Direct current motor drive circuit and fan motor including the same

A fan motor having a direct current motor drive circuit which drives a brushless direct current motor, comprising:

• a hall element that is disposed between predetermined magnetic poles of a coil of the brushless direct current motor;
• an H-bridge drive circuit including a first comparator that receives an input of a sinusoidal signal outputted from the hall element and outputs a first rectangular signal corresponding to the positive voltage of the sinusoidal signal, and a second comparator that receives an input of the first rectangular wave signal and outputs a second rectangular wave signal corresponding to the negative voltage of the sinusoidal signal;
• a dead time circuit which carries out rectangular wave signal processing for turning the first rectangular wave signal and the second rectangular wave signal on at timings wherein ON voltage periods thereof are different from each other;
• and
• an H-bridge circuit that receives inputs of the first rectangular wave signal and the second rectangular wave signal subjected to signal processing in the dead time circuit,
• wherein the H-bridge circuit includes
• a first series circuit in which a second switching element connected to a positive power supply voltage and a first field effect transistor (referred to as FET) connected to the ground are connected in series via a first node,
• a second series circuit in which a first switching element connected to the positive power supply voltage and a second FET connected to the ground are connected in series via a second node, and
• a coil of the direct current motor connected to the first node and the second node.

A direct current motor drive circuit which drives a brushless direct current motor for rotating a magnet rotor that switches polarities of a plurality of magnetic poles when the direction of an applied current is changed, comprising:

• a hall element disposed between predetermined magnetic poles of the motor coil;
• a first comparator which receives an input of a sinusoidal signal outputted from the hall element and outputs a first rectangular wave signal corresponding to the positive voltage of the sinusoidal signal;
• a second comparator which receives an input of the first rectangular wave signal and outputs a second rectangular wave signal corresponding to the negative voltage of the sinusoidal signal;
• a first dead time circuit which provides the first rectangular wave signal with gentle rises and steep falls and outputs it as a first rectangular wave processed signal;
• a second dead time circuit which provides the second rectangular wave signal with gentle rises and steep falls and outputs it as a second rectangular wave processed signal;
• and
• an H-bridge circuit which receives inputs of the first rectangular wave processed signal and the second rectangular wave processed signal,
• wherein the H-bridge circuit includes
• a first series circuit in which a second switching element connected to a positive power supply voltage and a first FET connected to the ground are connected in series via a first node,
• a second series circuit in which a first switching element connected to the positive power supply voltage and a second FET connected to the ground are connected in series via a second node, and
• the motor coil connected to the first node and the second node.