Patent ID: 8295021

Claim:
An overcurrent protection apparatus for protecting a load circuit from an overcurrent, the load circuit including a power source, a load and a first semiconductor element (T 1 ) disposed between the power source and the load, a first main electrode of the first semiconductor element (T 1 ) being coupled to a positive electrode of the power source and a second main electrode of the first semiconductor element (T 1 ) being coupled to a negative electrode of the power source via the load, the overcurrent protection apparatus comprising: an amplifying section (AMP 1 ); a first resistor (R 1 ) that includes one end which is coupled to the first main electrode of the first semiconductor element (T 1 ) and the other end which is coupled to an inverting input terminal of the amplifying section (AMP 1 ); a second resistor (R 2 ) that includes one end which is coupled to a point c that is the second main electrode of the first semiconductor element (T 1 ) and the other end which is coupled to a non-inverting input terminal of the amplifying section (AMP 1 ); a third resistor (R 3 ); a second semiconductor element (T 2 ) that includes a first main electrode, a second main electrode and a control electrode, the first main electrode being grounded via the third resistor (R 3 ), the second main electrode being coupled to a point a which is a coupling point between the first resistor (R 1 ) and the inverting input terminal of the amplifying section (AMP 1 ), and the control electrode being coupled to an output terminal of the amplifying section; and a first current source (IA) which is disposed between the point a and a ground, wherein in a case where a current flows through the load and a voltage at the point a becomes lower than a voltage (V 2 ) at the point c due to an offset voltage of the amplifying section (AMP 1 ), the first current source (IA) is set to flow a current that is equal to a current obtained by dividing a voltage between the point c and the point a by a resistance value of the first resister (R 1 ).