Electronic timepiece

1. An electronic timepiece, comprising:

a step motor comprising a coil and a rotor;

a motor driver configured to drive the step motor;

a normal drive pulse generation circuit configured to output a normal drive pulse at a drive rank designated from among normal drive pulses at a plurality of drive ranks different in driving force;

a rotation detection pulse generation circuit configured to output a detection pulse at a predetermined timing after the outputting of the normal drive pulse;

a rotation detection circuit which comprises at least a first detection mode determination circuit configured to conduct a determination in a first detection mode after the outputting of the normal drive pulse and which is configured to detect rotation or non-rotation of the rotor based on a detection signal generated by the detection pulse;

a rotation determination counter circuit configured to count a number of times that the rotation has been successively detected by the rotation detection circuit;

a first detection mode determination counter circuit configured to count a number of times that the detection signal generated by the detection pulse becomes a predetermined detection pattern in the first detection mode; and

a drive rank selection circuit configured to designate a drive rank of the normal drive pulse to be output by the normal drive pulse generation circuit based on results of the counting conducted by the rotation determination counter circuit and the first detection mode determination counter circuit.

2. The electronic timepiece according to claim 1 , wherein:

the first detection mode determination circuit is further configured to detect the rotation or non-rotation of the rotor based on a c 3 current detection pulse being a detection pulse output to a side different from a terminal to which the normal drive pulse is output; and

the first detection mode determination counter circuit is further configured to count a number of times that a detection signal generated by the c 3 current detection pulse has been, or has not been, detected prior to a predetermined timing.

3. The electronic timepiece according to claim 1 , wherein:

the first detection mode determination circuit is further configured to detect the rotation or non-rotation of the rotor based on a c 3 current detection pulse being a detection pulse output to a side different from a terminal to which the normal drive pulse is output; and

the first detection mode determination counter circuit is further configured to count a number of times that a detection signal generated by a c 2 current detection pulse, being a detection pulse output to the same side as the terminal to which the normal drive pulse is output has been, or has not been, detected.

4. The electronic timepiece according to claim 1 , wherein the first detection mode determination counter circuit is further configured to count a number of times that the detection signal generated by the detection pulse has been, or has not been, non-successively detected.

5. The electronic timepiece according to claim 1 , wherein the drive rank selection circuit is further configured to:

change the drive rank to be designated when the number of times counted by the rotation determination counter circuit reaches a predetermined number of times; and

alter a manner of changing the drive rank based on whether or not the number of times counted by the first detection mode determination counter circuit is equal to or larger than a first predetermined number.

6. The electronic timepiece according to claim 5 , wherein the drive rank selection circuit is further configured to select any one of the drive rank exhibiting a driving force smaller than a current drive rank by two or more ranks and the drive rank exhibiting a driving force smaller than the current drive rank by one rank, based on whether or not the number of times counted by the first detection mode determination counter circuit is equal to or larger than the first predetermined number.

7. The electronic timepiece according to claim 6 , wherein the drive rank exhibiting a smallest driving force is selected when the number of times counted by the first detection mode determination counter circuit becomes equal to or larger than the first predetermined number.

8. The electronic timepiece according to claim 5 , wherein the drive rank selection circuit is further configured to select any one of: the drive rank exhibiting a driving force larger than a current drive rank by one rank; the drive rank exhibiting a smallest driving force; and the drive rank exhibiting a driving force smaller than the current drive rank by one rank, based on whether or not the number of times counted by the first detection mode determination counter circuit is equal to or larger than the first predetermined number and whether or not the current drive rank is the drive rank exhibiting a largest driving force.

9. The electronic timepiece according to claim 5 , wherein the predetermined number of times required for a change in the drive rank to be designated by the drive rank selection circuit is changed based on whether or not the number of times counted by the first detection mode determination counter circuit is equal to or larger than a second predetermined number.

10. The electronic timepiece according to claim 9 , wherein the predetermined number of times is reduced based on whether or not the number of times counted by the first detection mode determination counter circuit is equal to or larger than the second predetermined number.

11. The electronic timepiece according to claim 9 , wherein the first predetermined number and the second predetermined number are different from each other.

12. The electronic timepiece according to claim 1 , further comprising a power supply voltage detection circuit configured to detect a voltage of a power source,

wherein the drive rank selection circuit is further configured to alter a manner of changing the drive rank based on a detection result obtained by the power supply voltage detection circuit.

13. The electronic timepiece according to claim 12 , wherein the drive rank selection circuit is further configured to select the drive rank exhibiting a smallest driving force when the power supply voltage detection circuit detects a voltage value larger than that of a predetermined voltage.

14. The electronic timepiece according to claim 1 , wherein the drive rank selection circuit is configured to restrict a change in the drive rank in a case where a detection result of conducting the counting by the first detection mode determination counter circuit is obtained when the normal drive pulse is output to only a specific terminal.

15. The electronic timepiece according to claim 1 , further comprising a correction drive pulse generation circuit configured to generate and output a correction drive pulse to be output when the non-rotation is detected by the rotation detection circuit.

16. The electronic timepiece according to claim 1 , wherein the rotation detection circuit further comprises a second detection mode determination circuit configured to conduct a determination in a second detection mode after the first detection mode is brought to an end.