JPH07322527A - Power supply adapter for electronic apparatus - Google Patents

Abstract

PURPOSE:To drive an electronic apparatus using both power supplies while eliminating the ON/OFF control for switching by providing means for limiting the bidirectional current flowing from an internal power supply to an external power supply, or vice versa, to a predetermined level. CONSTITUTION:An external battery adapter 1 comprises output terminals 2A, 2B, an external power supply, i.e., a battery 3, and a current limiter 4. The current limiter 4 is interposed between the output terminals 2A, 2B and the battery 3 and allows a current to flow in the direction from the battery 3 to the output terminal 2A or vice versa while limiting the current to a predetermined level or below in each direction. Consequently, the control system can be simplified to reduce the cost while allowing to drive an electronic apparatus using both the internal and external power supplies. Furthermore, the driving time can be prolonged and the operation can be sustained even if one power supply is replaced during operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an external power supply adapter applied to an electronic device capable of using an internal power supply and an external power supply in parallel, and particularly to the external power supply adapter for simultaneous use. The present invention relates to control of voltage and current supplied from an external power supply according to the state.

[0002]

2. Description of the Related Art Heretofore, in various electronic devices, there are many power supply systems which are configured to use both an internal power supply provided inside a set and an external power supply mounted outside the set.

The conventional combined internal / external power supply system is shown in FIG.
, The internal circuit 26 of the set 25, the internal power supply circuit 27, the switch circuit 28, the control circuit 29, and the external power supply input terminal 30A provided on the outer surface of the set 25,
30B and the information input terminal 31, and the external power supply circuit 32.

The internal power supply circuit 27 has an internal power supply (battery) and a circuit for detecting the state of the internal power supply. One end (the positive terminal in FIG. 10) of the internal power source is connected to one power source input terminal A of the internal circuit 26. The other end (minus terminal in FIG. 10) of the internal power source is connected to the switch circuit 28.

Further, the detection circuit of the internal power supply circuit 27 is connected to the control circuit 29, and whether the internal power supply is present or not,
The control circuit 29 is notified of information about the state of the internal power supply such as the remaining amount.

The switch circuit 28 has a switch and an operation circuit for turning on / off the switch. One terminal of this switch is connected to the negative terminal of the internal power supply circuit 27, and the other terminal is connected to the internal circuit 26.
Is connected to the other power input terminal B.

The operation circuit of the switch circuit 28 is adapted to turn on / off the switch in response to a control signal supplied from the control circuit 29. As a result, when the switch is turned on by the control signal from the control circuit 29, a power supply path from the internal power supply circuit 27 to the internal circuit 26 is formed.

External power input terminals 30A, 3 of the set 25
0B are power input terminals A and B of the internal circuit 26, respectively.
Connected with. The information input terminal 31 is connected to the control circuit 29.

The external power supply circuit 32 has a battery as an external power supply, a circuit for detecting the state of the battery, and the like. The positive terminal of the battery is the external power input terminal 30
The negative terminal is connected to the external power input terminal 30B. By this connection, power can be supplied from the external power supply circuit 32 to the internal circuit 26 of the set 25 via the external power supply input terminals 30A and 30B.

The circuit for detecting the state of the battery of the external power supply circuit 32 is connected to the information input terminal 31, whereby the information on the state of the external power supply is sent to the control circuit 29 via the information input terminal 31. It is supposed to report.

The entire operation of the power supply circuit having the above structure is controlled by the control circuit 29 as follows.

(1) Single Use of External Power Supply When the internal power supply cannot be used due to the information from the internal power supply circuit 27 for some reason, the control circuit 29 turns off the switch to disconnect the internal power supply, and the internal circuit 26 It is controlled so that it is driven only by an external power supply.

(2) Single use of internal power source The control circuit 29 cannot use the external power source when the external power source circuit 32 is not connected to the external power source input terminal, or even when it is connected, depending on the information from the external power source circuit 32. If it is determined that the internal circuit 2
Drive 6

(3) Alternate use of internal power supply and external power supply The control circuit 29 judges which is the best to use based on the information from the internal power supply circuit 27 and the external power supply circuit 32, and as a result, Use either power supply. This method has an advantage that the continuous use time of the set 25 is long, but has a drawback that the control circuit 29 has to perform complicated control, which increases the cost.

(4) Simultaneous use of internal power supply and external power supply Simultaneous use of internal power supply and external power supply increases the power supply capacity, so the continuous use time of the set is long, but charging and discharging current flows between both power supplies, which is dangerous. In some cases, this usage is prohibited.

[0016]

However, the above-mentioned prior art 0 (1), (2),
Even if all of the usage methods of (3) and (4) are possible, a large charge / discharge rush current may flow between the internal and external power sources, which requires complicated control and is costly. There was a problem that it became expensive.

Therefore, it is necessary to solve the problem of realizing an internal power supply / external power supply dual-use system which is low in cost, does not require complicated control, and can safely use the internal power supply and the external power supply simultaneously. Has issues that must be addressed.

[0018]

In order to solve the above problems, a power supply adapter for an electronic device according to the present invention is an electronic device having an internal power supply and an input terminal for connecting an external power supply. An output terminal removably connected to the input terminal is provided on the power supply side, and the output terminal is provided with a current limiter means for limiting a current flowing in both directions of the external power supply and the internal power supply to a predetermined value. It was established.

The current limiter means cuts off the power supply from the external power supply when the power supply from the external power supply to the internal power supply exceeds a predetermined current value; the predetermined current. The detection above the value should be done by the switching element;
Including an OS-type FET; the current limiter means includes:
A safety compensating means for detecting a voltage difference between the internal power source and the external power source is provided; the safety compensating means is configured to detect the voltage difference from the external power source when the voltage is outside a predetermined voltage value range based on the overdischarge voltage value of the internal power source. The power supply adapter for an electronic device is configured to cut off the supply of voltage.

[0020]

The function of the power adapter of the electronic device having the above-mentioned structure is
It has the following effects.

(1) Since the current limiter means for limiting the bidirectional current flowing from the internal power source to the external power source or from the external power source to the internal power source to a predetermined value is provided, the on / off control of the switch for switching is unnecessary. In addition, the driving is not limited to one of the power supplies, and the driving using both of them is possible, and the time when the device can be driven can be extended.

Further, even if one of them is replaced during use, continuous operation can be maintained.

(2) The current limiter means cuts off the power supply from the external power supply when the power supply from the external power supply to the internal power supply side exceeds a predetermined current value. Even if there is a voltage difference between the two, it is possible to prevent the adverse effect on the power supply of the other party by causing the reverse flow.

(3) Since the predetermined current value is detected by the switching element, the structure of the current limiter means can be realized easily and at low cost.

(4) The switching element is a MOS type F
With the configuration including ET, it becomes possible to realize the current limiter means in which the self-discharge amount is suppressed.

(5) Since the current limiter means is provided with the safety compensating means for detecting the voltage difference between the internal power source and the external power source, for example, heat is generated due to a predetermined voltage difference between the internal power source and the external power source. It is possible to prevent the harmful effects caused by.

(6) The safety compensating means is normally carried out by interrupting the supply of the voltage from the external power source when it is outside the predetermined voltage value range based on at least the over-discharge voltage value of the internal power source. It is possible to prevent a harmful effect due to a voltage difference due to parallel connection accompanying the control of over-discharge and over-charge, such as an adverse effect due to heat generation.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the power adapter for electronic equipment according to the present invention will be described below. As shown in FIG. 1, an external battery adapter 1 which is a power supply adapter for an electronic device basically has output terminals 2A and 2B, a battery 3 as an external power supply, and a current limiter 4. ing.

The output terminals 2A and 2B are provided with a plus sign (+) on the output terminal 2A so that the external battery adapter 1 can be detachably connected to an electronic device, and the output terminal 2B is provided.
Is marked with a minus sign (-), and depending on the device, it has a structure considering the directionality, so that the user does not make a mistake when mounting.

The current limiter 4 is provided between the output terminals 2A, 2B and the battery 3, and as shown by the symbol in FIG. 1, the direction from the battery 3 to the output terminal 2A (direction A) and vice versa. It has a function of allowing a current in both directions (direction B) and limiting the current in each direction to a predetermined value or less.

As shown in FIG. 2, the external battery adapter 1 having the above-mentioned structure is a set 5 of electronic equipment.
Attached to. The set 5 includes the internal circuit 6 and
It has an internal power supply 7, input terminals 8A and 8B, and a switch SW.

The internal circuit 6 represents all circuits supplied with power.

The internal power source 7 is mainly composed of a battery, and its positive terminal is connected to one power source input terminal 6A of the internal circuit 6.

The negative terminal of the internal power source 7 is connected to the other power source input terminal 6B of the internal circuit 6 via the switch SW.
Connected with. That is, when the switch SW is on, the internal power supply 7 supplies power to the internal circuit 6.

The input terminal 8A is connected to the power supply input terminal 6A of the internal circuit 6, and the input terminal 8B is connected to the power supply input terminal 6B of the internal circuit 6.

In order to attach the external battery adapter 1 to the set 5 provided in the electronic device having such a structure, the input terminals 8A and 8B of the set 5 and the output terminals 2A and 2B of the external battery adapter 1 are connected. Connect each. This connection can be easily made by inserting one into the other.

When the external battery adapter 1 is attached to the set 5, the battery 3 is connected to the internal circuit 6 via the current limiter 4, the output terminals 2A and 2B and the input terminals 8A and 8B. That is, the batteries 7 and 3 have the internal circuit 6
The power can be supplied in parallel with the power supply.

A set 5 of electronic devices configured as described above
The entire operation of the external battery adapter 1 connected to can be independently operated or used simultaneously as described below. The following is a description of each item.

(1) Single operation by internal power supply or external power supply Even when one battery is replaced, the other battery can operate the set 5 without any trouble during that time.

(2) Simultaneous use of internal power source and external power source The greatest feature of the present invention is that the simultaneous use of the internal power source and the external power source increases the total power source capacity, thus increasing the continuous use time of the set 5. Is. In this case, a charging / discharging current due to a voltage difference may flow between the batteries 3 and 7, but there is no danger because the bidirectional current limiter 4 limits the current so that it does not become excessive. .

External battery adapter 1 according to the present invention
Various examples were applied to an electronic device, for example, a camcorder, and a comparative study was conducted. The basic conditions of the current limiter 4 in this case are that the current limiting operation is performed at a steady current value (2 amperes in the embodiment), and the instantaneous current is allowed to exceed a predetermined current value (2 amperes in the embodiment). Don't backflow.

In addition to the above conditions, the problem of heat generation of the bidirectional current limiter based on the voltage difference between the internal power supply and the external power supply was also examined, and an effective countermeasure could be obtained.

The first to fourth embodiments described below relate to a bidirectional current limiter satisfying only the above basic conditions ~, and the fifth and sixth embodiments have basic conditions ~.
The present invention relates to a bidirectional current limiter that satisfies both the heat generation countermeasure and the heat generation countermeasure.

Bidirectional current limiter 4 according to the first embodiment
As shown in FIG. 3, A is a transistor 9, 10, a DC impedance R _LIM (0.3 ohm in the embodiment), a resistor R ₁ (4.7 ohm in the embodiment), R ₂ ( In the embodiment, 47 ohms) and a capacitor C are used.

The collector of the transistor 9 is connected to the output terminal 2A.
Connected to the emitter connected to one end of the DC impedance R _LIM, the other end of the DC impedance R _LIM connected to the positive terminal of the external power source of the battery 3, connecting the negative terminal of the battery 3 of the external power supply and the output terminal 2B To do. As a result, when the transistor 9 is on, the DC impedance R
A flow path for the current I is formed through the _LIM .

Further, resistors R ₁ and R ₂ are connected in series,
The terminal on the side of the resistor R ₁ of this series resistor is connected to the transistor 9
Of the resistor R ₂ and the output terminal 2B. The base of the transistor 10 is connected to the emitter of the transistor 9, and the collector is a resistor R.
₁ and R ₂ are connected, and the emitter is connected to the positive terminal of the battery 3 of the external power supply. In addition, the output terminal 2A,
Connect capacitor C between 2B.

The current limiter 4A configured as described above
Works as follows: That is, the transistor 9 is
A voltage between the base and the emitter (referred to as V _BE ) is supplied from the battery 3 via the DC impedance R _LIM and the resistors R ₁ and R ₂ to turn on. When the transistor 9 is turned on, the current I flows through the DC impedance R _LIM .

Since the base-emitter voltage V _BE of the transistor 10 is equal to the voltage drop due to the DC impedance R _{LI M} , the current I is a steady current value (2 in the embodiment).
Amperage), DC impedance R
Due to the increased voltage drop in _LIM , transistor 10
Turns on. When the transistor 10 is turned on, the transistor 9 is turned off, and the current from the external power source battery 3 to the output terminals 2A and 2B is cut off.

The current limiter 4A having this configuration has a relatively high DC impedance RLIM of 0.3 ohms, a large amount of self-discharge (base current), and the above-mentioned problem of backflow must be solved.

The current limiter 4B according to the second embodiment is
As shown in FIG. 4, the circuit configuration is such that the DC impedance RLIM of the first embodiment is reduced.
1, 12, 13 and DC impedance R _LIM (0.1 ohm in the embodiment), resistor R ₃ (100 ohm in the embodiment), R ₄ (470 in the embodiment).
0 ohm) , R ₅ (1800 ohms in the embodiment), R ₆ (6800 ohms in the embodiment), and a capacitor C.

The collector of the transistor 11 is connected to the output terminal 2
Connected to the A, the emitter is connected to one end of the DC impedance R _LIM, the other end of the DC impedance R _LIM connected to the positive terminal of the external power source of the battery 3, and an output terminal 2B the negative terminal of the battery 3 in the external power supply Connecting. As a result, when the transistor 11 is turned on, a flow path for the current I is formed through the DC impedance R _LIM .

The base of the transistor 11 is a resistor R₃of
Connect with one end, resistor R₃Connect the other end to the output terminal 2B
To do. Resistor R_Four, R_Five, R₆Connected in series,
Resistor R of the column resistor_FourConnect the side terminal to the transistor 11
And the resistor R ₆Connect the side terminals to the external power supply
Connect to the negative terminal of Terry 3.

The base and collector of the transistor 12 are connected together with the connection point of the resistors R ₅ and R ₆ , and the emitter thereof is connected with the emitter of the transistor 11. The emitter of the transistor 13 is connected to the positive terminal of the battery 3 of the external power source, the base is connected to the connection point of the resistors R ₄ and R ₅ , and the collector is connected to the base of the transistor 11.

The current limiter 4B having the above structure operates as follows. When the current I is equal to or less than a predetermined current value, that is, a steady current value (2 amperes in the embodiment), the transistors 12 and 13 are turned off, so that the transistor 11 is turned on and output from the battery 3 of the external power supply. A voltage is supplied to the terminals 2A and 2B.

The current I is a steady current value (2 in the embodiment).
Amperage), DC impedance R
The voltage drop of _LIM becomes large, and as a result, the transistor 12 or the transistor 13 corresponding to the direction of the current I is turned on. Therefore, the transistor 11 is turned off,
The voltage supply from the battery 3 of the external power supply to the output terminals 2A and 2B is cut off.

The current limiter 4B having this structure has a large amount of self-discharge and must solve the above-mentioned problem of backflow.

The current limiter 4C according to the third embodiment is
As shown in FIG. 5, the transistor 1 has the circuit configuration in which the self-discharge amount is reduced as in the first and second embodiments.
4, 15 and N-channel MOSFETs 16 and 17,
DC impedance R _LIM (0.3 ohm in the embodiment) , A resistor R ₇ (10 K ohms in the embodiment), and a capacitor C.

The drain of the MOSFET 16 is connected to the output terminal 2
Connect is B, connected back to back to sources of MOSFETs 16, the drain of the MOSFET17 connected to one end of the DC impedance R _LIM, the other end of the DC impedance R _LIM connected to the negative terminal of the battery 3, the battery 3 The positive terminal of is connected to the output terminal 2A.

The gates of the MOSFETs 16 and ₁₇ are connected to one end of the resistor R ₇ , and the other end of the resistor R ₇ is connected to the output terminal 2A. Thereby, the MOSFET 16,
A bidirectional path of the current I is formed through 17 and the DC impedance R _LIM (0.3 ohm in the embodiment).

Next, the collector of the transistor 14 is set to M
Connect to the gates of OSFETs 16 and 17, and set the base to MO
The drain is connected to the SFET 17, and the emitter is connected to the negative terminal of the battery 3 of the external power supply. Further, the collector of the transistor 15 is connected to the gates of the MOSFETs 17 and 18, the base is connected to the negative terminal of the battery 3, and the emitter is connected to the drain of the MOSFET 17.

The current limiter 4C having the above structure operates as follows. When the current I is a steady current value (2 amperes in the embodiment) or less, the DC impedance R
_Since the base-emitter voltage V _BE generated by the voltage drop of _LIM is insufficient, the transistors 14 and 15 are off. Further, since appropriate voltages are supplied to the gates of the MOSFETs 16 and ₁₇ through the resistor R ₇ ,
A current I flows through the DC impedance R _LIM .

Therefore, when the current exceeds the steady current value (2 amperes in the embodiment), the DC impedance R
_The base-emitter voltage V _BE generated by the voltage drop of _LIM increases, and as a result, the transistor 14 or the transistor 15 is turned on. Therefore, MOSFET
16 or MOSFET 17 turns off and battery 3
The supply of current from the output terminals to the output terminals 2A and 2B is cut off.

In the current limit 4C having such a structure, the DC impedance R _{LI M} is as high as 0.3 ohms, and the use of the MOSFET causes the above-mentioned reverse current to be a steady current value (2 amps in the embodiment). Can be suppressed to.

The current limiter 4D according to the fourth embodiment is
As shown in FIG. 6, the circuit configuration is such that the self-discharge amount is smaller than that in the first and second embodiments and the DC impedance RLIM is smaller than that in the second and third embodiments. , Transistors 18, 19, 20, and 21,
N-channel MOSFETs 16 and 17, DC impedance R _LIM (0.1 ohm in the embodiment), and resistor R ₇ (10 K ohm in the embodiment). , R ₈ (6800 ohms in the example), R ₉ (100 ohms in the example), R ₁₀ (5600 ohms in the example).
Ohm), R ₁₁ (6800 ohms in the example),
It is composed of R ₁₂ (1800 ohms in the embodiment), R ₁₃ (4700 ohms in the embodiment), and a capacitor C.

The drain of the MOSFET 16 is connected to the output terminal 2
Connect is B, connected back to back to sources of MOSFETs 16, the drain of the MOSFET17 connected to one end of the DC impedance R _LIM, the other end of the DC impedance R _LIM connected to the negative terminal of the battery 3, the battery 3 The positive terminal of is connected to the output terminal 2A.

[0066] Also, connect the gates of MOSFET16,17 and one end of the resistor R _7, connecting the other end of the resistor R ₇ and the output terminal 2A. Thereby, the MOSFET 16,
A flow path in both directions of the current I is formed through 17 and the DC impedance R _LIM .

Next, the resistor R₈, R₉, R_TenIn series
Connect and resistor R of this series resistor ₈Output terminal
Connected to child 2A and its resistor R_TenBattery 3 on the side terminal
Connect to the negative terminal of. Also, the resistor R₁₁, R₁₂,
R₁₃Is connected in series, and the resistor R of this series resistor is₁₁On the side
Connect the terminal to the positive terminal of the battery 3 and connect the resistor R
₁₃DC impedance R on the side terminal_LIMAnd MOSFET
Connect to the connection point with 17.

In addition, the base of the transistor 18 is a resistor R
Connected to the connection point of ₉ and R ₁₀ , and its collector is MOSFE
It is connected to the gates of T9 and T10, and its emitter is connected to the connection point of the DC impedance R _LIM and the MOSFET 17.

Further, the base of the transistor 19 is connected to the connection point of the resistors R ₈ and R ₉ together with the collector, and the emitter is connected to the negative terminal of the battery 3 of the external power supply. The base and collector of the transistor 20 are connected to resistors R ₁₁ and R
_It is connected to the connection point of ₁₂ and its emitter is connected to the connection point of the DC impedance R _LIM and the MOSFET 17.

Further, the base of the transistor 21 is connected to the connection point of the resistors R ₁₂ and R ₁₃ , and the collector is MOSFE.
It is connected to the gates of T9 and T10, and the emitter is connected to the negative terminal of the battery 3 of the external power supply.

The current limiter 4D constructed as described above
Works as follows: DC impedance R _LIM
When the current flowing through the transistor is a steady current value (2 amperes in the embodiment) or less, the transistors 18, 19, 20, 21 are
Is off, so MOSFET 16 or MOSFE
The gates of T17 predetermined voltage is supplied through a resistor R _7, therefore, the current I flowing through the MOSFETs 16, an output terminal 2A from the battery 3, the power is supplied to 2B.

The current I is a steady current value (2 in the embodiment).
Amperes), depending on the direction of the current I,
Transistor 18, 19 or transistor 20, 21
Is turned on, as a result, the MOSFETs 16 and 17 are turned off, and the battery 3 of the external power source outputs the output terminals 2A and 2
The power supply to B will be cut off.

The current limiter 4D having such a configuration
Can bring the above reverse current up to about 100 mA or less.

In this way, in the current limiters 4A, 4B, 4C, and 4D without taking into consideration the safety problem such as heat generation, the self-discharge amount is large, but the first and second circuits are realized by simplifying the circuit structure. The third embodiment and the fourth and third embodiments in which the circuit configuration is made more complicated than the first and second embodiments in order to reduce the self-discharge amount, but the problem of backflow is improved are effective.

That is, in the circuits shown in the first and second embodiments, the above-mentioned problem of backflow has not been solved, but the control in the switching element is performed with a steady current value (2 amperes in the embodiment). Since it is operated, it is possible to prevent further current from flowing. Therefore, even if the reverse flow is unlimited, the current is limited by the steady current value, so that no more reverse current is generated.

Further, in the circuits shown in the third and fourth embodiments, the problem of the backflow shown above is caused by the MOSFET.
The circuit configuration is limited by using. Therefore, the circuit structure has a so-called double protection that controls the steady current value and suppresses the backflow to a certain limit.

The control of the power supplies connected in parallel is as follows.
It goes without saying that all of the control of the currents flowing into each other are targeted, and the present invention is not limited to the first to fourth embodiments.

Next, a countermeasure against the heat generation of the current limiter caused by the voltage difference between the internal power source and the external power source, that is, the safety compensating means will be described. As a premise, if a voltage difference occurs between both power supplies connected in parallel, the resistance including the internal resistance cannot be zero. Therefore, a current flows due to the voltage difference, and heat generation equal to the product of the resistance value between the two power supplies connected in parallel and the square of the flowing current value is generated.

Normally, when the external battery adapter 1 is used, the voltage of the battery 3 of the external power supply is considered to be higher than the voltage of the battery 7 of the internal power supply in many cases. In such a case, a closed circuit as shown in FIG. 7 is formed,
The charging current for the battery 7 of the internal power source flows from the battery 3 of the external power source through the current limiter 4, and continues until the voltages of both are equal. This current causes heat generation of the current limiter 4, and if it is large, it becomes a problem.

Now, the voltage and the internal resistance of the battery 7 of the internal power source are V ₁ and r ₁ , respectively, the voltage and the internal resistance of the battery 3 of the external power source are V ₂ and r ₂ , respectively, between the negative values of the battery 7 and the battery 3. The total resistance connecting the two is represented by R, the series resistance of the current limiter 4 is represented by R _LIM , and the current flowing through the current limiter 4 is represented by I.

The voltage drop V _LIM and the power consumption P _LIM in the current limiter 4 are expressed as follows. V _LIM = V ₂ −V ₁ −I (r ₁ + r ₂ + R + R _LIM ) P _LIM = V _LIM × I

As an extreme example, the voltage V ₂ of the battery 3 of the external power supply is 8.4 volts, the voltage V ₁ of the battery 7 of the internal power supply is 0 volt, the current I flowing through the current limiter 4 is 2 amps, the internal power supply and Internal resistance of external power supply r ₁ = r ₂ =
Assuming a 0.4 ohm case, the voltage drop across the current limiter 4 is V _LIM = 8.4 volts-0 volts-2 amps * (0.4 ohm + 0.4 ohm + 0.3 ohm +
0.2 ohm) = 5.8 volts, so the power consumption in the current limiter 4 is: P _LIM = V _LIM × I = 5.8 volts × 2 amps = 1
It will be 1.6 watts.

Actually, it is not practical to attach a current limiter capable of withstanding heat generation equivalent to power consumption of power PLIM = 11.6 watts. However, when the battery 7 of the internal power source and the battery 3 of the external power source are used together, it is considered that the voltage V ₁ of the battery 7 of the internal power source becomes 0 volt as in the above example is extremely rare.

Because, normally, a circuit for controlling over-discharge and over-charge is provided to protect the battery. For example, when the voltage V1 of the battery 7 of the internal power source becomes 4.8 V or less, the over-discharge prevention circuit is provided. Works, and the voltage does not fall below that. Therefore, the minimum value of the voltage V ₁ of the battery 7 of the internal power supply may be considered to be the over-discharge voltage value (for example, 4.8 V) in practical use.

Therefore, the voltage V ₁ of the battery 7 of the internal power source
= 4.8 V, the voltage drop V _LIM = 1 V and the power consumption P _LIM = 2 W, and the heat generation does not cause any practical problems. While the electronic device (camcorder used in the embodiment) is driven, heat generation of about 0.3 to 0.5 watts increases, so the minimum value of the voltage V ₁ of the battery 7 of the internal power supply is 5.2.
It is recommended to set to bolt.

Based on the above consideration, in the present invention,
Basic circuit of current limiter (for example, the above-mentioned first to fourth implementation
In addition to "Example," the voltage difference V between the internal power supply and the external power supply₂-V₁
Is the voltage V₂When the ratio exceeds a certain ratio, that is, V₂
-V₁> V₀, (However, V ₀= A x V₂) Condition
Then, from the set the power supply of the external battery adapter 1 side
We decided to add a circuit for heat generation called "disconnect"
It was

For example, when a = 0.38 is set, in the above case, when the voltage V ₂ on the battery 3 side of the external power supply is 8.4 volts, the voltage V ₁ > 5.2 on the battery 7 side of the internal power supply.
If it is a bolt, the external battery adapter 1 can be used.

If the voltage V ₂ of the battery 3 of the external power source is < ₂
If it is 8.4 volts, the voltage V of the battery 7 of the internal power supply
The range of ₁ will be wider.

[0089] A battery configured to satisfy the above conditions.
Two examples of flow limiters are shown in FIGS. 8 and 9.

The current limiter 4 of the fifth embodiment shown in FIG.
E is the current limiter 4C of the third embodiment shown in FIG. 5 as a basic circuit, to which a heat generation countermeasure circuit which is a safety compensating means satisfying the above conditions is added, and description of the basic circuit is omitted. To do.

The heat generation countermeasure circuit 4G includes a transistor 22,
23 and 24 and resistors R ₁₄ (22K ohm in the embodiment), R ₁₅ (22K ohm in the embodiment), R ₁₆ (56K ohm in the embodiment), R ₁₇ (3K in the embodiment).
3K ohm).

Resistor R constituting this heat generation countermeasure circuit 4G
₁₆ and R ₁₇ are connected in series, the terminal on the resistor R ₁₆ side of this series circuit is connected to the positive terminal of the battery 3, and the terminal on the resistor R ₁₇ side is connected to the negative terminal of the battery 3.
The resistance values of the resistors R ₁₆ and R ₁₇ are set so that the voltage across the resistor R ₁₇ becomes the voltage V ₀ (= a × V ₂ ). For example, a = 0.38.

[0093] Then, the emitter of transistor 22 is connected to the positive terminal of the battery 3 (the output terminal 2A), a collector connected to one end of the resistor R _7, and the gate of MOSFET16,17 the other end of the resistor R ₇ Connecting.

[0094] Also, connect the base of transistor 23 and one end of the resistor R _14, the output terminal 2B and the other end of the resistor R ₁₄
Connect with. The collector of the transistor 23 is the battery 3
Connected to the positive terminal of the
It is connected to the negative terminal of the battery 3 together with the emitter of 4.

Further, the collector of the transistor 24 is connected to the base of the transistor 22, and the base is connected to the connection point of the resistors R ₁₆ and R ₁₇ .

Heat generation countermeasure circuit 4G configured as described above
Works as follows: Resistor R₁₆, R₁₇That's it
The resistance value of this is resistor R₁₇Is the above voltage V
₀(= A × V₂) Is set to
(V₂-V₁) ≦ a × V₂Transistor 1 while
4 and 15 are turned on and therefore transistor 22 is turned off.
The operation is similar to that of the circuit shown in FIG.

When the voltage (V ₂ −V ₁ )> a × V ₂ , the voltage across the resistor R _{15 and} the voltage across the resistor R ₁₇ (that is, a ×).
V ₂ ), the base-emitter voltage V _BE of the transistor 24 becomes smaller than a predetermined value, and as a result, the transistor 24 is turned off. When transistor 24 turns off, transistor 22 turns off and the MOSFET
16, 17 are turned off. As a result, the voltage supply from the battery 3 to the output terminals 2A and 2B is cut off.

The current limiter 4 of the sixth embodiment shown in FIG.
F has the current limiter 4D shown in FIG. 6 as a basic circuit, and the same heat generation countermeasure circuit 4G as that of the fifth embodiment shown in FIG. Omit it.

The heat generation countermeasure circuit 4G, which is a safety compensating means, is not limited to heat generation caused by the voltage difference between the internal power supply and the external power supply, and limits the current flowing from the internal power supply to the external power supply, for example, to the battery. The circuit also takes into consideration so-called safety such as protecting the state.

[0100]

As described above, the power supply adapter for electronic equipment according to the present invention has the following effects.

(1) Since the current limiter means for limiting the bidirectional current flowing from the internal power source to the external power source or from the external power source to the internal power source to a predetermined value is provided, the on / off control of the switch for switching is unnecessary. Since the control system can be simplified, it is possible to realize low cost, and it is possible to drive by using both of them without being limited to the drive by one power supply, and it is possible to significantly extend the usable time that can be driven. It has an extremely excellent effect.

Further, even if one of them is replaced during use, the continuous operation can be maintained, which is an extremely excellent effect that the electronic device can be easily used.

(2) The current limiter means cuts off the power supply from the external power supply when the power supply from the external power supply to the internal power supply side exceeds a predetermined current value. Even if there is a voltage difference between the two, it is possible to prevent adverse effects on the power source of the other party by backflowing, and it is extremely easy to use without the need to consider how to limit to either one as in the past. Play.

(3) Since the predetermined current value is detected by the switching element, the structure of the current limiter means can be realized easily and at low cost, and the miniaturization and the safety can be improved. It has an extremely excellent effect.

(4) The switching element is a MOS type F
By including the ET, it is possible to realize the current limiter means that suppresses the amount of self-discharge and suppresses the reverse flow of the current, and it is extremely possible to control harmful currents due to heat and accurate voltage. It has an excellent effect.

(5) Since the current limiter means is provided with the safety compensating means for detecting the voltage difference between the internal power source and the external power source, even if the voltage difference occurs, the harmful effect due to heat can be prevented.
It has an extremely excellent effect that the safety and the reliability can be enhanced even in parallel use.

(6) The safety compensating means is normally carried out by interrupting the supply of the voltage from the external power source at least when it is outside the predetermined voltage value range based on the overdischarge voltage value of the internal power source. This has an extremely excellent effect that a harmful effect due to heat due to parallel connection due to control of over-discharge and over-charge can be prevented and a long-time use condition can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the basic configuration of a power adapter for an electronic device according to the present invention.

FIG. 2 is an explanatory diagram showing a connection when the external power supply is used.

FIG. 3 is an explanatory diagram showing a configuration of a first embodiment of the external power supply.

FIG. 4 is an explanatory diagram showing a configuration of a second embodiment of the external power supply.

FIG. 5 is an explanatory diagram showing a configuration of a third embodiment of the external power supply.

FIG. 6 is an explanatory diagram showing a configuration of a fourth embodiment of the external power supply.

FIG. 7 is an explanatory diagram for analysis of heat generation of the current limiter when the power supply adapter is used.

FIG. 8 is an explanatory diagram showing a configuration of a fifth embodiment of an external power supply having the same heat generation suppression circuit.

FIG. 9 is an explanatory diagram showing a configuration of a sixth embodiment of an external power supply having the heat generation suppressing circuit.

FIG. 10 is an explanatory diagram of a conventional power supply adapter.

[Explanation of symbols]

1 External Battery Adapter (Adapter for Power Supply) 2A, 2B Output Terminal 3 External Power Supply (Battery) 4 Current Limiter 5 Set 6 Internal Circuit 7 Internal Power Supply (Battery) 8A, 8B Input Terminal 9-15, 18-24 Transistor 16, 17 MOSFET C Capacitor I Current R _{1 to} R ₁₇ , R, r ₁ , r ₂ Resistor R _LIM DC impedance

Claims (6)

[Claims] 1. An electronic device comprising an internal power supply and an input terminal for connecting an external power supply, wherein the external power supply side is provided with an output terminal detachably connected to the input terminal. The power supply adapter for electronic equipment, wherein the terminal is provided via a current limiter means for limiting a current flowing in both directions of the external power supply and the internal power supply to a predetermined value. 2. The current limiter means is configured to cut off the power supply from the external power supply when the power supply from the external power supply to the internal power supply exceeds a predetermined current value. Item 1. An electronic device power supply adapter according to item 1. 3. A switching element is used to detect the current equal to or higher than the predetermined current value.
Alternatively, the power supply adapter for the electronic device described in 2. 4. The switching element includes a MOS type F
The power supply adapter for an electronic device according to claim 3, further comprising ET. 5. The power supply adapter for electronic equipment according to claim 1, wherein the current limiter means is provided with a safety compensating means for detecting a voltage difference between the internal power supply and the external power supply. . 6. The safety compensating means is configured to cut off the supply of voltage from an external power supply at least when it is outside a predetermined voltage value range based on the overdischarge voltage value of the internal power supply. The power supply adapter for the electronic device according to item 5.