JP4192797B2 - Secondary battery charging method and charging device - Google Patents

Description

  The present invention relates to a charging method and a charging device for a secondary battery, and more particularly, to a charging method and a charging device that reduce the standby power by stopping the operation of a power supply circuit after the secondary battery is fully charged.

  Currently, devices incorporating a secondary battery as a power source are used in many fields. In addition, the frequency of use is increasing with the increase in functionality and portability of devices, and the demand for secondary batteries is increasing.

  Many of these secondary battery charging devices are also used as a stand for equipment, and when not in use, the equipment is often placed on the charging device for charging. Also, it is often left plugged into a household power outlet even when the device is not being charged.

  However, household electrical appliances that operate by taking in power from a commercial power source for household use do not generate power in the power circuit of the equipment, even if the main power of the equipment is not on, as long as the power cable is plugged into a household power outlet. Consuming. Since it is necessary to detect when the main power supply is turned on and to supply power to the circuit inside the device instantly, it is necessary to operate the power supply circuit that detects ON / OFF of the main power supply. And it leads to power consumption.

  In recent years, environmental problems have been addressed, and demands for reducing the power consumption and standby power consumption of home appliances are increasing. Even in the rechargeable battery chargers that have been popular recently, it is an important issue to reduce standby power in view of the situation that the commercial battery is always connected to a household commercial power source. Patent Document 1 below describes a charging device that prevents an excessive increase in temperature in a battery.

JP-A-9-331636

  As described in Patent Document 1, a conventional secondary battery charging device takes in an alternating current from a commercial power source for home use, converts it into a direct current in a power supply circuit section in the charging device, and thereby charges the battery. As with other home appliances, the rated charging current is not output after the battery is not attached or after the battery charging is finished, but the power supply circuit unit continues to operate and consumes power.

  So far, low power consumption power ICs (Integrated Circuits) and the like have been commercialized for the purpose of reducing standby power. For example, by mounting a circuit (intermittent control circuit) that turns on the power supply only when necessary, the power consumption during standby of the AC adapter is reduced. This circuit has a function to monitor the output voltage with a detection circuit and to output a switching signal when the voltage drops below the set voltage to operate the transformer, and to repeat the control to stop the transformer when the voltage exceeds the set voltage . Although low standby power has been gradually improved, market demand is still high, and it is necessary to develop a dedicated IC that can support low standby power.

  However, since development of an IC requires enormous costs and time, other standby power reduction measures have been demanded.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a secondary battery charging method and a charging apparatus that reduce standby power without using a newly developed IC in a secondary battery charging apparatus.

In order to solve the above-described problem, a first aspect of the present invention is a charging method in which a secondary battery is charged with an output of a power supply circuit, by detecting a battery voltage or a battery temperature of the secondary battery. a step of determining whether the battery has reached full charge, at the time when it has reached the fully charged is detected, while continuing the charging display, the step of stopping the charging current, the charging is detected fully And a step of stopping the charge display by starting a charge end timer with a preset time and completely stopping the ON / OFF operation of the switching element after the set time has elapsed.
In the above charging method, a step is provided for determining whether or not the secondary battery is inserted or removed within the set time of the charge end timer, and when it is determined that the secondary battery is not inserted or removed within the set time of the charge end timer. It is preferable to stop the operation of the power supply circuit and the charging display after the set time is over.

Further, according to a second aspect of the present invention, in the charging device for charging the secondary battery with the output of the power supply circuit, the secondary battery has reached full charge by detecting the battery voltage or the battery temperature of the secondary battery. discriminating means for discriminating whether or not a display means for displaying that it is being charged, the Rukoto is detected that the discriminating means secondary battery reaches the fully charged, to stop the charging current, the display means to continue charging display, the full charge is detected, activates the charge termination timer, completely stopping the oN / OFF operation of the switching element after a lapse of a set time, stops the charging display of the display unit And a control device.
The above-described charging device has second determination means for determining whether or not the secondary battery is inserted / removed within the set time of the charge end timer, and the control means uses the second determination means within the set time of the charge end timer. When it is determined that the secondary battery is not inserted or removed, it is preferable to stop the operation of the power supply circuit and the charging display after the end of the set time of the charging end timer period.

According to the present invention, since the circuit operation of the power supply is stopped after the battery is fully charged and no longer needs to be charged, the power consumption of the power supply can be made as close to zero as possible. For example, it is possible to reduce power consumption (standby power) to 0.001 W or less from the power consumed conventionally by 0.5 W. In addition, after the battery is fully charged and no longer needs to be charged, the secondary battery will not be charged for a certain period of time. Touching can be prevented.

  The power control function used in the present invention is a function given to a general power control IC. Therefore, it is possible to use a conventional power supply control IC, and there is no cost for developing a new IC, so that it can be achieved in a short period of time.

  Hereinafter, an embodiment of a charging device for a secondary battery according to the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit example of a secondary battery charging device to which the present invention is applied. This circuit includes a power supply circuit unit 1, a switch 8, a charge control circuit 13, and a battery 9.

  The power supply circuit unit 1 is a switching power supply circuit, for example, and is connected to an input filter circuit 2 connected to a power supply terminal such as an outlet for supplying an AC voltage from an external power supply such as a household AC power supply, and to the input filter circuit 2. Rectifying / smoothing circuit 3, a PWM (Pulse Width Modulation) converter 4 for stepping up / stepping down the alternating current supplied from the rectifying / smoothing circuit 3, and an output of direct current supplied from the PWM converter 4 to the battery 9. An output detection circuit 12 that detects a voltage and a control circuit 6 that controls the PWM converter 4 based on information detected by the output detection circuit 12 are provided.

  The input filter circuit 2 removes an alternating current in a predetermined frequency band input from a power supply terminal or the like, and transmits only an alternating current having a pulse waveform in a necessary frequency band. The rectifying / smoothing circuit 3 converts, for example, an alternating current only in a necessary frequency band by the input filter circuit 2 into a predetermined direct current, and generates a direct current of a pulse waveform having a stable voltage.

  The PWM converter 4 is a switching unit that controls a direct current supplied to the PWM converter 4 by being connected to the transformer 5 and turned on / off by an electric signal from the control circuit 6. And an element 14. The transformer 5 includes a primary coil 5a to which the rectifying / smoothing circuit 3 is electrically connected and a secondary coil 5b to which the battery 9 is electrically connected via the switch 8, and current is supplied to the primary coil 5a. By being supplied, the secondary coil 5 b induces a voltage and supplies a current having a pulse waveform to the rectifying and smoothing circuit 7. The rectifying / smoothing circuit 7 rectifies and smoothes the voltage of the charging current supplied from the secondary coil 5b to the battery 9, for example.

  The switching element 14 is, for example, a transistor or the like, is disposed between the primary coil 5 a and the control circuit 6, and switches ON / OFF based on a pulse signal supplied from the control circuit 6. When the switching element 14 is ON, a current is supplied to the transformer 5, and when the switching element 14 is OFF, no direct current flows through the transformer 5.

  In the PWM converter 4, in addition to the transformer 5 and the switching element 14, when a rectifying / smoothing circuit 7, an abnormal battery or the like is attached, a switch 8 that cuts off the circuit so as not to flow a charging current is provided. It is provided between the secondary coil 5 b and the battery holding part 15.

  When the switching element 14 is turned on by an electrical signal from the control circuit 6, the PWM converter 4 having such a configuration converts an AC voltage supplied from an external power source or the like through the input filter circuit 2 and the rectifying / smoothing circuit 3. And direct current is supplied to the primary coil 5a of the transformer 5. The PWM converter 4 is supplied with a DC voltage current to the primary coil 5 a, so that a voltage is induced in the secondary coil 5 b and a DC voltage current is generated in the secondary coil 5 b. A smoothed DC voltage charging current is supplied to the battery 9.

  In addition, when the switching element 14 is turned off by the electrical signal from the control circuit 6, the PWM converter 4 stops the supply of direct current to the primary coil 5 a of the transformer 5, and the charging current supplied to the battery 9. Suppress. The charging current for the battery 9 depends on the duty ratio of the signal for turning on / off the switching element 14.

  The output detection circuit 12 includes a photocoupler 10 including a light emitting element 10a and a light receiving element 10b, and a differential amplifier circuit 16 that detects a voltage of a charging current having a pulse waveform supplied from the PWM converter 4 to the battery 9. .

  The photocoupler 10 is connected so as to detect a voltage between the PWM converter 4 and the battery 9, receives a light emitting element 10 a made of a light emitting diode, an optical signal from the light emitting element 10 a, and receives the received optical signal. And a light receiving element 10b made of a phototransistor or the like, which is converted into an electric signal and supplied to the control circuit 6. The photocoupler 10 outputs to the control circuit 6 an electric signal having a light / dark level corresponding to the voltage of the charging current that the light emitting element 10 a flows between the PWM converter 4 and the battery 9.

  The differential amplifier circuit 16 is electrically connected to the light emitting element 10a of the photocoupler 10 and controls the current supplied to the light emitting element 10a. Specifically, the differential amplifier circuit 16 includes a reference voltage source 16a having a predetermined voltage, and a current value supplied to the light emitting element 10a of the photocoupler 10 due to a difference between the charging voltage and the voltage of the reference voltage source 16a. To control. In the photocoupler 10, the light emitting element 10 a emits light at a light / dark level according to the voltage level controlled by the differential amplifier circuit 16.

  The output detection circuit 12 having such a configuration outputs an electric signal having a voltage level controlled in accordance with the voltage of the charging current having a pulse waveform supplied to the battery 9 to the control circuit 6. That is, the output detection circuit 12 detects the output state of the charging current supplied to the battery 9 and outputs an electrical signal based on the detected information to the control circuit 6. The control circuit 6 outputs a pulse signal whose duty ratio is controlled corresponding to the voltage level of the electrical signal supplied from the output detection circuit 12 to the switching element 14 of the PWM converter 4.

  The power supply circuit unit 1 configured as described above is applied to the primary coil 5a of the transformer 5 in the PWM converter 4 in a state in which an AC voltage is changed to a DC voltage from the power supply terminal via the input filter circuit 2, the rectifying and smoothing circuit 3, and the like. When supplied, the secondary coil 5 b is induced to generate a charging current having a DC voltage pulse waveform, and this charging current is supplied to the battery 9. In the power supply circuit unit 1, the output detection circuit 12 detects the output state of the charging current supplied from the PWM converter 4, and the photocoupler 10 sends an electric signal of a voltage level based on the detected information to the control circuit 6. Output. In the power supply circuit unit 1, the control circuit 6 outputs a pulse signal having a pulse width corresponding to the voltage level of the electric signal from the output detection circuit 12 to the switching element 14 of the PWM converter 4, and according to the duty ratio of the pulse signal. Thus, ON / OFF of the switching element 14 is controlled to control the current supplied to the primary coil 5a of the transformer 5.

  Then, the power supply circuit unit 1 supplies a charging current in a state corresponding to the controlled current supplied to the primary coil 5 a from the secondary coil 5 b to the battery 9 via the battery holding unit 15. As described above, the power supply circuit unit 1 supplies the charging current having the pulse waveform rectified by the rectifying and smoothing circuit 7 to the battery 9 in a stable state while confirming the output state of the charging current.

  The charge control circuit 13 includes a charge control switch 8 electrically connected to the battery holding unit 15, and a photocoupler 11 including a light emitting element 11a and a light receiving element 11b.

  The photocoupler 11 includes a light emitting element 11 a composed of a light emitting diode or the like connected to an output from the PWM converter 4, and a light receiving element 11 b composed of a phototransistor or the like that converts a received optical signal into an electric signal and supplies the electric signal to the control circuit 6. And. In the photocoupler 11, the light emitting element 11 a emits light at a light / dark level based on the signal output from the charge control circuit 13, and the light receiving element 11 b that receives the light from the light emitting element 11 a receives the light / dark of the received light signal. An electric signal having a voltage level corresponding to the level is output to the control circuit 6.

  The charge control circuit 13 having such a configuration performs full charge detection based on a change in battery voltage detected from the battery holding unit 15. In the present invention, the battery full charge detection method is not particularly limited, and various methods can be used.

  Here, as an example of the full charge detection method based on the voltage, a voltage drop at the time of full charge specific to a Ni-MH (nickel metal hydride) battery or a Ni-cd (nickel) battery is detected. And a method of detecting a point at which the voltage change becomes negative. The battery voltage has two rising curves as shown by the solid line in FIG. That is, the battery voltage rises relatively abruptly at the beginning of charging, and then comes a period in which the battery voltage hardly changes. After that, the battery voltage rises again and drops slightly after reaching a peak.

  Here, the point at which the initial voltage rise curve becomes gentle is referred to as “initial termination”, and the point at which the voltage rise curve again rises above a certain coefficient is referred to as “late rise”. Also, the point at which the voltage rise curve becomes gentle after the end-stage rise (before the voltage peak point) is referred to as “end-of-term end”. As described above, in charging a secondary battery such as a Ni-MH battery or a Ni-cd battery, it is known that the battery voltage changes in a constant pattern. From this change, it is detected that it is the end-of-term rising period or end-of-term termination period, and the end of charging is determined.

  There is also a method of observing a rise in battery temperature, detecting a phenomenon in which the temperature suddenly rises, and determining full charge. As shown by the broken line in FIG. 3, when the battery reaches full charge, the temperature starts to rise rapidly. At this time, with respect to the battery temperature, ΔT / Δt (detects a point at which the temperature rise within a predetermined time changes more than a specified value) is used to detect full charge and determine the end of charge.

  When the charge control circuit 13 determines that the battery is fully charged from the change in battery voltage or battery temperature, the output to the photocoupler 11 is inverted and the light emitting element 11a of the photocoupler 11 is caused to emit light. The light receiving element 11b that has received the light from the light emitting element 11a outputs an electrical signal corresponding to the level of the received optical signal to the control circuit 6. When receiving the electrical signal from the light receiving element 11b of the photocoupler 11, the control circuit 6 outputs a signal for stopping the PWM converter 4.

  The PWM converter 4 has a function of completely stopping the ON / OFF operation of the switching element 14 based on a signal from the control circuit 6 (latch function). That is, since there is no electric signal from the light receiving element 11b of the photocoupler 11 during charging of the battery, the PWM converter control described above is performed, and the generated current is supplied to the battery 9. When it is detected that the battery is fully charged, the charge control circuit 13 supplies an electric signal to the control circuit 6 via the photocoupler 11, so that the control circuit 6 sends a signal to the PWM converter 4. The switching element 14 is turned OFF and the OFF state is continued. As a result, there is no current flow, and the entire power supply circuit unit 1 becomes non-operating. The power supply circuit unit 1 that has no longer required to output a charging current after the battery reaches full charge can completely stop its operation and reduce standby power to zero.

  The latch function of the PWM converter 4 is a function that is released by disconnecting and reconnecting a power supply terminal such as an outlet for supplying an AC voltage from an external power source such as a home AC power source. This function is given to the conventional power supply control IC. Therefore, when implementing the present invention, no new cost is generated, and the contents can be achieved in a short period of time.

  In addition to the method of immediately stopping the operation of the power supply circuit with the above-described configuration after the charge control circuit 13 determines that the battery is fully charged, the charge end timer that has been set in advance is started, The operation of the power supply circuit may be stopped after determining that the battery has not been removed within the timer time. When the battery is removed, charging is immediately terminated. The battery temperature during charging increases as the charging progresses, and reaches the highest temperature when the battery is fully charged. Some charging devices with a battery cover have been commercialized, but this is because the user is careful not to touch the battery in a high temperature state as much as possible.

  The end-of-charge timer is also considered so that the user does not touch the fully charged battery immediately. This charge end timer does not supply a charging current for a certain period after the battery is fully charged, but continues the charge display. This is an effective means from the viewpoint of safety because the user determines that charging is still continued and does not try to touch the battery. It is effective for some chargers, such as those without a battery cover.

  In the present invention, the full charge detection method is not limited to that described above, and the battery can be applied to various secondary batteries such as a coin type, a button type, and a gum type.

  Next, a charging method in the embodiment described above will be described with reference to the flowchart of FIG.

  In step S1, when the user connects a power supply terminal such as an outlet to a household AC power source or the like, for example, the power supply circuit unit 1 and the charge control circuit 13 are activated in step S2, and the battery 9 can be charged. It becomes.

  Next, the user attaches the battery 9 to the battery holding unit 15 in step S3. At this time, the charging control circuit 13 that detects the battery voltage determines that the battery 9 is mounted due to the voltage change, and outputs a signal for turning on the switch 8. In step S4, a charging current starts to flow through the battery 9, charging is started, and a lamp indicating that charging is in progress is turned on accordingly.

  Next, the charging control circuit 13 always detects the voltage or temperature of the battery 9, and determines whether or not the battery 9 is fully charged in step S5. If it is determined that the battery 9 has been fully charged, a charge completion timer is checked in step S6. In a charging device without a charging end timer, the process proceeds to step S9, and in a charging device incorporating a charging end timer, the process proceeds to step S7. In step S7, a charge end timer starts.

  If it is determined in step S8 that the charging end timer has passed the predetermined time or it is determined in step S6 that the charging end timer is not a built-in charging device, the operation of the power supply circuit is performed in step S9. The charging control circuit 13 outputs a signal for stopping the charging. This signal is supplied to the control circuit 6 via the photocoupler 11, and the control circuit 6 generates a signal for stopping the ON / OFF operation of the switching element 14 of the PWM converter 4, and the operation of the power supply circuit is stopped. Charging is completed when the operation of the power supply circuit is completely stopped (step 10). Therefore, it is possible to achieve a low power consumption charging device that consumes as much power as possible after the end of charging. At this time, the lamp and the like are turned off, and it is displayed that the charging is finished.

  Although the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible.

It is a block diagram which shows one Embodiment of the secondary battery charging device by this invention. 4 is a flowchart illustrating an example of an operation until charging is stopped in the embodiment of the secondary battery charging device according to the present invention. It is a figure which shows the charge characteristic at the time of charge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power supply circuit part 2 ... Input filter circuit 3, 7 ... Rectification smoothing circuit 4 ... PWM converter 5 ... Transformer 5a, 5b ... Coil 6 ... Control circuit 8 ... Switch 9 ... Secondary battery 10, 11 ... Photocoupler 10a, 11a ... Light emitting element 10b, 11b ... Light receiving element 12 ... Output detection circuit 13 ... Charge control circuit 14 ... Switching element 15 ... Battery holding part 16 ... Differential amplifier circuit 16a ... Reference voltage source

Claims (4)

In the charging method of charging the secondary battery with the output of the power circuit,
Determining whether the secondary battery has reached full charge by detecting battery voltage or battery temperature of the secondary battery; and
When the can fully reached the charging is detected, while continuing the charging display, the step of stopping the upper Symbol charging current,
When fully charged is detected, it activates the advance time charge termination timer is set to, by completely stopping the ON / OFF operation of the switching element after a set time has elapsed, and a step of stopping the charging display Charging method. In claim 1,
Determining whether the secondary battery is inserted or removed within the set time of the charge end timer;
And a step of stopping the operation of the power supply circuit and the charge display after the end of the set time when it is determined that the secondary battery is not inserted or removed within the set time of the charge end timer. In the charging device that charges the secondary battery with the output of the power circuit,
Discriminating means for discriminating whether or not the secondary battery has reached full charge by detecting the battery voltage or battery temperature of the secondary battery;
Display means for displaying that charging is in progress;
By Rukoto said discrimination means detects that the secondary battery reaches the fully charged, the charging current is stopped, to continue the charging display of the display unit, when the full charge is detected, charge termination timer And a control means for completely stopping the ON / OFF operation of the switching element after a set time has elapsed and stopping the charging display on the display means . In claim 3,
A second determining means for determining whether or not the secondary battery is inserted / removed within the set time of the charge end timer;
When it is determined by the second determination means that the secondary battery has not been removed or inserted within the set time of the charge end timer, the control means is configured to turn off the power supply circuit after the set time of the charge end timer period ends. A charging device characterized by stopping operation and charging display.

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