Melexis Technologies Nv

Melexis Nv

Christian Paintz

Thomas Freitag

Enrico Reinhardt

Detlef Klose

Heiko Grimm

Jan Heynlein

A method for assisting in operating a PWM driven motor comprising for at least one phase of the PWM driven motor: generating a pulse width modulated phase voltage scheme according to a desired phase profile with a base scaling factor, by time multiplexing a first pulse and at least a further pulse within a pulse width modulation period of the phase the first pulse having a pulse width according to a first profile, for that rotor position, multiplied with a first scaling factor, the first profile being in phase with the desired phase profile, and the at least a further pulse having a pulse width corresponds with a further profile, for that rotor position, multiplied with a further scaling factor, the further profile being not in phase with the desired phase profile, whereby the first pulse and the at least one further pulse are positioned within the pulse width modulation period of the phase in at least partially non-overlapping way.

Control for pulse width modulated driven motors

A switching control circuit includes driving a flow of direct current through an at least partially inductive load. The switching control circuit is adapted for adjusting a control current in order to activate and/or deactivate a flow of current to a load terminal. The system comprises a timer element for initiating at least one timed adjustment of the control current during activation or deactivation of the flow of current through a first semiconductor switch of the circuit so as to anticipate a state change of a component of the switching control circuit. The controller is adapted for determining a timing for the timed adjustment in a predictive manner. A method employs the various features of the switching control circuit.

Direct current control with low E-M emission

A method is provided for determining a phase current direction and a zero-crossing moment of the phase current in a sinusoidally controlled brushless direct current motor. The brushless direct current motor comprises a coil per phase and the phase of the brushless direct current motor is driven by a half bridge driver. The half bridge driver comprises a high side field effect transistor and a low side field effect transistor. The method comprising the following steps: measuring the drain source voltage over the high side field effect transistor and low side field effect transistor, and determining the zero crossing moment of the phase current by determining the current direction based on the measured drain source voltages and by determining the moment the current changes direction.

Phase current regulation in BLDC motors

During operation of a 3 phase BLDC motor it is driven by use of a PWM waveform applied to one of the driven phase (curve a). The other driven phase is connected thereto but no driving signal is applied (curve b). The third phase is left floating (curve c). This allows the back EMF in the third phase to be monitored for the purpose of determining rotor position by detection of zero crossing points. The rapid switching of the PWM pulses causes ringing in the back EMF signal indicated for one pulse by the ringed portionsof curve c. The ringing in the back EMF signal introduces inaccuracy into position calculations derived from back EMF signal measurement. In order to reduce this ringing, in the present invention, a reverse pulse is applied to the other driving coil shown (curve b) prior to a PWM on pulse. The reverse pulse has a polarity such that it drives the phase current through the linked coils in a direction opposite to that caused by the PWM on pulse. This reverse pulse reduces the magnitude of the ringing in the back EMF signal.

Accuracy of rotor position detection relating to the control of brushless DC motors

The present invention there is provides a method of determining the rotor position in an electric motor comprising the steps of: superimposing one or more alternating signals on to the driving waveform so as to generate one or more oscillating currents in the stator coils; monitoring the variation in magnitude of the oscillating currents and thereby determining the rotor position. Typically, two alternating signals are applied in opposition so as to have no net effect on the torque applied by the driving waveform. Using this technique rotor position estimation can be obtained at start-up from stand-still and at low to medium speeds. The method can be used in applications where a fast motor start is needed under unknown load conditions and can be used to detect when the rotor has passed a certain position that coincides with the commutation instance.

Operation of BLDC motors

In response to the determination or estimation of a back EMF zero crossing event for the phase, a time Tis calculated, Tbeing representative of the desired absolute maximum value of the phase current. Current samples are taken by the current sampling unit symmetrically centered around T. The values of the samples CS[] to CS[] are then input into the error function to calculate an error function value. The calculated error function value is input to the lead angle control unit which calculates a value for lead_angle. The value of lead_angle is calculated to be the adjustment in phase angle of the driving voltage profile that will minimize the absolute value of the error function. In generating and adjusting the driving voltage profile the driving voltage generation unit takes into account both lead_angle and the output of the position and speed estimation unit. The estimated motor speed may be used additionally in an outer speed control loop involving speed controller to adjust the amplitude (AMP) of the effective driving voltage.

Control of sinusoidally driven brushless DC (BLDC) motors

A driving system for a tri-polar electric motor comprises three phase windings. Winding drivers drive each winding with a driving waveform having a non-zero driving phase and intervals wherein the input is equal to zero at the start, middle and end of each driving phase. Using a driving waveform of this type enables monitoring of the back EMF in the winding during each interval when the input is equal to zero. This enables regular monitoring of the zero crossing point of each winding and hence of the position of the rotor. This enables the motor to operate efficiently without generating a torque ripple.

Driving brushless DC (BLDC) motors

In a three phase BLDC motor the rotor position is monitored by detecting the zero crossing points of the induced back EMF signals BEMF_U, BEMF_V, BEMF_W in the phase windings U, V, W. As they are illustrated, the back EMF signals are substantially sinusoidal but they may in other situations be substantially trapezoidal. The three back EMF signals are 120&#xb0; out of phase with each other. In order to accurately monitor the back EMF in a phase winding, the driving waveform for each phase U, V, W includes an undriven period P close to the expected zero crossing point. The period P can be a preset part of the driving waveform or can be an interruption of the normal driving waveform in response to suitable interrupt signals. In order to determine the zero crossing points of each back EMF signal, two (or more) samples of the back EMF are taken during the undriven period P and used to interpolate the back EMF signal to determine the zero crossing point.

Relating to driving brushless DC (BLDC) motors

In order to determine the orientation of the rotor of a brushless DC motor, a sequence of current pulses may be applied to the stator phases U, V, W by the respective drivers HS, LS, HS, LS, HS, LS. The current generated in the stator phases U, V, W in turn generates a current in a shunt resistor. The current in this shunt resistoris monitored by use of a current voltage converterand a comparatorto determine when it exceeds a predetermined threshold. The rise time until the threshold current is exceeded is recorded in capture unit. A processor unitthen calculates a scalar parameter SU, SV, SW for each respective stator phase U, V, W from the recorded rise times associated with each pulse. The orientation of the magnetic axis of the rotor can then be determined by consideration of the scalar parameters SU, SV, SW of each stator phase U, V, W, as the respective rise times of each pulse are determined by the inductive properties of the respective stator phases U, V, W, which in turn are dependent upon the orientation of the rotor.

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Erfurt, Germany

Christian Paintz