DE102004062580A1 - Multiphase electronically commutated motor regulating method, involves determining regulation relevant parameter by current state of free run diodes, which are arranged in phase half bridge of bridge circuit - Google Patents

Abstract

The method involves determining regulation relevant parameter by a current state (Z) of free run diodes (13, 13a, 13b, 13c), which are arranged in a phase half bridge (6a, 6b, 6c) of a bridge circuit (3). The current state is determined by a unit, in which a power circuit breaker of the phase half bridge (6a) has a conductive state, and another power circuit breaker has a blocking state. An independent claim is also included for a device for control of a multiphase motor.

Description

The The invention relates to a method for controlling a multiphase, electronically commutated motor. The invention further relates to a device for carrying out of the said method.

at an electronically commutated (electric) motor is commutating, i.e. for controlling the motor phases, an inverter is provided, the usual in the form of a bridge circuit is realized. Such a bridge circuit includes a number of motor phases corresponding number of Phase half-bridge, wherein each phase half-bridge over a Voltage intermediate circuit with the positive pole and the negative pole of a DC voltage source is connected and at a center tap a phase terminal includes for connecting an associated engine phase. Within each one Phase half bridge is a high potential side between the phase terminal and the positive terminal Circuit breaker, and between the phase terminal and the Negative pole arranged a low potential side circuit breaker, via which the respective branch of the phase half-bridge is blocked or released can be. Each circuit breaker has a freewheeling diode in parallel switched in the direction of the potential gradient between positive and negative pole is arranged blocking.

By the commutation become oscillating electrical in the motor phases streams stimulated. Under the effect of these motor phase currents in the motor becomes a magnetic Rotary field generated, which drives a rotor of the motor to a rotational movement. Motor control is usually based on the motor phase currents and / or so-called back EMF voltages caused by the rotor rotation be induced in each motor phase.

From the US 6,121,736 A is a control method for an electric motor of the above type is known, wherein for detecting the flow direction change of a motor phase current (hereinafter referred to as zero crossing of the motor phase current) associated with the motor phase terminal voltage detected during a dead time of the circuit breaker in the associated phase half-bridge is detected. The zero crossing of the motor phase current is detected here by a change in the terminal voltage between a ground potential assigned to the negative pole and an operating potential assigned to the positive pole. The dead time is provided in the course of a Kommutierungsschaltprozess switching time, while the two circuit breakers of a phase half-bridge are short-circuiting locked to avoid a quasi-simultaneous switching of the circuit breaker a short circuit between the positive and the negative pole.

One Disadvantage of the known method is that for detection the motor current direction only the comparatively short dead time for Available. A measurement of the terminal voltage is technically acceptable Effort only possible when the dead time is sufficiently large. this Requirement is running contravening the progressive development of modern motor controls. With the commercial availability increasingly more precise Circuit breakers are also increasingly seeking shorter dead times, a disturbing influence deadtime-related harmonics of the motor phase currents to eliminate.

At another, from the US 6,208,112 B1 Known control method for a motor of the above type is provided as a control variable, the phase shift between a motor phase current and the associated back EMF voltage. This phase shift is determined by the deviation between the zero crossing of the motor phase current and the zero crossing of the back EMF voltage. The back EMF voltage is measured in a motor phase, which is disconnected from the supply network during the measurement.

Of the Invention is based on the object, a control method for a multiphase, electronically commutated motor in the course one of which is very precise and metrologically simple detection of a control-relevant variable, in particular a motor phase current and / or a back EMF voltage and / or a derived therefrom size takes place. The invention is further based on the object, one for carrying out the Specify the method mentioned particularly suitable device.

With regard to the method, the object is achieved by the features of claim 1. Thereafter, it is provided that a motor phase associated, control-relevant variable is determined by detecting the Bestromungszustandes a freewheeling diode, which is arranged within a phase of the motor phase associated half-bridge of a bridge circuit. The Bestromungszustand is in this case during a subsequently referred to as "time" period detected, which is characterized in that one of the freewheeling diode within the phase half-bridge parallel-connected power switch is "on", ie, has a conductive state, while one of the freewheeling diode serially connected power switch one has blocking state.

in the The following is between a "considered Motor phase "and each "further Motor phases "distinguished. By this language regulation is to be expressed that by detection the energization state of a given freewheeling diode always one determining the size of the regulation, which is associated with that motor phase, in the associated Phase half bridge the freewheeling diode is arranged. This engine phase will be below, to distinguish it from the "other Motor phases "as" considered Motor phase ". However, this language is not in the sense of a definition to understand a specific, physical engine phase. Much more is in a preferred embodiment the current status of each freewheeling diode of each phase half-bridge is detected, so that, depending on the reference, each engine phase "considered Engine phase " can.

Of the Bestromungszustand the freewheeling diode is in an appropriate method variant by a direct current sensor, in particular one of the freewheeling diode via its Base-emitter junction serially connected bipolar transistor detected. In one alike preferred alternative process variant is the Bestromungszustand the freewheeling diode, e.g. by means of a comparator circuit, indirectly using an over the freewheeling diode sloping reference voltage determined. Indirect capture the Bestromungszustandes is particularly suitable for comparatively high drive power, especially as the indirect detection of the current state essentially lossless.

These Reference voltage corresponds to recognized (in the forward direction falling) forward voltage of the freewheeling diode when energized is. On the other hand, if the free-wheeling diode is de-energized, then the reference voltage corresponds while the time of the (falling in the reverse direction of the freewheeling diode) saturation voltage of the parallel circuit breaker. The reference voltage thus changes in case of a change the Bestromungszustandes the freewheeling diode the sign, whereby the Bestromungszustand the freewheeling diode and a change the same with circuitry particularly simple and thus especially cost-effective Means is recognizable.

Prefers the energization state of the low potential side, i. of the arranged between a phase terminal and the negative terminal Freewheeling diode of a half-phase bridge certainly. This is particularly useful from the aspect that the negative pole usually is used as the system mass, to which also the control logic a motor control usually is related. in principle but in addition or Alternatively, the energization state of the high potential side Freewheeling diode can be detected.

When becomes regulation-relevant variable in a preferred embodiment of the method, the flow direction of the considered in the engine phase flowing Motor phase current determined. A low potential side arranged Free-wheeling diode is during the At one time recognized then energized when the flow direction of the associated motor phase current positive is, i. when the motor current flows to the motor. at negative flow direction of the motor phase current is the freewheeling diode however, without power. The Bestromungszustand a high potential side freewheeling diode behave exactly opposite to this.

Preferably the energization state of the freewheeling diode is continuously, i. while each one time continuously or time discretely with a predetermined Sample rate monitored, around zero crossings, i.e. Detect flow direction change of the motor phase current. When for one Zero-crossing characteristic quantities become particular here the time at which the zero crossing occurs and optionally detects a sign associated with the zero crossing. A zero crossing is noted positive, if the motor phase current of negative Flow direction to positive flow direction changes. A flow direction change from positive to negative will be defined as a negative zero crossing designated. From the determined zero crossings of the motor phase current will be optionally derived quantities like the frequency of the motor phase current and / or the phase position of the motor phase current determined at any time.

Additionally or alternatively to the flow direction of the motor phase current is in a advantageous embodiment of the procedure as further regulation-relevant size the sign of an in the considered motor phase induced back EMF voltage the Bestromungszustandes the freewheeling diode determined. For this purpose is while a one-time of a considered engine phase, especially after Abkommuteirung of the relevant motor phase current, a so-called zero vector state manufactured in the course of which all motor phases on a common Pole of the voltage intermediate circuit are clamped, so that to the another motor phases, a terminal potential is applied, which is the Terminal potential of the considered engine phase substantially corresponds. If the Bestromungszustand the low potential side freewheeling diode determined, the zero vector state is realized in particular, by clamping all motor phases to the negative pole.

During the the zero pole state related to the negative pole is in the limit of one low motor phase current associated with the considered motor phase Terminal potential opposite the mass potential then positive if the associated back EMF voltage on has positive sign. Accordingly, the low-potential side freewheeling diode in this case de-energized. Conversely, the low potential side Freewheeling diode then energized when the back EMF voltage has a negative sign having.

The Sign of the back EMF voltage can equivalently also be based on the Bestromungszustandes a high potential side freewheeling diode be determined. Here are used to produce the zero vector state all motor phases are clamped on the positive pole. The high potential side freewheeling diode is energized with a positive sign of the back EMF voltage and with a negative sign the back EMF voltage is de-energized.

Prefers are considered regulatory variables both the flow direction of the motor phase current as well as the sign determines the back EMF voltage in the considered motor phase. The Determining the sign of the back-EMF voltage is hereby always advantageous then made, if previously a zero crossing of the motor phase current was detected. Through this with the zero crossing of the motor phase current quasi-simultaneous determination of the sign of the back EMF voltage is simultaneous information about a qualitative phase shift between the motor phase current and the back EMF voltage recovered, i. it can be stated whether the back EMF voltage is lagging or leading the motor current. The information about this qualitative phase shift is in a particular in a synchronous motor advantageous embodiment of the method as a control variable for phase matching of the motor phase current to the back EMF voltage.

Around before producing the zero vector state, the motor current flowing in the motor phase to eliminate, the null vector state expediently preceded by a Abkommutierungszustand. During the Abkommutierungszustandes is the phase half-bridge associated with the considered motor phase has a high impedance connected. In other words, both power switches of this phase half-bridge become temporary locking activated. At the other engine phases is simultaneously a clamping potential applied to the motor phase current in the considered Motor phase counteracts. flows the motor phase current in the considered motor phase thus in positive Flow direction, so is the other motor phases substantially created the operating potential. Accordingly, the others Motor phases grounded when at the beginning of Abkommutierungszustandes the Motor phase current in the considered motor phase in negative flow direction raft.

Regarding the to carry out of the method described above the object is achieved by the features of claim 10. Thereafter, the device comprises a bridge circuit for controlling a multiphase electronically commutated motor. The bridge circuit includes an associated phase half-bridge for each motor phase, in FIG which respect a phase connection terminal a high potential side arranged Circuit breaker and a low potential side arranged circuit breaker are arranged. Each circuit breaker is in this case a freewheeling diode connected in parallel. The device further comprises a control unit, which is designed to control the power switch of the bridge circuit.

According to the invention here is a freewheeling diode at least one phase half-bridge a Assigned sensor circuit, which is adapted during a One time according to the above Definition to determine the Bestromungszustand the freewheeling diode. Of the Control unit is the current from the sensor circuit indicative output value supplied, based on which the control unit after the method described above a control-relevant variable, in particular the flow direction of the motor phase current, the sign of the back EMF voltage or a quantity derived therefrom.

Conveniently, is the sensor circuit of a low potential side arranged Freewheeling diode assigned. The lower potential side is preferred Free-wheeling diode associated with each phase half-bridge, a sensor circuit.

For a direct Measurement of the Bestromungszustandes the freewheeling diode includes the sensor circuit in a preferred embodiment of the invention, a bipolar transistor, via its base-emitter path the freewheeling diode is connected in series. In an alternative execution The invention comprises the sensor circuit for indirect measurement of the Bestromungszustandes a comparator, to capture the above Free-wheeling diode sloping reference voltage an anode-side diode potential and a cathode-side diode potential of the freewheeling diode is supplied.

In a circuitally particularly advantageous embodiment of the invention, the sensor circuit together with the associated freewheeling diode and the latter connected in parallel circuit breaker in a common, in particular integrated monolithic running component, which is realized as a 4-pole, ie in addition to the three inputs of the circuit breaker comprises a sensor circuit associated sensor output, on which the output signal can be tapped. This sensor output is designed in particular as an open-collector output. An open-collector output provides a passive resistance value instead of an active voltage signal to indicate a signal condition.

The associated with the invention Benefits consist in particular in the means of a common Measuring principle, namely the detection of the Bestromungszustandes a freewheeling diode during the for the above-defined one-time characteristic switching state, on circuit technology particularly simple and thus cost-effective way control relevant Sizes like the flow direction of a motor phase current and / or the sign a back EMF voltage can be determined. Such one-times occur in a normal motor control from home and with metrologically sufficiently long duration on, so that in particular the flow direction of the motor phase current unproblematic can be determined during normal operation of the engine. In terms of one Detection of back EMF voltage is as described above Measuring principle in particular advantageous insofar as the measurement of Back EMF voltage during of a zero vector state. Such a zero vector state Typically, at each clock cycle, the power switch is turned on once run through.

to constructive simplification of the control device contributes in particular in that the flow direction of the motor phase current and the sign detects the back EMF voltage with one and the same sensor circuit become. This allows despite simple circuit design a high precision Measurement, so that in particular the comparatively weak, Back EMF voltage caused by the remanent magnetism of the rotor iron An asynchronous motor is measured safely. The procedure and the associated device is also advantageous in a synchronous motor, in particular for phase matching the motor phase currents to the back EMF voltage used.

following Be exemplary embodiments of Invention explained in more detail with reference to a drawing. Show:

1 in a schematically simplified block diagram, a device for controlling a three-phase, electronically commutated motor, with an inverter-side bridge circuit and a controlling this control unit,

2 in an electronic circuit diagram, a power switch and a parallel-connected freewheeling diode of the bridge circuit according to 1 with a sensor circuit designed as a comparator circuit for detecting the energization state of the freewheeling diode,

3 in illustration according to 2 an alternative embodiment of the sensor circuit,

4 to 6 in illustration according to 2 further embodiments of the sensor circuit,

7 in a schematic diagram for each of the three motor phases, the time profile of the motor phase current, the terminal potential and the phase voltage in a so-called "Fiat bottom modulation",

8th in a diagram with opposite 7 refined time scale Time segments Va and Vb of the diagram according to 7 .

9 in illustration according to 7 the time profile of the motor phase currents, terminal potentials and phase voltages in a so-called "centric modulation" and in addition the time course of the back EMF voltage induced in each motor phase,

10 in illustration according to 8th Time segments VIIa and VIIb of the diagram according to 9 in refined time resolution.

each other corresponding parts and sizes are always provided with the same reference numerals in all figures.

1 shows in a schematically simplified block diagram a device 1 for controlling a three-phase, electronically commutated motor 2 , At the engine 2 is an example of a brushless synchronous motor with permanent magnet. The method described below and the associated device 1 but are also used to control other types of motors, especially in an asynchronous motor or a reluctance synchronous motor.

The device 1 includes an inverter-side bridge circuit 3 that from a DC source 4 via a voltage intermediate circuit 5 is supplied with electricity. The bridge circuit 3 includes three phase half bridges 6a . 6b . 6c , which in parallel between each positive pole 7 and a negative pole 8th of the voltage intermediate circuit 5 are switched. Each phase half-bridge 6a . 6b . 6c has a phase at a tap connecting terminal 9a . 9b . 9c on. The phase connection terminal 9a . 9b . 9c and the positive pole 7 is within the respective phase half-bridge 6a . 6b . 6c a high potential side circuit breaker 10a . 10b . 10c interposed. Likewise, the respective phase connection terminal 9a . 9b . 9c and the negative pole 8th within the respective phase half-bridge 6a . 6b . 6c a low potential side circuit breaker 11a . 11b . 11c interposed. The circuit breakers 10a . 10b . 10c and 11a . 11b . 11c are designed as semiconductor switching elements, in particular IGBTs or MOFETs. Each high potential side circuit breaker 10a . 10b . 10c is a high-potential side freewheeling diode 12a . 12b . 12c connected in parallel. Likewise, each low potential side circuit breaker 11a . 11b . 11c an associated low potential side freewheeling diode 13a . 13b . 13c connected in parallel. The freewheeling diodes 12a . 12b . 12c and 13a . 13b . 13c are each with their forward direction to the positive pole 7 aligned and thus with respect to the potential gradient between positive pole 7 and negative pole 8th switched in the reverse direction.

With the phase connection terminal 9a . 9b . 9c each phase half-bridge 6a . 6b . 6c is an associated engine phase 15a . 15b . 15c of the motor 2 contacted, which is here exemplified in star connection. Every engine phase 15a . 15b . 15c includes a field winding 16a . 16b . 16c in a stator 17 of the motor 2 is arranged. The motor phases 15a . 15b . 15c are inside the stator 17 in a star point 18 together. The motor 2 further includes an inside of the stator 17 rotatably mounted rotor 19 in particular comprising a permanent magnet (not shown).

The device 1 further comprises a control unit 20 , which is designed in particular as a logical electronic circuit. The control unit 20 includes a switching module 21 for controlling or controlling the circuit breaker 10a . 10b . 10c and 11a . 11b . 11c , The switching module 21 this is via a corresponding control line 22 with the gate input of each circuit breaker 10a . 10b . 10c and 11a . 11b . 11c connected.

For determining a controlled variable R (described in more detail below), the control unit comprises 20 furthermore an evaluation module 23 , The evaluation module 23 In this case, the controlled variable R is designed on the basis of the (currentless or current-carrying) energization state Z of each freewheeling diode on the low potential side 13a . 13b . 13c to determine. For detecting the energization state Z, each of the low potential side freewheeling diodes 13a . 13b . 13c a sensor circuit 24a . 24b . 24c associated with the current state Z specifying output signal S _Z via a respective detection line 25 the evaluation module 23 supplies. The evaluation module 23 and switching module 21 are connected to exchange control signals S _C.

A low potential side circuit breaker 11 , which is exemplary for any circuit breaker 11a . 11b . 11c according to 1 is in the 2 and 3 together with the freewheeling diode connected in parallel 13 (corresponding to one of the free-wheeling diodes 13a . 13b . 13c out 1 ) and the associated sensor circuit 24 (corresponding to one of the sensor circuits 24a . 24b . 24c out 1 ) shown enlarged. The sensor circuit 24 is in a first embodiment according to 2 designed as a comparator circuit. The sensor circuit 24 hereby includes a comparator 30 , over his entrances 31 and 32 the respective freewheeling diode 13 is connected in parallel, so the input 31 with an anode-side diode potential φ_ and the input 32 is occupied by a cathode-side diode potential φ ₊ . The comparator 30 compares the applied diode potentials φ _- and φ ₊ and outputs at one output 33 the output signal S _Z in the form of a logic signal whose value of the size ratio of the diode potentials φ _- and φ ₊ , and thus the sign of one over the freewheeling diode 13 decreasing reference voltage U _R = (φ ₊ - φ _- ) depends. The energization state Z is determined indirectly via the sign of the reference voltage U _R. Is the freewheeling diode 13 energized, the reference voltage U _R corresponds to the forward voltage and thus negative forward voltage of the freewheeling diode 13 , Is the freewheeling diode 13 de-energized, so the falling over her reference voltage U _{R is} positive.

The sensor circuit 24 is optional together with the switching module 21 in a common driver block 34 integrated. In this embodiment, the diode potentials φ _- and φ _{+ are} at a "COM" input 35 or a "Vs" input 36 of the driver block 34 created, the building block internally with the entrances 31 respectively. 32 of the comparator 30 are contacted. The output signal S _Z is at one with the output 33 of the comparator 30 interconnected "Sign" output 37 of the driver block 34 tapped. An "LO" input 38 of the driver block 34 is via the associated control line 22 to the gate input of the low potential side circuit breaker 11 connected. A "HO" input 39 of the driver block 34 is corresponding to the gate input of the (in 2 not shown) associated high-potential side circuit breaker 10a . 10b . 10c connected. The inputs 38 u. 39 are (in a manner not shown) within the building block with the switching module 21 connected.

In an alternative embodiment of the sensor circuit 24 according to 3 becomes the Bestromungszustand Z of the freewheeling diode 13 measured directly. For this purpose, the freewheeling diode 13 a bipolar transistor 40 above its base-emitter route 41 connected in series. The output signal S _Z is in this case at a center tap 42 a voltage divider circuit 43 tapped, which has a resistance 44 with a supply potential VCC and a resistor 45 with a collector entrance 46 of the bipolar transistor 40 connected is. The base-emitter line 41 of the bipolar transistor 40 in this case even has the circuit properties of a same direction with the freewheeling diode 13 aligned diode. The bipolar transistor 40 can thus with appropriate design, the freewheeling diode 13 also completely replace.

Optional are the circuit breaker 11 , the freewheeling diode 13 and the bipolar transistor 40 in a common electronic component 47 combined. The component 47 is designed as a 4-pole. It includes three the circuit breaker 11 assignable connections 48 . 49 and 50 of which the connection 48 for connection to the negative pole 8th , the connection 49 as control input for connection to the switching module 21 and the connection 50 for connection to the respective motor phase terminal 9a . 9b . 9c is provided. The component 47 further includes a sensor output 51 , with the collector entrance 46 of the bipolar transistor 40 connected is. The sensor output 51 has the circuit properties of an open-collector output and provides a highly sensitive of the Bestromungszustand the base-emitter path 41 , and thus of the Bestromungszustand Z of the freewheeling diode 13 dependent resistance value available. The component 47 is preferably monolithic. The representation of the bipolar transistor 40 In this case, it does not represent a separate part, but a circuit-technical characteristic of the component 47 ,

Further embodiments of the sensor circuit 24 are in the 4 to 6 shown. In contrast to the embodiments described above according to 2 and 3 is the sensor circuit 24 here in each case from the low potential side circuit breaker 11 and the associated freewheeling diode 13 formed semiconductor device and the negative pole 8th interposed.

In operation of the engine 2 is achieved by commutation of the motor phases 15a . 15b . 15c , ie by periodic opening or closing of the circuit breaker 10a . 10b . 10c and 11a . 11b . 11c in every engine phase 15a . 15b . 15c generates a periodically fluctuating motor phase current I _a , I _b , I _c , wherein - as in 1 indicated - the motor phase current I _{a of} the motor phase 15a , the motor phase current I _{b of} the motor phase 15b and the motor phase current I _{c of} the motor phase 15c assigned. The motor phase currents I _a, I _b, I _c generate in the stator 17 of the motor 2 a rotating magnetic field exciting the rotor 19 drives. One within a motor phase 15a . 15b . 15c on the engine 2 incoming motor phase current I _a , I _b , I _c is noted below with a positive sign. A positive motor phase current I _a , I _b , I _c thus flows along a in 1 indicated flow direction 55 , Accordingly, one of the engine 2 wegfließender motor phase current I _a , I _b , I _{c recorded} with a negative sign. A corresponding motor phase current I _a , I _b , I _c thus flows in one of the flow direction 55 opposite flow direction.

To control the phase currents I _a , I _b , I _c is by raising or Zuseituerung the circuit breaker 10a . 10b . 10c and 11a . 11b . 11c a terminal potential φ _a , φ _b , φ _c at the respectively associated phase terminal 9a . 9b . 9c set.

The high potential side circuit breaker 10a . 10b . 10c and the associated low potential side circuit breaker 11a . 11b . 11c each phase half-bridge 6a . 6b . 6c These are - unless explicitly stated otherwise - always antiparallel driven, so that within each phase half-bridge 6a . 6b . 6c one circuit breaker each 10a . 10b . 10c respectively. 11a . 11b . 11c has a conductive state while the other power switch 10a . 10b . 10c respectively. 11a . 11b . 11c has a blocking state. Is the high potential side circuit breaker 10a . 10b . 10c a phase half-bridge 6a . 6b . 6c conductive, so the associated terminal potential φ _a , φ _b , φ _c corresponds essentially to the positive pole 7 assigned operating potential φ _B. In contrast, is the low-potential side circuit breaker 11a . 11b . 11c conductive, the associated terminal potential φ _a , φ _b , φ _c corresponds approximately to one at the negative pole 8th tappable mass potential φ _M. A change of the switching state within a phase half-bridge 6a . 6b . 6c is usually quasi-simultaneous for both circuit breakers 10a . 10b . 10c and 11a . 11b . 11c , more precisely, within the dead time introduced at the beginning, which is negligible due to its short duration for the subsequent embodiments. The control of the motor phases I _a , I _b , I _c is through the switching module 21 using pulse width modulation (PWM). In this case, the high-potential side circuit breaker 10a . 10b . 10c the motor phase to be controlled 15a . 15b . 15c by a series of control pulses P ( 7 ), which follow one another at a predetermined clock frequency. The duration of each control pulse P, referred to as the pulse width, is modulated between 0% and 100% of the clock duration of a PWM clock in the course of the control method. For the following on the control pulse P period of a PMW clock is the high potential side circuit breaker 10a . 10b . 10c switched off, and the associated motor phase 15a . 15b . 15c by controlling the corresponding low potential side circuit breaker 11a . 11b . 11c on the negative pole 8th clamped. At the in 1 illustrated circuit configuration corresponds to a Period of time characterized by this switching state of a one-time within the meaning of the above definition.

As the phase voltage U _a , U _b , U _c below the time average of the corresponding terminal potential formed on the PWM clock φ _a , φ _b , φ _c is referred to. Each phase voltage U _a , U _b , U _c is based on the ground potential φ _M and varies between 0V and the operating potential φ _B. The phase voltage U _a , U _b , U _c is in this case directly proportional to the pulse width, with which the corresponding motor phase 15a . 15b . 15c is controlled.

In practice, different variants of the pulse width modulated motor control are used, to which the inventive method is equally applicable. Exemplary is in 7 a so-called "Fiat Bottom" modulation shown. 7 shows in a graph against the time t for each engine phase 15a . 15b . 15c separates the respective motor phase current I _a , I _b , I _c , the associated terminal potential φ _a , φ _b , φ _c and the respective phase voltage U _a , U _b , U _c .

According to the diagram 7 It can initially be seen that the phase currents I _a , I _b , I _c vary periodically according to an at least substantially sinusoidal time dependence. The period of this sinusoidal time dependence corresponds to a full rotation of the excitation field, and - in a synchronous motor with N Polpaaren- a N-th rotation of the rotor 19 , A time interval within the diagram is thus directly proportional to a change in the phase angle of the exciter field or the rotor movement.

For the "Fiat Bottom" modulation according to 7 every engine phase 15a . 15b . 15c during a first subcycle corresponding to a phase angle range of 240 ° 60 controlled pulse width modulated each period. This subcycle 60 in the illustration according to 7 at the respective one control pulse P corresponding peaks of the terminal potentials φ _a , φ _b , φ _c to recognize, for reasons of limited time resolution in 7 neglecting their respective temporal extent, they are merely indicated as vertical bars. As can be seen from the corresponding profile of the respective phase voltage U _a , U _b , U _c , the pulse width of the control pulses P proportional thereto decreases in the course of the first half of the subcycle 60 to, goes through two maxima and decreases in the second half of the subcycle 60 again. To the subcycle 60 closes a second subcycle 61 which corresponds to a phase angle range of 120 ° and thus completes the period, ie with the sub-cycle 60 to a full cycle, corresponding to a phase angle range of 360 °. During the subcycle 61 is the respective engine phase 15a . 15b . 15c permanently clamped to the mass potential φ _M. The phase voltage U _a , U _b , U _c corresponds during this subcycle 61 the associated terminal potential φ _a , φ _b , φ _c .

The following is an example of the motor phase 15a limited consideration of the behavior of the terminal potential φ _a at a zero crossing of the associated motor phase current I _a explained in more detail. In this case, a zero crossing is referred to as a positive zero crossing, in which the flow direction changes from negative to positive. Such a positive zero crossing occurs according to 7 within the marked time segment Va. A negative zero crossing is a zero crossing of the motor phase current I _a at which the flow direction changes from positive to negative. Such a negative zero crossing occurs within the marked time segment Vb.

These time segments Va and Vb are in 8th shown again in a refined time resolution. 8th In particular, it can be seen that a base value L, which the terminal potential φ _a assumes during each onetime T, is determined by the direction of flow or the sign of the associated motor phase current I _a . For the according 8th At a time instant t ₁ , the positive zero crossing is the base value L of the terminal potential φ _a before the zero crossing slightly positive, then slightly negative. In accordance with 8th At a time t ₂ occurring negative zero crossing, the terminal potential φ _a behaves opposite, thus has a slightly negative value before the zero crossing and a slightly positive value after the zero crossing.

The base value L of the terminal potential φ _a is in this case by the Bestromungszustand Z of the freewheeling diode 13a certainly. As a result of continuity, that is, the inductively induced "inertia" of the motor phase current I _a flows the motor phase current _Ia at a negative direction during the on-time flow through the power switch 11a from. The motor phase current I _a is in the reverse direction of the freewheeling diode 13a directed, which is thus de-energized. As _a result, the terminal potential φ _a has one of the saturation voltage of the circuit breaker with respect to the ground potential φ _M 11a corresponding positive value. In the positive flow direction, the current flow is in the forward direction of the freewheeling diode 13a directed, which is thus energized. As a result, the base value L of the terminal potential φ _a is one of the forward voltage of the freewheeling diode 13a corresponding amount to the mass potential φ _M and thus in particular negative.

The Bestromungszustand Z of the freewheeling diode 13a or the conditional on it dependence of the base value L of the terminal potential φ _a is exploited according to the method to the flow direction, and in particular to determine zero crossings of the motor phase current I _a .

As turn out 8th can be seen, a positive zero crossing of the motor phase current I _a always takes place during a control pulse P. In this case, the zero crossing is determined on the basis of the change in the base value L between a onetime T ₁ immediately preceding the zero crossing and a subsequent onetime T ₂ . The detection of the zero crossing is thus carried out in particular at a beginning of the onetime T ₂ characterizing time t ₃ and thus with a slight time shift relative to the exact time t _{1 of} the zero crossing.

A negative zero crossing occurs during the subcycle 61 , which represents a one-time T ₃ in the sense of the above definition due to the associated switching state over its entire length. The zero crossing is therefore detected with the accuracy specified by the sampling rate of the current state Z directly at time t ₂ .

Another example of a pulse width modulated motor drive, to which the method according to the invention can be applied, is in 9 (in to 7 analog representation). This is a so-called "centric modulation" in which each motor phase 15a . 15b . 15c is clocked via the full cycle of the phase angle. As can be seen from the respective phase voltage U _a , U _b , U _c , the pulse width of the control pulses P varies in each motor phase 15a . 15b . 15c by way of example according to a sinusoidal time dependence with the period of the motor phase currents I _a , I _b , I _c . In addition to the motor phase currents I _a , I _b , I _c , the phase voltages U _a , U _b , U _c and the terminal potentials φ _a , φ _b , φ _c is in 9 the time course of a back-EMF voltage V _a , V _b , V _c entered by the counterelectromotive force (back EMF) of the rotor 19 in every engine phase 15a . 15b . 15c is induced. The in the engine phases 15a . 15b . 15c induced back EMF voltages V _a , V _b , V _c are on the possibly virtual star point 18 referred to as common reference potential. In the illustration according to 9 the back-EMF voltage V _a , V _b , V _c slightly behind the respective associated motor phase current I _a , I _b , I _c .

A variant of the method according to (again by way of example with reference to the motor phase 15a considered) by detecting the Bestromungszustandes Z of the freewheeling diode 13a the sign of the back EMF voltage V _a , V _b , V _c , and in particular their qualitative (ie positive or negative) phase shift relative to the associated motor phase current I _a , I _b , I _{c is} determined, is below with reference to 9 and 10 explained in more detail. In the latter figure are analogous to 8th Time segments VIIa and VIIb of the diagram according to 9 , which correspond to a positive or negative zero crossing of the exemplary considered motor phase current I _a , shown in more refined time resolution.

The back EMF voltage V _a , V _b , V _{c of} a motor phase 15a . 15b . 15c can be measured as soon as passing through the inductance of the exciter windings 16a . 16b . 16c driven current flow has subsided, and the residual current in a motor phase 15a . 15b . 15c in the case of short-circuited phase terminals 9a . 9b . 9c by the back EMF voltage V _a , V _b , V _{c of} the considered motor phase 15a . 15b . 15c is driven.

The determination of the sign of the back-EMF voltage V _a is effected by a so-called zero vector state N to the motor phases during a measuring time T _M 15a . 15b . 15c is created. For this purpose, the circuit breaker is triggered 11a . 11b . 11c not just the considered engine phase 15a , but also the other engine phases 15b and 15c clamped to the mass potential φ _M. During the zero vector state N, the freewheeling diode is 13a then energized if the back EMF voltage V _A is negative, and as a result the terminal potential φ _a ground potential φ _M below. If the back EMF voltage V _{a is} positive, then the freewheeling diode 13a de-energized.

Accordingly, during the according to 10 measured within the time segment VIIa measuring time T _m due to the negative back-EMF voltage Va a negative base value L measured or the current-carrying current state Z of the freewheeling diode 13a detected as an indication of the negative sign of the back EMF voltage V _a .

In contrast, during the measuring time T _M connected within the time segment VIIb, a positive base value L of the terminal potential φ _a or the currentless energization state Z of the freewheeling diode is generated 13a detected as the positive sign of the back EMF voltage V _a .

The detection of the back EMF voltage V _a is in each case upon detection of a zero crossing of the associated motor phase current I _a , and thus at a time at which the current flow in the considered motor phase 15a from home is particularly low, made. In order to eliminate the residual current, the application of the zero vector state N becomes a commutation state A in the motor phase 15a upstream. In the course of Abkommutierungszustandes A, the phase half-bridge 6a by shading both circuit breakers 10a and 11a switched high impedance. The terminal potentials φ _b and φ _{c of} the other motor phases 15b and 15c who at the same time set to a value that the current flow in the considered motor phase 15a counteracts.

Immediately after recognition of the occurring within the time segment VIIa positive zero crossing of the motor phase current I _a , the other motor phases accordingly 15b . 15c clamped to the operating potential φ _B. The successful Abkommutierung the motor phase current I _a can be seen in this case that the freewheeling diode 13a is de-energized and accordingly the terminal potential φ _{a increases} from a negative value to a value approximately corresponding to the operating potential φ _B.

Immediately after detection of the occurring during the time segment VIIb negative zero crossing of the motor phase current I _a , the other motor phases 15b and 15c in contrast, in the course of the Abkommutierungszustandes A to the ground potential φ _M clamped. The Abkommutierungsvorgang manifests itself in this case, that directly with the blocking of the two circuit breakers 10a and 11a the phase half-bridge 6a The terminal potential φ _a increases abruptly to a substantially the operating potential φ _B corresponding value and with the drying of the motor phase current I _a falls back to a low value. In this case, the detection of the Bestromungszustandes Z for determining the back-EMF voltage V _a already during Abkommutierungszustandes A begin as soon as the motor phase current I _{a has} dropped.

The inventive method is accordingly applicable to other common types of pulse width modulated Motoransteurung, in particular to a so-called block commutation. Optionally continue to be, for example, after a itself from the US 6,249,094 known methods, the back EMF voltages V _a , V _b , V _c also determined quantitatively.

In operation of the engine 2 detects the evaluation unit 23 during each onetime T of each phase half-bridge 6a . 6b . 6c that of the corresponding sensor circuit 24a . 24b . 24c certain Bestromungszustand Z of the corresponding freewheeling diode 13a . 13b . 13c , The detection of the energization state Z takes place at least once per one-time T. The evaluation unit 23 is in this case via the control signal S _C from the switching module 21 correspondingly "triggered." Detects the evaluation module 23 after in connection with the 7 and 8th described procedure, a zero crossing of a phase current I _a , I _b , I _c , it determines according to the in connection with the 9 and 10 described procedure, the sign of the back EMF voltage V _a , V _b , V _c . The evaluation module initiates this 23 the switching module 21 by outputting corresponding control signals S _C for generating the Abkommutierungszustandes A and for generating the zero vector state N.

On the basis of the flow direction or the sign of the motor phase currents I _a , I _b , I _c and / or back-EMF voltages V _a , V _b , V _c and optionally based on derived therefrom zero crossings of these variables, the evaluation module 23 the controlled variable R and transmits this to the switching module 21 ,

The controlled variable R is, in particular, the times associated with a zero crossing of the phase currents I _a , I _b , I _c and / or the back-EMF voltages V _a , V _b , V _c , which are the switching module 21 be supplied in the form of a trigger signal. Alternatively, the controlled variable R is a quantity derived therefrom, in particular the rotational speed, or a qualitative or quantitative measure for the phase shift between a motor phase current I _a , I _b , I _c and the associated back EMF voltage V _a , V _b , V _c . The speed is determined by determining the time interval between successive zero crossings. As a qualitative measure of said phase shift, the sign of the back EMF voltage V _a , V _b , V _c at the time of a zero crossing of the associated motor phase current I _a , I _b , I _c transmitted.

The switching module 21 controls the bridge circuit 3 in particular in such a way that the actual speed supplied as control variable R is calibrated to a predetermined desired speed. Optionally, the drive is additionally or alternatively made such that the actual phase shift between the motor currents I _a , I _b , I _c and the associated back-EMF voltages V _a , V _b , V _c , which is levied as a further controlled variable R, is minimized in terms of amount ,

Concrete embodiments of such control algorithms are known per se and, for example, in the documents US 6,249,094 B1 . US 6,208,112 B1 and US 6,121,736 A described.

A special application of the method described is the reliable detection of the speed of a permanent magnet synchronous motor or an asynchronous motor in the outlet or other control-free freewheeling phase. During such a freewheel, one or more of the circuit breakers 11a . 11b . 11c permanently open. In this case, under the effect of the back-EMF circulating currents through the short-circuited motor phases 15a . 15b . 15c generated, by which a braking torque on the rotor 19 is exercised. Also with an asynchronous motor exists due to the remanence magnetism in the rotor iron one, albeit much weaker back-EMF compared to a permanent magnet synchronous motor. Especially since the current state Z is a very sensitive measure of the freewheeling diodes 13a . 13b . 13c voltage conditions present, even the very weak back EMF of an asynchronous motor can be measured safely. If necessary, in this case, the remanence magnetism of the rotor iron is refreshed by a stator pulse preceding the freewheeling phase in order to amplify the amplitude of the back-EMF voltages V _a , V _b , V _c . In this way, in particular in the outlet, the speed of the motor 2 be tracked almost to a standstill. This functionality is useful to the safe stop of the engine 2 to recognize.

1

contraption

2

engine

3

bridge circuit

4

DC voltage source

5

Voltage link

6a-6c

Phase half bridge

7

positive pole

8th

minuspol

9a-9c

Line clamp

10a-10c

(High potential side) breakers

11 11a-11c

(Low potential side) breakers

12a-12c

(High potential side) Freewheeling diode

13 13a-13c

(Low-potential side) Freewheeling diode

15a-15c

motor phase

16a-16c

excitation winding

17

stator

18

star point

19

rotor

20

control unit

21

switching module

22

control line

23

evaluation module

24 24a-24c

sensor circuit

25

sense line

30

comparator

31

entrance

32

entrance

33

output

34

driver module

35

"COM" input

36

"Vs" input

37

"Sign" input

38

"LO" input

39

"HO" input

40

bipolar transistor

41

Base-emitter path

42

center tap

43

Voltage divider circuit

44

resistance

45

resistance

46

Pannel

47

component

48

connection

49

connection

50

connection

51

sensor output

55

flow direction

60

subcycle

61

subcycle

φ _- , φ _-

diodes potential

φ _a , φ _b , φ _c

terminal potential

φ _B

operating potential

φ _M

ground potential

A

Abkommutierungszustand

I _a , I _b , I _c

Motor phase current

L

base value

N

Zero vector state

P

control pulse

R

controlled variable

S _C

control signal

S _Z

output signal

t

Time

t ₁ , t ₂ , t ₃

time

T ₁ , T ₂ , T ₃

on-time

T _M

measuring time

U _a , U _b , U _c

phase voltage

U _R

reference voltage

V _a , V _b , V _c

Back-EMF voltage

VCC

supply potential

Z

energization

Claims (15)

Method for controlling a device using an inverter-side bridge circuit ( 3 ) commutated, several motor phases ( 15a . 15b . 15c ) having engine ( 2 ), characterized in that for determining a control-relevant variable of a considered engine phase ( 15a . 15b . 15c ) the Bestromungszustand (Z) of a freewheeling diode ( 13 . 13a . 13b . 13c ), which in one of the considered engine phases ( 15a . 15b . 15c ) associated phase half-bridge ( 6a . 6b . 6c ) of the bridge circuit ( 3 ) is detected during a one-time (T, T ₁ , T ₂ , T ₃ ) is detected in which one of the freewheeling diode ( 13 . 13a . 13b . 13c ) parallel circuit breaker ( 11 . 11a . 11b . 11c ) of the phase half-bridge ( 6a ) a conductive state, and one of the freewheeling diode ( 13 . 13a . 13b . 13c ) serially connected circuit breaker ( 10a . 10b . 10c ) has a blocking state. A method according to claim 1, characterized in that the current state (Z) of the freewheeling diode ( 13 . 13a . 13b . 13c ) by means of an over the freewheeling diode ( 13 . 13a . 13b . 13c ) falling reference voltage (U _R ) is determined. A method according to claim 1 or 2, characterized characterized in that the freewheeling diode ( 13 . 13a . 13b . 13c ), whose Bestromungszustand (Z) is determined, within the considered engine phase ( 15a . 15b . 15c ) associated phase half-bridge ( 6a . 6b . 6c ) with respect to a phase terminal ( 9a . 9b . 9c ) is arranged on the low potential side. Method according to one of claims 1 to 3, characterized in that as a control-relevant variable on the basis of the Bestromungszustandes (Z), the flow direction of a considered in the engine phase ( 15a . 15b . 15c ) flowing motor phase current (I _a , I _b , I _c ) is determined. A method according to claim 4, characterized in that for the determination of zero crossings of the motor phase current (I _a , I _b , I _c ) of the energization state (Z) of the freewheeling diode ( 13 . 13a . 13b . 13c ) is continuously monitored, wherein a zero crossing is detected by a change in the current state (Z). Method according to one of claims 1 to 5, characterized in that as control-relevant variable based on the Bestromungszustandes (Z), the sign of one of the engine ( 2 ) into the considered engine phase ( 15a . 15b . 15c ) induced back EMF voltage (V _a , V _b , V _c ) is determined by a zero vector state (N) with respect to a motor phase ( 15a . 15b . 15c ) applied terminal potential (φ _a , φ _b , φ _c ) and further each to one of the other motor phases ( 15a . 15b . 15c ) applied terminal potentials (φ _a , φ _b , φ _c ) is produced. A method according to claim 6, characterized in that the determination of the sign of the back-EMF voltage (V _a , V _b , V _c ) upon detection of a zero crossing of the motor phase current (I _a , I _b , I _c ) in the considered motor phase ( 15a . 15b . 15c ) is made. Method according to Claim 6 or 7, characterized in that, before the zero-state state (N) is produced for commutation of the motor current (I _a , I _b , I _c ) in the considered motor phase ( 15a . 15b . 15c ) a Abkommutierungszustand (A) is brought about, in which the motor phase under consideration ( 15a . 15b . 15c ) associated phase half-bridge ( 6a . 6b . 6c ) is switched to high impedance and to the other motor phases ( 15a . 15b . 15c ) the motor phase current (I _a , I _b , I _c ) in the considered motor phase ( 15a . 15b . 15c ) counteracting terminal potential (φ _a , φ _b , φ _c ) is applied. Method according to one of claims 6 to 8, characterized in that based on a flow direction change of the motor phase current (I _a , I _b , I _c ) and the sign of the back-EMF voltage (V _a , V _b , V _c ) at this time (t ₁ , t ₂ ) a phase shift between the motor phase current (I _a , I _b , I _c ) and the back-EMF voltage (V _a , V _b , V _c ) is determined as a controlled variable (R). Contraption ( 1 ) for controlling a multiphase, electronically commutated motor ( 2 ), with an inverter-side bridge circuit ( 3 ) within which each engine phase ( 15a . 15b . 15c ) a phase half-bridge ( 6a . 6b . 6c ) associated with a phase terminal ( 9a . 9b . 9c ) high-potential side circuit breaker ( 10a . 10b . 10c ) and one with respect to the phase terminal ( 9a . 9b . 9c ) low potential side arranged circuit breaker ( 1l . 11a . 11b . 11c ), and one each of each circuit breaker ( 10a . 10b . 10c . 11 . 11a . 11b . 11c ) parallel-connected freewheeling diode ( 12a . 12b . 12c . 13 . 13a . 13b . 13c ) and a control unit ( 20 ) for controlling the circuit breaker ( 10a . 10b . 10c . 11 . 11a . 11b . 11c ) of the bridge circuit ( 3 ), characterized in that a freewheeling diode ( 13 . 13a . 13b . 13c ) at least one phase half-bridge ( 6a . 6b . 6c ) a sensor circuit ( 24 . 24a . 24b . 24c ), which is adapted, during a one-time (T, T ₁ , T ₂ , T ₃ ), in which one of the freewheeling diode ( 13 . 13a . 13b . 13c ) parallel circuit breaker ( 13 . 13a . 13b . 13c ) a conductive state, and one of the freewheeling diode ( 13 . 13a . 13b . 13c ) serially connected circuit breaker ( 12a . 12b . 12c ) has a blocking state, a Bestromungszustand (Z) of the freewheeling diode ( 13 . 13a . 13b . 13c ) for detecting a control-relevant quantity of the considered engine phase ( 15a ) to investigate. Contraption ( 1 ) according to claim 10, characterized in that the or each sensor circuit ( 24 . 24a . 24b . 24c ) with respect to the associated phase connection terminal ( 9a . 9b . 9c ) low potential side mounted freewheeling diode ( 13 . 13a . 13b . 13c ) assigned. Device (10) according to claim 10 or 11, characterized in that the sensor circuit ( 24 . 24a . 24b . 24c ) a comparator ( 30 ), to which an anode-side diode potential (φ _- ) and a cathode-side diode potential (φ ₊ ) of the freewheeling diode ( 13 . 13a . 13b . 13c ) is supplied as input potential. Contraption ( 1 ) according to claim 10 or 11, characterized in that the sensor circuit ( 24 . 24a . 24b . 24c ) a bipolar transistor ( 40 ) via its base-emitter path ( 41 ) of the freewheeling diode ( 13 . 13a . 13b . 13c ) is connected in series. Contraption ( 1 ) according to one of claims 10 to 13, characterized in that the sensor circuit ( 24 . 24a . 24b . 24c ) together with the associated freewheeling diode ( 13 . 13a . 13b . 13c ) and the that of this parallel circuit breaker ( 11 . 11a . 11b . 11c ) in a common component ( 47 ) are integrated. Contraption ( 1 ) according to claim 14, characterized in that one of the sensor circuit ( 24 . 24a . 24b . 24c ) and a the energization state (Z) of the freewheeling diode ( 13 . 13a . 13b . 13c ) indicative output signal (S _Z ) providing the sensor output ( 51 ) of the component ( 47 ) is designed as an open collector output.