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Title:
OVERCURRENT DETECTION CIRCUIT
Document Type and Number:
Japanese Patent JPH0713645
Kind Code:
A
Abstract:

PURPOSE: To improve the efficiency of a power source circuit by arranging a resistor on the connection route of one end of a current detection resistor with the base of a transistor and supplying an infinitesimal current to the resistor.

CONSTITUTION: When a load current IL is small, a certain voltage V1 is generated in the resistor 8 and the voltage of VS=RS×IL is generated in the current detection resistor 7. Thus, the voltage of V1+VS is generated between the base and emitter of an NPN transistor 5. In the section of VF>V1+VS with the voltage between the base and emitter defined as VF for turning ON the NPN transistor 5, the NPN transistor is not turned ON and a control signal 6 is not outputted. When VF=V1+VS is attained, the control signal 6 is outputted. Since a part of the voltage between the base and emitter of the NPN transistor 5 for detecting overcurrent and outputting the control signal is prevented from depending on the load current IL, the resistance value of the current detection resistor 7 can be made smaller than before and a generated voltage can be made small.


Inventors:
Hirota, Yoshihiro
Application Number:
JP1993000176050
Publication Date:
January 17, 1995
Filing Date:
June 23, 1993
Export Citation:
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Assignee:
NEC CORP
International Classes:
G05F1/56; H02H3/087; H02M3/155; (IPC1-7): G05F1/56; H02H3/087; H02M3/155
Domestic Patent References:
JPS5310256A
JPS60111372A
JP55187549A
Attorney, Agent or Firm:
▲柳▼川 信



 
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