| 摘要 |
An electronic device with a display having a light source, such as an electroluminescent element, becomes easier to see and is reduced in size and power consumption when a single boosting element is used for selectively driving the light source and an additional element, such as an alarm. A sound generating circuit charges and discharges with a boosted voltage a charge boosting element, such as a piezoelectric element, in accordance with a control signal supplied by an alarm signal generating circuit. A light source disable circuit discriminates when a signal is being output by an alarm signal generating circuit, and disables a boosting circuit and a discharge circuit used for driving the light source, respectively. The light source disable circuit distinguishes between a driving pulse for driving a light source such as an electroluminescent element to light a display and a control signal from an alarm signal generating circuit for driving a piezoelectric element to sound a buzzer, thereby enabling the selective lighting of the display or the generation of an alarm with only one boosting element.
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