JP2002320335A - Charge/discharge controlling circuit and charging type power source unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charge/discharge controlling circuit which surely detects excessive charge, and a charging type power source device using the circuit. SOLUTION: In the charge/discharge controlling circuit, a circuit which has a delay time in the case that the state of excessive charge is released is constituted in an excessive charge detecting circuit, thereby surely detecting the sate of excessive charge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] 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 Patent Application Laid-Open No. 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, the discharge can be stopped (overcurrent control) when an excessive current flows. 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-chFETs. The voltage of the secondary battery 101 is detected by the charge / discharge control circuit 102. Charge / discharge control circuit 102
Is composed of an overcharge detection comparator 119, an overdischarge detection comparator 118, an overcurrent detection comparator 117, a reference voltage circuit A116, a reference voltage circuit B114, a voltage division circuit A120, a voltage division circuit B121, an output control logic circuit 124, and the like. I have. The charge / discharge control circuit 102 is connected to the switch circuit 103 via signal lines 107A and 107B, and sends an ON / OFF signal of the switch circuit. Charger 1 for charging secondary battery 101
08 or a device that can be driven by a secondary battery (a load as viewed from the secondary battery) is connected between the external terminals + V0 104 and −V0 105. External terminal -V0 105 and secondary battery 1
01, the FET-A 112 and the FET-B 113
Are connected in series.

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 equal to the reference voltage A11.
6, the output of the comparator is inverted from Low to High. When this output signal is input to the output control logic circuit 124, the FE of the switch circuit is
The gate voltage of the TB 113 changes from High to Low. As a result, the charging current stops flowing to the secondary battery 101, and charging is stopped. Hysteresis circuit A 12
2. By the hysteresis circuit B123, when transitioning to the overcharge state and the overdischarge state, the charge and discharge of the secondary battery can be stably turned on and off with respect to the voltage fluctuation due to the internal impedance of the secondary battery. Become.

The overcurrent detection comparator 117 compares the voltage of the external terminal -V0 105 with the reference voltage B114, outputs a signal according to each state, and inputs the signal 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 output a signal to the resistor A 127.
Pulls down the external terminal -V0 105. 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. The resistor B 129 is connected to the overcurrent detection terminal 115 to protect the charge / discharge control circuit 102 from destruction by static electricity.

In the case of an overcurrent state in the overcharged state, the hysteresis is returned to protect the FET-B 113 from heat generation, and the FET-B is turned on even when the FET-B is over the overcharge release voltage.

[0008] These can also realize a switch instead of a single FET.
It is necessary to change not only the gate potential of T 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. Currently, two FETs
It is generally controlled by:

[0009]

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

A description will be given based on FIG. Rechargeable battery 101
When the overcharge detection comparator 119 detects an overcharged state, the FET-B 113 turns off. At this time, a current flows from the gate-source capacitance of the FET-B 113 to the resistor B 129, and the overcurrent detection comparator 117 detects the overcurrent state, thereby returning the hysteresis of the overcharge detection voltage. Will be.

As described above, the voltage fluctuation due to the internal impedance of the secondary battery 101 is stable.
Could not be turned off, and the secondary battery 101 could be destroyed.

[0012]

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

[0013]

In the charge / discharge control circuit configured as described above, the overcharge state is reliably detected to protect the secondary battery 101.

[0014]

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 overcharge release delay circuit 128 is added to FIG. After the overcharge detection comparator 119 detects overcharge, a current flows from the gate-source capacitance of the FET-B 113 to the resistor B 129, whereby the overcurrent detection comparator 117 detects an overcurrent state and detects overcharge. Even if the hysteresis of the voltage is returned, the overcharge release delay circuit 128 does not turn on the FET-B 113 during the delay time. If the fluctuation ends during that time, the hysteresis of the overcharge detection comparator 119 functions, so that the overcharge state is stably protected.

As described above, it is clear that the overcharged state is reliably detected and the secondary battery 101 is protected.

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

Further, the above-described load 109 and charger 1
For stable transient voltage fluctuations caused by attachment / detachment of 08 and other various causes
It is effective to optimize the delay time of the overcurrent release delay circuit 128 of this embodiment so that a voltage is generated at the B control signal output terminal 125-B.

The switch circuit 103 of this embodiment is a Pch
It is clear that the same operation as described so far is performed when the device is constituted by the FET.

Although the embodiments described so far have been described by controlling the charging and 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 that it can be detected, 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 insulator circuit, the charge / discharge control circuit can be constituted by a bipolar transistor, and is easily realized.

[0023]

According to the present invention, as described above, by simply adding a simple circuit, an overcharged state can be reliably detected and the secondary battery 101 can be protected, thereby improving the safety of the product. There is.

[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 Lock control circuit 125-A: FET-A control signal output terminal 125-B: FET-B control signal output terminal 126: FET-C 127: Resistance A 128: Overcharge release Delay circuit 129: resistor B

Claims (2)

[Claims] 1. A charge / discharge control circuit having a voltage dividing circuit, a reference voltage, a comparator, a logic circuit, and a hysteresis circuit for controlling charge / discharge of a secondary battery, wherein the charge / discharge control circuit is configured to control a voltage of the secondary battery. In addition to the function of turning off the switch circuit to stop discharging from the secondary battery to the load at the time of overdischarge that has decreased and overcurrent when excessive current has flowed through the switch circuit, the voltage of the secondary battery has increased. It has a function of turning off the switch circuit even during overcharge and stopping charging from the charger to the secondary battery, and a detection circuit for detecting overcharge when the rechargeable power supply device detects overcharge. Charge / discharge control circuit having an overcharge release delay circuit 2. A rechargeable battery comprising a switch circuit and a secondary battery connected in series to an external power supply terminal, a voltage dividing circuit for controlling the switch circuit, a reference voltage, a comparator, a logic circuit, and a hysteresis circuit. A rechargeable power supply device comprising a connected charge / discharge control circuit, wherein the charge / discharge control circuit switches the switch circuit at the time of overdischarge when the voltage of the secondary battery becomes low and at the time of overcurrent when an excessive current flows through the switch circuit. It has a function to turn off and stop discharging from the secondary battery to the load, and also stops charging from the charger to the secondary battery by turning off the switch circuit even during overcharge when the voltage of the secondary battery becomes high. A rechargeable power supply device having a function and having a detection circuit for detecting overcharge and an overcharge release delay circuit when the rechargeable power supply device detects overcharge. .