Current sensor

A current sensor for detecting a detection target current using a terminal voltage of a shunt resistor provided in series in a path through which the detection target current flows and a resistance value for current detection corresponding to a resistance value of the shunt resistor, the current sensor comprising:

• a resistance value correction circuit that corrects the resistance value for detection;
• and
• a power supply circuit that supplies an electric power to the resistance value correction circuit,
• wherein:
• the resistance value correction circuit includes:
• a correction resistor connected in series with the shunt resistor in a path different from the path through which the detection target current flows;
• a signal application unit that applies an alternating current signal to a series circuit of the shunt resistor and the correction resistor;
• a voltage detection unit that detects the terminal voltage of the shunt resistor and a terminal voltage of the correction resistor when the alternating current signal is applied to the series circuit;
• and
• a correction unit that calculates a resistance value of the shunt resistor based on each detection value of the terminal voltage of the shunt resistor and the terminal voltage of the correction resistor detected by the voltage detection unit, and corrects the resistance value for detection based on a calculated resistance value which is the resistance value of the shunt resistor calculated;
• the power supply circuit includes:
• a first power supply generator that generates a first power supply having a low voltage with respect to an input power supply by stepping down the input power supply supplied from an outside;
• and
• a second power supply generator that generates a second power supply different from the first power supply;
• and
• the power supply circuit is configured to supply the first power supply to the signal application unit and to supply the second power supply to the voltage detection unit,
• the signal application unit includes a transistor, a signal generator, and an operational amplifier or a buffer;
• the voltage detection unit includes an A/D converter and a synchronous detector or a semiconductor integrated circuit and
• the correction unit includes a semiconductor integrated circuit or a micro-computer.