The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 20, 2001
Filed:
Jun. 13, 2000
Yoshihisa Hiramatsu, Kyoto, JP;
Kou Takemura, Kyoto, JP;
Yoshiyuki Hojo, Kyoto, JP;
Nobuhiro Nishikawa, Kyoto, JP;
Rohm Co., Ltd., Kyoto, JP;
Abstract
A power supply device that feeds electric power to an output terminal that is to be connected to a load has first and second PNP-type transistors having their emitters connected to a supplied power line. The collector of the first transistor is connected to the output terminal, and is connected also through two serially connected resistors to ground. An operational amplifier controls the first and second transistors in such a way that the voltage at the node between the two serially connected resistors is kept equal to a setting voltage. To achieve this, a control current is fed to the bases of the first and second transistors. In accordance with the collector current of the second transistor, a limiter circuit limits the output current of the first transistor. The limiter circuit controls the first transistor through the operational amplifier. Between the collectors of the first and second transistors, a capacitor is connected. This capacitor keeps the collector voltage of the second transistor high so as to make the limiter circuit operate when the power supply device is started up or the load is short-circuited.