SENSORLESS MOTOR DRIVING CIRCUIT

PURPOSE: To reduce the number of parts to be fitted outside and reduce the cost, and to make optimum switching possible always by switching the energization of exciting coils, on the basis of pulses delayed by specified amounts from a reference position of the rotor. CONSTITUTION: If either of exciting coils 1 and 2 is energized, and the rotor R rotates by its magnetic force, a detecting means 3 detects counter- electromotive forces 6s-2 and 6s-4. A differentiated pulse generating means 7 generates a differentiated pulse 7s from the output signal of the detecting means 3. A phase comparator compares the differentiated pulse 7s with a pulse obtained by dividing a clock pulse 8s. A latch delay circuit 9 generates a pulse 9s delayed by a specified amount from a reference position of the rotor R, by counting the clock pulse 8s. Circuits 6 and 12 generates energization switching signals 13s-1 to 13s-4 for the exciting coils 1 and 2 on the basis of the delayed pulse 9s, and switch the energization pattern of the exciting coils 1 and 2 over to the next one compulsorily.