DE19734292A1 - Electronic control for electronically-commutated unipolar DC motor - Google Patents

Abstract

The electronic control has an external controlled switch (Q2) for controlling each motor phase (1, 2, 3). The phase voltage or the current are regulated through the phase winding inductance (L1) via the switch or a free-running circuit. The free running circuit contains a second external controlled switch (Q1), for interrupting the free-running circuit when the induced voltage in the corresponding phase changes polarity.

Description

The invention relates both to a method for electronics taxes of commutatorless unipolar multiphase DC motors as well as an electronic circuit regulation for the electronic control of commutatorless uni polar multi-phase DC motors, each with one externally controllable switch and a freewheeling circuit for each phase.  

Bipolar and conventional adjustable unipolar electronic Controls for commutatorless DC motors need two series-connected semiconductors to control the motor. In applications where the voltage is low, e.g. B. in Automotive sector, the resulting voltage drop case very unfavorable. Accordingly, the engine must be different be dimensioned and the energy losses in the elek tronic controls are higher.

In addition, conventional unipolar electronic Controls each in the self-inductance of the wick magnetization energy of the respective phase lost or recuperated only with a certain effort bar.

It is therefore an object of the present invention to provide a verb procedure and a simplified electronic scarf arrangement for controlling commutatorless unipolar to create multi-phase DC motors.

According to the invention, this object is achieved by a control method solved, in which each phase by an external one controllable switch is controlled, the phase span voltage or the current at the self-inductance of the winding the respective phase both by external control of the Switch as well as through a freewheeling circuit when the Switch is not controlled externally, is regulated, and in which the freewheeling circuit with another, external controllable switch is interrupted at least then if the voltage induced in the respective phase is her Sign changes or before in the respective phase in induced voltage short-circuited by the freewheeling circuit would be sen.  

The freewheeling circuit, which in combination with the (first) switch (Q ₂ ) in a pulse width modulation method or a similar method regulates the phase voltage or the current in the respective phase, can with the further (second) switch (Q ₁ ) can be switched off. This freewheeling circuit must be switched off before it short-circuits the voltage induced in the respective phase. The freewheeling circuits can be switched off in all phases of the motor.

With the control method according to the invention, the Mo gate with the same number of (semiconductor) switches (e.g. 6 switches for a 3-phase motor) as with bi polar controls. The advantage is that the current only in a (semiconductor) switch at a certain time point flows. The voltage drop can thus be halved if the same transistor types are used.

In a preferred embodiment of the control process the further switch gives the freewheeling circuit for so long as free as possible, which is part of the self-inductance existing magnetization energy is simply recuperated can be. With externally controlled, closed first Switch and externally uncontrolled, open second Switch can be used during this time interval Self-inductance still existing magnetization energy be broken down slowly. Because during this time interval the voltage induced in the respective phase is still negative - compared to the supply voltage U⁺ - results a motor with the slowly decreasing current Torque, whereby the magnetizing energy is partially right is cooked.  

If after breaking the free-wheel circuit by the other switch is the externally not controlled switch or the externally uncontrolled additional switch from free circuit is controlled internally, can remain de magnetization energy in the via a Zener diode (Zener diode) internally controlled switch, which thereby becomes a voltage-controlled resistance is converted, consumed become. The advantage of delayed shutdown of the first Switch opposite the second switch is that the magnetizing energy largely without additional Components can be recuperated. This leads to a better one efficiency and less losses.

The above-mentioned task is performed at the beginning electronic circuit arrangement solved by an im Freewheeling circuit provided further, externally controllable ren switch, which already with respect to the tax advantages mentioned.

Further advantages of the invention result from the Be writing and drawing. Likewise, the above mentioned and invented the features further invented in accordance with the invention individually for themselves or for several in be arbitrary combinations are used. The shown and The embodiments described are not intended to be final Understand enumeration, but rather have exemplary th character for the description of the invention.

It shows:

FIG. 1a, the inventive circuit arrangement for Pha se 1 a direct current motor, wherein the current flow through the phase 1 in a first actuation at a time t (e.g., t ₁ <t <t _2,.) Is also shown;

Fig. 1b shows the circuit arrangement of Figure 1a with the current flow through the circuit arrangement in a two-th control at a time t (z. B. t ₃ <t <t ₄ ).

Fig. 1c, the circuit arrangement of Figure 1a with the current flow in a third control, namely at a time t (t ₄ <t <t ₅ ). and

Fig. 2 schematically shows the current flow over time at transistor switches Q ₂ (curve a)) and Q ₁ (curve b)) as well as at the self-inductance L ₁ (curve c)) in phase 1 of the DC motor and the time course of the Transistor switches Q ₁ , Q ₂ externally controlling control signals S ₂ (curve d)) and S ₁ (curve e)).

The circuit arrangement shown in Fig. 1 is used to control a commutatorless three-phase unipolar DC motor M. For this purpose, the circuit arrangement has two semiconductor switches Q ₁ and Q _{2 designed} as MOSFET transistors for each phase, only in Fig. 1 the control for phase 1 is shown. The control of phases 2 and 3 is carried out with appropriate circuitry. The phases 1, 2, 3 are each energized one after the other for a duration of T / 3 (T: period of electrical revolution or electrical switching period), as a result of which the DC motor M runs.

The DC motor M could also be n-phase, and the switches Q ₁ and Q ₂ could also use other technologies, e.g. B. bipolar or IGBT. The self-inductance of the windings of phases 1, 2 and 3 are designated L ₁ , L ₂ and L ₃ .

The self-inductance L ₁ , the switch Q ₁ and a free-wheeling diode D ₁ , as described below, form a freewheeling circuit. In the following, the timing of the switches Q ₁ and Q _{2 is applied} via external control signals S ₁ and S _2, respectively, to their gate, and the resulting current profile I _Q1 , I _Q2 at the switches Q ₁ , Q ₂ and I _L1, respectively the self-inductance L ₁ with reference to FIG. 2 for phase 1 explained at different times:

• - 1st time interval (t ₁ <t <t ₂ ):
  If phase 1 is to be energized, ie at time t ₁ , Q ₁ is continuously driven by the external control signal S ₁ ( FIG. 2e). This ensures the electrical connection of the cathode of the freewheeling diode D ₁ to the supply voltage U⁺ (eg 12 V). At the same time, Q _{2 is driven} by an external control signal S ₂ ( FIG. 2d). A current flows from U⁺ via L ₁ and Q ₂ to U⁻ ( Fig. 1a). The current I _Q2 flowing through Q ₂ ( FIG. 2a) and thus the current I _L1 at the self-inductance L ₁ ( FIG. 2c) increase in accordance with the self-inductance L ₁ between t ₁ and t ₂ , depending on the input voltage, the voltage induced in phase 1 - ie the speed - and the currents flowing in the other phases through inductive negative feedback.
• - 2nd time interval (t ₂ <t <t ₃ ):
  If Q _{2 is} no longer activated at time t ₂ , a current I _Q1 flows via Q _{1 in} accordance with the induction current which continues to flow in L ₁ . As a result, the magnetization contained in L ₁ is reduced. Correspondingly, at time t _2, the current I _L1 drops from its value at time t ₂ until signal Q ₂ is switched off again by signal S ₂ I _Q1 and I _Q2 or I _L1 rise again. This process is repeated continuously in the second time interval, so that this activation of Q ₂ by S ₂ leads to the current profile I _L1 shown in FIG. 2c. The pulse width (clock frequency) of the signal S ₂ allows the maximum current I _L1 and the duration of the second time interval, ie the speed of the direct current motor M, to be regulated as a function of the self-inductance L ₁ of phase 1. To simplify the electronics, it is also possible to start the pulse width modulation from t ₁ (instead of t ₂ ). The disadvantage is that the current I _{Q1 will} increase more slowly.
• - 3rd time interval (t ₃ <t <t ₄ ):
  Between t ₃ and t ₄ , when Q _{2 is} no longer actuated externally, the magnetization present in L ₁ slowly degrades only in the closed freewheeling circuit formed by L ₁ , D ₁ , Q ₁ ( FIG. ₁ b), and I _L1 decreases ( Fig. 2c).
• - 4th time interval (t ₄ <t <t ₅ ):
  At time t ₄ , that is, with a time delay compared to the switch-off time t ₃ of Q ₂ , transistor Q ₁ is also no longer driven externally, so that after time t ₄ there is no longer a path for the remaining current still present in L ₁ . If there is still a current after time t ₄ , the voltage at the drain of Q ₁ and Q _{2 increases} . This voltage increases the breakdown voltage (e.g. 24 V or 30 V) of the Zener diode (Zener diode) D ₂ or D ₃ , which connects the freewheeling circuit to the gate of Q ₁ or Q ₂ , so the switch Q ₁ or Q _{2 is} now partially internally controlled again. Q ₁ then functions as a voltage-controlled resistor, via which the energy still present in L ₁ is discharged ( FIG. ₁ c). At Q ₁ - in contrast to the pure freewheeling current according to Fig. 1b) - a larger voltage, z. B. 9 V, because Q ₁ now regulates the voltage across the Zener diode D ₂ . A corresponding current I _Q2 , as indicated in FIG. 2a in the fourth time interval, can flow off via Q ₂ via U⁻ ( FIG. 1c). A magnetization still present in L ₁ at t ₄ and thus I _L1 degrade correspondingly faster than in the third time interval. At t ₅ , L _{1 is} completely demagnetized, ie current I _L1 no longer flows (I _L1 = 0).
• - 5th time interval (t ₅ <t <t ₆ ):
  Before the voltage induced in phase 1 becomes positive, ie before t ₆ , the connection of phase 1 to voltage U⁺ must be interrupted by D ₁ and Q ₁ , since otherwise there is practically a short circuit.

Claims (4)

1. Method for the electronic control of commutatorless, unipolar, multi-phase DC motors,
in which each phase (1, 2, 3) is controlled by an externally controllable switch (Q ₂ ), the phase voltage or the current (I _L1 ) at the self-inductance (L ₁ ) of the winding of the respective phase ( 1, 2, 3) both by external control of the switch (Q ₂ ) and by a free-wheeling circuit when the switch (Q ₂ ) is not controlled externally, and
in which the freewheeling circuit with a further, externally controllable switch (Q ₁ ) is interrupted at least when the voltage induced in the respective phase changes its sign. 2. Control method according to claim 1, characterized in that the further switch (Q ₁ ) releases the freewheeling circuit as long as possible. 3. Control method according to claim 1 or 2, characterized in that after the interruption of the freewheeling circuit by the further switch (Q ₁ ) of the externally uncontrolled switch (Q ₂ ) or the externally uncontrolled further switch (Q ₁ ) from the freewheeling circuit is controlled internally. 4. Electronic circuit arrangement for the electronic control of commutatorless unipolar multi-phase DC motors, each with an externally controllable switch (Q ₂ ) and a freewheeling circuit for each phase (1, 2, 3), in particular for performing the control method according to one of claims 1 to 3 , characterized by a provided in the freewheeling circuit further, externally controllable switch (Q ₁ ).