JPH11224132A - Power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a short-circuit current from a secondary battery to the outside from being generated owing to the short-circuiting of the power reception terminal of an electric equipment when an AC adapter is detached from the electric equipment main body and the electronic equipment is placed in operation by a secondary battery provided inside the electronic equipment main body. SOLUTION: In the AC adapter 1, a rectifying circuit consisting of a diode D3 and a capacitor C4 is added to the side of the secondary winding 142 of a converter transformer 14 to constitute a circuit which outputs a control signal rectified by the rectifying circuit from a control terminal 7a and also allows the electronic equipment main body 2 to disconnect the secondary battery 2 and power receiving input terminal 5b from each other with the control signal inputted from a control terminal 7b. When the control signal is zero, the secondary battery 2 and power receiving input terminal 5b are insulated from each other, so that no short-circuit current flows even if the power receiving input terminal 5b and 6b short-circuit.

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, and more particularly, to a power supply device for preventing backflow of a secondary battery provided in an electronic device.

[0002]

2. Description of the Related Art A rechargeable battery (secondary battery) is provided in an electronic device as a power supply to a small and portable electronic device, and a predetermined DC voltage is converted from a household power supply of AC100V. Equipment to supply electronic equipment,
A so-called method using an AC adapter together has been generally used.

Next, a conventional power supply device using both a secondary battery and an AC adapter will be described with reference to FIGS. FIG. 4 is a block diagram showing a configuration of a conventional power supply device, FIG. 5 is a diagram showing a state where an AC adapter is not used in this power supply device, and FIG. 6 shows a relationship between a voltage of the power supply device and a load current. FIG. Here, the power supply means a system configuration of an AC adapter and a power supply circuit inside the electronic device.

[0004] As shown in FIG. 4, when the AC adapter 3 is mounted on the electronic device main body 4, the power supply terminal 5 a of the AC adapter 3 which is a positive terminal and the power receiving terminal 5 b of the electronic device main body 4 are connected. A power supply terminal 6a of the AC adapter 3 which is a terminal and a power receiving terminal 6b of the electronic device body 4
Is connected, and power is supplied to the electronic device main body 4.

[0005] First, an AC plug 11 is inserted into an AC 100 V outlet, which is a home power supply, and power is supplied to the AC adapter 3.
After removing the noise on the power supply in step 2, the rectifier circuit 1
In step 3, the voltage is converted to a DC voltage. The converted DC voltage is input to the primary winding 141 side of the converter transformer 14, and predetermined power is transmitted to the secondary winding 142 side by a switching operation of a transistor Tr described later in detail. On the secondary side, the direct current is converted again by the diode D3 and the capacitor C3 and sent to the power supply terminal 5a.

In order to control the output voltage and current, the DC-converted voltage is input to a differential amplifier 15 and compared with a reference voltage V1. The comparison signal is sent to a control signal transmission circuit 17 via a diode D1. Is input to Similarly, the supplied current is the resistance R1 inserted in the negative power line.
Is input to the differential amplifier 16 and the operation result is input to the control signal transmission circuit 17 via the diode D2. The control signal transmission circuit 17
Is composed of, for example, a photocoupler or the like that can electrically separate the primary side and the secondary side. Based on the detected voltage and current, a control signal for converting predetermined power is input from the control signal transmission circuit 17 to the control circuit 18, and the transistor Tr is set to PWM (Pulse Width Modul).
The power is controlled and driven to supply a predetermined power from the primary side to the secondary side.

As shown in FIG. 6, for example, as shown in FIG. 6, a constant voltage V01 is output until the output current I0 reaches a maximum of I01 (constant voltage control). The current I0 is kept at the maximum value I01, and the output current I0 is controlled to be constant, and as a result, the voltage V0 is controlled to decrease (constant current control).

In the electronic equipment main body 4, the current I0 input from the power receiving terminal 5b is supplied to the electronic equipment circuit 21 (current IS), and the transistor Q1 is operated by an external operation of the electronic equipment main body 4 if necessary. Activate,
Accordingly, the secondary battery 22 is charged by operating the FET switch F1 (current IC).

Next, consider the case where the electronic device main body 4 is driven by the built-in secondary battery 22 in the power supply device having the above-described configuration, and the AC adapter 3 is not mounted on the electronic device main body 4. At this time, as shown in FIG. 5, the power supply terminal 5a and the power receiving terminal 5b, and the power supply terminal 6a and the power receiving terminal 6b are separated and exposed to the outside. In this state, the transistor Q1 is operated, so that the FET switch F1 is operated to supply the current IS to the electronic device circuit 21 to operate the electronic device.

However, in the above-described use state, the power receiving terminal 5b and the power receiving terminal 6b are exposed to the outside. Therefore, when these two terminals are short-circuited, a very large short-circuit current Ig flows out of the secondary battery 22. There was a problem. Therefore, measures such as adopting a structure in which the power receiving terminals 5b and 6b are unlikely to be short-circuited and providing a terminal cover have conventionally been taken. However, problems such as complicated structure and high cost remain. I was

[0011]

SUMMARY OF THE INVENTION Accordingly, the present invention relates to a case where an electronic device is operated by a power supply side device, that is, an AC adapter is detached from an electronic device main body and a secondary battery provided inside the electronic device main body. In this case, it is intended to prevent a current from flowing out of a built-in secondary battery to the outside due to a short circuit of a power receiving terminal of an electronic device.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and comprises a power supply unit mounted on an electronic device for supplying power and a power supply circuit provided in the electronic device. A power supply unit configured to include a supply power generation circuit, a power supply terminal, a control signal generation circuit, and a control signal output terminal; The power supply circuit provided includes a power receiving terminal, a control signal input terminal, and a shutoff means for shutting off the secondary battery provided inside the electronic device and the power receiving terminal, wherein the control signal input is provided. A power supply device is configured to shut off a secondary battery and a power receiving terminal inside the electronic device by the shutoff means based on a control signal from the power supply unit input from a terminal.

[0013] Further, the control signal generation circuit has a circuit configuration for generating a voltage higher than a voltage generated by the supply power generation circuit, thereby solving the above-mentioned problems.

According to the configuration of the present invention, when the AC adapter is detached from the electronic device main body, the secondary battery built in the electronic device and the power receiving terminal of the electronic device are automatically shut off.

A sufficiently high control signal is supplied to a circuit on the electronic device side.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS. Here, FIG.
FIG. 2 is a block diagram illustrating a configuration of a power supply device according to the present invention. FIG. 2 is a diagram illustrating a state where an AC adapter is not used in the power supply device. FIG. 3 is a diagram illustrating a configuration example of a converter transformer of the power supply device. It is.

In the embodiment, as shown in FIG. 1, in the AC adapter 1, a rectifier circuit composed of a diode D4 and a capacitor C4 is added to the secondary winding 142 of the converter transformer 14 so that the control terminal 7a The control signal generated by the rectifier circuit is output and the electronic device main body 2
Is characterized by having a circuit configuration for shutting off the secondary battery 22 and the power receiving terminal 5b based on a control signal input from the control terminal 7b.

The main body 2 of the electronic equipment includes an FET switch F2 inserted into the + power supply line and a transistor Q2 inserted between the gate of the FET switch F2 and the-power supply line, which are operated by a control signal input from the control terminal 7b. Is provided. Further, the input control signal is input to the electronic device circuit 21. Note that the other circuit configurations and operations of the AC adapter 1 and the electronic device main body 2 are the same as those described for the AC adapter 3 and the electronic device main body 4 in the conventional example, and a description thereof will be omitted.

The operation of the power supply device in the above-described circuit configuration will be described. The current input from the power receiving terminal 5b is input to the electronic device circuit 21 via the FET switch F2 (current IS), and the charging current (current IC) is supplied to the secondary battery 22 via the FET switch F1. .
The transistor Q2 inserted between the gate of the FET switch F2 and the power supply line operates at the voltage VP input from the control terminal 7b, and the FET switch F2 becomes conductive.
Electric power is supplied to the electronic device circuit 21. Also, the operation of the electronic device main body 2 causes the transistor Q1
And the FET switch F1 is operated to charge the secondary battery 22.

Next, let us consider a case where the electronic device main body 2 is driven by the built-in secondary battery 22 in the power supply device having the above-described configuration, and the AC adapter 1 is not attached to the electronic device main body 2. At this time, as shown in FIG. 2, the power supply terminal 5a and the power reception terminal 5b, the power supply terminal 6a and the power reception terminal 6b, and the control terminals 7a and 7b are separated and exposed to the outside. In this state, the transistor Q1 is actuated by an external operation or the like to the electronic device circuit 21, so that the FET switch F1
Is activated, electric power is supplied to the electronic device circuit 21, and the current IS flows into the electronic device circuit 21 to operate the electronic device.

In this case, since the voltage VP at the control terminal 7b is zero, the transistor Q2 does not operate, and the FET switch F2 does not operate, the + power supply line is connected between the power receiving terminal 5b and the secondary battery 22. Will be cut off. Therefore, even if a short circuit occurs between the power receiving terminals 5b and 6b, no short-circuit current flows from the secondary battery 22 between the terminals.

Therefore, there is no generation of a large current from the secondary battery 22 to the outside, which is safe, and there is no need to complicate the terminal shape as in the prior art. Further, by inputting the voltage VP of the control terminal 7b to the electronic device circuit 21, the operation state of the AC adapter 1 can be monitored.

FIG. 3 is a diagram showing another example of the secondary winding 142 for generating a control voltage for the converter transformer 14. As shown in FIG. This is obtained by extracting the voltage VP from a portion having a larger number of turns than the winding that generates the output voltage V0.
The voltage VP is higher than the output voltage V0. By using such a winding, a high voltage VP for control can be obtained even for an electronic device having a low operating voltage, and the power supply circuit and the electronic device circuit inside the electronic device can be reliably controlled. It becomes possible.

In the embodiment described above, the constant voltage and constant current control described with reference to FIG. 6 in the conventional example is similarly applied.

The present invention is not limited to the above-described circuit configuration, but may employ any circuit configuration that realizes the technical idea of the present invention.

[0026]

As is apparent from the above description, according to the power supply device of the present invention, when the power supply side device, that is, the AC adapter is removed from the electronic device main body,
Short-circuiting of the power receiving terminal on the electronic device side can prevent generation of a short-circuit current from the built-in secondary battery.

Also, by monitoring the voltage of the control terminal, the presence or absence of the AC adapter and the operation state can be identified on the electronic device side, and various operation states regarding the power supply can be displayed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a power supply device according to the present invention.

FIG. 2 is a diagram illustrating a state where an AC adapter is not used in the power supply device illustrated in FIG. 1;

FIG. 3 is a diagram illustrating a configuration example of a converter transformer of the power supply device illustrated in FIG. 1;

FIG. 4 is a block diagram showing a configuration of a conventional power supply device.

FIG. 5 is a diagram illustrating a state in which an AC adapter is not used in the power supply device illustrated in FIG. 4;

FIG. 6 is a diagram illustrating a relationship between a voltage of a power supply device and a load current.

[Explanation of symbols]

1,3 ... AC adapter, 2,4 ... Electronic device body, 5
a, 6a: power supply terminal, 5b, 6b: power receiving terminal,
7a, 7b control terminal, 11 AC plug, 12 input filter, 13 rectifier circuit, 14 converter transformer, 15, 16 differential amplifier, 17 control signal transmission circuit, 18 control circuit, 21 electronic Equipment circuit, 22: secondary battery, 141: primary winding, 142: secondary winding

Claims (2)

[Claims] 1. A power supply device comprising a power supply unit mounted on an electronic device and supplying power, and a power supply circuit provided in the electronic device, wherein the power supply unit is configured to generate a supply power. A power supply circuit, a power supply terminal, a control signal generation circuit, and a control signal output terminal. The power supply circuit provided in the electronic device includes a power reception terminal, a control signal input terminal. And a shutoff means for shutting off the secondary battery and the power receiving terminal provided inside the electronic device, and based on a control signal from the power supply unit input from the control signal input terminal, A power supply device characterized in that a secondary battery and a power receiving terminal inside a device are shut off by the shut-off means. 2. The power supply device according to claim 1, wherein the control signal generation circuit has a circuit configuration that generates a voltage higher than a voltage generated by the supply power generation circuit.