invention, Fig. 6 is an external view showing the device of this embodiment, and Fig. 7 is FIG. 2 is a wiring diagram showing a conventional voltage detection circuit. 1... Portable electronic device, 8... Voltage detection element, 10
...CPU (Central Processing Unit), 11...Rechargeable battery (for main power supply), 12...Discharge circuit, 13.
...Discharge control circuit, 14.. Rechargeable battery (backup power source), 15.. Charging circuit, 16.. Voltage detection circuit. ″、Representative Patent Attorney Masayoshi Misawa (2,′ Figure 1 Figure 2 Figure 4

Claims (1)

[Claims] A portable electronic device whose components are driven by a rechargeable battery, characterized by comprising a discharge circuit that completely discharges the battery, and a discharge control circuit that operates the discharge circuit when the voltage of the battery decreases. Portable electronic devices.