Patent ID: 7535189

Claim:
A motor drive circuit comprising: a first power line; a second power line; an H-bridge circuit that includes a first source transistor and a first sink transistor connected serially, a second source transistor and a second sink transistor connected serially, a motor coil connected at a connection point between the first source transistor and the first sink transistor, and first to fourth regenerative diodes disposed respectively on the first and second source transistors and the first and second sink transistors, the H-bridge circuit being connected between the first power line and the ground, the first source transistor and the second sink transistor being switched complementarily to the second source transistor and the first sink transistor; and a voltage constraint circuit connected between the second power line and control electrodes of the first and second source transistors, the voltage constraint circuit constraining increase in the voltage of the control electrodes of the first and second source transistors to a voltage corresponding to the voltage of the second power line, the first and second source transistors being transistors turned on/off in accordance with a voltage difference between an electrode on the first power line and the control electrode, the voltage of the second power line being a voltage that turns off the second source transistor if a current flows from the first source transistor to the second sink transistor.