DD139966A3 - CIRCUIT ARRANGEMENT FOR SIMPLIFIED BIPOLAR STEPPER MOTOR CONTROL - Google Patents

Abstract

The invention relates to the bipolar activation of step motors, especially for small, simple drives. Object of the invention is to create a simple in construction stepper motor control, the has a high efficiency and low self-heating of the engine causes. By the invention, the problem to be solved, consuming Additional equipment for generating the average holding current and thus the heating limit in bipolar MotoranTeuererung to avoid. According to the invention lies in a bipolar Stepper motor driver with transistor bridge one side of the stator coil directly on one side of the transistor bridge and the other side the stator coil via a series resistor and a capacitor, the parallel, on the other side of the transistor bridge. The circle, by the stator coil and the capacitor are, is as a series resonant circuit educated. The invention is particularly suitable for Positioning and drive tasks in smaller battery-powered Devices used v / earth -

Description

196 451

Circuitry for the simplified bipolar stepping motor control.

.Automation of the invention

The invention relates to the simplified bipolar stepper motor drive with improved efficiency at a narrowed step frequency range and is mainly for. Positioning and drive tasks suitable even in smaller battery-powered devices.

Characteristic of the known technical solutions

If a stepper motor is to be used optimally, it is preferable to operate bipolar; because in unipolar operation one of the two windings is alternately switched off in each stator package. To limit its heating, a lower current, the holding current, is allowed to flow during downtime. This holding current determines the magnitude of the braking torque and is easy to lower in unipolar motors on its value.

In a bipolar motor, the current through the entire coil is switched instead of the alternating operation of coil halves for field reversal. The full utilization of the vee ickel space brings a doubling of the degree of effectiveness. For driving a transistor bridge circuit is preferably used for each stator coil, however, the current reduction in the Still ~ stand sides presents considerable difficulties and forces to special measures. So z. B. to each transistor bridge additionally arranged a current limiter circuit with high hysteresis and two controlled by it gate circuits. One in the

Power supply to the transistor bridge inserted measuring resistor controls the limiter circuit such that upon reaching the maximum current through the gate circuits, the two lower switching transistors of the transistor bridge are blocked. By this additional arrangement ensures that for both Stromflußrichtungen a bridge, the current periodically oscillates between maximum and minimum value, where 'is maintained by the steep high current increase, but the decisive for the allowable heating mean current value is not exceeded. With this arrangement, high-speed drives can be achieved. However, their overall efficiency is very low. "Such control circuits are supplied as standard, matching the engine type. (Vctlvo Manual, Engines 1974 p. 137)

Object of the invention _t

The aim of the invention is to provide for constant pace speeds a simple in construction stepper motor drive, which has a high efficiency and low self-heating of the engine causes. It should also be able to be used in battery-powered portable measuring or scanning devices.

Explanation of the essence of the invention

The invention is based on the object, in de.r bipolar motor drive with a suitable frequency range consuming additional equipment for the generation of the average holding current and thus to avoid the heating limit. According to the invention this is achieved in that each stator coil is only on one side directly to the associated transistor bridge, that for DC-free supply of the step power a capacitor and for supplying the holding current, a series resistor to the. Statorspule is arranged and that the capacitor is constructed with the stator coil as a series resonant circuit.

With this arrangement it is achieved that the turn-off voltage of the stator coil can form almost freely in the switching on or switching moment and that they, as their polarity of the

newly applied voltage is equal, added and thereby a very steep, together with the discharge of the simultaneously reversed capacitor by self-resonant prolonged coil current rise with subsequent rounded peak value arises. It is therefore used in the switching moment on the coil resulting cut-off voltage, which was previously destroyed by diodes.

It is expedient to construct the series resonant circuit so that the series resonance occurs at a frequency of about 0.35 x step frequency. By this frequency selection is achieved that the Stromüberhöhung of the resulting half-wave has its maximum shortly before the end of a step.

Ausführungsbeispie1

The invention will be explained in a Ausführungsbeispxel reference to drawings. Show it:

Fig. 1 shows a circuit according to the invention

Fig. 2 a - 2 c voltage or current waveforms at various measuring points

Fig. 3, the dependence of the maximum rotation

moments from the step frequency

One terminal of the stator coil 1 of a stepping motor is connected directly to a branch 2, 3 of a transistor bridge, while the other terminal for the supply of the holding current is connected via a series resistor 6 to the other branch 4, 5 of the transistor bridge.

Via a second parallel path to the Yorwiderstand 6, the step power is supplied DC-free via a capacitor of the stator coil 1.

The capacitance of the capacitor 7 is so dimensioned that it results in the inductance of the stator coil 1 series resonance for a frequency of about 0.35 x step frequency. By this frequency selection is achieved that the current increase of the resulting half-wave at a step has its maximum just before the start of the next step. This is initiated by Umpien the other stator coil, during which the next step, the current of the previous step

the holding value decreases. In the hold state, the operating voltage is divided by the series resistor 6, wherein approximately half of the voltage applied to the stator coil as the series resistor. The capacitor 7 is also charged to the voltage at the resistor.

If now reversed, the coil field collapses and the resulting turn-off voltage already has the polarity of the newly applied voltage so that it adds to it. Together with the discharge current of the simultaneously reversed polarity of the capacitor 7, a steep current increase which then merges into the sine half-wave of the self-resonance. The AbschaItspannung of the stator coil was previously intercepted by a diode at each stepper motor drive, although - as this example shows - can be of great use. In the present circuit, the diodes 8, 9 »10, 11 only serve to protect the transistors.

In Fig. 2 a, the switching voltages of the transistor bridges are shown. Fig. 2 b shows the approximate course of the coil voltage with (solid line) and without capacitor 7 (dashed curve). In Fig. 2 c, the coil current is shown.

In Fig. 3, the curve a represents the dependence of the torque on the step frequency using the capacitor 7. The curve b represents this dependence without using the capacitor 7. From the curve a it can be seen that in this example for the calculation of Resonant frequency the maximum torque corresponding step frequency of 200 Hz is required. However, it is also possible to use underlying frequencies down to the single step to the drive, although the torque is reduced. By changing the series resistor 6, the capacitance of the capacitor 7 or the inductance of the stator coil 1, the stepper motor can thus be adapted within the scope of its technical parameters to the respective requirements.

Claims (2)

I * Invention claim: 1. Circuit arrangement for the simplified bipolar stepper motor drive using a transistor bridge circuit for driving the stepping motor, characterized in that one side of the stator coil (1) directly to a branch (2,3) of the transistor bridge is that the other side of the stator coil (1) is connected via a series resistor (6) and a parallel capacitor (7) to the other branch of the transistor bridge and that the capacitor (7) with the stator coil (1) is constructed as a series resonant circuit. 2. Circuit arrangement according to item 1, characterized in that the series resonant circuit is constructed for a frequency of 0.35 of the step frequency. flierzu.ji. "Page drawings