JPH0795732A - Device for selecting power supply to be used - Google Patents

Abstract

PURPOSE:To extend the continuously using time of electronic equipment by electrically detecting the connection of an external battery and, when the external battery is connected, successively using an internal battery and the external battery. CONSTITUTION:When it is discriminated that the power supply voltage of an internal battery 1 becomes lower than a dropped voltage in a state where it is discriminating that an external battery 3 is connected by judging that the external battery 3 is connected by means of an external connection judging means 15 and detecting that the power supply voltage of the battery 1 has become lower than the lowest limit at which the normal operation of a load 6 is guaranteed by means of a voltage drop detecting means 14, the power supply voltage from the battery 3 is supplied to the load 6 by operating a switch 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power source selection device for selectively switching power sources of two systems of an internal battery and an external battery.

[0002]

2. Description of the Related Art In a portable portable electronic device, an internal battery housed in a housing of the main body and an external battery housed in a battery box detachable from the main body in a housing separate from the main body are used. There is a system that can selectively use the power supply of the system.

In such an electronic device, a power source selection device for selecting a power source to be used is, for example,
As shown in Japanese Patent No. 23066, it is known that an internal battery is disconnected from a load by connecting an external power source, and switching is automatically performed so that the external power source is used.

The above-mentioned power source selection device automatically switches the external power source to be usable by simply connecting the external power source when the internal battery is exhausted or when the internal battery is preserved. , No complicated operation is required to select the power supply to be used.

[0005]

On the contrary, the above-mentioned power source selection device cannot use the internal battery in the state where the external power source is connected. Therefore, when the external power source is a battery, the internal battery cannot be used. It was impossible to extend the continuous use time of the electronic device because the external battery had to be connected and the internal battery and the external battery could not be used one after another.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and includes a switch inserted in an external power supply path for supplying a load with a power supply voltage from an external battery,
Reduced voltage detection means for detecting that the power supply voltage of the internal battery has fallen below the minimum level that guarantees normal operation of the load, and external connection determination means for determining that an external battery has been connected , It is detected that the power supply voltage of the internal battery has dropped below the reduced voltage by the reduced voltage detection means,
And a switch switching control means for controlling switching of the switch so as to supply a power supply voltage from the external battery to the load when the external connection determining means determines that the external battery is connected.

[0007]

According to the present invention, when it is determined that the external battery is connected, when the power supply voltage of the internal battery drops below the reduced voltage, the switch is switched to supply the power supply voltage from the external battery to the load. Thus, when the electronic device is used while the external battery is connected, the internal battery is used first, and when the internal battery is exhausted, the external battery is automatically used.

Further, all the means for detecting the power source selection condition are electrically performed.

[0009]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. In the figure, reference numeral 1 denotes an internal battery housed in the housing of the main body 2, which is composed of a nickel cadmium secondary battery and is rechargeable.

Reference numeral 3 denotes an external battery which is housed in a battery box 4 which is detachable from the main body 2 and which is separate from the main body 2. The external battery 3 is composed of a primary battery such as an alkaline battery, The main body 2 is selectively connected to the external power supply terminals 5a and 5b.

Reference numeral 6 is a load which is an internal circuit constituting the main body 2, 7 is a main power switch which is inserted into a power supply path for supplying a power supply voltage from the internal battery 1 and the external battery 3 to the load 6, and 8 is a main power switch. The power supply voltages from the internal battery 1 and the external battery 3 are applied to the power supply terminal 8a via the backflow prevention diodes 9 and 10, respectively, and the power key switch 1
A microcomputer provided with a power supply control means 12 for controlling the opening and closing of the main power supply switch 7 in accordance with the operation of 1, and 13 is inserted into a power supply path for the external battery 3 connecting the external power supply terminal 5a and the main power supply switch 7. It is an auxiliary power switch.

The microcomputer 8 has a voltage reduction detecting means 14 for detecting that the power supply voltage of the internal battery 1 has decreased to a minimum voltage level for ensuring the normal operation of the load 6, and the external power supply terminal 5a. Voltage generated on the load 6
External connection determination means 15 for detecting that the external battery 3 has been connected, and detecting that the external battery 3 has been connected to the external battery 3 by the detection.
An AND means 16 which ANDs the discrimination output from the external connection discrimination means 15 and the detection output from the reduced voltage detection means 14, and the switching of the auxiliary power switch 13 is controlled according to the AND output from the AND means 16. The switch switching control means 17 is provided.

The reduced voltage detecting means 14 is adapted to operate only when the switch switching control means 17 controls the auxiliary power switch 13 to be in an open state.

Next, the circuit operation of FIG. 1 will be described.
In the microcomputer 8, the power supply voltage of the internal battery 1 is applied to the power supply terminal 8a via the diode 9 or the power supply voltage of the external battery 3 is applied to the power supply terminal 8a via the diode 10, and the power supply voltage is always applied regardless of the power-on. Has been done.
In the state where the power is not turned on, the microcomputer 8 is set to the sleep mode and most of its operations are stopped, but the power control means 12 monitors the opening and closing of the power key switch 11. .

Now, the power key switch 11 is closed,
When the power supply control means 12 detects that the power key switch 11 is closed, the microcomputer 8 is released from the sleep mode, and the power supply control means 12 closes the main power supply switch 7.

When the main power switch 7 is closed, the internal battery 1 and the load 6 are connected, and the power supply voltage of the internal battery 1 is supplied to the load 6. By the way, the power supply voltage of the internal battery 1 is applied to the terminal 8b of the microcomputer 8, and the voltage level is monitored by the reduced voltage detection circuit 14. The reduced voltage detection circuit 14 outputs a reference voltage set in accordance with a reduced voltage that is less than a minimum value for ensuring that the power source voltage of the internal battery 1 operates the load 6 normally and the power source voltage of the internal battery 1. In comparison, when the power supply voltage is lower than the reference voltage, that is, when the power supply voltage of the internal battery 1 is lower than the reduced voltage, an “H” level detection output is generated. The detection output of the "L" level is generated. Therefore, when the power supply voltage of the internal battery 1 is higher than the reduced voltage, the "L" level output from the AND means 16 is applied to the switch switching control means 17.

Here, the switch switching control means 17
Controls the auxiliary power switch 13 to the open state when the "L" level AND output is input, and "H"
When the level AND output is input, the auxiliary power switch 13 is controlled to be closed. Therefore, the internal battery 1
Is higher than the reduced voltage, the auxiliary power switch 13 is in the open state, and the power supply path connecting the external battery 3 and the load 6 is cut off even when the main power switch 7 is closed. There is.

Therefore, when the power source voltage of the internal battery 1 is higher than the reduced voltage, the internal battery 1 is used as the power source of the load 6. On the other hand, in the state where the power supply voltage of the internal battery 1 is reduced to the reduced voltage or less, the reduced voltage detection means 14 generates the detection output of “H” level, and the AND means 16
Is in a state in which the AND output changes in accordance with the discrimination output level from the external connection discrimination means 15.

Here, the external connection discriminating means 15 detects whether or not the voltage generated at the external power supply terminal 5a is equal to or lower than the reference voltage set according to the reduced voltage, and the voltage equal to or lower than the reference voltage is detected. When it is detected, it is determined that the external battery 3 is not connected, and an “L” level determination output is generated. On the other hand, when a voltage higher than the reference voltage is detected, the external battery 3 is connected. It is determined that it is in the state of being.
Therefore, the battery box 4 accommodating the external battery 3 is mounted on the main body 2 and the voltage generated at the external power supply terminal 5a is higher than the reference voltage in a state where the power supply voltage of the internal battery 1 is decreased to the reduced voltage or less. In this case, the AND output from the AND means 16 becomes "H" level, and the switch switching control means 1
The auxiliary power switch 13 is closed by 7.

Therefore, when it is determined that the external battery 3 is connected in the state where the power supply voltage of the internal battery 1 is reduced to the reduced voltage or less, the external battery 3 is used as the power source of the load 6.

In this case, the power supply voltage of the external battery 3 is applied to the load 6 after the internal battery 1 is once charged. Further, when the auxiliary power switch 13 is switched to the closed state by the switch switching control means 17, the detection operation by the reduced voltage detection means 14 is stopped, so that the power supply voltage of the external battery 3 is the terminal 8 of the microcomputer 8.
The closed state of the auxiliary power switch 13 is maintained even when applied to b.

By the way, when the external battery 3 is connected in a state where the internal battery 1 is not consumed below the reduced voltage, it is first detected by the reduced voltage detection means 14 that the power supply voltage of the internal battery 1 is higher than the reduced voltage. Upon detection, the auxiliary power switch 13 is opened, and the internal battery 1 is used as a power source for the load 6. After that, when the internal battery 1 is consumed by the load 6 and the power supply voltage of the internal battery 1 drops below the reduced voltage, the power supply voltage of the internal battery 1 falls below the reduced voltage in the state where it is determined that the external battery 3 is connected. Since it will be detected that
3 is closed. Therefore, by connecting the external battery 3 while the internal battery 1 is being charged, the internal battery 1 and the external battery are sequentially used as the power source of the load 6.

[0023]

As described above, the power source selection device according to the present invention automatically switches the battery to be used according to the exhaustion state of the internal battery and the connection state of the external battery, so that the external battery is connected. Can prevent the internal battery from being used up, and by connecting the external battery, the internal battery and the external battery can be used sequentially, and the continuous use time of electronic devices can be extended. I can.

Further, according to the present invention, since the connection status of the external battery is electrically detected, a microcomputer can be used for the detection, and the configuration can be simplified.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1 Internal Battery 3 External Battery 6 Load 7 Main Power Switch 8 Microcomputer 13 Auxiliary Power Switch 14 Reduced Voltage Detection Means 15 External Connection Discrimination Means 16 AND Means 17 Switch Switching Control Means

Claims (2)

[Claims] 1. An electronic device in which an external battery is connectable in parallel to an internal battery, and a power supply voltage from the external battery is supplied to a load in an electronic device that switches and uses two systems of power sources, the internal battery and the external battery. A switch that is inserted into the external power supply path, a voltage reduction detection unit that detects when the power supply voltage of the internal battery is below the minimum voltage that guarantees normal operation of the load, and the external battery An external connection determining means for determining that the switch is connected, and a switch switching control means for controlling switching of the switch according to a detection output from the reduced voltage detecting means and a determination output from the external connection determining means, The feature is that the power supply voltage from the external battery is supplied to the load when the power supply voltage of the internal battery drops below the reduced voltage when it is determined that the external battery is connected. Used power source selection device. 2. The external connection determination means according to claim 1, wherein the external battery connection determination is performed by detecting that the voltage generated at the connection terminal of the external battery is higher than the reduced voltage of the load. Used power source selection device.