| 摘要 |
The device enables a stepping motor (M) to be supplied at constant power whatever the value of the supply voltage. Using a bridge (R1 to R4), a voltage (UAB) proportional to the supply voltage (U0) is tapped. The signal (T1) required to advance the rotor by one step is split into a large number of sampling periods (Te) of predetermined duration. Each of these periods consists of an elementary pulse followed by a period of interruption. The duration (T0) of the elementary pulse is determined by the time taken by a capacitor (C) to become charged: this will become shorter as the proportional voltage (UAB) applied to terminals of a network (RC) becomes higher. A comparator (16) compares the voltage (Uc) across the terminals of the capacitor with a reference voltage (Ur) so as to determine the duration (T0) of the elementary pulse and to define a chopping rate for the supply signal to the motor (M) which is inversely proportional to the supply voltage (U0). <IMAGE> |
