| 摘要 |
The invention relates to a control circuit for a brushless self-starting D.C. motor of the type which has a permanent magnet rotor and a stator coil, a magnetic field-dependent component subjected to the rotor field to determine the rotary position, and a controllable electronic servo-element lying in series with the stator coil at the D.C. source, the servo-element controlling the flux through the stator coil in dependence on the rotary position of the rotor, the magnetic field-dependent parameter changes of the magnetic field-dependent component being convertible to a control signal for the servo-element. The control circuit is characterized by including an oscillator with an LC resonance circuit of which the inductance is formed by the magnetic field-dependent component in the form of a sensing coil (10) with a core. The circuit includes a modulator for modulating the oscillation of the oscillator in response to the induction brought about in the sensing coil by the torot field. The control signal for the servo-element is derivable from the modulated oscillator oscillation, and that the oscillator frequency is considerably higher than the rotor speed. The oscillating condition of the oscillator is responsive to the induction in the sensing coil, and the control signal is derivable from the intermittent oscillator oscillation.
|
