JP4405232B2 - Voltage detection method and apparatus, and electronic apparatus - Google Patents

Description

  The present invention relates to a voltage detection method, a voltage detection device, and an electronic device, and in particular, for example, a voltage detection method and a voltage detection device capable of more accurately calculating a remaining capacity (remaining discharge capacity) of a battery, In addition, the present invention relates to electronic equipment.

  In recent years, portable devices represented by, for example, mobile phones and portable terminal devices have become widespread. In these portable devices, a primary battery such as an alkaline battery or a manganese battery, or a secondary battery such as a nickel cadmium storage battery, a nickel hydride storage battery, or a lithium ion storage battery is used as the power source.

  The discharge capacity of these primary batteries or secondary batteries that serve as power sources, for example, greatly affects the continuous usable time of devices in which those batteries are used as power sources, and is an important factor for performance evaluation in portable devices. Become.

  In portable devices using these batteries as a power source, it is the remaining capacity of the discharge capacity that is important together with the total discharge capacity of the battery. In general portable devices, the remaining capacity of the battery that is the power source is monitored as necessary so that the remaining capacity is not suddenly lost and the power supply is cut off. The remaining capacity is displayed on a display or the like so that the user can visually recognize it.

  For example, when the remaining capacity is displayed on the mobile phone, the user can estimate the remaining callable time or the time when charging work or battery replacement work is necessary.

  Here, a system configuration example in which this type of mobile phone is used will be described. For example, a system configuration shown in FIG. 7 can be considered. In FIG. 7, a plurality of prepared base stations 1 and 2 for wireless communication are connected to a network 4 which is a digital circuit network, and also connected to a PSTN (Public Switched Telephone Network) station 3 which is an exchange station for a wired telephone. It is. A predetermined service provider 5 is connected to the network 4, and various services can be received according to the contract contents by accessing the service provider 5 from the mobile phone side via the network 4.

  This service uses, for example, SMS-PP (Short Message Service Point-To-Point) or broadcast SMS-CB (Short Message Service Cell Broadcast) to send predetermined data to a mobile phone. Based on the response to the message, information such as a service user message and a selection result is transmitted to the mobile phone. Further, access to the Internet may be performed.

  The mobile phone 6 performs wireless communication 1a with the nearest base station 1 and is connected to the network 4 which is a digital circuit network. In addition, the base station 2 can perform wireless communication 2 a with another mobile phone 7 to connect to the network 4.

  Each mobile phone 6 periodically transmits a control signal to the base station in accordance with a schedule instruction transmitted from the nearest base station 1 when in an idle state where no line is connected. Thereby, the mobile phone 6 recognizes that it is under the control of the base station 1 and performs call connection maintenance. Similarly, the cellular phone 7 also maintains a call connection by transmitting a control signal to the nearest base station 2.

  For example, when the mobile phone 6 makes a call to the mobile phone 7, the user of the mobile phone 6 inputs the telephone number of the mobile phone 7 and operates the call button to instruct the mobile phone 6 to perform dialing processing. To do. The cellular phone 6 instructed to perform dialing processing performs wireless communication with the base station 1 and connects to the base station 2. The dial transmission process may be automatically executed by software stored in a storage unit built in the mobile phone 6.

  The base station 1 communicates with the base station 2 in which the location of the mobile phone 7 is registered via the network 4 and an exchange station (not shown). The base station 2 communicates with the mobile phone 7 based on the communication. Perform wireless communication. In this way, the mobile phone 6 and the mobile phone 7 are finally connected and a call can be made.

  As a method of measuring the remaining battery capacity applicable to a mobile phone used in such a system, there is a method of measuring the output voltage of the battery in use. FIG. 8 is a diagram showing the principle of a conventional remaining capacity measuring method applied to the mobile phone 6 shown in FIG.

  In FIG. 8, the power source 6a is, for example, a primary battery such as an alkaline battery or a manganese battery, or a secondary battery such as a nickel cadmium storage battery, a nickel hydride storage battery, or a lithium ion storage battery, and is configured by a main circuit or the like. Is connected to a load 6c to supply power. As shown in FIG. 8, the power supply unit 6a is equivalently configured by a battery cell (hereinafter simply referred to as a battery) 6b which is a voltage source and an internal resistance Ri.

  In such a circuit, the output voltage V0 of the power supply unit 6a is measured, and the remaining capacity of the power supply unit 6a is calculated from the value of the output voltage V0 using a discharge characteristic table of the power supply unit 6a prepared in advance. Is done.

  However, various processes are performed in the load 6c which is the main circuit, and the power consumption of the load 6c varies greatly depending on the contents of the processes. That is, a load current i flows between the power supply unit 6a and the load 6c, and the value of the load current i changes depending on the state of the load 6c. Accordingly, the amount of voltage drop due to the internal resistance Ri also changes, and the value of the measured output voltage V0 changes, so that there are cases where the remaining capacity cannot be calculated more accurately than the output voltage V0.

  Therefore, when the load 6c in FIG. 8 is a cellular phone, the internal impedance of the power source 6a is obtained by measuring the output voltage V0 when the value of the load current i is known, and the internal A method for obtaining the remaining capacity by utilizing the correlation between the impedance and the remaining capacity of the power supply unit 6a has been proposed.

  That is, FIG. 9 is a diagram showing the principle of a conventional TDMA synchronous voltage detection method, which is one of methods for measuring the output voltage V0, assuming that the load current i is a known value.

  9, the waveform of FIG. 9A is a waveform of a transmission time slot (TDMA (Time Division Multiple Access) TX Timeslot). The TDMA system is a wireless communication technology used in wireless communication systems such as GSM (Global System for Mobile Communications) and PDC (Personal Digital Cellular), and is a process that performs transmission and reception in a time-sharing manner. The slot indicates burst timing (Burst Timing) output at the time of transmission.

  The waveform of FIG. 9B shows the waveform of the output voltage V0 (battery output voltage) of the power supply unit, and the pulse of FIG. 9C is the sampling time that is the timing for measuring the output voltage V0 of the power supply unit. Is shown.

  When a burst is output in the transmission time slot shown in FIG. 9A (T−1, T0, and T + 1), the load current i shown in FIG. 8 becomes large, so that the waveform of FIG. As shown, the value of the output voltage V0 of the power supply section drops (V-1, V0, and V + 1). The output voltage V0 is measured at the timing (S-1, S0, and S + 1) at which the burst is output, as shown in the pulse of FIG. 9C. Then, the internal impedance of the power supply unit is obtained from the output voltage V0 and the load current i, and the remaining capacity of the secondary battery (battery) built in the power supply unit is calculated from the internal impedance.

  In this case, the load current i is recognized using a power class value (Power Class) that adjusts the transmission output of radio waves. That is, a power class value (Power Class) for controlling transmission output is supplied from a base station to a general mobile phone, and the mobile phone transmits a control signal, call data, etc. to the base station. In order not to adversely affect the control signal or call data transmitted from other mobile phones, the transmission output in the transmission time slot described above is used for all the transmission levels in the base station using the power class value. Adjusted to be the same for mobile phones.

  This power class value is increased or decreased in proportion to the distance from the base station to the mobile phone. That is, the power class value is adjusted so that the transmission output decreases as the distance between the base station and the mobile phone decreases. Conversely, the power class value increases so that the transmission output increases as the distance between the base station and the mobile phone increases. Is adjusted. In the mobile phone, the power consumption in the amplifier circuit of the transmitter of the mobile phone is calculated from the power class value, and the load current i is calculated from the power consumption.

  However, the load current i changes depending on other processing operations. That is, as shown in the waveform of FIG. 9B, the output voltage measured at timing S-1 corresponding to T-1 which is the timing at which the burst is output in the transmission time slot (TDMA TX Timeslot). The output voltage V0 measured at the timing S0 corresponding to V-1 and T0 and the output voltage V + 1 measured at the timing S + 1 corresponding to T + 1 take different values.

  Specifically, from timing S-1 to S0, other processing operations decrease, the load current decreases, the output voltage increases, and the value of the output voltage V0 is the value of the output voltage V-1. It is getting bigger. Further, from timing S0 to S + 1, other processing operations increase, the load current increases, the output voltage decreases, and the value of the output voltage V + 1 is smaller than the value of the output voltage V0.

  As described above, the actual load current i includes not only the current flowing through the amplifier circuit of the transmission unit of the mobile phone but also the current flowing through the block that performs various other processes in the mobile phone. If the internal impedance of the power supply unit is obtained using the current flowing through the amplifier circuit as the load current i, a large error may be included in the calculated value of the internal impedance.

  Further, as a method for calculating the remaining capacity, for example, there is a method of integrating all currents during charging / discharging of the power supply unit. In this current integration method, the maximum current capacity of the power supply unit needs to be measured in advance by some method. In addition, the maximum current capacity of the power supply section varies greatly depending on temperature characteristics and changes with time. Therefore, a very complicated correction calculation process may be required. Furthermore, since the necessary correction calculation processing differs based on the type of the power supply unit and the like, information on the power supply unit is required in advance whenever the power supply unit is replaced.

Patent Document 1 discloses a process for displaying a battery remaining amount in an electronic device that uses this type of secondary battery as a power source. In the process described in Patent Document 1, in order to accurately determine the remaining battery capacity, the output of the battery voltage detection amplifier is input to a microcomputer, and the remaining battery capacity is obtained by calculation in the microcomputer. It is like that.
JP-A-11-215718

  As described above, even if the output voltage V0 and load current of the power supply unit are simply measured, and the remaining battery level is detected only by calculation based on the values, the detection accuracy of the remaining battery level is limited. Yes, as a method of detecting the remaining battery level with higher accuracy, connect a small resistor for current detection between the power supply and the load, and the current detection resistance is equivalent to the internal resistance in the power supply. There is a method of performing processing that can be performed. That is, as shown in FIG. 2 described in an embodiment described later, a current detection resistor Rd is connected between the power source 50 and the load 59, and the output of the power source is connected between the power source 50 and the resistor Rd. The voltage V0 is detected, and the voltage Vd is also detected between the resistor Rd and the load 59.

  The voltage obtained by subtracting the voltage drop caused by the internal resistance Ri in the power supply 50 from the constant voltage generated by the battery 51 becomes the output voltage V0 of the power supply. Thus, the current detection resistor Rd is provided. Thus, the current consumption current i can be monitored, that is, the current consumption current i can be detected using the difference between the output voltage V0 and the detection voltage Vd and the resistance value of the resistor Rd. . Furthermore, if the resistance Rd for current detection and the internal resistance Ri can be made equivalent, a voltage corresponding to the output voltage of the power supply when there is no load can be obtained, and voltage measurement independent of the load current is possible. .

This can be expressed by the following formula. First, the load current i is expressed by the following equation.

Further, the internal resistance Ri is expressed by the following equation when the voltage Vbat (constant voltage) of the battery itself is used.

From these [Expression 1] and [Expression 2], the following expression is obtained.

これは、即ち電流検出抵抗Ｒｄの両端で生じる電圧差を、このＧ倍したことで等価となることを示している。 Furthermore, the following formula is obtained from the formula [3].

This indicates that the voltage difference generated at both ends of the current detection resistor Rd is equivalent by multiplying the voltage difference by G.

  FIG. 10 shows the state calculated and corrected in this way. The vertical axis in FIG. 10 shows the change in the output voltage of the power supply, and the horizontal axis shows the remaining battery level in the power supply. The initial voltage Vini indicates an output voltage at full charge determined by the characteristics of the battery. Further, the discharge curve α indicates the relationship between the power supply output voltage and the remaining capacity when the battery is discharged under a certain condition given by the characteristics of the battery. Here, when the measured voltage Vm of the power supply output voltage is detected, if it is a certain load current, it is affected by the internal resistance Ri, so that the remaining voltage Vm and the discharge curve α are obtained. The capacity Cm cannot be said to be an accurate remaining amount due to the influence of the load current. Here, the correct remaining voltage C1 at this time is calculated by adding the correction voltage based on the above-mentioned [Equation 1] to [Equation 4] to the measured voltage Vm to obtain the corrected voltage Vmc. Is done.

  The circuit configuration shown in FIG. 11 shows a configuration for executing a process of obtaining a corrected voltage by adding a correction voltage based on the [Equation 1] to [Equation 4]. As a configuration in which the terminal 81 to which the power source is connected is connected to the load side via the current detection resistor Rd, one end of the resistor Rd (the side connected to the terminal 81, that is, the power source side) is connected to the resistors R11 and R12. The other end side (that is, the load side) of the resistor Rd is grounded via a series circuit of resistors R13 and R14. The resistance values of the resistors R11 and R12 are made equal, and the resistance values of the resistors R13 and R14 are also set to be equal to each other, and a voltage obtained by halving the output voltage V0 and the detection voltage Vd is obtained at the midpoint of connection between the two resistors. Then, the connection midpoint of the resistors R11 and R12 is connected to the + side input end of the first amplifier 82, and the connection midpoint of the resistors R13 and R14 is connected to the − side of the first amplifier 82 via the resistor R15. The input terminal is connected, and the negative input terminal and the output terminal of the first amplifier 82 are connected by a resistor R16. The first amplifier 82 amplifies a voltage drop generated in the current detection resistor Rd, and the gain of the first amplifier 82 is set to the gain expressed by the above-described [Equation 4]. This gain is determined by resistors R15 and R16.

  Further, the output terminal of the first amplifier 82 is connected to the negative input terminal of the second amplifier 83 via the resistor R18, and the terminal 84 from which the reference voltage Vref is obtained is connected to the second amplifier 83 via the resistor R17. Connect to 83 + input terminal. Further, the connection middle point of the resistors R11 and R12 is connected to the negative input terminal of the second amplifier 83 via the resistor R19, and the negative input terminal and the output terminal of the second amplifier 83 are connected by the resistor R20. . The second amplifier 83 is for adding the correction voltage output from the first amplifier 82 to the voltage at the midpoint of the resistors R11 and R12. Therefore, the measurement voltage from which the influence of the load current described in [Expression 1] to [Expression 4] is removed is obtained as the output of the second amplifier 83.

  Then, the signal obtained at the output terminal of the second amplifier 83 is supplied to the analog / digital converter 85, sampled at a timing synchronized with the sampling pulse obtained at the terminal 87, digitally converted, and converted data. Is output via the output register 86. This output data is supplied to the central control unit (CPU) of this device. The cycle for sampling by the converter 85 is a cycle set for the CPU to monitor the power supply. On the CPU side, for example, it is determined which position in the discharge curve in FIG. 10 the supplied voltage data corresponds to, the remaining amount of the battery as a power source is determined, and display based on the remaining capacity is performed. Had to do.

  However, the processing shown in FIGS. 10 and 11 has a problem that the load on the CPU side of the device is heavy. That is, the voltage data measured by the circuit configuration of FIG. 11 is sent to the CPU of the device, and the position in the discharge curve α shown in FIG. 10 in the CPU corresponds to the memory connected to the CPU. Therefore, it is necessary to refer to the data of the discharge curve α and calculate the remaining amount from the determined position, and there is a problem that the CPU needs a lot of processing for monitoring the remaining amount of the battery.

  Further, although not shown in the configuration of FIG. 11, in order to measure the remaining battery level more accurately, it is necessary to correct the temperature characteristics of the battery. When the temperature characteristic correction is also performed, the CPU needs to perform the correction calculation process for that purpose, and there is a problem that the burden on the CPU becomes larger.

  The present invention has been made in view of the above points, and an object of the present invention is to make it possible to easily perform accurate measurement of the remaining battery level without imposing a burden on a control means such as a CPU.

In the present invention, when detecting an output voltage of a power source constituted by a battery, the two terminals of a current detecting resistor connected in series between the power source and the load to detect a load current flowing in the load are provided. The gain variable amplification processing that obtains the voltage drop value due to the load current in the internal resistance of the power supply by amplifying the voltage of the power supply, and the voltage that is detected based on the temperature of the power supply Based on a gain control value conversion process for converting to a gain control value, an output voltage detection process for correcting the output voltage of the battery based on the obtained voltage drop value, and an output voltage conversion table for correcting the discharge characteristics of the battery substantially linearly Thus, voltage correction processing for correcting the output voltage detected in the voltage detection processing is performed.

  By doing so, the detected output voltage changes almost linearly in proportion to the remaining battery level, and the correspondence with the remaining battery level can be taken easily. For example, based on the detected data Thus, the process of displaying the remaining battery level can be easily performed from the detection data.

  According to the present invention, correspondence between the detected output voltage and the remaining battery level can be easily achieved, and processing based on voltage detection data can be easily performed. Therefore, for example, it is possible to greatly reduce the processing load on the control means such as a CPU, and the control configuration in the apparatus to which the present invention is applied can be simplified.

  In this case, temperature compensation is also performed by obtaining a gain control value for amplifying the voltage detected by the load current detection resistor from the voltage detected based on the temperature of the power supply, and performing gain control. The temperature compensation, which was impossible without external support such as a CPU, can be performed only by the processing in the battery voltage detection unit, so that an accurate remaining battery level can be easily detected.

  In addition, the output voltage conversion table for converting the output voltage into a substantially linear discharge characteristic is configured as a memory having a MONOS structure, and is configured on the same integrated circuit as a circuit for performing voltage detection processing and voltage correction processing. Thus, an integrated circuit that performs the processing of the present invention can be configured easily.

  In addition, by providing a remaining capacity calculation means for calculating the remaining capacity of the battery based on the voltage-corrected output voltage, a display means for the remaining capacity calculated by the remaining capacity calculation means, etc., display of the remaining capacity, etc. It is possible to easily calculate the remaining battery capacity in the remaining capacity calculation means for performing.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
In this example, the present invention is applied to a process for measuring the remaining capacity of a secondary battery (such as a lithium ion storage battery) incorporated in an electronic device. FIG. 1 is a diagram showing a configuration example of a mobile phone as an example of an electronic apparatus incorporating a configuration for performing the processing of this example. As a wireless network system configuration in which a mobile phone is used, for example, the system configuration of FIG. 7 described in the conventional example is applicable.

  The configuration example of the mobile phone shown in FIG. 1 will be described. The antenna 11 is connected to a reception RF (Radio Frequency) unit 13 and a transmission RF unit 28 via a selector 12, and serves as both a reception antenna and a transmission antenna. First, the configuration of the reception system will be described. The reception RF unit 13 performs band limitation using an intermediate frequency filter, AGC (Automatic Gain Control), etc. on the reception signal supplied from the antenna 11 via the selector 12. Then, the processed received signal is supplied to the mixer 14.

  The mixer 14 multiplies the reception signal supplied from the reception RF unit 13 by the signal supplied from the local oscillation unit 20 configured by a local oscillator or the like so as to obtain a reception signal having a predetermined frequency. The received signal (intermediate frequency signal) obtained by extracting the frequency is supplied to a reception IF (Intermediate Frequency) unit 15. The reception IF unit 15 digitally converts the acquired reception signal, and supplies it to the reception demodulation unit 16 as I data and Q data of a predetermined bit rate whose phase and amplitude are orthogonally modulated.

  The reception demodulator 16 performs processing for removing influences such as fading, received signal type discrimination processing, deinterleaving processing for separating multiplexed signals, and error correction for the received signals of I data and Q data. Error control processing and the like are performed, and appropriate decoding is performed to separate voice data and communication data. Then, the reception demodulation unit 16 supplies the separated audio data to the audio decoding unit 17 and supplies the separated communication data to the communication data decoding unit 21.

  The audio data is compressed by being divided into blocks for each received burst, and the audio decoding unit 17 decompresses the acquired audio data by a predetermined method, decodes it, converts it to analog, and supplies it to the speaker amplifier 18. To do. The speaker amplifier 18 amplifies the supplied audio signal and outputs it from the speaker 19. Further, the communication data decoding unit 21 to which communication data is supplied from the reception demodulating unit 16 decompresses and decodes the acquired communication data by a predetermined method, and via a bus line, a central control unit (CPU) 30, a RAM 32, etc. To supply.

  Next, the configuration of the transmission system will be described. Speech input to the microphone 22 is converted into an electrical signal, supplied to the microphone amplifier 23, amplified, and then supplied to the speech encoding unit 24. The audio encoding unit 24 performs digital conversion on the acquired audio signal at a predetermined sampling rate, encodes it, and then performs compression processing. Then, the audio encoding unit 24 divides the compressed audio data into blocks corresponding to the burst signal for transmission, and supplies the divided data to the transmission modulation unit 25.

  The communication data encoding unit 29 encodes communication data supplied from the CPU 30 or the like via the bus line, compresses the data, and divides the data into blocks corresponding to the burst signal for transmission. To supply. The transmission modulation unit 25 multiplexes the acquired audio data and communication data, and performs orthogonal modulation to express I data and Q data of a predetermined bit rate (expressed on a plane defined by the orthogonal I axis and Q axis) Symbol) as a symbol). The transmission IF unit 26 converts the acquired I data and Q data into analog modulation signals and supplies them to the mixer 27.

  The mixer 27 multiplies the analog modulation signal supplied from the transmission IF unit 27 by the signal supplied from the local oscillation unit 20 configured by a local transmitter or the like so that a transmission signal having a predetermined frequency is obtained. Then, a transmission signal having a predetermined frequency is supplied to the transmission RF unit 28. The transmission RF unit 28 amplifies the supplied transmission signal, supplies it to the antenna 11 via the selector 12, and radiates it.

  The CPU 30 which is a control means for controlling the operation of each part of the mobile phone of this example executes various processes according to programs stored in the ROM 31 or the EEPROM 33. Further, an RTC (Real Time Clock) 34 having a clock function is connected to the bus line, and time information held in a RAM or the like built in the RTC 34 is supplied to each unit under the control of the CPU 30.

  In addition, the CPU 30 is configured to control data transfer with each unit connected to the input / output interface 35. The input / output interface 35 includes a display 36 composed of display means such as an organic EL (Electro luminescence) display and LCD (Liquid Crystal Display), a key unit 37 composed of dial keys, jog dials, etc., an infrared interface and a digital data interface. A data communication unit 38 configured, an external storage unit 39 configured by a flash memory, a hard disk, and the like, a SIM slot unit 40 in which a memory card called a SIM (Subscriber Identity Module) is mounted, and the like are connected.

  The display 36 displays various menus, a telephone book in which telephone numbers are registered, and the like. An icon representing the remaining capacity of the battery built in the power supply 50 is also displayed. The icon display indicating the remaining battery capacity is displayed in a relatively limited number of stages, such as three or four stages.

  In addition, the cellular phone of this example includes a power source 50 that operates each unit, and the power source 50 includes a secondary battery that is configured by a lithium ion storage battery or the like. The output voltage of the power supply 50 is detected by the battery voltage detector 60 and the detected data is sent to the CPU 30. The CPU 30 refers to the output voltage data of the supplied power supply, determines the remaining capacity of the secondary battery, and displays an icon indicating the remaining capacity on the display 36.

  FIG. 2 is a diagram illustrating the principle of detecting the output voltage of the power supply 50 by the battery voltage detection unit 60. The power source 50 has a built-in battery 51 composed of a secondary battery. When shown by an equivalent circuit, the battery 51 is connected to an internal resistor Ri. In addition, in order to detect the temperature of the battery 51, the power supply 50 is provided with the thermistor 52, and the output of the thermistor 52 is also supplied to the battery voltage detection unit 60.

  The load 59 corresponds to each circuit block shown in FIG. 1, and a resistor Rd for detecting a load current is connected between the power supply 50 and the load 59. As the current detection resistor Rd, a very small resistance is adopted, so that the voltage drop at the current detection resistor Rd is negligible if the voltage drop at the load 59 is considered. Then, the output voltage V0 of the power supply is detected between the power supply 50 and the resistor Rd, and the voltage Vd is also detected between the resistor Rd and the load 59.

  The basic principle for detecting the accurate output voltage of the battery 51 from the output voltage V0 and the voltage Vd is the principle based on the formulas [1] to [4] described as the prior art. It is. That is, a voltage drop equivalent to the voltage drop caused by the internal resistance Ri in the power supply 50 is detected and corrected based on the difference between the output voltage V0 and the detection voltage Vd.

  FIG. 3 is a diagram illustrating a configuration of the battery voltage detection unit 60 of the present example. Each circuit that detects the battery voltage detection unit 60 of this example is configured by one or a plurality of integrated circuits, and a memory that is a data conversion table is also configured in the integrated circuit. The current detection resistor Rd already described is connected between the output terminal 61 of the power source 50 and the load 59, and one end side (the side connected to the terminal 61, that is, the power source side) of the resistor Rd is connected to the resistor. The other end side (that is, the load side) of the resistor Rd is grounded via the series circuit of the resistors R3 and R4. The resistance values of the resistors R1 and R2 are made equal, and the resistance values of the resistors R3 and R4 are also set to be equal, and the voltage obtained by dividing the output voltage V0 and the detection voltage Vd by half at the connection midpoint of both resistors, respectively. obtain. Then, the voltage obtained at the connection midpoint of the resistors R1 and R2 and the voltage obtained at the connection midpoint of the resistors R3 and R4 are supplied to the subtractor 62, and the difference between the two voltages V0 and Vd is detected. The difference is supplied to the variable gain amplifier 63. The gain of the variable gain amplifier 63 is controlled by control data supplied from a temperature correction table 75 described later. The gain of the variable gain amplifier 63 is a gain set by the equation (4) already described.

  Then, the output voltage of the variable gain amplifier 63, the voltage obtained at the connection midpoint of the resistors R1 and R2, and the reference voltage Vref obtained at the terminal 65 are supplied to the subtractor 64, and the variable gain is obtained from the reference voltage Vref. The output voltage of the amplifier 63 is subtracted from the connection midpoint voltage of the resistors R1 and R2. The voltage subtracted by the subtractor 64 is supplied to the amplifier 66, and the output of the amplifier 66 is supplied to the analog / digital converter 67. For example, the reference voltage Vref is set to ½ of the output voltage of the battery 51 when fully charged. By setting in this way, a measured value having a characteristic that the voltage rises from 0 V with discharge is obtained as the output of the amplifier 66.

  From the configuration in which the resistors R1 and R2 and the resistors R3 and R4 divide, the configuration from the amplifier 66 detects the voltage drop value due to the load current in the internal resistance Ri of the power source using the current detection resistor Rd, and this is detected. This corresponds to output voltage detection means for performing output voltage detection processing for correcting the output voltage of the power supply 50 by the voltage drop value. The correction in this output voltage detection process is a process for detecting (estimating) the battery output voltage when there is no load, based on the principles of the formulas [1] to [4] already described.

  The analog / digital converter 67 samples the output of the amplifier 66 into digital data at a timing based on the sampling pulse obtained at the terminal 70, and supplies the converted data to the voltage correction table 68. The voltage correction table 68 is a memory in which voltage data obtained by correcting the voltage data is written at an address corresponding to the input voltage data, and a page to be referred to is controlled by control data supplied from the temperature correction table 75. It is designed to change. That is, a table for performing voltage correction using optimal correction data for each temperature is provided. In this case, the voltage data corrected by the temperature correction table 75 is data that corrects the discharge characteristics of the battery 51 built in the power supply 50 substantially linearly. An example of correcting this discharge characteristic to be substantially linear will be described later.

  The voltage correction table 68 of this example is configured by a memory having a MONOS structure, and is configured on the same integrated circuit as other circuits in the battery voltage detection unit 60 which is basically an analog circuit. The basic structure of the MONOS structure memory is shown in FIG. 4 in which a tunnel oxide film 101, charge storage means 102, an insulating film 103, and a gate oxide film 104 are formed on a silicon substrate 100. A source 100 s and a drain 100 d are formed on the silicon substrate 100. Here, the charge storage means 102 is formed of Si3 N4 or the like, and electrons are injected into the charge storage means 102. With this configuration, even if there is a defect in the oxide film, it has the feature that the retained charge is not dissipated, the oxide film can be thinned, and the miniaturization is easy. The non-volatile memory can be configured on the integrated circuit configured as described above. Also in the case of this example, by utilizing this feature, the voltage correction table 68 is configured as a non-volatile memory in the integrated circuit configuring the battery voltage detection unit 60 that is an analog circuit. A temperature correction table 75 described later is also configured in the same integrated circuit.

  Returning to the description of FIG. 3, the corrected voltage data read from the voltage correction table 68 is output through the output register 69 and supplied to the CPU 30 shown in FIG. Also for the output register 69, the holding timing is controlled by the sampling pulse obtained at the terminal 70.

  The voltage correction table 68 and its peripheral configuration, that is, the analog / digital converter 67, the voltage correction table 68, and the output register 69 are based on an output voltage conversion table that corrects the discharge characteristics of the battery 51 substantially linearly. This corresponds to voltage correction means for performing voltage correction processing for correcting the output voltage detected in the voltage detection processing.

  In this example, the bias circuit 72 adds a bias voltage to the voltage obtained at the terminal 71 to which the output of the thermistor 52 in the power supply 50 is supplied, and then the analog / digital converter 73 converts it to digital data. The converted voltage data is accumulated in the register 74 and then input to the temperature correction table 75. For the analog / digital converter 73 and the register 74, the sampling timing is set by the sampling pulse obtained at the terminal 70.

  Similarly to the voltage correction table 68 described above, the temperature correction table 75 is also configured by a memory having a MONOS structure, and is configured in the same integrated circuit as other circuits in the battery voltage detection unit 60. The temperature correction table 75 is a table that obtains the gain of the variable gain amplifier 63 required at the temperature and the conversion table page data in the voltage correction table 68 based on the input voltage data that is voltage data corresponding to the battery temperature. is there. The gain control data read in the temperature correction table 75 is supplied to the variable gain amplifier 63 to set the gain corresponding to the battery temperature at that time. The page data of the conversion table in the voltage correction table 68 read by the temperature correction table 75 is supplied to the voltage correction table 68 to set the page used for conversion in the voltage correction table 68.

  FIG. 5 is a diagram showing an example of the principle of voltage correction in the battery voltage detection unit 60 of this example. In the case of this example, the battery 51 built in the power supply 50 changes as shown by the discharge curve Va in FIG. 5 as the remaining capacity decreases from the fully charged state. The relationship between the dischargeable time and the output voltage indicated by the discharge curve Va is not linear. Further, the discharge curve Va varies depending on the temperature. Here, in this discharge curve Va, an initial voltage Vini corresponding to a voltage at the time of full charge and a final voltage Vend are set, and a correction curve for connecting the initial voltage Vini and the final voltage Vend substantially linearly. (Line) Vb is set. Then, the voltage correction table 68 converts the value on the discharge curve Va to the value on the correction curve Vb. The voltage data input to the voltage correction table 68 is configured by the subtractors 62 and 64 and the amplifiers 63 and 66 in the previous stage, and is corrected to a voltage corresponding to the battery output voltage at no load. Therefore, the remaining capacity can be determined.

  A specific battery voltage detection example in FIG. 5 will be described. For example, the voltage difference between the measured voltage Vm1 on the discharge curve Va at the observation point M1 and the measured voltage Vm2 on the discharge curve Va at the observation point M2 is very different. Few. On the other hand, the difference between the measured voltage Vmc1 on the correction curve Vb at the observation point M1 and the measured voltage Vmc2 on the correction curve Vb at the observation point M2 is that the distance between the two observation points M1 and M2 on the correction curve Vb is constant. Then it becomes constant. This means that, for example, when estimating the remaining capacity from the current correction voltage to the end voltage, the calculation becomes easy. Therefore, based on the output of the battery voltage detection unit 60 of this example, the process of determining the remaining battery capacity in the CPU can be accurately performed with a simple process, and an accurate remaining amount display becomes possible. Further, when the battery remaining amount display is performed in a plurality of stages on the display, the voltage value when changing for each stage can be set to the same voltage value in all stages.

  FIG. 6 is a diagram showing the principle of temperature correction according to this example. Assuming that the measured temperature T1 is obtained, it can be obtained from the internal resistance and internal resistance curve y of the battery at that time. At this time, the ratio between the current detection resistor Rd and the internal resistance obtained here is the gain G in the formula [4], which is indicated by the set gain G1. By using the gain table so that the gain can be directly obtained in this way, the processing is simplified. Further, by using the voltage correction curve x from the same measured temperature T1, the temperature characteristic of the discharge curve can be corrected. The correction curve Vb shown in FIG. 5 is prepared on the memory as a plurality of pages in a temperature range assumed in advance. Then, the setting page P1 of the voltage correction table 68 is obtained by using the voltage correction curve x from the measured temperature T1. By applying this as an upper address of a memory used as a voltage correction table, for example, a page can be selected.

  As described above, according to this example, based on the detection of the voltage across the current detection resistor, the voltage corresponding to the battery output voltage at no load is detected (estimated), and the detected voltage is converted into a voltage. Since the voltage is converted into a linear discharge characteristic voltage on the table, it is possible to easily perform accurate determination of the remaining amount when displaying the remaining amount of battery necessary for the cellular phone. That is, on the CPU side, the remaining amount can be easily and accurately determined from the supplied voltage data, and the processing load on the CPU side for accurately determining the remaining amount can be reduced. In particular, in the case of this example, the correction process based on the temperature characteristic can be performed without using the CPU at all, so that the CPU processing load can be reduced from this point as well, and accurate detection without the influence of the temperature characteristic is easy. It has the effect that can be done.

  In the description so far, it has been described that the remaining battery level is displayed on the display in a plurality of stages of about 3 to 4 based on the detected remaining battery level. Since it is possible to detect the amount, it is possible to easily display the remaining battery level as a percentage, for example.

  In the above-described embodiment, the present invention is applied to the process of detecting and displaying the remaining amount of the battery as the power source built in the mobile phone, but the present invention is also applied to various electronic devices in which other batteries can be mounted as the power source. Of course, the above process is applicable. Also, at least a part of the remaining battery level detection function for executing the processing of the present invention is converted into software, and the softwareized program is mounted on a data processing device such as a personal computer device, so that the same remaining battery level detection process is performed. May be performed. The program installed in the data processing device such as the personal computer device may be distributed via various recording (storage) media such as an optical disk and a memory card, or distributed via communication means such as the Internet. Also good.

It is the block diagram which showed the apparatus structural example by one embodiment of this invention. It is explanatory drawing which showed the example of observation by one embodiment of this invention. It is the block diagram which showed the example of a detection structure by one embodiment of this invention. It is explanatory drawing which showed the example of the MONOS structure. It is the characteristic view which showed the example of the voltage correction principle by one embodiment of this invention. It is the characteristic view which showed the example of the temperature correction principle by one embodiment of this invention. It is explanatory drawing which showed the structural example of the radio telephone system. It is explanatory drawing which showed the example of observation of a battery voltage. It is explanatory drawing which showed the voltage detection example in the case of performing the communication process of the conventional TDMA synchronous type. It is the characteristic view which showed the example of the conventional voltage correction principle. It is the circuit diagram which showed the example of the conventional voltage detection structure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 30 ... Central control unit (CPU), 36 ... Display, 50 ... Power supply, 51 ... Battery, 52 ... Thermistor, 59 ... Load, 60 ... Battery voltage detection part, 63 ... Gain variable amplifier, 66 ... Amplifier, 67 ... Analog / Digital converter 68 ... Voltage correction table 69 ... Output register 73 ... Analog / digital converter 74 ... Register 75 ... Temperature correction table

Claims (7)

A voltage detection method for detecting an output voltage of a power source constituted by a battery,
The load current in the internal resistance of the power supply is amplified by amplifying the voltage between two terminals of a current detection resistor that is connected in series between the power supply and the load and detects a load current flowing through the load. Variable gain amplification processing to obtain the voltage drop value by
Gain control value conversion processing for converting a voltage detected based on the temperature of the power source into a gain control value of the gain variable amplification processing by a gain control value conversion table;
An output voltage detection process for correcting the output voltage of the battery according to the obtained voltage drop value;
A voltage detection method for performing a voltage correction process for correcting the output voltage detected in the voltage detection process, based on an output voltage conversion table for correcting the discharge characteristics of the battery substantially linearly. A voltage detection device for detecting an output voltage of a power source constituted by a battery,
A current detection resistor connected in series between the power source and the load to detect a load current flowing in the load;
Gain variable amplification means for obtaining a voltage drop value in the internal resistance by amplifying the voltage between the two terminals of the current detection resistor;
A gain control value conversion table for converting a voltage detected based on the temperature of the power source into a gain control value of the gain variable amplification means;
A voltage detecting means for obtaining an output voltage of the battery corrected by the voltage drop value,
A voltage detection device comprising: voltage correction means for correcting the output voltage detected by the voltage detection means based on an output voltage conversion table for correcting the discharge characteristics of the battery substantially linearly. The voltage detection device according to claim 2 ,
The output voltage conversion table is configured as a memory having a MONOS structure, and is configured on the same integrated circuit as an analog circuit configuring the voltage detection unit and the voltage correction unit. An electronic device to which power is supplied from a power source configured by a battery,
A current detection resistor connected in series between the power source and the load to detect a load current flowing in the load;
Gain variable amplification means for amplifying a voltage between two terminals of the current detection resistor to obtain a voltage drop value in the internal resistor;
A gain control value conversion table for converting a voltage detected based on the temperature of the power source into a gain control value of the gain variable amplification means;
A voltage detecting means for obtaining an output voltage of the battery corrected by the voltage drop value,
An electronic apparatus comprising: a voltage correction unit that corrects an output voltage detected by the voltage detection unit based on an output voltage conversion table that corrects the discharge characteristics of the battery substantially linearly. The electronic device according to claim 4 ,
The output voltage conversion table is an electronic device configured as a memory having a MONOS structure and configured on the same integrated circuit as an analog circuit constituting the voltage detection means and the voltage correction means. The electronic device according to claim 4 or 5 ,
An electronic apparatus comprising: a remaining capacity calculating unit that calculates a remaining capacity of the battery based on the output voltage corrected by the voltage correcting unit. The electronic apparatus according to claim 6 .
An electronic apparatus comprising display means for displaying the remaining capacity of the battery calculated by the remaining capacity calculation means.

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