OVERCURRENT DETECTING CIRCUIT

PROBLEM TO BE SOLVED: To provide an overcurrent detecting circuit, capable of changing easily a current for overcurrent detection. SOLUTION: This overcurrent detecting circuit has a power MOSFET1 whose source region is divided into a main source part and a sub-source part, plural negative-feedback c...

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1. Verfasser: ARAKI YUMIKO
Format: Patent
Sprache:eng
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Zusammenfassung:PROBLEM TO BE SOLVED: To provide an overcurrent detecting circuit, capable of changing easily a current for overcurrent detection. SOLUTION: This overcurrent detecting circuit has a power MOSFET1 whose source region is divided into a main source part and a sub-source part, plural negative-feedback control circuits 11, 12 by which a negative-feedback control of a gate voltage of the power MOSFET1 is performed corresponding to a current flowing through a load 10, and a constant-current source 2. The negative-feedback control circuits 11, 12 have transistors Q1, Q2 having different emitter area ratios respectively, and a constant-current source 3 connected to a collector terminal of the transistor Q2 through switches SW1, SW2. When either of the switches SW1, SW2 is changed to ON-state, a negative-feedback control is performed so that a current corresponding to the emitter area ratios of the transistors Q1, Q2 will be sent into the main source part of the power MOSFET1. Therefore, a current value for overcurrent detection can be easily changed by changing over the switches SW1, SW2.