Diagnostic device

A diagnostic device comprising:

• a shifter configured to receive an excitation signal EXC+ to be input to a first end of an excitation coil of a resolver and an excitation signal EXC− to be input to a second end of the excitation coil, and shift a level of at least one of the excitation signal EXC+ and the excitation signal EXC− so that a period from first timing as a starting point to second timing as an end point becomes equal to or less than a predetermined threshold, the first timing and the second timing at which the excitation signal EXC+ and the excitation signal EXC− have a same value in a vicinity of a peak value of the excitation signal EXC+;
• a trigger generation circuit configured to generate a trigger during the period;
• a control unit configured to diagnose whether there is an abnormality in a resolver circuit based on the trigger;
• and
• a sample-hold circuit configured to hold a value of an output signal SIN+ that is output from a first end of a first secondary coil of the resolver, an output signal SIN− that is output from a second end of the first secondary coil, a value of an output signal COS+ that is output from a first end of a second secondary coil of the resolver, and a value of an output signal COS−that is output from a second end of the second secondary coil,
• wherein the control unit determines that there is an abnormality in any of the output signals SIN+, SIN−, COS+, and COS− when an absolute value of half of a sum of the value of the output signal SIN+ and the value of the output signal SIN− becomes more than a predetermined threshold or when an absolute value of half of a sum of the value of the output signal COS+ and the value of the output signal COS− becomes more than a predetermined threshold.