JP2002373037A - Power source controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power source controller, with which the exhaustion of a power source is eliminated and the ON/OFF of the power source is not unexpectedly repeated. SOLUTION: When a power source button SW1 is operated, a start signal is outputted from a power source starting circuit 15 to a DC/DC converter 30 just for prescribed time by a monostable multivibrator MM2. After the voltage of a system power source outputted from the DC/DC converter 30 becomes sufficiently higher than a specified voltage V2 by a delay circuit DL2, a microcomputer 16 is reset and started. The microcomputer 16 outputs an ACT signal and performs power source management by itself. When the power source button SW1 is operated during the use of a digital camera, the system power source is prevented from being turned off within prescribed time by a delay circuit DL1 and within the time, data backup to a memory 35 and the function suppression of a terminal are conducted, afterward a PWCTL signal is made Lo. Then, the system power source is turned off and the power source of the microcomputer 16 itself is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply control device which hardly consumes power when an electronic device is not used and which does not repeat power-on / power-off without permission.

[0002]

2. Description of the Related Art Digital still cameras (digital cameras), digital video cameras, and portable information terminals (PDs)
A), electronic devices such as a mobile phone, a voice memo, and a portable audio player have a clock function and a memory function for storing various settings and are not used (for example, a digital still camera is used for photographing, etc.). Do not do)
For example, if the state continues for 3 minutes or more, the power switch is automatically turned off to provide an automatic power-off function or the like for preventing unnecessary consumption of a power battery (for example, a lithium ion battery or an AA battery). Many.

[0003] Such a function is realized by a microcomputer as is well known. For this reason, even when the power switch is off, the microcomputer always receives a small amount of standby current from the power supply battery. When the power switch is turned on, the microcomputer detects this and starts up, and supplies necessary power to each unit from the power supply circuit.

[0004]

As described above, even when the power switch is turned off, the power battery of the electronic device is consumed. Therefore, it is not only uneconomical but also has a greater problem. That is, when the power switch is turned on while the power battery is considerably depleted, the power supply circuit may not operate sufficiently and the power-off process may need to be performed during the startup of the microcomputer. Since it is very difficult to control the timing of this processing, the microcomputer may hang up and cause a hunting phenomenon in which power-on / power-off is repeated without permission.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In the state where electronic equipment is not used, power consumption is hardly reduced, and power supply control that does not repeatedly repeat power-on / power-off is described. It is intended to provide a device.

[0006]

In order to achieve the above object, a power supply control device according to the present invention comprises a main power supply detecting means for detecting the presence or absence of a main power supply by detecting the voltage or current of a main power supply such as a battery. A signal holding means for holding an ON signal of the power switch for a predetermined time every time the power switch is operated, and starting the power supply circuit while the main power is detected and the ON signal of the power switch is held. It comprises a power supply starting means and a microcomputer which starts up by receiving power supply from a power supply circuit and controls the power supply starting means and the like after the start-up.

The power supply activating means has a first delay means which does not delay when activating the power supply circuit and delays it for a predetermined time when halting the power supply circuit. A voltage detection circuit for detecting an output voltage of the power supply circuit between the power supply circuit and the microcomputer; and a microcomputer when the output voltage of the power supply circuit increases to reach a predetermined voltage. And a second delay means for resetting the microcomputer without delay when the output voltage of the power supply circuit falls below a predetermined voltage. The delay means is controlled by clock means for generating a constant clock pulse.

[0008]

FIG. 1 shows a power supply control device according to a first embodiment of the present invention. In this embodiment, a power supply control device 10 is incorporated in, for example, a digital camera. As the main power supply connected to the power supply control device 10, for example, an AA battery 11 is used. In addition, AC adapter 1
2 can be connected and used. In addition, it is also possible to charge the battery when the AC adapter 12 is connected by using a built-in charging circuit and using, for example, a lithium ion battery or the like instead of the AA battery 11.

The electric contact 13 to which the terminal of the AA battery 11 contacts is connected to a power supply starting circuit 15 and a microcomputer 16 via a main power supply voltage detecting circuit 14. The power supply activation circuit 15 includes one AND circuit 21 and 2
It comprises OR circuits 22 and 23 and a delay circuit DL1. The AND circuit 21 includes the main power supply voltage detection circuit 14 and the O
Each output from the R circuit 22 is input.

The OR circuit 22 is a three-input OR gate. The first input is an ON signal of the power button SW1 input through two monostable multivibrators MM1 and MM2 connected in series. The second input is the A_on signal from the switch SW2 input via the monostable multivibrators MM1 and MM2. The third input is an output signal from the AND circuit 25.

The switch SW2 is a switch that is turned on when the power is automatically started in addition to the operation of the power button SW1. The switch SW2 is turned on when, for example, the AC adapter 12 is connected to control charging of a rechargeable power supply battery (for example, a lithium ion battery) (detection of the connection of the AC adapter 12), remote control, wireless communication (Bluetooth ), Etc., when the wireless receiving module receives a power-on signal by remote operation.

The output from the AND circuit 21 is directly ORed.
The signal is input to one terminal of the circuit 23 and is input to the other terminal of the OR circuit 23 via the delay circuit DL1. As soon as the output Hi from the AND circuit 21 is input to the OR circuit 23, the output from the OR circuit 23, that is, the power control signal (hereinafter referred to as a PWCTL signal) as a control signal from the power supply start-up circuit 15 becomes Hi. , Even if the output from the AND circuit 21 changes to Lo,
The WCTL signal does not immediately change to Lo and remains unchanged at Hi for a predetermined time. When the PWCTL signal becomes Hi,
When the DC / DC converter 30 which is a power supply circuit is activated and the PWCTL signal becomes Lo, the DC / DC converter 30 is stopped. However, the activation of the DC / DC converter 30 is quickly performed by the operation of the delay circuit DL1. Stopping is done slowly.

A system power supply (a main power supply of the AA battery 11, a microcomputer 16, and various parts of a digital camera (a liquid crystal panel as an electronic viewfinder, a photographing lens, a lens barrier, A power supply for actually driving the entire system including a CCD image sensor and a strobe device) is connected to a power supply input terminal of the microcomputer 16 and a system power supply voltage detection circuit 3 via a switch SW3.
2 and each part of the digital camera. When the system power is output from the DC / DC converter 30, the switch SW3 is turned on regardless of the voltage level, and after the microcomputer 16 is started, the switch SW3 is turned on.
ON / OFF is controlled by the microcomputer 16.

The system power supply voltage detection circuit 32 has a DC /
When the voltage of the system power supply input from the DC converter 30 reaches the minimum specified voltage V2 for driving the entire system, the Hi signal is directly input to one input terminal of the AND circuit 33 and the other input terminal is input. The terminal is a delay circuit DL
2 to input the information. An output from the AND circuit 33 is supplied to a reset terminal (RE) of the microcomputer 16.
SET) and one input terminal of the AND circuit 25.

Even if the system power supply voltage detection circuit 32 outputs a Hi signal, the microcomputer 16 is not immediately reset by the delay circuit DL2, and the voltage of the system power supply becomes a voltage sufficient to start the microcomputer 16. The reset is delayed until it is reached. That is,
When the voltage of the system power supply is sufficient, the microcomputer 16 is reset.

The microcomputer 16 is connected to a nonvolatile memory 35 such as a flash memory. The memory 35 stores, as backup data, various setting values and the like previously set together with the operating system (OS). After the microcomputer 16 starts up and starts up the OS, the microcomputer 16 reads backup data from the memory 35 as appropriate and drives each unit.

The microcomputer 16 has an OS
Then, a system operation signal (hereinafter referred to as an ACT signal) is output from an ACT terminal to an AND circuit 25 to control the power supply activation circuit 15. The microcomputer 16 monitors the voltage of the main power supply input from the main power supply voltage detection circuit 14 and monitors a power-off signal (PWoff signal) from the power button SW1. In addition, PWo
The ff signal is output when the power button SW1 is operated again after the microcomputer 16 is completely activated.

The operation of the power supply control device 10 configured as described above will be described with reference to FIGS. AA battery 11
Is set in the battery compartment of the digital camera, the main power supply voltage detection circuit 14 detects whether or not the voltage of the AA battery 11 is equal to or higher than the minimum specified voltage V1 required for the operation of the digital camera. When the voltage of the AA battery 11 is equal to or higher than the specified voltage V1, it is determined that the main power supply is present, and the Hi signal of the main power supply presence / absence detection signal (hereinafter referred to as the VDET signal) is output from the Output to the microcomputer 16. However, at this time, since the microcomputer 16 has not been started up, VD
The Hi signal of the ET signal is input only to the AND circuit 21. Further, since the microcomputer 16 is not supplied with the standby current, the consumption of the AA battery 11 is extremely small.

Next, when the power button SW1 is pressed, one square wave P having a short time width is output from the monostable multivibrator MM1 to the monostable multivibrator MM2. The monostable multivibrator MM2 has a square wave P
A square wave Q having a longer time width than the square wave P is output to the OR circuit 22 and the microcomputer 16 at the timing of the falling edge of. However, at this time, the microcomputer 16 has not been started up, so that the square wave Q is input only to the OR circuit 22.

While the square wave Q is being input to the OR circuit 22, Hi is output from the OR circuit 22 to the AND circuit 21. Becomes Hi. As a result, the output from the OR circuit 23 immediately becomes Hi, and the PWCT is supplied from the power supply activation circuit 15 to the DC / DC converter 30.
When the L signal = Hi is output, the DC / DC converter 3
0 starts activation.

The time width of the square wave Q is set to be equal to or longer than the time required for the voltage of the system power supply output from the DC / DC converter 30 to reach the specified voltage V2 required to drive the entire system. . Further, once the monostable multivibrator MM2 starts outputting the square wave Q, it does not receive the square wave P from the monostable multivibrator MM1 within the time width of the square wave Q. Even if the power button SW1 is inadvertently operated during the raising operation, the power-off process is not started, and the microcomputer 16 does not hang up.

When the DC / DC converter 30 is activated and the AA battery 11 starts to supply power, the switch SW3 is turned on, and the output from the DC / DC converter 30, that is, the system power is supplied to the microcomputer 1
6 and a system power supply voltage detection circuit 32. When the voltage of the system power supply reaches the specified voltage V2, the output Hi from the system power supply voltage detection circuit 32 is sent to the AND circuit 33 and the delay circuit DL2.

Since both input terminals of the AND circuit 33 become Hi with a delay of a predetermined time by the delay circuit DL2, the reset signal is output from the AND circuit 33 after the voltage of the system power supply becomes sufficiently higher than the specified voltage V2. It is sent to the computer 16. After the microcomputer 16 is reset, it is started by a system power supply input from a power input terminal.

When the microcomputer 16 is started, it immediately reads the OS from the memory 35 and starts it up, and then outputs an ACT signal to the AND circuit 25 to start the PWC.
Maintain the TL signal = Hi. Thus, the drive of the DC / DC converter 30 is continued even after the output time of the square wave Q from the monostable multivibrator MM2 has elapsed, and the system power is stably supplied to each unit.

The microcomputer 16 has a memory 35
After reading the previous setting data from, a check of each terminal, a timer start after the count value is set to 0, a mode check such as a shooting mode or a reproduction mode, and the like are performed. Then, control of each unit is started. For example, in the photographing mode, the lens barrier of the photographing lens is moved from the closed position to the open position, the photographing lens is moved from the retracted position to the initial photographing position where photographing is possible, and the liquid crystal panel is turned on and the photographing lens is turned on. Displays the image that is projected through. Also, the VDET signal from the main power supply voltage detection circuit 14 and the output (PWoff) from the monostable multivibrator MM2
Signal).

To stop using the digital camera and turn off the power, the power button SW1 is pressed again. Thereby, PWo is output from the monostable multivibrator MM2.
The ff signal is input, and the microcomputer 16 executes a power-off process. At this time, the AND circuit 21
Is output to the OR circuit 23 and the delay circuit DL1. Since the delay of both input terminals of the OR circuit 23 by the delay circuit DL1 is delayed, there is a time margin (delay time) before the output from the OR circuit 23 changes from Hi to Lo. The power-off process by the microcomputer 16 is performed within the time until the output from the OR circuit 23 changes from Hi to Lo.

In the power-off process, first, a liquid crystal panel,
The end operation of each part such as the photographing lens is performed, for example, the driving of the liquid crystal panel is stopped, the backlight is turned off, the photographing lens is retracted, and the lens barrier is closed. Next, various setting values and the like are stored in the memory 35 as backup data. Finally,
After disabling the output terminal of the microcomputer 16 connected to the memory 35, the ACT signal is changed to Lo.
To make the PWCTL signal Lo, DC /
After the DC converter 30 is turned off (system power is turned off), the power of the microcomputer 16 itself is immediately turned off. The delay time of the delay circuit DL1 is P
It is set longer than the time until the WCTL signal becomes Lo.

While using the digital camera, the AA battery 11
Is exhausted and the voltage of the AA battery 11 drops below the specified voltage V1, or when the system power supply drops below the specified voltage V2, the microcomputer 16 performs an emergency power-off process. In this process, since there is no power margin for collapsing the taking lens and closing the lens barrier, after writing various setting data and the like in the memory 35, the function of the output terminal of the microcomputer 16 is suppressed. Thereafter, the PWCTL signal is set to Lo, the system power is turned off, and the power of the microcomputer 16 itself is turned off. Also in this process, since the system power is turned off after data backup is always performed, the AA battery 11
When the power button SW1 is pressed after replacing the camera with a new one, the microcomputer 16 starts up normally, and the photographing lens and the like return to the normal initial startup state, so that the digital camera can be used without any problem.

If an accident such as accidental removal of the AA battery 11 during the startup of the microcomputer 16 occurs, RESET = Hi and PWCTL = Hi, and the output terminal of the microcomputer 16 is still in the function inhibited state. Occasionally, VDET = Lo and PWCTL = Lo, and the system power is turned off. However, since access to the memory 35 has not occurred, the data in the memory 35 has not been changed. Therefore, if the AA battery 11 is correctly set and the power button SW1 is pressed again, the microcomputer 16 can be operated without any problem.
Starts up and you can use your digital camera.

When the occurrence of the accident is RESET = H
If i and PWCTL = Hi, and the microcomputer 16 starts writing to the memory 35, it means that the microcomputer 16 has already read the OS from the memory 35 and has completed initial operations such as mode check. , The microcomputer 16 can execute the power-off control as usual. Therefore,
In this case, since the microcomputer 16 turns off its own power after performing the above-described emergency power-off process, if the AA battery 11 is correctly set again and the power button SW1 is pressed again, there is no problem. Instead, the microcomputer 16 is activated and the digital camera can be used.

Next, in FIG. 5 showing the second embodiment,
The power control device 40 uses a volatile RAM RAM 41 in place of the memory 35 of the first embodiment described above, and adds a backup power circuit to the RAM 41. This power supply circuit includes a charging circuit 42, a charging voltage detection circuit 43, a switch SW4, and a capacitor 44. The capacitor 44 is connected to the RAM 41. The capacitor 44 has a large capacity. Further, the capacitor 44 may be replaced with a secondary battery such as a polyacene battery.

When the AA battery 11 is set in the battery compartment of the digital camera equipped with the power control device 40, the charging circuit 42 starts operating. When the output voltage from the charging circuit 42 reaches a predetermined charging voltage, the charging voltage detection circuit 43 detects this and turns on the switch SW4, and the charging circuit 42
This backs up the RAM 41 and charges the capacitor 44.

When the AA battery 11 is consumed and drops below the specified voltage, or when the AA battery 11 is pulled out, the output voltage from the charging circuit 42 drops below the predetermined charging voltage or becomes zero. , The charging voltage detection circuit 43 detects this and turns off the switch SW4. After the switch SW4 is turned off, the discharge voltage of the capacitor 44 causes RA
The M41 is backed up.

The delay circuits DL1 and DL2 used in the first and second embodiments are general ones using capacitors. Since it is difficult to make the capacitance and temperature characteristics of the capacitor completely constant, errors are likely to occur in the delay times generated by the extension circuits DL1 and DL2. In FIG. 6 showing a third embodiment in which this point is improved, a power supply control device 50 shown in FIG.
Uses counters CT1 and CT2 instead of the delay circuits DL1 and DL2. These counters CT1, C
T2 performs a more accurate delay operation than the delay circuits DL1 and DL2 by counting clock pulses generated by the clock circuit 51. The same components as those in the first embodiment are denoted by the same reference numerals.

The clock circuit 51 amplifies and divides the clock pulse generated by the oscillator 52 incorporated therein to generate a clock pulse of a predetermined frequency. Clock circuit 51
Generates clock pulses generated by the counters CT1 and CT2.
Not only that, it is also sent to the monostable multivibrators MM1 and MM2 and the microcomputer 16 and used for the timing control of the power supply control device 50 as a whole. The oscillator 5
As 2, for example, a quartz oscillator, a piezoelectric ceramic, or the like is used. Note that the operation of the power supply control device 50 is the same as that of the first embodiment, and a description thereof will be omitted. In the present embodiment, the clock circuit 51 and the power supply activation circuit 15 are integrated on the same IC, so that the counters CT1 and C
It was found that the operation accuracy of T2 was further improved.

The embodiment described above is a digital camera, but the present invention is not limited to this, and a digital video camera, a portable information terminal (PDA), a portable telephone, a voice memo, a portable audio player, etc. It can also be applied to electronic devices.

In the above embodiment, as the power switch,
Although the power button which is pressed is employed, a dial type or a lever type may be used. Although the voltage of the main power supply is detected to detect the presence or absence of the main power supply, the current of the main power supply may be detected.

[0038]

As described above, according to the power supply control device of the present invention, no current flows to the microcomputer when the power is not turned on, so that the main power supply is hardly consumed when the electronic device is not used. be able to. In addition, since the ON signal of the power switch is output only for a certain period of time, it is possible to prevent an accident in which power-on / power-off is repeated without permission. Also, since the power supply circuit is not delayed when it is started, and is delayed for a certain time when it is stopped,
The startup time is short, and when the power is turned off, the power supply voltage can be extended to perform data backup or the like. The microcomputer reset is delayed and stopped immediately, so that the microcomputer can be started safely and reliably after the output of the power supply circuit is sufficiently stabilized, and power-off processing such as data backup is performed. The power of the microcomputer can be turned off as soon as the operation is completed. Further, since the delay means is controlled by a clock means for generating a constant clock pulse, it is possible to eliminate errors due to variations in components constituting the delay means and temperature characteristics, and to perform a delay operation at accurate timing. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a power supply control device.

FIG. 2 is a time chart of the power supply control device.

FIG. 3 is a flowchart showing power-on control of the power supply control device.

FIG. 4 is a flowchart showing power-off control of the power supply control device.

FIG. 5 is a block diagram showing a second embodiment of the power supply control device.

FIG. 6 is a block diagram showing a third embodiment of the power supply control device.

[Explanation of symbols]

 10, 40, 50 Power control device 11 AA battery 14 Main power supply voltage detection circuit 15 Power supply start circuit 16 Microcomputer 30 DC / DC converter 32 System power supply voltage detection circuit 35 Memory 41 RAM 42 Charging circuit 51 Clock circuit 52 Oscillator CT1 , CT2 counter DL1, DL2 delay circuit MM1, MM2 monostable multivibrator SW1 power button SW2-4 switch

Claims (4)

[Claims] 1. A main power supply detecting means for detecting the presence or absence of a main power supply by detecting a voltage or a current of a main power supply such as a battery, and a signal for holding an ON signal of the power switch for a predetermined time every time the power switch is operated. Holding means, the main power supply is detected,
A power supply activating means for activating a power supply circuit while the ON signal of the power switch is held; A power supply control device comprising a computer. 2. The power supply activating device according to claim 1, further comprising a first delay unit that does not delay when activating the power supply circuit and delays the power supply circuit for a predetermined time when halting the power supply circuit. The power supply control device as described in the above. 3. A voltage detection circuit for detecting an output voltage of the power supply circuit between the power supply circuit and the microcomputer, when the output voltage of the power supply circuit rises and reaches a predetermined voltage. And a second delay means for delaying the reset of the microcomputer for a predetermined time, and resetting the microcomputer without delay when the output voltage of the power supply circuit falls below a predetermined voltage. 3. The power supply control device according to claim 1, wherein: 4. The power supply control device according to claim 2, wherein the delay unit is controlled by a clock unit that generates a constant clock pulse.