| 摘要 |
1. A control circuit which is able to produce a digital value corresponding to the difference between a measuring frequency (fx ) and a set frequency (fc ), especially in view of the digital control of the speed of a motor (10), this control circuit comprising in combination : - an elaboration circuit (14) furnishing said set frequency (fc ), - a tachometrique probe (22) delivering said measuring frequency (fx ), - an up- and down-counter (16), an upcounting input of which receives said set frequency (fc ), whereas a downcounting input receives said measuring frequency (fx ), the content of said counter (16) representing at a given moment the time integral of the difference (fc -fx ) of said frequencies, - a period comparator (18) receiving said two frequencies and delivering at its output one of three states (positive, negative or zero) corresponding respectively to a positive difference fc -fx , a negative difference fc -fx or a difference zero, - a logical adder-combinator (20) receiving said output signals of said counter (16) and of said period comparator (18) and furnishing at its output a digital value which constitutes a function of the type K1 multiplied with the content of the counter (16) plus K2 multiplied with the sign of the output signal of the period comparator (18), - a digital limiting device (22) branched at the output of said logical adder-combinator (20) and restricting the value of the output signal of the latter to a value between a lower minimum value (B) and an upper maximum value (H), the digital value of the output signal of the adder-combinator (20) limited by the limiting device (22) constituting the digital control output signal of the control circuit, and - a digital power control (24) receiving said output signal from the limiting device (22) and controlling the speed of the motor (10) in accordance with this latter signal. |
