Overcurrent protection apparatus for load circuit

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 (T1) disposed between the power source and the load, a first main electrode of the first semiconductor element (T1) being coupled to a positive electrode terminal of the power source and a second main electrode of the first semiconductor element (T1) being coupled to a negative electrode terminal of the power source via the load, the overcurrent protection apparatus comprising:

• an amplifying section (AMP1) that includes a non-inverting terminal which is coupled to the second main electrode of the first semiconductor element (T1);
• a first resistor (R1) that includes one end which is coupled to the first main electrode of the first semiconductor element (T1) and the other end which is coupled to an inverting terminal of the amplifying section (AMP1);
• a third resistor (R3);
• a second semiconductor element (T2) that includes a first main electrode, a second main electrode and a control electrode, the first main electrode being grounded via the third resistor (R3), the second main electrode being coupled to a point a which is a coupling point between the first resistor (R1) and the inverting terminal of the amplifying section, and the control electrode being coupled to an output terminal of the amplifying section;
• and
• a comparator (CMP1) that includes one input terminal and the other input terminal, the one input terminal being applied with a voltage (V3) at a coupling point (point e) between the second semiconductor element (T2) and the third resistor (R3), and the other input terminal being applied with a determination voltage (V4) which is generated by dividing a voltage (V1) of the first main electrode of the first semiconductor element (T1) by a resistance ratio (R4:R5),
• wherein in a case where a current having a current value (V4/m/Ron), which is obtained by dividing the determination voltage (V4) by a value (m) that is obtained by dividing a resistance value of the third resistor (R3) by a resistance value of the first resistor (R1), by an average value (Ron) of an on-resistance of the first semiconductor element (T1) flows into the first semiconductor element (T1) and the on-resistance is smaller than the average value (Ron) of the on-resistance, a current obtained by adding a current CAW proportional to a deviation (ΔRon) of the on-resistance to a current (I1) flowing through the first resistor at the point a is flown through the third resistor so that an output signal of the comparator (CMP1) is inverted.

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 (T1) disposed between the power source and the load, a first main electrode of the first semiconductor element (T1) being coupled to a positive electrode terminal of the power source and a second main electrode of the first semiconductor element (T1) being coupled to a negative electrode terminal of the power source via the load, the overcurrent protection apparatus comprising:

• an amplifying section (AMP1) that includes a non-inverting terminal which is coupled to the second main electrode of the first semiconductor element (T1);
• a first resistor (R1) that includes one end which is coupled to the first main electrode of the first semiconductor element (T1) and the other end which is coupled to an inverting terminal of the amplifying section (AMP1);
• a third resistor (R3);
• a forth resistor (R4) that includes one end which is coupled to a terminal (point d) of the power source;
• a fifth resistor (R5) that includes one end which is coupled to the other end of the fourth resistor and the other end which is grounded;
• a second semiconductor element (T2) that includes a first main electrode, a second main electrode and a control electrode, the first main electrode being grounded via the third resistor (R3), the second main electrode being coupled to a point a which is a coupling point between the first resistor (R1) and the inverting terminal of the amplifying section, and the control electrode being coupled to an output terminal of the amplifying section;
• and
• a comparator (CMP1) that includes one input terminal and the other input terminal, the one input terminal being applied with a voltage (V3) at a coupling point (point e) between the second semiconductor element (T2) and the third resistor (R3), and the other input terminal being applied as a determination voltage with a voltage (V4) at a point f which is a coupling point between the fourth resistor and the fifth resistor,
• wherein in a case where a current having a current value (V4/m/Ron), which is obtained by dividing the determination voltage (V4) by a value (m) that is obtained by dividing a resistance value of the third resistor (R3) by a resistance value of the first resistor (R1), by an average value (Ron) of an on-resistance of the first semiconductor element (T1) flows into the first semiconductor element (T1) and the on-resistance is smaller than the average value (Ron) of the on-resistance, a current (IR4−I10) obtained by subtracting a current (I10) proportional to a deviation (ΔRon) of the on-resistance from a current (IR4) flowing through the fourth resistor (R4) at the point f is flown through the fifth resistor (R5) so that an output signal of the comparator (CMP1) is inverted.

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 (T1) disposed between the power source and the load, a first main electrode of the first semiconductor element (T1) being coupled to a positive electrode terminal of the power source and a second main electrode of the first semiconductor element (T1) being coupled to a negative electrode terminal of the power source via the load, the overcurrent protection apparatus comprising:

• an amplifying section (AMP1) that includes a non-inverting terminal which is coupled to the second main electrode of the first semiconductor element (T1);
• a first resistor (R1) that includes one end which is coupled to the first main electrode of the first semiconductor element (T1) and the other end which is coupled to an inverting terminal of the amplifying section (AMP1);
• a third resistor (R3);
• a forth resistor (R4) that includes one end which is coupled to a terminal (point d) of the power source;
• a fifth resistor (R5) that includes one end which is coupled to the other end of the fourth resistor and the other end which is grounded;
• a second semiconductor element (T2) that includes a first main electrode, a second main electrode and a control electrode, the first main electrode being grounded via the third resistor (R3), the second main electrode being coupled to a point a which is a coupling point between the first resistor (R1) and the inverting terminal of the amplifying section, and the control electrode being coupled to an output terminal of the amplifying section;
• and
• a comparator (CMP1) that includes one input terminal and the other input terminal, the one input terminal being applied with a voltage (V3) at a coupling point (point e) between the second semiconductor element (T2) and the third resistor (R3), and the other input terminal being applied as a determination voltage with a voltage (V4) at a point f which is a coupling point between the fourth resistor and the fifth resistor,
• wherein in a case where a current having a current value (V4/m/Ron), which is obtained by dividing the determination voltage (V4) by a value (m) that is obtained by dividing a resistance value of the third resistor (R3) by a resistance value of the first resistor (R1), by an average value (Ron) of an on-resistance of the first semiconductor element (T1) flows into the first semiconductor element (T1) and the on-resistance is larger than the average value (Ron) of the on-resistance, a current (IR4+I11−I10) obtained by adding a current (I11−I10) proportional to a deviation (ΔRon) of the on-resistance to a current flowing through the fourth resistor (R4) at the point f is flown through the fifth resistor (R5) so that an output signal of the comparator (CMP1) is inverted.

An overcurrent protection apparatus for protecting a load circuit from an overcurrent, the load circuit being arranged in that a first semiconductor element (T1) is disposed between a power source and a load, a first main electrode of the first semiconductor element (T1) is coupled to a positive electrode terminal of the power source and a second main electrode of the first semiconductor element (T1) is coupled to a negative electrode terminal of the power source via the load, wherein

• a voltage between the first main electrode and the second main electrode of the first semiconductor element (T1) is compared with a determination voltage to determine whether or not a current flowing through the first semiconductor element (T1) is an overcurrent;
• the determination voltage is generated by dividing a voltage between the first main electrode of the first semiconductor element (T1) and a ground by a fourth resistor (R4) and a fifth resistor (R5);
• a circuit which detects the voltage between the first main electrode and the second main electrode of the first semiconductor element (T1), a circuit which generates the determination voltage, and a comparator (CMP1) which compares the voltage between the first main electrode and the second main electrode of the first semiconductor element (T1) with the determination voltage are contained in a same integrated circuit;
• and
• in a case where an output of the comparator (CMP1) is not inverted when a current to be determined as an overcurrent is flown through the first semiconductor element (T1), the determination voltage is corrected so that the output of the comparator (CMP1) is inverted by increasing or decreasing a current flowing through the fourth resistor (R4) or the fifth resistor (R5) of a determination value circuit.