The present invention relates to an electronic device that operates with a battery as the power source and to a control method for the same.
Notebook computers, word processors, personal digital assistants, and other such portable electronic devices, and electronic devices that are used both indoors and outdoors, such as portable Compact Disc players, televisions with liquid crystal displays, and camcorders, emphasize basic performance and ease of use during battery drive operation, that is, when driven using a battery as the power source. Considering these conditions, such electronic devices are generally comprised to use a secondary battery such as a rechargeable nickel-cadmium battery or nickel-metal hydride battery.
FIG. 11 is a block diagram showing an example of the configuration of the above electronic devices.
Electronic device 200 has a control unit 210 for constantly detecting and comparing the secondary battery output voltage with a specific threshold voltage to monitor when it is time to recharge the secondary battery, and a load group 220 comprising various loads driven by the secondary battery.
When the control unit 210 of an electronic device 200 thus comprised detects that the output voltage has dropped below the specific threshold voltage (3.0 V, for example) after starting detection of the secondary battery output voltage, it switches switch SS1 from on to off and stops power supply to the load group 220.
When the battery is used for an extended period, however, characteristics deteriorate and the internal resistance in particular increases. Therefore, when the residual capacity of the battery is low and the output voltage has dropped, a minute outflow of consumption current from the battery can produce a sharp drop in the power supply voltage, and this can lead to the control unit 210 malfunctioning.
Furthermore, power supply to the control unit 210 continues even after the power supply to the load group 220 has been stopped in the above-described electronic device. If the load of driving the control unit 210 is lighter than the various loads comprising the load group 220 (below the control unit 210 is referred to as a light load, and. load group 220 as a heavy load), the output voltage of the secondary battery recovers by being released from the heavy load (see A in FIG. 12). More specifically, because the secondary battery output voltage drops an amount equivalent to current consumption multiplied by the internal resistance of the secondary battery, the secondary battery output voltage recovers by the difference between the voltage drop during a heavy load and the voltage drop (=V; see FIG. 12) during a light load when it is released from the large heavy load of the current consumption.
When the control unit 210 detects that the secondary battery output voltage has recovered it switches the switch SS1 back from off to on and resumes power supply to the heavy load, but the output voltage of the recovered secondary battery immediately hits the threshold voltage for turning the switch SS1 off. The control unit 210 thus repeatedly runs a process whereby it supplies power to the heavy load despite being unable to drive the heavy load normally (referred to below as xe2x80x9cfalse detection operationxe2x80x9d).
The present invention was conceived with consideration for the conditions described above, and a first object is to provide an electronic device capable of preventing malfunctioning due to a drop in the battery output voltage under conditions such as when the residual capacity of the battery is low. Furthermore, a second object of this invention is to provide an electronic device in which the above-noted false detection operation is prevented.
To achieve these objects, the present invention provides an electronic device characterized by comprising: a battery; multiple load units driven by the battery; a first control unit for limiting driving part of the multiple load units by the battery when the battery output voltage while driving the multiple load units drops to a first threshold voltage; and a second control unit for stopping driving at least part of the multiple load units and the first control unit when the battery output voltage drops to a second threshold voltage after driving part of the multiple load units is limited.
According to this invention, the battery output voltage is monitored by the second control unit after the battery output voltage drops and driving part of the load unit is limited, and when this reaches the second threshold voltage driving multiple load units and the first control unit is stopped. It is therefore possible to prevent malfunctioning of the first control unit in conjunction with a drop in the battery output voltage.
In a preferred aspect of the invention the multiple load units have a heavy load unit and a light load unit with less power consumption than the heavy load unit; and the first control unit stops driving the heavy load unit with the battery when the battery output voltage drops to the first threshold voltage while driving the multiple load units.
Furthermore, the first control unit may output an activation signal to start the second control unit when the battery output voltage drops to the first threshold voltage while driving the multiple load units.
Further preferably, the difference between voltage drop due to internal resistance of the battery when driving the light load unit, first control unit, and second control unit, and voltage drop due to internal resistance of the battery when driving only the second control unit, is smaller than the voltage detection resolution of the second control unit.
Furthermore, in another preferable embodiment the heavy load unit has a wireless communication unit; the first control unit has a means for controlling so that the heavy load unit is intermittently driven by the battery, and a means for terminating intermittent drive of the heavy load unit by the battery when the battery output voltage drops to the first threshold voltage while the heavy load unit is driven by the battery; and the second control unit comprises a means that responds to change in the battery output voltage faster than the first control unit, and interrupts power supply from the battery to the first control unit and terminates intermittent drive of the heavy load unit when the battery output voltage drops to or below a third threshold voltage in a period in which the heavy load unit is not driven by the battery while the heavy load unit is being intermittently driven by the battery.
Furthermore, in another preferred embodiment the electronic device comprises a third control unit that is a means that responds to change in the battery output voltage faster than the first control unit, and prohibits driving the heavy load unit by the battery when the battery output voltage while the heavy load unit is being driven by the battery drops to a fourth threshold voltage that is lower than the first threshold voltage.
In the various modes noted above the light load unit preferably includes a light load for communicating arrival of a recharge time or battery replacement time, and the first control unit drives the light load for communicating arrival of a recharge time or battery replacement time when the battery output voltage drops to the first threshold voltage while driving the multiple load units.
The light load for communicating arrival of the recharge time may be a display device for reporting arrival of the recharge time by displaying a text message or image.
The light load for communicating arrival of the recharge time may be an alarm device for reporting arrival of the recharge time by producing an alarm sound or vibration.
In a preferred mode the load units include a wireless communication function unit driven by the battery for intermittent two-way wireless communication with an external device; and the electronic device comprises a detection means for detecting a condition of the battery; and a fourth control unit for prohibiting driving a specific load unit of the multiple load units other than the wireless communication function unit if wireless communication occurs when the detection means detects that the battery condition has reached a specific state.
An electronic device thus comprised can maintain wireless communication quality even when the battery output voltage drops because driving load units other than the wireless communication function unit having the potential to adversely affect wireless communication is limited.
In a preferred mode the detection means is a circuit for detecting the battery output voltage.
Furthermore, in another preferred mode the detection means is a circuit for detecting remaining battery capacity.
The fourth control unit may determine the load unit or combination of plural load units to be prohibited from driving during wireless communication according to the battery state detected by the detection means.
In a further preferred embodiment of the invention the electronic device can assume a low power consumption mode for wireless communication of synchronization signals at a specific period for maintaining synchronization of a wireless communication network formed with an external device, or an active mode for actual wireless data communication with the external device; and the fourth control unit prohibits driving one or multiple load units other than the wireless communication function unit when in the active mode and during wireless communication of the synchronization signals in the low power consumption mode.
Said wireless communication uses, for example, Bluetooth ((trademark)).
In a preferred mode the load unit prohibited from driving during wireless communication includes any one of the following function units: a buzzer communication function unit dependent upon driving a buzzer, a vibration communication function unit dependent upon driving a motor for a vibrator, a light-emitting communication function unit dependent upon driving an LED, and a display function unit dependent upon driving a liquid crystal display unit.
Furthermore, the present invention provides a control method for an electronic device characterized by comprising: a detection step for detecting the output voltage of a battery disposed as the power source in an electronic device having a heavy load unit with high power consumption and a light load unit with low power consumption; a first control step for limiting driving the heavy load unit by the battery when the battery output voltage drops to a first threshold voltage; and a second control step for stopping driving the heavy load unit and light load unit by the battery when the battery output voltage drops to a second threshold voltage after driving a heavy load unit is limited.
This invention can also be achieved by distributing to users over an electrical communication circuit a program for running this control method on a computer controlling the electronic device, or by recording such a program to a computer-readable recording medium for distribution to users.
Furthermore, from a different perspective this invention provides an electronic device characterized by having multiple load units including a wireless communication function unit for intermittent two-way wireless communication with an external device; and a control unit for prohibiting driving at least a part of the load units other than the wireless communication function unit during wireless communication.
Furthermore, from a different perspective this invention provides an electronic device comprising a battery; a detection means for detecting an electrical condition of the battery; multiple load units including a wireless communication function unit for intermittent two-way wireless communication with an external device; and a fourth control unit for prohibiting driving a specific load unit of the multiple load units other than the wireless communication function unit if wireless communication occurs when the detection means detects that the electrical condition of the battery has reached a specific state.
Furthermore, from a different perspective this invention provides an electronic device comprising a battery; a detection means for detecting an electrical condition of the battery; multiple load units including a wireless communication function unit for intermittent two-way wireless communication with an external device; a first control unit for limiting driving part of the multiple load units by the battery when the battery output voltage drops to a first threshold voltage while driving the multiple load units; a second control unit for stopping driving at least part of the multiple load units and the first control unit when the battery output voltage drops to a second threshold voltage after driving part of the multiple load units is limited; and a fourth control unit for prohibiting driving a specific load unit of the multiple load units other than the wireless communication function unit if wireless communication occurs when the detection means detects that the electrical condition of the battery has reached a specific state.
In this case the first control unit can comprise a CPU, and the function of the fourth control unit and the function of the first control unit can be achieved with the CPU.
During wireless communication in a preferred mode the control unit prohibits driving one or multiple function units, other than the wireless communication function unit, that when driven produce electromagnetic noise greater than or equal to a specified level.
In a preferred mode the detection means is a circuit for detecting the battery output voltage.
In a further preferred mode the detection means is a circuit for detecting remaining battery capacity.
The control unit can determine the load unit or combination of plural load units to be prohibited from driving during wireless communication according to the battery state detected by the detection means.
In a further preferred mode the electronic device can assume a low power consumption mode for wireless communication of synchronization signals at a specific interval for maintaining synchronization of a wireless communication network formed with an external device, or an active mode for actual wireless data communication with the external device; and the control unit prohibits driving one or multiple load units other than the wireless communication function unit when in the active mode and during wireless communication of the synchronization signals in the low power consumption mode.
Said wireless communication uses, for example, Bluetooth ((trademark)).
In a preferred mode the load unit prohibited from driving during wireless communication includes any one of the following function units: a buzzer communication function unit dependent upon driving a buzzer, a vibration communication function unit dependent upon driving a motor for a vibrator, a light-emitting communication function unit dependent upon driving an LED, and a display function unit dependent upon driving a liquid crystal display unit.
Furthermore, from a different perspective this invention provides in a control method for an electronic device having multiple load units operated by power from a battery and including a wireless communication function unit for intermittent two-way wireless communication with an external device a detection step for detecting a battery state, and a control step for prohibiting driving a specific function unit of the multiple load units other than the wireless communication function unit if wireless communication is in progress when the battery state reaches a specific state.
In a preferred mode the electronic device control method includes a step for determining the load unit or combination of plural load units to be prohibited from driving during wireless communication according to the battery state detected by the detection means.
Furthermore, in a preferred mode the electronic device can assume a low power consumption mode for wireless communication of synchronization signals at a specific interval for maintaining synchronization of a wireless communication network formed with an external device, or an active mode for actual wireless data communication with the external device; and the control step prohibits driving one or multiple load units other than the wireless communication unit when in the active mode and during wireless communication of the synchronization signals in the low power consumption mode.
This invention can also be achieved by distributing to users over an electrical communication circuit a program for running this control method on a computer controlling the electronic device, or by recording such a program to a computer-readable recording medium for distribution to users.
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