Importance

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Abstract

The invention relates to a method and a controlling apparatus for controlling the magnitude and direction of a current (I) through a winding (L). The method and controlling apparatus are based on a drive circuit (TR.sub.1, D.sub.1, TR.sub.2, D.sub.2, TR.sub.3, D.sub.3, TR.sub.4, D.sub.4) which is controllable such as to enter into three different types of operational state. In a first type of operational state the current is normally increasing in magnitude. In a second type of operational state the current is normally decreasing in magnitude comparatively slowly. In a third type of operational state the current magnitude is normally decreased comparatively rapidly. When the drive circuit is in the first type of operational state it is controlled either to remain in this state or to change to the second type of operational state in response to the result of at least one comparison between the actual value of the current and a desired value (I*) carried out during the time the drive circuit was in the first type of operational state. When the drive circuit is in the third type of operational state it is controlled either to remain in this state or to change to the second type of operational state in response to the result of at least one comparison between the current actual value and a desired value carried out during the time the drive circuit was in the third type of operational state. The method and apparatus are primarily intended for microstepping a two-phase stepping motor with a permanent magnetized rotor.

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First Claim