Safe torque turn-off circuit used in frequency converter

Abstract

A safe torque turn-off (STO) circuit for use in a frequency converter is disclosed. The frequency converter includes a motor driver and a motor controller. The motor driver includes a high-side driver and a low-side driver for a high-side IGBT and a low-side IGBT, respectively. The STO circuit comprises a first optocoupler which comprises a first primary side for receiving a first STO signal and a first secondary side, and the first secondary side cuts off power supply of a high-side driver according to the effective first STO signal; the second optocoupler comprises a second primary side for receiving a second STO signal and a second secondary side, and the second secondary side cuts off the power supply of the low-side driver according to the effective second STO signal; the third optocoupler comprises a third primary side and a third secondary side which are used for receiving a logical operation result of the first STO signal and the second STO signal, the third secondary side is used for cutting off the supply of a driving control signal of the motor controller according to an effective logical operation result, and the logical operation is that when at least one of the first STO signal and the second STO signal is effective, the third primary side and the third secondary side cut off the supply of the driving control signal of the motor controller. The result of the logical operation is also effective.

Description

[0001] This application is a divisional application of the invention patent application with application number 202110617526.4 filed on June 2, 2021 and named "Safe Torque Off Circuit and Inverter Including the Circuit". Technical Field

[0002] The present disclosure relates to the field of electronic circuits, and more particularly, to a safe torque off (STO) circuit with improved reliability and an inverter including the same. Background Art

[0003] Currently, safe torque-off (STO) circuits often employ dual-channel designs. To improve safety, these circuits often employ dynamic detection mechanisms or use dynamic power supplies. However, dynamic detection mechanisms are complex in logic, and dynamic power supplies require bulky and costly electrical isolation transformers, which negatively impact design and cost.

[0004] CN109428585A discloses a dual-branch control circuit based on an optocoupler and its method. Specifically, it uses a diagnostic circuit to determine whether the optocoupler has failed based on the output and power supply status of the optocoupler's secondary side, thereby improving circuit reliability and safety. CN207884588U discloses a safe torque off circuit that uses a dual-channel design. The primary sides of the first and second optocouplers are connected in series. When the STO signal of either channel is enabled, both STO channels will trigger the safe torque off. Summary of the Invention

[0005] In view of the above, an object of the present disclosure is at least partially to provide a safe torque off (STO) circuit with improved reliability and an inverter including the same.

[0006] According to an embodiment of the present disclosure, a circuit with an STO function is provided, including: a first STO channel, configured to control the on-off of power supply to a high-side driver of an inverter according to a first STO signal; a second STO channel, configured to control the on-off of power supply to a low-side driver of the inverter according to a second STO signal; and a third STO channel, configured to control the provision of a drive control signal from a controller of the inverter to the high-side driver and the low-side driver according to a logical operation result of the first STO signal and the second STO signal, wherein the logical operation is such that when at least one of the first STO signal and the second STO signal is valid, the logical operation result is also valid.

[0007] According to an embodiment, the power supply to the high-side driver may be stopped according to the valid first STO signal. Similarly, the power supply to the low-side driver may be stopped according to the valid second STO signal.

[0008] The first STO channel may include: a first isolation device including a first primary side and a first secondary side, wherein the first primary side is configured to receive a first STO signal; and a first switching device whose on / off is controlled by the first secondary side, connected between a power supply of a high-side driver and the high-side driver, wherein the first secondary side is connected to turn off the first switching device when the first STO signal is valid. The second STO channel may include: a second isolation device including a second primary side and a second secondary side, wherein the second primary side is configured to receive a second STO signal; and a second switching device whose on / off is controlled by the second secondary side, connected between a power supply of a low-side driver and the low-side driver, wherein the second secondary side is connected to turn off the second switching device when the second STO signal is valid.

[0009] The third STO channel may include: a third isolation device, including a third primary side and a third secondary side, wherein the third primary side is configured to receive a logic operation result of the first STO signal and the second STO signal, wherein the third secondary side is connected to stop providing the drive control signal when at least one of the first STO signal and the second STO signal is valid.

[0010] The third primary can be connected between the first STO signal and ground to form a current path from the first STO signal through the third primary to ground. The circuit can further include a switching device disposed in the current path, wherein a control terminal of the switching device is controlled by the second STO signal. For example, the switching device can be connected between the first STO signal and the third primary, or between the third primary and ground.

[0011] The circuit may further include: a gate driver connected to a control terminal of the switching device, wherein the gate driver operates under control of the second STO signal.

[0012] Alternatively, the third primary can be connected between the first STO signal and ground to form a current path from the first STO signal through the third primary to ground. The circuit can further include a bypass branch connected in parallel with the current path, the bypass branch being controlled by the second STO signal. For example, the bypass branch can include a switching device, the control terminal of which is controlled by the second STO signal.

[0013] Alternatively, the output of the third secondary side can be connected to the enable terminal of the controller. For example, the third isolation device may include an optocoupler. One end of the third secondary side is connected to the first power supply, and the other end is connected to the ground voltage through a resistor. The output voltage at the other end is connected to the enable terminal of the controller.

[0014] Alternatively, the third STO channel may further include a third switching device, whose on / off control is controlled by a third secondary side, connected between the controller and the high-side driver and the low-side driver. For example, the third switching device may include a first transmission gate connected between the controller and the high-side driver, configured to transmit a drive control signal from the controller to the high-side driver; and a second transmission gate connected between the controller and the low-side driver, configured to transmit a drive control signal from the controller to the low-side driver. The output of the third secondary side is connected to the enable terminals of the first transmission gate and the second transmission gate, respectively. For example, the third isolation device may include an optocoupler, with one end of the third secondary side connected to the first power supply via a resistor and the other end connected to ground. The output voltage at the one end is connected to the enable terminals of the first transmission gate and the second transmission gate, respectively.

[0015] Alternatively, the output of the third secondary side can be connected to a clock generator that provides a clock signal to the controller. The circuit may further include: a third switching device whose on / off is controlled by the third secondary side, connected between a power supply of the clock generator and the clock generator, wherein the third secondary side is connected to turn off the third switching device when at least one of the first STO signal and the second STO signal is active.

[0016] According to the disclosed embodiments, an AND gate may be constructed by discrete components to perform the logic operation.

[0017] According to an embodiment of the present disclosure, the circuit may further include: a first switch configured to control whether the first STO signal is provided to the first STO channel; a second switch configured to control whether the second STO signal is provided to the second STO channel; and a third switch configured to control whether the circuit is grounded.

[0018] According to an embodiment of the present disclosure, a frequency converter is provided, comprising the above circuit.

[0019] According to an embodiment of the present disclosure, a circuit with a safe torque off (STO) function is provided, including: three STO channels, respectively receiving a first STO signal, a second STO signal, and a signal after a logical operation of the first STO signal and the second STO signal, and controlling the power supply of the high-side driver, the power supply of the low-side driver, and the provision of a drive control signal of the inverter according to the received signals, wherein the logical operation is: when at least one of the first STO signal and the second STO signal is valid, the signal after the logical operation is also valid; the drive control signal is provided by the controller of the inverter to the high-side driver and the low-side driver.

[0020] According to an embodiment of the present disclosure, an STO circuit for use in a frequency converter is provided. The frequency converter includes a motor driver and a motor controller, wherein the motor driver includes a high-side driver and a low-side driver for high-side IGBTs and low-side IGBTs, respectively. The STO circuit includes: a first optocoupler including a first primary side and a first secondary side, the first primary side receiving a first STO signal, and the first secondary side cutting off power to the high-side driver based on a valid first STO signal; a second optocoupler including a second primary side and a second secondary side, the second primary side receiving a second STO signal, and the second secondary side cutting off power to the low-side driver based on a valid second STO signal; and a third optocoupler including a third primary side and a third secondary side, the third primary side receiving a result of a logical operation of the first STO signal and the second STO signal, and the third secondary side cutting off the supply of a drive control signal to the motor controller based on the valid result of the logical operation, wherein the logical operation is such that when at least one of the first STO signal and the second STO signal is valid, the result of the logical operation is also valid.

[0021] According to an embodiment of the present disclosure, the STO circuit includes three STO channels, creating a "one out of three" (1oo3) structure. Each channel can independently shut down the motor. In other words, the STO circuit according to an embodiment of the present disclosure can tolerate two faults while still maintaining the STO function, resulting in a hardware fault tolerance (HFT) of 2. Therefore, inverters using this STO circuit can simply and effectively achieve a higher level of safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0023] Figure 1 A block diagram of a circuit with a safe torque off (STO) function is schematically shown;

[0024] Figure 2 Schematically shows a principle diagram of a circuit with an STO function according to an embodiment of the present disclosure;

[0025] Figures 3 to 5 Schematic diagrams of circuits with STO functions according to embodiments of the present disclosure are respectively shown;

[0026] Figure 6 Schematically illustrates various circuit diagrams for implementing an AND operation on level signals according to an embodiment of the present disclosure;

[0027] Figure 7A schematic diagram showing an input portion of a circuit with an STO function according to an embodiment of the present disclosure is shown.

[0028] Throughout the drawings, the same or similar reference numerals refer to the same or similar parts. DETAILED DESCRIPTION

[0029] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely illustrative and are not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0030] The terms used herein are intended only to describe specific embodiments and are not intended to limit the present disclosure. The terms "a," "an," and "the" as used herein also include "plurality" and "multiples," unless the context clearly indicates otherwise. Furthermore, the terms "comprise," "include," and "includes" as used herein indicate the presence of the described features, steps, operations, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.

[0031] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0032] Unless otherwise expressly indicated, the numerical parameters in this specification and the appended claims are approximate and can vary depending on the desired properties obtained through the content of the present disclosure. Specifically, all numbers used in the specification and claims to express composition amounts, reaction conditions, etc. should be understood to be modified by the term "about" in all cases. Generally, the meaning of the expression is intended to include the specific amount, for example, in some embodiments, ±10% or more or less.

[0033] The use of ordinal numbers such as "first," "second," and "third" in the specification and claims to modify corresponding elements does not, in itself, indicate any ordinal number for the elements, nor does it indicate the order, manufacturing sequence, or importance of one element relative to another. Ordinal numbers are used only to clearly distinguish one element from another element with the same name.

[0034] Figure 1 A block diagram of a circuit with a safe torque off (STO) function is shown schematically.

[0035] This circuit diagram schematically shows the signal flow and schematic connection relationship of using a frequency converter to control a motor. Figure 1 As shown, depending on the operating voltage and safety considerations, the circuit can be divided into a low-voltage (e.g., protective extra-low voltage, PELV) side and a high-voltage side. The low-voltage side primarily handles low-voltage operations, such as various control signals, while the high-voltage side primarily handles high-voltage operations, such as powering a load (e.g., a motor). For electrical safety reasons, an electrical isolation component, such as an optocoupler 101, is typically provided between the low-voltage and high-voltage sides. Optocoupler 101 not only provides electrical isolation between the low-voltage and high-voltage sides, but also optically transmits control from the low-voltage side to the high-voltage side. The following description uses an optocoupler as an example of an electrical isolation component. However, it should be understood that the present disclosure is not limited to this. For example, components such as capacitive couplings and magnetic couplings that both provide electrical isolation and signal transmission between the low-voltage and high-voltage sides may also be used.

[0036] Specifically, the optocoupler 101 may include a primary side 101P and a secondary side 101S. The primary side 101P may be in the form of a light-emitting diode (LED) that is turned on or off based on the STO signal received at the signal input terminal. Generally, the STO signal is inactive when at a high level (e.g., approximately 24V), indicating that the motor is operating normally and does not need to be shut down; and is active when at a low level (e.g., a low voltage such as 0V or an open circuit), indicating that the motor should be shut down. Here, "high level" refers to a voltage that effectively turns on the LED on the primary side 101P of the optocoupler 101, while "low level" refers to a voltage that keeps the LED off. For example, when the STO signal is high (causing the voltage across the LED to exceed the LED's turn-on voltage), the LED may turn on and emit light. However, when the STO signal is enabled (e.g., at a low level or an open circuit), the LED may be turned off. Secondary side 101S can be in the form of a transistor, and the light signal emitted by the LED on primary side 101P can serve as its base signal. More specifically, when the LED on primary side 101P is on and emitting light, the transistor on secondary side 101S can be turned on; and when the LED on primary side 101P is off and not emitting light, the transistor on secondary side 101S can be turned off.

[0037] Therefore, the secondary side 101S can be turned on or off based on the STO signal received by the primary side. This on / off switching of the secondary side 101S controls the power supply to the power supply circuit 103. For example, when the transistor on the secondary side 101S is on, the power supply circuit 103 is controlled to supply power; when the transistor on the secondary side 101S is off, the power supply circuit 103 stops supplying power. Consequently, the motor driver 105 powered by the power supply circuit 103 can operate (when powered) or stop operating (when not powered) based on the STO signal received by the primary side 101P.

[0038] In an optocoupler, the primary side 101P is in the form of a diode and the secondary side 101S is in the form of a transistor, and signals are transmitted optically between the two. As mentioned above, the present disclosure is not limited to this. For example, the capacitive coupling can be in the form of a capacitor, and the magnetic coupling can be in the form of a transformer. Regardless of the form of the electrical isolation component, in the present disclosure, the so-called "primary side" refers to the side that receives the STO signal, and the "secondary side" refers to the other side of the electrical isolation component. The primary side exhibits different states depending on the high and low levels of the STO signal received by the primary side (for example, outputting signals of different levels depending on the connection method), and can therefore control the output of the connected circuit.

[0039] The motor driver 105 can operate according to the drive control signal provided by the motor controller 107 while powered by the power supply circuit 103. Specifically, the motor driver 105 can output a drive signal to the motor based on the drive control signal provided by the motor controller 107 (for controlling the rotation / stop, speed, etc. of the motor, such as a pulse width modulation (PWM) signal), to drive the motor. Typically, the drive control signal provided by the motor controller 107, such as the PWM signal, is a low-voltage signal (e.g., approximately 3.3V). The motor driver 105 can utilize the power supplied by the power supply circuit 103 to output a high-voltage drive signal (e.g., approximately 18V). The drive signal corresponds to the drive control signal and can, for example, be a PWM signal having the same waveform.

[0040] The motor driver 105 can provide rotational torque to the motor through switching devices such as insulated gate bipolar transistors (IGBTs). For a three-phase motor, six IGBTs can usually be provided, three on the high side and three on the low side. The drive signal output by the motor driver 105 can be coupled to the gate of the IGBT to control the on and off of the IGBT. Accordingly, the motor controller 107 can output six drive control signals such as PWM signals for the six IGBTs. The motor driver 105 may include a high-side driver and a low-side driver for the high-side IGBT and the low-side IGBT, respectively (for example, see Figure 2 305H and 305L in FIG), which receive three corresponding drive control signals from the motor controller 107 and output three (gate) drive signals for the corresponding three IGBTs. By adjusting the duty cycle of the PWM signal, the motor speed can be adjusted.

[0041] exist Figure 1In the example shown, only a single STO channel is shown. Dual STO channels can also be set up. Typically, the two STO channels are set up separately to form a redundant configuration. For example, one channel can be used to control the high-side driver for the high-side IGBT, and the other channel can be used to control the low-side driver for the low-side IGBT. Each channel can receive an STO signal separately. When the STO signal of any channel is enabled and valid, the corresponding driver can be powered off, thereby stopping driving the corresponding high-side or low-side IGBT and causing the motor to stop working, realizing the STO function.

[0042] According to an embodiment of the present disclosure, a three-channel STO configuration is provided. These three channels can independently output signals for shutting down the motor in response to a valid STO signal, thereby reducing the risk of failure to shut down the motor due to a fault in a single channel or dual channels.

[0043] Figure 2 The schematic diagram shows a principle diagram of a circuit with STO function according to an embodiment of the present disclosure.

[0044] like Figure 2 As shown, the circuit according to this embodiment has two STO channels (referred to as the "first STO channel" and the "second STO channel") for the high-side driver 305H and the low-side driver 305L, respectively. These channels operate in response to a first STO signal STO_a and a second STO signal STO_b, respectively. The first STO channel includes a first isolation component 301a, and the second STO channel includes a second isolation component 301b. As described above, the first isolation component 301a and the second isolation component 302a can include isolation components such as optocouplers, capacitive couplers, and magnetic couplers.

[0045] The first isolation device 301a receives a first STO signal STO_a, and its output controls the operation of the high-side driver 305H. For example, in response to an active first STO signal STO_a, it shuts off the power supply (Vdd1) to the high-side driver 305H. In this case, the first switching device 303a is connected between the power supply (Vdd1) of the high-side driver 305H and the high-side driver 305H, and the output of the first isolation device 301a can control the on / off switching of the first switching device 303a. The second isolation device 301b receives a second STO signal STO_b, and its output controls the operation of the low-side driver 305L. For example, in response to an active second STO signal STO_b, it shuts off the power supply (Vdd2) to the low-side driver 305L. In this case, the second switching device 303b is connected between the power supply (Vdd2) of the low-side driver 305L and the low-side driver 305L, and the output of the second isolation device 301b can control the on / off switching of the second switching device 303b.

[0046] In the figure, isolation devices 301a and 301b of two STO channels are shown controlling the power supply to high-side and low-side drivers 305H and 305L, respectively, via switching devices 303a and 303b. However, the present disclosure is not limited to this. The outputs of isolation devices 301a and 301b can also be connected to the enable terminals of high-side and low-side drivers 305H and 305L, thereby enabling or disabling the high-side and low-side drivers 305H and 305L to control their operation. For example, when either or both of the first STO signal STO_a and the second STO signal STO_b are enabled (valid), the output of the corresponding isolation device can disable the driver on the corresponding side, causing it to stop operating.

[0047] The first STO channel and the second STO channel can be respectively Figure 1 For example, when any one of the first STO signal STO_a and the second STO signal STO_b is enabled (valid), the corresponding switching device 303a or 303b can cut off the power supply to the corresponding driver 305H or 305L, thereby stopping the driver 305H or 305L from operating.

[0048] In addition to the first and second STO channels, the circuit may also include a third STO channel for the motor controller 307. The third STO channel may include a third isolation device 301c, whose output can control the motor controller 307 to provide drive control signals to the high-side and low-side drivers 305H and 305L. For example, a third switching device 303c may be connected between the motor controller 307 and the high-side and low-side drivers 305H and 305L, and the output of the third isolation device 301c can control the on and off of the third switching device 303c. Those skilled in the art will appreciate that controlling the signal provided by a signal source to a component is not limited to using a switching device in the transmission path between the signal source (in this example, the motor controller 307) and the component (in this example, the high-side and low-side drivers 305H and 305L). Other methods may also be used. For example, the operation of the signal source may be controlled. Similarly, the third isolation device 301c may include an isolation component such as an optocoupler, a capacitive coupler, or a magnetic coupler.

[0049] The third STO channel can operate based on the first STO signal STO_a and / or the second STO signal STO_b. Specifically, if either (or both) the first STO signal STO_a and the second STO signal STO_b are enabled (meaning the motor should be shut down), the third STO channel can also shut off the drive control signal from the motor driver 307 to the high-side and low-side drivers 305H and 305L by turning off the third switching device 303c. In other words, the third STO channel can be activated if either or both of the first STO signal STO_a and the second STO signal STO_b are enabled. This can be achieved by performing an AND operation on the level signals between the first STO signal STO_a and the second STO signal STO_b. Figure 2 The schematic diagram shows an AND gate 309 for realizing the AND of level signals. It should be noted that the AND gate 309 here only represents a functional module and can be realized by different circuit configurations, such as simply using several discrete devices, which will be referred to below. Figure 6 Further explanation.

[0050] If the drive control signal from motor driver 307 to high-side and low-side drivers 305H and 305L is cut off, high-side and low-side drivers 305H and 305L cannot generate corresponding drive signals due to lack of drive control signals, and thus can stop driving the motor. Thus, providing a third STO channel as a redundant configuration in addition to the first and second STO channels improves reliability and safety.

[0051] like Figure 2 As shown, only the third isolation device 301c, AND gate 309, and switch device 303c are required to implement a redundant configuration without changing other circuit components. Therefore, a higher level of security can be achieved with minimal cost (primarily the cost of the third isolation device 301c).

[0052] There are many ways to implement the third STO channel, some of which are described below. In these examples, for ease of describing the operation of the circuit, an optocoupler is used as an example to describe the electrical isolation component.

[0053] Figure 3 The figure schematically shows a circuit diagram of a circuit with an STO function according to an embodiment of the present disclosure.

[0054] like Figure 3As shown, the circuit according to this embodiment has a three-STO channel configuration, including a first optocoupler OP1, a second optocoupler OP2, and a third optocoupler OP3. The anode of the primary LED of the third optocoupler OP3 can be connected to receive a first STO signal STO1, and the cathode can be connected to ground via a switching device 409 (e.g., an NPN transistor). The second STO signal STO2 can be connected to a control terminal (e.g., a base terminal) of the switching device 409. In this example, the first STO signal STO1 can be considered the power supply for the primary LED of the third optocoupler OP3. The primary LED of the third optocoupler OP3 is connected between the power supply STO1 and ground. The switching device 409 (between the cathode of the primary LED of the third optocoupler OP3 and ground) can turn the circuit containing the primary LED of the third optocoupler OP3 on or off based on the second STO signal STO2. In this way, when either or both of the first STO signal STO1 and the second STO signal STO2 are enabled, the primary LED of the third optocoupler OP3 can be turned off. For example, when the first STO signal STO1 is enabled, the primary LED of the third optocoupler OP3 is turned off due to the lack of power supply. When the second STO signal STO2 is enabled, the primary LED of the third optocoupler OP3 is turned off due to the disconnection to ground. Thus, an "AND" operation of the level signals of the first STO signal STO1 and the second STO signal STO2 is achieved. Those skilled in the art are familiar with various "AND" operation circuits. Figure 3 The circuit shown in is only an example.

[0055] In this example, the signal input terminals of STO1 and STO2 are connected to 15V Zener diodes D1 and D2, respectively. The Zener diodes D1 and D2 can provide a stable STO trigger threshold voltage.

[0056] One end of the secondary transistor of the first optocoupler OP1 is pulled up to the power supply voltage FVGD+, and the other end is grounded. In addition, in this example, a low-pass filter circuit is connected to the output of the secondary transistor to provide a stable output. In this example, an RC low-pass filter circuit composed of a resistor R11 and a capacitor C1 is shown, and a filtered output is provided at both ends of the capacitor C1. In addition, a resistor R1 can also be connected to both ends of the capacitor C1 to provide a discharge path for the capacitor C1 (the resistor R1 is equivalent to the load of the RC low-pass filter circuit). Those skilled in the art are aware of various low-pass filter circuits, Figure 3 The circuit shown in is only an example.

[0057] A first switching device Q1 (e.g., a PMOSFET) is connected between the power supply voltage FVGD+ and the high-side driver 405H. The filtered output from the secondary side of the first optocoupler OP1 controls the on / off switching of the first switching device Q1. When the first switching device Q1 is on, the power supply voltage FVGD+ is provided to the high-side driver 405H as the power supply VGD. Based on the power supply VGD, the high-side driver 405H outputs a gate drive signal for the high-side IGBT according to a drive control signal, such as a PWM signal, from the motor controller 407.

[0058] The secondary transistor of the second optocoupler OP2 is similarly connected, with one end pulled up to the power supply voltage FVGD+ and the other end grounded. Similarly, a low-pass filter circuit, such as an RC low-pass filter circuit formed by a resistor R22 and a capacitor C2, can be connected to the output of the secondary transistor. Resistor R2 can be connected across capacitor C2 as a load, which will not be further described here.

[0059] A second switching device Q2 (e.g., a PMOSFET) is connected between the power supply voltage FVGD+ and the low-side driver 405L. The filtered output of the secondary side of the second optocoupler OP2 can control the on / off switching of the second switching device Q2. When the second switching device Q2 is on, the power supply voltage FVGD+ is provided to the low-side driver 405L as the power supply VSL. Based on the power supply VSL, the low-side driver 405L can output a gate drive signal for the low-side IGBT according to a drive control signal, such as a PWM signal, from the motor controller 407.

[0060] One end of the secondary side of the third optocoupler OP3 can be connected to the power supply voltage Vcc, and the other end can be grounded via a resistor R3. The output signal of the secondary side of the third optocoupler OP3 (e.g., the voltage at the emitter) is high during normal operation (at which point the motor controller 407 should normally provide a drive control signal), and is low when STO is triggered (e.g., either or both STO1 and STO2 are enabled) (at which point the motor controller 407 does not provide a drive control signal). In other words, the output signal of the secondary side of the third optocoupler OP3 can be the same as the enable logic of the motor controller 407. Therefore, the output signal of the secondary side of the third optocoupler OP3 can be connected to the enable terminal EN of the motor controller 407.

[0061] When STO is triggered (for example, at least one of STO1 and STO2 is enabled), the first optocoupler OP1, the second optocoupler OP2, and the third optocoupler OP3 are all turned off, and their respective secondary transistors are also turned off. In the STO channel where the optocoupler OP1 or OP2 is turned off, capacitor C1 or C2 can discharge through resistor R1 or R2. When the voltage across capacitor C1 or C2 drops below the threshold voltage of switching device Q1 or Q2, switching device Q1 or Q2 is turned off. With switching device Q1 or Q2 turned off, high-side driver 405H or low-side driver 405L will no longer receive power supply VGD or VSL, and will therefore cease operation, thereby shutting down the motor torque. In addition, in the third STO channel where the third optocoupler is located, the secondary side of the third optocoupler is cut off so that its output signal is pulled down to the ground, so that the enable terminal EN of the motor controller 407 can be pulled down to the ground voltage, thereby failing to transmit the drive control signal to the high-side driver 405H and the low-side driver 405L, so that the high-side driver 405H and the low-side driver 405L can stop driving the motor to rotate.

[0062] In this example, in the third STO channel, instead of Figure 2 Instead of using a switching device to control on / off as shown in FIG, the operation of the motor controller 407 itself is controlled by the enable terminal. Of course, the present disclosure is not limited to this. For example, switching devices can be respectively provided between the motor controller 407 and the high-side driver 405H and between the motor controller 407 and the low-side driver 405L, and these switching devices can be controlled according to the output signal of the secondary side of the third optocoupler.

[0063] Figure 4 The figure schematically shows a circuit diagram of a circuit with an STO function according to an embodiment of the present disclosure.

[0064] like Figure 4 As shown, the STO circuit according to this embodiment is a three-STO channel configuration, including a first optocoupler OP1, a second optocoupler OP2, and a third optocoupler OP3. The connections of these optocouplers at the primary and secondary sides are combined with the above Figure 3 The description is the same and will not be repeated here. In addition, similar to the first optocoupler OP1 and the second optocoupler OP2, an RC low-pass filter circuit composed of, for example, a resistor R33 and a capacitor C3 is also provided at the secondary side of the third optocoupler OP3 as described above, and the resistor R3 can be connected to both ends of the capacitor C3 as a load. In addition, with respect to the switching device 509, the motor controller 507, the high-side driver 505H, and the low-side driver 505L, reference can be made to the previous description of the corresponding components.

[0065] In this example, the output signal of the secondary side of the third optocoupler OP3 is not connected to the enable terminal of the motor controller, but instead is connected to a clock generator 511 connected to the motor controller 507. The clock generator 511 can, for example, generate a clock signal CLK based on a crystal oscillator. The motor controller 507 can generate a drive control signal, such as a PWM signal, based on the clock signal CLK. A third switching device Q3 (e.g., a PMOSFET) can be connected between a power supply voltage Vcc (the power supply for the clock generator) and a power supply terminal of the clock generator 511. The filtered output of the secondary side of the third optocoupler OP3 can control the on / off switching of the third switching device Q3. When the third switching device Q3 is on, the power supply voltage Vcc is transmitted to the clock generator 511, enabling the clock generator 511 to operate and generate the clock signal CLK. Conversely, when the third switching device Q3 is off, the clock generator 511 is powered off and cannot generate the clock signal CLK, causing the motor controller 507 to stop providing the drive control signal.

[0066] Combination of the above Figure 3 and Figure 4 Different examples of implementing the three-channel STO function by controlling the operation of the motor controller are described. It is obvious to those skilled in the art that there are many different ways to control the operation of the motor controller.

[0067] Figure 5 The figure schematically shows a circuit diagram of a circuit with an STO function according to an embodiment of the present disclosure.

[0068] like Figure 5 As shown, the STO circuit according to this embodiment is a three-STO channel setting, including a first optocoupler OP1, a second optocoupler OP2 and a third optocoupler OP3. The connection between the first optocoupler OP1 and the second optocoupler OP2 at the primary and secondary sides is combined with the above Figure 3 The description is the same and will not be repeated here. One end of the secondary side of the third optocoupler OP3 is pulled up to the power supply voltage Vcc through the resistor R3, and the other end is grounded. The output signal of the secondary side of the third optocoupler OP3 (e.g., the voltage at the collector) is low during normal operation and high when STO is triggered (e.g., either STO1 or STO2 is enabled). In addition, with respect to the motor controller 607, the high-side driver 605H, and the low-side driver 605L, reference can be made to the previous description of the corresponding components.

[0069] In this example, instead of using a transistor, a transmission gate is used as the third switching device. For example, the first transmission gate 613_a can be connected between the motor controller 607 and the high-side driver 605H, and the second transmission gate 613_b can be connected between the motor controller 607 and the low-side driver 605L. When enabled, the first transmission gate 613_a and the second transmission gate 613_b can transmit the drive control signal generated by the motor controller 607 to the high-side driver 605H and the low-side driver 605L, respectively. The output of the secondary side of the third optocoupler OP3 can be connected to the enable terminal ENB of each of the first transmission gate 613_a and the second transmission gate 613_b. Here, the enable terminal ENB can be active at a low level. When the secondary side of the third optocoupler OP3 is turned on, the enable terminal ENB of each of the first transmission gate 613_a and the second transmission gate 613_b is pulled down to the ground voltage, and is enabled to transmit the drive control signal. On the contrary, when the secondary side of the third optocoupler OP3 is turned off, the enable terminals ENB of the first transmission gate 613_a and the second transmission gate 613_b are pulled up to the power supply voltage Vcc. At this time, the first and second transmission gates are disabled and thus cannot transmit the driving control signal.

[0070] The above Figures 3 to 5 The setting and working principle of three STO channels of the present invention have been described as an example. However, the present invention is not limited to this. For example, the first STO channel and the second STO channel are not necessarily to control high and low side drivers, and the 3rd STO channel is not necessarily to control motor controller. On the contrary, by adaptively adjusting the circuit topology, it is possible to realize that the first STO channel controls low side driver or motor controller, the second STO channel controls high side driver or motor controller, or the 3rd STO channel controls high side or low side driver. In a word, using the "AND" operation of two STO signals as the input signal of another STO channel, and outputting a three-channel scheme that realizes controlling the provision of a drive control signal, all should fall within the scope of the present invention.

[0071] Figure 6 Various circuit diagrams for implementing an “AND” operation of level signals according to an embodiment of the present disclosure are schematically shown.

[0072] like Figure 6 As shown in (a), different types of switching devices such as N-type metal oxide semiconductor (NMOS) transistors can be used to achieve Figure 3 The switching device 409 shown in FIG.

[0073] exist Figure 3 and Figure 6 In the example shown in (a), the switch device is connected to the cathode of the primary side of the third optocoupler OP3. However, the present disclosure is not limited thereto. For example, the switch device may also be connected to the anode of the primary side of the third optocoupler OP3, as shown in FIG. Figure 6 As shown in (b) of FIG3 , the anode of the primary LED of the third optocoupler OP3 can be connected to receive the first STO signal STO1 via a switching device (e.g., an NMOS), and the cathode can be connected to ground. The second STO signal STO2 can be connected to a control terminal for controlling the switching device. In this example, the first STO signal STO1 can also be considered the power supply for the primary LED of the third optocoupler OP3. The primary LED of the third optocoupler OP3 is connected between the power supply STO1 and ground. The switching device (between the power supply STO1 and the anode of the primary LED of the third optocoupler OP3) can turn the circuit containing the primary LED of the third optocoupler OP3 on or off based on the second STO signal STO2.

[0074] Alternatively, instead of using the second STO signal STO2 to directly control the control terminal of the switching device, a gate driver such as Figure 6 As shown in (c), the anode of the primary LED of the third optocoupler OP3 can be connected to receive the first STO signal STO1 through a switching device (e.g., an NMOS), and the cathode can be connected to ground. The second STO signal STO2 can be connected to control a gate driver, which can drive the gate of the switching device. When the second STO signal STO2 is not enabled (e.g., at a high level), the gate driver can operate, driving the switching device to conduct. When the second STO signal STO2 is enabled (e.g., at a low level or open), the gate driver can stop operating, turning the switching device off.

[0075] In the above embodiment, the switching device is implemented by NMOS. However, the present disclosure is not limited thereto. For example, Figure 6 As shown in (d) of FIG. 1 , a P-type metal oxide semiconductor (PMOS) transistor can be used to implement the switching device. Since the driving logic of a PMOS is opposite to that of an NMOS, in this example, the second STO signal STO2 can be driven by, for example, an inverter and a resistor connected between the second STO signal STO2 and the power supply STO1 to drive the PMOS gate. Of course, the circuit for driving a PMOS transistor based on the second STO signal STO2 is not limited to this.

[0076] In the above embodiment, the circuit where the primary LED of the third optical coupler OP3 is located (between the power supply STO1 and the ground) is controlled by a switch device. However, the present disclosure is not limited thereto. For example, Figure 6As shown in (e), a bypass branch can be provided between the first STO signal STO1 (power supply) and ground, connected in parallel with the primary LED of the third optocoupler OP3. The bypass branch can include a switching device, such as a PNP transistor, and the second STO signal STO2 can be connected to a control terminal for controlling the switching device. Here, the second STO signal STO2 can be configured to turn off the switching device when not enabled (e.g., at a high level), thereby allowing the primary LED of the third optocoupler OP3 to operate normally. When enabled (e.g., at a low level or open circuit), the switch device can be connected, short-circuiting the primary LED of the third optocoupler OP3 and ceasing operation.

[0077] In various circuits implementing AND logic, the first STO signal STO1 and the second STO signal STO2 can be interchanged.

[0078] Figure 7 A schematic diagram showing an input portion of a circuit with an STO function according to an embodiment of the present disclosure is shown.

[0079] like Figure 7 As shown, the STO signal can be provided by a power supply PS (for example, a 24V DC power supply). Here, a first switch SW1 and a second switch SW2 are provided to control the input of the first STO signal STO1 and the second STO signal STO2 to the first optocoupler OP1 and the second optocoupler OP2, respectively. In addition, a third switch SW3 is provided to control the grounding of the circuit (in this example, grounding can mean connecting to the negative pole of the power supply PS). The ground terminals of each component in the circuit (for example, the various components described in the above embodiments) can be connected to the ground COM in common. The first switch SW1, the second switch SW2, and the third switch SW3 can be turned on or off together. In this example, three switches are provided to adapt to the three channels. Thus, a three-channel architecture is implemented not only inside the circuit but also at the circuit input, thereby being able to tolerate two faults both inside and outside the circuit while ensuring that the STO function is not lost, greatly improving safety and reliability.

[0080] exist Figure 7 In the figure, for convenience only, the circuit after the AND gate and the optocoupler are not shown. Figure 7 The configuration shown is applicable to the various circuit configurations described above.

[0081] As described above, the circuit with the STO function according to the embodiment of the present disclosure can be applied to an inverter to realize an inverter with higher reliability.

[0082] The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be used in combination to advantage. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A safe torque off (STO) circuit used in a frequency converter, wherein: The frequency converter includes a motor driver and a motor controller, wherein the motor driver includes a high-side driver and a low-side driver for the high-side IGBT and the low-side IGBT respectively. The STO circuit includes: A first optocoupler includes a first primary side and a first secondary side, wherein the first primary side receives a first STO signal, and the first secondary side cuts off power supply to the high-side driver according to the valid first STO signal; a second optocoupler comprising a second primary side and a second secondary side, wherein the second primary side receives a second STO signal, and the second secondary side cuts off power supply to the low-side driver according to a valid second STO signal; a third optocoupler including a third primary side and a third secondary side, wherein the third primary side receives a result of a logic operation of the first STO signal and the second STO signal, and the third secondary side cuts off the provision of the drive control signal of the motor controller according to a valid result of the logic operation; The logic operation is as follows: when at least one of the first STO signal and the second STO signal is valid, the result of the logic operation is also valid.

2. The STO circuit according to claim 1, wherein: The third primary is connected between the first STO signal and ground to form a current path from the first STO signal through the third primary to ground. The circuit further includes a switching device disposed in the current path, wherein a control terminal of the switching device is controlled by the second STO signal.

3. The STO circuit according to claim 2, further comprising: A gate driver is connected to a control terminal of the switching device, wherein the gate driver is controlled to operate by the second STO signal.

4. The STO circuit according to claim 1, wherein: The third primary is connected between the first STO signal and ground to form a current path from the first STO signal through the third primary to ground. The circuit further includes a bypass branch connected in parallel with the current path, wherein the bypass branch is controlled by the second STO signal.

5. The STO circuit according to claim 1, wherein: The output of the third secondary side is connected to the enable terminal of the motor controller.

6. The STO circuit according to claim 1, wherein: The output of the third secondary side is connected to a clock generator that provides a clock signal to the motor controller.

7. The STO circuit according to claim 1 , further comprising: The AND gate composed of discrete components is configured to perform the logic operation.

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