JPH0530681A - Power supply for electronic equipment - Google Patents

Abstract

PURPOSE:To remove influence of noise to an internal circuit by providing a switch for switching from a battery to a charging terminal or an internal circuit, and providing a switch for switching from the internal circuit to the battery or an external terminal. CONSTITUTION:A first switch 3 for switching from a battery 5 to a charging terminal 2 or an internal circuit 6, and a second switch 4 for switching from the circuit 6 to an external power source terminal 1 and the battery 5, are provided. When the external power source is not input, the switches 3, 4 are so set as to connect the battery 5 to the circuit 6. When the external power source is input, the switch 3 is so set as to connect the terminal 2 to the battery 5 and the switch 4 is so set as to connect the terminal 1 to the circuit 6. Thus, influence of noise to the circuit 6 can be removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for electronic equipment which uses a rechargeable secondary battery as a main power supply.

[0002]

2. Description of the Related Art FIG. 3 is a circuit block diagram showing a conventional example of a power supply device for electronic equipment which uses a rechargeable secondary battery as a main power supply. In FIG. 3, reference numeral 1 indicates an external power supply terminal, 2 indicates a charging terminal, 5 indicates a battery, and 6 indicates an internal circuit. A diode 14 is arranged between the battery 5 and the internal circuit 6 so that power is supplied from the battery 5 to the internal circuit 6 as indicated by a path a. Further, a diode 10 is arranged between the external power supply terminal 1 and the internal circuit 6, and power is supplied from the external power supply terminal 1 to the internal circuit 6 as shown by a path b. Furthermore, the diode 12 is arranged between the charging terminal 2 and the battery 5, and the charging terminal 2 is connected to the battery 5 as shown by the path c.
It is designed to supply power to.

In the above-mentioned structure, power is usually supplied from the battery 5 to the internal circuit 6 through the diode 14. When power is supplied to the internal circuit from an external power source, the diode 1 is set by setting the voltage of the external power source higher than the voltage of the battery 5 and the charging power source voltage of the charging terminal 2.
Since the voltage applied to both ends of 4 has the opposite polarity, the power supply from the battery 5 to the internal circuit 6 is cut off, and the power is supplied from the external power supply terminal 1 to the internal circuit 6 as shown by the path b, and the path c Electric power is supplied from the charging terminal 2 to the battery 5 as indicated by.

[0004]

However, in the conventional system, as described above, the voltage supplied from the external power source must be set to a voltage higher than the maximum value of the battery voltage or the charging voltage. Will become larger. Also, in the internal circuit, it is necessary to use a component having a high breakdown voltage corresponding to this external power supply voltage. Further, in the charging circuit, there is a drawback that a method taking into consideration the charging voltage must be used. Furthermore, in the conventional method, since the external terminal is physically and electrically connected to the internal circuit, it has a drawback that it is easily affected by noise from the outside.

Therefore, it is an object of the present invention to provide a novel power supply device for electronic equipment which solves the above-mentioned drawbacks.

[0006]

In order to achieve the above-mentioned object, the present invention provides a first switch for switching a charging terminal and an internal circuit from a battery in a power supply device for an electronic device having a secondary battery as a main power source. And an external power source terminal and a second switch for switching the battery from the internal circuit, and the first switch and the second switch are set to connect the battery and the internal circuit when the external power source is not input. , When the external power source is input, the first switch is set to connect the charging terminal and the battery, and the second switch is set to connect the external power source and the internal circuit. To do.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a circuit block diagram showing a state in which an external power source is not input. 1, a switch 1 (first switch) for switching from the battery 5 to the charging terminal 2 or the internal circuit 6 is provided as compared with the configuration of the conventional example shown in FIG. Alternatively, a switch 2 (second switch) for switching to the external power supply terminal 1 is provided, and instead of the diode 1,
0 and 14 have been removed. In the state of FIG. 1, power is supplied from the battery 5 to the internal circuit 6 as indicated by the path a, and the external power supply terminal 1 and the charging terminal 2 are separated from the internal circuit 6 at this time.

FIG. 2 is a circuit block diagram showing a state when an external power source is input. In FIG. 2, switch 1
1 and 2 are switched from the state of FIG. 1, power is supplied to the internal circuit 6 from an external power source as shown by a path c, and charging is performed from the charging terminal 2 to the battery 5 as shown by a path b. Be seen. At this time, the battery 5 is separated from the internal circuit 6. Note that the switching of the two switches is performed from this external power supply during operation of the external power supply, for example.

[0009]

As described in detail above, the present invention is
By providing two switches instead of the diode and switching the two switches by an external power source, the battery can be completely separated from the internal power source, that is, physically.
As a result, the voltage of the external power supply can be set to the minimum voltage to be supplied to the internal circuit, so that the size can be reduced and at the time of charging, any charging method can be selected without being restricted by voltage or the like. Further, when the external power supply is not connected, the external power supply terminal and the charging terminal are physically separated from the internal circuit, and thus are not affected by noise.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a state in which an external power supply is not input.

FIG. 2 is a circuit block diagram showing a state when an external power supply is input.

FIG. 3 is a circuit block diagram showing a conventional example of a power supply device for electronic equipment having a rechargeable secondary battery as a main power supply.

[Explanation of symbols]

 1 External power supply terminal 2 Charging terminal 3 First switch 4 Second switch 5 Battery 6 Internal circuit

Claims (1)

Claim: What is claimed is: 1. In a power supply device for an electronic device, which uses a secondary battery as a main power supply, a first switch for switching a charging terminal and an internal circuit from the battery, and an external power supply terminal and the battery from the internal circuit. A second switch for switching, and the first switch and the second switch are set to connect the battery and the internal circuit when the external power source is not input, and the first switch and the second switch are set when the external power source is input. Is connected to the charging terminal and the battery, and the second switch is set to connect the external power supply and the internal circuit.