| 摘要 |
PURPOSE:To improve the power efficiency of a brushless motor and to prevent the oversaturation of a drive transistor by controlling the voltage converting means of switching type on the basis of the operating voltage of a drive transistor or correcting the coil supply current. CONSTITUTION:The first feedback loop (current feedback loop) is composed of a current controller 31, a selector 32, drive transistors 5-7, current detecting resistor 36 and a resistor 37, and the supply current to the coils 1-3 is effectively set to the value corresponding to a command signal. The second feedback loop is composed of an operation detector 11, a switch 12, a voltage converter 10 and coils 1-3, and the operating voltages of the drive transistors 5-7 are equalized to the prescribed value (approx. Va-VBE) in the active range. When the conversion signal 92 becomes high level (corresponding to the high speed rotation), the output current i1 of the detector 11 becomes i1=i3, the coil current Ia varies in response to the current i1 and the voltage V1 of a command signal 91. When the current i3 becomes large (the operating voltage of the drive transistor becomes small), the current Ia is corrected by a small amount. |
