JP2002238174A - Charging/discharging control circuit and rechargeable power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance safety and also improve performance of a charging/ discharging control circuit and a rechargeable power supply. SOLUTION: There is provided a circuit, having a delay time to surely detect overcurrent condition, when the overcurrent condition is canceled from the overcurrent detecting circuit in the charging/discharging control circuit 102. Accordingly, an FET-A 112 will not be turned on during delay time with an overcurrent cancellation delay circuit 128, even when an external terminal -VO 105 changes transitionally, after an overcurrent detecting comparator 117 detects an overcurrent, with capacity between drain and source, load and inductive element of wiring of the FET-A 112 and the overcurrent detecting comparator 117 detects overcurrent cancellation. If such a variation is completed during this period, the overcurrent detecting comparator 117 stable results in protecting the overcurrent condition, in order to detect the overcurrent condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge / discharge control circuit capable of controlling charging / discharging of a secondary battery by turning on / off a switch circuit, and a rechargeable power supply using the circuit.

[0002]

2. Description of the Related Art As a conventional rechargeable power supply comprising a secondary battery, a power supply as shown in a circuit block diagram of FIG. 2 has been known. For example, such a structure is disclosed in Japanese Unexamined Patent Publication No. Hei 4-75430 "Rechargeable power supply device".
That is, the secondary battery 101 is connected to the external terminal -V0 105 or + V0 104 via the switch circuit 103. Further, the charge / discharge control circuit 1 is connected in parallel with the secondary battery 101.
02 is connected. This charge / discharge control circuit 102
A function of detecting the voltage of the secondary battery 101 is provided. The secondary battery 101 is in an overcharged state (a state in which the battery is higher than a predetermined voltage value; hereinafter, this state is referred to as an overcharge protection state) or an overdischarged state (a state in which the battery is lower than a predetermined voltage value. In either case, the charge / discharge control circuit 102 outputs a signal so that the switch circuit 103 is turned off. External terminal + V
By stopping the discharge when 0 104 reaches a certain voltage, the current flowing through the switch circuit 103 can be limited. That is, when an excessive current flows, the discharge can be stopped (overcurrent control). Hereinafter, this state is called an overcurrent protection state.

As another example of a conventional rechargeable power supply comprising a secondary battery, a power supply as shown in a circuit block diagram of FIG. 3 is also known. In this circuit, the switch circuit 103 shown in FIG. 2 is connected in series with the negative electrode 111 of the secondary battery.

FIG. 4 is a conventional circuit block diagram of a specific charge / discharge control circuit. The secondary battery 101 is connected to the external terminal -V0 105 via the switch circuit 103. The switch circuit 103 is composed of two N-ch FETs. The voltage of the secondary battery 101 is detected by the charge / discharge control circuit 102. Charge / discharge control circuit 102
Are overcharge detection comparator 119, overdischarge detection comparator 118, overcurrent detection comparator 117, reference voltage circuit A 116, reference voltage circuit B 114, voltage division circuit A 120, voltage division circuit B 121, output control logic circuit 124, etc. It is composed of The charge / discharge control circuit 102 is connected to the switch circuit 1 by the signal lines 107A and 107B.
03 and ON / OF of the switch circuit.
An F signal is transmitted. A charger 108 for charging the secondary battery 101 and a device that can be driven by the secondary battery (load as viewed from the secondary battery) include external terminals + V0 104 and −V0
105. The FET-A 112 and the FET-B are connected to the external terminal -V0 105 or + V0 104.
113 are connected in series.

[0005] The overcharge detection comparator 119 and the overdischarge detection comparator 118 have a function of comparing the voltage of the secondary battery 101 with the voltage of the reference voltage A116. The output control logic circuit 124 sends signals to the terminals 125A and 125B in accordance with the outputs of the respective comparators, so that the gate voltage of each FET changes according to each state, and charging and discharging of the secondary battery can be turned on and off. Looks like For example, when an overcharge state occurs, the positive input terminal voltage of the overcharge detection comparator 119 becomes the reference voltage A
116, and the output of the comparator is Lo.
Invert from w to High. When this output signal is input to the output control logic circuit 124, the gate voltage of the FET-B 113 of the switch circuit is changed from High to Low.
Changes to As a result, the charging current stops flowing to the secondary battery 101, and charging is stopped.

The overcurrent detection comparator 117 compares the voltage of the external terminal -V0 105 with the voltage of the reference voltage B 114, outputs signals according to the respective states, and inputs the signals to the output control logic circuit 124. In the overcurrent protection state, the output control logic circuit 124 sends a signal to the FET-A 112 so as to stop discharging, and at the same time, sends a signal to the FET-C 126 to stop the resistor 12.
At 7, the external terminal -V0105 is pulled down. This pull-down is necessary to stabilize the external terminal -V0 105 below the reference voltage B114 and return to the normal state when the load 109 is removed from the overcurrent protection state after detecting the overcurrent.

[0007] It is possible to realize a switch instead of this with one FET, but for that purpose, it is necessary to change not only the gate potential of the FET but also the substrate potential. Otherwise, a situation occurs in which the source potential of the FET becomes higher than the drain potential, so that the charge / discharge control as described above cannot be performed. At present, it is generally controlled by two FETs.

[0008]

However, the charge / discharge control circuit configured as described above has the following disadvantages when transitioning to the overcurrent protection state.

A description will be given with reference to FIG. When the resistance value of the load 109 decreases and the overcurrent detection comparator 117 detects an overcurrent state, the FET-A 112 is turned off.
At this time, the external terminal −VO 1 is generated by the drain-source capacitance of the FET-A 112 and the load or the inductive component of the wiring.
05 changes transiently. This causes the overcurrent detection comparator 117 to release the overcurrent state, so that the FE
TA 112 turns ON. This means returning to the overcurrent state, and the overcurrent detection comparator 117 detects the overcurrent state.

By repeating the above, the FET-A 11
2 should be turned off, but it will be in an oscillation state that repeats ON-OFF, so that the FET-A 112 and the FET-
In some cases, the overcurrent state of B113 was not completely stopped and was destroyed.

[0011]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a circuit having a detection circuit for detecting overcurrent and an overcurrent recovery delay circuit when detecting overcurrent in a charge / discharge control circuit. It was configured.

[0012]

In the charge / discharge control circuit configured as described above, the overcurrent state is reliably detected and the FET-A
The ET-B 113 or the secondary battery 101 will be protected.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.
It will be described based on the following.

In the circuit of FIG. 1, an overcurrent release delay circuit 128 is added to FIG. After the overcurrent detection comparator 117 detects an overcurrent, the external terminal −VO 105 transiently fluctuates due to the drain-source capacitance of the FET-A 112 and the inductive component of the load or wiring, and the overcurrent detection comparator 117 Even if the overcurrent release is detected, the FET-A
112 does not turn on. If the fluctuation ends during that time, the overcurrent detection comparator 117 stably protects the overcurrent state to detect the overcurrent.

As described above, the overcurrent state is reliably detected and the FET-
A 112, FET-B 113 or secondary battery 1
Protecting 01 is obvious.

As described above, the circuit of this embodiment does not affect all the environments in which the secondary battery is used, and solves the problems of the conventional circuit.

Further, the above-described load 109 and charger 108
The overcurrent release delay circuit 128 according to the present embodiment is designed so that a voltage is stably generated at the FET-A control output terminal 125-A in response to a transient voltage change caused by attachment / detachment or other various causes. It is also effective to optimize the delay time of.

The switch circuit 103 of this embodiment is a Pch-
Obviously, the same operation as described so far will be performed when the FET is used.

Although the above embodiments have been described by controlling the charging / discharging of one secondary battery, even when a plurality of secondary batteries are connected in series, the voltage of each battery is controlled by a charging / discharging control circuit. At 102, a simple configuration can be obtained by changing the detection so as to be detectable, and the present invention is also effective at that time.

Further, according to the present invention, a release delay is provided when an overcurrent is detected, so that the overcurrent state is reliably detected and the FET-A 112
If the circuit configuration protects the FET-B 113 or the secondary battery 101, the object can be achieved, and the circuit need not be exactly the same as in this embodiment.

In this embodiment, the C-MOS (Comple
mentally Metal Oxide Semiic
Although the charge / discharge control circuit is constituted by an inductor circuit, the charge / discharge control circuit can be constituted by a bipolar transistor, which is easy to realize.

[0022]

As described above, according to the present invention, by simply adding a simple circuit as described above, the overcurrent state can be reliably detected and the FET can be detected.
-A 112, FET-B 113 or secondary battery
Thus, the protection of the product 101 is improved, and the safety of the product is improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing circuit blocks of a rechargeable power supply device of the present invention.

FIG. 2 is an explanatory diagram showing circuit blocks of a conventional rechargeable power supply device.

FIG. 3 is a circuit block diagram showing another example of a conventional rechargeable power supply device.

FIG. 4 is a circuit block diagram showing a specific example of a conventional rechargeable power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 ... Rechargeable battery 102 ... Charge / discharge control circuit 103 ... Switch circuit 104 ... External terminal + V0105 ... External terminal-V0106 ... Terminal-(+) V0 connection line 107A: Signal line A 107B: Signal line B 108: Charger 109: Load 110: Positive electrode of secondary battery 111: Negative electrode of secondary battery 112: FET-A 113 ... FET-B 114 ... Reference voltage B 115 ... Overcurrent detection terminal 116 ... Reference voltage A 117 ... Overcurrent detection comparator 118 ... Overdischarge detection comparator 119 ... Over Charge detection comparator 120: voltage dividing circuit A 121: voltage dividing circuit B 122: hysteresis circuit A 123: hysteresis circuit B 124: output logic Block control circuit 125-A: FET-A control signal output terminal 125-B: FET-B control signal output terminal 126: FET-C 127: Resistor 128: Overcurrent recovery delay circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02H 7/18 H02H 7/18 H02J 7/10 H02J 7/10 BF term (Reference) 5G003 AA01 BA01 DA07 DA13 FA04 GA01 5G004 AA04 AB02 BA04 DA02 DC01 EA01 5G053 AA01 BA01 CA01 EA03 EC03 5H030 AA03 AA04 AA06 AS05 BB01 BB21 FF42 FF43 FF44

Claims (1)

[Claims] 1. A rechargeable power supply device comprising a switch circuit and a secondary battery connected in series to an external power supply terminal, and a charge / discharge control circuit connected in parallel to the secondary battery to control the switch circuit. The charge / discharge control circuit includes at least a voltage dividing circuit, a reference voltage, a comparator, a logic circuit,
The charge / discharge control circuit includes a hysteresis circuit, and the charge / discharge control circuit turns off the switch circuit at the time of overdischarge when the voltage of the secondary battery is lowered and at the time of overcurrent when an excessive current flows through the switch circuit, and loads the load from the secondary battery. And a function of stopping the charging of the secondary battery from the charger by turning off the switch circuit even during overcharge when the voltage of the secondary battery has increased, and A charge / discharge control circuit and a rechargeable power supply device having a detection circuit for detecting overcurrent and an overcurrent recovery delay circuit when the power supply device detects overcurrent.