JPH09294330A - Power circuit of information communication terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of a secondary battery due to overcharging, by serially connecting a specified resistor to the secondary battery and judging that the secondary battery is fully charged when the voltage across the resistor becomes nearly zero, and installing a circuit for stopping the charging of the secondary battery. SOLUTION: When the capacity of a main battery 1 is full and is connected, a backup battery 2 is charged and a selector 5 selects an A side and a power circuit 3 for stabilization supplies power to a clock function implementation means 6 and SRAM 7. When the capacity of the main battery 1 decreases or is disconnected, the selector 5 selects a B side and the backup battery 20 supplies power to the clock function implementation means 6 and the SRAM 7. At that time, a transistor 12 is turned off since transistor 14, 15 are turned off. By this method, the charging of the secondary battery 2 can be stopped when the battery 2 is fully charged, and thereby preventing overcharging.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit having a battery for backup.

[0002]

2. Description of the Related Art In information communication terminals such as mobile phones, those having a clock function or a message recording function are increasing. Since these information communication terminals place importance on mobility and supply power with a battery, it is an important issue to prolong the duration of the operation. However, with regard to the clock function and the message recording function, it is necessary to back up for a predetermined time even when the battery voltage drops or when the battery is removed. Therefore, these backups are realized by using a secondary battery.

A related circuit for backing up a memory circuit or the like using a secondary battery is described in "Technology Editing Department", "Battery Utilization Handbook", CQ Publisher, pp.
119-pp122, January 1994.

[0004]

The first problem to be solved by the present invention is to prevent the overcharge and overdischarge of the secondary battery for backup, which leads to the extension of its life. In the present invention, the deterioration of the secondary battery due to overcharging is prevented by detecting the fully charged state and stopping the charging.

The second problem is to supply a power supply circuit which does not affect the charging current even if an abnormal charging current flows, and does not affect the current supplied to the load. Especially.

The third problem is that the backup battery has a life, so that the user is informed of the life of the backup battery by knowing the standard of the replacement time.

[0007]

[Means for Solving the Problem] A means for solving the first problem is to connect a predetermined resistor in series with a secondary battery, and fully charge the battery at a place where the voltage generated at both ends becomes almost zero. And to provide a circuit for stopping the charging.
After the charging is stopped, the battery is discharged with a leak current. When the output voltage of the secondary battery drops to a predetermined voltage due to the discharge caused by the leakage current, the charging is restarted. In this way, overcharging can be prevented.

A means for solving the second problem is to construct a power supply circuit for separately supplying the charging current of the secondary battery and the current supplied to the load.

The means for solving the third problem is to utilize the fact that the voltage at the load end differs between the current supply from the main power supply and the current supply from the backup battery, and By measuring the supply time from the backup battery, the life of the battery is predicted and means for notifying the user is provided. It is also possible to predict the supply time of the backup battery from the terminal voltage of the backup battery when the power supply from the main power supply is restarted.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a block diagram of one embodiment of the present invention. In FIG. 1, 1 is a main battery, 2 is a backup battery, 3 and 4 are stabilized power supply circuits, 5 is a selection means, 6 is a clock function realizing means, 7 is an SRAM, 8 is a CPU, and 9 is a full charge of the backup battery 2. Detecting means, 10 is battery voltage detecting means for the backup battery 2, 11 is a capacitor, and 12 to 1
6 is a transistor, and 17 to 19 are resistors.

Power switch of the information communication terminal (not shown)
When is pressed, the information is input to the CPU 8 and the CP
A signal for turning on the transistor 16 is output from U8.

On the other hand, the battery voltage of the backup battery 2 is
When the battery voltage detection means 10 detects that the voltage has not reached the predetermined voltage, the backup battery 2 is charged from the main battery 1 via the stabilized power supply circuit 3 and the transistor 12. Furthermore, the charge state of the backup battery 2 is detected by the full charge detecting means 9. For example, it is determined that the battery is fully charged when the voltage drop due to the charging current flowing through the resistor 17 becomes almost zero. Further, by detecting the terminal voltage of the backup battery 2, it is possible to determine that the state in which the voltage has reached the predetermined voltage is fully charged. When it is determined that the backup battery 2 is fully charged, the transistors 15 and 12 are turned off to stop charging. After that, the transistor 12 and the selection means 5 are discharged.
Is the leakage current of When the battery voltage of the backup battery drops below the predetermined voltage due to this discharge, the battery voltage detection means 10 turns on the transistors 14 and 12, and the charging is restarted.

When the main battery 1 has a sufficient capacity and is attached, the backup battery 2 is charged as described above, the selecting means 5 selects the A side as shown, and the stabilizing power supply circuit 3 is selected. Then, power is supplied to the clock function realizing means 6 and the SRAM 7.

When the capacity of the main battery 1 decreases,
Alternatively, when removed, the selecting means 5 selects the B side, and the backup battery 2 to the clock function realizing means 6, SR
Supply power to AM7. At that time, the transistor 12
Is turned off because the transistors 14 and 15 are turned off.

In this way, when the backup battery 2 is fully charged, its charging can be stopped, so that overcharging can be prevented.

By separating the charging current and the load current when the backup battery 2 is charged, the influence of the abnormal charging current on the loads 6 and 7 and the influence of the abnormal load current on the backup battery 2 are eliminated. be able to.

The timepiece function realizing means 6 comprises an oscillator for forming a reference signal and its counter, and measures one second intervals from its oscillation frequency, and further one minute and one hour to measure the timepiece. It realizes a function. The clock function is realized and displayed on the display 20 with the time set by the input from the numeric keypad 21 of the information communication terminal as the start time.

With regard to the SRAM 7, voices on the transmitting side and the receiving side are stored by a mobile phone or the like to realize a memo function. This function will be briefly described with reference to FIGS.

FIG. 2 is a block diagram for realizing a memo function in an analog type mobile phone. 31 is a receiver, 32 is a microphone, 33 is a selection means, 34 is a DA converter, 35, 3
6 is an AD converter, 37 is a signal processing unit, 38 is a high frequency unit,
39 is an antenna.

In this mobile phone, the voice on the transmitting side input from the microphone 32 is processed by the signal processing unit 37, converted into a high frequency signal by the high frequency unit 38, and transmitted from the antenna 39. At this time, the voice from the microphone 32 is converted into a digital signal by the AD converter 36, and the signal is stored in the SRAM 7. Therefore, in order to reproduce the stored voice, the data stored in the SRAM 7 is transferred to the DA converter 34 and converted into an analog signal, and then the selecting means 33 selects the A side as shown in the drawing and the receiver 31 outputs it. The memorized voice is output.

On the other hand, as for the voice on the receiving side, the signal received by the antenna 39 and the high frequency section 38 is converted into a voice signal by the signal processing section 37, and the signal is selected by the selecting means 33 on the B side. Is output from the receiver 31. The voice signal received at this time is converted into a digital signal by the AD converter 35, and the signal is stored in the SRAM 7. Therefore, in order to reproduce the stored voice, the SRAM 7
After transferring the stored data to the DA converter 34 and converting it to an analog signal, the selecting unit 33 selects the A side as shown in the figure and outputs the stored voice from the receiver 31.

Next, the implementation of the memo function in the digital mobile phone will be described with reference to FIG.

FIG. 3 is a block diagram for realizing a memo function in a digital mobile phone. 40 is a DA converter, 4
1 is an AD converter, 42 is a selection means, 43 is a signal processing unit,
Reference numeral 44 is a modulation / demodulation unit, and 45 is a high frequency unit.

In this mobile phone, the voice on the transmitting side input from the microphone 32 is converted into a digital signal by the AD converter 41, subjected to predetermined signal processing by the signal processing unit 43, and then by the modulation / demodulation unit 44. The signal is modulated and converted into a high frequency signal by the high frequency unit 45 and transmitted from the antenna 39. At this time, the signal input to the signal processing unit 43 or the digital signal being processed is stored in the SRAM 7. Therefore,
In order to reproduce the stored voice, the data stored in the SRAM 7 is selected by the selecting means 42 (selecting the B side).
After transferring to the DA converter 40 and converting into an analog signal,
The stored voice is output from the receiver 31.

On the other hand, for the voice on the receiving side, the signal received by the antenna 39 and the high frequency section 45 is demodulated by the modulation / demodulation section 44 and then converted into a voice signal (digital signal) by the signal processing section 43. The signal is selected by the selecting means 42 on the A side, and DA
The received voice is output from the receiver 31 by being converted into an analog signal by the converter 40. At this time, the signal processing unit 4
The received digital signal processed in step 3 is stored in the SRAM 7 at an appropriate stage. Therefore, in order to reproduce the stored voice, the data stored in the SRAM 7 is transferred to the DA converter 40 via the selection means 42 (selecting the B side) and converted into an analog signal, and then the receiver 3 is used.
The stored voice is output from 1.

The above is the outline of the memo function.
By storing the voice from No. 1, by transmitting the stored voice to a predetermined telephone number at a predetermined time, it is possible to automatically transmit a predetermined message.

Next, a specific circuit of the present invention will be described with reference to FIGS.

FIG. 4 is a circuit diagram of the present invention, and FIG. 5 is an explanatory diagram of its operation. 51, 52 are comparators, 5
3, 54 are transistors, 55 are diodes, 56 to 5
Reference numeral 8 is a resistor, 59 is an oscillator, and 60 is a counter means.

In the circuit diagram of FIG. 4, the full charge detecting means 9 of FIG. 1 is realized by the comparator 51. In this circuit, full charge is detected by detecting that the charging current flowing through the resistor 17 becomes almost zero when fully charged. The charging current flows from the transistor 12 to the backup battery 2. The terminal voltage of the backup battery 2 increases with the charging time as shown in FIG. Therefore, the voltage across the resistor 17 decreases with time. That is, in the comparator 51, the negative input increases with time. Therefore, until the minus input reaches a predetermined level, the output signal thereof becomes high level, the transistors 15 and 12 are turned on, and the charging of the backup battery 2 is maintained. Further, when charging progresses and the terminal voltage of the backup battery 2 rises to reach a predetermined level,
The output signal of the comparator 51 is inverted to the low level, the transistor 15 is turned off, and the charging is stopped. After that, the backup battery 2 is discharged only by the leak current flowing from the transistor 12 to the transistor 14 or 15. During this discharging, the direction of current flow is opposite to that during charging, so the output of the comparator 51 remains low level and is not inverted to high level. However, if the discharge is continued by the leak current, the voltage at the point a in the figure decreases. Then, the voltage is detected by the battery voltage detecting means 10. In this embodiment, the battery voltage detection means 10 is realized by the comparator 52. The voltage at point a is calculated by the comparator 5
2 is input to the minus input, and the voltage determined by the resistors 57 and 58 is input to the plus input for comparison. That is, when the negative input drops to a predetermined voltage, the output of the comparator 52 is inverted to a high level, and the transistor 12 is turned on via the transistor 14 to turn on the main battery 1.
The backup battery 2 is charged from.

When the output voltage of the main battery 1 drops or is removed, the output voltage of the stabilized power supply circuit 3 drops and drops below the output voltage of the backup battery 2. Backup is realized.

Further, the selection means 5 in FIG.
3, 54, diode 55, and resistor 56. Here, when the main battery 1 outputs a predetermined voltage, the transistor 53 is turned on and the clock function realizing means 6,
Power is supplied to the SRAM 7. At this time diode 5
By providing 5, the current is not supplied from the backup battery 2 to the load (clock function realizing means 6, SRAM 7). Therefore, at this time, the backup battery 2
It is only charged from the main battery 1. Further, when the output voltage of the main battery 1 drops or is removed, backup is realized. At this time, the output current of the backup battery 2 is supplied to the load by turning off the transistors 14, 15, 16 and 54. In this way, the main battery 1 or the backup battery 2 is selected as the source of the current supplied to the load.

In this embodiment, the clock function realizing means 6 is realized by the oscillator 59 and the counter means 60. This is achieved by measuring the frequency of the signal oscillated by the oscillator 59 with the counter means 60 for 1 second, 1 second.
Realize the clock function by measuring minutes and 1 hour. Here, the counter means 60 of the clock function realizing means 6 is replaced by the CPU 8
However, the counter means can be realized as a part of the CPU 8. In that case, what is backed up by the backup battery 2 only needs to back up the portion for realizing the clock function.

Another embodiment of the present invention will be described with reference to FIG.

FIG. 6 is a circuit diagram of the second embodiment of the present invention. In FIG. 6, 65 is a temperature detecting means, 66 to 68 are resistors, 6
Reference numeral 9 is a comparator, and 70 is an AND gate.

In FIG. 6, the temperature rise of the backup battery 2 is increased by using the temperature detecting means 65 such as a thermistor arranged in the vicinity of the backup battery 2 in addition to the full charge detecting means 9 of FIG. To detect overcharge. In the charged state, the temperature of the backup battery 2 also rises. When the temperature exceeds a predetermined temperature, the resistance value of the temperature detecting means 65 increases, and the output signal of the comparator 69 is inverted and becomes low level. The signal is input to the AND gate 70 to turn off the transistor 12 via the transistor 15. By thus detecting the temperature rise, the accuracy of detecting the overcharged state is increased.

Next, an embodiment of the invention for solving the second problem will be described with reference to FIG.

FIG. 7 is a circuit diagram of the third embodiment of the present invention. In FIG. 7, 76 is a diode and 77 is a transistor.

At the time of charging the backup battery 2, in addition to the charging current, a current is supplied via the diode 76 to the circuits 6 and 7 that require backup. On the other hand, when the voltage of the main battery 1 drops or when the main battery 1 is removed, the transistor 77 is turned off, so the transistor 12 is also turned off. Therefore, current is supplied from the backup battery 2 to the circuits 6 and 7 that require backup through the diode 55. In this way, by separating the charging current and the load current when the backup battery 2 is charged, the influence of the abnormal charging current on the loads 6 and 7 and the backup battery 2 having the abnormal load current
Can have no effect on.

Next, an embodiment of the invention which solves the third problem will be described with reference to FIGS.

FIG. 8 is a circuit diagram of the fourth embodiment of the present invention, and FIG. 9 is an operation explanatory diagram thereof. In FIG. 8, 80 is a comparator, 81 and 82 are resistors, 83 is an AD converter, and 84 is a counter means.

In this embodiment, the load 6 and the load are supplied from the main battery 1 and the load 6 and 7 respectively.
The fact that the voltage applied to 7 changes is used. The counter means 8 detects the voltage change and detects how many times it has occurred.
By counting at 4, the backup battery 2
Estimate the lifespan of. The change in the power supply voltage applied to the loads 6 and 7 is detected by the comparator 80 and the output signal is input to the counter means 84. The power supply for the counter means 84 and the comparator 80 is supplied from the main battery 1, and when the voltage drops or when the main battery 1 is removed, the capacitor 11 backs up for a time that can be counted by the counter means 84 (FIG. 9f). Then, the number of times of the voltage change is counted. It is also possible to store the data of the counter means 84 in the SRAM 7 via the CPU 8. Further, at this time, by detecting the terminal voltage of the backup battery 2 when the main battery 1 is restored, how long the current is supplied from the backup battery 2 can improve the accuracy of life detection. . That is, the terminal voltage of the backup battery 2 when the main battery 1 is restored is A
By converting it into digital data by the D converter 83 and inputting it to the CPU 8, the backup time of the backup battery 2 is estimated and the life is estimated. In this way, the user can be informed of the estimated life of the backup battery 2 by using a display or the like to inform the user of the replacement.

The applicable battery of the present invention can also be applied to a primary battery such as a dry battery.

[0044]

According to the present invention, deterioration of the secondary battery due to overcharging can be prevented by detecting the fully charged state and stopping the charging.

According to the present invention, it is possible to realize a power supply circuit that does not affect the current supplied to the load even if an abnormal charging current flows, and does not affect the charging current even when an abnormal load current flows.

In the present invention, it is possible to know the standard of the replacement time of the backup battery, and to inform the user of the life of the backup battery.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram for realizing a memo function on an analog mobile phone.

FIG. 3 is a block diagram for realizing a memo function on a digital mobile phone.

FIG. 4 is a circuit diagram of the present invention.

FIG. 5 is an explanatory diagram of the operation in FIG. 4;

FIG. 6 is a circuit diagram of a second embodiment of the present invention.

FIG. 7 is a circuit diagram of a third embodiment of the present invention.

FIG. 8 is a circuit diagram of a fourth embodiment of the present invention.

9 is an explanatory diagram of the operation of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Main battery, 2 ... Backup battery, 3, 4 ... Stabilized power supply circuit, 5 ... Selection means, 6 ... Clock function realization means, 7 ... SRAM, 8 ... CPU, 9 ... Full charge detection means, 10 ... Battery voltage Detection means, 11 ... Capacitor, 12-16 ... Transistor, 17-19 ... Resistor.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H02J 7/34 H02J 9/06 503A 9/06 503 G06F 1/00 335C (72) Inventor Hiroshi Yamamoto Yokohama, Kanagawa Prefecture Hitachi Image Information Systems Co., Ltd. 292 Yoshida-cho, Totsuka-ku, Yokohama

Claims (6)

[Claims] 1. In a battery-driven information communication terminal, a secondary battery for backing up a predetermined circuit, control means for turning on / off charging from the battery to the secondary battery, and output of the battery. And a selecting means for selecting the output of the secondary battery and supplying the selected output to the predetermined circuit, the power supply circuit of the information communication terminal. 2. In an information communication terminal driven by a battery, a secondary battery for backing up a predetermined circuit, a charge state detecting means for detecting a charge state of the secondary battery, and a battery voltage of the secondary battery are provided. Battery voltage detecting means for detecting,
Depending on the outputs of the charging state detecting means and the battery voltage detecting means, the charging of the secondary battery from the battery is turned on / off.
A power supply circuit for an information communication terminal, comprising: control means for turning off, the battery output, and a selection means for selecting the secondary battery output and supplying the selected output to the predetermined circuit. 3. A power supply circuit of an information communication terminal, wherein the charge state detecting means of claim 2 is a full charge detecting means. 4. A power supply circuit of an information communication terminal, wherein the charge state detecting means of claim 2 is a full charge detecting means and a battery temperature detecting means. 5. In an information communication terminal driven by a battery, a battery for backing up a predetermined circuit, a means for counting the number of times the power supply voltage of the predetermined circuit fluctuates, and a memory for storing an output signal of the counting means. A power supply circuit for an information communication terminal, comprising: 6. The power supply circuit for an information communication terminal according to claim 5, further comprising detection means for detecting the terminal voltage of the backup battery when the battery is restored.