TWI719930B - Overvoltage protection circuit - Google Patents

Abstract

An overvoltage protection circuit can be applied to a motor controller. The motor controller is used for driving a motor, where the motor has a motor coil. The motor coil has a first terminal and a second terminal. The motor controller comprises the overvoltage protection circuit and a switch circuit. The switch circuit is an H-bridge circuit and includes two upper-side switches and two lower-side switches. The overvoltage protection circuit comprises a pre-driver, a phase detecting unit, a control unit, and an overvoltage detecting circuit. When an overvoltage occurs at the first terminal or the second terminal, the overvoltage protection circuit is configured to suppress a voltage spike by turning on two upper-side switches or two lower-side switches.

Description

Overvoltage protection circuit

The present invention relates to an overvoltage protection circuit, in particular to an overvoltage protection circuit which can be applied to a motor controller.

Figure 1 is a schematic diagram of a conventional motor controller 10. The motor controller 10 is used to drive a motor, wherein the motor has a motor coil L. The motor coil L has a first end O1 and a second end O2. The motor controller 10 has a switch circuit 100, a control unit 110, and a phase detection unit 120. The switch circuit 100 is coupled to a terminal VCC and the terminal VCC generates a supply current IVCC. The switching circuit 100 has a transistor 101, a transistor 102, a transistor 103, and a transistor 104 for providing a motor current to the motor coil L. The phase detection unit 120 generates a phase signal Vph to the control unit 110 to notify the control unit 110 to switch the phase. The control unit 110 generates four driving signals to the switch circuit 100 to control the conduction status of the transistor 101, the transistor 102, the transistor 103, and the transistor 104, respectively.

Figure 2 is a timing diagram of related signals corresponding to Figure 1. Please refer to Figure 1 and Figure 2 at the same time. When the motor is driving forward, it can be set that the transistor 101 and the transistor 104 are conductive and the transistor 102 and the transistor 103 are not conductive. At this time, the motor current flows from the terminal VCC to the transistor 101 and the first terminal O1 in sequence. , The second terminal O2, the transistor 104, and finally flow to a terminal GND. When the motor needs to decelerate or turn, it is set that the transistor 102 and the transistor 103 are conductive and the transistor 101 and the transistor 104 are not conductive, so as to reduce the motor current or reverse the direction of the motor current. At this time, the motor current will maintain its original direction due to inertial motion, that is, the motor current flows from the terminal GND to the transistor 102, the first terminal O1, the second terminal O2, the transistor 103, and finally to the terminal. The point VCC causes the voltage of the terminal VCC to rise and a voltage surge is generated. If the voltage of the terminal VCC is greater than the withstand voltage of the switch circuit 100, the switch circuit 100 may be damaged. Traditionally, a capacitor C or an audit diode ZD can be coupled between the terminal VCC and the terminal GND to absorb excessive energy or to clamp the voltage surge, but this method will increase the manufacturing cost.

In view of the foregoing problems, the object of the present invention is to provide an overvoltage protection circuit to protect the switching circuit and reduce the manufacturing cost.

According to the present invention, the motor controller is provided. The motor controller is used to drive a motor, wherein the motor has a motor coil. The motor coil has a first end and a second end. The motor controller has a switch circuit and an overvoltage protection circuit, wherein the overvoltage protection circuit is coupled to the switch circuit to avoid damage to the switch circuit. The switch circuit is coupled to a terminal VCC and the terminal VCC generates a supply current to the switch circuit. The switch circuit is used to provide a motor current to the motor coil, wherein the motor current can be analogous to the supply current. The switch circuit has a first transistor, a second transistor, a third transistor, and a fourth transistor. In addition, the switch circuit is an H-bridge circuit. The first transistor and the third transistor are respectively an upper switch and the second transistor and the fourth transistor are respectively a lower switch.

The overvoltage protection circuit has a pre-driver, a phase detection unit, a control unit, and an overvoltage detection circuit. The phase detection unit generates a phase signal to the control unit to notify the control unit to switch the phase. The overvoltage detection circuit has a first resistor, a second resistor, and a comparator for generating a detection signal to the control unit. The first resistor is coupled to the terminal VCC and the second resistor and the second resistor is coupled to a terminal GND for generating a feedback voltage to the comparator. The comparator compares the feedback voltage with a reference voltage to output the detection signal. Therefore, the overvoltage detection circuit can be used to set a predetermined value to represent the overvoltage protection value of the terminal VCC. When an overvoltage occurs at the terminal VCC, it means that an overvoltage occurs at the first terminal or the second terminal. Therefore, the overvoltage detection circuit is also suitable for detecting whether an overvoltage occurs at the first terminal or the second terminal.

The control unit receives the phase signal and the detection signal to generate a control signal to the pre-driver, wherein the control unit determines whether to enter an overvoltage protection mechanism according to the detection signal. The pre-driver generates a first drive signal, a second drive signal, a third drive signal, and a fourth drive signal according to the control signal to control the first transistor and the second transistor respectively , The conduction status of the third transistor and the fourth transistor.

When an overvoltage occurs at the first terminal or the second terminal, the overvoltage protection circuit suppresses a voltage surge and protects the switch circuit by turning on two upper switches or two lower switches. Since there is no need to add external components, the manufacturing cost can be reduced.

The following description will make the purpose, features, and advantages of the present invention more obvious. The preferred embodiments according to the present invention will be described in detail with reference to the drawings.

FIG. 3 is a schematic diagram of the motor controller 20 and the overvoltage protection circuit 300 according to an embodiment of the present invention. The motor controller 20 is used to drive a motor, wherein the motor has a motor coil L. The motor coil L has a first end O1 and a second end O2. The motor controller 20 has a switch circuit 200 and an overvoltage protection circuit 300, wherein the overvoltage protection circuit 300 is coupled to the switch circuit 200 to prevent the switch circuit 200 from being damaged. The switch circuit 200 is coupled to a terminal VCC and the terminal VCC generates a supply current IVCC to the switch circuit 200. The switch circuit 200 is used to provide a motor current to the motor coil L, where the motor current can be analogous to the supply current IVCC. The switch circuit 200 has a first transistor 201, a second transistor 202, a third transistor 203, and a fourth transistor 204. The first transistor 201 is coupled to the terminal VCC and the first terminal O1, and the second transistor 202 is coupled to the first terminal O1 and a terminal GND. The third transistor 203 is coupled to the terminal VCC and the second terminal O2, and the fourth transistor 204 is coupled to the second terminal O2 and the terminal GND. The first transistor 201, the second transistor 202, the third transistor 203, and the fourth transistor 204 can be a P-type metal oxide semi-transistor or an N-type metal oxide semi-transistor. In Figure 3, the first transistor 201 and the third transistor 203 are two P-type metal oxide semi-transistors as an example. The second transistor 202 and the fourth transistor 204 are based on two N-type metal oxide semi-transistors as an example. In addition, the switch circuit 200 is an H-bridge circuit. The first transistor 201 and the third transistor 203 are respectively an upper switch and the second transistor 202 and the fourth transistor 204 are respectively a lower switch.

The overvoltage protection circuit 300 has a pre-driver 310, a phase detection unit 320, a control unit 330, and an overvoltage detection circuit 340. The phase detection unit 320 generates a phase signal Vph to the control unit 330 to notify the control unit 330 to switch phases, where the phase detection unit 320 can be a Hall sensor. The Hall sensor is arranged near the motor to sense the change of the magnetic field of the motor. The overvoltage detection circuit 340 has a first resistor R1, a second resistor R2, and a comparator 341 for generating a detection signal Vd to the control unit 330. The first resistor R1 is coupled to the terminal VCC and the second resistor R2, and the second resistor R2 is coupled to the terminal GND to generate a feedback voltage Vfb to the comparator 341. The comparator 341 compares the feedback voltage Vfb with a reference voltage Vr to output the detection signal Vd. Therefore, the overvoltage detection circuit 340 can be used to set a predetermined value to represent the overvoltage protection value of the terminal VCC. When an overvoltage occurs at the terminal VCC, it means that an overvoltage occurs at either the first terminal O1 or the second terminal O2. Therefore, the overvoltage detection circuit 340 is also suitable for detecting whether an overvoltage occurs at the first terminal O1 or the second terminal O2.

The control unit 330 receives the phase signal Vph and the detection signal Vd to generate a control signal Vc to the pre-driver 310. The control unit 330 determines whether to enter an overvoltage protection mechanism according to the detection signal Vd. The pre-driver 310 generates a first driving signal D1, a second driving signal D2, a third driving signal D3, and a fourth driving signal D4 according to the control signal Vc to control the first transistor 201 and the second transistor respectively. The conduction status of the second transistor 202, the third transistor 203, and the fourth transistor 204.

Figure 4 is a timing diagram of the relevant signals corresponding to Figure 3. Please refer to Figure 3 and Figure 4 at the same time. Since the phase signal Vph is a periodic signal and has a period T, a commutation time Tp can be defined as 1/2 period T. In other words, the time interval from time point 0 to time point T1 is the commutation time Tp. The time interval from time point T1 to time point T2 is the commutation time Tp. The time interval from the time point T2 to the time point T3 is the commutation time Tp. The time interval from time T3 to time T4 is the commutation time Tp.

Specifically, when the motor changes from a forward rotation state to a braking state at time T1, if the voltage of the terminal VCC is greater than a predetermined value, the detection signal Vd will change from a low level L to a high level H to notify the control The unit 330 enters the overvoltage protection mechanism. At this time, the second transistor 202 and the fourth transistor 204 are set to be turned on and the first transistor 201 and the third transistor 203 are not turned on, so that the voltage of the first terminal O1 and the voltage of the second terminal O2 are forced to be pulled To the low level L to suppress the voltage surge of the second terminal O2. In addition, after the conduction time between the second transistor 202 and the fourth transistor 204 lasts for at least one commutation time Tp, the second transistor 202 and the fourth transistor 204 are set to be non-conductive or the second transistor 202 and the fourth transistor 204 are set to be non-conductive. One of the fourth transistors 204 is not turned on to leave the overvoltage protection mechanism. The purpose is to ensure that the motor current approaches 0 or equals to 0 before leaving the overvoltage protection mechanism to prevent voltage surges from occurring again. In order to reduce the temperature of the switch circuit 200, the motor can be driven again after at least N commutation times Tp after leaving the overvoltage protection mechanism, where N≥1 and N is a positive integer. Another embodiment of the present invention can also choose to set the first transistor 201 and the third transistor 203 to conduct and the second transistor 202 and the fourth transistor 204 to not conduct when entering the overvoltage protection mechanism to suppress the voltage surge. Similarly, when the motor changes from a reverse rotation state to a braking state, the overvoltage protection circuit 300 of the present invention can also be used to suppress the voltage surge generated by the first terminal O1.

The overvoltage protection circuit 300 of the present invention can be applied to a single-phase motor. When an overvoltage occurs at the first terminal O1 or the second terminal O2, the overvoltage protection circuit 300 suppresses a voltage surge and protects the switch circuit 200 by turning on the two upper switches or the two lower switches. Since there is no need to add external components, the manufacturing cost can be reduced.

Although the present invention has been described with the preferred embodiment as an example, it should be understood that the present invention is not limited to the disclosed embodiment. On the contrary, the present invention is intended to cover various modifications and similar configurations that are obvious to those familiar with the art. Therefore, the scope of patent application should be based on the broadest interpretation to include all such modifications and similar configurations. The foregoing descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made in accordance with the scope of the patent application of the present invention should fall within the scope of the present invention.

10: Motor controller 100: switch circuit 110: control unit 120: Phase detection unit 101, 102, 103, 104: Transistor C: Capacitance ZD: Sensing diode 20: Motor controller VCC: Endpoint GND: terminal IVCC: Supply current 200: switch circuit 300: Overvoltage protection circuit 310: Front Drive 320: Phase detection unit 330: control unit 340: Overvoltage detection circuit 341: Comparator R1: first resistance R2: second resistor Vph: phase signal Vc: control signal Vd: detection signal Vfb: feedback voltage Vr: Reference voltage 201: first transistor 202: second transistor 203: Third Transistor 204: Fourth Transistor D1: the first drive signal D2: second drive signal D3: Third drive signal D4: Fourth drive signal L: Motor coil O1: first endpoint O2: second endpoint T: period T1, T2, T3, T4: point in time Tp: Commutation time

Figure 1 is a schematic diagram of a conventional motor controller. Figure 2 is a timing diagram of related signals corresponding to Figure 1. Figure 3 is a schematic diagram of a motor controller and an overvoltage protection circuit according to an embodiment of the present invention. Figure 4 is a timing diagram of the relevant signals corresponding to Figure 3.

20: Motor controller

VCC: Endpoint

GND: terminal

IVCC: Supply current

200: switch circuit

300: Overvoltage protection circuit

310: Front Drive

320: Phase detection unit

330: control unit

340: Overvoltage detection circuit

341: Comparator

R1: first resistance

R2: second resistor

Vph: phase signal

Vc: control signal

Vd: detection signal

Vfb: feedback voltage

Vr: Reference voltage

201: first transistor

202: second transistor

203: Third Transistor

204: Fourth Transistor

D1: the first drive signal

D2: second drive signal

D3: Third drive signal

D4: Fourth drive signal

L: Motor coil

O1: first endpoint

O2: second endpoint

Claims (20)

An overvoltage protection circuit is used to protect an H-bridge circuit. The H-bridge circuit is used to provide a motor current to a motor coil and the motor coil has a first end and a second end. The H bridge The circuit has two upper switches and two lower switches. The overvoltage protection circuit includes: A pre-driver for generating a plurality of driving signals to control the H-bridge circuit; and A control unit for generating a control signal to the pre-driver, wherein when an overvoltage occurs at the first terminal or the second terminal, the two lower switches are set to be turned on. For the overvoltage protection circuit described in item 1 of the scope of patent application, when an overvoltage occurs at the first terminal or the second terminal, the two upper switches are set to be non-conducting. In the overvoltage protection circuit described in item 1 of the scope of patent application, the two upper switches are respectively a P-type metal oxide semi-transistor, and the two lower switches are respectively an N-type metal oxide semi-transistor. The overvoltage protection circuit described in item 1 of the scope of patent application, wherein the overvoltage protection circuit is applied to a single-phase motor. For the overvoltage protection circuit described in item 1 of the scope of patent application, the overvoltage protection circuit further includes a phase detection unit, and the phase detection unit is used to generate a phase signal to the control unit to switch the phase. The signal is a periodic signal and has a period. For the overvoltage protection circuit described in item 5 of the scope of patent application, the on-time of the two lower switches is set to last for at least one commutation time, wherein the commutation time is 1/2 cycle. For example, in the overvoltage protection circuit described in item 6 of the scope of patent application, the two lower switches are set to be non-conductive only after the conduction time of the two lower switches is set to last for at least one commutation time. For the overvoltage protection circuit described in item 6 of the scope of patent application, one of the two lower switches is set to be non-conducting only after the conduction time of the two lower switches is set to last for at least one commutation time. An overvoltage protection circuit is used to protect an H-bridge circuit. The H-bridge circuit is used to provide a motor current to a motor coil and the motor coil has a first end and a second end. The H bridge The circuit has two upper switches and two lower switches. The overvoltage protection circuit includes: A pre-driver for generating a plurality of driving signals to control the H-bridge circuit; and A control unit for generating a control signal to the pre-driver, wherein when an overvoltage occurs at the first terminal or the second terminal, the two upper switches are set to be turned on. For the overvoltage protection circuit described in item 9 of the scope of patent application, when an overvoltage occurs at the first terminal or the second terminal, the two lower switches are set to be non-conducting. An overvoltage protection circuit is used to protect a switch circuit. The switch circuit is used to provide a motor current to a motor coil. The motor coil has a first end and a second end. The switch circuit has a first end. Transistor, a second transistor, a third transistor, and a fourth transistor, the first transistor is coupled to a third terminal and the first terminal, and the second transistor is coupled to the first terminal A terminal and a fourth terminal, the third transistor is coupled to the third terminal and the second terminal, and the fourth transistor is coupled to the second terminal and the fourth terminal, the pass Voltage protection circuit includes: A pre-driver for generating a plurality of driving signals to control the switch circuit; A control unit for generating a control signal to the pre-driver; A phase detection unit for generating a phase signal to the control unit to switch the phase, wherein the phase signal is a periodic signal and has a period; and An overvoltage detection circuit for generating a detection signal to the control unit, wherein when an overvoltage occurs at the first terminal or the second terminal, the second transistor and the fourth transistor are set to conduct To enter an overvoltage protection mechanism. For example, the overvoltage protection circuit described in item 11 of the scope of patent application, wherein when an overvoltage occurs at the first terminal or the second terminal, the first transistor and the third transistor are set to be non-conducting to enter the Overvoltage protection mechanism. The overvoltage protection circuit described in item 12 of the scope of patent application, wherein the overvoltage protection circuit is applied to a single-phase motor. In the overvoltage protection circuit described in item 13 of the scope of patent application, the conduction time of the second transistor and the fourth transistor is set to last for at least one commutation time, wherein the commutation time is 1/2 cycle. For example, the overvoltage protection circuit described in item 14 of the scope of patent application, wherein the conduction time of the second transistor and the fourth transistor is set to last for at least one commutation time before the second transistor and the fourth transistor are set The transistor does not conduct to leave the overvoltage protection mechanism. For example, the overvoltage protection circuit described in item 14 of the scope of patent application, wherein the conduction time of the second transistor and the fourth transistor is set to last for at least one commutation time before the second transistor and the fourth transistor are set One of the transistors does not conduct to leave the overvoltage protection mechanism. For example, the overvoltage protection circuit described in item 15 of the scope of patent application, wherein the single-phase motor is driven to run again after at least N commutation times after leaving the overvoltage protection mechanism, where N≥1 and N is a positive integer . For example, the overvoltage protection circuit described in item 16 of the scope of patent application, wherein the single-phase motor is driven to run again after at least N commutation times after leaving the overvoltage protection mechanism, where N≥1 and N is a positive integer . Such as the overvoltage protection circuit described in item 11 of the scope of patent application, wherein the overvoltage detection circuit includes: A first resistor coupled to the third terminal; A second resistor, coupled to the first resistor and the fourth terminal, for generating a feedback voltage; and A comparator is used to output the detection signal by comparing the feedback voltage with a reference voltage. The overvoltage protection circuit described in item 11 of the scope of patent application, wherein the first transistor and the third transistor are respectively a P-type metal oxide semi-transistor, and the second transistor and the fourth transistor are They are respectively an N-type metal oxide semi-transistor.

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