Power supply circuit

U.S. Patent Number: 5387820

Abstract: An apparatus using a battery as a power source requires a battery having an extended life time. A burden upon a battery can be reduced by operating the inner circuit at a low voltage and current. The present invention aims at providing a compact and low power consuming apparatus. A battery used as a power source drives a circuit for a low voltage circuit system and a switching circuit which switches power supply when the battery voltage becomes a preset voltage. A circuit for a high voltage circuit is directly driven by the battery when the battery voltage is high, and the circuit is powered from the output (for example, 1.5 volts) of a step-up circuit when the battery voltage is low. Switching of power sources is made in such a manner, resulting in low power consumption. Extension of life time of battery, and reduction in size of battery and apparatus can be achieved.

Inventors: Imagawa; Yasumi (Kanazawa, JP)

Assignee: Matsushita Electric Industrial Co., Ltd. (Osaka, JP)

Application Number: 07/914,519

Issued: 1995-02-07

Expired: 2007-02-07

Classes: 307/31 ; 307/34; 307/39

Field of search: 307/33,34,38,39,31,46,58,66,110,80,82,87,130,140,141.4 361/187

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