KR100885274B1 - Inverter circuit - Google Patents

Abstract

The present invention provides an inverter circuit including at least one first transistor as a switching element, comprising: a monitor current supply unit providing a monitor current to the first transistor when the first transistor is turned on; The terminal voltage between the terminals conducting in the turned-on state of the first transistor is measured based on the monitor current, and the terminal voltage is compared with a predetermined reference voltage and switched to the switching terminal of the first transistor based on a comparison result. A switching control unit providing a signal; A capacitor having one end connected in series with a branch branched from a node between the switching control unit and the switching terminal to bypass the high frequency component of the switching signal; And a second transistor connected to the other end of the capacitor, switched by the high frequency component, and bypassing the monitor current when turned on.

As such, the inverter circuit according to the embodiment of the present invention may provide a means for estimating the amount of current by a simple indirect method without using an ammeter. Further, by providing a means for supplementing the monitor current from a separate voltage source by supplementing a small amount of current provided by the gate driver IC, a means for further changing the detection level is provided. Accordingly, a plurality of inverter transistors can be controlled by one gate driver IC.

Furthermore, by bypassing the high frequency component and providing a delay time according to the incomplete measurement according to the high frequency component due to the noise of the switching signal, it is possible to provide a means for adjusting the detection time to a time capable of accurate detection. .

Inverter, IGBT

Description

Inverter circuit {INVERTER CIRCUIT}

1 is a circuit diagram of a motor drive device for explaining a conventional three-phase motor control inverter;

2 is a partial circuit diagram of an inverter circuit according to an embodiment of the present invention.

The present invention relates to an inverter circuit, and more particularly, to an inverter circuit that can effectively detect and block the conduction of overcurrent in the turn-on state of a transistor used as a switching element.

An inverter is a device that converts DC power into AC power. As is well known, inverters are used in various fields, but are most commonly used for the control of three-phase motors.

1 is a circuit diagram of a motor driving apparatus for explaining a conventional three-phase motor control inverter.

Referring to Fig. 1, the motor driving apparatus has a three-phase motor 1, an inverter 3, a current detector 5, and a controller 7.

The three-phase motor 1 has a stator 11 and an internal rotor 12 including resistors R1 to R3 and inductors L1 to L3. Each phase terminal of the three-phase motor 1 is connected to the inverter 3, and when an excitation phase current flows and a current flows through the inductors L1 to L3, a magnetic field is formed to rotate the internal rotor 12.

The inverter 3 has six switching transistors Q1 to Q6. Two are connected in series to each of the phase terminals of the three-phase motor 1, one of which is connected to the positive terminal of the external Vdc and the other to the negative terminal.

The excitation phase current supplied from the inverter 3 to the three-phase motor 1 is detected by the current detector 5, and the base terminals of the transistors Q1 to Q6 are switched by a bias signal input from the controller 7. Controlled.

The current detection unit 5 is for measuring the excitation phase current, which provides the basis for the determination by the control unit 7 to determine the initial position of the rotor, whether or not to communicate.

The control unit 7 drives the inverter 3 in accordance with the two-phase excitation method. That is, one of the three upper transistors Q1 to Q3 of the inverter 3 is turned on, and one of the lower transistors Q4 to Q6 having a phase different from the turned on phase is turned on. According to this excitation method, six current directions can be symbolized as shown in Table 1 below.

sign Direction of current IU U-> V IV V-> W IW W-> U -IU V-> U -IV W-> V -IW U-> W

Table 1

Here, the arrow indicates current reflection between the phase terminals U, V, and W. As shown in FIG. For example, "U-> V" means that the excitation current flowing into the U phase terminal of the three-phase motor 1 flows out into the V phase terminal.

The control unit 7 switches the switching transistors Q1 to Q6 of the inverter 3, and selectively switches the transistors Q1 to Q6 of the inverter 3 based on the current detected from the current detection unit 5. do.

However, when abnormal operations such as an arm short occur in the two-phase excitation control scheme, excessive current flows and the transistors Q1 to Q6 may be damaged. If the transistors Q1 to Q6 are damaged, only the transistors need to be replaced. However, since the transistors are fixed to the substrate and modularized, it is not easy to selectively replace the damaged transistors. If one part is enough, even if the finished product or the board must be replaced, customer satisfaction will deteriorate.

Therefore, it is necessary to monitor whether the excessive excessive current flows through the transistor due to the occurrence of a cancer short and actively protect it. However, connecting the ammeters in series for each transistor in the inverter circuit is economically inefficient, and thus, it is necessary to provide a means for effectively performing this.

Also, an overshoot of the signal that occurs momentarily on the rising edge when the switch signal is applied to the transistor at high speed. Due to the high frequency component, the transistor is unstablely turned on, which makes it difficult to check an electrical signal (eg, current, voltage, etc.) and control based thereon.

Accordingly, an object of the present invention is to provide an inverter circuit capable of effectively measuring the current flowing through the switching transistor to protect the device.

In addition, the present invention is to provide an inverter circuit capable of estimating a conduction current of a transistor without being affected by overshoot, high frequency component noise, etc. which may occur when the transistor is turned on, and performing switch control based on the same.

In order to achieve the above object, the present invention provides a monitor current supply unit for providing a monitor current to the first transistor when the first transistor is turned on in an inverter circuit including at least one first transistor as a switching element. ; The terminal voltage between the terminals conducting in the turned-on state of the first transistor is measured based on the monitor current, and the terminal voltage is compared with a predetermined reference voltage and switched to the switching terminal of the first transistor based on a comparison result. A switching control unit providing a signal; A capacitor having one end connected in series with a branch branched from a node between the switching control unit and the switching terminal to bypass the high frequency component of the switching signal; And a second transistor connected to the other end of the capacitor, switched by the high frequency component, and bypassing the monitor current when turned on.

Here, the monitor current supply unit, a current source for providing a constant current; And a voltage source connected in series with a pull-up resistor, wherein the monitor current is supplied from the current source and the voltage source.

The monitor current supply unit may include a diode having a cathode terminal connected to one of the terminals conducting when the first transistor is turned on, and the switching controller measures a voltage of a series node connected to an anode terminal of the diode. It is preferable to estimate the terminal voltage.

In addition, the monitor current is connected to be discharged when the second transistor is turned on, and is charged by a source supplying the monitor current so that the monitor current only when the charging voltage is high by a predetermined voltage with respect to one of the conductive terminals of the first transistor. It is preferable to include a charging capacitor configured to flow.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a partial circuit diagram of an inverter circuit according to an embodiment of the present invention.

Referring to FIG. 2, an inverter circuit according to an embodiment of the present invention may include any one of six transistors (hereinafter, referred to as a “first transistor”) of the inverter circuit disclosed in FIG. 1 and according to an embodiment of the present invention. It consists of a plurality of elements connected thereto. Accordingly, it should be understood that the partial circuit diagram of the inverter circuit disclosed in FIG. 2 may be configured to be equally expanded and repeated for the six transistors disclosed in FIG.

Specifically, the inverter circuit disclosed in FIG. 2 includes the first transistor Q1, the monitor current supply unit 10, the charging capacitors C2 and C3, the switching control unit 20, the bypass capacitor C1, and the second transistor. It is comprised including (Q2).

As described above, the first transistor Q1 corresponds to any of the transistors disclosed in FIG. 1, and its use and operation method are the same as those described in FIG. 1. It will be appreciated that the transistor adopted in this embodiment can be replaced with an Insulated Gate Bipolar Transistor (IGBT) or another type of transistor.

As shown in FIG. 2, the emitter of the first transistor Q1 is connected to a predetermined reference potential terminal, and the collector is connected to the DC voltage source Vcc as shown in FIG. 1 and the monitor current supply unit 10. It is connected together to the connecting branch. In addition, a freewheeling diode Df is connected between the collector and the emitter.

The monitor current supply unit 10 is for supplying a monitor current for estimating a current flowing in the first transistor Q1 in the turn-on state of the first transistor Q1. The current flowing during the turn-on of the first transistor Q1 is estimated by obtaining a terminal voltage between the collector and the emitter of the first transistor Q1, and the collector-emitter terminal voltage may be estimated by measuring the monitor current.

As shown in FIG. 2, the monitor current supply unit 10 includes a current source Is that provides a constant current, a voltage source Vcc connected in series with a pull-up resistor R2, and a cathode terminal of the first transistor Q1. A diode D connected to the collector and a resistor R1 connected to the anode terminal of the diode D are included.

Each current supplied from the current source Is and the voltage source Vcc forms a monitor current, and the monitor current is a resistor R1 and a diode D when the first transistor Q1 is turned on to conduct the collector and emitter. ), The collector of the first transistor Q1, and the emitter are sequentially flowed. It will be appreciated that the specific connection configuration of the monitor current supply unit 10 may be changed somewhat while performing the same function.

The charging capacitors C2 and C3 are connected between the node where the monitor current is formed and the reference potential terminal and connected in parallel to the second transistor Q2 which will be described later.

The charging capacitors C2 and C3 are charged by the current source Is and the voltage source Vcc to a potential capable of supplying a monitor current. That is, when the collector and emitter voltage V _CE of the first transistor Q1 is 2 [V] and the conduction voltage of the diode D is 0.7 [V], the charging capacitors C2 and C3 are about. Charged to 2.7 [V], after which the monitor current begins to be provided. As a result, the supply start time of the monitor current is delayed until the charging capacitors C2 and C3 are charged.

On the other hand, when an arm short occurs and an overcurrent flows, for example, when the current increases from 500 A to 700 A, the collector-emitter voltage V _CE of the first transistor Q1 increases to 7 [V], for example. do. Capacitors C2 and C3 charged to maintain a potential of 2.7 [V] in a normal turn-on state have a potential of 0.7 [V] higher than the collector-emitter voltage V _CE of the first transistor Q1. It is charged again to have a potential of 7.7 [V]. This increasing voltage is input to the switching control unit 20, specifically, the comparator 22, which will be described later, and used to estimate the voltage between the collector and the emitter V _CE of the first transistor Q1, which is the conduction current as described above. It is used to estimate the level of.

The switching controller 20 is for providing a switching signal of the first transistor Q1 and is generally implemented as a gate driver IC. As described above, the driving signal is determined by the initial position of the rotor in the three-phase motor, and the switching signal output from the switching control unit 20 is also changed according to the terminal voltage between the collector and the emitter estimated based on the monitor current. Can be provided.

The operation of this additional switching controller 20 according to an embodiment of the present invention can be implemented using a comparator 22 as a configuration for estimating the collector-emitter terminal voltage as shown in FIG. .

That is, the + terminal of the comparator 22 has a resistor R1 such that a voltage formed when the monitor current flows through the resistor R1 to the reference potential terminal, that is, a holding voltage held by the charging capacitors C2 and C3 is input. And one side of the charging capacitors C2 and C3, and the input voltage is compared with a predetermined reference voltage Vref input to the negative terminal, and the comparison result is output.

The output voltage of the comparator 22 is used as an index indicating whether the collector-emitter terminal voltage is excessive, that is, whether excessive current flows. If it is determined that excessive current flows, the switching control unit 20 may be programmed to stop the output of the switching signal for the first transistor Q1 and to perform any predetermined procedure.

As shown in FIG. 2, the comparator 22, the current source Is, and the like may be included in one gate driver IC, and various connection configurations are possible as well as known for internal configuration connections in the gate driver IC. To be omitted. Since the monitor current supplied by the gate driver IC is insufficient to operate by connecting a large-capacity IGBT in parallel, it is necessary to supplement the monitor current by using a separate voltage source (Vcc) and a pullup resistor as in the embodiment of the present invention. desirable.

Since the IGBT requires a lot of current for the switching signal output from the switching control unit 20, the IGBT may be interposed through the current buffer 30, which may be selectively used according to the type of transistor and its use.

The bypass capacitor C1 bypasses the high frequency component of the switching signal connected to the gate of the first transistor Q1 and input to the gate. Accordingly, the high frequency noise component of the switching signal is prevented from being input to the first transistor Q1, thereby ensuring a stable switching operation of the first transistor Q1.

The second transistor Q2 has its base terminal connected to the bypass capacitor C1 and is switched by a high frequency component that is bypassed. In particular, the collector terminal of the second transistor Q2 is connected to the node where the monitor current is formed, so that the charging charges of the charging capacitors C2 and C3 are changed according to the turn-on of the second transistor Q2. And then to the reference potential stage.

Now, the operation of the inverter circuit shown in Figure 2 and its specific effects will be described in detail.

The switching control unit 20 provides a switching signal to control the transistors of the inverter circuit, that is, the first transistor Q1 of FIG. 2.

However, when there is a high frequency noise in the switching signal provided from the switching control unit 20 or when a high frequency component occurs due to an overshoot that may occur during the transition of the switching signal, the signal component may cause the first transistor Q1. The current is bypassed by the bypass capacitor C1 and input to the base of the second transistor Q2. In this case, the electrical energy charged in the charging capacitors C2 and C3 is discharged through the second transistor Q2 as the second transistor Q2 is turned on.

When the high frequency component disappears and the switching signal is stabilized, the first transistor Q1 is turned on so that the collector and emitter terminals of the first transistor Q1 are conducted so that a current flows.

Meanwhile, as the high frequency component disappears, the second transistor Q2 is turned off, and the charging capacitors C2 and C3 start to be charged again by the current source Is and the voltage source Vcc. The charge amount is determined by the potential between the sustain voltage of the capacitor and the collector terminal voltage of the first transistor Q1.

In other words, when the conduction potential of the diode D is 0.7 [V], the monitor current is maintained until the charging capacitors C2 and C3 are charged to a potential that is at least about 0.7 [V] greater than the potential of the collector terminal. It cannot flow to the collector terminal of transistor Q1.

Therefore, even if the first transistor Q1 is turned on at the same time as the second transistor Q2, the measurement time of the terminal voltage by the comparator 22 is delayed slightly, thereby making it possible to avoid an incomplete measurement operation. That is, the measurement time of the terminal voltage can be adjusted by the time constants of the charging capacitors C2 and C3.

In this normal state, when a short circuit occurs and a large amount of current flows in the first transistor Q1, the collector terminal voltage increases, and thus the monitor current cannot flow any more. That is, the monitor current cannot naturally flow unless the holding voltage of the charging capacitors C2 and C3 increases by 0.7 [V] following the terminal voltage of the first transistor Q1.

Therefore, the electrical energy supplied from the current source Is and the voltage source Vcc is not supplied to the monitor current, but instead starts charging the charging capacitors C2 and C3. Charging proceeds until the potential of the charging capacitors C2 and C3 becomes at least about 0.7 [V] greater than the potential of the collector terminal, which is input to the + terminal of the comparator 22.

For example, when a current of 200 [A] is supplied and a current of 700 [A] flows due to an arm short, and the collector terminal voltage increases from 2 [V] to 7 [V], the charging capacitor C2, The holding voltage held by C3) must be increased from 2.7 [V] to 7.7 [V] so that the monitor current can flow to the first transistor.

The comparator 22 continuously compares the input voltage of the + terminal with a reference voltage Vref, for example, 3.5 [V], which is an allowable predetermined level, and the holding voltages of the charging capacitors C2 and C3 are converted into transient currents. Increase the sign of the output voltage when it exceeds 3.5 [V].

In response to the change in the output voltage, the switching controller 20 may protect the transistor by adjusting switching control of the transistor Q1 through which excessive current flows.

As such, the inverter circuit according to the embodiment of the present invention may provide a means for estimating the amount of current by a simple indirect method without using an ammeter. In addition, as shown in FIG. 2, a large capacity IGBT connected in parallel to one gate drive IC by providing a means for supplementing a small amount of current provided by the gate driver IC to supplement the monitor current from a separate voltage source (Vcc). Such transistors can be controlled.

In addition, it is possible to provide a means for adjusting the detection time by bypassing the high frequency component and providing a delay time according to the incomplete measurement according to the high frequency component due to the noise of the switching signal.

Although some embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that modifications may be made to the embodiment without departing from the spirit or spirit of the invention. . It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

According to the present invention, an inverter circuit capable of protecting the device by effectively measuring the current flowing through the switching transistor is provided. In addition, there is provided an inverter circuit capable of estimating a conduction current of a transistor without being influenced by overshoot, noise of high frequency components, etc., which may occur when the transistor is turned on, and performing switch control on the basis thereof.

Claims (5)

An inverter circuit comprising at least one first transistor as a switching element, A monitor current supply unit configured to provide a monitor current to the first transistor when the first transistor is turned on; The terminal voltage between the terminals conducting in the turned-on state of the first transistor is measured based on the monitor current, and the terminal voltage is compared with a predetermined reference voltage and switched to the switching terminal of the first transistor based on a comparison result. A switching control unit providing a signal; A capacitor having one end connected in series with a branch branched from a node between the switching control unit and the switching terminal to bypass the high frequency component of the switching signal; And And a second transistor connected to the other end of the capacitor and switched by the high frequency component and configured to bypass the monitor current when turned on. The method of claim 1, The monitor current supply unit, A current source for providing a constant current; A voltage source connected in series with the pullup resistor, And the monitor current is supplied from the current source and the voltage source. The method according to claim 1 or 2, And the monitor current supply unit includes a diode having a cathode terminal connected to one of the terminals that are turned on when the first transistor is turned on. The method of claim 3, The switching controller measures the terminal voltage by measuring the voltage of the series node connected to the anode terminal of the diode. delete

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