Patent ID: 8390222

Claim:
A brushless motor driving circuit comprising: a drive voltage generating circuit that includes a switching element group including ground-side switching elements having one end there of connected to an output terminal connected to one end of a coil of a brushless motor and the other end thereof grounded, that generates a voltage for driving the brushless motor from a source voltage by turning on/off the switching element group, and that applies the generated voltage to the coil; a drive control circuit that turns on/off the switching element group; and a clamp circuit that turns on/off the ground-side switching elements so that an output voltage becomes equal to or lower than the source voltage, based on the output voltage at the output terminal and the source voltage; wherein: the drive voltage generating circuit includes, as the switching element group, an inverter circuit including a P-type MOSFET to which the source voltage is supplied from a source terminal and an N-type MOSFET whose source terminal is grounded, which are connected in series, a connection point of the P-type MOSFET and the N-type MOSFET being connected to output terminal; when the output voltage and the source voltage are input, and the output voltage is the voltage that corresponds to the source voltage, the clamp circuit turns on the N-type MOSFET; the drive voltage generating circuit is an H bridge circuit including two inverter circuits, which are a first inverter circuit and a second inverter circuit, and two output terminals, which are a first output terminal and a second output terminal, wherein the first output terminal, to which the connection point of the first inverter circuit is connected, is connected to the one end of the coil, and the second output terminal, to which the connection point of the second inverter circuit is connected, is connected to the other end of the coil; and the clamp circuit turns on the N-type MOSFET in the first inverter circuit when the output voltage at the first output terminal and the source voltage are input to the first inverter circuit and the output voltage is the voltage that corresponds to the source voltage, and turns on the N-type MOSFET in the second inverter circuit when the output voltage at the second output terminal and the source voltage are input to the second inverter circuit, and the output voltage is the voltage that corresponds to the source voltage.