Motor drive circuit and control method thereof

Abstract

The present application discloses a motor drive circuit and a control method thereof. The circuit includes an output stage circuit, a selection circuit, a first comparison circuit and a reverse current control circuit for providing a drive current for a motor. The output stage circuit includes a first and a second bridge arm coupled in parallel between an input voltage and a reference ground, the first bridge arm having a first high-side switch and a first low-side switch coupled in series, and the second bridge arm having a second high-side switch and a second low-side switch coupled in series. The selection circuit selects the common node voltage of the first bridge arm or the common node voltage of the second bridge arm as the selected common node voltage based on a Hall sensing signal. The first comparison circuit compares the selected common node voltage with the input voltage and provides a first comparison signal at the output end. Based on the first comparison signal and a polarity indication signal indicating the polarity of the drive current, the reverse current control circuit determines whether to control the first or second low-side switch to operate in a linear voltage regulation (LDO) mode.

Description

Technical Field

[0001] Embodiments of the present invention relate to a motor drive system, and more particularly to a motor drive circuit and a control method thereof for reducing voltage spikes. Background Art

[0002] Motor drives are widely used in CPU cooling fans. Figure 1 The motor drive system 100 of the prior art. The motor drive system 100 includes a motor drive circuit, which provides a drive current I for a motor 102. The motor drive circuit includes an output stage circuit 101, an input capacitor Cin, a voltage regulator device VZ connected in parallel with the input capacitor Cin, and a power supply 103 coupled to the output stage circuit 101 via a protection device D0. The output stage circuit 101 includes a bridge arm 1 and a bridge arm 2. The bridge arm 1 includes a first switch M1 and a second switch M2, and the bridge arm 2 includes a third switch M3 and a fourth switch M4. The first switch M1 and the second switch M2 are coupled in series to the input voltage V IN and the reference ground, the third switch M3 and the fourth switch M4 are coupled in series to the input voltage V IN and the reference ground. The equivalent circuit model of the motor 102 includes three parts: equivalent parasitic inductance L S , equivalent resistance R P and the induced electromotive force V t The first terminal A of the motor 102 is coupled to a common node of the first switch M1 and the second switch M2 , and the second terminal B of the motor 102 is coupled to a common node of the third switch M3 and the fourth switch M4 .

[0003] When the first switch M1 and the fourth switch M4 are turned on, and the second switch M2 and the third switch M3 are turned off, the driving current I is driven by the input voltage V IN , the first switch M1, the equivalent parasitic inductance L S , equivalent resistance R S , Induced electromotive force V t , the fourth switch M4 and the reference ground form a path. s The driving current I direction is from left to right. Figure 2 Curve I shown.

[0004] In order to maintain the torque direction unchanged, when the motor rotor rotates past the key position, the drive current I needs to be reversed. At this time, the second switch M2 and the third switch M3 are turned on, and the first switch M1 and the fourth switch M4 are turned off. Since the inductor current cannot change suddenly, the drive current I at this time passes through the second switch M2, the equivalent parasitic inductance L S , equivalent resistance R S , Induced electromotive force V t The third switch M3 flows back into the input voltage V INTherefore, the return voltage V IN The energy in the input capacitor C in Causes voltage spikes, such as Figure 2 The curve V CIN . Figure 2 : is a working waveform diagram of the motor drive system 100 in the prior art. The Hall sensing signal V HALL The positive and negative potentials change cyclically according to the rotation angle ω. Summary of the invention

[0005] Therefore, the purpose of the present invention is to solve the problem of voltage spikes in the motor drive of the prior art, and to provide a motor drive circuit and a control method for the motor drive circuit.

[0006] According to one embodiment of the present invention, a motor drive circuit is proposed, comprising: an output stage circuit, providing a drive current for the motor, comprising a first bridge arm and a second bridge arm coupled in parallel between an input voltage and a reference ground, wherein the first bridge arm has a first high-side switch and a first low-side switch coupled in series, and the second bridge arm has a second high-side switch and a second low-side switch coupled in series; a Hall detection circuit, providing a Hall sensing signal; a first selection circuit, having a first input terminal, a second input terminal, a control terminal and an output terminal, wherein the first input terminal is coupled to a common node of the first high-side switch and the first low-side switch to receive a first common node voltage, the second input terminal is coupled to a common node of the second high-side switch and the second low-side switch to receive a second common node voltage, the control terminal is coupled to the Hall detection circuit to receive the Hall sensing signal, and the first selection circuit selects the first high-side switch to be connected to the first low-side switch based on the Hall sensing signal. A common node voltage or a second common node voltage is provided to the output end as the selected common node voltage; a current polarity detection circuit generates a polarity indication signal indicating the polarity of the driving current; a first comparison circuit has a first input end, a second input end and an output end, wherein the first input end receives an input voltage, and the second input end is coupled to the output end of the selection circuit, the first comparison circuit compares the selected common node voltage with the input voltage and provides a first comparison signal at the output end; and a reverse current control circuit determines whether to control the first low-side switch or the second low-side switch to operate in a linear voltage regulation (LDO) mode based on the first comparison signal and the polarity indication signal, wherein the LDO mode controls the conduction degree of the first low-side switch or the second low-side switch to keep the selected common node voltage unchanged, and the driving current flows to the reference ground through the first low-side switch and the second low-side switch.

[0007] According to another embodiment of the present invention, a control method for a motor drive circuit is proposed, the motor drive circuit includes an output stage circuit that provides a drive current for the motor, the output stage circuit includes a first bridge arm and a second bridge arm coupled in parallel between an input voltage and a reference ground, wherein the first bridge arm includes a first high-side switch and a first low-side switch coupled in series, and the second bridge arm includes a second high-side switch and a second low-side switch coupled in series, the control method includes: based on a Hall sensing signal, selecting a first common node voltage of a common node of a first high-side switch and a first low-side switch or a second common node voltage of a common node of a second high-side switch and a second low-side switch as a selected common node voltage; comparing the selected common node voltage with the input voltage to generate a first comparison signal; providing a polarity indication signal indicating the polarity of the drive current; and based on the first comparison signal and the polarity indication signal, determining whether to control the first low-side switch or the second low-side switch to operate in an LDO mode, wherein the LDO mode is to control the conduction degree of the first low-side switch or the second low-side switch to keep the selected common node voltage unchanged, and the drive current flows to the reference ground through the first low-side switch and the second low-side switch.

[0008] According to an embodiment of the present invention, when the motor driving circuit provided by the present invention detects that the voltage of the selected switch node increases to the input voltage and the polarity of the driving current is reversed, the motor driving circuit controls the corresponding low-side switch to operate in LDO mode to prevent the driving current from flowing back to the input voltage and reduce voltage spikes. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The following drawings illustrate embodiments of the present invention. These drawings and embodiments provide some examples of the present invention in a non-limiting and non-exhaustive manner.

[0010] Figure 1 This is a motor drive system 100 in the prior art.

[0011] Figure 2 FIG. 1 is a working waveform diagram of the motor drive system 100 in the prior art.

[0012] Figure 3 2 is a motor driving system 200 according to an embodiment of the present invention.

[0013] Figure 4 According to an embodiment of the present invention Figure 3 The working waveform of the motor drive circuit shown.

[0014] Figure 5 FIG. 2 is a motor driving system 200A according to yet another embodiment of the present invention.

[0015] Figure 6 FIG. 2 is a motor driving system 200B according to yet another embodiment of the present invention.

[0016] Figure 7 According to an embodiment of the present invention Figure 6 The working waveform of the motor drive circuit shown.

[0017] Figure 8 FIG. 3 is a flow chart 300 of a control method for a motor driving circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The motor drive circuit and control method thereof according to the embodiment of the present invention are described in detail below. In the following description, some specific details, such as the specific circuit structure in the embodiment and the specific parameters of these circuit elements, are used to provide a better understanding of the embodiment of the present invention. It can be understood by those skilled in the art that the embodiment of the present invention can be implemented even in the absence of some details or in the combination of other methods, elements, materials, etc.

[0019] Figure 3 FIG. 2 is a circuit diagram of a motor drive system 200 according to an embodiment of the present invention. Figure 3 As shown, the motor drive system 200 includes a motor drive circuit that provides a drive current I1 for a motor 202. The motor drive circuit includes an output stage circuit 201, an input capacitor C IN , and the input capacitor C IN The parallel-connected voltage regulator VZ, the power supply 203 coupled to the output stage circuit 201 via the protection device D0, the Hall detection circuit 204, the selection circuit 205, the first comparison circuit 206, the current polarity detection circuit 207, the reverse current control circuit 208 and the control signal generation circuit 209.

[0020] The output stage circuit 201 includes a first bridge arm and a second bridge arm coupled in parallel between an input voltage VIN and a reference ground. The first bridge arm has a first high-side switch Q1 and a first low-side switch Q2 coupled in series, and the second bridge arm has a second high-side switch Q3 and a second low-side switch Q4 coupled in series. The Hall detection circuit 204 generates a Hall sensing signal V according to the position of the rotor of the motor 202. HALL , and the Hall sensing signal V HALL Provided to the selection circuit 205 and the control signal generating circuit 209. The control signal generating circuit 209 is based on the Hall sensing signal V HALL A plurality of switch control signals are generated to control the output stage 201 , thereby controlling the drive current I1 flowing through the motor 202 .

[0021] The selection circuit 205 has a first input terminal, a second input terminal, a control terminal and an output terminal, wherein the first input terminal is coupled to a common node A of the first high-side switch Q1 and the first low-side switch Q2 to receive a first common node voltage V AThe second input terminal is coupled to the common node B of the second high-side switch Q3 and the second low-side switch Q4 to receive the second common node voltage V B , the control end is coupled to the Hall detection circuit 204 to receive the Hall sensing signal V HALL The selection circuit 205 is based on the Hall sensing signal V HALL , select the first common node voltage V A Or the second common node voltage V B Provided to the output terminal as the selected common node voltage.

[0022] The first comparison circuit 206 has a first input terminal, a second input terminal and an output terminal, wherein the first input terminal receives the input voltage VIN, the second input terminal is coupled to the output terminal of the selection circuit 205, and the first comparison circuit 206 compares the selected common node voltage with the input voltage VIN and provides a first comparison signal CMP1 at the output terminal.

[0023] The current polarity detection circuit 207 generates a polarity indication signal VP indicating the polarity of the driving current. The reverse current control circuit 208 receives the first comparison signal CMP1 and the polarity indication signal VP, and determines whether to control the first low-side switch Q2 or the second low-side switch Q4 to operate in a linear voltage regulation (LDO) mode based on the first comparison signal CMP1 and the polarity indication signal VP. Generally, the control signal generating circuit 209 generates a Hall sensing signal V provided by the Hall detection circuit 204. HALL , generating 4 control signals to respectively control the four switches Q1 to Q4 of the output stage circuit 201 .

[0024] When the selected common node voltage increases to the input voltage VIN and the polarity indication signal VP indicates that the polarity of the driving current I1 changes, the reverse current control circuit 208 is enabled, and the output of the reverse current control circuit 208 is coupled to the control terminal of the first low-side switch Q2 or the second low-side switch Q4 to control the first low-side switch Q2 or the second low-side switch Q4 to operate in the LDO mode. Specifically, in one embodiment, when the first common node voltage V A Selected by the selection circuit 205, the first common node voltage V A When the voltage VIN increases to the input voltage VIN and the polarity indication signal VP indicates that the driving current I1 changes from positive to negative, the first low-side switch Q2 is configured to operate in the LDO mode. B is selected, the second common node voltage V B When the voltage increases to the input voltage VIN and the polarity indication signal VP indicates that the driving current I1 changes from negative to positive, the second low-side switch Q4 is configured to operate in the LDO mode.

[0025] Figure 4 According to an embodiment of the present invention Figure 3 The working waveform of the motor drive circuit is shown in Figure 1. Figure 4 As shown, during the period from t0 to t2, the second low-side switch Q4 remains turned on, and the two switches of the first bridge arm are complementarily turned on to provide a driving current for the motor, and the driving current I1 flows from the first common node A to the second common node B.

[0026] During t0~ta, the Hall sensing signal V HALL The selection circuit 205 is based on the low-level Hall sensing signal V HALL , select the first common node voltage V A Compared with the input voltage VIN. During ta~t2, the Hall sensing signal V HALL The selection circuit 205 is based on the high-level Hall sensing signal V HALL , select the second common node voltage V B Compared with the input voltage VIN. Since the polarity indication signal VP remains unchanged, indicating that the direction of the driving current I1 has not changed, the reverse current control signal RCTRL also remains unchanged and will not control the first low-side or second low-side switch to enter the LDO mode.

[0027] At time t2, the driving current I1 starts to commutate and flows from the second common node B to the first common node A, and the polarity indication signal VP changes from a low level to a high level. HALL From low level to high level, the second common node voltage V B The selected common node voltage is compared with the input voltage VIN. Since the selected common node voltage increases to the input voltage VIN and the polarity indication signal VP indicates that the driving current I1 is commutated, the reverse current control signal RCTRL provided by the reverse current control circuit 208 becomes high. Therefore, during the period t2 to t3, the second low-side switch Q4 is configured to operate in the LDO mode, and the second common node voltage V B The driving current I1 remains unchanged and flows through the first low-side switch Q2 and the second low-side switch Q4 to avoid a voltage spike on the input capacitor CIN.

[0028] During the period t3 to t5, since the direction of the driving current I1 remains unchanged, the reverse current control circuit is disabled and the reverse current control signal RCTRL is not enabled. HALL To generate a plurality of control signals of the output stage circuit 201. Specifically, during the period t3 to t5, the second low-side switch Q2 remains turned on, and the second low-side switch Q4 and the second high-side switch Q3 are turned on complementarily.

[0029] At time t5, the driving circuit I1 changes direction, and the polarity indication signal VP changes from high level to low level. At this time, the Hall sensing signal V HALL is low level, the first common node voltage V A The selected common node voltage is compared with the input voltage VIN. According to the comparison result, during the period t5-t6, the first low-side switch Q2 is configured to operate in the LDO mode, and the first common node voltage V A The driving current I1 will remain unchanged and flow through the first low-side switch Q2 and the second low-side switch Q4 to avoid voltage spikes on the input capacitor CIN.

[0030] In summary, when the polarity indication signal VP indicates that the driving current I1 is commutating and the selected common node voltage increases to the input voltage VIN, the corresponding low-side switch is controlled to operate in the LDO mode, otherwise, the four switches of the output stage circuit 201 are controlled based on the traditional switch control signal.

[0031] Figure 5 FIG. 2 is a motor drive system 200A according to another embodiment of the present invention. Figure 3 compared to, Figure 5 The first comparison circuit 206 shown includes a comparator COM1. The comparator COM1 has a non-inverting input terminal, an inverting input terminal and an output terminal, wherein the non-inverting input terminal receives the input voltage VIN, the inverting input terminal is coupled to the output terminal of the selection circuit 205 to receive the selected common node voltage, and the comparator COM1 compares the input voltage VIN with the selected common node voltage, and provides a first comparison signal CMP1 at the output terminal. When the selected switch node voltage increases to the input voltage VIN and the drive current I1 commutates, the reverse current control circuit 208 is enabled to generate a reverse current control signal RCTRL. The reverse current control signal RCTRL configures the first low-side switch Q2 or the second low-side switch Q4 to operate in LDO mode to prevent the drive current I1 from flowing back to the input voltage terminal to reduce the voltage spike on the input capacitor CIN.

[0032] like Figure 5 As shown, the current polarity detection circuit 207A includes one or more detection resistors R SENSE , a first operational amplifier 271 and a zero-crossing detection comparison circuit 272. Figure 5 In the embodiment shown, the sense resistor R SENSE is connected in series between the low-side switch of the input stage circuit 201 and the reference ground. In other embodiments, the detection resistor R SENSE It can be connected in series between the first public node A and the second public node B.

[0033] The two input terminals of the first operational amplifier 271 are coupled to the detection resistor R SENSEThe two ends of the detection resistor R SENSE The voltages at both ends are sampled to provide a current detection signal. The zero-crossing detection comparison circuit 272 compares the current detection signal with the first reference threshold voltage Vref1 and provides a polarity indication signal VP at the output end.

[0034] Figure 6 FIG. 2 is a motor drive system 200B according to another embodiment of the present invention. Figure 6 In the embodiment shown, the current polarity detection circuit 207B detects the first common node voltage V A The polarity indication signal VP is generated according to the comparison result by comparing the second reference threshold voltage Vref2 to the input voltage VIN. In one embodiment, the second reference threshold voltage Vref2 is less than the input voltage VIN and greater than zero voltage.

[0035] like Figure 6 As shown, the current polarity detection circuit 207B includes a dead time generation circuit 274, a voltage detection circuit 275 and a second comparison circuit 276. The dead time generation circuit 274 generates a dead time control signal TD according to a plurality of switch control signals of the output stage circuit 201. The first input terminal of the voltage detection circuit 275 receives the first common node voltage V A , and its second input terminal receives the dead zone control signal TD. Based on the dead zone control signal TD, the voltage detection circuit 275 provides a voltage detection signal at the output terminal. The second comparison circuit 276 has a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to the voltage detection circuit 274 to receive the voltage detection signal, the second input terminal receives the second reference threshold voltage Vref2, and the second comparison circuit 276 compares the voltage detection signal with the second reference threshold voltage Vref2, and provides a polarity indication signal VP at the output terminal.

[0036] Figure 7 According to an embodiment of the present invention Figure 6 The working waveform of the motor drive circuit is shown in Figure 1. Figure 7 As shown, the dead time generation circuit 274 generates a high level dead time control signal TD during the periods t1 to t2, t3 to t4, and t5 to t6, respectively, and enables the voltage detection circuit 275 to detect the first common node voltage V A During the period t1 to t2, the voltage detection circuit 275 samples the first common node voltage V A is stored on the first capacitor C1. During this period, the first common node voltage V A The voltage detection circuit 275 samples the first common node voltage VA The voltage detection circuit 275 samples the first common node voltage V A When the voltage is less than zero, the second comparison circuit 276 outputs a low-level polarity indication signal VP.

[0037] Figure 8 FIG. 3 is a flow chart 300 of a control method for a motor drive circuit according to an embodiment of the present invention. Figure 8 As shown, the motor drive circuit includes an output stage circuit that provides a drive current for the motor, and the output stage circuit includes a first bridge arm and a second bridge arm coupled in parallel between an input voltage and a reference ground, wherein the first bridge arm includes a first high-side switch and a first low-side switch coupled in series, and the second bridge arm includes a second high-side switch and a second low-side switch coupled in series, and the control method includes steps 301 to 304.

[0038] In step 301 , based on the Hall sensing signal, a first common node voltage of a common node between a first high-side switch and a first low-side switch or a second common node voltage of a common node between a second high-side switch and a second low-side switch is selected as a selected common node voltage.

[0039] In step 302, the selected common node voltage is compared with the input voltage to generate a first comparison signal.

[0040] In step 303, a polarity indication signal indicating the polarity of the driving current is provided.

[0041] In one embodiment, a detection resistor is connected in series to an output stage circuit; a voltage across the detection resistor is amplified to provide a current detection signal; and the current detection signal is compared with a first reference threshold voltage to generate a polarity indication signal.

[0042] In yet another embodiment, the method for providing a polarity indication signal includes comparing the first common node voltage with a second reference threshold voltage during a dead time when both the first high-side switch and the first low-side switch are turned off, and generating a polarity indication signal according to the comparison result. In one embodiment, the second reference threshold is greater than zero voltage and less than the input voltage.

[0043] In step 304 , based on the first comparison signal and the polarity indication signal, it is determined whether to control the first low-side switch or the second low-side switch to operate in the LDO mode.

[0044] In one embodiment, when the first common node voltage is selected, the first common node voltage increases to the input voltage and the polarity indication signal indicates that the drive current changes from positive to negative, the first low-side switch is configured to operate in the LDO mode; and when the second common node voltage is selected, the second common node voltage increases to the input voltage and the polarity indication signal indicates that the drive current changes from negative to positive, the second low-side switch is configured to operate in the LDO mode.

[0045] The embodiments of the present invention are not limited to the above specific examples, and those skilled in the art should understand that a half-bridge, push-pull or other topologies with similar functions may also be used as the output stage.

[0046] The above description and implementation of the present invention only illustrate the motor drive circuit and drive method of the embodiment of the present invention in an exemplary manner, and are not intended to limit the scope of the present invention. It is possible to make changes and modifications to the disclosed embodiments, and other feasible optional embodiments and equivalent changes to the elements in the embodiments can be understood by ordinary technicians in this technical field. Other changes and modifications to the embodiments disclosed by the present invention do not exceed the spirit and protection scope of the present invention.

Claims

1. A motor drive circuit, comprising: An output stage circuit, providing a driving current for the motor, comprising a first bridge arm and a second bridge arm coupled in parallel between an input voltage and a reference ground, wherein the first bridge arm has a first high-side switch and a first low-side switch coupled in series, and the second bridge arm has a second high-side switch and a second low-side switch coupled in series; Hall detection circuit, providing Hall sensing signal; A first selection circuit has a first input terminal, a second input terminal, a control terminal and an output terminal, wherein the first input terminal is coupled to a common node of the first high-side switch and the first low-side switch to receive a first common node voltage, the second input terminal is coupled to a common node of the second high-side switch and the second low-side switch to receive a second common node voltage, the control terminal is coupled to a Hall detection circuit to receive a Hall sensing signal, and the first selection circuit selects to provide the first common node voltage or the second common node voltage as a selected common node voltage to the output terminal based on the Hall sensing signal; A current polarity detection circuit generates a polarity indication signal indicating the polarity of the driving current; A first comparison circuit has a first input terminal, a second input terminal and an output terminal, wherein the first input terminal receives an input voltage, the second input terminal is coupled to the output terminal of the first selection circuit, the first comparison circuit compares the selected common node voltage with the input voltage, and provides a first comparison signal at the output terminal; as well as The reverse current control circuit determines whether to control the first low-side switch or the second low-side switch to operate in a linear voltage regulation LDO mode based on the first comparison signal and the polarity indication signal, wherein the LDO mode controls the conduction degree of the first low-side switch or the second low-side switch to keep the selected common node voltage unchanged, and the drive current flows to the reference ground through the first low-side switch and the second low-side switch.

2. The motor drive circuit according to claim 1, wherein When the first common node voltage is selected, the first common node voltage increases to the input voltage and the polarity indication signal indicates that the driving current changes from positive to negative, the first low-side switch is configured to operate in the LDO mode; and When the second common node voltage is selected, the second common node voltage increases to the input voltage and the polarity indication signal indicates that the driving current changes from negative to positive, the second low-side switch is configured to operate in the LDO mode.

3. The motor drive circuit according to claim 1, wherein the current polarity detection circuit comprises: A detection resistor is connected in series in the output stage circuit; A first operational amplifier, having two input terminals coupled to the two ends of the detection resistor, samples the voltage across the two ends of the detection resistor, and provides a current detection signal at the output terminal; as well as The zero-crossing detection comparison circuit compares the current detection signal with the first reference threshold voltage and provides a polarity indication signal at the output terminal.

4. The motor drive circuit as described in claim 1, wherein the current polarity detection circuit compares the first common node voltage with the second reference threshold voltage during a dead time when both the first high-side switch and the first low-side switch are turned off, and generates a polarity indication signal according to the comparison result. 5 . The motor driving circuit as claimed in claim 4 , wherein the second reference threshold voltage is less than the input voltage and greater than zero voltage.

6. The motor drive circuit according to claim 4, wherein the current polarity detection circuit comprises: A dead time generation circuit generates a dead time control signal according to a plurality of switch control signals of the output stage circuit; A voltage detection circuit, wherein a first input terminal thereof receives a first common node voltage, a second input terminal thereof receives a dead zone control signal, and based on the dead zone control signal, the voltage detection circuit provides a voltage detection signal at an output terminal; as well as The second comparison circuit has a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to the voltage detection circuit to receive a voltage detection signal, the second input terminal receives a second reference threshold voltage, and the second comparison circuit compares the voltage detection signal with the second reference threshold voltage and provides a polarity indication signal at the output terminal.

7. The motor drive circuit according to claim 6, wherein the voltage detection circuit comprises: A sampling switch having a first terminal, a second terminal and a control terminal, wherein the first terminal is coupled to a common node of the first high-side switch and the first low-side switch to receive a first common node voltage, and the control terminal receives a dead zone control signal; as well as The first capacitor has a first terminal and a second terminal, wherein the first terminal is coupled to the second terminal of the sampling switch and the first input terminal of the second comparison circuit, and the second terminal is coupled to the reference ground.

8. The motor driving circuit as claimed in claim 1, wherein the output stage circuit further comprises a third bridge arm, which is coupled in parallel with the first bridge arm and the second bridge arm to provide driving current for the three-phase motor.

9. A control method for a motor drive circuit, the motor drive circuit comprising an output stage circuit providing a drive current for a motor, the output stage circuit comprising a first bridge arm and a second bridge arm coupled in parallel between an input voltage and a reference ground, wherein the first bridge arm comprises a first high-side switch and a first low-side switch coupled in series, and the second bridge arm comprises a second high-side switch and a second low-side switch coupled in series, the control method comprising: Based on the Hall sensing signal, selecting a first common node voltage of a common node between the first high-side switch and the first low-side switch or a second common node voltage of a common node between the second high-side switch and the second low-side switch as a selected common node voltage; Comparing the selected common node voltage with the input voltage to generate a first comparison signal; Providing a polarity indication signal indicating the polarity of the driving current; as well as Based on the first comparison signal and the polarity indication signal, it is determined whether to control the first low-side switch or the second low-side switch to operate in the LDO mode, wherein the LDO mode controls the conduction degree of the first low-side switch or the second low-side switch to keep the selected common node voltage unchanged, and the drive current flows to the reference ground through the first low-side switch and the second low-side switch.

10. The control method according to claim 9, wherein: When the first common node voltage is selected, the first common node voltage increases to the input voltage and the polarity indication signal indicates that the driving current changes from positive to negative, the first low-side switch is configured to operate in the LDO mode; as well as When the second common node voltage is selected, the second common node voltage increases to the input voltage and the polarity indication signal indicates that the driving current changes from negative to positive, the second low-side switch is configured to operate in the LDO mode.

11. The control method as claimed in claim 9, wherein the method of providing the polarity indication signal comprises: Connect the detection resistor in series with the output stage circuit; sampling the voltage across the sensing resistor to provide a current sensing signal; as well as The current detection signal is compared with a first reference threshold voltage to generate a polarity indication signal.

12. The control method as claimed in claim 9, wherein the method of providing the polarity indication signal comprises: During the dead time when both the first high-side switch and the first low-side switch are turned off, the first common node voltage is compared with the second reference threshold voltage, and a polarity indication signal is generated according to the comparison result. 13 . The control method as claimed in claim 12 , wherein the second reference threshold voltage is greater than zero voltage and less than an input voltage.

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