CN115088181A - Method for operating an electric machine - Google Patents

Abstract

The invention relates to a method for operating an electric machine by means of an inverter having a power half-bridge for generating a phase voltage for each phase of the electric machine, wherein the power half-bridges are controlled in a block-commutated manner by generating a control signal (S) for the power half-bridges in the inverter _U 、S _V 、S _W ) Wherein the converter receives a clock signal (S) _T ) Said clock signal containing information about said steering signal (S) _U 、S _V 、S _W ) Switching information (I) of the switching time point of (2) _U ) And wherein in the converter is based on the clock signal (S) _T ) And a handover message contained thereinInformation (I) _U ) Switching the control signal (S) _U 、S _V 、S _W ) And to such a converter.

Description

Method for operating an electric machine

Technical Field

The invention relates to a method for operating an electric machine by means of a converter (Stromrichter), to a converter, to a system having a converter and a computing unit, and to a computer program for carrying out the method.

Background

In the field of low-cost motor bicycles or motorcycles with a typical small internal combustion engine, permanently excited synchronous generators can be used, which are rigidly coupled to the crankshaft of the internal combustion engine. These generators are used to supply electrical energy to an electrical system (with a battery, control device(s), ignition device, injection device, etc.). The generator can be designed such that the maximum energy requirement of the electrical system can be provided at any time. This means that in many operating points more electrical energy is provided by the generator than is needed.

When the electric power is excessively supplied in the operating point, it is necessary to prevent overcharge of the battery. Since it is not possible to change the excitation (as in the case of externally excited electrical machines) or the rotational speed, the generator can be decoupled from the other components of the electrical system and placed in an electrical idle or short circuit for this purpose. In the case of electrical idle, the generator rotates synchronously with the internal combustion engine without stressing it in a noteworthy manner. In the event of a short circuit, the electrical energy formed is converted into heat and thereby loads the internal combustion engine in a parasitic manner. Since very high voltages (proportional to the rotational speed) can occur in electrical freewheeling, short-circuit solutions can be preferred and the resulting power losses can be tolerated.

It is possible in the field to typically use single-phase and three-phase generators, but other numbers of phases are possible. Common power levels move between 150W and 500W (for an output voltage corresponding to the battery voltage) depending on the design and energy requirements of the electrical system.

In the case of a small internal combustion engine, for example for a motorbike, the generator can combine three functions. In addition to the electrical energy for the electrical system, a rotor of large implementation can provide a rotating mass for stabilizing the operating behavior of the internal combustion engine. Furthermore, in most cases metallic markings ("teeth") may be located on the rotor, which markings thus represent the sensing wheel and, together with a rotational speed sensor, may generate rotational speed and crankshaft position signals for the motor control device. The rotational speed and crankshaft position signals are necessary for operating modern internal combustion engines by means of electronic motor control devices. For example, the rotational speed of the sensor wheel is detected by the sensor wheel, for example using an inductively acting sensor or a hall sensor. The sensor then records the passing metal mark ("tooth") and determines the rotation speed from the time difference between the two marks.

In order to perform the crank angle synchronization function, the absolute position of the crankshaft can furthermore be detected in order, for example, to correctly determine the time points for injection and ignition (in the case of a gasoline motor). This can be achieved by means of a tooth gap on the sensor wheel, which can be identified by means of the rotational speed sensor and thus assigned to a defined crank angle.

Disclosure of Invention

According to the invention, a method for operating an electric machine, a converter, a system with a converter and a computing unit and a computer program for carrying out the method are proposed with the features of the independent patent claims. Advantageous embodiments are the subject matter of the dependent claims and the following description.

The invention relates to the operation of an electric machine, in particular a permanently excited electric machine, by means of a converter having a power half-bridge for generating a phase voltage for each phase of the electric machine. The power half-bridge can comprise two semiconductor switches or power switches, for example MOSFETs or IGBTs, one of which is usually referred to as a high-side switch and the other as a low-side switch, and can be connected to the positive or negative pole terminal of the electrical system, respectively.

In the case of a three-phase motor, three power half-bridges can thus be provided. However, even if a three-phase motor is used for illustration within the scope of the invention, the invention is also applicable to motors having other numbers of phases.

By using such a converter (in particular also referred to as inverter or inverter) instead of a rectifier voltage regulator, the electrical machine can be operated both as a generator and as a motor, as a result of which the efficiency of the electrical energy production can be increased and the drive train can be mixed at least to a weak extent.

In order to actuate the converter or inverter in accordance with the respective torque request and to operate the electric machine optionally as a motor or generator, at least one digital actuation signal can be output for each power half-bridge via a computing unit or a control device. Depending on the logic level of the control signal, the upper (high level) or lower (low level) power switch of a power half-bridge can be switched on by suitable circuitry (e.g., a gate driver) and the other power switch can be switched off accordingly. Accordingly, a digital steering signal is required for each power half-bridge. In the case of a three-phase motor, three control lines are therefore required.

In order to be able to carry out the respective torque request, the inverter must output a voltage signal for the stator which leads or lags the current position of the rotor. Accordingly, the current rotor position and thus the crankshaft position in the case of a rotor rigidly mounted on the crankshaft are required for generating the control signal.

Since the crankshaft position for operating the internal combustion engine is already present as a measured variable in the electric motor control device, it is expedient to also use this control device for controlling the converter, and thus to achieve a hybridization without a second control device or a rotor position sensor system, which is only required for the electric machine.

However, as long as suitable circuits for the inverter are not integrated (or cannot or should not be integrated) into the motor control device, three control lines (or generally one for each phase) must be provided between the inverter and the control device for this purpose.

Against this background, it is now proposed within the scope of the invention that the power half-bridge is controlled in a block-commutated manner by generating a control signal for the power half-bridge in the converter. For this purpose, the inverter receives a clock signal which contains switching information about the switching time point of the control signal and which is generated and transmitted, for example, by a computing unit separate from the inverter, such as a motor control device. The level of the control signal is then switched in the converter on the basis of the clock signal and the switching information contained therein, or the control signal is generated such that it accordingly contains a change in level.

While in the case of motors of the higher power class, the phase voltages of the stator are usually generated using a fast clocked pulse inverter method, pure block commutation can also be used as a control method for motors with comparatively low power (for example 150W to 500W or possibly 1 kW) as is the case in the field of motor-cycle engineering. The resulting profile of the phase voltage is similar in its shape to the voltage profile in the case of conventional diode rectifiers. However, the power output or power consumption of the motor can be arbitrarily set by the phase angle value of the voltage with respect to the rotor position.

In the case of block commutation, the steering signals for the power half-bridges are only phase-shifted with respect to each other, but are otherwise identically shaped. This now makes it possible to store such forms of the steering signals in an analog manner in the inverter, for example in suitable circuits or hardware for all power half-bridges or phases, and as an input only to apply or receive in the inverter the mentioned clock signals describing the switching points or switching time points from one block to the next, i.e. those time points at which the level of the steering signal should or must be changed, for example from high to low.

Here, the block describes an interval where there is no change in the manipulation signal. Accordingly, each edge of the control signal, i.e. the level change description, transitions from one block to the next. For three phases, for example, six different switch states and blocks are obtained before the first block pattern is repeated after a cycle (or a steering cycle), i.e. the steering cycle performs a complete traversal.

The number of cycles per rotor revolution is derived from the number of magnets or pole pairs used in the rotor. For each pole pair, an electrical cycle is obtained, so that for six pole pairs, for example, six cycles or actuation cycles are obtained per revolution. Since the sequence of blocks is fixedly predefined by the geometry of the electric machine, the sequence of blocks is not changed by different torque requirements. Only the phase angle value of the block relative to the rotor position is shifted.

Preferably, the clock signal furthermore contains synchronization information, which preferably specifies each complete traversal of the commutation period of all power half-bridges, wherein the commutation signal is brought into a desired state in the inverter, preferably synchronized with the rotor position of the electrical machine, on the basis of the clock signal and the synchronization information contained therein. Accordingly, it is possible to synchronize the manipulations accordingly, periodically and/or when needed.

It is particularly preferred if the switching information in the clock signal corresponds to the synchronization information for a particular switching time point of a particular control signal within a complete traversal of the control cycles of all power half-bridges and is formed as a pulse having a first length, wherein the switching information is formed as a pulse having a second length, different from the first length, for the remaining switching time points of the control signals within this complete traversal of the control cycles of all power half-bridges. Here, the pulse for the synchronization information is suitably longer (first length) than the remaining pulse for the switching information (second length).

In the exemplary case of a three-phase machine, a total of six successive switching time points are obtained, one of which is used for synchronization and has a pulse length which differs from the other five switching time points. The clock signal therefore contains a longer pulse after every five short pulses. The defined block is shifted to be assigned to this longer pulse. Thereby realizing that: synchronization to the rotor and crankshaft positions is possible and the circuit can be brought into a known state at any time. The clock signal can be designed with short voltage dips and high quiescent levels. However, depending on the implementation, clock signals with low quiescent levels and short rising voltage peaks or pulses may also be used.

Alternatively, it is preferred if the switching information in the clock signal is constructed as pulses having lengths differing from one another for the switching time points of all the control signals of a complete traversal of the control cycles of all the power half-bridges, respectively. In particular, one or more pulses are then used as synchronization information during this traversal of the control cycles of all power half-bridges.

In the case of this variant, not only can a specific block transformation be triggered by longer pulses, but also a defined pulse length is assigned to each block transformation. It is thus possible to switch to an arbitrary block at every arbitrary point in time without having to output a sequence of a plurality of pulses. Depending on the response speed of the switching of the converter, a fast sequence of block transformations may trigger a short-time oscillation of the phase voltages etc., which can be avoided with this alternative even if this requires, for example, a more costly coding of the clock signal.

Independent of the number of different pulse lengths, an implementation is preferred in which the first starting edge of the pulse triggers a block transition to the next switching state, i.e. is used as switching information. The duration up to the second end edge of the pulse (i.e. the duration of the pulse itself) is expediently used to check or evaluate whether the currently set block corresponds to the desired block characterized by the pulse length, i.e. whether the level of the control signal corresponds. If not, a re-switching procedure to the desired block is preferably triggered. This ensures that the switch to the next block is made as early as possible and that, in the case of an error, resynchronization can be effected as soon as synchronization information is present with the end of a pulse (two pulse lengths after six pulses at the latest, after the evaluation of each pulse length in the second variant).

Across the entire operating range of the electric machine, different requirements can be made on the circuit or the inverter and the clock signal to be generated or received.

During the starting process, the position of the crankshaft of the internal combustion engine (and the position of the rotor of the slave motor) is not immediately known. Accordingly, the inverter cannot be controlled in a targeted manner and a reasonable clock signal cannot be provided. In this connection it is preferred that the control signal for the power half-bridge is generated in the inverter only when the clock signal is (fully) received, in order to control the power half-bridge in block commutation.

It is furthermore expedient if the inverter is operated as a diode rectifier or all high-side switches or all low-side switches of the power half-bridge are switched conductive if the inverter does not receive a clock signal or if the clock signal contains no switching information.

In order to have a defined state of the inverter in such an operating point during the starting process, an "enable" signal can be generated from the clock signal. The "enable" signal may correspond to a "disable" level (e.g., low) if the clock signal is not present (or contains no switching information). If a clock signal is present, the "enable" level of the "enable" signal is derived therefrom (thus, for example, high) and switching is activated in the inverter. If necessary, the enable signal can assume the enable level only when the synchronization pulse is first predefined (i.e. for example a longer pulse, as already mentioned above).

If the "disable" level is present, the converter can be operated as a diode rectifier, as has also been mentioned. For this purpose, all power switches can be switched off and the body diodes that are typically present (for example the parasitic diodes of MOSFETs) can be used as diode rectifiers. Alternatively, the upper power switches can all be switched off and the lower power switches can all be switched on (or vice versa), and the electric machine can thereby be operated in a short-circuit state decoupled from the direct voltage side (battery or electrical system side).

The activation may preferably be performed by a (longer) synchronization pulse or synchronization information in the clock signal. In order to output the synchronization pulse as early as possible after the crankshaft position is present, the required number of short pulses (with switching information) can be output very shortly after the synchronization pulse in order to set the desired block for the current crankshaft position. Since the block is reached, a clock signal is output in synchronism with the rotational frequency of the rotor, with longer pulses being output at the respective positions as described, in order to ensure that the phase angle values of the phase voltages are set as desired and that, for example, there is no permanent shift (faulty) operation on the clock line due to short-term disturbances.

As already mentioned, the electric machine is preferably coupled to the internal combustion engine in a rotationally fixed manner, for example by fastening the rotor directly to or at the crankshaft of the internal combustion engine.

It is also expedient for the clock signal to be generated by a different computing unit than the inverter (for example, a motor control device of an internal combustion engine) and to be transmitted to the inverter, preferably via a separate control line. In order to change the mechanical or electrical power emitted by the electric machine, the switching time information in the clock signal is then changed such that the switching time is shifted in time.

In order to change the torque of the electric machine, the phase angle values of the phase voltages and thus of the clock signals have to be changed. Based on typical generator operation for powering electrical systems, the clock signal must be delayed for stronger generator-type operation and increased braking torque (i.e., increased electrical power generated). For weaker generator-type operation or motor-type operation and acceleration torque (i.e., increasing the mechanical power emitted), the clock signal must be output earlier.

For stronger generator operation, the switching takes place by correspondingly delaying the next clock pulse. However, if the newly obtained block is to correspond to a block that is different from the block that corresponds to the very current block, a correspondingly long delay must be provided for this purpose. Alternatively, the synchronization pulse or synchronization information may also follow the necessary number of short pulses or switching information in order to immediately switch to the desired block.

In order to switch to a less powerful generator or motor mode of operation, the clock pulses must be advanced in time. Here, if a pulse is to "slip in" past, the synchronization pulse or synchronization information must also be carried out after the necessary number of short pulses or switching information in order to achieve a rapid and targeted transfer into the desired block.

Instead of the synchronization pulse and the necessary number of other pulses for reaching the desired new block, only the necessary number of short pulses may be output. Since each first edge of a pulse triggers a further switch to the next block, it is desirable to place all necessary pulses in the shortest possible time for a fast transition to a new block, i.e. to discard a long synchronization pulse. This alternative enables faster switching to a new block, but with the following risk: in the event of a disturbance pulse, there may be an erroneous operating state of the electric machine until a regular synchronization pulse is output.

The electric machine is expediently accommodated in an electrical system with a battery, wherein it is then preferred that the synchronization information and/or the switching information cause the converter to: if an undesired change in the battery or the electrical system voltage is detected, a desired level of the desired control signal is subsequently generated.

Short-time disturbances of the clock signal, for example a single disturbance pulse, lead to a transition to an undesired block or to a level change of the control signal. Accordingly, an undesirable torque of the motor occurs. Accordingly, when jumping to stronger generator mode operation, more electrical energy is generated into the electrical system and the battery voltage rises. And when jumping to weaker generator or even motor operation, the energy drops or becomes negative. The battery voltage drops accordingly.

When an undesired, in particular significant, change in the battery voltage or the electrical system voltage is detected (or when the respective threshold value is exceeded or not exceeded), a possible disturbance of the signal line or of the clock signal transmitted via the signal line can therefore be inferred. In response, a synchronization pulse and a necessary number of short pulses (or synchronization information and switching information) may be output in order to reach a desired block.

If the desired battery voltage does not subsequently occur, a load change in the electrical system can be inferred, and the rating of the respective voltage regulator can be adapted to the new load condition.

Further, the monitoring of the clock signal may be provided in the hardware of the converter. For example, the frequency of the clock signal may be checked for plausibility, and if there is high frequency and persistent interference, the circuit may be deactivated ("disable" level, etc.). Alternatively, the renewed clock pulse is only allowed after a minimum time, so that the regions in which the interference has an effect are reduced. In addition, the maximum time between clock pulses may also be monitored. Since the control device is actuated only with the rotating crankshaft and at a minimum rotational speed (for example 50-100 rpm or U/min), it is possible to prevent disturbances on the clock line from causing incorrect operation of the inverter when the crankshaft is stationary or at low rotational speeds.

Furthermore, a converter for operating a permanently excited electrical machine, which has a power half-bridge for generating a phase voltage for each phase of the electrical machine, is the subject of the invention, and is set up to carry out all method steps of the method according to the invention as long as they are carried out by the converter.

Correspondingly, a system having a converter with a power half-bridge for generating a phase voltage for each phase of the electric machine and having a computing unit which is preferably connected to the converter by means of a control line is also the subject of the present invention, wherein the system is set up for carrying out all method steps of the method according to the present invention, for example, if the method steps are carried out by the converter and the computing unit (which may be an electric machine control device).

With regard to possible designs of the inverter and its circuit, reference should be made to the drawings and the accompanying description.

The implementation of the method according to the invention in the form of a computer program or a computer program product with program code for executing all method steps is advantageous, since this results in particularly low costs, in particular when the execution control device is also used for other tasks and is therefore already present. Suitable data carriers for providing the computer program are, in particular, magnetic, optical and electronic memories, such as a hard disk, flash memory, EEPROM, DVD, etc. It is also possible to download the program via a computer network (internet, intranet, etc.).

Further advantages and embodiments of the invention emerge from the description and the drawing.

The invention is schematically illustrated in the drawings according to embodiments and is described below with reference to the drawings.

Drawings

Fig. 1 schematically shows a system with an internal combustion engine, an electric machine, an inverter and an electric motor control device, with which the method according to the invention can be carried out.

Fig. 2 shows schematically in a preferred embodiment the clock signals and the control signals during the execution of the method according to the invention.

Fig. 3 schematically shows in a preferred embodiment a converter cell being part of a converter according to the invention.

Fig. 4 schematically shows signals generated with a converter unit according to fig. 3.

Fig. 5 schematically shows a circuit for implementing the functionality shown in fig. 3.

Detailed Description

Fig. 1 schematically shows a system 100, with which a method according to the invention can be carried out, having an internal combustion engine 120, an electric machine 110, an inverter 130 and a computing unit 160 in the form of a motor control device.

The electric machine 110 has a rotor 112 with permanent magnets (not shown) and a stator 111 with, for example, three phases U, V, W and thus forms a permanently excited electric machine (for example, a so-called outer rotor). The rotor 112 is connected in a rigid and rotationally fixed manner to a crankshaft 121 of the internal combustion engine 120.

For example, in the case of a suitably designed crankshaft (with a sensor wheel, for example, as mentioned at the outset), the rotational speed and the absolute position can be detected by means of the rotational speed sensor 122. These values may then also be fed to the motor control device 160.

The converter 130 (also referred to as inverter) has three power half bridges 140 according to three phases U, V, W, the power half bridges 140 each having a high-side power switch (e.g. MOSFET) 141 and a low-side power switch (e.g. MOSFET) 142, which are (electrically) wired and connected to the phase U, V, W in a manner known per se. Likewise, the power half-bridge 140 is (electrically) wired to the electrical system 170 or to the battery 171 in a manner known per se.

The inverter 130 furthermore has a converter unit 150, by means of which the inverter can receive a clock signal, which is then evaluated (as explained in more detail below) and forwarded to a control unit (or gate control circuit) 151, by means of which the inverter can generate a control signal for the power half bridges (in the example shown, a signal for each power switch, but only a signal for each power half bridge is also conceivable), and also via a (single) control line 131. For this purpose, the control lines to the individual power switches are shown.

Furthermore, the converter 130 has, for example, a monitoring unit 152, by means of which, for example, the voltage of the electrical system 170 or the battery 171 can be monitored. For example, so that an error response can likewise be initiated. As soon as an impermissibly high battery voltage is determined in this way, the high-side power switch can be switched to be completely off and the low-side power switch can be switched to be completely on (or vice versa), for example, and the electric machine can be operated in short-circuit mode and the battery can be protected against overcharging.

If, for example, the entire permissible range of the battery voltage should be able to be fully utilized during the operation of the inverter 130, the monitoring described can be released, for example, only if no clock signal is present.

In order to prevent the output voltage of the inverter from jumping during generator operation of the electric machine in the event of a loss of the battery terminals during operation, a second voltage monitoring can be permanently provided above the permitted battery voltage range. The second voltage monitoring intervenes, for example, in the event of a fault, and switches the electric machine to short-circuit operation, as also described.

The clock signal S is schematically shown in fig. 2 _T Steering signals S for three phases U, V and W _U 、S _V And S _W And the associated phase voltage (plotted as U over time t) that may occur when the method according to the invention is carried out, as in a preferred embodiment.

Clock signal S _T Having a high level as a quiescent level and containing switching information I _U And synchronization information I _S . In the example shown, the handover information I _U Constructed as pulses with short lengths (here short voltage dips), the synchronization information I _S Is constructed as a pulse of slightly longer length, here a longer voltage dip, but the synchronization information is simultaneously used as switching information.

From a clock signal S in an inverter, in particular by means of a converter unit 150 and a control unit 151 as shown in fig. 1 _T To obtain steering signals S for the three phases U, V and W _U 、S _V And S _W . Reference should also be made to the following statements.

It can be seen here that the clock signal S is used _T Per pulse or at each switching information I _U And each synchronization information I _S The level of one of the steering signals is changed. The form of the control signal corresponds to the usual form when block commutation is used and is known per se. In this connection it is possible to use only the clock signal S _T To generate these steering signals.

These control signals are then used to control the power half-bridge or the power switch in a manner known per se, i.e. the phase voltages obtained from these are the phase voltages that are common for block commutation, as can be seen in fig. 2 in the lower part.

In fig. 3, a converter cell is schematically illustrated in a preferred embodiment as part of a converter according to the invention (see also fig. 1 for this purpose). As already mentioned, three control lines (or one control line per phase) are no longer necessary by the invention, but rather one control line is sufficient for the clock signal. One possible and exemplary implementation of the additional circuitry required (the mentioned converter cell) is shown in fig. 1.

Basic functionality may be implemented by a shift register 300 having a serial data input and a parallel clocked data output. The shift register can be realized here as an integrated component or circuit with corresponding functionality.

When a corresponding first signal edge occurs at the clock input CLK, the shift register 300 transfers the logic level occurring at the DATA input DATA at that point in time to the first DATA output OUT 1. The corresponding signal edge can be a falling or rising signal edge depending on the selected shift register. Correspondingly other signal edges do not trigger any action in the shift register. With a clock signal S _T To the next data output N (OUT 1 to OUT 2, OUT 2 to OUT 3) and to the first output OUT 1 to assume the new current level of the data input.

In order to alternately obtain a high level or a low level for three clocks, the last DATA output (OUT 3) is fed back in inverted phase onto the DATA input (DATA). In this case, inversely means that a low level is predefined at the input when a high level is present at the output and vice versa.

The following switching state sequence is thus obtained:

here, clock 1 corresponds to the state that also occurs initially and after reset. After the sixth clock (clock 6), the pattern from clock 1 (clock 1') reappears not only due to the usual clock pulse but also due to the extended clock pulse (reset pulse). Thus, each cycle 1 can be triggered with a prolonged reset pulse without affecting the signal sequence, so that a continuous resynchronization takes place and possible interference pulses can cause interference in the output pattern only for a short time.

From a clock signal S predetermined by the motor control device _T To generate all required internal signals. Whenever necessary, the form and level of the clock signal is adapted to the additional circuitry in the inverter in a first step. For this purpose, a level shifter, an inverter circuit, or an amplifier circuit, and a protection circuit such as an overvoltage limitation or a current limitation may be applied as long as necessary.

A reset signal (see step or block 330) and (whenever desired) an enable signal (see step or block 320) are generated from the processed clock signal (see step or block 310). The reset signal is derived from the longer pulse in the clock signal (the synchronization information mentioned) and clears the register contents of the shift register 300 so that it is placed in an initial state.

This initial state defines the block in which the switching of the inverter is initially started and the position of the longer pulse in the clock signal has to be triggered in view of the block. The initial state typically corresponds to a low level at all data outputs. Accordingly, after the triggered reset, a high level is applied at the data input for the first subsequent clock signal.

As shown in fig. 2, only two of the control signals each have the same level, while the third control signal has a correspondingly different level. And after reset all three data outputs of the shift register have the same level. Thus, one of the three output signals (OUT 2) is handed over in anti-phase (OUT 2') to the subsequent circuit part. This ensures that the correct signal form of all three control signals is present at each time point and always starts in the same state after reset (triggered by a longer pulse of the clock signal), so that the functionality described above is achieved.

In order to additionally ensure that the control signal is forwarded only when a clock signal is present, i.e. is available at the output of the shift register, an "enable" signal may be set. Many shift register circuits offer the following possibilities: the output is only activated when the corresponding "enable" level is present at the "enable" input. Depending on the gate driver used, the same signal may also be used as an "enable" signal for these driver circuits.

Reset and enable functionality is typically associated with a falling signal edge or low level. Thus, when the circuit is not activated, the enable signal assumes a high level as a quiescent level and changes to a low level to activate the output. When the circuit is activated, the reset signal has a high level as a static level, and the reset of the shift register is triggered by a low pulse.

Thereby resulting in the signals shown in fig. 4. The signals CLK, RESET and EN signals are shown above. As described, the clock signal S is present as long as there is no signal from the outside _T Or CLK has a high level. By pre-setting the low level to a quiescent level, signaling: a clock signal can be expected from now on. Accordingly, the RESET signal RESET is set to a high level. By predetermining a longer pulse at the desired position (according to the torque request to the motor), a corresponding low pulse is generated in the reset signal, which pulse puts the shift register into the desired state. The enable signal is set to a low level in a delayed manner. Thus, the shift register can be switched to a desired state by a desired number of clock pulses before the output is activated and the inverter starts to operate.

Further shown are signal outputs OUT 1, OUT 2 and OUT 3. These signal outputs are activated only when the enable signal is set to a low level, and are all deactivated accordingly if the enable signal is set back to a high level. During the time that is activated, the output switches to the next state or block at each clock pulse according to the table above.

Furthermore, two signals OUT 2' and DATA are shown, which can be generated from the signals OUT 2 or OUT 3 by means of an inverter circuit and behave in a level-inverted manner accordingly.

Furthermore, the three output signals OUT 1, OUT 2' and OUT 3 are shown in the direction of the other hardware of the converter (i.e. towards the control unit 151 according to fig. 1). The signal profile corresponds to the control signals required for operating the converter in block commutation as shown in fig. 2.

After the fifth reset pulse, the clock signal S may be _T Or irregular pulse patterns are seen in CLK. Individual glitches are drawn between the desired clock pulses. The glitch pulse correspondingly triggers an early transition to the next block. The thus shifted pattern of the output signal continues until the next reset pulse. At this point, the circuit is resynchronized to the desired clock signal and the corresponding output pattern is again output.

The first extended clock pulse (i.e. the synchronization information) and the reset pulse associated therewith can optionally be output only when the rotor of the electrical machine is in the desired position (according to the desired operating point of the electrical machine) or already earlier if the inverter should start operating as early as possible.

In this case, after the reset pulse, the other clock pulses required have to be output immediately after one another in order to bring the shift register into the desired state before the output is activated (enable = low). In the example shown here, a further pulse is shifted back in the clock signal immediately after the first reset pulse (nachgeschoeben) before the further clock pulses for switching the respective blocks are predefined in a rotor-synchronous manner.

A possible implementation or circuit with additional functional blocks in addition to the shift register according to fig. 3 is shown in fig. 5. The circuit shown is based on the input signal S _T The output stage with open collector line or push-pull stage is used to generate the output voltage at proper output level in motor control deviceInputting a signal. Preferably, a corresponding input line (see reference numeral 310 in fig. 3) can also be provided for level conversion or as a protection device for signal input, which input circuit adapts the signal of the control device to the operating range of the inverter circuit and at the same time suppresses interference.

If the input signal is not predetermined by the motor control device, the clock signal S _T Is pulled to the supply voltage Vcc through a pull-up resistor R1. However, if the motor control device generates an input signal, the input signal is active high here. That is, the quiescent level is at a low level and the pulse is transmitted as a short high level.

The input signal (in the case of open collector generation) is pulled through pull-up resistor R1 to the desired voltage level Vcc of the line. The slight fluctuations or short voltage peaks are filtered by capacitor C1.

The members R2, R6, C2, M1 and D1 generate desired reset signals from the input signals. Due to the low-pass capability of the resistor R6 and the capacitor C2, rising edges in the input signal are only slowly forwarded to the gate of the MOSFET M1. The threshold voltage of the MOSFET is exceeded only with a sufficiently long pulse length (prolonged synchronization pulse of the input or clock signal) and the MOSFET becomes conductive for a short time. Therefore, the reset signal is pulled high through the resistor R6 most of the time. The reset signal is pulled low for this period only if the input signal has a sufficiently long pulse (defined by the time constant of the RC element R2, C1).

Diode D1 causes: the gate of the MOSFET M1 is discharged quickly (without the time delay of the RC element) in case of a falling edge of the input signal. So that it is already possible to process the short pulses again shortly after the synchronization pulse without generating a distorted reset signal.

The members R3, R7, R8, C3, M2 and D2 generate enable signals. During absence of input signal, clock signal S _T Staying at a high level. The gate of MOSFET M2 is not manipulated by inversion by means of M1. In this case, the enable signal is thus pulled high through R3. Once the cover is closedThe input signal is applied (mostly as low level) and the gate of M2 is slowly charged (time defined by the time constant of the RC element) through R8 and C3. Once the threshold voltage of the gate is reached, M2 becomes conductive and pulls the enable signal low. Since typical enable functionality is activated by a low level, the state of the enable signal corresponds to the activation of the subsequent shift register output. Once the input signal is no longer present, the enable signal is no longer desired. If the input signal should be placed high as quickly as possible, the gate of M2 may be discharged through an optional additional circuit consisting of diode D2 and resistor R7 for current limiting. Alternatively, these two members may not be required, and the gate of M2 may be slowly discharged through R8. In both cases, the enable signal assumes a high level again (deactivated output and circuit) as soon as the input signal is no longer present.

The members R4, R9, and M3 are used to invert the output signal OUT 3. The inverted signal DATA is fed back to the DATA input of the shift register.

The members R5, R10, and M4 are used to invert the output signal OUT 2. This inverted signal OUT 2' is forwarded as a control signal to a circuit for controlling the power switch (control unit 151 according to fig. 1).

Instead of being realized by means of discrete components, it is also possible to provide for the use of a digital controller on the inverter. This is not as much as in the case of other converters, taking over the detection of the rotor position and the corresponding control of the output stage according to the external torque demand. Alternatively, the same pulse signals as described above can be supplied from an external control unit to the controller, and individual control signals for the output stages can be derived therefrom, and the input signals can be checked for plausibility and enable signals can be generated.

Accordingly, the requirements for such a digital controller are significantly lower than in the case of other converters, and therefore a more advantageous control unit with lower software expenditure can be used. If necessary, it is also possible to use an integrated unit which combines the digital control unit with the necessary additional lines (e.g. power supply) and the circuit parts for controlling all power switches in one component. Thereby, the space requirement on the circuit board of the inverter can be greatly reduced.

Claims (15)

1. A method for operating an electric machine (110) by means of an inverter (130), the inverter (130) having a power half-bridge (140) for generating a phase voltage for each phase (U, V, W) of the electric machine (110),

wherein the power half-bridge (140) is steered in a block-commutated manner by generating a steering signal (S) for the power half-bridge (140) in the converter (130) _U 、S _V 、S _W ），

Wherein the inverter (130) receives a clock signal (S) _T ) Said clock signal containing information about said steering signal (S) _U 、S _V 、S _W ) Switching information (I) of the switching time point of (2) _U ) And are each and every

Wherein in the converter (130) based on the clock signal (S) _T ) And handover information (I) contained therein _U ) Switching the control signal (S) _U 、S _V 、S _W ) Of (c) is detected.

2. Method according to claim 1, wherein said clock signal (S) _T ) In addition, it contains synchronization information (I) _S ) Said synchronization information preferably describing each complete traversal of a steering cycle of all power half-bridges, and wherein in said inverter (130) based on said clock signal (S) _T ) And synchronization information (I) contained therein _S ) The manipulation signal (S) _U 、S _V 、S _W ) Bringing into a desired state and preferably synchronizing with a rotor position of the electric machine (110).

3. Method according to claim 2, wherein only said clock signal (S) is asserted _T ) Is generated in the converter (130) when receivedGenerating a steering signal (S) for the power half-bridge (140) _U 、S _V 、S _W ) In order to steer the power half-bridge (140) in a block-commutated manner.

4. A method according to claim 2 or 3, wherein said clock signal (S) _T ) Handover information (I) in (1) _U ) For a steering signal (S) over a complete traversal of the steering cycles of all power half-bridges _U 、S _V 、S _W ) Corresponds to said synchronization information (I) _S ) And is constructed as pulses having a first length, and wherein the switching information (I) _U ) For the steering signals (S) within the complete traversal of the steering cycles of all power half-bridges _U 、S _V 、S _W ) Are each designed as a pulse having a second length, which is different from the first length.

5. Method according to any of claims 1 to 3, wherein the clock signal (S) _T ) Handover information (I) in (1) _U ) All steering signals (S) for a complete traversal of the steering cycles of all power half-bridges _U 、S _V 、S _W ) Are configured as pulses having mutually different lengths, and wherein preferably one or more pulses are used as synchronization information (I) within this traversal of the steering cycles of all power half-bridges _s ）。

6. Method according to claim 4 or 5, wherein for the switching time a starting edge of a pulse is used, and/or wherein a duration of a pulse is used for checking, in particular for checking a currently used level of a manipulation signal.

7. Method according to any of the preceding claims, wherein if the inverter (130) does not receive a clock signal or the clock signal (S) _T ) Without switching information, the converter (1)30) All high-side switches (141) or all low-side switches (142) operated as diode rectifiers or as the power half-bridge (140) are switched conductive.

8. The method according to one of the preceding claims, wherein the electric machine (110) is coupled in a rotationally fixed manner to an internal combustion engine (120).

9. Method according to any of the preceding claims, wherein the clock signal (S) _T ) Is generated by a calculation unit (160) different from the converter (130) and is preferably transmitted to the converter (130) via a separate control line (131).

10. Method according to claim 9, wherein the clock signal (S) is adapted to vary the mechanical or electrical power emitted by the motor (110) _T ) Switching time information (I) in (1) _U ) Is changed such that the switching time point is shifted in time.

11. The method according to claim 9 or 10, wherein the motor (110) is installed in an electrical system (170) with a battery (171), and wherein the clock signal (S) is generated if an undesired change of the battery or electrical system voltage is identified _T ) Is changed so that the synchronization information (I) _S ) And/or the handover information (I) _U ) Causing the converter (130) to generate a desired control signal (S) for the next time _U 、S _V 、S _W ) The desired level of the voltage.

12. An inverter (130) for operating a permanently excited electrical machine (110), the inverter (130) having a power half-bridge (140) for generating a phase voltage for each phase (U, V, W) of the electrical machine, the inverter being set up for carrying out all method steps of the method according to one of claims 1 to 7.

13. A system having an inverter (130) for operating a permanently excited electrical machine (110), the inverter (130) having a power half-bridge (140) for generating a phase voltage for each phase (U, V, W) of the electrical machine (110), and having a computing unit (160) which is preferably connected to the inverter (130) by means of a control line (131), wherein the system is set up for carrying out all method steps of the method according to any one of claims 8 to 11.

14. A computer program which, when executed on a converter (130) or a system, causes the converter (130) or the system to perform all the method steps of the method according to any one of claims 1 to 11.

15. A machine readable storage medium having stored thereon a computer program according to claim 14.

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