JPH08250158A - Charging-terminal short-circuit protection circuit of battery pack - Google Patents

Abstract

PURPOSE: To provide a charging-terminal short-circuit protection circuit of a battery pack which can surely provide protection against short circuits using simple constitution. CONSTITUTION: This charging-terminal short-circuit protection circuit is for a battery pack having a battery, charging terminals, and output terminals, and designed to supply a charging current from a charger to the battery through the charging terminals and to supply the current from the battery to portable equipment through the output terminals. A FET 2-3 is provided between the battery 2-12 and the charging terminals T3 , T4 , and a toroidal transformer 2-5 is provided which, when a short circuit occurs between the charging terminals T3 , T4 , detects a short-circuit current Is flowing from the battery 2-12. A control means is provided which normally keeps the FET 2-3 on and which turns off the FET 2-3 at which the toroidal transformer 2-5 has detected the short-circuit current Is and then turns the FET 2-3 on and off only for a short time after a predetermined lag time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging terminal short circuit protection circuit for a battery pack used in a mobile device such as a mobile phone.

[0002]

2. Description of the Related Art Conventionally, a technique of this kind has been disclosed in Japanese Patent Laid-Open No.
There is one disclosed in Japanese Patent Publication No. 96758. FIG. 3 is a diagram showing an example of a power supply terminal short circuit protection circuit of a conventional battery pack. The battery pack 4 is used as a power source of a mobile device, and as shown in the figure, the conventional battery pack 4 is composed of a switch 4-1, a terminal 4-2, a terminal 4-3, and a battery 4-4. When mounting on the equipment (omitted), the terminal 4-
The switch 4-1 is mounted so as to be mechanically pushed and operated at the same time when the terminal 2 and the terminal 4-3 come into contact with the terminal on the side of the device used.

When the battery pack 4 is attached to a portable device, the terminal 4-2 and the terminal 4-3 are used as power supply terminals, and when attached to the charger, the terminal 4-2 and the terminal 4 are used.
-3 is used as a charging terminal. For example, at the time of charging, the switch 4-1 is activated when the battery pack is attached to the charger, and the terminal 4-2,
Charging current is supplied from the terminal 4-3 to the battery 4-1 for charging.

Since the switch 4-1 is in an open state when the battery pack 4 is not used, the battery 4-4 is protected from being short-circuited even if a conductor contacts between the terminals 4-2 and 4-3. You can

In addition to this, as a measure for preventing a battery short circuit, a magnetically actuated re-driller is used instead of the switch 4-1, a magnet is attached to the side of the equipment to be used, and a re-driller is attached when the battery pack is mounted. Applying that the temperature rises due to the heat generated by the short-circuit current at the time of short circuit, instead of the switch 4-1, a poly switch (PTC) whose resistance value rapidly increases with temperature rise is used. A method of limiting the short-circuit current, a method of blocking the terminals 4-2 and 4-3 with an insulator so that the conductor does not directly touch the terminals when not in use, and the like have been devised.

[0006]

However, the above-mentioned method of mounting the mechanically operated switch 4-1 requires adjustment of the mechanism and has a problem in reliability when repeatedly used, and the magnetically operated lead reel relay is used. There is a problem that the method of using a magnetic switch causes malfunctions due to the approach or contact of a magnetic product such as a magnetic necklace or the adhesion of iron powder, and the method of using a polyswitch is difficult to take measures against an incomplete short state. In addition, there is a problem in that it is mechanically difficult to automatically perform this blinding by a method in which the terminals are covered with an insulator so that the conductor does not directly touch the terminals when not in use.

In addition, instead of the switch 4-1, a switch driven by an electric signal is used, the battery pack 4 is provided with terminals 4-2 and 4-3, and terminals for driving the switch. A method in which the switch is operated only when the battery pack is attached to the charger and a voltage is applied to the terminal can be considered, but it is necessary to provide a terminal for driving the switch, and the number of terminals between the battery pack and the charger is reduced. It also increases mechanical constraints and increases costs.

The present invention has been made in view of the above points, and an object of the present invention is to provide a charging terminal short circuit protection circuit for a battery pack which eliminates the above problems and can surely perform short circuit protection with a simple structure.

[0009]

To solve the above problems, the present invention comprises a battery, a charging terminal and an output terminal, and supplies a charging current from a charger to the battery through the charging terminal,
In a charging terminal short-circuit protection circuit of a battery pack configured to supply current from the battery to a portable device through an output terminal, when an electronic switch is provided in series between the battery and the charging terminal and the charging terminal is short-circuited A short-circuit detecting means for detecting a short-circuit current flowing from the battery is provided, and when the short-circuit detecting means detects the short-circuit current, the electronic switch is turned off, and the ON / O is turned on for a predetermined short time after a predetermined delay.
It is characterized in that a control means for performing FF control is provided.

[0010]

According to the present invention, when the charging terminal is short-circuited and the short-circuit detecting means detects the short-circuit current, the control means turns off the electronic switch and turns on / off for a predetermined delay time and for a predetermined short time. Since control is performed, by adjusting this delay time and a predetermined short time to turn on,
Since the energy of the short-circuit current can be made extremely small, the battery can be protected even if the charging terminal is short-circuited for a long time.

Further, only two charging terminals (+ terminal and-terminal) are required between the battery pack and the charger, and the circuit configuration is simple and there is no mechanical operation, so there are few mechanical restrictions and charging terminal short-circuit protection. The circuit can be configured and reliability is improved. The above battery pack uses a lithium ion battery as a battery. Since the lithium ion battery requires accurate charge current control and charge voltage control, it is a diode for preventing backflow.
In such cases, the voltage drop due to temperature change is unstable and it cannot be used.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing an example of a charging terminal short circuit protection circuit for a battery pack of the present invention. As shown in the figure, the battery pack 2 detects the resistor 2-1, the resistor 2-2, the FET (field effect transistor) 2-3 for turning off the short circuit current Is, the diode 2-4, and the short circuit current Is. Toroidal transformer 2-5, capacitor 2-6 for determining the time constant, resistor 2-7, resistor 2-8, transistor 2-9, diode 2-10, waveform shaping circuit 2-11, chargeable A battery 2-12, a charging terminal T ₃ and a charging terminal T ₄ to which the charging current i is supplied from the charger 1, and an output terminal T ₅ and an output terminal T ₆ for supplying power to the portable device 3.

The charging terminal T ₃ of the battery pack 2 is the battery 2-1.
2 to the + side and the output terminal T ₅ , and the charging terminal T ₄ (− side) is F
The battery 2 passes through the primary coil of the toroidal transformer 2-5 via the drain terminal D and the source terminal S of the ET 2-3.
12 - are connected to the side and the output terminal T _6. F
The gate terminal G of ET2-3 is a resistor 2-1 and a resistor 2-
It is connected to the charging terminal T ₄ through 2.

A diode 2-4 and a capacitor 2-6 are connected in series to the secondary coil of the toroidal transformer 2-5, and the connection point between the capacitor 2-6 and the diode 2-4 is a resistor 2-. Base terminal b of the transistor 2-9 through 7
Connected to. The emitter terminal e of the transistor 2-9
Is connected to the charging terminal T ₆ via the diode 2-10. The collector terminal c of the transistor 2-9 is a resistor 2-
It is connected to the charging terminal T ₃ (+ side) via 8 and its output signal is input to the waveform shaping circuit 2-11. The output of the waveform shaping circuit 2-11 is connected to the connection point of the resistor 2-1 and the resistor 2-2.

The charger 1 includes a power supply circuit 1-1 for converting AC 100 V into a DC voltage for charging, a control unit 1-2 for controlling the charging voltage and the charging current i, and an output terminal T ₁ (+) for supplying the charging current i. Side) and an output terminal T ₂ (− side). The mobile device 3 is usually equipped with the battery pack 2, and power is supplied from the battery 2-12 via the output terminals T ₅ and T ₆ . When the battery pack 2 is attached to the charger 1 as it is during charging, the charging terminal T ₃ and the charging terminal T ₄ of the battery pack 2 come into contact with the output terminal T ₁ and the output terminal T ₂ of the charger 1, respectively. The charging current i is supplied to the battery pack 2. Although not shown in the above example, the charger 1 is a battery pack 2
Is mechanically detected, and the charging current i is supplied to the battery pack 2 after the mounting of the battery pack 2 is detected.

FIG. 2 is a diagram showing current and voltage waveforms at various parts of the battery pack when the charging terminals T ₃ and T ₄ are short-circuited.
The operation of this embodiment will be described with reference to FIGS. The battery pack 2 is attached to the charger 1, when it is charged in the battery 2-12 through charging terminals T _3, T _4, FET 2-3 of gate - in DOO terminal G resistors 2-1 and resistor 2- A gate voltage V _G is applied from the charging terminal T ₃ via FET 2,
The drain terminal D and the source terminal S of No. 3 are turned on.
Therefore, the charging current i flows as shown by the arrow and charges the battery 2-12. In addition, the moment of charging is a toroidal transformer 2-
The secondary coil voltage of 5 is induced, but the current due to the voltage is blocked by the diode 2-4 and is not output.

When the battery pack 2 is not charged, the battery pack 2 is removed from the charger 1, but the battery 2-1 is connected to the resistor 2-1 and the resistor 2-.
Since the gate voltage V _G is applied via the FET 2,
The drain terminal D and the source terminal S of No. 3 are in the ON state.
Therefore, when the charging terminal T ₃ and the charging terminal T ₄ are short-circuited, FE
The + voltage of the charging terminal T ₃ is applied to the drain terminal D of T2-3, and the short-circuit current Is from the battery 2-12 side is F as shown by the arrow.
It flows from the drain terminal D of ET2-3 through the source terminal S and the primary coil of the toroidal transformer 2-5 to the battery 2-12.

At the time of the above-mentioned short circuit, a voltage is induced in the secondary coil of the toroidal transformer 2-5, and a current is instantaneously forwarded through the diode 2-4 (see short circuit detection signal _IT FIG. 2 (a)). Flows and charges the capacitor 2-6. The voltage of the charged capacitor 2-6 is the resistor 2-7 and the transistor 2
A discharge is performed through the base 2 and the emitter of −9 and the diode 2-10. Therefore, as shown in FIG. 2B, the base current Ib of the transistor 2-9 flows while being attenuated according to the time constant determined by the capacitance of the capacitor 2-6, the resistor 2-7, and the resistance value of the circuit element.

While the base current Ib is sufficiently flowing between the collector c and the emitter e of the transistor 2-9, it is in the off state when the base current Ib decreases,
The output voltage Vc of the collector c of the transistor 2-9 is shown in FIG.
It changes as shown in (c) and is input to the waveform shaping circuit 2-11.

The waveform shaping circuit 2-11 is a transistor 2-
The output voltage Vc of 9 is converted into the low level voltage and the high level voltage shown in FIG. 2D, and the FET 2-3 is connected via the resistor 2-2.
Input to the gate terminal G of (the gate of the FET 2-3 of FIG. 2).
Voltage V _G ). The FET 2-3 is turned off when the gate voltage V _G is at a low level and turned on when the gate voltage is at a high level, so that it is turned off when the output of the waveform shaping circuit 2-11 is at a low level and turned on when the output is at a high level.

That is, a short circuit occurs and the transistor 2-9
Until the output voltage Vc of the FET reaches a high level, FET2
-3 is turned off, and the short circuit current Is is blocked (blocked). When the base current Ib of the transistor 2-9 is attenuated and the output voltage Vc reaches a high level, the waveform shaping circuit 2-1.
The high level voltage V _{G for a} short time (pulse) from 1 is input to the gate terminal G of the FET 2-3 through the resistor 2-2, and the FET 2-3 is turned on for a short time. At this time, if the charging terminals T ₃ and T ₄ are in the short-circuited state, the above-described operation is repeated and the pulsed short-circuit current Is flows.

Since the pulse interval of the short circuit current Is is determined by the time constant depending on the capacitance of the capacitor 2-6, the resistance value of the resistor 2-7 and other circuit elements, it can be set sufficiently long, and The pulse width of the short-circuit current Is is determined by the waveform shaping circuit 2-11 and can be controlled to several microseconds (μs) in this embodiment, so the energy of the short-circuit current Is can be made extremely small. Becomes Therefore, the battery 2-12 is sufficiently protected even if the charging terminals T ₃ and T ₄ are short-circuited for a long time. In addition, only two charging terminals (+ terminal and-terminal) are required between the battery pack 2 and the charger 1, and the circuit is simple and there is no mechanical operation, so there are less mechanical restrictions and reliability is high and the price is low. Become.

Further, since the toroidal transformer 2-5 detects the short-circuit current Is opposite to the charging current i, the toroidal transformer 2-5 has good sensitivity and is incomplete due to an unstable conductor such as a chain between the charging terminals T ₃ and T _4. It works properly even if it touches.

[0024]

As described above, according to the present invention, the following excellent effects can be obtained. (1) The energy of the short-circuit current can be made extremely small by adjusting the predetermined delay time in which the electronic switch of the control means is turned on for a short time with a predetermined time delay and the ON time. The battery can be protected even if the charging terminal is short-circuited for a long time.

(2) Also, between the battery pack and the charger is 2
Since only one charging terminal (+ terminal and − terminal) is required and the circuit configuration is simple and there is no mechanical operation, there are few mechanical restrictions, and a charging terminal short circuit protection circuit can be configured and reliability is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a charging terminal short circuit protection circuit of a battery pack of the present invention.

FIG. 2 is a diagram showing the current and voltage of each part of the battery pack when the charging terminal is short-circuited.

FIG. 3 is a diagram showing an example of a conventional charging terminal short circuit protection circuit for a battery pack.

[Explanation of symbols]

 1 Charger 1-1 Power Supply Circuit 1-2 Control Part 2 Battery Pack 2-1 Resistor 2-2 Resistor 2-3 FET (Field Effect Transistor) 2-4 Diode 2-5 Toroidal Transformer 2-6 Capacitor 2-7 resistor 2-8 resistor 2-9 transistor 2-10 diode 2-11 waveform shaping circuit 2-12 battery 3 mobile device

Claims (1)

[Claims] 1. A battery, a charging terminal, and an output terminal are provided, and a charging current is supplied from a charger to the battery through the charging terminal, and a current from the battery is supplied to a portable device through the output terminal. In the charging terminal short-circuit protection circuit of the battery pack, an electronic switch is provided in series between the battery and the charging terminal, and short-circuit detection means for detecting a short-circuit current flowing from the battery when the charging terminal is short-circuited is provided. Charging a battery pack, characterized in that when the short-circuit detection means detects a short-circuit current, the electronic switch is turned off and ON / OFF control is performed to turn on the electronic switch for a predetermined short time after a predetermined time delay. Terminal short circuit protection circuit.