阅读说明：本技术 具有变频机制的马达驱动系统及方法 (Motor driving system with frequency conversion mechanism and method ) 是由 蔡明融 于 2019-09-25 设计创作，主要内容包括：本发明公开一种具有变频机制的马达驱动系统及方法。系统包含查表模块、振荡电路、多频信号生成电路以及马达驱动电路。查表模块储存默认驱动信号。振荡电路生成具有不同频率的多个振荡信号。多频信号生成电路依据多个振荡信号输出多频信号。多频信号在调频区的波形区段具有第一振荡频率。多频信号在调频区外的其他波形区段具有第二振荡频率。第一振荡频率大于第二振荡频率。马达驱动电路在调频区的时间区间内,当马达的反电动势或相电流到达零值时,依据默认驱动信号以及多频信号输出驱动信号至马达。(The invention discloses a motor driving system with a frequency conversion mechanism and a method thereof. The system comprises a table look-up module, an oscillation circuit, a multi-frequency signal generating circuit and a motor driving circuit. The table look-up module stores the default driving signal. The oscillation circuit generates a plurality of oscillation signals having different frequencies. The multi-frequency signal generating circuit outputs a multi-frequency signal according to the plurality of oscillation signals. The multi-frequency signal has a first oscillation frequency in a waveform section of the frequency modulation region. The multifrequency signal has a second oscillation frequency in other waveform sections outside the frequency modulation region. The first oscillation frequency is greater than the second oscillation frequency. The motor driving circuit outputs a driving signal to the motor according to the default driving signal and the multi-frequency signal when the back electromotive force or the phase current of the motor reaches a zero value in a time interval of the frequency modulation region.)

1. A motor driving system with a frequency conversion mechanism, adapted to drive a motor, the motor driving system with the frequency conversion mechanism comprising:

a table lookup module configured to store a default drive signal;

an oscillation circuit configured to generate a plurality of oscillation signals having different frequencies;

a multi-frequency signal generating circuit, connected to the table look-up module and the oscillating circuit, configured to transmit the default driving signal and output a multi-frequency signal according to the plurality of oscillating signals, where the multi-frequency signal has a first oscillating frequency in a waveform section of a frequency modulation region, and the multi-frequency signal has a second oscillating frequency in other waveform sections outside the frequency modulation region, and the first oscillating frequency is greater than the second oscillating frequency; and

and the motor driving circuit is connected with the multi-frequency signal generating circuit and is configured to output a driving signal to drive the motor according to the default driving signal and the multi-frequency signal when detecting that the back electromotive force or the phase current of the motor reaches a zero value in the time interval of the frequency modulation area.

2. The motor driving system with frequency conversion mechanism as claimed in claim 1, wherein the multi-frequency signal generating circuit is configured to redefine the frequency conversion region according to a local adjustment request.

3. The motor driving system with variable frequency mechanism as claimed in claim 1, further comprising a detection circuit configured to detect a back electromotive force or a phase current of the motor during the time interval of the frequency modulation region.

4. The motor driving system with a frequency conversion mechanism according to claim 3, wherein the detection circuit detects that a back electromotive force or a phase current of the motor reaches a zero value at time points within the frequency modulation region of the multi-frequency signal, the time points being separated by an angle on the waveform of the multi-frequency signal from a start time point and an end time point of the frequency modulation region, respectively.

5. A motor driving method with a frequency conversion mechanism is suitable for driving a motor, and is characterized by comprising the following steps:

storing the default driving signal by using a table look-up module;

generating, with an oscillation circuit, a plurality of oscillation signals having different frequencies;

outputting a multi-frequency signal by using a multi-frequency signal generating circuit according to the plurality of oscillation signals, wherein the multi-frequency signal has a first oscillation frequency in a waveform section in a frequency modulation area, the multi-frequency signal has a second oscillation frequency in other waveform sections outside the frequency modulation area, and the first oscillation frequency is greater than the second oscillation frequency;

transmitting the default drive signal using the multi-frequency signal generation circuit; and

and outputting a driving signal to drive the motor according to the default driving signal and the multi-frequency signal when detecting that the back electromotive force or the phase current of the motor reaches a zero value in the time interval of the frequency modulation area by using a motor driving circuit.

6. The method as claimed in claim 5, further comprising the steps of:

and redefining the frequency modulation area by using the multi-frequency signal generating circuit according to the area adjustment request.

7. The method as claimed in claim 5, further comprising the steps of:

and detecting the back electromotive force or the phase current of the motor in the time interval of the frequency modulation area by using a detection circuit.

8. The method as claimed in claim 5, further comprising the steps of:

detecting, with a detection circuit, that a back electromotive force or a phase current of the motor reaches a zero value at time points within the frequency modulation region of the multi-frequency signal, wherein the time points are separated by an angle on a waveform of the multi-frequency signal from a start time point and an end time point of the frequency modulation region, respectively.

Technical Field

The present invention relates to a motor driving system and method, and more particularly, to a motor driving system and method with a frequency conversion mechanism.

Background

Generally, in order to drive the dc brushless motor to detect the position of the motor rotor, a position sensor, such as a Hall sensor (Hall sensor), an optical encoder, etc., is used to obtain an appropriate phase-change signal to drive the motor to rotate normally when the motor is running. However, the position sensor must be placed inside the motor, which increases the size of the system, increases the assembly difficulty and increases the system cost.

In order to reduce the volume of the system occupied by the motor and the difficulty of assembly, the brushless dc motor technology without sensors is widely applied to various driving products. Many brushless dc motor driving apparatuses without sensors have been proposed to determine the position and phase change of a rotor by Back Electromotive force (BEMF) induced by a stator (stator) of the motor. Or another existing structure, the phase change action is performed by using the phase current of the motor as zero. However, both of the above may still fail to detect in real time that the back emf of the motor has reached a zero value or that the motor phase current has been zero.

Disclosure of Invention

The present invention provides a motor driving system with a frequency conversion mechanism, which is suitable for driving a motor. The motor driving system with the frequency conversion mechanism comprises a table look-up module, an oscillation circuit, a multi-frequency signal generating circuit and a motor driving circuit. The look-up table module is configured to store a default driving signal. The oscillation circuit is configured to generate a plurality of oscillation signals having different frequencies. The multi-frequency signal generating circuit is connected with the table look-up module and the oscillating circuit. The multi-frequency signal generating circuit is configured to transmit a default driving signal and output a multi-frequency signal according to a plurality of oscillation signals. The multi-frequency signal has a first oscillation frequency in a waveform section of the frequency modulation region. The multifrequency signal has a second oscillation frequency in other waveform sections outside the frequency modulation region. The first oscillation frequency is greater than the second oscillation frequency. The motor driving circuit is connected with the multi-frequency signal generating circuit. The motor driving circuit is configured to output a driving signal to drive the motor according to the default driving signal and the multi-frequency signal when detecting that the back electromotive force or the phase current of the motor reaches a zero value in a time interval of the frequency modulation region.

In one embodiment, the multi-frequency signal generating circuit is configured to redefine the frequency modulation region according to the local adjustment request.

In one embodiment, the motor driving system with the frequency conversion mechanism further includes a detection circuit configured to detect a back electromotive force or a phase current of the motor during a time interval of the frequency conversion zone.

In one embodiment, the detection circuit detects that the back electromotive force or the phase current of the motor reaches a zero value at a time point within the frequency modulation section, wherein the time point is separated by an angle from a start time point and an end time point of the frequency modulation section, respectively.

In addition, the invention provides a motor driving method with a frequency conversion mechanism, which is suitable for driving a motor, and comprises the following steps: storing the default driving signal by using a table look-up module; generating, with an oscillation circuit, a plurality of oscillation signals having different frequencies; outputting a multi-frequency signal by using a multi-frequency signal generating circuit according to a plurality of oscillation signals, wherein the multi-frequency signal has a first oscillation frequency in a waveform section in a frequency modulation area, the multi-frequency signal has a second oscillation frequency in other waveform sections outside the frequency modulation area, and the first oscillation frequency is greater than the second oscillation frequency; transmitting a default drive signal using a multi-frequency signal generating circuit; and outputting a driving signal to drive the motor according to the default driving signal and the multi-frequency signal when detecting that the back electromotive force or the phase current of the motor reaches a zero value in a time interval of the frequency modulation area by using the motor driving circuit.

In one embodiment, the method for driving a motor with a variable frequency mechanism further includes the following steps: and redefining the frequency modulation area by using the multi-frequency signal generating circuit according to the area modulation request.

In one embodiment, the method for driving a motor with a variable frequency mechanism further includes the following steps: the back electromotive force or the phase current of the motor is detected in the time interval of the frequency modulation section by a detection circuit.

In one embodiment, the method for driving a motor with a variable frequency mechanism further includes the following steps: with the detection circuit, it is detected that the back electromotive force or the phase current of the motor reaches a zero value at time points within the frequency modulation section, which are separated by an angle from the start time point and the end time point of the frequency modulation section, respectively.

As described above, the present invention provides a motor driving system and method with a frequency conversion mechanism, which generates a plurality of oscillation signals with different oscillation frequencies by using an oscillation circuit, and generates a multi-frequency signal with a high-frequency waveform section and a low-frequency waveform section according to the plurality of oscillation signals, wherein the current and the electromotive force of the motor are detected with a higher detection frequency and a higher resolution in a time interval of the high-frequency waveform section, so that the current and the electromotive force can be accurately detected in real time as parameter conditions for driving the motor, thereby improving the operating efficiency of the motor, and the low-frequency waveform section is provided to reduce switching loss and power consumption when the detection operation is not performed.

For a better understanding of the features and technical content of the present invention, reference should be made to the following detailed description and accompanying drawings, which are provided for purposes of illustration and description only and are not intended to limit the invention.

Drawings

Fig. 1 is a block diagram of a motor driving system with a frequency conversion mechanism according to an embodiment of the present invention.

Fig. 2 is a flowchart illustrating steps of a motor driving method with a frequency conversion mechanism according to an embodiment of the present invention.

Fig. 3 is a waveform diagram of a cycle of a multi-frequency signal generated after frequency modulation of an oscillation signal in a frequency modulation region according to a motor driving system with a frequency conversion mechanism and a method of the present invention.

Fig. 4 is a waveform diagram of two cycles of a multi-frequency signal generated after frequency modulation of the oscillation signal in the frequency modulation region according to the motor driving system with frequency conversion mechanism and the method of the present invention.

Fig. 5 is a waveform diagram of a current signal of a motor detected by the motor driving system and method with a frequency conversion mechanism according to an embodiment of the invention.

Fig. 6 is a waveform diagram of a triangular wave signal, a sinusoidal wave signal, a triangular wave level signal, a motor driving signal, and a node voltage signal of the motor provided by the motor driving system and method with a frequency conversion mechanism according to the embodiment of the invention.

Fig. 7 is a waveform diagram of a node voltage signal and a current flowing signal of a motor to which the system and method for driving a motor with a frequency conversion mechanism according to an embodiment of the present invention are applied.

Detailed Description

The following are specific examples to illustrate the embodiments of the present disclosure, and those skilled in the art will appreciate the advantages and effects of the present disclosure from the disclosure herein. The invention is capable of other and different embodiments and its several details are capable of modification and various other changes, which can be made in various details within the specification and without departing from the spirit and scope of the invention. The drawings of the present invention are for illustrative purposes only and are not intended to be drawn to scale. The following embodiments will further explain the related art of the present invention in detail, but the disclosure is not intended to limit the scope of the present invention.

It will be understood that, although the terms "first," "second," "third," etc. may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are used primarily to distinguish one element from another element or from one signal to another signal. In addition, the term "or" as used herein should be taken to include any one or combination of more of the associated listed items as the case may be.

Please refer to fig. 1, which is a block diagram of a motor driving system with a frequency conversion mechanism according to an embodiment of the present invention. As shown in fig. 1, the motor driving system with frequency conversion mechanism according to the embodiment of the invention includes a look-up table module 10, an oscillation circuit 20, a multi-frequency signal generating circuit 30 and a motor driving circuit 40. The multi-frequency signal generating circuit 30 is connected to the table look-up module 10 and the oscillating circuit 20. The motor drive circuit 40 is connected to the multi-frequency signal generation circuit 30.

The lut 10 can be a lookup table, or can be replaced by a database, a register, a memory or other components with storage functions, which are only exemplary and not limiting. The lookup module 10 is configured to store the default driving signal MD. For example, the default drive signal MD may have one or more sine waves, third-order harmonics (third-order harmonics) or other waveforms, which are merely illustrative and not limiting.

The oscillation circuit 20 is configured to generate a plurality of oscillation signals having different frequencies. In the present embodiment, the oscillation circuit 20 generates the first oscillation signal OWH and the second oscillation signal OWL. For example, the first oscillation signal OWH and the second oscillation signal OWL are triangular waveforms, which are only illustrated herein, and the invention is not limited thereto. The first oscillation signal OWH may be a high frequency oscillation signal having a first oscillation frequency. The second oscillation signal OWL may be a low frequency oscillation signal having a second oscillation frequency. The first oscillation frequency of the first oscillation signal OWH is greater than the second oscillation frequency of the second oscillation signal OWL.

The multi-frequency signal generating circuit 30 is configured to output the multi-frequency signal MFS according to the first oscillation signal OWH and the second oscillation signal OWL obtained from the oscillating circuit 20. For example, the multi-frequency signal generating circuit 30 defines a waveform section of the waveform of the first oscillation signal OWH in the frequency modulation region HFR, and performs frequency modulation on the waveform section in the frequency modulation region HFR to generate the multi-frequency signal MFS having the second oscillation frequency in the frequency modulation region HFR and the first oscillation frequency outside the frequency modulation region HFR. The waveform of the multi-frequency signal MFS of the present embodiment may have two or actually more frequencies, compared to a single oscillation signal having only a single frequency.

In fact, the multi-frequency signal generating circuit 30 may obtain more oscillation signals from the oscillation circuit 20 and define more frequency modulation regions, and the invention is not limited to the two oscillation signals OWH and OWL illustrated in the embodiment. The multi-frequency signal generating circuit 30 can frequency-modulate a plurality of waveform sections in a plurality of frequency modulation regions according to a plurality of oscillation signals, so that the same multi-frequency signal MFS has more frequencies.

The motor driving system with the frequency conversion mechanism of the embodiment may further include a detection circuit (not shown) configured to detect the back electromotive force or current of each coil of the three phases of the motor during the time interval of the frequency conversion zone. The multi-frequency signal generating circuit 30 can redefine or adjust the frequency modulation regions in different angle ranges of the multi-frequency signal MFS and the widths of the frequency modulation regions according to the region adjustment request, thereby redefining the time interval for detecting the motor.

The motor is operated at a normal speed, e.g., a low rotational speed, e.g., 50HZ, in a normal operation mode, which maintains low power consumption. In the time interval in which the motor is to be detected, the frequency of the multi-frequency signal MFS in the waveform section of the frequency modulation region is increased by, for example, 100HZ, so that the detection circuit can accurately detect the electromotive force or the current value of the motor. Therefore, the detection circuit has high detection frequency and high resolution, can detect that the back electromotive force or current of the motor reaches zero value every time in real time, and can drive complete sine wave or third harmonic wave to the motor as expected after a preset time, such as the time of a frequency modulation region (a finishing time point PT2 of the frequency modulation region WN shown in FIG. 6), is started immediately or after a preset time, when the electromotive force or current of the motor reaches zero value is detected, so as to improve the operation efficiency of the motor.

Referring to fig. 1 and fig. 2 together, fig. 2 is a flowchart illustrating a method for driving a motor with a frequency conversion mechanism according to an embodiment of the present invention. As shown in fig. 2, the motor driving method with the frequency conversion mechanism of the present embodiment includes the following steps S201 to S213, and is applied to the motor driving system with the frequency conversion mechanism.

In step S201, the lut 10 provides the stored default driving signal MD, such as a sine wave or a third harmonic waveform, to the multi-frequency signal generating circuit 30.

In step S203, the oscillation circuit 20 generates a first oscillation signal OWH, i.e., a high-frequency oscillation signal, and supplies the generated signal to the high-frequency signal generation circuit 30.

In step S205, the oscillation circuit 20 generates the second oscillation signal OWL, i.e., a low-frequency oscillation signal, and supplies the generated signal to the high-frequency signal generation circuit 30.

In step S207, the multi-frequency signal generating circuit 30 outputs the multi-frequency signal MFS according to the oscillation signals OWL and OWH. The waveform section of the multi-frequency signal MFS in the frequency modulation region has a high-frequency oscillation frequency. The multi-frequency signal MFS has a low-frequency oscillation frequency in other waveform sections outside the fm region.

In step S209, it is detected whether the electromotive force or current of the motor reaches zero value in the time interval of the frequency modulation section by using a detection circuit included in or added to the motor driving circuit 40.

In step S211, when the electromotive force or current of the motor reaches a zero value, the motor driving circuit 40 is used to generate a driving signal having a square wave or a pulse according to a default driving signal MD such as a sine wave or a third harmonic wave and a multi-frequency signal MFS such as a triangular wave.

In step S213, the motor driving circuit 40 drives the motor to operate by using the driving signal.

Referring to fig. 1 and 3 together, fig. 3 is a waveform diagram of a cycle of a multi-frequency signal generated by frequency-modulating the frequency of an oscillation signal in a frequency modulation region according to a motor driving system with a frequency-converting mechanism and a method of the present invention.

When the frequency of the triangular waveform is too high, the connected upper and lower switches of the motor will generate Switching Loss during Switching, especially for motor applications with Discrete MOSFET devices. In order to accurately detect the zero point of the electromotive force and the current of the motor to determine the subsequent driving of the motor, the triangular waveform should have a high frequency.

Therefore, as shown in fig. 3, the triangular waveform of the multi-frequency signal generated by the multi-frequency signal generation circuit 30 has a high-frequency waveform section TRWH in the frequency modulation region HFR and a low-frequency waveform section TRWL outside the frequency modulation region HFR. That is, during the time interval of the frequency modulation region HFR, the zero point of the electromotive force and the current of the motor is detected, and the low frequency waveform section TRWL is outputted when the detection operation is not performed, so as to reduce the switching loss.

The look-up table module 10 stores the default drive signal SIWL having a sine wave waveform, or which is actually replaced by a third harmonic waveform. The motor driving circuit 40 compares the default driving signal SIWL with the multi-frequency signals having waveform sections TRWH and TRWL to output the driving signal DM having a square wave or pulse waveform to the motor to drive the motor. In other words, the driving signal DM may be a pwm signal having a plurality of waveforms with different frequencies, and the frequency of the pulse in the fm region HFR is higher than the frequency of the pulse outside the fm region HFR.

Referring to fig. 1 and 4 together, fig. 4 is a waveform diagram of two cycles of a multi-frequency signal generated by frequency-modulating the frequency of an oscillation signal in a frequency modulation region according to the motor driving system with a frequency-modulating mechanism and the method of the present invention.

As shown in fig. 4, the sine wave of the default driving signal SIWL stored in the lookup module 10 corresponds to the triangle wave of the low-frequency oscillation signal generated by the oscillation circuit 20. The multi-frequency signal generating circuit 30 may define the frequency modulation regions HRR1, HRR2, HRR3 on the sine wave of the default driving signal SIWL. In the present embodiment, the fm regions HRR1, HRR2, and HRR3 have the same width, but in practice, they can be adjusted to have different widths according to the requirement.

The multi-frequency signal generating circuit 30 may drive the motor with the high-frequency of the waveform sections TRWH1, TRWH2, TRWH3 in the frequency modulation regions HRR1, HRR2, HRR3 according to the frequency of the high-frequency oscillation signal generated by the oscillation circuit 20.

In addition, the multi-frequency signal generating circuit 30 may have the same frequency as the fm waveform sections TRWH1, TRWH2, TRWH3 according to the single high-frequency oscillation signal generated by the oscillation circuit 20. Alternatively, the multifrequency signal generation circuit 30 may have frequencies different from each other in the frequency modulation waveform sections TRWH1, TRWH2, TRWH3 in accordance with the plurality of high-frequency oscillation signals generated by the oscillation circuit 20.

It should be understood that, in this document, "high frequency" and "low frequency" may be used merely as relative terms for emphasizing that the frequency of the waveform section of the multi-frequency signal within the frequency modulation region is higher than the frequency of the waveform section of the multi-frequency signal outside the frequency modulation region, or that the frequency of the waveform section of the multi-frequency signal outside the frequency modulation region is lower than the frequency of the waveform section of the multi-frequency signal within the frequency modulation region, and these terms are not intended to limit the frequency of the multi-frequency signal to be frequency-modulated within a specific invariable frequency range.

Please refer to fig. 5, which is a waveform diagram of a current signal of a motor detected by the motor driving system and method with a frequency conversion mechanism according to an embodiment of the present invention.

As indicated by a broken line a1 shown in fig. 5, the current values of the peaks of the plurality of waveforms of the output current ID of the motor detected by the detection circuit are the same. As indicated by a broken line a2 shown in fig. 5, the current values of the valleys of the plurality of waveforms of the output current ID of the motor detected by the detection circuit are the same.

The detection circuit detects the motor in a frequency modulation region (i.e., a waveform section having a higher frequency) of the drive signal, has a higher detection frequency and a higher resolution than the detection circuit detects the motor in a waveform section having a lower frequency, and can detect a current value and an electromotive force of the motor more accurately because the number of times of detection per unit time is larger. After detecting that the electromotive force or the current value of the motor is zero, the motor driving circuit can drive third harmonic wave or sine wave to the motor in real time or after a preset time.

Referring to fig. 1, fig. 6 and fig. 7, fig. 6 is a waveform diagram of a triangular wave signal, a sinusoidal wave signal, a triangular wave level signal, a motor driving signal and a node voltage signal of a motor provided by the motor driving system and method with a frequency conversion mechanism according to the embodiment of the present invention; fig. 7 is a waveform diagram of a node voltage signal and a current flowing signal of a motor to which the system and method for driving a motor with a frequency conversion mechanism according to an embodiment of the present invention are applied.

The oscillating circuit 20 shown in fig. 1 may generate a first oscillating signal as well as a second oscillating signal. The multi-frequency signal generating circuit 30 shown in fig. 1 generates a multi-frequency signal according to the first oscillation signal and the second oscillation signal. As shown in fig. 6, the multi-frequency signal has a high-frequency waveform section TRMH with a high-frequency oscillation frequency in the frequency modulation region WN and a low-frequency waveform section TRML with a low-frequency oscillation frequency outside the frequency modulation region WN.

The falling edge of the low-frequency waveform section TRLEL of the triangular level signal is aligned with the peak of the low-frequency waveform section TRML of the multi-frequency signal, and the falling edge of the high-frequency waveform section TRLEH is aligned with the peak of the high-frequency waveform section TRMH of the multi-frequency signal.

The motor driving circuit 40 compares the multi-frequency signal with the sine wave signal SIML to generate a driving signal to be output to the motor to drive the motor to operate. The driving signal has a high frequency waveform section DMTH with a high frequency oscillation frequency in the frequency modulation region WN, and a low frequency waveform section DMTL with a low frequency oscillation frequency outside the frequency modulation region WN.

The motor, such as a three-phase motor, may include a U-phase, a V-phase, and a W-phase. The motor driving circuit 40 shown in fig. 1 may include an upper bridge switch and a lower bridge switch for the U-phase, an upper bridge switch and a lower bridge switch for the V-phase, and an upper bridge switch and a lower bridge switch for the W-phase. And a node between the upper bridge switch and the lower bridge switch of the U phase is connected with one end of the coil of the U phase of the motor. The node between the upper and lower bridge switches of the V-phase is connected to one end of the V-phase coil of the motor. The node between the upper and lower bridge switches of the W phase is connected to one end of the W phase coil of the motor. The other end of the coil of the U-phase, the other end of the coil of the V-phase and the other end of the coil of the W-phase are connected to a common point.

In order to avoid the short circuit when the upper bridge switch and the lower bridge switch of any one of the U-phase, V-phase or W-phase of the motor are simultaneously turned on, a switching Time, also referred to as Dead Time (Dead Time), is provided during the switching process between the upper bridge switch and the lower bridge switch.

For example, during the Dead Time (Dead Time), when current flows from the V-phase to the W-phase, the negative half-cycle waveform of current flow signal ILEV shown in fig. 7 indicates that current is in reverse flow for the W-phase. In this process, a current flows through the internal diode of the W-phase upper bridge switch and toward the input voltage source connected to the W-phase upper bridge switch. As a result, the node voltage signal shown in fig. 6 and 7 has a concave waveform in the high frequency waveform section VLDH in the frequency modulation region WN, which represents that the voltage (e.g., 5.7V) of the node voltage signal at the node between the W-phase upper bridge switch and the W-phase lower bridge switch is equal to the output voltage (e.g., 5V) of the input voltage source VCC plus the voltage (e.g., 0.7V) of the internal diode.

Conversely, during the dead time, when current flows from the W-phase to the V-phase, the positive half-cycle waveform of current flow signal ILEV shown in fig. 7 indicates that current is downstream for the W-phase. In this process, the current flows through the internal diode of the lower bridge switch of the W phase, then flows out of the W phase, and finally flows into the V phase. When a current flows through the internal diode of the W-phase lower bridge switch, the node voltage signal shown in fig. 6 has a concave waveform in the high frequency waveform section VLDH in the frequency modulation region WN, which represents that the voltage (e.g., -0.7V) of the node voltage signal, which is the node between the W-phase upper bridge switch and the lower bridge switch, is equal to the ground voltage GND (e.g., 0V) minus the voltage (e.g., 0.7V) of the internal diode.

Therefore, the voltage of the node between the upper bridge switch and the lower bridge switch of any one of the U-phase, the V-phase or the W-phase, i.e. the voltage value of the node voltage signal, can be detected to determine the flowing direction of the current, such as the reverse flow or the forward flow.

As shown in fig. 7, the motor driving system with the frequency conversion mechanism according to the embodiment of the present invention may further include a comparator CMP. The first input terminal of the comparator CMP is connected to a node between the upper and lower bridge switches of any of the U-phase, V-phase, or W-phase of the motor, so as to obtain a voltage at the node, i.e., a voltage of the node voltage signal. In addition, the comparator CMP can obtain the reference voltage VR from a reference voltage source. The comparator CMP may be configured to compare the node voltage (e.g., -0.7V), i.e., the voltage of the node voltage signal, with a reference voltage VR (e.g., -0.35V), for example, to output a comparison signal, so as to provide a basis for controlling the motor by the motor driving circuit 40 shown in FIG. 1. Therefore, in the detection section, the time point when the current waveform changes from concave-up to concave-down, or from concave-down to concave-up, can switch the frequency through the higher U-phase, V-phase or W-phase, so as to avoid missing the time point when the true current is zero. And obtaining more accurate zero credit.

[ advantageous effects of the embodiments ]

In summary, the present invention provides a motor driving system and method with a frequency conversion mechanism, which utilizes an oscillation circuit to generate a plurality of oscillation signals with different oscillation frequencies, and generates a multi-frequency signal with a high-frequency waveform section and a low-frequency waveform section according to the plurality of oscillation signals, wherein the current and the electromotive force of the motor are detected with a higher detection frequency and a higher resolution in a time interval of the high-frequency waveform section, so that the current and the electromotive force can be accurately detected in real time as parameter conditions for driving the motor, thereby improving the operating efficiency of the motor, and the low-frequency waveform section is provided to reduce switching loss and power consumption when the detection operation is not performed.

The disclosure above is only a preferred embodiment of the present invention and is not intended to limit the claims, so that all the modifications and equivalents of the disclosure and drawings are included in the claims.