Title:
POWER SUPPLY CHANGEOVER CIRCUIT
Document Type and Number:
Japanese Patent JPH0670459
Kind Code:
A
Abstract:
PURPOSE: To eliminate a backward current from an external power supply to a built-in power supply at the time of switchover between the external power supply and the built-in power supply.
CONSTITUTION: An FET 1 whose source is connected to a built-in battery 3, an FET 2 whose drain is connected to the drain of the FET 1 and whose source is connected to a load 20, a controller 4 which is connected to the respective gates of the FET 1 and the FET 2, a power supply switch 5 which is connected to the controller 4 and a detecting circuit 6 which detects the connection of an external power supply voltage and supply the information to the controller 4 are provided.
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Inventors:
OTSUKA TSUNEO
Application Number:
JP10009392A
Publication Date:
March 11, 1994
Filing Date:
April 21, 1992
Export Citation:
Assignee:
NEC CORP
International Classes:
G05F1/00; H02J1/00; H02J9/06; (IPC1-7): H02J1/00; G05F1/00
Attorney, Agent or Firm:
Naoki Kyomoto (2 outside)