| 摘要 |
PURPOSE:To provide a driving circuit for brushless motor in which the efficiency does not deteriorates for low output of driving transistor and acoustic noise does not increase for high output. CONSTITUTION:Output voltage from a Hall element 1 is shaped through a shaper circuit 3 output therefrom is then sliced at a predetermined level through a slice circuit 4. Thus sliced voltage is then fed to an output transistor constituting a driving amplifier 5 which produces an output for driving a coil 7. In order to make power loss due to the collector.emitter voltage of the output transistor variable according to the amplitude of driving voltage or driving current, a residual voltage setting circuit 6 for varying the slice level is provided between a driving power supply Vs and the slice circuit 4. The residual voltage setting circuit 6 varies the slice level according to the saturation level Vce of the output transistor which thereby operates in an active region at all times without making a transition to a saturation region. |
