Initial position detection and over-current detection multiplexing direct current brushless motor driving chip and control system

Abstract

The invention relates to the technical field of electronic circuits, in particular to an initial position detection and over-current detection multiplexing direct-current brushless motor driving chip and a control system. By arranging a multiplexing detection circuit, a digital core controls the multiplexing detection circuit to be used for initial position detection or over-current detection in different states through multiplexing control signals during use, specifically, the initial position detection function and a current sampling module for over-current detection are multiplexed, the repeatability of design of an analog circuit in a chip is reduced, and the reliability of the chip is improved. And meanwhile, the nonvolatile memory has an amplitude gear of an initial position detection reference current and an amplitude gear of an overcurrent detection reference current of the motor under different rated voltages, so that the chip can be suitable for initial position detection and overcurrent detection of different motors.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to a DC brushless motor drive chip and a control system for multiplexing initial position detection and overcurrent detection. Background Art

[0002] The detection of the initial position of the rotor (IPD) plays a key role in the startup of the three-phase DC brushless motor. At present, most DC brushless motor driver chips adopt two startup schemes. The first is to inject a current of a specified amplitude and direction into the motor, forcibly drag the motor rotor to a certain angle, and then the system enters the open-loop acceleration phase to increase the motor speed until a detectable back electromotive force is generated, and then the closed-loop drive motor is switched on. The second is to directly determine the rotor position by using a built-in or external Hall sensor on the chip. The disadvantage of the first method is that it cannot avoid the possible reversal when the motor starts; and the forced drag process takes a long time for a DC brushless motor with large inertia. The disadvantage of the second method is that the built-in Hall sensor on the chip increases the circuit area, and the external Hall sensor will increase the application cost.

[0003] Based on the above defects, this patent introduces a developed brushless DC motor driver chip that can reuse the initial position detection function and the current sampling module for overcurrent detection. Its most significant advantage is that it improves the motor starting performance, reduces the repeatability of the analog circuit design inside the chip, and improves the chip's integration. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a brushless DC motor drive chip and control system that reuses initial position detection and overcurrent detection, which reuses the initial position detection function and the current sampling module of overcurrent detection, reducing the repeatability of the analog circuit design inside the chip and making the chip more integrated.

[0005] The present invention discloses a DC brushless motor driver chip for multiplexing initial position detection and overcurrent detection through an embodiment, including a digital core, a non-volatile memory and a driver module, wherein the digital core sets a plurality of IPD drive states and corresponding freewheeling states, and the non-volatile memory stores a duration parameter and a freewheeling mode parameter of each freewheeling state; and further includes: a current sampling circuit and a multiplexing detection circuit;

[0006] The motor drive signal output terminal of the digital core is connected to the input terminal of the drive module, and is used to output the motor drive control signal to the drive module according to the set IPD drive states;

[0007] The multiplexing signal control output terminal of the digital core is connected to the multiplexing signal control input terminal of the multiplexing detection circuit, and is used to output the multiplexing control signal to the multiplexing detection circuit;

[0008] The output end of the driving module serves as the output end of the brushless DC motor driving chip;

[0009] The current sampling circuit is used to collect the output current of the driving module, and transmit the output current to the multiplexing detection circuit with or without scaling;

[0010] The multiplexing detection circuit is used to output an initial position indication signal to the digital core according to the multiplexing control signal, and the digital core calculates the initial position of the motor; or output an overcurrent detection result signal to the digital core, and the digital core determines whether to continue to output or disconnect the motor drive control signal according to the overcurrent detection result signal.

[0011] Further, the digital core includes: a motor starting logic controller, a timer, and a circuit breaker;

[0012] After receiving the speed command or forward and reverse rotation command of the motor, the motor start logic controller outputs the motor drive control signal to the drive module and outputs the multiplexing control signal to the multiplexing detection circuit;

[0013] The timer is used to count the duration of the initial position indication signal under each IPD driving state, and return the duration under each IPD driving state to the motor start logic controller, and the motor logic controller determines the initial position according to the driving state with the shortest duration under each IPD driving state;

[0014] The circuit breaker is used to determine whether to disconnect the motor drive control signal according to the overcurrent detection result signal.

[0015] Furthermore, the digital core also includes a filter, which is used to filter out burrs in the overcurrent detection result signal and then transmit the overcurrent detection result signal to the circuit breaker.

[0016] Furthermore, the non-volatile memory is also used to store the amplitude level of the initial position detection reference current, the amplitude level of the overcurrent detection reference current, and information on whether to restart after overcurrent triggering; and output the amplitude level of the initial position detection reference current and the amplitude level of the overcurrent detection reference current to the multiplexing detection circuit.

[0017] Further, the multiplexing detection circuit includes: a multiplexer, a current comparator and a demultiplexer;

[0018] The multiplexer is used for receiving the initial position detection reference current and the overcurrent detection reference current output by the non-volatile memory, and selecting to output the initial position detection reference current or the overcurrent detection reference current to the first input terminal of the current comparator according to the received multiplexing control signal;

[0019] The output current signal of the driving module collected by the current sampling circuit is input to the second input terminal of the current comparator;

[0020] The output end of the current comparator is connected to the input end of the demultiplexer, and is used to output the current comparison result signal to the demultiplexer;

[0021] The demultiplexer selects to output an initial position indication signal or an overcurrent detection result signal to the digital core according to the received multiplexing control signal and the current comparison result signal.

[0022] Further, the driving module includes a pre-driving circuit and an inverter circuit;

[0023] The digital core outputs the motor drive control signal under each IPD drive state to the pre-drive circuit, and the pre-drive circuit converts the motor drive control signal and outputs it to the inverter circuit. The output end of the inverter circuit serves as the output end of the brushless DC motor drive chip.

[0024] Furthermore, the inverter circuit includes a three-phase bridge inverter, and the output end of the three-phase bridge inverter serves as the output end of the brushless DC motor drive chip.

[0025] The current sampling circuit collects the sum of the currents of the bridge arms of the three-phase bridge inverter as the output current, and transmits the output current to the multiplexing detection circuit with or without scaling.

[0026] Furthermore, the non-volatile memory is also used to store information on whether to restart after an overcurrent trigger.

[0027] In order to achieve the above-mentioned purpose, the present invention also provides a DC brushless motor control system for multiplexing initial position detection and overcurrent detection, including the above-mentioned DC brushless motor drive chip for multiplexing initial position detection and overcurrent detection, and also including a three-phase brushless motor; wherein the output of the three-phase bridge inverter is connected to the three-phase brushless motor, and the digital core is also connected to the speed control command signal and forward and reverse command signal of the three-phase brushless motor.

[0028] The technical principle of the present invention is: according to the principle that the equivalent inductance of the motor stator coil is related to the rotor position, the voltage pulses with the same voltage value and different voltage directions are judged, and the current change rate is different to identify the initial position of the rotor; when the stator current exists, when the current direction is consistent with the direction of the N pole of the rotor magnetic pole, the phase inductance is minimum. According to u=Ldi / dt, when the voltages at both ends of the inductor coil are the same, the smaller the inductance, the greater the slope of the current rise. The driver chip is started under different driving states, and when the driving current of the motor reaches the set IPD threshold from 0, there will be a duration. The duration of the motor traversing each driving state is obtained, and then the approximate position of the motor rotor can be obtained according to the shortest duration, and then the initial angle of the rotor can be calculated according to the driving state with the shortest timing. Among them, when the motor starts, the position detection function takes effect: the multiplexing detection circuit outputs the initial position detection reference current according to the multiplexing control signal, and the current sampling circuit collects the current change when the motor's driving current reaches the set IPD threshold (i.e., the initial position detection reference current) from 0, and compares it through the current comparator. Once the driving current reaches the threshold, the output of the current comparator flips, and the timer records this time. Finally, the initial angle of the rotor is calculated according to the shortest time of a certain driving state; after the position detection is completed, the overcurrent detection function begins to take effect: the multiplexing detection circuit outputs the overcurrent detection reference current according to the multiplexing control signal, and the current sampling circuit collects the motor's driving current, and compares it through the current comparator. Once the driving current reaches the overcurrent detection reference current threshold, the output flips, and transmits a signal to the circuit breaker to make the inverter output voltage 0, forcing the motor to stop rotating to protect the drive chip or the motor.

[0029] Compared with the prior art, the present invention has the following beneficial effects: the initial position detection function is multiplexed with the current sampling circuit and current comparator for overcurrent detection, thereby reducing the repeatability of the analog circuit design inside the chip and making the chip more integrated. At the same time, the non-volatile memory has amplitude levels of the reference current for initial position detection of the motor under different rated voltages and amplitude levels of the reference current for overcurrent detection. Different levels can be set according to needs to adapt to different application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the present invention and facilitate further understanding of the technical effects, technical features and purposes of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings. The accompanying drawings constitute an essential part of the specification and are used together with the embodiments of the present invention to illustrate the technical solution of the present invention, but do not constitute a limitation to the present invention.

[0031] Figure 1 The internal schematic diagram of the chip described in the present invention;

[0032] Figure 2 The IPD control process described in the embodiment of the present invention;

[0033] Figure 3 The current flow direction of the driving circuit in the freewheeling mode according to the embodiment of the present invention;

[0034] Figure 4 The internal module diagram of the chip described in the present invention;

[0035] Figure 5 This is a schematic diagram of the control system described in the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. Of course, the specific embodiments described below are only intended to explain the technical solutions of the present invention, rather than to limit the present invention. In addition, the parts described in the embodiments or the accompanying drawings are only examples of the relevant parts of the present invention, rather than the entirety of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art should naturally belong to the protection scope of the present invention.

[0037] like Figure 1-4 As shown, the present invention proposes a DC brushless motor driver chip 101 for multiplexing initial position detection and overcurrent detection through the following embodiments, including a digital core 203, a non-volatile memory 202 and a driver module 2, the digital core 203 sets multiple IPD drive states and corresponding freewheeling states, the non-volatile memory 202 stores the duration parameter and freewheeling mode parameter of each freewheeling state, and is also used to store the amplitude level of the initial position detection reference current, the amplitude level of the overcurrent detection reference current, and the information of whether to restart after the overcurrent trigger, and store the information of whether to restart after the overcurrent trigger; and output the amplitude level of the initial position detection reference current and the amplitude level of the overcurrent detection reference current to the multiplexing detection circuit; and also include: a current sampling circuit 206 and a multiplexing detection circuit 3;

[0038] The motor drive signal output terminal of the digital core 203 is connected to the input terminal of the drive module 2, and is used to output the motor drive control signal to the drive module 2 according to the set IPD drive states;

[0039] The multiplexing signal control output terminal of the digital core 203 is connected to the multiplexing signal control input terminal of the multiplexing detection circuit, and is used to output the multiplexing control signal to the multiplexing detection circuit 3;

[0040] The output end of the driving module 2 serves as the output end of the brushless DC motor driving chip 101;

[0041] The current sampling circuit 205 is used to collect the output current of the driving module 2, and transmit the output current to the multiplexing detection circuit 3 with or without scaling;

[0042] The multiplexing detection circuit 3 is used to output an initial position indication signal to the digital core 203 according to the multiplexing control signal, and the digital core 203 calculates the initial position of the motor; or output an overcurrent detection result signal to the digital core 203, and the digital core 203 determines whether to continue to output or disconnect the motor drive control signal according to the overcurrent detection result signal.

[0043] In this embodiment, the digital core 203 includes: a motor start logic controller, a timer and a circuit breaker. Among them, during the initial position detection period, the motor start logic controller outputs a specified six-way drive signal sequence according to the received forward and reverse command signal to provide IPD control logic for motor start; during normal drive, it provides algorithm support for motor speed regulation; monitors the motor operation status, outputs signal multiplexing control signals, and six-way drive signals. Specifically, the six-way drive signal is divided into 12 IPD states, of which the 1st, 3rd, 5th, 7th, 9th, and 11th states are drive states, and the 2nd, 4th, 6th, 8th, 10th, and 12th states are freewheeling states. The time for which the IPD freewheeling state is maintained is the time t1 set in the non-volatile memory 202. In the IPD drive state: voltage is applied to any two phases of the three-phase winding, and the third phase is in a high impedance state, for a total of six combinations. For example, the power tubes are turned on in this order: driving state 1 is to turn on the high side of V phase and the low side of W phase, driving state 3 is to turn on the high side of W phase and the low side of V phase, driving state 5 is to turn on the high side of U phase and the low side of V phase, driving state 7 is to turn on the high side of V phase and the low side of U phase, driving state 9 is to turn on the high side of W phase and the low side of U phase, and driving state 11 is to turn on the high side of U phase and the low side of W phase.

[0044] The timer is used to count the duration of the initial position indication signal under each IPD driving state, and return the duration of each IPD driving state to the motor starting logic controller, and the motor logic controller determines the initial position according to the driving state with the shortest duration among the IPD driving states.

[0045] The circuit breaker is used to determine whether to disconnect the motor drive control signal according to the overcurrent detection result signal.

[0046] In this embodiment, the digital core 203 further includes a filter, which is used to filter out the burrs in the overcurrent detection result signal and transmit the overcurrent detection result signal to the circuit breaker. The filter can prevent the signal burrs caused by electromagnetic interference from causing the level of the overcurrent detection result signal to change, thereby triggering the switch tube to shut down, ensuring that the system has higher reliability.

[0047] In this embodiment, the multiplexing detection circuit 3 includes: a multiplexer 208, a current comparator 207 and a demultiplexer 209;

[0048] The multiplexer 208 is used to receive the initial position detection reference current IrefIPD and the overcurrent detection reference current IrefOCP output by the non-volatile memory, and select to output the initial position detection reference current or the overcurrent detection reference current to the first input terminal of the current comparator 207 according to the received multiplexing control signal Sel2;

[0049] The output current signal of the driving module collected by the current sampling circuit 206 is input to the second input terminal of the current comparator 207;

[0050] The output end of the current comparator 207 is connected to the input end of the demultiplexer 208, and is used to output the current comparison result signal Flag to the demultiplexer 209;

[0051] The demultiplexer 209 selects to output the initial position indication signal or the overcurrent detection result signal to the digital core 203 according to the received multiplexing control signal and the current comparison result signal.

[0052] In this embodiment, the drive module 2 includes a pre-drive circuit 204 and an inverter circuit 205. Among them, the digital core outputs the motor drive control signal in each IPD driving state to the pre-drive circuit 204, and the pre-drive circuit 204 converts the motor drive control signal to the inverter circuit after level conversion, and the output end of the inverter circuit 205 is used as the output end of the DC brushless motor drive chip. The pre-drive circuit 204 converts the six-way drive signal output by the digital core to turn on or off the field effect transistor in the inverter circuit. The inverter circuit 205 is a three-phase bridge inverter, which is composed of six field effect transistors. The switch tubes in the three-phase bridge inverter are connected in series in pairs, receive the six-way signal from the pre-drive circuit 204, and under the control of the speed control algorithm in the digital core, appropriately turn on or off the field effect tube so that the output three-phase voltage can directly drive the three-phase brushless DC motor.

[0053] When used for IPD detection, such as Figure 2 As shown, according to the preset driving sequence in the digital core 203, voltage pulses are applied to the motor at fixed time intervals. At this time, the multiplexer 208 selects to output the initial position detection reference current to provide a reference current for the current comparator. A timer is set in the digital core, and timer1 starts timing from 0 in each driving state. When the Flag signal output by the current comparator 207 flips, the timer timer1 stops timing. The values ​​of timer1 timing are compared in sequence. When six driving states are completed, the current direction of the driving state with the shortest timer timing corresponds to the approximate position of the rotor. The digital core contains a lookup table, and the initial angle of the rotor can be found correspondingly according to the driving state with the shortest timing.

[0054] It is worth noting that after a driving state ends, a continuous flow state must follow. The continuous flow state can be selected as a high-impedance mode or a circulation mode, which is configured by the non-volatile memory 202. The current flow direction of the two modes is referenced Figure 4 .

[0055] Taking the current direction in the driving state as U phase flowing into the motor and V phase flowing out of the motor as an example, that is, in the driving state, the three-phase bridge inverter 205 turns on the upper bridge arm MOS of the U phase bridge arm and the lower bridge arm MOS of the V phase bridge arm.

[0056] If the freewheeling mode is configured as the circulation mode, the corresponding freewheeling state is: turn off the upper bridge arm MOS of the U phase, keep the lower bridge arm MOS of the V phase turned on, so that the freewheeling direction of the current is: the V phase stator winding of the motor → the V phase lower bridge arm MOS tube of the three-phase bridge inverter → the ground wire → the body diode of the U phase lower bridge arm of the three-phase bridge inverter → the U phase stator winding of the motor.

[0057] If the freewheeling mode is configured as the high-impedance mode, the corresponding freewheeling state is: turn off the upper bridge arm MOS of the U phase and the lower bridge arm MOS of the V phase, so that the freewheeling direction of the current is: ground → body diode of the lower bridge arm of the U phase of the three-phase bridge inverter → stator winding of the U phase of the motor → stator winding of the V phase of the motor → body diode of the upper bridge arm of the V phase of the three-phase bridge inverter → power supply.

[0058] When the freewheeling mode is the high-impedance mode, the bus current decays to 0 faster, but the disadvantage is that it will cause voltage surges on the power supply, which can be improved by connecting a suitable capacitor between the power supply and the ground line. However, when the power surge is unacceptable, the value representing the freewheeling time t1 stored in the non-volatile memory 202 can be reasonably set to ensure that the current in the motor winding has sufficient time to be discharged to 0 before the next driving state comes.

[0059] At the end of the IPD phase, Figure 4As shown, the control state inside the digital core 203 jumps to the normal driving state. The initial position detection reference current or the overcurrent detection reference current changes with the control state, so that the multiplexer 208 selects the overcurrent detection reference current, and the current comparator compares the driving current Isample with the overcurrent detection reference current IrefOCP; when Isample>IrefOCP, the current comparison result signal OCPFlag received by the digital core 203 changes in level (OCPFlag changes from low level to high level as shown in the figure), indicating that the bus current is too high at this time and exceeds the set safety threshold. The digital core 203 receives the current comparison result signal, and performs a logical operation on the six MOS drive signals generated by the speed control algorithm and the current comparison result signal OCPFlag (as shown in the figure, the OCPFlag signal is inverted and then ANDed with the six MOS drive signals respectively), so as to directly shut down each switch tube in the inverter to avoid motor loss of control or circuit burning.

[0060] On the other hand, in order to achieve the above purpose, Figure 5 As shown, the present invention also provides a DC brushless motor control system 100 for multiplexing initial position detection and overcurrent detection, including the above-mentioned DC brushless motor drive chip 101 for multiplexing initial position detection and overcurrent detection, and also including a three-phase brushless motor 102; wherein, the output of the three-phase bridge inverter is connected to the three-phase brushless motor, and the digital core is also connected to the speed control command signal 103 and the forward and reverse rotation command signal 104 of the three-phase brushless motor.

[0061] It should be noted that the above embodiments are only for more clearly illustrating the technical solutions of the present invention. Those skilled in the art will understand that the implementation methods of the present invention are not limited to the above contents, and obvious changes, replacements or substitutions based on the above contents do not exceed the scope of the technical solutions of the present invention; other implementation methods will naturally fall within the scope of the present invention without departing from the concept of the present invention.

Claims

1. A brushless DC motor driver chip for multiplexing initial position detection and overcurrent detection, comprising a digital core, a non-volatile memory and a driver module, wherein the digital core sets a plurality of IPD drive states and corresponding freewheeling states, and the non-volatile memory stores a duration parameter and a freewheeling mode parameter of each freewheeling state, characterized in that: Also includes: Current sampling circuit and multiplexing detection circuit; The motor drive signal output terminal of the digital core is connected to the input terminal of the drive module, and is used to output the motor drive control signal to the drive module according to the set IPD drive states; The multiplexing signal control output terminal of the digital core is connected to the multiplexing signal control input terminal of the multiplexing detection circuit, and is used to output the multiplexing control signal to the multiplexing detection circuit; The output end of the driving module serves as the output end of the brushless DC motor driving chip; The current sampling circuit is used to collect the output current of the driving module, and transmit the output current to the multiplexing detection circuit with or without scaling; The multiplexing detection circuit is used to output an initial position indication signal to the digital core according to the multiplexing control signal, and the digital core calculates the initial position of the motor; or output an overcurrent detection result signal to the digital core, and the digital core determines whether to continue to output or disconnect the motor drive control signal according to the overcurrent detection result signal.

2. The DC brushless motor driver chip for multiplexing initial position detection and overcurrent detection as claimed in claim 1, characterized in that: The digital core includes: a motor starting logic controller, a timer and a circuit breaker; After receiving the speed instruction or the forward and reverse rotation instruction of the motor, the motor start logic controller outputs the motor drive control signal to the drive module and outputs the multiplexing control signal to the multiplexing detection circuit; The timer is used to count the duration of the initial position indication signal under each IPD driving state, and return the duration under each IPD driving state to the motor start logic controller, and the motor logic controller determines the initial position according to the driving state with the shortest duration under each IPD driving state; The circuit breaker is used to determine whether to disconnect the motor drive control signal according to the overcurrent detection result signal.

3. The DC brushless motor driver chip for multiplexing initial position detection and overcurrent detection as claimed in claim 2, characterized in that: The digital core further includes a filter, which is used to filter out burrs in the overcurrent detection result signal and then transmit the overcurrent detection result signal to the circuit breaker.

4. The DC brushless motor driver chip for multiplexing initial position detection and overcurrent detection as claimed in claim 2, characterized in that: The non-volatile memory is also used to store the amplitude level of the initial position detection reference current and the amplitude level of the overcurrent detection reference current of the motor under different rated voltages, as well as information on whether to restart after overcurrent triggering; and output the amplitude level of the initial position detection reference current and the amplitude level of the overcurrent detection reference current to the multiplexing detection circuit.

5. The DC brushless motor driver chip for multiplexing initial position detection and overcurrent detection as claimed in claim 4, characterized in that: The multiplexing detection circuit comprises: a multiplexer, a current comparator and a demultiplexer; The multiplexer is used to receive the initial position detection reference current and the overcurrent detection reference current output by the non-volatile memory, and select to output the initial position detection reference current or the overcurrent detection reference current to the first input terminal of the current comparator according to the received multiplexing control signal; The output current signal of the driving module collected by the current sampling circuit is input to the second input terminal of the current comparator; The output end of the current comparator is connected to the input end of the demultiplexer, and is used to output a current comparison result signal to the demultiplexer; The demultiplexer selects to output an initial position indication signal or an overcurrent detection result signal to the digital core according to the received multiplexing control signal and the current comparison result signal.

6. The DC brushless motor driver chip for multiplexing initial position detection and overcurrent detection as claimed in claim 5, characterized in that: The driving module includes a pre-driving circuit and an inverter circuit; The digital core outputs the motor drive control signal under each IPD drive state to the pre-drive circuit, and the pre-drive circuit performs level conversion on the motor drive control signal and outputs it to the inverter circuit. The output end of the inverter circuit serves as the output end of the brushless DC motor drive chip.

7. The DC brushless motor driver chip for multiplexing initial position detection and overcurrent detection as claimed in claim 6, characterized in that: The inverter circuit includes a three-phase bridge inverter, and the output end of the three-phase bridge inverter serves as the output end of the brushless DC motor drive chip; The current sampling circuit collects the sum of the currents of the bridge arms of the three-phase bridge inverter as the output current, and transmits the output current to the multiplexing detection circuit with or without scaling.

8. The DC brushless motor driver chip for multiplexing initial position detection and overcurrent detection as claimed in claim 1, characterized in that: The non-volatile memory is also used to store information on whether to restart after an overcurrent trigger.

9. A brushless DC motor control system with multiplexing of initial position detection and overcurrent detection, characterized in that: It includes the DC brushless motor drive chip for multiplexing initial position detection and overcurrent detection as described in claim 7, and also includes a three-phase brushless motor; the output of the three-phase bridge inverter is connected to the three-phase brushless motor, and the digital core is also connected to a speed control command signal and a forward and reverse command signal.

Images