JP3342296B2 - Power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a power supply device for an electronic device operated by a battery.

[0002]

2. Description of the Related Art In a battery-operated electronic device, for example, a video tape recorder with a built-in camera, even when a power switch is turned off, a power supply to a main body is not immediately turned off. After detecting that it has reached the position, the control microcomputer outputs a control signal for turning off the output of the DC / DC converter, which is a power supply circuit, and turns off the power supplied to each unit. However, since the control microcomputer needs to detect the turning on of the power switch and control the power supply circuit, even in the power-off mode, power is supplied to the control microcomputer to keep it in an operation standby state. Therefore, a minute current flows even in the power-off mode.

[0003]

Therefore, in the power supply device of the conventional electronic equipment, it is necessary to supply a small amount of current even in the power-off mode. However, when power is supplied by a battery, there is a problem that the remaining capacity of the battery mounted on the electronic device body is reduced little by little even when the power switch is turned off.

[0004] It is an object of the present invention to provide a power supply device that does not reduce the capacity of a battery even when the battery is mounted while the power is turned off.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides, as a power supply, a battery connection terminal for connecting a battery, and a first connection / disconnection between the battery connection terminal and a power supply circuit. A switch, a control circuit operable by a power supply from the power supply circuit and controlling the power supply circuit in accordance with the operation of the power supply switch, and a power supply to the power supply circuit connected to a plug of an AC adapter without passing through the first switch. A charging circuit for supplying power supplied from the power supply terminal and driven by the power supply circuit to the battery connection terminal via a second switch, and controlling charging; and a first switch. And a charge switch for switching the on / off of the second switch in conjunction with the off / on of the second switch.

[0006]

[0007]

[0008] Further, there is provided a limiting means which does not permit turning on the power switch unless the charging switch is in an off state.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram showing a power supply circuit of an electronic device according to an embodiment of the present invention. In the figure, when a plug 2a of an AC adapter 2 for converting an AC power supply from a power line into a predetermined DC power supply is inserted into a DC jack 1, a power supply circuit is provided from a terminal D3 of the DC jack 1 through a diode 3 and a fuse 4. Power is supplied to the DC / DC converter 5. When the plug 2a is not inserted into the DC jack 1, the terminal D1 and the terminal D2 are connected to each other. , The terminal D1, the terminal D2, the first switch 7, and the fuse 4 to be supplied to the DC / DC converter 5.
That is, the electronic apparatus according to the present embodiment can be used with a power line or a rechargeable battery.

The DC / DC converter 5 supplies a predetermined power to the electronic device body 8 and a control circuit 9 composed of a microcomputer. The first switch 7 is configured by, for example, an FET transistor so as to be turned off when a charging switch 10 described later is turned on.

Therefore, the rechargeable battery 6 is connected to the battery connection terminals J1, J
Even when the charging switch 10 is connected, the first switch 7 is turned off when the charging switch 10 is turned on, so that it is possible to prevent a minute current from flowing out of the rechargeable battery 6. The first switch 7 is turned on / off by operating the charging switch 10.
Since it is turned off, there is no need to separately provide an operation button on the electronic device.

Further, this power supply circuit can charge the rechargeable battery 6 when the charging switch 10 is turned on while the rechargeable battery 6 is connected to the battery connection terminals J1 and J2. That is, when the charging switch 10 is turned on, the first switch 7
Is turned off, the second switch 11 is turned on, and the diode 3, the second switch 11, the third switch 12, the fourth switch 13, the resistor R1, and the resistor R
2, a charging current is passed through the diode 14 and the battery connection terminal J1, and the rechargeable battery 6 is charged.

When the connected rechargeable battery 6 is in an overdischarged state,
Alternatively, in order to prevent an overcurrent from flowing when the battery connection terminals J1 and J2 are short-circuited, a protection circuit is configured using the comparator 15, the third switch 12, the fourth switch 13, and the resistor R3. That is, the charging current from the diode 14 is also input to one of the comparators 15, and the comparator 15 outputs a control signal if the charging current is equal to or more than a predetermined value by comparing with a reference voltage input to the other, Third switch 1 which is normally on
2. The fourth switch 13 is turned off.

Therefore, the charging current from the AC adapter 2 is normally output to the battery connection terminal J1 via the resistors R1 and R2 connected in parallel, but when the third switch 12 and the fourth switch 13 are turned off. Then, the resistance R1 and the resistance R
3 are connected in series to increase the resistance value and decrease the charging current, thereby preventing overcurrent.

On the other hand, the control circuit 9 has a power switch 16 connected thereto, and the electronic device main body 8 is connected to the DC / D
While controlling the C converter 5, the third switch 12
Is also controlled. That is, it is detected that the charge switch 10 is turned on, and after a predetermined time period in which the rechargeable battery 6 is almost fully charged from the time point when the charge switch 10 is turned on, the diode 1
The control signal is output through the switch 7 to turn off the third switch 12 which is on. Then, the parallel connection of the resistor R1 and the resistor R2 is released, and the charging current passes through only the resistor R1, so that the charging current is reduced, thereby preventing the rechargeable battery 6 from being overcharged.

When the resistances of the resistors R1 and R2 are the same, the charging current is reduced to half by turning off the third switch 12. Further, the diode 18 and the diode 17 are provided with a control signal from the comparator 15 and / or
Alternatively, an OR circuit for supplying a control signal from the control circuit 9 to the third switch 12 is configured.

Next, the charging switch 10 and the power switch 1
6 will be described with reference to a functional block diagram shown in FIG. The charging switch 10 and the power switch 16 are housed in one housing 20. An operation member 21 is supported on the housing 20 so as to be slidable left and right. In the state where the operation member 21 is located at the center as illustrated, the charging switch 1
0 and the power switch 16 are both off. And when the operation member is slid to the left in the figure,
When only the charge switch 10 is turned on and slides to the right, only the power switch 16 is turned on and does not turn on at the same time.

Therefore, when the power switch 16 is turned on, the charging switch 10 is always turned off, that is, the first switch is turned on. Even when the electronic device is driven at the charging station 6, the control circuit is controlled by the DC / DC converter 5. 9
The control circuit 9 can detect that the power switch 16 has been turned on since a very small current has flowed in advance.

Although the embodiment of the present invention has been described above, it goes without saying that a DC / DC converter 5 may be operated by connecting a non-rechargeable dry battery instead of the rechargeable battery 6.

[0020]

According to the present invention, the first switch for connecting / disconnecting the battery connection terminal and the power supply circuit can prevent a small current from flowing out of the battery, and can keep the battery mounted on the electronic device body. The battery can be stored for a long time.

Since the first switch is linked with the second switch constituting the charging circuit by the charging switch, it is not necessary to provide a new operating member.

Further, since the power switch cannot be turned on unless the charge switch is in the off state, the control is performed despite the provision of the first switch for connecting and disconnecting the battery connection terminal and the power circuit. The circuit can detect that the power switch has been turned on.

[Brief description of the drawings]

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

FIG. 2 is a functional block diagram showing a main part of the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 DC jack 2 AC adapter 2a plug 5 DC / DC converter 6 Rechargeable battery J1, J2 Battery connection terminal 7 First switch 9 Control circuit 10 Charge switch 11 Second switch 16 Charge switch 21 Operating member

Claims (2)

(57) [Claims] 1. A battery connection terminal for connecting a battery, and a first connection / disconnection between the battery connection terminal and a power supply circuit.
A switch, a control circuit operable by a power supply from the power supply circuit and controlling the power supply circuit in accordance with an operation of the power supply switch, and a power supply to the power supply circuit connected to a plug of an AC adapter without passing through the first switch. A charging circuit that supplies power supplied by the power supply circuit from the power supply terminal to the battery connection terminal via a second switch and controls charging; and A power supply device comprising: a charging switch that switches between on / off of a switch and off / on of the second switch in conjunction with each other. 2. The power supply device according to claim 1, further comprising a limiting unit that does not allow the power switch to be turned on unless the charge switch is in an off state.