Motor controller and electric power steering device

A motor controller controlling an energization and a rotation direction of a DC motor that can rotate in a positive rotation direction and a negative rotation direction, the motor controller comprising:

• an H-bridge circuit including four switching elements which are connected in a bridge connection, the H-bridge circuit supplying a direct-current power to the DC motor;
• a switching-element driving circuit PWM driving a first driving circuit and a second driving circuit, wherein the first driving circuit includes the switching elements arranged on a diagonal line of the H-bridge circuit, and the second driving circuit includes the switching elements arranged on the other diagonal line of the H-bridge circuit;
• a motor-current detection circuit including a shunt resistor connected with the H-bridge circuit in a series connection, the motor-current detection circuit detecting a voltage between two ends of the shunt resistor;
• a sample hold circuit executing a sample hold of an output of the motor-current detection circuit at every half period and outputting the output of the motor-current detection circuit obtained when the first driving circuit is turned on as a first signal and the output of the motor-current detection circuit obtained when the second driving circuit is turned on as a second signal, according to a PWM output timing of the switching-element driving circuit;
• and
• a motor-current calculation circuit selecting a signal that is larger between the first signal and the second signal as a selection signal, the motor-current calculation circuit calculating a value of the selection signal as an absolute value of a motor current, the motor-current calculation circuit determining a current direction based on a relation between the selection signal and a PWM output signal at a sample timing that the selection signal is obtained.