Active brake circuit of three-phase motor

Abstract

An active brake circuit of a three-phase motor comprises a rotating speed detection circuit, an energy consumption circuit and a controller. The rotating speed detection circuit comprises an overvoltage detection element and a level signal generation circuit; the first end of the overvoltage detection element is connected with any phase of the three-phase motor, the second end of the overvoltage detection element is connected with the input end of the level signal generation circuit, and the output end of the level signal generation circuit is connected with the input end of the controller. The energy consumption circuit is connected between any phase of the three-phase motor and the ground, and comprises an energy consumption element used for consuming electric energy and a control switch used for controlling whether the energy consumption element works or not. The output end of the controller is connected with the controlled end of the control switch. According to the utility model, when the rotating speed of the three-phase motor is too fast, the rotating speed of the three-phase motor can be rapidly reduced, so that the three-phase motor is protected.

Description

Technical Field

[0001] The utility model relates to a control circuit technology for a three-phase motor. Background Art

[0002] In order to prevent the charging cover of new energy vehicles from being damaged by the high speed of the charging cover drive motor due to excessive external thrust, a common solution is to increase the mechanical holding force of the charging cover drive motor and control the electronic holding force of the charging cover drive motor through electronic control.

[0003] Increasing the mechanical holding force of the charging cover's drive motor requires increasing the motor's gear ratio, which reduces the motor's transmission efficiency, violates energy conservation requirements, and increases costs. Increasing the electronic holding force of the charging cover's drive motor through electronic control consumes more operating current, reducing the range of new energy vehicles. Conventional motor active braking circuits, however, experience excessive back EMF voltage due to excessive motor speed, causing the system to enter overvoltage protection and thus lose control of the active braking circuit. Summary of the Invention

[0004] The technical problem to be solved by the utility model is to provide a three-phase motor active braking circuit, which can quickly reduce the speed of the three-phase motor when the speed of the three-phase motor is too fast, and has a simple circuit structure and low energy consumption.

[0005] An embodiment of the utility model discloses an active braking circuit for a three-phase motor, comprising a speed detection circuit, an energy consumption circuit, and a controller. The speed detection circuit comprises an overvoltage detection element and a level signal generating circuit. A first end of the overvoltage detection element is connected to any phase of the three-phase motor, a second end of the overvoltage detection element is connected to an input end of the level signal generating circuit, and an output end of the level signal generating circuit is connected to an input end of the controller. The overvoltage detection element is configured to control the level signal generating circuit to output a first level signal to the controller when the back electromotive force voltage of any phase of the three-phase motor is lower than a preset voltage, and to control the level signal generating circuit to output a second level signal to the controller when the back electromotive force voltage of any phase of the three-phase motor is equal to or higher than the preset voltage. The energy consumption circuit is connected between any phase of the three-phase motor and ground, and comprises an energy consumption element for consuming electrical energy and a control switch for controlling whether the energy consumption element operates. The output end of the controller is connected to a controlled end of the control switch. The controller is configured to control the control switch to be turned off upon receiving the first level signal, thereby disabling the energy consumption element, and to control the control switch to be turned on upon receiving the second level signal, thereby enabling the energy consumption element to consume electrical energy.

[0006] Preferably, the controller uses an MCU of model TLE9879 manufactured by Infineon Technologies, the MON interface of the MCU constitutes the input end of the controller, and the IO interface of the MCU constitutes the output end of the controller.

[0007] The utility model has at least the following technical effects:

[0008] 1. The embodiment of the present invention can detect the situation where the speed of the three-phase motor is too high through a simple hardware circuit, and control the energy consumption circuit through the controller to consume the energy caused by the excessive speed, thereby limiting the excessive speed of the three-phase motor and avoiding damage to the motor components caused by the excessive speed;

[0009] 2. The controller of the embodiment of the present invention adopts the MCU model TLE9879 manufactured by Infineon. Due to the special function of the MON interface of this MCU chip, the three-phase motor active braking circuit of this embodiment can work normally even if the system is in sleep mode. Therefore, the three-phase motor will not be damaged due to excessive speed under any working conditions, and better energy-saving effect can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The schematic diagram of the three-phase motor active braking circuit according to the embodiment of the present invention is shown.

[0011] Figure 2 The figure shows a circuit principle diagram of a three-phase motor active braking circuit according to an embodiment of the present utility model. DETAILED DESCRIPTION

[0012] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0013] Please refer to Figure 1 and Figure 2 According to an embodiment of the present invention, a three-phase motor active braking circuit includes a speed detection circuit 1 , an energy consumption circuit 2 , and a controller 3 .

[0014] The speed detection circuit 1 includes an overvoltage detection element 11 and a level signal generating circuit 12. A first end of the overvoltage detection element 11 is connected to any phase of the three-phase motor 4, a second end of the overvoltage detection element 11 is connected to an input of the level signal generating circuit 12, and an output of the level signal generating circuit 12 is connected to an input of the controller 3. The overvoltage detection element 11 is configured to control the level signal generating circuit 12 to output a first level signal to the controller 3 when the back electromotive force voltage of any phase of the three-phase motor 4 is lower than a preset voltage, and to control the level signal generating circuit 12 to output a second level signal to the controller 3 when the back electromotive force voltage of any phase of the three-phase motor 4 is equal to or higher than the preset voltage.

[0015] In this embodiment, the overvoltage detection element 11 is formed by a voltage regulator tube Z1, and the cathode and anode of the voltage regulator tube Z1 respectively constitute the first terminal and the second terminal of the overvoltage detection element 11. The aforementioned preset voltage is the breakdown voltage of the voltage regulator tube.

[0016] In this embodiment, the level signal generating circuit 12 includes a switching element Q1, a switching element Q2, a resistor R1, and a resistor R2. The first end of resistor R1 and the first conductive end of switching element Q2 are respectively connected to a power supply VDD. The common point between the second end of resistor R1 and the first conductive end of switching element Q1 is connected to the controlled end of switching element Q2. The second conductive end of switching element Q2 is connected to the first end of resistor R2. The second end of resistor R2 and the second conductive end of switching element Q1 are both grounded. The controlled end of switching element Q1 constitutes the input end of the level signal generating circuit 12, and the common point between the second conductive end of switching element Q2 and the first end of resistor R2 constitutes the output end of the level signal generating circuit 12. The first level signal is a low level signal, and the second level signal is a high level signal.

[0017] exist Figure 2 In the illustrated embodiment, the switching element Q1 is an NPN transistor, whose base, collector, and emitter respectively constitute the controlled terminal, first conducting terminal, and second conducting terminal of the switching element Q1. The switching element Q2 is a PNP transistor, whose base, emitter, and collector respectively constitute the controlled terminal, first conducting terminal, and second conducting terminal of the switching element Q2.

[0018] The energy consumption circuit 2 is connected between any phase of the three-phase motor 4 and the ground. The energy consumption circuit 2 includes an energy consumption element 21 for consuming electric energy and a control switch 22 for controlling whether the energy consumption element 21 is working.

[0019] In this embodiment, the energy dissipation element 21 includes a resistor R3. A first end of the resistor R3 is connected to any phase of the three-phase motor 4. A second end of the resistor R3 is connected to a first conductive end of the control switch 22. The second conductive end of the control switch 22 is grounded. Optionally, the control switch 22 is formed by an NMOS transistor Q3. The gate, drain, and source of the NMOS transistor Q3 respectively constitute the controlled end, first conductive end, and second conductive end of the control switch 22.

[0020] exist Figure 1 In the illustrated embodiment, the first end of the overvoltage detection element 11 is connected to the U phase of the three-phase motor 4, and the energy consumption circuit 2 is connected between the V phase of the three-phase motor 4 and ground. This is merely an example. In other embodiments, for example, the first end of the overvoltage detection element 11 and the energy consumption circuit 2 may both be connected to the U phase of the three-phase motor 4.

[0021] The output end of the controller 3 is connected to the controlled end of the control switch 22. The controller 3 is used to control the control switch 22 to turn off when receiving a first level signal so that the energy-consuming element 21 does not work, and to control the control switch 22 to turn on when receiving a second level signal so that the energy-consuming element consumes electrical energy.

[0022] In this embodiment, controller 3 includes an MCU. Controller 3 employs an Infineon Technologies MCU, model TLE9879. The MCU's MON interface constitutes the input of controller 3, while the MCU's IO interface constitutes the output of controller 3. The MON interface is a special IO port of the TLE9879 MCU chip U1. When the entire system is dormant, an external high level input to the MON interface can trigger the system to wake up and operate normally, thereby controlling the operation of energy-consuming circuit 2.

[0023] In this embodiment, the control output of the controller 3 is connected to the input of a three-phase motor drive circuit 5 (for example, a three-phase full-bridge drive circuit), and the output of the three-phase motor drive circuit 5 is connected to a three-phase motor 4. The three-phase motor 4 is a brushless DC motor (i.e., a BLDC motor).

[0024] In a specific application, the three-phase motor active braking circuit of this embodiment is applied to the motor control circuit of a smart charging cover for a car, where the three-phase motor 4 is the driving motor of the charging cover. The motor speed is detected by hardware, triggering the MCU to drive the energy consumption circuit 2 to operate, thereby achieving the purpose of limiting the three-phase motor speed. The back electromotive force voltage of any phase of the three-phase motor 4 is directly proportional to the speed of the three-phase motor 4. When the system is operating normally and the three-phase motor speed is not high, the back electromotive force voltage is not high, and the output signal of the speed detection circuit 1 does not trigger the energy consumption circuit 2 to operate. When the charging cover is pushed by an external force, the speed will increase, and the back electromotive force voltage will also increase. When the speed detection circuit 1 detects that the speed reaches the protection threshold (i.e., the back electromotive force voltage of any phase of the three-phase motor is equal to or greater than the preset voltage), it will output a high-level signal to the MCU. After the MCU detects this high level, it outputs a signal through the IO interface to turn on the control switch 22, and the energy consumption element 21 consumes the input power of the three-phase motor 4, thereby controlling the speed of the three-phase motor 4 below the protection threshold.

[0025] The following combination Figure 1 and Figure 2 The working process of the three-phase motor active braking circuit according to one embodiment of the present invention is described in detail.

[0026] During normal operation, since the speed of three-phase motor 4 is low, the back EMF voltage of phase U of three-phase motor 4 is low, preventing voltage regulator diode Z1 from breaking down. NPN transistor Q1 is unable to conduct and is in the off state. The base and emitter of PNP transistor Q2 are both high, consistent with the voltage of power supply VDD, thus also turning off PNP transistor Q2. Resistor R2 is connected between the collector of PNP transistor Q2 and ground. Since PNP transistor Q2 is in the off state, the collector voltage of PNP transistor Q2 is 0V. The MON interface of MCU chip U1, manufactured by Infineon Technologies, model TLE9879, is a special high-level detection port. If the voltage level of this interface does not exceed 0.3VDD, the MCU will not enter interrupt control protection, and the MCU's IO interface output is low, thus turning off NMOS transistor Q3. This disables energy consumption circuit 2 and does not affect normal system operation.

[0027] When the charging cover is pushed too quickly, the back EMF voltage of the three-phase motor 4 is proportional to the rotational speed. When the back EMF voltage of the U phase reaches or exceeds a certain voltage value, the voltage regulator diode Z1 breaks down and turns on, causing the NPN transistor Q1 to saturate and turn on, and the collector of the NPN transistor Q1 is pulled down to 0V. Since the base of the PNP transistor Q2 is connected to the collector of the NPN transistor Q1 and the voltage is both 0V, the emitter of the PNP transistor Q2 is at a high level (the voltage of the power supply VDD), so the PNP transistor Q2 is saturated and turns on, and the collector of the PNP transistor Q2 is also at a high level (the voltage of the power supply VDD). When the MCU's MON interface detects the voltage jump from 0V to a high level, its IO interface will output a high level, turning on the NMOS transistor Q3. The V phase dissipates the energy caused by the excessive speed through resistor R3, thus reducing the speed of the three-phase motor 4 and protecting the charging cover motor (i.e., the three-phase motor 4) from damage due to the high speed.

[0028] Even if the system enters sleep mode, since the MON interface of the MCU chip U1 has a special wake-up function, when the charging cover is pushed externally or the speed of the three-phase motor 4 is too high, the system will be awakened and the energy consumption circuit 2 will work normally to protect the charging cover from being damaged.

Claims

1. A three-phase motor active braking circuit, characterized in that: It includes a speed detection circuit, an energy consumption circuit and a controller; The speed detection circuit includes an overvoltage detection element and a level signal generating circuit; a first end of the overvoltage detection element is connected to any one phase of the three-phase motor, a second end of the overvoltage detection element is connected to an input end of the level signal generating circuit, and an output end of the level signal generating circuit is connected to an input end of the controller; the overvoltage detection element is configured to control the level signal generating circuit to output a first level signal to the controller when the back electromotive force voltage of any one phase of the three-phase motor is lower than a preset voltage, and to control the level signal generating circuit to output a second level signal to the controller when the back electromotive force voltage of any one phase of the three-phase motor is equal to or higher than the preset voltage; The energy consumption circuit is connected between any phase of the three-phase motor and the ground, and includes an energy consumption element for consuming electric energy and a control switch for controlling whether the energy consumption element is working; The output end of the controller is connected to the controlled end of the control switch. The controller is used to control the control switch to be turned off when receiving the first level signal so that the energy-consuming element does not work, and to control the control switch to be turned on when receiving the second level signal so that the energy-consuming element consumes electrical energy.

2. The three-phase motor active braking circuit according to claim 1, characterized in that: The level signal generating circuit includes a switch element Q1, a switch element Q2, a resistor R1 and a resistor R2; A first end of the resistor R1 and a first conductive end of the switch element Q2 are respectively connected to a power supply VDD, a common point between the second end of the resistor R1 and the first conductive end of the switch element Q1 is connected to a controlled end of the switch element Q2, a second conductive end of the switch element Q2 is connected to the first end of the resistor R2, and the second end of the resistor R2 and the second conductive end of the switch element Q1 are both grounded; The controlled end of the switch element Q1 constitutes the input end of the level signal generating circuit, and the common connection point of the second conducting end of the switch element Q2 and the first end of the resistor R2 constitutes the output end of the level signal generating circuit.

3. The three-phase motor active braking circuit according to claim 2, characterized in that: The switch element Q1 is an NPN transistor, and the base, collector and emitter of the NPN transistor respectively constitute the controlled end, the first conducting end and the second conducting end of the switch element Q1.

4. The three-phase motor active braking circuit according to claim 2, characterized in that: The switching element Q2 is a PNP transistor, and the base, emitter and collector of the PNP transistor Q2 constitute the controlled end, the first conducting end and the second conducting end of the switching element Q2 respectively.

5. The three-phase motor active braking circuit according to claim 1, characterized in that: The overvoltage detection element is composed of a voltage regulator tube Z1, and the cathode and anode of the voltage regulator tube Z1 respectively constitute the first end and the second end of the overvoltage detection element.

6. The three-phase motor active braking circuit according to claim 1, characterized in that: The energy consumption element includes a resistor R3, a first end of the resistor R3 is connected to any phase of the three-phase motor, a second end of the resistor R3 is connected to the first conductive end of the control switch, and the second conductive end of the control switch is grounded.

7. The three-phase motor active braking circuit according to claim 6, characterized in that: The control switch is composed of an NMOS transistor Q3 , and the gate, drain, and source of the NMOS transistor Q3 respectively constitute the controlled end, the first conducting end, and the second conducting end of the control switch.

8. The three-phase motor active braking circuit according to claim 1, characterized in that: The controller includes an MCU.

9. The three-phase motor active braking circuit according to claim 1, characterized in that: The controller uses an MCU of model TLE9879 manufactured by Infineon Technologies, the MON interface of the MCU constitutes the input end of the controller, and the IO interface of the MCU constitutes the output end of the controller; The first level signal is a low level signal, and the second level signal is a high level signal.

10. The three-phase motor active braking circuit according to claim 1, characterized in that: The three-phase motor is a brushless DC motor.

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