JP2004096960A - Backup battery charge circuit for portable apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backup battery charge circuit for a portable apparatus capable of extending a data hold time in a backup operation. <P>SOLUTION: The backup battery charge boosting circuit 6 is operated after a power circuit 2 is turned off by a power circuit battery-voltage detection circuit 3, voltages are constantly fed to a backup memory 16 and a clock function 17, and a backup secondary battery 18 is charged. When a battery voltage of a main battery 1 comparatively drops, the backup battery charge boosting circuit 6 is turned off, and from the time of the drop, the backup memory 16 and the clock function 17 are driven by the backup operation of the backup secondary battery 18. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a backup battery charging circuit for a portable device, and more particularly to a circuit for charging a backup secondary battery used in a portable device.
[0002]
[Prior art]
In recent years, mobile phones have become more sophisticated and multi-functional in order to browse the Internet, send and receive e-mails, acquire still images, colorize liquid crystal screens, etc. I have.
[0003]
As a result, the capacity of the battery pack attached to the mobile phone has been increasing, but when the battery runs short, the retention time of the data memory for holding the phonebook, personal data, clock data, etc. A backup circuit for lengthening the time is also required.
[0004]
Recently, some mobile devices such as mobile phones have a built-in main battery, and in many cases, the battery is not removed. Therefore, even if the main battery becomes low voltage and communication becomes impossible, it is necessary to generate a voltage for retaining data, so a backup secondary battery is used.
[0005]
Conventionally, in a portable device such as a cellular phone, as shown in FIG. 5, a main battery 1, a power supply circuit 2, a battery voltage detection circuit 3 for a power supply circuit, an antenna 8, a wireless transmission / reception unit 9, a baseband A processing unit 10, a transmitter / receiver 11, a CPU (central processing unit) 12, a data input unit 13, a display unit 14, a diode 15, a backup memory 16, a clock function 17, and a backup , And a current limiting resistor 19.
[0006]
In the above portable device, ON / OFF control of the power supply circuit 2 is collectively performed by the battery voltage detection circuit 3 for the power supply circuit. Therefore, when the voltage of the main battery 1 decreases, the power supply circuit 2 is turned off by the power supply circuit battery voltage detection circuit 3, and the backup memory 16 and the clock function 17 must be driven by the backup secondary battery 18. .
[0007]
As described above, in a portable device such as a mobile phone, in addition to the main battery 1, a secondary battery 18 for backup or a secondary power supply for supplying power to a standby circuit configuration during a standby mode is mounted. (For example, see Patent Documents 1 and 2).
[0008]
[Patent Document 1]
JP-A-11-206030 [Patent Document 2]
JP 2001-505399 A
[Problems to be solved by the invention]
In the above-described conventional portable device, since the power supply is turned on / off collectively by the battery voltage detecting means, when the main battery voltage decreases, the power supply circuit is turned off by the battery voltage detecting means and the backup memory or The clock function must be driven by a backup secondary battery.
[0010]
However, as shown in FIG. 6, in the conventional portable device, the power supply circuit is turned off at the detection time t2 of the detection voltage "Vet1-", the charging of the backup secondary battery is stopped, and the backup operation is started. Therefore, the data retention time during the backup operation is determined by the time that the backup secondary battery has been charged up to that time.
[0011]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a backup battery charging circuit for a portable device capable of solving the above-mentioned problems and extending the data retention time during the backup operation.
[0012]
[Means for Solving the Problems]
A backup battery charging circuit for a portable device according to the present invention is a backup battery charging circuit for a portable device including a main primary battery and a backup secondary battery, wherein the primary battery has a low voltage. Means for detecting, and a circuit for charging the backup secondary battery using the remaining amount of the primary battery when it is detected that the primary battery has reached the low voltage.
[0013]
That is, the backup battery charging circuit of the portable device of the present invention uses a booster circuit by utilizing the remaining amount of the primary battery even in a portable communication device such as a mobile phone, even if the main battery pack becomes low voltage. By charging the secondary battery for backup, the data retention time during the backup operation is extended.
[0014]
More specifically, in the backup battery charging circuit of the portable device of the present invention, when a main battery is connected as much as possible by using a converter or the like for a low-voltage battery, the voltage is used. It is configured to be used for memory backup.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a portable device according to one embodiment of the present invention. In FIG. 1, a portable device according to one embodiment of the present invention includes a main battery 1, a power supply circuit 2, a battery voltage detection circuit 3 for a power supply circuit, a battery voltage detection circuit 4 for a booster circuit, and an AND gate 5. A booster circuit 6 for charging a backup battery, diodes 7 and 15, an antenna 8, a wireless transceiver 9, a baseband processor 10, a transmitter / receiver 11, and a CPU (central processing unit) 12. , A data input unit 13, a display unit 14, a backup memory 16, a clock function 17, a backup secondary battery 18, and a current limiting resistor 19.
[0016]
The power supply circuit 2 supplies a voltage to each device, and the power supply circuit battery voltage detection circuit 3 detects a battery voltage and performs ON / OFF control on the power supply circuit 2. The booster circuit battery voltage detection circuit 4 includes a charge pump or the like that performs ON / OFF control of the backup battery charging booster circuit 6.
[0017]
The AND gate 5 performs an AND operation on the signal of the battery voltage detecting circuit 3 for the power supply circuit and the signal of the battery voltage detecting circuit 4 for the boosting circuit and outputs the result to the backup battery charging boosting circuit 6. The diode 7 is arranged to prevent backflow to the backup battery charging booster circuit 6, and the diode 15 is arranged to prevent backflow to the power supply circuit 2.
[0018]
The CPU 12 performs data processing, and the data input unit 13 is a keyboard or the like for inputting data from outside. The backup memory 16 is, for example, an SRAM (Static Random Access Memory) for retaining data during a backup operation. The clock function 17 is a real-time clock or the like that counts time even during the backup operation.
[0019]
The power supply circuit 2 includes a stabilized power supply REG (regulator) 21 such as a series regulator that supplies a voltage to a transmission / reception control unit such as the wireless transmission / reception unit 9 and the inverse band processing unit 10, and a stabilized power supply REG 22 that supplies power to the CPU 12. And a REG 23 for charging the backup secondary battery 18 and supplying power to the clock function 17 and the backup memory 16.
[0020]
In a conventional portable device, as shown in FIG. 5, the ON / OFF of the power supply circuit 2 is collectively controlled by a battery voltage detection circuit 3 for a power supply circuit. The power supply circuit 2 is turned off by the circuit battery voltage detection circuit 3, and the backup memory 16 and the clock function 17 must be driven by the backup secondary battery 18.
[0021]
In this embodiment, after the power supply circuit 2 is turned off by the power supply circuit battery voltage detection circuit 3, the backup battery charging booster circuit 6 is operated to always supply a voltage to the backup memory 16 and the clock function 17, and Of the secondary battery 18 is charged. When the battery voltage of the main battery 1 becomes considerably low, the backup battery charging step-up circuit 6 is turned off, and the backup memory 16 and the clock function 17 are driven by the backup operation from this point. Therefore, in the present embodiment, the data retention time in the backup memory 16 is lengthened by the time during which charging is performed by the backup battery charging booster circuit 6.
[0022]
FIG. 2 is a timing chart showing the operation of the portable device according to one embodiment of the present invention. A backup operation in a portable device according to an embodiment of the present invention will be described with reference to FIGS. In FIG. 2, the release voltage of the battery voltage detection circuit 3 for the power supply circuit is “Vdet1 +”, the detection voltage is “Vdet1-”, and the release voltage of the battery voltage detection circuit 4 for the booster circuit is “Vdet2 +”. Assuming that the voltage is “Vdet2−”, the relationship is “Vdet1 + ≧ Vdet2 +> Vdet1 → Vdet2−”.
[0023]
The power supply circuit 2 is turned on by the power supply circuit battery voltage detection circuit 3 when the release voltage exceeds “Vdet1 +”, and is turned off by the power supply circuit battery voltage detection circuit 3 when the detection voltage falls below “Vdet1-”.
[0024]
Similarly to the power supply circuit 2, when the release voltage exceeds “Vdet2 +”, the backup battery charging booster circuit 6 is also turned on by the booster battery voltage detection circuit 4, and the detected voltage becomes “Vdet2-”. When the voltage falls below the threshold voltage, the voltage is turned off by the battery voltage detection circuit 4 for the booster circuit. At this time, an AND operation is performed by the AND gate 5 on the ON / OFF signal from the battery voltage detection circuit 3 for the power supply circuit and the ON / OFF signal from the battery voltage detection circuit 4 for the booster circuit. The booster circuit 6 is controlled. Thus, in the present embodiment, the REG 23 for charging and the boosting circuit 6 for charging the backup battery can be operated exclusively.
[0025]
When the main battery 1 is connected to the device or when the battery voltage rises due to charging and the release voltage exceeds “Vdet1 +” at time t1, the REG 23 is turned on to charge the secondary battery 18 for backup. Begins. At this time, if “Vdet1 +> Vdet2 +”, the backup battery charging booster circuit 6 operates first at t0, but switches to REG23 at “Vdet1 +”. At this time, even if the voltage drops momentarily, no backflow occurs because of the presence of the diode 15 and the diode 7.
[0026]
Conversely, if the battery voltage drops and “Vdet1−” is detected at time t2, an OFF signal is sent from the battery voltage detection circuit 3 for the power supply circuit to the power supply circuit 2 and transmitted to each device. Supply of the voltage stops. At this time, the backup battery charging step-up circuit 6 is turned on when the power supply circuit 2 is turned off by the AND gate 5, and if the backup secondary battery 18 is used, the charging state is continuously performed. When the battery voltage drops, "Vdet2-" is detected at time t3, and the backup operation by the backup secondary battery 18 is performed for the first time at that time.
[0027]
In the conventional portable device, as shown in FIG. 6, the power supply circuit 2 is turned off at the detection time t2 of "Vdet1-", so that the charging of the backup secondary battery 18 is stopped, and the operation shifts to the backup operation. I do. However, in the present embodiment, the backup retention time can be extended by the time of t3-t2.
[0028]
FIG. 3 is a block diagram showing a configuration of a portable device according to another embodiment of the present invention. Referring to FIG. 3, a portable device according to another embodiment of the present invention further includes a backup battery voltage detection circuit 20, and controls ON / OFF of the backup battery charging booster circuit 6 according to the state of the voltage of the backup secondary battery 18. Except for this, the configuration is the same as the configuration of the portable device according to the embodiment of the present invention shown in FIG. 1, and the same components are denoted by the same reference numerals. The operation of the same component is the same as that of the embodiment of the present invention.
[0029]
In one embodiment of the present invention, the backup battery charging booster circuit 6 is turned on after the power supply circuit 2 is turned off, and the backup secondary battery 18 is constantly charged. In the example, the backup operation is performed after the power supply circuit 2 is turned off. When the voltage of the backup secondary battery 18 is monitored by the backup battery voltage detection circuit 20 and the voltage drops to a certain battery voltage level due to discharge, The backup battery charging booster circuit 6 is operated to charge the backup secondary battery 18.
[0030]
As a result, in the present embodiment, the consumed current can be reduced at all times compared to when the backup battery charging booster circuit 6 is operated, and therefore, the drop in the battery voltage of the main battery 1 is small. Become.
[0031]
FIG. 4 is a timing chart showing the operation of a portable device according to another embodiment of the present invention. A backup operation in a portable device according to another embodiment of the present invention will be described with reference to FIGS. In FIG. 4, the backup battery voltage detection circuit 20 outputs a signal for turning off the backup battery charging booster circuit 6 when the release voltage exceeds “Vdet3 +”, and when the detection voltage falls below “Vdet3-”, A signal for turning on the backup battery charging booster circuit 6 is output.
[0032]
When the voltage of the main battery 1 drops, first, “Vdet1−” is detected at time t1, and the voltage supply by the REG 23 is turned off. At this time, in one embodiment of the present invention, the backup battery charging booster circuit 6 operates, but in this embodiment, if the backup secondary battery 18 is sufficiently charged, that is, if the backup battery voltage is detected. If the battery voltage of the backup secondary battery 18 in the circuit 20 is higher than "Vdet3 +", the backup battery charging step-up circuit 6 is not operated to perform the backup operation.
[0033]
When power is consumed in the backup memory 16 and the clock function 17 by the backup operation, the voltage of the backup secondary battery 18 drops, and when the voltage falls below “Vdet3-” at time t 2, the backup battery voltage detection circuit 20 Sends a signal to the backup battery charging booster circuit 6, the backup battery charging booster circuit 6 starts operating, and the backup secondary battery 18 is charged.
[0034]
By the charging operation, the battery voltage of the backup secondary battery 18 increases. If the battery voltage of the backup secondary battery 18 exceeds “Vdet3 +” at time t3, the backup battery charging booster circuit 6 is turned off. Then, the operation shifts to the backup operation again.
[0035]
Further, when the voltage of the backup secondary battery 18 drops again and falls below “Vdet3-”, the same operation as described above is performed, and the operation is repeated until the battery voltage of the main battery 1 falls below “Vdet2-”.
[0036]
In this case, in the present embodiment, the OFF control of the backup battery charging step-up circuit 6 is performed when the release voltage exceeds “Vdet3 +”. However, if the backup secondary battery 18 is set to a state close to full charge, For example, the voltage is monitored at both ends of the current limiting resistor 19, and when the potential difference becomes 0, that is, when it is detected that the current flowing into the backup secondary battery 18 becomes 0, the backup battery charging is performed. The booster circuit 6 may be turned off.
[0037]
Thus, according to the present invention, the data retention time during the backup operation can be lengthened. Further, in this embodiment, the charging of the backup secondary battery can be continued even if other power supply circuits are turned off.
[0038]
Further, in the present invention, since the backup battery charging step-up circuit 6 supplies a voltage to the backup secondary battery 18, the main battery 1 can be used up to a low voltage.
[0039]
Furthermore, in the present invention, since the backup battery charging step-up circuit 6 is independent of the power supply circuit 2, it can be turned on / off even during the operation of the main battery 1 by changing the control logic. .
[0040]
【The invention's effect】
As described above, the present invention provides a primary battery and a backup battery charging circuit for a portable device including a backup secondary battery, which are used when the primary battery is detected to have a low voltage. By charging the backup secondary battery with the booster circuit using the remaining amount of the battery, the effect of increasing the data retention time during the backup operation can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a portable device according to an embodiment of the present invention.
FIG. 2 is a timing chart showing an operation of the portable device according to one embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of a portable device according to another embodiment of the present invention.
FIG. 4 is a timing chart showing an operation of a portable device according to another embodiment of the present invention.
FIG. 5 is a block diagram showing a configuration of a portable device according to a conventional example.
FIG. 6 is a timing chart showing an operation of a portable device according to a conventional example.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 Main battery 2 Power supply circuit 3 Battery voltage detection circuit for power supply circuit 4 Battery voltage detection circuit for booster circuit 5 AND gate 6 Backup battery charging booster circuit 7, 15 Diode 8 Antenna 9 Wireless transceiver 10 Baseband processor 11 Transmission Handset / receiver 12 CPU
13 Data Input Unit 14 Display Unit 16 Backup Memory 17 Clock Function 18 Backup Secondary Battery 19 Current Limiting Resistor 20 Backup Battery Voltage Detection Circuits 21 and 22 Stabilized Power Supply REG
23 REG

Claims (6)

A backup battery charging circuit for a portable device including a main primary battery and a backup secondary battery, wherein the unit detects that the primary battery has become low voltage, and the primary battery has the low battery level. A circuit for charging the backup secondary battery using the remaining amount of the primary battery when the voltage is detected. The circuit for charging the backup secondary battery is a booster circuit that boosts the remaining amount of the primary battery to a charging voltage of the backup secondary battery and charges the backup secondary battery. The backup battery charging circuit according to claim 1, wherein: 3. The backup battery charging circuit according to claim 2, wherein a circuit for preventing backflow to the booster circuit is provided between the booster circuit and the backup secondary battery. When the primary battery has reached a preset threshold value lower than the low voltage, the charging of the backup secondary battery by the booster circuit is stopped, and the backup operation by the backup secondary battery is started. 4. The backup battery charging circuit according to claim 2, wherein the backup battery charging circuit shifts. Means for detecting the voltage of the backup secondary battery, wherein when the voltage of the backup secondary battery drops to a predetermined battery voltage level set by discharging, the booster circuit causes the booster circuit to detect the backup secondary battery. The backup battery charging circuit according to any one of claims 2 to 4, wherein the secondary battery is charged. 6. The charging of the backup secondary battery by the booster circuit is stopped when the battery voltage of the backup secondary battery increases by charging and exceeds a preset battery voltage level. A backup battery charging circuit as described.

Images