| 摘要 |
PURPOSE:To reduce power consumption of an output transistor by sustaining the high amplitude of driving voltage waveform until an output transistor is saturated thereby utilizing the saturated region, as well as the active region, of the output transistor. CONSTITUTION:Voltage waveforms MU, MV, MW are formed based on the output signals WA, WB, WC from sensors 31, 32, 33 for detecting the rotor position of a brushless motor. The voltage waveforms MU, MV, MW are superposed utilizing the inclining parts Q thereof thus synthesizing a driving voltage waveform D1. Upper and lower parts of the driving voltage waveform are controlled such that the difference A between the crossing voltage VC of adjacent voltage waveforms MU, MV, MW and the voltage VM at the intermediate point of the amplitude of voltage waveform has a constant ratio with respect to the amplitude B of the voltage waveform. In other words, an output transistor Tr 50 is operated using the saturated region as well as the active region thereof thus controlling the waveform of driving voltage for the brushless motor. |
