Multiphase motor driving circuit and multiphase motor driving method

Abstract

The invention discloses a multiphase motor driving circuit and a multiphase motor driving method. The multiphase motor driving circuit comprises a power stage circuit; and a control circuit. In the motor braking mode, when the maintaining voltage is smaller than a first voltage threshold value, the control circuit enters a first sub-mode, and in the first sub-mode, the control circuit controls at least one part of switches in the power level circuit to perform periodic switching through a pulse width modulation signal so as to convert the back electromotive force of the multi-phase motor into the maintaining voltage, and then the maintaining voltage is supplied to the control circuit. In the motor braking mode, when the maintaining voltage is larger than a second voltage threshold value, the control circuit enters a second sub-mode, in the second sub-mode, the control circuit controls at least one part of switches in the power level circuit through pulse width modulation signals to enable the switches to be constantly turned on, and therefore the counter electromotive force of the multi-phase motor is consumed to reduce the rotating speed of the multi-phase motor.

Description

Technical Field

[0001] The present invention relates to a multi-phase motor driving circuit and a multi-phase motor driving method, and in particular to a multi-phase motor driving circuit and a multi-phase motor driving method that do not require additional external circuits to achieve power-off braking. Background Art

[0002] Figure 1A and Figure 1B FIG. 1 is a diagram showing a known multi-phase motor driving circuit. Figure 1A The known technique shown uses additional external circuits 1, 2, 3 to achieve power-off braking. Each low-side transistor requires an additional set of external circuits. Figure 1B The above-mentioned additional external circuits 1, 2, and 3 are shown (as shown by the dotted line), which include three resistors R1, R2, and R3 and a transistor Q1. LO is the gate signal from the control circuit 101. When the power is off, the supply voltage VCC will drop instantly, and the maintenance voltage VCF will be maintained for a short time according to the capacity of the capacitor Cf. At this time, the transistor Q1 will be turned off due to the pull-down of the resistor R2, and the voltage Vgs will be divided by the voltage divider formed by the resistor R3 and the resistor Rs, and then the three-phase low-end transistors will be turned on. The multi-phase motor thus starts to brake effectively. Here, the larger the capacitor Cf, the longer the maintenance voltage VCF can be maintained, which means that the capacitor Cf is the key to determining the braking time.

[0003] However, in the above-mentioned known technology, the hardware design is relatively complex and requires additional external components, cost and space. The braking time is determined by the timing of the capacitor Cf and the conduction of the low-end transistor. The selection of the capacitor Cf, the resistor and the low-end transistor should be accurately calculated. In order to have a sufficiently long braking time to completely brake the motor, the capacitance value of the capacitor Cf needs to be increased, thereby increasing the cost and space.

[0004] In view of this, the present invention aims at addressing the above-mentioned deficiencies in the prior art and proposes a multi-phase motor driving circuit and a multi-phase motor driving method that do not require the above-mentioned additional external circuits. Summary of the invention

[0005] In one viewpoint, the present invention provides a multi-phase motor drive circuit including: a power stage circuit coupled between a holding voltage and a multi-phase motor, the power stage circuit being used to operate the multi-phase motor according to a pulse width modulation signal; and a control circuit being used to generate the pulse width modulation signal according to the power source provided by the holding voltage; wherein in a motor braking mode, when the holding voltage is less than a first voltage threshold, a first sub-mode is entered, wherein in the first sub-mode, the control circuit controls at least a portion of the switches in the power stage circuit to perform periodic switching through the pulse width modulation signal, so as to convert the back electromotive force of the multi-phase motor into the holding voltage, thereby supplying power to the control circuit; wherein in the motor braking mode, when the holding voltage is greater than a second voltage threshold, a second sub-mode is entered, wherein in the second sub-mode, the control circuit controls at least a portion of the switches in the power stage circuit through the pulse width modulation signal to make it constantly turned on, thereby consuming the back electromotive force of the multi-phase motor to reduce the rotation speed of the multi-phase motor.

[0006] In a preferred embodiment, in the motor braking mode, the first sub-mode is entered only when the maintenance voltage is less than the first voltage threshold and the rotation speed of the multi-phase motor is greater than a rotation speed threshold.

[0007] In a preferred embodiment, the multi-phase motor drive circuit also includes a path switch coupled between an input voltage and the maintenance voltage; wherein in a motor operation mode, the path switch is controlled to be turned on to electrically connect the maintenance voltage to the input voltage, wherein the control circuit controls the switching of multiple switches in the power stage circuit through the pulse width modulation signal, thereby converting the maintenance voltage to generate a driving voltage to drive the multi-phase motor to rotate; wherein when the path switch is not conducting and waits for a stabilization time, the motor braking mode is entered.

[0008] In a preferred embodiment, the multi-phase motor driving circuit further includes a holding capacitor coupled to the holding voltage, wherein in the first sub-mode of the motor braking mode, the back electromotive force of the multi-phase motor is converted into the holding voltage to charge the holding capacitor.

[0009] In a preferred embodiment, the power stage circuit includes a multi-phase inverter circuit, wherein the multi-phase inverter circuit includes multiple upper bridge switches and multiple lower bridge switches, wherein the multiple upper bridge switches are coupled between the maintenance voltage and the corresponding multiple switching nodes, the multiple lower bridge switches are coupled between the corresponding multiple switching nodes and a ground potential, and the multi-phase motor is coupled to the multiple switching nodes.

[0010] In a preferred embodiment, in the second sub-mode of the motor braking mode, the control circuit controls the multiple lower bridge switches in the power stage circuit through the pulse width modulation signal, so that the multiple lower bridge switches are constantly turned on, thereby consuming the back electromotive force of the multi-phase motor to reduce the rotational speed of the multi-phase motor.

[0011] In a preferred embodiment, in the first sub-mode of the motor braking mode, the control circuit controls the multiple lower bridge switches in the power stage circuit to perform periodic switching through the pulse width modulation signal, so as to convert the back electromotive force of the multi-phase motor into the maintenance voltage through reverse boost conversion, thereby supplying power to the control circuit.

[0012] In a preferred embodiment, in the first sub-mode of the motor braking mode, the control circuit controls the multiple upper bridge switches in the power stage circuit through the pulse width modulation signal, so that the multiple upper bridge switches are non-conductive, and then asynchronous reverse boost conversion is performed through the body diodes of the multiple upper bridge switches.

[0013] In a preferred embodiment, in the first sub-mode of the motor braking mode, the control circuit also controls the multiple upper bridge switches in the power stage circuit to perform periodic switching through the pulse width modulation signal, so as to convert the back electromotive force of the multi-phase motor into the maintenance voltage through reverse boost conversion, thereby supplying power to the control circuit.

[0014] In a preferred embodiment, in the first sub-mode of the motor braking mode, there is a delay time between the end time of the conduction of the multiple lower bridge switches and the start time of the conduction of the multiple upper bridge switches, and / or between the end time of the conduction of the multiple upper bridge switches and the start time of the conduction of the multiple lower bridge switches. During the delay time, the multiple upper bridge switches and the multiple lower bridge switches are both non-conductive, wherein the delay time is determined based on at least one characteristic parameter of the multi-phase motor and a preset braking time.

[0015] In a preferred embodiment, in the first sub-mode of the motor braking mode, when the multiple upper bridge switches are turned on, or when the multiple lower bridge switches are turned on, the multi-phase motor forms a short-circuit loop, thereby consuming the back electromotive force of the multi-phase motor to reduce the rotational speed of the multi-phase motor.

[0016] In a preferred embodiment, the control circuit generates a ramp signal, and the conduction start time points of the multiple upper bridge switches and the conduction start time points of the multiple lower bridge switches are determined according to the crossing time points of the ramp signal with a third voltage threshold and a fourth voltage threshold, respectively.

[0017] In a preferred embodiment, the first voltage threshold is a hysteresis voltage lower threshold, and the second voltage threshold is a hysteresis voltage upper threshold, wherein the hysteresis voltage lower threshold is smaller than the hysteresis voltage upper threshold, and the first sub-mode and the second sub-mode form hysteresis control so that the maintenance voltage varies between the hysteresis voltage upper threshold and the hysteresis voltage lower threshold.

[0018] In a preferred embodiment, the multi-phase motor driving circuit further includes a voltage regulator for converting the maintenance voltage into a supply voltage to supply power to the control circuit.

[0019] In a preferred embodiment, the first voltage threshold is greater than or equal to a minimum operating voltage of the control circuit.

[0020] In another viewpoint, a multi-phase motor driving method is provided for driving a multi-phase motor, wherein the multi-phase motor is coupled to a power stage circuit, wherein the power stage circuit includes a plurality of switches, and the multi-phase motor driving method includes: turning off the power supply of the multi-phase motor; when a maintaining voltage is less than a first voltage threshold, entering a motor braking mode; in the motor braking mode, when the maintaining voltage is less than the first voltage threshold, entering a first sub-mode, wherein in the first sub-mode, at least a portion of the switches among the plurality of switches are controlled to be periodically switched to convert the back electromotive force of the multi-phase motor into the maintaining voltage for power supply; and in the motor braking mode, when the maintaining voltage is greater than a second voltage threshold, entering a second sub-mode, wherein in the second sub-mode, at least a portion of the switches among the plurality of switches are controlled to be constantly turned on, thereby consuming the back electromotive force of the multi-phase motor to reduce the rotational speed of the multi-phase motor.

[0021] In a preferred embodiment, after the step of entering the motor braking mode when the maintaining voltage is less than the first voltage threshold, the method further includes: waiting for a stabilization time.

[0022] In a preferred embodiment, the multi-phase motor driving method also includes: in a motor operation mode, controlling the path switch to be conductive to electrically connect the maintenance voltage to the input voltage, and controlling multiple switches in the power stage circuit to switch, thereby converting the maintenance voltage to generate a driving voltage to drive the multi-phase motor to rotate, wherein the maintenance voltage is coupled to an input voltage through a path switch, and the step of shutting off the power supply of the multi-phase motor includes making the path switch non-conductive.

[0023] In a preferred embodiment, the multi-phase motor is coupled to the multiple switching nodes, wherein the step of reducing the rotational speed of the multi-phase motor includes: in the second sub-mode, controlling the multiple lower bridge switches in the power stage circuit so that the multiple lower bridge switches are constantly turned on, thereby consuming the back electromotive force of the multi-phase motor to reduce the rotational speed of the multi-phase motor.

[0024] In a preferred embodiment, the step of converting the back electromotive force of the multi-phase motor into the maintenance voltage for power supply includes: in the first sub-mode, controlling the multiple lower bridge switches in the power stage circuit to perform periodic switching to convert the back electromotive force of the multi-phase motor into the maintenance voltage through reverse boost conversion for power supply.

[0025] In a preferred embodiment, the step of converting the back electromotive force of the multi-phase motor into the maintenance voltage for power supply includes: in the first sub-mode, controlling the multiple upper bridge switches in the power stage circuit so that the multiple upper bridge switches are non-conducting, and then performing asynchronous reverse boost conversion through the body diodes of the multiple upper bridge switches.

[0026] In a preferred embodiment, the step of converting the back electromotive force of the multi-phase motor into the maintenance voltage for power supply also includes: in the first sub-mode, controlling the multiple upper bridge switches in the power stage circuit so that the multiple upper bridge switches are periodically switched to convert the back electromotive force of the multi-phase motor into the maintenance voltage through reverse boost conversion for power supply.

[0027] In a preferred embodiment, the multi-phase motor driving method also includes generating a ramp signal, wherein the conduction starting time points of the multiple upper bridge switches and the conduction starting time points of the multiple lower bridge switches are determined based on the crossing time points of the ramp signal with a third voltage threshold and a fourth voltage threshold.

[0028] In a preferred embodiment, the multi-phase motor driving method further includes converting the sustaining voltage into a supply voltage, wherein the supply voltage is lower than the sustaining voltage.

[0029] In a preferred embodiment, the multi-phase motor driving method further includes: when the maintenance voltage is less than a minimum voltage or the rotation speed of the multi-phase motor is less than the rotation speed threshold, completing a shutdown procedure of the multi-phase motor.

[0030] The advantages of the present invention are that the present invention does not require an additional circuit to achieve power-off braking, the capacitor volume of the present invention is small, and the circuit design of the present invention is simple.

[0031] The following is a detailed description through specific embodiments to make it easier to understand the purpose, technical content, characteristics and effects achieved by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1A and Figure 1B FIG. 1 is a diagram showing a known multi-phase motor driving circuit.

[0033] Figure 2A FIG. 4 is a circuit diagram showing a multi-phase motor driving circuit according to an embodiment of the present invention.

[0034] Figure 2B FIG. 4 is a circuit diagram showing a multi-phase motor driving circuit according to another embodiment of the present invention.

[0035] Figure 3A FIG. 4 is a schematic diagram showing signal waveforms of related signals of a multi-phase motor driving circuit according to an embodiment of the present invention.

[0036] Figure 3B FIG. 4 is a schematic diagram showing signal waveforms of related signals of a multi-phase motor driving circuit according to another embodiment of the present invention.

[0037] Figure 3C FIG. 4 is a schematic diagram showing signal waveforms of related signals of a multi-phase motor driving circuit according to an embodiment of the present invention.

[0038] Figure 3D FIG. 4 is a schematic diagram showing signal waveforms of related signals of a multi-phase motor driving circuit according to an embodiment of the present invention.

[0039] Figure 4A-4C 1 is a circuit diagram and an operation diagram showing a multi-phase motor driving circuit according to an embodiment of the present invention.

[0040] Figure 4D FIG. 4 is a simplified circuit diagram showing a multi-phase motor driving circuit according to an embodiment of the present invention.

[0041] Figure 5A is a flow chart showing the steps of a multi-phase motor driving method according to an embodiment of the present invention.

[0042] Figure 5B is a flowchart showing a multi-phase motor driving method according to another embodiment of the present invention.

[0043] Figure 5C is a flowchart showing a multi-phase motor driving method according to another embodiment of the present invention.

[0044] Explanation of symbols in the figure

[0045] 1, 2, 3: Additional external circuits

[0046] 101, 202: Control circuit

[0047] 20: Multi-phase motor drive circuit

[0048] 201: Power stage circuit

[0049] 203: Voltage Regulator

[0050] 30: Multiphase motor

[0051] 40: Multi-phase motor driving method

[0052] 401~411: Steps

[0053] Cf: (holding) capacitance

[0054] dUH, dUL, dVH, dVL, dWH, dWL: pulse width modulation signals

[0055] EMF: Back Electromotive Force

[0056] Io1: output current

[0057] LO: Gate signal

[0058] LX1, LX2, LX3: Switching nodes

[0059] Q1: Transistor

[0060] Qh1, Qh2, Qh3, Qhe: (upper bridge) switch

[0061] Ql1, Ql2, Ql3, Qle: (lower bridge) switch

[0062] R1, R2, R3, Rs: resistors

[0063] Sb: Braking strength

[0064] Sp: Path switch

[0065] Td: delay time

[0066] Ton_hs: On-time of the upper bridge switch

[0067] Ton_ls: On-time of the lower bridge switch

[0068] Tsw: switching period

[0069] VCC: supply voltage

[0070] VCF: Holding voltage

[0071] Vgs: voltage

[0072] Vhys_H: hysteresis voltage upper threshold

[0073] Vhys_L: Hysteresis voltage lower threshold

[0074] VIN: Input voltage

[0075] Vmin: minimum voltage

[0076] Vo, Vo1, Vo2, Vo3: driving voltage

[0077] Vramp: ramp signal

[0078] Vth1, Vth2, Vth3, Vth4: voltage thresholds DETAILED DESCRIPTION

[0079] The diagrams in the present invention are all schematic, and are mainly intended to show the coupling relationship between various circuits and the relationship between various signal waveforms. The circuits, signal waveforms and frequencies are not drawn according to scale.

[0080] Figure 2A FIG. 1 is a circuit diagram showing a multi-phase motor driving circuit according to an embodiment of the present invention. Figure 2A As shown, the multi-phase motor driving circuit 20 of the present invention includes a power stage circuit 201 and a control circuit 202. The power stage circuit 201 is coupled between the maintenance voltage VCF and the multi-phase motor 30. The power stage circuit 201 is used to operate the multi-phase motor 30 according to the pulse width modulation (PWM) signals dUH, dUL, dVH, dVL, dWH, dWL. In one embodiment, the power stage circuit 201 includes a multi-phase inverter circuit. In one embodiment, the multi-phase inverter circuit includes a plurality of upper bridge switches Qh1, Qh2, Qh3 and a plurality of lower bridge switches Ql1, Ql2, Ql3. The plurality of upper bridge switches Qh1, Qh2, Qh3 are coupled between the maintenance voltage VCF and the corresponding plurality of switching nodes LX1, LX2, LX3, and the plurality of lower bridge switches Ql1, Ql2, Ql3 are coupled between the corresponding plurality of switching nodes LX1, LX2, LX3 and the ground potential. The multi-phase motor 30 is coupled to a plurality of switching nodes LX1, LX2, and LX3. The control circuit 202 is used to generate pulse width modulation signals dUH, dUL, dVH, dVL, dWH, and dWL according to the power provided by the maintenance voltage VCF. In a motor operation mode, the control circuit 202 generates the pulse width modulation signals dUH, dUL, dVH, dVL, dWH, and dWL to control the switching of a plurality of switches Qh1, Ql1, Qh2, Ql2, Qh3, and Ql3 in the power stage circuit 201, thereby converting the maintenance voltage VCF to generate a driving voltage Vo to drive the multi-phase motor 30 to rotate. In one embodiment, the multi-phase motor 30 may be, for example, a multi-phase motor of a fan. In one embodiment, the multi-phase motor 30 may be, for example, a brushless DC motor.

[0081] like Figure 2A As shown, the multi-phase motor driving circuit 20 further includes a path switch Sp and a holding capacitor Cf. The path switch Sp is coupled between the input voltage VIN and the holding voltage VCF. In the motor operation mode, the path switch Sp is controlled to be turned on to electrically connect the holding voltage VCF to the input voltage VIN. The holding capacitor Cf is coupled to the holding voltage VCF.

[0082] Figure 2BFIG. 1 is a circuit diagram showing a multi-phase motor driving circuit according to an embodiment of the present invention. Figure 2A The embodiment of the invention is different in that, Figure 2B As shown, the multi-phase motor driving circuit 20 further includes a regulator 203 (eg, a low dropout linear regulator) for converting the sustaining voltage VCF into a supply voltage VCC to supply power to the control circuit 202 .

[0083] Figure 3A 1 is a schematic diagram showing the signal waveforms of related signals of a multi-phase motor driving circuit according to an embodiment of the present invention. The sustaining voltage VCF, the pulse width modulation signals dUH, dUL, dVH, dVL, dWH, dWL are shown in FIG. Figure 3A Before time point t0, the multi-phase motor driving circuit operates in the motor operation mode, the maintenance voltage VCF is equal to the input voltage VIN, and the pulse width modulation signals dUH, dUL, dVH, dVL, dWH, dWL are switched to control the switching of multiple switches Qh1, Ql1, Qh2, Ql2, Qh3, Ql3 in the power stage circuit 201, thereby converting the maintenance voltage VCF to generate the driving voltage Vo to drive the multi-phase motor 30 to rotate. Then at time point t0, the path switch Sp is turned off, and the maintenance voltage VCF decreases accordingly.

[0084] Continue reading Figure 3A In one embodiment, in the motor braking mode, when the voltage VCF is maintained less than the voltage threshold Vth1 (time point t1), the first sub-mode is entered. In another embodiment, in the motor braking mode, when the voltage VCF is maintained less than the voltage threshold Vth1 and the speed of the multi-phase motor 30 is greater than the speed threshold, the first sub-mode is entered. Please also refer to Figure 3A and Figure 2A In the first sub-mode, the control circuit 202 controls at least a portion of the switches in the power stage circuit 201, such as but not limited to the lower bridge switches Ql1, Ql2, Ql3, to perform periodic switching through the pulse width modulation signals dUL, dVL, and dWL, so as to convert the back electromotive force EMF of the multi-phase motor 30 into a maintenance voltage VCF through reverse boost conversion, thereby supplying power to the control circuit 202 and charging the maintenance capacitor Cf. Figure 3A and Figure 2A As shown, in the first sub-mode of the motor braking mode, the control circuit 202 controls, for example, a plurality of upper bridge switches Qh1, Qh2, Qh3 in the power stage circuit 201 through the pulse width modulation signals dUH, dVH, and dWH, so that the plurality of upper bridge switches Qh1, Qh2, and Qh3 are always non-conductive, and then the body diodes of the plurality of upper bridge switches Qh1, Qh2, and Qh3 are used to perform asynchronous reverse boost conversion, as shown in FIG. Figure 3AAs shown, the maintenance voltage VCF rises from time t1 due to the reverse boost conversion. In one embodiment, the voltage threshold Vth1 is greater than or equal to the minimum operating voltage of the control circuit 202, so that the control circuit 202 can still operate to control the power stage circuit 201 in the motor braking mode.

[0085] like Figure 3A As shown, in the motor braking mode, when the maintenance voltage VCF rises to a value greater than the voltage threshold Vth2 (time point t2), the second sub-mode is entered. Figure 3A and Figure 2A In the second sub-mode, the control circuit 202 controls at least a portion of the switches in the power stage circuit 201, such as but not limited to the lower bridge switches Ql1, Ql2, Ql3, through the pulse width modulation signals dUL, dVL, dWL, so that they are always turned on, thereby consuming the back electromotive force EMF of the multi-phase motor 30 to reduce the speed of the multi-phase motor 30. Figure 3A and Figure 2A As shown, in one embodiment, in the second sub-mode of the motor braking mode, the plurality of upper bridge switches Qh1 , Qh2 , and Qh3 are still controlled to be constantly non-conductive.

[0086] In one embodiment, the voltage threshold Vth1 is the hysteresis voltage lower limit threshold Vhys_L, and the voltage threshold Vth2 is the hysteresis voltage upper limit threshold Vhys_H, wherein the hysteresis voltage lower limit threshold Vhys_L is less than the hysteresis voltage upper limit threshold Vhys_H, and the first sub-mode and the second sub-mode form hysteresis control, so that the maintenance voltage VCF varies between the hysteresis voltage upper limit threshold Vhys_H and the hysteresis voltage lower limit threshold Vhys_L.

[0087] Figure 3B FIG. 1 is a schematic diagram showing the signal waveforms of related signals of a multi-phase motor driving circuit according to another embodiment of the present invention. The sustaining voltage VCF, the pulse width modulation signals dUH, dUL, dVH, dVL, dWH, dWL are shown in FIG. Figure 3B This embodiment is similar to Figure 3A The difference is that please also refer to Figure 3B and Figure 2A, during the period from time t1 to time t2, in the first sub-mode of the motor braking mode, the control circuit 202 also controls the multiple upper bridge switches Qh1, Qh2, Qh3 in the power stage circuit 201 to perform periodic switching through the pulse width modulation signals dUH, dVH, and dWH, so as to convert the back electromotive force EMF of the multi-phase motor 30 into the maintenance voltage VCF through the reverse boost conversion, and then supply power to the control circuit 202. In this embodiment, in the first sub-mode of the motor braking mode, since the upper bridge switches Qh1, Qh2, Qh3 and the lower bridge switches Ql1, Ql2, Ql3 are switched alternately and periodically, the conduction and non-conduction time of the upper bridge switches Qh1, Qh2, Qh3 and the lower bridge switches Ql1, Ql2, Ql3 are more balanced, and thus the life of the upper bridge switches and the lower bridge switches can be balanced and extended.

[0088] Figure 3C 1 is a schematic diagram showing the signal waveforms of related signals of a multi-phase motor driving circuit according to an embodiment of the present invention. The ramp signal Vramp, the pulse width modulation signals dUH, dUL, dVH, dVL, dWH, dWL are shown in FIG. Figure 3C In. Figure 3C As shown, in the first sub-mode of the motor braking mode, between the end time point of the conduction of the plurality of lower bridge switches Ql1, Ql2, Ql3 (e.g., time point t1) and the start time point of the conduction of the plurality of upper bridge switches Qh1, Qh2, Qh3 (e.g., time point t2), and / or, between the end time point of the conduction of the plurality of upper bridge switches Qh1, Qh2, Qh3 (e.g., time point t3) and the start time point of the conduction of the plurality of lower bridge switches Ql1, Ql2, Ql3 (e.g., time point t4), a delay time Td is included. In one embodiment, the delay time Td can be obtained by the following equations (1) and (2):

[0089]

[0090] Wherein Tsw is the switching period, Sb is the braking strength (%), Ton_hs is the conduction time of the upper bridge switch, and Ton_ls is the conduction time of the lower bridge switch. In one embodiment, the longer the delay time Td is, the smaller the braking strength Sb is. Within the delay time Td, the plurality of upper bridge switches Qh1, Qh2, Qh3 and the plurality of lower bridge switches Ql1, Ql2, Ql3 are all non-conductive. In one embodiment, the delay time Td is adjustable.

[0091] In one embodiment, the delay time Td is determined according to at least one characteristic parameter of the multi-phase motor 30 and a preset braking time. Figure 2A and Figure 3C, the control circuit 202 generates a ramp signal Vramp, and the start time of the conduction of the plurality of upper bridge switches Qh1, Qh2, Qh3 and the start time of the conduction of the plurality of lower bridge switches Ql1, Ql2, Ql3 are determined according to the crossing time of the ramp signal Vramp and the voltage threshold Vth3 and the voltage threshold Vth4. In one embodiment, the delay time Td also affects the duty cycle and conversion ratio of the reverse boost conversion. In other words, the delay time Td affects Figure 3A or Figure 3B For example, the rising slope of the voltage VCF is maintained during the first sub-mode, thus affecting the overall braking time. In one embodiment, in the first sub-mode, the duty cycle of the upper bridge switches Qh1, Qh2, Qh3 is the same as the duty cycle of the lower bridge switches Ql1, Ql2, Ql3.

[0092] Figure 3D FIG. 1 is a schematic diagram showing the signal waveforms of related signals of a multi-phase motor driving circuit according to an embodiment of the present invention. The voltage VCF and the output current Io1 are shown in FIG. Figure 3D Please also refer to Figure 2A and Figure 3D At time point t1, when the path switch Sp is non-conductive and after waiting for the stabilization time Ts, the motor braking mode is entered at time point t2.

[0093] Figure 4A-4B 1 is a circuit diagram and an operation diagram showing a multi-phase motor driving circuit according to an embodiment of the present invention. Figure 4A As shown, in the first sub-mode of the motor braking mode, when the multiple lower bridge switches Ql1, Ql2, and Ql3 are turned on, the multi-phase motor 30 forms a short circuit, thereby consuming the back electromotive force EMF of the multi-phase motor 30 to reduce the speed of the multi-phase motor 30. Figure 4B As shown, in the first sub-mode of the motor braking mode, when the multiple upper bridge switches Qh1, Qh2, and Qh3 are turned on, the multi-phase motor 30 forms a short-circuit loop, and the back electromotive force EMF of the multi-phase motor 30 is consumed by the resistance in the short-circuit loop to reduce the rotation speed of the multi-phase motor 30. Figure 4C 1 is a circuit diagram and an operation diagram of a multi-phase motor driving circuit according to an embodiment of the present invention. This embodiment shows that during the delay time Td, when the plurality of upper bridge switches Qh1, Qh2, Qh3 and the lower bridge switches Ql1, Ql2, Ql3 are all non-conductive, the multi-phase motor 30 forms a short circuit through the body diodes of the upper bridge switches Qh1, Qh2 and the lower bridge switch Ql3, and charges the holding capacitor Cf to provide a holding voltage VCF to power the control circuit 202, while also consuming the back electromotive force EMF of the multi-phase motor 30 to reduce the speed of the multi-phase motor 30.

[0094] Figure 4DFIG. 1 is a simplified circuit diagram showing a multi-phase motor drive circuit according to an embodiment of the present invention. Figure 4C The upper bridge switch Qhe is equivalent to Figure 4C The upper bridge switches Qh1 and Qh2, and the lower bridge switch Qle is equivalent to Figure 4C The lower bridge switch Ql3.

[0095] Figure 5A FIG. 1 is a flowchart showing a method for driving a multi-phase motor according to an embodiment of the present invention. Figure 5A As shown, the multi-phase motor driving method 40 of the present invention includes, in step 401, confirming whether the path switch Sp is turned on. If not, it means that the power supply of the multi-phase motor 30 is turned off, and then proceed to step 404. In step 404, confirm whether the maintenance voltage VCF is less than the voltage threshold Vth1 and whether the speed of the multi-phase motor 30 is greater than the speed threshold. If so, proceed to step 405. If not, return to step 404. In step 405, wait for the stabilization time. Then, in step 406, confirm whether the maintenance voltage VCF is greater than the voltage threshold Vth2. If so, proceed to step 407. If not, proceed to step 409. In step 407, control at least a part of the switches Qh1, Ql1, Qh2, Ql2, Qh3, Ql3 among the multiple switches to make them constantly turned on, thereby consuming the back electromotive force EMF of the multi-phase motor 30 to reduce the speed of the multi-phase motor 30. Next, in step 408, it is determined whether the maintenance voltage VCF is less than the voltage threshold Vth1. If so, the process proceeds to step 409. If not, the process returns to step 407. In step 409, at least a portion of the switches Qh1, Ql1, Qh2, Ql2, Qh3, and Ql3 in the plurality of switches are controlled to switch periodically to convert the back electromotive force EMF of the multi-phase motor 30 into the maintenance voltage VCF for power supply. After step 409, the process returns to step 406.

[0096] On the other hand, in step 401, if the path switch Sp is turned on, it means that the power supply of the multi-phase motor 30 is normally turned on, then proceed to steps 402 and 403: control the multiple switches Qh1, Ql1, Qh2, Ql2, Qh3, Ql3 in the power stage circuit 201 to switch, thereby converting the maintenance voltage VCF to generate the driving voltage Vo to drive the multi-phase motor 30 to rotate.

[0097] Figure 5B is a flowchart showing the steps of a multi-phase motor driving method according to another embodiment of the present invention. Figure 5AThe embodiment of the present invention is different in that when the result of step 408 is yes, the process proceeds to step 410. In step 410, it is determined whether the maintenance voltage VCF is less than the minimum voltage Vmin or whether the speed of the multi-phase motor 30 is less than the speed threshold. If so, the process proceeds to step 411. If not, the process proceeds to step 409. In step 411, the shutdown process of the multi-phase motor 30 is completed.

[0098] Figure 5C FIG. 1 is a flowchart showing the steps of a multi-phase motor driving method according to another embodiment of the present invention. Figure 5B The embodiment of the present invention is different in that step 410 of the present embodiment is followed by step 409 and step 409 is followed by step 408.

[0099] In summary, the present invention does not require an additional external circuit to achieve power-off braking, the capacitor required by the present invention is relatively small, and the circuit design of the present invention is relatively simple, thus saving costs.

[0100] The present invention has been described above with respect to the preferred embodiment, but the above is only to make it easy for those skilled in the art to understand the content of the present invention, and is not used to limit the broadest scope of the rights of the present invention. The various embodiments described are not limited to individual applications, but can also be used in combination. For example, two or more embodiments can be used in combination, and part of the components in one embodiment can also be used to replace the corresponding components in another embodiment. In addition, under the same spirit of the present invention, those skilled in the art can think of various equivalent changes and various combinations. For example, the present invention refers to "processing or calculating or generating an output result according to a certain signal", which is not limited to the signal itself, but also includes, when necessary, converting the signal to voltage and current, current and voltage, and / or ratio conversion, and then processing or calculating according to the converted signal to generate an output result. It can be seen that under the same spirit of the present invention, those skilled in the art can think of various equivalent changes and various combinations, and there are many combinations, which are not listed one by one here. Therefore, the scope of the present invention should cover the above and all other equivalent changes.

Claims

1. A multi-phase motor drive circuit, comprising: a power stage circuit coupled between a holding voltage and a multi-phase motor, the power stage circuit being used to operate the multi-phase motor according to a pulse width modulation signal; and a control circuit for generating the pulse width modulation signal according to the power provided by the sustaining voltage; In a motor braking mode, when the holding voltage is less than a first voltage threshold, a first sub-mode is entered, wherein in the first sub-mode, the control circuit controls at least a portion of the switches in the power stage circuit to perform periodic switching through the pulse width modulation signal, so as to convert the back electromotive force of the multi-phase motor into the holding voltage, thereby supplying power to the control circuit; In the motor braking mode, when the maintaining voltage is greater than a second voltage threshold, a second sub-mode is entered. In the second sub-mode, the control circuit controls at least a portion of the switches in the power stage circuit through the pulse width modulation signal to keep it constantly turned on, thereby consuming the back electromotive force of the multi-phase motor to reduce the rotational speed of the multi-phase motor.

2. The multi-phase motor drive circuit according to claim 1, wherein: In the motor braking mode, the first sub-mode is entered only when the maintenance voltage is less than the first voltage threshold and the rotation speed of the multi-phase motor is greater than a rotation speed threshold.

3. The multi-phase motor driving circuit according to claim 1, wherein: Also included is a path switch coupled between an input voltage and the maintenance voltage; wherein in a motor operation mode, the path switch is controlled to be turned on to electrically connect the sustaining voltage to the input voltage, wherein the control circuit controls the switching of a plurality of switches in the power stage circuit through the pulse width modulation signal, thereby converting the sustaining voltage to generate a driving voltage to drive the multi-phase motor to rotate; When the path switch is not conducting and after waiting for a stable time, the motor braking mode is entered.

4. The multi-phase motor driving circuit according to claim 1, wherein: The invention also includes a holding capacitor coupled to the holding voltage, wherein in the first sub-mode of the motor braking mode, the back electromotive force of the multi-phase motor is converted into the holding voltage to charge the holding capacitor.

5. The multi-phase motor driving circuit according to claim 1, wherein: The power stage circuit includes a multi-phase inverter circuit, wherein the multi-phase inverter circuit includes multiple upper bridge switches and multiple lower bridge switches, wherein the multiple upper bridge switches are coupled between the maintenance voltage and the corresponding multiple switching nodes, the multiple lower bridge switches are coupled between the corresponding multiple switching nodes and a ground potential, and the multi-phase motor is coupled to the multiple switching nodes.

6. The multi-phase motor driving circuit according to claim 5, wherein: In the second sub-mode of the motor braking mode, the control circuit controls the multiple lower bridge switches in the power stage circuit through the pulse width modulation signal, so that the multiple lower bridge switches are constantly turned on, thereby consuming the back electromotive force of the multi-phase motor to reduce the rotation speed of the multi-phase motor.

7. The multi-phase motor driving circuit according to claim 5, wherein: In the first sub-mode of the motor braking mode, the control circuit controls the multiple lower bridge switches in the power stage circuit to perform periodic switching through the pulse width modulation signal, so as to convert the back electromotive force of the multi-phase motor into the maintenance voltage through reverse boost conversion, thereby supplying power to the control circuit.

8. The multi-phase motor driving circuit according to claim 7, wherein: In the first sub-mode of the motor braking mode, the control circuit controls the multiple upper bridge switches in the power stage circuit through the pulse width modulation signal to make the multiple upper bridge switches non-conductive, thereby performing asynchronous reverse boost conversion through the body diodes of the multiple upper bridge switches.

9. The multi-phase motor driving circuit according to claim 7, wherein: In the first sub-mode of the motor braking mode, the control circuit also controls the multiple upper bridge switches in the power stage circuit to perform periodic switching through the pulse width modulation signal, so as to convert the back electromotive force of the multi-phase motor into the maintenance voltage through reverse boost conversion, thereby supplying power to the control circuit.

10. The multi-phase motor driving circuit according to claim 9, wherein: In the first sub-mode of the motor braking mode, there is a delay time between the end time of the conduction of the multiple lower bridge switches and the start time of the conduction of the multiple upper bridge switches, and / or between the end time of the conduction of the multiple upper bridge switches and the start time of the conduction of the multiple lower bridge switches. During the delay time, the multiple upper bridge switches and the multiple lower bridge switches are not conducting, wherein the delay time is determined based on at least one characteristic parameter of the multi-phase motor and a preset braking time.

11. The multi-phase motor driving circuit according to claim 9, wherein: In the first sub-mode of the motor braking mode, when the multiple upper bridge switches are turned on, or when the multiple lower bridge switches are turned on, the multi-phase motor forms a short circuit, thereby consuming the back electromotive force of the multi-phase motor to reduce the rotation speed of the multi-phase motor.

12. The multi-phase motor driving circuit according to claim 9, wherein: The control circuit generates a ramp signal. The conduction start time points of the upper bridge switches and the conduction start time points of the lower bridge switches are respectively determined according to the crossing time points of the ramp signal with a third voltage threshold and a fourth voltage threshold.

13. The multi-phase motor driving circuit according to claim 1, wherein: The first voltage threshold is a hysteresis voltage lower threshold, and the second voltage threshold is a hysteresis voltage upper threshold, wherein the hysteresis voltage lower threshold is less than the hysteresis voltage upper threshold, and the first sub-mode and the second sub-mode form hysteresis control, so that the maintenance voltage varies between the hysteresis voltage upper threshold and the hysteresis voltage lower threshold.

14. The multi-phase motor driving circuit according to claim 1, wherein: The invention also comprises a voltage stabilizer for converting the maintenance voltage into a supply voltage to supply power to the control circuit.

15. The multi-phase motor driving circuit according to claim 1, wherein: The first voltage threshold is greater than or equal to the lowest operating voltage of the control circuit.

16. A multi-phase motor driving method for driving a multi-phase motor, wherein the multi-phase motor is coupled to a power stage circuit, wherein the power stage circuit includes a plurality of switches, the multi-phase motor driving method comprising: Turning off power to the multi-phase motor; When a maintenance voltage is less than a first voltage threshold, entering a motor braking mode; In the motor braking mode, when the holding voltage is less than the first voltage threshold, a first sub-mode is entered, wherein in the first sub-mode, at least a portion of the switches among the plurality of switches are controlled to perform periodic switching to convert the back electromotive force of the multi-phase motor into the holding voltage for power supply; and In the motor braking mode, when the maintaining voltage is greater than a second voltage threshold, a second sub-mode is entered, wherein in the second sub-mode, at least a portion of the multiple switches are controlled to be constantly turned on, thereby consuming the back electromotive force of the multi-phase motor to reduce the rotational speed of the multi-phase motor.

17. The multi-phase motor driving method according to claim 16, wherein: The motor braking mode is entered when the maintenance voltage is less than the first voltage threshold and the rotation speed of the multi-phase motor is greater than a rotation speed threshold.

18. The multi-phase motor driving method according to claim 16, wherein: After the step of entering the motor braking mode when the maintaining voltage is less than the first voltage threshold, the method further includes: waiting for a stabilization time.

19. The multi-phase motor driving method according to claim 16, wherein: It also includes: in a motor operation mode, controlling the path switch to be conductive to electrically connect the maintenance voltage to the input voltage, and controlling multiple switches in the power stage circuit to switch, thereby converting the maintenance voltage to generate a driving voltage to drive the multi-phase motor to rotate, wherein the maintenance voltage is coupled to an input voltage through a path switch, and the step of shutting off the power supply of the multi-phase motor includes making the path switch non-conductive.

20. The multi-phase motor driving method according to claim 16, wherein: In the first sub-mode of the motor braking mode, the back electromotive force of the multi-phase motor is converted into the holding voltage to charge a holding capacitor, wherein the holding capacitor is coupled to the holding voltage.

21. The multi-phase motor driving method according to claim 20, wherein: The power stage circuit includes a plurality of upper bridge switches and a plurality of lower bridge switches, wherein the plurality of lower bridge switches are coupled between a plurality of switching nodes and a ground potential, wherein the plurality of upper bridge switches are coupled between the maintaining voltage and the plurality of switching nodes, and the multi-phase motor is coupled to the plurality of switching nodes, wherein the step of reducing the rotational speed of the multi-phase motor includes: in the second sub-mode, controlling the plurality of lower bridge switches in the power stage circuit so that the plurality of lower bridge switches are constantly turned on, thereby consuming the back electromotive force of the multi-phase motor to reduce the rotational speed of the multi-phase motor.

22. The multi-phase motor driving method according to claim 20, wherein: The power stage circuit includes a plurality of upper bridge switches and a plurality of lower bridge switches, wherein the plurality of lower bridge switches are coupled between a plurality of switching nodes and a ground potential, wherein the plurality of upper bridge switches are coupled between the holding voltage and the plurality of switching nodes, and the multi-phase motor is coupled to the plurality of switching nodes, wherein the step of converting the back electromotive force of the multi-phase motor into the holding voltage for power supply includes: in the first sub-mode, controlling the plurality of lower bridge switches in the power stage circuit to perform periodic switching so as to convert the back electromotive force of the multi-phase motor into the holding voltage through reverse boost conversion for power supply.

23. The multi-phase motor driving method according to claim 22, wherein: The step of converting the back electromotive force of the multi-phase motor into the maintenance voltage for power supply includes: in the first sub-mode, controlling the multiple upper bridge switches in the power stage circuit to make the multiple upper bridge switches non-conductive, and then performing asynchronous reverse boost conversion through the body diodes of the multiple upper bridge switches.

24. The multi-phase motor driving method according to claim 22, wherein: The step of converting the back electromotive force of the multi-phase motor into the maintenance voltage for power supply also includes: in the first sub-mode, controlling the multiple upper bridge switches in the power stage circuit so that the multiple upper bridge switches are periodically switched to convert the back electromotive force of the multi-phase motor into the maintenance voltage for power supply through reverse boost conversion.

25. The multi-phase motor driving method according to claim 24, wherein: In the first sub-mode of the motor braking mode, there is a delay time between the end time of the conduction of the multiple lower bridge switches and the start time of the conduction of the multiple upper bridge switches, and / or between the end time of the conduction of the multiple upper bridge switches and the start time of the conduction of the multiple lower bridge switches. During the delay time, the multiple upper bridge switches and the multiple lower bridge switches are not conducting, wherein the delay time is determined based on at least one characteristic parameter of the multi-phase motor and a preset braking time.

26. The multi-phase motor driving method according to claim 24, wherein: The method further comprises generating a ramp signal, wherein the conduction start time points of the plurality of upper bridge switches and the conduction start time points of the plurality of lower bridge switches are determined according to the crossing time points of the ramp signal, a third voltage threshold and a fourth voltage threshold.

27. The multi-phase motor driving method according to claim 16, wherein: The first voltage threshold is a hysteresis voltage lower threshold, and the second voltage threshold is a hysteresis voltage upper threshold, wherein the hysteresis voltage lower threshold is less than the hysteresis voltage upper threshold, and the first sub-mode and the second sub-mode form hysteresis control, so that the maintenance voltage varies between the hysteresis voltage upper threshold and the hysteresis voltage lower threshold.

28. The multi-phase motor driving method according to claim 16, wherein: The method also includes converting the sustain voltage into a supply voltage, wherein the supply voltage is lower than the sustain voltage.

29. The multi-phase motor driving method according to claim 17, wherein: The method also includes: when the maintenance voltage is less than a minimum voltage or the rotation speed of the multi-phase motor is less than the rotation speed threshold, completing the shutdown procedure of the multi-phase motor.

Images