Speed detector using resolver

A speed detector comprising:

• a fixed frequency oscillator for generating two-phase sine waves adapted to excite two-phase exciting windings of a resolver;
• multipliers (1406 and 1407) for subjecting an output of a detecting winding of said resolver and said two-phase sine waves to multiplication, respectively;
• and a position conversion circuit (1410) and a speed conversion circuit (1411) for receiving outputs of said multipliers to provide a rotation position signal and a rotation speed signal, respectively;
• in which said speed conversion circuit (1411) comprises:
• a multiplier (1413) for subjecting to multiplication a signal from said multiplier (1406) and a signal from a variable frequency oscillator (1412);
• a multiplier (1414) for subjecting to multiplication a signal from said multiplier (1407) and a signal from said variable frequency oscillator (1412);
• a comparator (1415) for subtracting an output of said multiplier (1414) from an output of said multiplier (1413);
• and
• a proportional integration amplifier (1416) for receiving an output of said comparator (1415),
• the output of said proportional integration amplifier (1416) being utilized as said rotation speed signal and applied to said variable frequency oscillator (1412).