JPH05176474A - Overcharge control circuit - Google Patents

Abstract

PURPOSE:To provide an overcharge control circuit for rechargeable battery built in an appliance in which adverse effect of ambient temperature or charging voltage is suppressed and overcharge is prevented from sustaining. CONSTITUTION:An appliance incorporates a rechargeable power supply battery 12 which is fed with a charging current from a constant current circuit 13a comprising a -DELTAV detecting control circuit for detecting the battery voltage drop DELTAV at the end of charging operation of the rechargeable battery 12 and terminating the charging operation. The appliance further incorporates a thermister 28 for sequentially converting the temperature of the rechargeable battery 12 into a voltage value thus detecting a battery temperature voltage value, a voltage reference generating circuit 32 for converting a temperature at the time of overcharge of the rechargeable battery 12 into a voltage value thus outputting a voltage reference, and a circuit 31 for comparing the battery temperature voltage value with the voltage reference, wherein a switching circuit 33 interrupts a circuit for feeding the charging current from an external charger when the battery temperature voltage value exceeds the voltage reference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcharge control circuit for a rechargeable battery, and more particularly to an overcharge control circuit for connecting an external charger to an electronic device having a built-in rechargeable battery for charging.

[0002]

2. Description of the Related Art In recent years, as electronic devices such as facsimile machines have become smaller and lighter, a rechargeable battery has been built in in addition to a commercial power source, which is used as an operating power source and is easy to carry and easy to use. Unconstrained, portable electronic devices have been developed. Conventionally, in such electronic devices, a commercial power supply (AC) is installed in the device and a constant DC power supply (D) is used.
A power supply circuit for converting into C) is provided, and the power supply circuit supplies power to the main body circuit and charges the built-in rechargeable battery.

Generally, the power supply circuit uses a component having a larger weight and shape than other circuit components such as a transformer and an electrolytic capacitor. These components need to be large according to the magnitude of the output current of the power supply circuit. For this reason, in the case of the portable electronic device described above, a power supply system has been proposed in which a power supply is supplied from the outside and a rechargeable battery as a portable power supply is built therein.

When charging the rechargeable battery built in this equipment, it is necessary to charge the rechargeable battery while controlling the charging conditions according to the usage condition of the rechargeable battery. In particular, a large current is used for a short time. To charge the battery, it was necessary to provide a control circuit outside. Therefore, as conventional charging control methods, there are a battery voltage detection method, a battery temperature detection method, a -ΔV detection control method, a timer method, and the like.

FIG. 5 is a diagram illustrating a conventional battery voltage detection method, FIG. 6 is a diagram illustrating a conventional battery temperature detection method, (a) is a circuit block diagram, and (b) is a control operation. It is a diagram showing. 7A and 7B are diagrams for explaining a conventional -ΔV detection control method, FIG. 7A is a circuit block diagram, and FIG. 7B is a diagram showing a control operation. First, in the battery voltage detection method, as shown in FIG. 5, when the battery voltage rises to a certain cutoff voltage (Vc) at the end of charging, it is detected and the charging current is controlled. is there. However, this method
There is a problem that the battery voltage at the time of charging easily changes depending on the charging current, the ambient temperature, etc., and a compensation circuit for this is required separately. Moreover, since the cutoff voltage (Vc) must be set lower than the peak value of the charging voltage,
There is a problem that the charging capacity cannot be secured.

Next, in the battery temperature detecting method, as shown in FIG. 6 (a), a commercial power source or the like is used as a direct current power source 1 through a rectifying circuit, and the direct current power source 1 is used to charge a rechargeable battery 2. Is. The rechargeable battery 2 is covered with a battery case 3, and a temperature sensitive element 4 such as a thermistor or a thermostat is added to the side surface of the outer can of the battery to generate heat from the battery due to gas consumption reaction at the cathode at the end of charging. To be detected. The temperature detected by the temperature sensitive element 4 is shown in FIG.
When the cutoff temperature of (b) is reached, the switching circuit 5 is switched to stop the supply of the charging current. This method has a problem that the charging battery is always overcharged for a certain period of time each time it is charged, because the charging current is controlled after entering the overcharge region. The problem of overcharging a rechargeable battery is that the life of the rechargeable battery is shortened and it tends to be defective. If liquid leakage occurs or some of the plurality of rechargeable batteries become defective, the resistance becomes 0Ω. , Even if it is normally charged, it may be overcharged.

Next, the -ΔV detection control method is shown in FIG.
As shown in, when charging the rechargeable battery 2 with the charging current from the constant current power source 6, a drop (ΔV) in battery voltage at the end of charging is detected between the rechargeable battery 2 and the switching circuit −ΔV. A detection control circuit 7 is provided. This-
The ΔV detection control circuit 7 is composed of a comparison circuit 8 and a peak value storage circuit 9, inputs the battery voltage of the rechargeable battery 2 to one terminal of the comparison circuit 8, and stores the peak value of the battery voltage in the peak value. The value is stored in the circuit 9 and input to the other terminal of the comparison circuit 8. While comparing with the comparison circuit 8, from the peak value to −Δ
When the battery voltage drops by V, the switching circuit 5 is activated to stop the charging current supply. This method is a kind of the voltage detection method described above, but does not require compensation for ambient temperature.

Next, in the timer method, charging is performed for a certain time by a timer. Although this method can make the amount of charge almost constant, it is effective when charging from a state where the remaining capacity of the battery is zero, but there is a problem that it may be overcharged when there is a remaining capacity. ..

[0009]

As described above, the various conventional overcharge control circuits have advantages and disadvantages, but are less susceptible to the influence of the charging current and the ambient temperature and may be overcharged. The low-ΔV detection control method is generally used. However, this −ΔV detection control method is
As shown in FIG. 7B, the switching circuit 5 of FIG. 7A operates at the time point when the peak value at the end of charging falls by −ΔV, and the supply of the charging current is temporarily stopped. When the outlet is accidentally unplugged and then plugged in again, the peak voltage storage circuit 9 stores the battery voltage at that time as the peak value, and therefore −ΔV is further detected due to the characteristics of the battery even if the charging current is supplied thereafter. However, there is a problem in that overcharging may continue as in the overcharging area 10 shown by hatching in FIG. 7B.

The present invention has been made in view of the above conventional problems, and when charging a rechargeable battery incorporated in a device, there is little influence by ambient temperature or charging voltage, and overcharging continues. It is an object of the present invention to provide an overcharge control circuit that is less likely to occur.

[0011]

The invention according to claim 1 is
The device has a rechargeable battery for power supply, and a charging current for charging the rechargeable battery is supplied from an external charger having a constant current circuit, and the external charger has a battery at the end of charging generated by the rechargeable battery. In the overcharge control circuit including a −ΔV detection control circuit that detects a voltage drop (ΔV) and terminates charging, the temperature of the rechargeable battery is sequentially converted into a voltage value inside the device. Battery temperature detection means for detecting a temperature voltage value, reference voltage value output means for outputting a reference voltage value obtained by converting a temperature generated when the charging battery is overcharged into a voltage value, and the detected battery temperature voltage value Voltage comparison means for comparing with the reference voltage value, and when the battery temperature voltage value becomes equal to or higher than the reference voltage value by the voltage comparison means, the charging current supply circuit from the external charger is cut off to terminate the charging. Switching Means and are provided.

According to a second aspect of the present invention, in place of the switching means of the first aspect, when the battery temperature voltage value becomes equal to or higher than a reference voltage value by the voltage comparing means, the external charger changes to the rechargeable battery. It is characterized in that a pseudo load resistance connecting means for connecting a pseudo load resistance in parallel to a supply circuit for supplying a charging current is provided. The invention according to claim 3 is
The overcharge control circuit according to claim 1 or 2, wherein a reverse current prevention diode that causes a current to flow only from the external charger to the charging battery in the middle of the supply circuit that supplies the charging current from the external charger to the charging battery in the device. Is provided, and power is supplied from the anode side of the reverse current prevention diode to the battery temperature detection means, the reference voltage value output means, the voltage comparison means, the switching means, the pseudo load connection means, etc. An overcharge control circuit characterized by the above.

[0013]

According to the first aspect of the invention, the external charger has -ΔV.
The charge is terminated by the detection control circuit, and the battery temperature / voltage value that converts the temperature of the rechargeable battery into a voltage value inside the device and the reference voltage value that converts the overcharge temperature of the rechargeable battery into a voltage value are compared. When the battery temperature voltage value exceeds the reference voltage value and the charging battery reaches the overcharging temperature, the charging current supply circuit supplied from the external charger to the charging battery is opened to terminate the charging. Therefore, conventionally, if the outlet is accidentally unplugged and then re-plugged after the charging is completed by the −ΔV detection control circuit, the charging is restarted and the overcharged state continues. However, the overcharge control circuit in the device of the present invention monitors the charging battery temperature even after the charging is accidentally started again, and terminates the charging when the overcharging temperature is reached.
Continuous overcharging is prevented.

According to the second aspect of the present invention, the pseudo load resistor is connected in parallel to the supply circuit that supplies the charging current from the external charger to the charging battery when the charging battery temperature is monitored and the overcharge state is detected. To be done. As a result, the charging current supplied from the external charger to the rechargeable battery will also flow to the pseudo load resistance side to increase the amount of current, but the amount of current is kept constant by the constant current circuit inside the external charger. Attempts to generate a voltage drop. Therefore, the −ΔV detection control circuit built in the external charger detects the voltage drop (ΔV) and terminates the charging even if the continuous overcharge state occurs, so that the charging battery is overcharged. Is prevented.

According to the third aspect of the present invention, a reverse current prevention diode is provided in the middle of the supply circuit for supplying the charging current from the external charger to the charging battery in the device, and the reverse current preventing diode is used to flow the current only from the external charger to the charging battery. Power is supplied from the anode side of the reverse current prevention diode to the overcharge control circuit in the device. Therefore, when charging the rechargeable battery from the external charger, power is supplied to the overcharge control circuit to operate, but the current output from the rechargeable battery after charging is not supplied to the overcharge control circuit by the reverse current prevention diode. Therefore, the overcharge control circuit does not operate and wasteful power consumption is prevented.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. First, the configuration will be described. 1A and 1B are diagrams showing the configuration of an embodiment of a facsimile apparatus incorporating an overcharge control circuit according to the present invention. FIG. 1A is an external perspective view and FIG. 1B is a circuit block diagram. FIG. 2 is a diagram for explaining an overcharge control circuit according to the invention of claim 1, (a) is a circuit block diagram,
(B) is a diagram showing a control operation. FIG. 3 is a diagram for explaining an overcharge control circuit according to the invention of claim 2,
(A) is a circuit block diagram and (b) is a diagram showing a control operation. FIG. 4 is a circuit block diagram of an overcharge control circuit according to a third aspect of the invention.

As shown in FIG. 1A, the facsimile apparatus 11 according to the present embodiment is provided with a rechargeable battery 12, such as a battery pack, which is built in the facsimile apparatus 11 and an external charger 1.
3 is used for charging. The external charger 13 and the rechargeable battery 12 of the facsimile device 11 are detachably connected to each other via a charging cable 14 with a connector 15. The external charger 13 is for inserting a commercial power source of AC 100 V into an outlet and outputting a constant DC current. Here, a transformer, a rectifier circuit,
A constant current circuit and a -ΔV detection control circuit are provided.

Next, FIG. 1 (b) is a circuit block diagram of the facsimile apparatus 11 of FIG. 1 (a).
In the figure, reference numeral 16 is a scanner unit for reading an image of a transmission document of a facsimile and converting it into an electric image signal, 17
Is an encoding / decoding unit that encodes image information to be transmitted and decodes the received image information, and 18 is a plotter that records the image information on a thermal recording paper or the like. A large number of heat generating elements are arranged in the head. Reference numeral 19 is a network control unit for performing a predetermined call-out operation by connection with the line L, transmission of a selection signal which is a destination telephone number, detection of an incoming call, and 20. , A communication control unit 21 for controlling the network control unit 19 and the modem 20 to execute facsimile communication, and a display unit 22 for displaying the operating state of the facsimile apparatus 11 and allowing the operator to perform various operations. An operation display section for instructing 23 is provided with a microcomputer and various electronic circuits, a system control section for controlling each section in the facsimile apparatus, 24 is supplied with power from the rechargeable battery 12, and a constant voltage is applied to each section. Stabilized power supply for output, 25 is rechargeable battery 1
2, a charging control unit that controls the charging operation while preventing overcharging, 26 is a data bus that connects the above units to supply data and power, and 27 is an overcharge control circuit according to the present invention.

Therefore, a specific structure of the overcharge control circuit 27 in the facsimile apparatus 11 will be described with reference to FIGS. First, as shown in FIG.
The constant current circuit 13a is built in the external charger 13 described above, and further, the constant current circuit 13a has the -ΔV detection control circuit shown in the conventional example of FIG. 7 built therein. The constant current circuit 13a is connected to the overcharge control circuit 27 via the connector 15 and charges the rechargeable battery 12.

Therefore, the overcharge control circuit 2 according to claim 1
7, a thermistor 28, which is a temperature sensing element for temperature detection, is provided adjacent to the rechargeable battery 12, one end of the thermistor 28 is grounded, and a constant voltage power supply 29 has a resistor (R) at the other end.
It is connected via 30 and is input to one terminal of the comparison circuit 31. A reference voltage generation circuit 32 that generates a reference voltage value obtained by converting the temperature generated when the rechargeable battery 12 is overcharged into a voltage value is provided at the other terminal of the comparison circuit 31.
Are connected. The output of the comparison circuit 31 is input to the switching circuit 33 provided in the middle of the supply circuit that supplies the charging current from the constant current circuit 13a to the charging battery 12, and controls the switching operation.

Next, the operation will be described. As shown in FIG. 2B, when the battery voltage exceeds the peak value at the end of charging and the voltage drops by ΔV, the −ΔV detection control circuit in the constant current circuit 13a operates to stop the supply of the charging current. .. However, when the external charger is unplugged and then plugged in again, the charging operation is restarted and the battery voltage at that time is stored as a peak value.
Further, the battery voltage does not drop by ΔV, and continuous overcharging is performed (the overcharging region 3 indicated by hatching in the figure).
4).

However, the overcharge control circuit 27 of this embodiment is
2A, the temperature of the rechargeable battery 12 in the device is sequentially detected by the thermistor 28 and converted into a voltage value, as shown in FIG. The resistance value of the thermistor 28 increases as the temperature rises, and since the thermistor 28 is connected to the constant voltage power supply 29 via the resistor 30, the resistance value of the thermistor 28 changes depending on the temperature of the charging battery 12, The voltage across the resistor (R) changes, and the voltage input to the comparison circuit 31 changes. The comparison circuit 31 compares the battery temperature voltage value with the reference voltage value of the reference voltage generation circuit 32. If the charging battery 12 exceeds the overcharge temperature (cutoff temperature), switching is performed by the output of the comparison circuit 31. The circuit 31 is opened to stop supplying the charging current. Therefore, as shown in FIG. 2B, even if the charging is mistakenly restarted by the −ΔV detection control circuit of the constant current circuit 13a, the overcharge control circuit 27 in the device sequentially changes the temperature of the rechargeable battery 12. Since the charging current is monitored and cut off, overcharging is not performed continuously, and deterioration of the characteristics of the rechargeable battery 12 due to overcharging can be prevented.

Next, the overcharge control circuit 27 according to claim 2
As shown in FIG. 3 (a), the basic configuration is almost the same as that of the above claim 1, except that the constant current circuit 13a is replaced by the rechargeable battery 12 instead of the switching circuit 33. One end of the pseudo load resistance (R ₁ ) 35 is connected to the electric path for supplying the charging current to the other end, the other end of the pseudo load resistance 35 is connected to the collector of the transistor 36, and the output of the comparison circuit 31 is the output of the transistor 36. It is connected to the base and the emitter of the transistor 36 is grounded.

Next, the operation will be described. As mentioned above,
The thermistor 28 is resistant to the temperature change of the rechargeable battery 12.
(R _O) The voltage between 30 changes and compared with the reference voltage value
If the battery temperature exceeds the cutoff temperature, the comparison circuit
The transistor 36 is turned on by the output of 31, and the pseudo negative
Load resistance (R₁) 35 to the current (i₁)
It As a result, the current supplied from the constant current circuit 13a
Is i₁Current (i)
₀) And (i₁+ I₀).

However, in this embodiment, since the external charger 13 is composed of the constant current circuit 13a, a voltage drop is caused in order to keep the current amount constant. Figure 3
As shown in (b), the battery temperature drops once when the charging current is not supplied at the first detection of −ΔV, but the temperature starts to rise when the outlet is reinserted and charging is started. When the transistor 36 is turned on when the cut-off temperature is reached and a current flows through the pseudo load resistor 35, the battery voltage drops due to the above reason, -ΔV detection is performed, and -ΔV of the external charger 13 is detected. The detection control circuit terminates charging.

That is, in the embodiment of claim 2, when the charge battery temperature exceeds the cut-off temperature, a pseudo -ΔV is generated, and the battery is controlled as if it were at the end of charge.
Charging is terminated on the external charger side. Next, as shown in FIG. 4, the overcharge control circuit 27 according to claim 3 is the constant current circuit between the constant current circuit 13a and the rechargeable battery 12 in the embodiment according to claim 1 or 2. 13a
Is provided with a reverse current prevention diode 37 that allows a current to flow only in the direction from the charging battery 12 to the rechargeable battery 12. On the anode side of the reverse current prevention diode 37, a thermistor 28, a resistor 30, and a constant voltage power supply 29 that configure the charging control unit 25. , Reference voltage generation circuit 32, comparison circuit 31, switching circuit 33
Alternatively, a stabilizing power supply 38 for supplying electric power to the pseudo load resistor 35 and the transistor 36 is connected.
The stabilizing power supply 38 also supplies power to the stabilizing power supply 38 while the charging current is being supplied from the constant current circuit 13a to the rechargeable battery 12, and operates each part of the charging control unit 25. However, after charging the rechargeable battery 12, the rechargeable battery 1
Since the current supplied from 2 does not flow into the anode side by the reverse current prevention diode 37, power is not supplied to each part of the charging control unit 25 and the operation is stopped.

As described above, in the case of the third embodiment, the charging control unit 25 is operated only at the time of supplying the charging current at the time of charging, so that the power consumption of the rechargeable battery 12 is prevented from being wasted. it can. As described above, when the portable facsimile apparatus is configured using the overcharge control circuit of this embodiment, the built-in rechargeable battery is less likely to be overcharged, and the power of the rechargeable battery is reduced. It can be consumed efficiently.

[0028]

According to the first aspect of the present invention, the thermistor is disposed adjacent to the rechargeable battery built in the equipment, and when the temperature of the rechargeable battery exceeds the overcharge temperature, the external charger is used. Prevents overcharging by opening the charging current supply circuit by, so even if the -ΔV detection control circuit provided in the external charger mistakenly starts recharging after the end of charging, the overcharged state is prevented from continuing. can do.

According to the second aspect of the present invention, the thermistor is arranged adjacent to the rechargeable battery built in the equipment, and when the temperature of the rechargeable battery exceeds the overcharge temperature, the charge is performed from the external charger. Since the pseudo load resistance is connected in parallel to the supply circuit that supplies the charging current to the battery, the impedance inside the device is reduced and the charging current is controlled to increase, and the constant load in the external charger is controlled. The voltage is reduced by the current circuit, and the −ΔV detection control circuit in the external charger is activated to end the charging. For this reason, the -ΔV detection control circuit that once detected the end-of-charge state of the rechargeable battery and finished charging,
Even if the charging is accidentally started again, continuous overcharging can be prevented.

According to a third aspect of the present invention, in the overcharge control circuit according to the first or second aspect, a reverse current preventing diode is provided between the external charger and the charging battery in the device, and the reverse current preventing diode is provided from the anode side. Since power is supplied to the charge control circuit, it is possible to prevent wasteful power consumption.

[Brief description of drawings]

1A and 1B are diagrams showing a configuration of an embodiment of a facsimile apparatus incorporating an overcharge control circuit of the present invention, in which FIG. 1A is an external perspective view and FIG. 1B is a circuit block diagram.

2A and 2B are diagrams illustrating an overcharge control circuit according to the first aspect of the invention, FIG. 2A is a circuit block diagram, and FIG. 2B is a diagram showing a control operation.

3A and 3B are diagrams illustrating an overcharge control circuit according to a second aspect of the present invention, in which FIG. 3A is a circuit block diagram and FIG. 3B is a diagram showing a control operation.

FIG. 4 is a circuit block diagram of an overcharge control circuit according to a third aspect of the invention.

FIG. 5 is a diagram illustrating a conventional battery voltage detection method.

FIG. 6 is a diagram illustrating a conventional battery temperature detection method,
(A) is a circuit block diagram and (b) is a diagram showing a control operation.

FIG. 7 is a diagram illustrating a conventional −ΔV detection control method,
(A) is a circuit block diagram and (b) is a diagram showing a control operation.

[Explanation of symbols]

 11 Facsimile Device 12 Rechargeable Battery (Battery Pack) 13 External Charger 13a Constant Current Circuit 25 Charge Control Section 27 Overcharge Control Circuit 28 Temperature Sensing Element (Battery Temperature Detection Means) 29 Constant Voltage Power Supply 30 Resistance 31 Comparison Circuit (Voltage Comparison Means) ) 32 reference voltage generation circuit (reference voltage value output means) 33 switching circuit (switching means) 35 pseudo load resistance 36 transistor (pseudo load resistance connection means) 37 reverse current prevention diode 38 stabilized power supply

Claims (3)

[Claims] 1. A rechargeable battery for power supply is provided in a device, a charging current for charging the rechargeable battery is supplied from an external charger having a constant current circuit, and the rechargeable battery is provided in the external charger. In the overcharge control circuit provided with a −ΔV detection control circuit, which detects a drop (ΔV) in the battery voltage at the end of charging and ends the charging, the temperature of the charging battery is sequentially changed to a voltage value inside the device. A battery temperature detecting means for converting the battery temperature voltage value into a voltage value, and a reference voltage value outputting means for outputting a reference voltage value obtained by converting the temperature generated at the time of overcharging of the rechargeable battery into a voltage value; Voltage comparing means for comparing the battery temperature voltage value with the reference voltage value, and turning off the charging current supply circuit from the external charger when the battery temperature voltage value exceeds the reference voltage value by the voltage comparing means. To end charging Overcharge control circuit, wherein the switching means, further comprising a that. 2. The overcharge control circuit according to claim 1, wherein, in place of the switching means, when the battery temperature voltage value becomes equal to or higher than a reference voltage value by the voltage comparison means, the external charger charges the battery. An overcharge control circuit comprising pseudo load resistance connecting means for connecting a pseudo load resistance in parallel to a supply circuit for supplying a charging current to the load circuit. 3. The overcharge control circuit according to claim 1, wherein a current is supplied only from the external charger to the charging battery in the middle of a supply circuit that supplies the charging current from the external charger to the charging battery in the device. A reverse current prevention diode for flowing is provided, and the battery temperature detection means, the reference voltage value output means, the voltage comparison means, the switching means or the pseudo load connection means, etc. for controlling the charging of the equipment from the anode side of the reverse current prevention diode An overcharge control circuit characterized in that power is supplied thereto.