Step Motor Drive Circuit
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
A three-phase step motor uses only a lower switching transistor and one additional power transistor rather than both upper and lower transistors. This enables a high recovery voltage to be used when stepping to have faster stepping and a low recovery voltage to be used when needed such as during detent of a variable reluctance step motor, for example. A three-phase step motor has windings 1, 2 and 3 connected to a supply voltage, +V. The windings 1, 2 and 3 are connected through power transistors 4, 5 and 6, respectively, to a PWM control 7. A power transistor 8 has its emitter connected to +V, its base connected to a line 9 through a resistor R1, and its collector connected to the line 9.