KR102635649B1 - Optional Snubber Circuit - Google Patents

Abstract

The selective snubber circuit of the present invention forms a current path parallel to the switch element constituting the inverter for driving the motor, and includes a snubber resistor and a snubber capacitor connected in series with each other; A snubber interruption switch that switches the current path of the snubber resistor and the snubber capacitor; And it may include a controller that turns off the snubber intermittent switch when the inverter for driving the motor is in a 0 torque control state.

Description

Optional Snubber Circuit {Optional Snubber Circuit}

The present invention relates to a selective snubber circuit that determines the operation of the snubber circuit according to the driving conditions of the inverter.

Figure 1 is a circuit diagram showing a snubber circuit fixedly connected to an inverter power switch according to the prior art.

FIG. 2 is a waveform diagram showing the operation of the snubber circuit according to on/off of the inverter power switch 10 of FIG. 1.

A snubber circuit is used in addition to an inverter circuit for the purpose of blocking surges caused by sudden voltage increases and eliminating ringing phenomenon during the switching operation of the power switch 10.

In the T4200 OFF section of FIG. 2, a current as shown by the downward arrow in FIG. 1 flows, and the stirrer capacitor is charged, and in the T4200 ON section, a current as shown by the upward arrow flows, and the stirrer capacitor is discharged.

Figure 3 is a graph showing the occurrence of temperature difference depending on the presence/absence of a snubber in the circuit of Figure 1.

When a snubber circuit is applied, while it has a positive function of eliminating switching surges and noise, it also has a negative function of reducing heat generation and efficiency by R(12) among the elements 12 and 14 made up of RC series. do.

In particular, the drive shaft is rotating due to the vehicle's coasting, but in the zero torque state, which is the stage immediately before driving the motor, current does not flow to the motor coil, and the inverter controller generates the most heat. However, even though the motor is not driven due to the connected snubber circuit, the temperature of the inverter controller rises, degrading motor performance, and the performance of the product also deteriorates.

In other words, the RC snubber causes the temperature of the controller and elements to rise, reducing efficiency, and in the 0 torque control section, current does not flow to the motor coil, so heat circulates only inside the inverter. In the case of Figure 3, the presence/absence of the snubber Accordingly, it can be seen that a temperature difference of about 9 degrees occurs.

Republic of Korea Registration Publication No. 10-0333089

The present invention seeks to provide a selective snubber circuit that improves the thermal efficiency of inverter control by selectively controlling the current flow of the RC snubber.

The selective snubber circuit according to one aspect of the present invention forms a current path parallel to the switch element constituting the inverter for driving the motor, and includes a snubber resistor and a snubber capacitor connected in series with each other; A snubber interruption switch that switches the current path of the snubber resistor and the snubber capacitor; And it may include a controller that turns off the snubber intermittent switch when the inverter for driving the motor is in a 0 torque control state.

Here, when the controller receives a 0 torque command from the vehicle's VCU, it can determine a 0 torque control situation.

Here, one end of the snubber capacitor is connected to the source terminal of the inverter switch element, the other end is connected to one end of the snubber resistor, and one end of the snubber interrupt switch is connected to the other end of the snubber resistor, The other end may be connected to the drain terminal of the inverter switch element.

here,

The snubber intermittent switch may have a source connected to the other end of the snubber resistor, a drain connected to the drain terminal of the inverter switch element, and an on/off indication signal of the controller may be applied to the gate.

Here, the inverter switch element is a MOSFET, and the snubber interrupt switch may be a MOSFET of the same type or made of the same material as the inverter switch element.

The selective snubber circuit according to another aspect of the present invention forms a current path parallel to the switch element constituting the inverter for driving the motor, and includes a snubber resistor and a snubber capacitor connected in series with each other; A snubber bypass switch that forms a bypass path with respect to the current path of the snubber resistor and the snubber capacitor or the current path of the snubber resistor; And it may include a controller that turns on the snubber bypass switch when the inverter for driving the motor is in a 0 torque control situation.

Here, when the controller receives a 0 torque command from the vehicle's VCU, it can determine a 0 torque control situation.

Here, one end of the snubber capacitor is connected to the source terminal of the inverter switch element, the other end is connected to one end of the snubber resistor, and one end of the snubber bypass switch is connected to the other end of the snubber resistor. , the other end may be connected to the drain terminal of the inverter switch element.

Here, the snubber bypass switch has a source connected to the other end of the snubber resistor, a drain connected to the drain terminal of the inverter switch element, and an on/off instruction signal of the controller may be applied to the gate. .

Here, the inverter switch element is a MOSFET, and the snubber bypass switch may be a MOSFET of the same type or made of the same material as the inverter switch element.

If the selective snubber circuit according to the spirit of the present invention of the above-described configuration is implemented, there is an advantage of improving thermal efficiency by selectively controlling the current flow of the RC snubber with a switch (FET).

The selective snubber circuit of the present invention has the advantage of improving product performance by improving the thermal efficiency of a motor driving device such as an inverter for driving a motor.

Figure 1 is a circuit diagram showing a snubber circuit fixedly connected to an inverter power switch according to the prior art.
FIG. 2 is a waveform diagram showing the operation of the snubber circuit according to on/off of the inverter power switch of FIG. 1.
Figure 3 is a graph showing the occurrence of temperature difference depending on the presence/absence of a snubber in the circuit of Figure 1.
Figure 4 is an equivalent circuit diagram of a DC motor to explain torque control of an inverter.
Figure 5 is a circuit diagram illustrating a commonly used H-bridge inverter.
Figure 6 is a circuit diagram showing an embodiment of a selective snubber circuit according to the spirit of the present invention.
FIG. 7 is a flowchart showing an operating mechanism by the selective snubber circuit of FIG. 6.
Figure 8 is a circuit diagram showing another embodiment of a selective snubber circuit according to the spirit of the present invention.

In describing the present invention, terms such as first and second may be used to describe various components, but the components may not be limited by the terms. Terms are intended only to distinguish one component from another. For example, a first component may be referred to as a second component, and similarly, the second component may be referred to as a first component without departing from the scope of the present invention.

When a component is mentioned as being connected or connected to another component, it can be understood that it may be directly connected to or connected to the other component, but other components may exist in between. .

The terms used herein are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions may include plural expressions, unless the context clearly indicates otherwise.

In this specification, terms such as include or have are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, including one or more other features or numbers, It can be understood that the existence or addition possibility of steps, operations, components, parts, or combinations thereof is not excluded in advance.

Additionally, the shapes and sizes of elements in the drawings may be exaggerated for clearer explanation.

First, let's look at the zero torque situation of the inverter, which is of interest to the selective snubber circuit according to the spirit of the present invention.

Figure 4 is an equivalent circuit diagram of a DC motor to explain torque control of an inverter.

Figure 5 is a circuit diagram illustrating a commonly used H-bridge inverter.

Zero torque control means that the vehicle's driving control device (generally a VCU) controls the motor's torque to output 0Nm when the vehicle coasts without driving force with potential energy due to inertia or slope gradient.

0 The reasons why torque control is necessary are as follows.

When the vehicle drive motor rotates, back electromotive force is generated in proportion to the rotation speed, as shown in Equation 1 below.

At this time, if the motor rotates quickly due to other force without controlling the inverter, the energy of the large back electromotive force may burn out the device. Therefore, a closed loop is formed through inverter control (0Nm control) to perform zero torque control to prevent damage to the device due to back electromotive force when the motor rotates.

However, as seen above, if a snubber circuit is provided to block surges caused by rapid voltage rises during the switching operation of the power switch and to eliminate the ringing phenomenon, the snubber resistance during the above-described zero torque control A significant level of heat is generated.

Figure 6 is a circuit diagram showing an embodiment of a selective stirrer circuit that prevents heat generation during zero torque control according to the spirit of the present invention.

The illustrated selective snubber circuit forms a current path parallel to the switch element 10 constituting the inverter for driving the motor, and includes a snubber resistor 120 and a snubber capacitor 140 connected in series with each other; A snubber intermittent switch 160 that switches the current path of the snubber resistor 120 and the snubber capacitor 140; And it may include a controller 200 that turns off the snubber control switch 160 when the inverter for driving the motor is in a 0 torque control state.

Generally, CPUs related to the driving of an electric vehicle include the vehicle's Motor Control Unit (MCU), Transmission Control Unit (TCU), Electronic Control Unit (ECU), and Vehicle Control Unit (VCU). The controller 200 generally determines a 0 torque control situation when it receives a 0 torque command from the vehicle's VCU among the above-described CPUs. However, in other implementations, a 0 torque command may be received from another CPU.

Looking at the illustrated circuit diagram in detail, one end of the snubber capacitor 140 is connected to the source terminal of the inverter switch element 10, the other end is connected to one end of the snubber resistor 120, and the snubber capacitor 140 is connected to the source terminal of the inverter switch element 10. It can be seen that the source as one end of the interrupt switch 160 is connected to the other end of the snubber resistor 120, and the drain as the other end is connected to the drain terminal of the inverter switch element 10.

That is, the snubber intermittent switch 160 shown has a source connected to the other end of the snubber resistor 120, a drain connected to the drain terminal of the inverter switch element 10, and a gate connected to the controller ( It is implemented as a MOSFET to which an on/off indication signal (200) is applied.

In general, MOSFET switches are widely used as power devices in inverters. When the snubber interrupt switch 160 is implemented as a MOSFET, the same type (N or P) and/or the same material (GaAs, GaN, Si-based material, etc.) as the corresponding inverter switch element 10 can be adopted. . In this case, there is an advantage that on/off can be controlled (timing control) in the same way with similar noise characteristics and switching characteristics.

FIG. 7 is a flowchart showing the operating mechanism of the selective stubber circuit of FIG. 6.

The process shown in the flowchart is performed by the controller 200, and since it is a relatively simple task, the controller 200 can be implemented with a programmed microcomputer.

As shown, the controller 200 checks whether zero torque control is performed according to an instruction output from the vehicle's VCU, etc. (S20); If it is a 0 torque control situation, turning off the snubber control switch 160 (S40) to block the current flow to the RC snubber path (S45); And if it is not a 0 torque control situation, the step of turning on the snubber control switch 160 (S40) and maintaining the current flow to the RC snubber path (S45) can be performed. Accordingly, heat generation is limited by turning off the snubber control switch 160 as an RC snubber switch only during zero torque control for the inverter, but switching performance through the RC snubber is maintained when rotating in normal mode instead of zero torque control. It can be improved.

This is due to installing a snubber intermittent switch 160 on the RC snubber, turning it OFF at a certain stage to block the current flowing to the RC snubber, and turning the RC snubber switch ON at the motor driving stage to improve switching characteristics. do.

Figure 8 is a circuit diagram showing another embodiment of a selective snubber circuit according to the spirit of the present invention.

The illustrated selective snubber circuit forms a current path parallel to the switch element 10 constituting the inverter for driving the motor, and includes a snubber resistor 120 and a snubber capacitor 140 connected in series with each other; A snubber bypass switch 162 that forms a bypass path with respect to the current path of the snubber resistor 120 and the snubber capacitor 140 or the current path of the snubber resistor 120; And it may include a controller 202 that turns on the snubber bypass switch 162 when the inverter for driving the motor is in a 0 torque control state.

When the controller 202 receives a 0 torque command from the VCU of the vehicle, it determines a 0 torque control situation as in the case of FIG. 6, but in the case of a 0 torque control situation, the snubber bypass switch 162 is turned on. There is a difference in ordering.

Depending on implementation, the snubber bypass switch 162 may be connected in parallel with the snubber resistor 120 and the snubber capacitor 140, or may be connected in parallel with the snubber resistor 120. Figure 8 shows the former case.

In the former case, there is an advantage in suppressing heat generated by the RC snubber more effectively, but there is a disadvantage in that more attention is required for control because a short path is formed. In the latter case, the direct current path is blocked by the snubber capacitor 140, which has the advantage of making control easier, but has the disadvantage of having a risk of side effects caused by the snubber capacitor 140.

One end of the illustrated snubber capacitor 140 is connected to the source terminal of the inverter switch element 10, the other end is connected to one end of the snubber resistor 120, and the snubber bypass switch 162 One end of is connected to the other end of the snubber resistor 120, and the other end is connected to the drain terminal of the inverter switch element 10.

Specifically, the snubber bypass switch 162 has a source connected to the other end of the snubber resistor 120, a drain connected to the drain terminal of the inverter switch element 10, and a gate of the controller. It can be seen that it is implemented as a MOSFET to which the on/off indication signal is applied.

At this time, when the inverter switch element 10 is a MOSFET, the snubber control switch 162 may be a MOSFET of the same type or made of the same material as the inverter switch element.

Those skilled in the art to which the present invention pertains should understand that the present invention can be implemented in other specific forms without changing its technical idea or essential features, and that the embodiments described above are illustrative in all respects and not restrictive. Just do it. The scope of the present invention is indicated by the claims described later rather than the detailed description, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. .

10: Inverter switch element
120: Snubber resistance
140: snubber capacitor
160: Snubber disconnect switch
162: Snubber bypass switch
200, 202: Controller

Claims (10)

A snubber resistor and a snubber capacitor that form a current path parallel to the switch element constituting the motor driving inverter and are connected in series with each other;
A snubber interruption switch that switches the current path of the snubber resistor and the snubber capacitor; and
A controller that turns off the snubber intermittent switch when the inverter for driving the motor is in a 0 torque control situation.
Optional snubber circuit including.
According to paragraph 1,
The controller is,
An optional snubber circuit that determines a 0 torque control situation when a 0 torque command is received from the vehicle's VCU.
According to paragraph 1,
One end of the snubber capacitor is connected to the source terminal of the inverter switch element, and the other end is connected to one end of the snubber resistor,
A selective snubber circuit in which one end of the snubber interrupt switch is connected to the other end of the snubber resistor, and the other end is connected to the drain terminal of the inverter switch element.
According to paragraph 3,
The snubber intermittent switch is a selective snubber whose source is connected to the other end of the snubber resistor, whose drain is connected to the drain terminal of the inverter switch element, and which is a MOSFET to which the on/off indication signal of the controller is applied to the gate. Circuit.
According to paragraph 3,
The inverter switch element is a MOSFET,
The snubber intermittent switch is a selective snubber circuit that is a MOSFET of the same type or material as the inverter switch element.
A snubber resistor and a snubber capacitor that form a current path parallel to the switch element constituting the motor driving inverter and are connected in series with each other;
a snubber bypass switch that forms a bypass path with respect to the current path of the snubber resistor and the snubber capacitor or the current path of the snubber resistor; and
A controller that turns on the snubber bypass switch when the inverter for driving the motor is in a 0 torque control situation.
Optional snubber circuit including.
According to clause 6,
The controller is,
An optional snubber circuit that determines a 0 torque control situation when a 0 torque command is received from the vehicle's VCU.
According to clause 6,
One end of the snubber capacitor is connected to the source terminal of the inverter switch element, and the other end is connected to one end of the snubber resistor,
A selective snubber circuit in which one end of the snubber bypass switch is connected to the other end of the snubber resistor, and the other end is connected to the drain terminal of the inverter switch element.
According to clause 8,
The snubber bypass switch is a selective switch whose source is connected to the other end of the snubber resistor, whose drain is connected to the drain terminal of the inverter switch element, and which is a MOSFET to which the on/off indication signal of the controller is applied to the gate. Nubber circuit.
According to clause 8,
The inverter switch element is a MOSFET,
The snubber bypass switch is a selective snubber circuit that is a MOSFET adopting the same type or material as the inverter switch element.

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