Patent ID: 7193386

Claim:
A motor driving apparatus comprising; a motor having a first coil and a second coil; a first push-pull circuit capable of selecting a state of one of terminals of the first coil among a push state in which a current is supplied to the one of terminals, a pull state in which a current is drawn through the one of terminals, and an open state in which a current does not flow through the one of terminals; a second push-pull circuit capable of selecting a state of one of terminals of the second coil among a push state in which a current is supplied to the one of terminals, a pull state in which a current is drawn through the one of terminals, and an open state in which a current does not flow through the one of terminals; a common push-pull circuit to which another of terminals of the first coil and another of terminals of the second coil are connected as a common terminal, and which is capable of selecting a state of the common terminal between a push state and a pull state; and a control circuit which controls states of the first push-pull circuit, the second push-pull circuit, and the common push-pull circuit, wherein the control circuit controls states of the first push-pull circuit and the second push-pull circuit so as to determine flow directions of current flow into the first coil and the second coil, and the control circuit controls the common push-pull circuit to alternately change the push state and the pull state with a period which is shorter than a period for changing the state of the first push-pull circuit and a period for changing the state of the second push-pull circuit, so that a value of current flown into the first coil and a value of current flown into the second coil are at constants; and wherein the control circuit changes a duty ratio between a push state period and a pull state period of the first or second push-pull circuit according to an equation “period of time of push state”/(“period of time of push state” +“period of time of pull state”) ×100%. in a period which is obtained by adding a push state period which is alternately performed in the common push-pull circuit to a pull state period which is alternately performed in the common push-pull circuit.