JP4534439B2 - Battery level judgment circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a circuit for determining a remaining battery level.
[0002]
[Prior art]
Batteries, especially alkaline batteries that are often used in film cameras and digital cameras, will recover their output voltage once they are left unloaded for a long time even if their remaining capacity is low. May come. Therefore, the remaining battery level cannot be accurately determined from the output voltage at no load. In order to solve this problem, a camera is known in which an actuator such as a zoom motor for moving a photographing lens is used as a dummy load, and the remaining battery level is determined based on the battery voltage when the dummy load is driven (Patent Document 1). ).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-109438
[Problems to be solved by the invention]
The camera of Patent Document 1 has a large inrush current during driving because the actuator is a dummy load. Therefore, in order to accurately determine the remaining battery level, it is necessary to use the battery voltage after the current has stabilized. For this reason, there are problems such as a long driving time of the actuator and battery consumption, and noise generated by the operation of the actuator.
[0005]
In film cameras and digital cameras, various batteries such as lithium batteries and nickel metal hydride batteries are used in addition to alkaline batteries. These batteries have different characteristics such as output voltage and internal resistance, and output voltage change characteristics when they are used. The camera of Patent Document 1 cannot accurately determine the remaining battery levels of all these batteries.
[0006]
The present invention provides a remaining battery level determination circuit that can accurately determine the remaining battery level without using an actuator, and that can accurately determine the remaining battery level even between different types of batteries.
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention, in a battery remaining amount determination circuit that detects an output voltage of a battery and determines the remaining amount of the battery, a first load resistor connected to the battery and a second load resistor that is larger than the first load resistor. a load resistor, a detecting means for the first load resistor is detected and a second output voltage of the battery when the first output voltage and a second load resistor of the battery when connected is connected, by the detection means A first step of detecting the first output voltage to determine whether or not the first output voltage is equal to or higher than a first predetermined value; and detecting the second output voltage by detecting means to detect the second output voltage. And the second step of determining whether or not is greater than or equal to the second predetermined value in order, and if the determination is affirmative in both the first and second steps, the first output by the detection means The voltage is detected again and the first output voltage is greater than or equal to the third predetermined value. And control means for performing a third step of determining whether or not, first, if the determination is negative in either the second or third step, the determination means that there is no remaining capacity of the battery It is to be prepared.
A second aspect of the present invention, in the battery residual amount judging circuit according to claim 1, the control means is a plurality of times a third step at predetermined sampling intervals.
According to a third aspect of the present invention, in the battery remaining capacity determining circuit of the first or second aspect , the third predetermined value is smaller than the first predetermined value.
According to a fourth aspect of the present invention, in the remaining battery level determination circuit for detecting the output voltage of the battery and determining the remaining battery level, the first load resistance connected to the battery and the second load resistance that is larger than the first load resistance. Detecting means for detecting a load resistance, a first output voltage of the battery when the first load resistance is connected, and a second output voltage of the battery when the second load resistance is connected; Calculation means for calculating the internal resistance value of the battery based on the detected first output voltage and second output voltage, storage means for storing the initial value of the internal resistance value, and the first output voltage detected by the detection means Is compared with a predetermined value to determine the remaining battery level, and the amount of change in the internal resistance value calculated by the calculating unit based on the initial value stored in the storing unit is compared with the predetermined value. Determining means for determining the amount; When the output voltage is equal to or higher than the predetermined value and the change amount of the internal resistance value based on the initial value is equal to or lower than the predetermined value, the determination is made to determine the remaining battery level based on the first output voltage. Control means for controlling the means.
A fifth aspect of the present invention, in the battery residual amount judging circuit according to claim 4, the control unit detects the first output voltage by the detecting means whether or not said first output voltage is not less than the first predetermined value The first output voltage and the second output voltage are detected by the detection means, the internal resistance value is calculated by the calculation means, and the internal resistance value with reference to the stored initial value is calculated. If the amount of change is thereby sequentially performed and a second step of determining whether a second predetermined value or less, determination is positive in any of the first and second steps, first by the detection means 1 detects the output voltage again said first output voltage to perform the third step of determining whether a third predetermined value or more, determination means first, second or third step If negative determination is made in any of the above, there is no remaining battery power One in which a constant.
According to a sixth aspect of the present invention, in the remaining battery level determining circuit of the fifth aspect , the control means performs the third step a plurality of times at a predetermined sampling interval.
According to a seventh aspect of the present invention, in the remaining battery level determination circuit of the fifth or sixth aspect , the third predetermined value is smaller than the first predetermined value.
The invention of claim 8, in any one of the battery residual amount judging circuit according to claim 7, in which further comprising a timer means for operating the control means for a predetermined operating time.
According to a ninth aspect of the present invention, there is provided a camera comprising the battery remaining capacity determining circuit according to any one of the first to eighth aspects.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
-First embodiment-
The configuration of the first embodiment of the remaining battery level determination circuit of the present invention is shown in FIG. The remaining battery level determination circuit is mounted on various cameras such as a film type camera and a digital camera, and determines the remaining battery level for various types of batteries loaded in the camera. 1 includes a microcomputer 2, a DC / DC converter 3, a switch 4, transistors 5, 6 and resistors 7-10. The remaining battery level determination circuit 20 is connected to the drive circuits 11 and 12, the magnet 13, and the motor 14 that are components of the camera, and to the battery 1 loaded in the camera.
[0009]
As the battery 1, various types of batteries such as an alkaline battery, a lithium battery, and a nickel metal hydride battery are used. The drive circuits 11 and 12 are circuits for driving the magnet 13 and the motor 14, respectively, and perform predetermined operations in the camera by driving them. For example, the magnet 13 is used to open and close a shutter, and the motor 14 is used to adjust the focus of the taking lens.
[0010]
The microcomputer 2 of the battery remaining amount determination circuit 20 has terminals P0 to P5. When a power switch (not shown) of the camera is turned on, the switch 4 is closed and the voltage at the terminal P1 of the microcomputer 2 changes from H to L. H corresponds to the output voltage value of the battery 1 and varies depending on the type of battery 1 and the usage state. L represents the ground level, that is, the voltage value is about 0V.
[0011]
When the voltage at the terminal P1 changes from H to L, the microcomputer 2 outputs a control signal from the terminal P2 to the DC / DC converter 3. When this control signal is input, the DC / DC converter 3 supplies constant voltage power to the power supply terminal P0 of the microcomputer 2 for a predetermined operation time, for example, for 2 seconds. Meanwhile, the microcomputer 2 operates to perform the battery remaining amount determination process shown in FIG. When the predetermined time elapses, the constant voltage power from the DC / DC converter 3 is not supplied, and the microcomputer 2 ends the battery remaining amount determination process. Immediately after the power switch is turned on in this way, the microcomputer 2 operates for a predetermined operation time and executes a battery remaining amount determination process.
[0012]
In addition, after the battery remaining amount determination process immediately after the power switch is turned on, a control signal is output from the camera to the DC / DC converter 3 every time the user performs a predetermined operation on the camera. Is done. When this control signal is input, the DC / DC converter 3 supplies constant voltage power to the power supply terminal P0 of the microcomputer 2 for a predetermined operation time, as in the above case. Also at this time, the microcomputer 2 executes the remaining battery level determination process of FIG. Note that the predetermined operation on the camera includes, for example, a half-press operation of a release button.
[0013]
A flowchart of the remaining battery level determination process in FIG. 2 will be described below. In step S1, when a power switch (not shown) is turned on and the switch 4 is closed, the voltage at the terminal P3 is changed from H to L. As a result, the transistor 5 is turned on, and the output current from the battery 1 flows through the resistors 7 and 8. At this time, in order to avoid wasteful current consumption of the battery 1, resistors 7 and 8 having sufficiently large resistance values are used.
[0014]
In step S2, the voltage of the terminal P5 is measured, and the battery voltage of the battery 1 in a state where the resistors 7 and 8 are connected (hereinafter referred to as the first load connection) is detected. At this time, since the collector-emitter voltage of the transistor 5 and the resistance values of the resistors 7 and 8 are known, the battery voltage of the battery 1 is determined by the measured voltage value of the terminal P5, that is, the voltage value applied to the resistor 8. It can be detected. Here, it is assumed that the internal resistance R _bat of the battery 1 can be ignored.
[0015]
In step S3, it is determined whether or not the battery voltage at the time of connecting the first load detected in step S2 is 5 V or higher. If it is 5V or more, the process proceeds to step S4, and if it is less than 5V, the process proceeds to step S11. In step S4, the voltage H is output from the terminal P4 with a predetermined pulse width, for example, a pulse width of 10 ms. As a result, the transistor 6 is turned on for the duration of the pulse width, and the output current from the battery 1 flows through the resistor 10 during that time. The resistor 10 is a dummy load used for measuring the battery voltage of the battery 1 and has a resistance value that allows a current to flow appropriately so that the battery voltage of the battery 1 at the time of connection can be appropriately measured.
[0016]
In step S5, the voltage of the terminal P5 is measured while the pulse is output in step S4, and the battery voltage of the battery 1 in a state where the resistor 10 is connected (hereinafter referred to as a second load connection) is obtained. To detect. In this way, wasteful consumption of the battery 1 can be suppressed by flowing the current through the dummy load and detecting the battery voltage for a predetermined time that is determined by the pulse width and does not affect the power consumption of the battery 1. . At this time, by using the resistor 10 as a dummy load, an inrush current does not increase as in the actuator, a stable load can be obtained even for a short predetermined time, and noise is generated due to the operation of the actuator. Can be eliminated.
[0017]
In step S6, it is determined whether or not the battery voltage at the time of connecting the second load detected in step S5 is 4 V or higher. When it is 4V or more, the process proceeds to step S7, and when it is less than 4V, the process proceeds to step S11. After waiting 50 ms in step S7, in step S8, the battery voltage when the battery 1 is connected to the first load is detected in the same manner as in step S2. In step S9, it is determined whether or not the battery voltage detected in step S8 is 5 V or higher. If it is 5V or more, the process proceeds to step S10, and if it is less than 5V, the process proceeds to step S11.
[0018]
If all the determinations in steps S3, S6, and S9 are affirmed, a display indicating that the remaining battery level is present is displayed on a display unit (not shown) of the camera in step S10. Thereby, the user can recognize that the battery 1 can still be used. On the other hand, if the determination in any of steps S3, S6, or S9 is negative, a display indicating no remaining battery power is displayed on the display unit of the camera in step S11. Thereby, the user can recognize that the battery 1 has no remaining battery power and needs to be replaced.
[0019]
In step S12, it is determined whether or not constant voltage power is supplied from the DC / DC converter 3. If it is supplied, the process returns to step S7, and if not, the process of FIG. 2 is terminated. That is, when step S6 is affirmed, the process from step S7 to step S12 is repeated, so that the battery voltage detection at the time of connecting the first load with the standby time (50 ms) in step S7 as the sampling period is determined as DC / DC This is performed only for a predetermined operation time during which constant voltage power is supplied from the converter 3.
[0020]
According to the first embodiment described above, the following operational effects can be obtained.
(1) The output voltage when the first load is connected is detected (step S2), and it is determined whether or not the output voltage is a predetermined value or more (step S3). Moreover, the output voltage at the time of 2nd load connection is detected (step S5), and it is determined whether the output voltage is more than predetermined value (step S6). If both of these output voltages are greater than or equal to a predetermined value, the output voltage when the first load is connected is further detected (step S8), and the remaining battery level is determined based on the output voltage. (Step S9). Since it did in this way, a battery remaining charge can be determined correctly, without driving an actuator.
(2) The output voltage of the battery 1 when the first load is connected is detected (step S2), and it is determined whether or not the output voltage is equal to or higher than a predetermined value (step S3). An output voltage is detected (step S5), and it is determined whether or not the output voltage is a predetermined value or more (step S6). If these determination results are both affirmative, the output voltage at the time of the first load is detected again (step S8), and it is determined whether or not the output voltage is equal to or higher than a predetermined value (step S8). If a negative determination is made in any one of steps S3 and S6, it is determined that there is no remaining battery 1 (step S11). Since it did in this way, battery remaining charge can be determined, without applying a load to a battery.
(3) Since steps S8 and S9 are performed a plurality of times at a predetermined sampling period, the remaining battery level can be determined more accurately.
(4) Since the power is supplied from the DC / DC converter 3 to the microcomputer 2 for a predetermined operation time (step S12) and the microcomputer 2 is operated only during that time, the remaining battery level determination process is performed. Can prevent unnecessary battery consumption.
[0021]
-Second Embodiment-
FIG. 3 shows a second embodiment of the remaining battery level determination circuit according to the present invention. The remaining battery level determination circuit 20A includes a microcomputer 2A instead of the microcomputer 2 in the first embodiment described above, and further includes an EEPROM 15. Since the configuration other than this is the same as that of the first embodiment, a description thereof will be omitted below.
[0022]
The microcomputer 2A has a terminal P6 in addition to the terminals P0 to P5 in the microcomputer 2 of the first embodiment described above. The EEPROM 15 is connected to the terminal P6. The EEPROM 15 is a ROM capable of electrically rewriting stored memory contents from the outside.
[0023]
A flowchart of the remaining battery level determination process executed in the microcomputer 2A is shown in FIG. This process is similar to the battery remaining amount determining process in the first embodiment shown in the flowchart of FIG. 2 after the battery remaining amount determining process immediately after the power switch is turned on or when a predetermined operation is performed. When performed, the constant voltage power is supplied from the DC / DC converter 3 for a predetermined operation time. In addition, about the process of the same step number as the flowchart of FIG. 2, the same process is performed also in this FIG. 4, and description is abbreviate | omitted below.
[0024]
In step S3A, the battery voltage (referred to as battery voltage A) at the time of connecting the first load detected in step S2 is stored in the EEPROM 15. In step S5A, the battery voltage (referred to as battery voltage B) at the time of connecting the second load detected in step S5 is stored in the EEPROM 15. At this time, the battery voltage A is stored in a different memory area from that stored in step S3A.
[0025]
In step S5B, the internal resistance value of the battery 1 is calculated from the battery voltage A stored in step S3A and the battery voltage B stored in step S5A by the following equation (1).
[Expression 1]
R _bat ≈ R ₁₀ · {(V _A −V _B ) / V _B } (1)
However, R _bat : Internal resistance value of battery 1 R ₁₀ : Resistance value of resistor 10 V _A : Value of battery voltage A V _B : Value of battery voltage B
In step S6A, it is determined whether or not the amount of change (increase rate) with respect to the initial value of the internal resistance value _Rbat of the battery 1 calculated in step S5B is 20% or less. At this time, the EEPROM 15 stores the initial value (R _bat0 ) of the internal resistance value R _bat of the battery 1, and the calculated internal resistance value R _bat is in a range of 120% or less of the initial value R _bat0. In some cases, the amount of change is 20% or less. If the change amount is 20% or less, the process proceeds to step S7, and if it is greater than 20%, the process proceeds to step S11. The initial value R _bat0 is the internal resistance value R _bat calculated in step _S5B when the process of FIG. 4 is executed for the first time immediately after the battery 1 is replaced. Alternatively, a plurality of initial values R _bat0 are stored in advance for each type of battery, and the user selects a type of battery used as the battery 1 to select from the plurality of initial values R _bat0. Also good.
[0027]
According to the second embodiment described above, the following operational effects can be obtained.
(1) The output voltage when the first load is connected is detected (step S2), and it is determined whether or not the output voltage is a predetermined value or more (step S3). Further, the output voltage when the second load is connected is detected (step S5), and the internal resistance value of the battery 1 is calculated based on the detected output voltages when the first and second loads are connected (step S5B). It is determined whether or not the internal resistance value is equal to or less than a predetermined value (step S6A). When the detected output voltage when the first load is connected is equal to or greater than a predetermined value and the calculated internal resistance value is equal to or less than the predetermined value, the output voltage when the first load is connected is detected ( In step S8, the remaining battery level is determined based on the output voltage (step S9). Since it did in this way, in addition to the effect in 1st Embodiment, a battery remaining charge can be correctly determined also between the batteries from which a kind differs. Moreover, since the change of internal resistance is observed, the battery can be used up sufficiently.
(2) The output voltage of the battery 1 when the first load is connected is detected (step S2), and it is determined whether or not the output voltage is equal to or higher than a predetermined value (step S3). The output voltage is detected (step S5), the internal resistance value of the battery 1 is calculated (step S5B), and it is determined whether the internal resistance value is equal to or less than a predetermined value (step S6A). If both of these determination results are affirmative determination, the output voltage at the first load is detected again (step S8), and it is determined whether or not the output voltage is equal to or higher than a predetermined value. While the remaining amount is detected (step S9), if a negative determination is made in either step S3 or S6A, it is determined that there is no remaining amount of the battery 1 (step S11). Since it did in this way, a battery remaining charge can be determined still more correctly.
[0028]
In addition, each numerical value used in the above embodiment is not limited to this, and each battery output voltage when the first load is connected and when the second load is connected is detected to appropriately determine whether or not the remaining battery level is present. Any numerical value may be used as long as it can be determined. At this time, the threshold when determining the output voltage when the first load is connected in step S3 and the threshold when determining the output voltage when the second load is connected in step S9 are the same value or The latter is preferably smaller than the former. In this way, if the threshold value for the determination in step S3 that is performed first is set higher and the threshold value for the determination in step S9 that is repeatedly performed later is set lower than that, the battery is further increased. Can be used up fully.
[0029]
In the above embodiment, the presence / absence of the remaining battery level is displayed in two stages, but a plurality of threshold values are set for the detected output voltage value of the battery, thereby determining the remaining battery level. May be displayed by an arbitrary number of steps.
[0030]
In the above embodiment, the first load resistance is realized by the resistors 7 and 8, the second load resistance is the resistance 10, the storage means is realized by the EEPROM 15, the timer means is realized by the microcomputer 2 or the microcomputer 2A, the detection means, the determination means, the control means, Each means of the calculation means is realized by the microcomputer 2 or 2A. However, the present invention is not limited to the above-described embodiment, and other modes conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.
[0031]
【The invention's effect】
According to the present invention, since it is configured as described above, it is possible to reduce battery consumption when the remaining battery level is detected, and to accurately detect the remaining battery level between different types of batteries.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a first exemplary embodiment of the present invention.
FIG. 2 is a flowchart showing the content of a remaining battery level determination process executed in the first embodiment.
FIG. 3 is a diagram showing a configuration of a second exemplary embodiment of the present invention.
FIG. 4 is a flowchart showing the contents of a remaining battery level determination process executed in the second embodiment.
[Explanation of symbols]
1: Battery 2, 2A: Microcomputer 3: DC / DC converter 4: Switch 5, 6: Transistors 7, 8, 9, 10: Resistors 11, 12: Drive circuit 13: Magnet 14: Motor 15: EEPROM

Claims (9)

In the remaining battery level determination circuit that detects the battery output voltage and determines the remaining battery level,
A first load resistor connected to the battery; a second load resistor greater than the first load resistor;
Detecting means for detecting a first output voltage of the battery when the first load resistor is connected and a second output voltage of the battery when the second load resistor is connected;
A first step of detecting the first output voltage by the detection means to determine whether the first output voltage is greater than or equal to a first predetermined value; and detecting the second output voltage by the detection means The second step of determining whether or not the second output voltage is equal to or higher than a second predetermined value is sequentially executed, and an affirmative determination is made in both the first and second steps. Control means for detecting the first output voltage again by the detection means and executing a third step of determining whether the first output voltage is equal to or higher than a third predetermined value;
A battery remaining capacity determination circuit comprising: a determination unit that determines that the remaining battery capacity is not present when a negative determination is made in any of the first, second, and third steps . In the battery remaining capacity determination circuit according to claim 1 ,
The battery remaining capacity determination circuit, wherein the control means performs the third step a plurality of times at a predetermined sampling interval. In the battery remaining capacity determination circuit according to claim 1 or 2 ,
The battery remaining capacity determination circuit, wherein the third predetermined value is smaller than the first predetermined value. In the remaining battery level determination circuit that detects the battery output voltage and determines the remaining battery level,
A first load resistor connected to the battery; a second load resistor greater than the first load resistor;
Detecting means for detecting a first output voltage of the battery when the first load resistor is connected and a second output voltage of the battery when the second load resistor is connected;
Calculating means for calculating an internal resistance value of the battery based on the first output voltage and the second output voltage detected by the detecting means;
Storage means for storing an initial value of the internal resistance value;
The remaining battery level is determined by comparing the first output voltage detected by the detection unit with a predetermined value, and is calculated by the calculation unit based on the initial value stored by the storage unit. Determination means for determining the remaining battery level by comparing the amount of change in the internal resistance value with a predetermined value;
When the first output voltage is greater than or equal to a predetermined value and the amount of change in the internal resistance value based on the initial value is less than or equal to a predetermined value, the remaining battery level is determined based on the first output voltage. And a control means for controlling the determination means so as to determine the battery level. In the battery remaining amount determination circuit according to claim 4 ,
Said control means includes first determining whether the first output voltage is detected and the first output voltage is not less than the first predetermined value by the detecting means, wherein the said detecting means the One output voltage and the second output voltage are detected, the internal resistance value is calculated by the calculating means, and the amount of change in the internal resistance value based on the stored initial value is equal to or less than a second predetermined value and executes a second step of determining whether or not sequential, if an affirmative determination is made in any of the first and second step, again detecting the first output voltage by said detecting means the first output voltage to perform the third step of determining whether a third predetermined value or more and,
The battery remaining capacity determining circuit according to claim 1, wherein the determination means determines that there is no remaining battery power when a negative determination is made in any of the first, second, and third steps. In the remaining battery level determination circuit according to claim 5 ,
The battery remaining capacity determination circuit, wherein the control means performs the third step a plurality of times at a predetermined sampling interval. In the battery remaining capacity determination circuit according to claim 5 or 6 ,
The battery remaining capacity determination circuit, wherein the third predetermined value is smaller than the first predetermined value. In the battery remaining amount determination circuit according to any one of claims 1 to 7 ,
A battery remaining capacity determination circuit further comprising timer means for operating the control means for a predetermined operating time. A camera comprising the battery remaining capacity determination circuit according to claim 1 .

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