JPH0741479U - Battery level monitoring circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a battery remaining amount monitoring circuit that can accurately measure the remaining amount of batteries having different voltages without being affected by the outside temperature. [Structure] In the circuit, C1> C2, R1 = R3, R2
= R41 + R42, the variable voltage g is set to be slightly higher than the reference voltage f by the variable resistor R5. When the reference voltage f becomes larger than the fluctuation voltage g, the comparator 1 is configured to output the abnormality detection signal h. First, when the capacity of the battery 2 is sufficient and the internal impedance r is small, the fluctuating voltage g does not decrease much even if the load 3 suddenly becomes heavy, and does not become smaller than the reference voltage f. But battery 2
If the internal impedance r becomes large,
The battery voltage e drops due to the load 3 being overloaded and the fluctuation voltage g
Also drops, and is momentarily smaller than the reference voltage f at which the voltage drop is delayed due to C1> C2. Therefore, the alarm is output from the comparator 1.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a circuit for monitoring the capacity of a battery as a power source of electronic equipment.

[0002]

[Prior art]

 The battery remaining monitoring circuit that has been widely used in the past compares the current battery voltage or its divided voltage with a reference voltage maintained at a constant potential by a constant-voltage diode, etc. It is configured so that it sometimes outputs a detection signal to notify that the remaining battery capacity is low. This utilizes the property that the battery voltage decreases as the battery capacity decreases.

[0003]

[Problems to be solved by the device]

 However, in the circuit as described above, not only when the battery capacity becomes low, but for example, even when the battery capacity is sufficient, the outside temperature happens to be low and the chemical reaction inside the battery becomes slower. Even if the voltage drops, the detection signal could be erroneously output. In addition, since the supply voltage of electronic devices differs depending on the type and number of batteries used in them, it was necessary to adjust and set the reference voltage for each supply voltage.

The present invention has been proposed in view of the above problems, and is used regardless of the difference in the battery voltage depending on the type and number of batteries and the voltage fluctuation due to the influence of the outside temperature and the like. It is an object of the present invention to provide a battery remaining amount monitoring circuit capable of accurately detecting that the battery capacity is low.

[0005]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, in the battery residual amount monitoring circuit according to claim 1, first delay detecting means for delaying a variation of the battery voltage to be monitored in time and outputting it as a delay reference signal, and the battery voltage. Of the delay reference signal and the delay variation signal are compared with each other by comparing the delay reference signal and the delay variation signal with the second delay detecting means that outputs the variation as a delay variation signal after a delay of a shorter time than the first delay detecting means. A means for providing a comparison means for outputting an abnormality detection signal when a deviation occurs is provided.

In the present invention, the deviation is a numerical value relatively indicating how much it deviates from the value of the steady state potential difference between the delay reference signal and the delay fluctuation signal. The delay time of the second delay detecting means includes 0.

Further, in the battery remaining amount monitoring circuit according to claim 2, first average detecting means for averaging fluctuations of the battery voltage to be monitored by a predetermined time constant and outputting the average reference signal, the battery voltage Of the average fluctuation signal is averaged with a time constant smaller than that of the first average detection means and is output as an average fluctuation signal, and the average reference signal and the average fluctuation signal are compared, and a predetermined value or more is compared. And a comparison means for outputting an abnormality detection signal when the deviation occurs.

In the present invention, the deviation is a numerical value relatively indicating how much it deviates from the value of the steady state potential difference between the average reference signal and the average fluctuation signal. The time constant of the second average detecting means includes 0. Batteries include not only primary batteries such as manganese dry batteries and silver batteries but also secondary batteries such as lead storage batteries and nickel-cadmium batteries.

[0009]

[Action]

 According to the battery remaining amount monitoring circuit of claim 1, the delay time of the delay fluctuation signal is set shorter than the delay time of the delay reference signal. Here, when the battery voltage fluctuates, the above two signals also fluctuate. However, there is a delay time difference between the two signals, and the delay fluctuation signal always fluctuates faster than the delay reference signal. For example, when the battery voltage drops, the delay fluctuation signal drops faster than the delay reference signal. . Therefore, a deviation occurs in the potential difference between the two signals.

In a battery in which the electric capacity is decreased and the internal impedance is increased, when the output current suddenly changes, the battery voltage changes abruptly by the product of the increase in the output current and the internal impedance. A large deviation occurs in the potential difference between the two signals. When the deviation exceeds a predetermined value, the comparing means outputs an abnormality detection signal.

According to the battery level monitoring circuit of the second aspect, the time constant of the average fluctuation signal is set smaller than the time constant of the average reference signal. Here, when the battery voltage fluctuates, the above two signals also fluctuate. However, since the two signals have a time constant difference and the average fluctuation signal always fluctuates faster than the average reference signal, for example, when the battery voltage drops, the average fluctuation signal drops faster than the average reference signal. . Therefore, a deviation occurs in the potential difference between the two signals.

In a battery in which the electric capacity is decreased and the internal impedance is increased, when the output current suddenly fluctuates, the average fluctuation signal greatly fluctuates by the product of the increase in the output current and the internal impedance. The deviation becomes larger as it goes. When the deviation exceeds a predetermined value, the comparing means outputs an abnormality detection signal.

[0013]

【Example】

 The battery remaining amount monitoring circuit of the present invention utilizes the property that the internal impedance increases as the battery capacity decreases. Hereinafter, the present invention will be described in detail with reference to the drawings showing an embodiment.

First Embodiment FIG. 1 is a block diagram of a first embodiment of a battery remaining amount monitoring circuit according to the present invention, and FIG. 2 is a time chart of its operation. In this embodiment, the delay time of the second delay detecting means is 0. In FIG. 1, a is a battery voltage, b is a delay reference signal, c is a delay variation signal, and d is an abnormality detection signal. 1a is an OP amplifier that outputs a voltage corresponding to the difference between the delay reference signal b and the delay fluctuation signal c, and 1b is the absolute value of the difference between the inputs of the OP amplifier 1a that is a predetermined potential difference V. _m It is a discrimination circuit that outputs the abnormality detection signal d when the above is reached. 2 is a battery having an electromotive force of E 1 and an internal impedance of r 2. 3 is a fluctuating load, and 4 is a switch for the load 3. Reference numeral 5 is a BBD (Bucket Brigade Device) that delays the fluctuation of the electric signal with time. Reference numeral 6a denotes a buffer having a high input impedance provided to reduce the influence on the battery 2 and 6b reduces the influence on the BBD 5. The output voltage (delayed reference signal b) of the buffer 6b is proportional to the battery voltage a. Reference numeral 7 is a voltage dividing circuit composed of resistors for adjusting the level to the voltage of the delay reference signal b, which is composed of high resistance so as not to load the battery 2. Predetermined potential difference V_mCan be set by the discrimination circuit 1b. The current consumption of the battery level monitoring circuit is sufficiently smaller than the current consumption of the load 3.

Here, the BBD 5 and the buffers 6a and 6b serve as the first delay detecting means, the OP amplifier 1a and the discriminating circuit 1b serve as the comparing means, and the voltage dividing circuit 7 serves as the second delay detecting means. Corresponds to a predetermined value. Further, in the steady state of this embodiment, the potential difference between the delay reference signal b and the delay variation signal c is set to 0, and the magnitude of the potential difference between the two signals corresponds to the deviation.

The operation of the battery remaining amount monitoring circuit configured as described above will be described below with reference to FIG. 2 together with FIG. The battery level monitoring circuit of the present invention is always energized. The battery voltage a is obtained by subtracting the voltage drop caused by the consumption current of the battery remaining amount monitoring circuit and the internal resistance r from the electromotive force voltage E.

As shown in FIGS. 2A and 2B, the delay variation signal c is set to the voltage V0 at the same level as the delay reference signal b by the voltage dividing circuit 7 until the timing T1. At this time, the potential difference was 0, and no deviation occurred.

First, the operation when the battery 2 has a sufficient capacity and the internal impedance r is small will be described with reference to FIG. When the switch 4 is turned on at timing T1, a current flows through the load 3. Even if the load suddenly becomes heavy and the output current of the battery 2 increases, the internal impedance r is small, and therefore the battery voltage a only drops a little. At this time, since the delay fluctuation signal c has a delay time of 0, the voltage simultaneously drops and becomes the voltage V1.

On the other hand, the delayed reference signal b is delayed by a predetermined delay time from the timing T1 by the action of the BBD5, and the voltage drops at the timing T2. Therefore, from the timing T1 to the timing T2, the delay reference signal b becomes higher than the delay variation signal c by the potential difference (V0-V1), and a deviation occurs. At that time, a voltage corresponding to the potential difference (V 0 −V 1) is output from the OP amplifier 1 a and input to the discrimination circuit 1 b. However, since the potential difference (V 0 −V 1) is less than the predetermined potential difference V _m , the abnormality detection signal d Is not output.

Next, the operation when the capacity of the battery 2 decreases and the internal impedance r increases will be described with reference to FIG. When the switch 4 is turned on at timing T1, a current flows through the load 3. Then, the battery voltage a of the battery 2 having the increased internal impedance r is greatly reduced by the voltage drop due to the consumption current of the load 3. At the same time, the delay variation signal c immediately drops from the voltage V0 to the voltage V2.

On the other hand, since the delay reference signal b is delayed by a predetermined delay time and drops in voltage at the timing T2, the delay reference signal b is equal to the potential difference (V0-V2) from the delay fluctuation signal c from the timing T1 to the timing T2. It becomes higher and deviation occurs. At that time, a voltage corresponding to the potential difference (V0-V2) is output from the OP amplifier 1a and is input to the determination circuit 1b. At this time, the potential difference (V0 -V2) Since a higher predetermined potential difference V _m, is output abnormality detection signal d of FIG. 2 (C), the knowledge that the capacity of the battery 2 becomes small Selle.

In the battery remaining amount monitoring circuit of the present embodiment, when the switch 4 is turned off, the current consumption decreases and the battery voltage a rises sharply, the delay fluctuation signal c is greater than the delay reference signal b, contrary to the above example. Get higher Even when the absolute value of the potential difference exceeds the predetermined potential difference V _m , the discrimination circuit 1b operates and outputs the abnormality detection signal d.

In the present embodiment, the BBD element is used as the first delay detecting means to delay the change in the battery voltage with time, but a ring buffer may be used for the control processing by the CPU. The sample and hold circuit may be used to temporarily hold the battery voltage before the change. Further, in the present embodiment, the battery remaining amount monitoring circuit is always in the ON state, but it suffices that it be operated before the load 3 is energized, and it is not necessary to always energize it.

Further, a window comparator may be used instead of the OP amplifier 1a and the discrimination circuit 1b, or the comparator is used after adjusting the voltage dividing circuit 7 to give a bias voltage to the delay variation signal c. Good.

(Embodiment 2) FIG. 3 is a circuit diagram of Embodiment 2 of a battery remaining amount monitoring circuit according to the present invention, and FIG. 4 is a time chart thereof. In FIG. 3, e is a battery voltage, f is a reference voltage generated across the resistor R2, g is a variable voltage generated across the resistor (R41 + R42) and the variable resistor R5, and h is an abnormality detection signal.

The battery 2 and the load 3 are the same as in the first embodiment. Reference numeral 1 is a comparator that outputs an abnormality detection signal h when the reference voltage f becomes higher than the fluctuation voltage g. Reference numeral 4a is a switch for turning on / off the entire power source. Further, A is a reference voltage detecting means composed of resistors R1 and R2 and a capacitor C1 for detecting a reference voltage f. B is a fluctuating voltage detecting means composed of resistors R3, R41, R42, a variable resistor R5, and a capacitor C2 for detecting a fluctuating voltage g. The variable resistor R5 indicates a predetermined potential difference V _n in a steady state with the reference signal f. Adjust. C is a hold circuit that holds the abnormality detection signal h output from the comparator 1 in an output state, and D is a display circuit that receives an output of the abnormality detection signal h 1 from the comparator 1 and displays an alarm of the battery capacity with an LED.

Here, the reference voltage f is the average reference signal, the fluctuation voltage g is the average fluctuation signal, the reference voltage detection means A is the first average detection means, and the fluctuation voltage detection means B is the second average detection means. The comparator 1 corresponds to the comparison means. Further, in the steady state of the present embodiment, the potential difference V _n is set in advance for the reference voltage f and the variation voltage g, and the variation of the potential difference from the predetermined potential difference V _n corresponds to the deviation.

The circuit constants of the reference voltage detecting means A and the fluctuating voltage detecting means B of the battery remaining amount monitoring circuit of this embodiment depend on the ratio between the maximum value and the minimum value of the consumption current of the load 3 and other conditions. However, the basic conditions are as follows. R1 = R3, R2 = R41 + R42 (It should be noted that R1: R2 = R3: (R41 + R42).) (Each resistor is made large to some extent so as not to load the battery 2.) Here, R41 >> R42 R5> 0 (variable resistor for adjusting the predetermined potential difference) C1> C2 Although the capacitor C2 can be operated without the capacitor C2, the operation of the battery remaining amount monitoring circuit becomes sensitive and malfunction may increase.

The operation of the battery remaining amount monitoring circuit configured as described above will be described below with reference to FIG. 3 and FIG. 4 showing the fluctuation voltage g and the reference voltage f. After the circuit constants of the battery level monitoring circuit of this embodiment are set, the potential difference V _n between the fluctuation voltage g and the reference voltage f in the steady state is adjusted by the variable resistor R5.

First, when the switch 4a is turned on at the timing T3, a current flows through the load 3 and the battery remaining amount monitoring circuit, and the battery voltage e appears. In the reference voltage detecting means A, the battery voltage e is divided by the resistors R1 and R2 to show the reference voltage f, which is input to the comparator 1 at the same time when the capacitor C1 is charged. Similarly, in the fluctuating voltage detecting means B, the fluctuating voltage g appears across the resistors (R41 + R42) and the variable resistor R5, and the capacitor C2 is charged, and at the same time, is input to the other side of the comparator 1. The manner in which the two voltages, the reference voltage f and the fluctuating voltage g, rise is as shown in FIGS. 4 (A) and 4 (B). Since the capacitance of the capacitor C2 is smaller than that of the capacitor C1, the fluctuation voltage g rises more rapidly than the reference voltage f.

From timing T3 to timing T4, the fluctuation voltage g is always higher than the reference voltage f, so the comparator 1 does not output the abnormality detection signal h. Further, the magnitude of the fluctuating voltage g that has reached the steady state is the voltage V3. The voltage of the difference between the reference voltage f and the fluctuating voltage g in the steady state is the predetermined potential difference V _n , and no deviation has occurred at present.

First, the operation when the battery 2 has a sufficient capacity and the internal impedance r is low will be described with reference to FIG. At timing T4, when the load 3 suddenly becomes heavy, the output current of the battery 2 increases, so the battery voltage e drops slightly. Therefore, the fluctuating voltage g also drops to the voltage V4, and a deviation occurs depending on the degree of the drop. However, since the internal impedance r is small, the voltage drop of the fluctuating voltage g is small, and even when the fluctuating voltage g drops to the voltage V4 at the timing T5, it does not become smaller than the reference voltage f. Therefore, the abnormality detection signal h is not output from the comparator 1 and the display circuit D does not operate.

Next, the operation when the capacity of the battery 2 is reduced and the internal impedance r is increased will be described with reference to FIG. 4 (B). At the timing T4, when the load suddenly becomes heavy and the output current of the battery 2 increases, the battery voltage e decreases greatly because the internal impedance r increases this time, and the reference voltage f and the fluctuation voltage g also increase. A big descent. However, when C1> C2, the degree of the fall is faster for the fluctuating voltage g, and the reference voltage f is delayed by the discharge of the capacitor C2. Therefore, at the timing T5, the fluctuating voltage g becomes smaller than the reference voltage f, the abnormality detection signal h is output as shown in FIG. 4C, and the display circuit D operates. The deviation in this state is _{equal to} or more than the predetermined potential difference V _n .

Once the abnormality detection signal h is output at the timing T5, the transistor of the hold circuit C is turned on by the signal, and the resistor R42 and the resistor R5 are short-circuited. Therefore, the variation voltage g is forced to V5. It is brought to a lower state and remains below the reference voltage f. Therefore, the abnormality detection signal h is still output and the LED of the display circuit 9 continues to light. When the hold circuit C is not provided, the fluctuating voltage g finally becomes the voltage V5 as shown by the broken line.

When the switch 4 is turned off once according to the alarm of the display circuit 9, the abnormality detection signal h output thereby is canceled and the present circuit is reset. Even if the secondary battery is charged or a new dry battery is inserted, the LED of the display circuit 9 remains off and the above operation is repeated.

In the second embodiment, if the abnormality detection signal h is directly input to the CPU and processed, the hold circuit C becomes unnecessary. Further, instead of the comparator 1, an OP amplifier and a discriminating circuit may be used to detect and amplify the difference between the two signals, discriminate based on a predetermined potential difference, and output the abnormality detection signal h. In that case, the resistance of the fluctuating voltage detecting means B is adjusted so that the potential difference between the reference voltage f and the fluctuating voltage g becomes 0 in the steady state.

When the battery remaining amount monitoring circuit of this embodiment is always connected to the battery, it works well even in a device in which the fluctuation of the current consumption is small. That is, the change in the battery voltage when the load is changed from the no-load condition to a sudden drop, and the change in the battery voltage when the load is set to 0 (switch off) after long-term consumption is changed. The difference between the two signal voltages is detected.

[0038]

EFFECTS OF THE INVENTION In the battery remaining amount monitoring circuit of the present invention, the remaining capacity of the battery to be monitored is calculated as the difference between the delay reference signal and the delay fluctuation signal or the difference in the time constant, which has a delay time difference. Since the judgment is made based on the deviation between the average reference signal and the average fluctuation signal, it is not necessary to change the operating point setting due to the difference in battery voltage depending on the type and number of batteries, and it is not affected by the outside temperature, etc. The capacity of the battery can be monitored accurately and the battery can be managed appropriately.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of a battery remaining amount monitoring circuit according to the present invention.

FIG. 2 is a time chart of the battery remaining amount monitoring circuit of FIG.

FIG. 3 is a block diagram of a second embodiment of the battery remaining amount monitoring circuit according to the present invention.

FIG. 4 is a time chart of the battery remaining amount monitoring circuit of FIG.

[Explanation of symbols]

a, e Battery voltage b Delay reference signal c Delay variation signal d, h Abnormality detection signal f Reference voltage (Average reference signal) g Variation voltage (Average variation signal) 1 Comparator (Comparison means) 1a OP amplifier (Comparison means) 1b Discrimination Circuit (comparing means) 2 Battery 3 Load 4, 4a Switch 5 BBD (first delay detecting means) 6a, 6b Buffer (first delay detecting means) 7 Voltage dividing circuit (second delay detecting means) A Reference voltage Detecting means (first average detecting means) B Fluctuating voltage detecting means (second average detecting means) V _m , V _n Predetermined potential difference (predetermined value)

Claims (2)

[Scope of utility model registration request] 1. A first delay detecting means for delaying a variation of a battery voltage to be monitored in time and outputting it as a delay reference signal, and a time delay of the variation of the battery voltage shorter than that of the first delay detecting means. Second delay detecting means for outputting as a delay variation signal, comparing means for comparing the delay reference signal with the delay variation signal, and outputting an abnormality detection signal when a deviation of a predetermined value or more occurs, A battery remaining amount monitoring circuit characterized by comprising: 2. A first average detecting means for averaging fluctuations of a battery voltage to be monitored with a predetermined time constant and outputting as an average reference signal, and a fluctuation of the battery voltage smaller than the first average detecting means. The second which averages with a time constant and outputs as an average fluctuation signal
And an average detection means for comparing the average reference signal and the average fluctuation signal, and a comparing means for outputting an abnormality detection signal when a deviation of a predetermined value or more occurs, Quantity monitoring circuit.