Horology: time measuring systems or devices – Power supply details – Electrical
Reexamination Certificate
2002-03-06
2004-06-01
Martin, David (Department: 2841)
Horology: time measuring systems or devices
Power supply details
Electrical
C368S203000, C368S047000, C320S132000, C320S134000, C320S161000
Reexamination Certificate
active
06744698
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
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.
RELATED ART
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 SS
1
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 SS
1
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 SS
1
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 “false detection operation”).
SUMMARY OF THE INVENTION
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
Fujisawa Teruhiko
Kitazawa Koji
Koyama Shunsuke
Gabrik Michael T.
Lindinger Michael L.
Martin David
Seiko Epson Corporation
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