DE2329374A1 - CONTROL CIRCUIT FOR RAPID EXCITATION OF ELECTROMAGNETIC SYSTEMS, IN PARTICULAR OF A STEPPER MOTOR - Google Patents

Description

Control circuit for high-speed excitation of electromagnetic systems, in particular a stepper motor.

(Addition to patent application P 22 58 862.1)

The invention relates to a control circuit for rapid excitation of electromagnetic systems, in particular for one by electrical Impulse switchable stepper motor, the rotor of which is spatially offset from one another by excitation of several of several arranged stator coils can be switched forward with a voltage source Can be connected via Lel ± ungstransistors, which one after the other from a pulse generator via a pulse distributor controlled, the mean value of the stator coil current being kept constant with the help of a two-point constant current control is, furthermore, the power transistors both for switching over the respective stator coil and for two-point constant current control be controlled and whereby for the rapid de-energization of the stator coils between the bases and the collectors of the power transistors Zener diodes are arranged, while in each case one controlled by the pulse distributor parallel to the stator coils Semiconductor, in particular a transistor, is in series with a diode, according to main application P 22 58 862.1.

Electromagnetic systems as well as stepper motors of the aforementioned The dynamic characteristics of the species depend very much on the

- 2 "·

A09881 / 0623

Control circuit off, and it is necessary at high step frequencies to excite and de-excite the individual magnetic systems, i.e. different stator coils assigned to the individual steps, in a short time. However, since the rise or fall of current in a solenoid coil is delayed or slow due to the self-induction, a special high-speed excitation circuit was proposed according to the main application, in which the power transistors assigned to the individual stator coils on the one hand for switching the stator coils in accordance with the various steps and on the other hand for Two-point control of the respectively flowing coil current can be switched within one step. If the coil current has risen to a certain, adjustable value after switching on a power transistor, the power transistor is blocked and, taking into account a delay, only opened again when the coil current has fallen below a certain, adjustable value. By switching the power transistors on and off, which corresponds to a 'chopping process ¹ ', a direct current with a relatively low ripple occurs due to the inductive effect of the coil, which depends on the hysteresis behavior of the two-point constant current control.

Only at the beginning of the next step is the current formed or regulated in this way for a specific stator coil for the next cycle interrupted, while the subsequent stator coil is switched on in a corresponding manner. If rapid switching of the stator coils or a rapid step sequence of the motor is desired, the magnetic energy stored in the preceding stator coil must be quickly dissipated so that this stator coil does not exert a torque opposite to the desired movement. However, in order to limit the high cut-off voltages that occur when the current is switched off as a result of self-induction to fourth tm , which is not dangerous for the power transistor, according to the main application, Zener diodes are arranged in a known manner between the collectors and the bases of the power transistors, which act together with the power transistors as controlled free-wheeling diodes, whereby the stored magnetic energy

409881/0623

gie can be dismantled in a very short time. Such a quick one However, the reduction in energy should not take place within one step, i.e. during the constant current regeneration process, otherwise each time the power transistor is switched on for the purpose of constant current regulation, the previously dissipated energy of the stator coil would have to be replaced. On the one hand, this would lead to a greater load on the network and, on the other hand, the Power transistor is mostly switched on. To avoid such a mode of operation, after the main application with a so-called quenching circuit when switching the control device on and off at high frequencies, a slow reduction in the energy in the coil causes stored energy. A occurs only when changing from one stator coil to the other according to the step frequency faster degradation via the combination of zener diode and power transistor. The mentioned cancellation circuits are parallel to the Stator coils and consist of semiconductors controlled by the pulse distributor, for example transistors in series with a for the cut-off current of the coil can be arranged in the forward direction diode. During a step and thus during control of a power transistor and in the course of the control process, the quenching circuit assigned to a stator coil remains in the switched-through state, so that self-de-excitation can only take place relatively slowly via the extinguishing circuit. Only when switching off by the pulse distributor and thus when switching over on the next stator coil, the quenching circuit is interrupted, so that rapid de-excitation via the power transistor as well as the zener diode can be done.

The object of the present invention is the control circuit to improve according to the main application with simple measures so that the stepper motor also from a substantially over the frequency lying at the start-stop frequency can be stopped. This process should be done in no time and without Step losses occur. In addition, the damping behavior should

for operation with single steps or lower Frequency can be significantly improved.

AÜ988 1/0623

The solution to the problem posed is achieved in a control circuit according to the main application in that the controlled semiconductors Via intermediate links in Norirtal operation from the impulse distributor Together with the power transistors, they can be switched on or off one after the other and when a signal is sent to an external control input can be influenced together or individually. In an advantageous embodiment, the links represent logical OR gates, whose first inputs are connected separately to the control logic and whose second inputs are connected together to the external control input are.

The main advantage of the invention is that the rapid de-energization effective in normal operation when switching over the Stator coils can be put out of operation by means of a logic signal at the external control input. In every operating moment there is it is thus possible to interrupt the fast de-energization and thus to slow down the reduction of the coil current.

The invention is illustrated below in a drawing Exemplary embodiment of a circuit diagram that is only slightly modified compared to that from the main application explained.

The controlled stator coils S 1, S 2 and S 3 are each via the power transistors T 1, T 2 and T 3 and the common Emitter resistor R with the terminals R l and B 2 one DC voltage source connected. Zener diodes D 1, D 2 and are parallel to the base-collector sections of the power transistors D 3. The quenching circuits with controlled transistors T 4, T 5 and T 6, each in series, are parallel to the stator coils with one for the discharge current of the stator coil in the forward direction connected freewheeling diode D 4, D 5 and D 0 are located.

The outputs of a control logic SL for switching of the stator coils are each connected to a gate g ,, / ₂ 9 l 'goiJ ^{each case} associated AND gate G 1, G 2 and G 3, the outputs g _1? /

^ ₁ c _,

4U988 1/0623

or g_2 each lead to the base of the assigned power transistor. The remaining gates g _l3 / g ₂₃ and g ₃₃ are a! Comparator K is connected to the output K 3 whose two inputs K 1 and K 2 on the one hand the reference voltage U _{R f} and on the other hand the voltage dropping at the common emitter resistor Rp actual Voltage U _{T is} supplied. Between the second entrance K ?. of the comparator and the emitter resistor Rg, a T-element is arranged with the resistors R 1 and R 2 in the series branch and the capacitor C 1 in the shunt branch. This T-element simulates the inductance of the stator coils S 1, S 2 or S 3 and causes the input voltage at terminal K 2 of the comparator to drop when the power transistors are blocked according to the current in one of the stator coils according to an exponential function . A positive feedback resistor R ^ is also provided between the input K 2 of the comparator and its output K 3, which causes a hysteresis behavior of the switching on and off processes of the power transistors, which is necessary for the constant current regulation.

The controlled transistors of the quenching arrangements are connected in series Diodes prevent inverse operation of the controlled transistors, which are at the outputs of equipotential bonding circuits P 1, P 2 and P 3, respectively. The inputs of these elements are connected to the output of an assigned OR gate G 4, G 5 or G 6 connected, whose first inputs are connected separately to the control logic SL in accordance with the main registration. Against are the second inputs of the OR gates are interconnected and applied to an external control input E. While the control logic SL switches on a specific power transistor and the associated quenching arrangement at the same time during normal operation when applying a logic signal to the external control input E, regardless of the operating state of the circuit, all of them at the same time Extinguishing orders are switched on. Accordingly, all will be done quickly via the power transistors and the zener diodes Fast de-energizing disabled, which means that the energy dissipation of the stator coils via the quenching arrangements accordingly done slowly. This makes it possible to reduce the damping, especially with a single-step process and with low fre-

- ί \ -

AU9881 / 0623

to improve the frequency significantly. In addition, the stepper motor can be stopped from a comparatively very high frequency in a very short time without step losses. The measures required for this are simple and only set a very high level
minor change in the circuit after the main registration
in advance.

Claims

409881/0623

Claims (3)

Λ claims 1.J control circuit for high-speed excitation electromagnetic Systems, in particular for a stepper motor which can be advanced by electrical impulses, the rotor of which is activated by excitation individual of several stator coils arranged spatially offset from one another can be incremented, which with a Voltage source can be connected via power transistors, which one after the other from a pulse generator via a Pulse distributors are controlled, with the mean value of the stator coil current using a two-point constant current control is kept constant, furthermore the power transistors both for switching the respective stator coil as well as for two-point constant current control and whereby for quick de-energization of the stator coils between the Bases and collectors of the power transistors Zener diodes are arranged while parallel to the stator coils in each case a semiconductor controlled by the pulse distributor, in particular a transistor, is connected in series with a diode, according to FIG Main application P 22 58 862.1, characterized in that the controlled semiconductors (T 4, T 5, T 6) via intermediate elements (G 4, G5, G6) in normal operation from the pulse distributor with the power transistors can be switched on or off one after the other and when a signal is sent to an external control input (E) can be influenced jointly or individually. 2. Control circuit according to claim 1, characterized in that the parallel to the respective stator coil (S 1, S 2, S 3) is arranged Controlled semiconductors (T 4, T 5, T 6) if there is no signal to the external control input (E) as long as via the respective associated intermediate member is kept conductive, such as the stator coil is controlled by the pulse distributor, and that the respective power transistor when switched off by the 4U9881 / 0623 Pulse distributor as a result of the self-induced voltage generated by the stator coil between the collector and Base arranged Zener diode (D 1, D 2, D 3) for fast de-energization is only blocked so far that the permissible collector-emitter voltage is not exceeded. 3. Control circuit according to claim 2, characterized in that the intermediate elements (G4, G 5, G 6) logic OR gates represent whose first inputs separately to the control logic (SL) and whose second inputs jointly or separately are connected to one or more external control inputs (E). U 9 8 8 1/0623