Electrical circuit for regulating the current in the windings of certain step motors

Claim 1

In a stepping motor control system, wherein the stepping motor is adapted to be connected to a source (106) of electrical energy, and has a plurality of windings (10a, 10b, 10c) comprising, in accordance with the invention, the circuit combination of separate switch means (11a, 11b . . . ) connecting when closed, a respective winding to the source; separate switch control means (20a, 20b . . . ) respectively connected to and controlling operation of the respective switch means; a buffer capacitor (100); coupling circuit means (17a, 17b . . . ; 19a, 19b . . . ) respectively connected to said respective windings and to the buffer capacitor to transfer stored electromagnetic energy in the respective windings to the buffer capacitor when, after energization of a respective winding, the respective switch means is controlled to open; and a storage circuit (103, 104, 105) including a main storage capacitor, with charge sensing means (101, 111) connected to the buffer capacitor (106) and sensing when the charge accumulated thereon has reached a predetermined value; and connecting circuit means including transfer switch means (102) controlled by the charge sensing means, interconnecting the buffer capacitor (100) and the storage circuit (103, 104, 105), the charge sensing means controlling the transfer switch means (102) to close when the charge on the buffer capacitor (100) has reached the predetermined value to transfer at least a portion of the charge thereon to the main storage capacitor (105), the charge sensing means controlling the transfer switch means to open when the charge level in the buffer capacitor has dropped, so that the buffer capacitor can then receive additional energy from the respective windings while being isolated from the storage circuit.