WO2010149432A2

WO2010149432A2 - Method for controlling a reverse-conducting igbt

Info

Publication number: WO2010149432A2
Application number: PCT/EP2010/056687
Authority: WO
Inventors: Hans-Günter ECKEL; Mark-Matthias Bakran
Original assignee: Siemens Aktiengesellschaft
Priority date: 2009-06-26
Filing date: 2010-05-17
Publication date: 2010-12-29
Also published as: WO2010149432A3; DE102009030739A1

Abstract

The invention relates to a method and a device for controlling a reverse-conducting IGBT (T1, T2). A measurement voltage (u_M) is determined from a measured collector-emitter voltage (U_CE) of an RC-IGBT (T1, T2) to be controlled. The reverse-conducting IGBT (T1, T2) is controlled depending on the polarity sign of the determined measurement voltage (u_M) and a state of a target control signal (S*_T ₁, S*_T ₂) if the polarity sign is positive and the target control signal( S*_T ₁, S*_T ₂) is in the "ON" state. The invention provides a method for controlling a reverse-conducting IGBT (T1, T2) without directly measuring an initial current of a bridge branch having two reverse-conducting IGBTs (T1, T2) connected in series.

Description

Method for controlling a reverse conducting IGBT

The invention relates to a method and a device for controlling a reverse conducting IGBT.

Backward conducting IGBTs are also known as Reverse Conducting IGBTs (RC-IGBTs). These RC-IGBTs are a further development of the known reverse blocking IGBTs. An RC-IGBT differs from a conventional IGBT in that the diode function and the IGBT function are combined in one chip. This creates a power semiconductor in which the anode efficiency in the diode mode is dependent on the gate voltage. This requires a change in the drive over a conventional IGBT.

In addition, there are advantages in the forward voltage, the thermal behavior and the surge current resistance. As a result, such a power semiconductor, which has the same silicon area as a conventional IGBT, has a higher power, whereby a voltage source inverter with a higher power can be realized. In the publication "A High Current 3300V Module Employing Repeating Conducting IGBT's Setting a New Benchmark in Output Power Capability" by M. Rahimo, U. Schlapbach, A. Kopta, J. Vobecky, D. Schneider and A. Baschnagel in ISPSD 2008, a high current 3300V RC IGBT module is presented. This publication also describes a commutation method from a reverse mode IGBT operated in diode mode to a backward conductive IGBT operating in IGBT mode, which form a communications circuit.

In a bridge branch of a voltage source inverter having two conventional IGBTs, these backward-blocking IGBTs are each connected in anti-parallel with one diode. These two conventional IGBTs of a bridge branches are controlled in such a way that during a transition from one state to another state, both IGBTs are switched off for a short time. The control of these two conventional IGBTs of a bridge branch is independent of the sign of an output current. For both current directions, two semiconductors are available, which can carry an output current.

If reverse-conducting IGBTs are used instead of reverse-blocking IGBTs in a voltage intermediate-circuit converter, in particular in a load-side pulse-controlled converter, this known driving method is not very advantageous. As already mentioned, a reverse conducting IGBT in a diode mode, i. a negative collector current flows, or in an IGBT mode, i. it flows a positive collector current, operated. When the gate-emitter voltage of a reverse conducting IGBT is above its threshold voltage while the current flows from the emitter to the collector (negative collector current), i. this RC-IGBT is operated in diode mode, the anode efficiency is lowered, whereby the forward voltage is increased. That is, to determine in which mode the RC-IGBT is located, an output current of a bridge branch of a voltage source inverter must be measured.

As is known, a current measurement is always associated with a certain tolerance. A state switching exactly at zero current is therefore hardly feasible. Since an IGBT mode (positive collector-emitter current) is not possible when the gate is switched off, a diode mode (negative collector-emitter current) is possible with increased gate losses when the gate is on, but for a positive collector-emitter current. Current the associated gate must be switched on in any case.

If the sign of a bridge output current for the generation of drive signals of two electrical in series When switching backward conductive IGBTs used, this changes an interface between the controller and power section of the inverter, ie conventional IGBTs of a load-side pulse-controlled converter of a voltage source inverter can not be easily replaced by backward-conducting IGBTs.

The invention is based on the object of specifying a driving method and a drive device, without having to modify an interface between the controller and a semiconductor-near drive.

This object is achieved on the one hand with the features of claim 1 and on the other hand with the characterizing features of claim 3 according to the invention.

Characterized in that, according to the invention, a sign of a continuously measured collector-emitter voltage of a reverse-conducting IGBT to be controlled and a desired state of this reverse-conducting IGBT are used to generate a drive signal, the control takes place without direct measurement of a current. As a result, no additional signal from the power semiconductor to the controller must be transmitted, whereby the interface between the power unit and control of a load-side pulse converter of a voltage source inverter remains unchanged.

Since, according to the invention, an output current of a bridge branch of an inverter is not measured, but a collector-emitter voltage of a reverse-conducting IGBT to be controlled, this voltage measurement and its evaluation can be accommodated with respect to its sign on a drive device close to the semiconductor. For voltage measurement, a voltage divider is electrically connected in parallel to the collector-emitter path of a reverse-conducting IGBT, the output of which is linked by means of an evaluation device to the driver circuit of a backward-conducting IGBT. Advantageous embodiments of the device according to the invention can be found in the subclaims 5 to 14.

To further explain the invention, reference is made to the drawings, in which several embodiments of a device according to the invention for driving a backward conductive IGBT are illustrated schematically, implementing the inventive method.

1 shows a bridge branch with two RC-IGBTs and a DC voltage source of a voltage source converter, the

2 shows a block diagram of a control of a pulse-controlled converter of a voltage intermediate circuit

Inverter with semi-conductor drive devices of two RC-IGBTs of a bridge branch according to FIG

3 is a block diagram of a first embodiment of a device for controlling an RC

Illustrated in the IGBTs according to the invention, wherein in FIG 4, a characteristic of a voltage divider of

5 shows a block diagram of a second embodiment of a device for controlling an RC-IGBT according to the invention, wherein in the

6 shows a characteristic of a voltage divider of the device according to FIG. 5, and FIGS. 7 and 8 each show a block diagram of a variant of the second embodiment of the drive device according to FIG.

2 shows a bridge branch, with 4 a DC voltage source, 6 a positive bus bar and 8 a negative bus bar. By means of these two bus bars 6 and 8, the bridge branch 2 and the DC voltage source 4 are electrically connected in parallel. The bridge Branch 2 has two reverse-conducting IGBTs Tl and T2, which are electrically connected in series. A connection point of these two reverse-conducting IGBTs Tl and T2 form an AC-side output A, to which a load can be connected. The DC voltage source has two capacitors 10 and 12, which are also electrically connected in series. A connection point of these two capacitors 10 and 12 forms a midpoint connection M. At these two electrically connected in series capacitors 10 and 12 is a DC voltage U _d . Alternatively, instead of the two capacitors 10 and 12, only one capacitor can be used, which is arranged between the busbars 6 and 8. The center M is then not accessible. In a voltage source inverter this DC voltage source 4 forms a voltage intermediate circuit, wherein the pending DC voltage U _{d is} referred to as Zwischenkreisspan- voltage. The bridge branch 2 is three times in a three-phase pulse converter of a voltage source inverter. At the AC-side output A is relative to the center port M of

DC voltage source 4 a pulse width modulated square wave voltage U _AM .

2 shows a block diagram of a controller 16 of a three-phase power converter, in particular a pulse converter, a voltage source inverter, with associated semiconductor driver devices 14 of a bridge branch 2 of this three-phase converter. The controller 16 generates two target control signals S _τ ^* _ι , S _τ ^* ₂ and S _τ ^* ₃ , S _τ ^* ₄ and S _T ^* _5, respectively, depending on a setpoint value, for example a speed setpoint value n *, per bridge branch 2 and S _τ ^* ₆ . For the sake of clarity, only one bridge branch 2 is represented by the three bridge branches of a three-phase power converter. The two desired control signals S ₁ , S ₂ are each fed to a semiconductor-near drive device 14 of each reverse-conducting IGBT T ₁ and T 2 of the bridge branch 2. The output side is in each case an actual control signal Sn or S _τ2 , with a gate of an associated backward conductive IGBTs Tl or T2 is driven. In this illustration, the AC-side output is not designated as in FIG 1 with A but with R. The two further bridge branches, each with an AC-side output of a three-phase converter, are not explicitly shown. These three bridge branches are electrically connected in parallel with the DC voltage source 4, which forms the voltage intermediate circuit of a voltage intermediate-circuit converter.

3 is a schematic diagram of a first embodiment of a semiconductor-near drive device 14 with associated reverse-conducting IGBT T1 according to the invention. This semiconductor-near drive device 14 has a voltage divider 24, an evaluation device 18 and a driver circuit 20. The voltage divider 24 is electrically connected in parallel with the collector-emitter path of the reverse conducting IGBT Tl. An output terminal 22 of the voltage divider 24 is connected to an input terminal 26 of the evaluation device 18. On the output side, this evaluation device 18 is connected to an input of the driver circuit 20, which is connected on the output side to the gate of the RC-IGBTs T1. The voltage divider 24 consists of a series circuit of three resistors Rl, R2 and R3 or in general three impedances. The connection point of the two resistors Rl and R2 form the output terminal 22 of the voltage divider 24. At the connection point of the two resistors R2 and R3 two diodes 28 and 30 are connected, the diode 28 on the anode side and the diode 30 are connected to the cathode side with this connection point. At the collector terminal of the diode 28 and at the anode terminal of the diode 30 is in each case a terminal voltage U _da mp referred to the potential of the emitter of the RC-IGBTs Tl, which is also referred to as Brenzungsspannung on. The potential of the emitter of the RC-IGBT T1 is also referred to as the reference potential of the semiconductor-near drive device 14. By this wiring, the voltage divider 24 receives a limited measuring range on both sides. At the output At the end 22, a determined measuring voltage u _{M is applied} , which is fed to the downstream evaluation device 18. In addition to the desired control signal S _{f1 of} the associated RC-IGBT T 1, this evaluation device 18 is also supplied with a reference voltage u _R. This evaluation device 18 generates an actual control signal S _T i for the reverse-conducting IGBT T1 in dependence on a sign of the determined measurement voltage u _M and the desired control signal S _τ ^* _ι . With this driver circuit 20, this actual control signal S becomes _T i generates a gate voltage. In order to determine the sign of the determined measuring voltage u _M ZU, the reference voltage u _{R is} used. This reference voltage u _R has, for example, the value OV. The determined measuring voltage u _M is checked to see whether it is greater or smaller than the predetermined reference voltage u _R. The result is the sign of the determined measuring voltage u _M. The switching state of the actual control signal S _T i of the reverse-conducting IGBT T 1 to be controlled is determined as a function of the switching state of the associated desired control signal S _n ^* and of the determined sign of the determined measuring voltage u _M. For this purpose, the evaluation device 18 has a state table in which the switching states of a desired control signal S _τ ^* _x , an actual control signal S _T χ, with X = I, ..., n, and the sign of a determined Measuring voltage U _{M are} deposited.

As the first embodiment of the drive device according to the invention can be seen, the measurement of the collector-emitter voltage U _CE of the to be controlled backward conductive IGBTs Tl on the semiconductor drive device 14 is carried out in many cases, this collector-emitter voltage U _CE For example, for short-circuit protection or for active clamping of the collector-emitter voltage U _{CE, the} measurement of the collector-emitter voltage U _CE must have a positive value of a few volts from a negative value of a few volts can distinguish. The measurement is facilitated by a voltage range -0, 7V <U _CE <+0, 7V for the collector-emitter voltage U _CE only at such small currents occurs that it can be assumed that the current in this voltage range is approximately zero.

The value of the maximum positive collector-emitter voltage U _CE will approximately correspond to the value of the reverse voltage of the RC-IGBT Tl. As a result, the value of the maximum collector-emitter voltage U _CE is larger than the value of a forward voltage of this RC-IGBT T1 by more than two orders of magnitude. Thus, the requirements for resolution and accuracy of the collector-emitter voltage measurement are high. By limiting the measuring range of the voltage divider 24, the magnification is increased, which simplifies the sufficiently accurate measurement of the forward voltage. Since only the sign of a determined measuring voltage u _{M is} required for the generation of an actual control signal S _T i, the limitation of the measuring range is permissible.

FIG. 4 shows a characteristic curve of the voltage divider 24, which has a measuring range bounding on both sides. The limit value is determined as a function of the resistances R 1, R 2 and R 3 of the voltage divider 24 and a supplied clamping voltage u _c i _a mp. The positive terminal and the negative voltage input Udamp terminal voltage u i _c _a m p can also have un ^¬ terschiedliche values.

FIG. 5 illustrates a basic circuit diagram of a semiconductor-near control device 14 which has a voltage divider 32 which has an asymmetrically limited measuring range. Opposite the voltage divider 24 of FIG 3 has been dispensed with the voltage divider 32 to the diode 30. An associated characteristic curve is shown in FIG.

In contrast to this embodiment, the asymmetrically limited voltage divider 32 is provided instead of a diode 28 with a Zener diode 34, the cathode side with the connection point of the two resistors R2 and R3 and on the anode side with the emitter terminal E of the backward conductive IGBT Tl is electrically connected. The zener voltage u _{z of} this zener diode 34 determines the value of the asymmetric limit.

8 shows a block diagram of a further variant of the semiconductor-near drive device 14 is shown. This variant differs from the variant according to FIGS. 5 and 7 in that, instead of a voltage divider 32 bounded on one side, a decoupling circuit 36 is provided. This uncoupling circuit 36 has at least one high-voltage diode 38. If several high-voltage diodes 38 are used, they are electrically connected in series. In addition, this uncoupling circuit 36 has a voltage source 40 with series resistor 42 and a voltage divider 44, consisting of the resistors Rl and R2, on. The connection point of these two resistors R1 and R2 forms an output terminal 22 of the disconnection circuit 32. Alternatively, instead of the voltage source 40 with the series resistor 42, a current source can also be used. The voltage divider 44 is electrically connected in parallel with the series connection of the voltage source 40 and the series resistor 42 or electrically in parallel with a current source. This parallel connection and the high-voltage diode 38 are electrically connected in series. The voltage divider 44, which in this embodiment has two ohmic resistances R 1 and R 2, can also be designed as a capacitive or ohmic-capacitive voltage divider.

All embodiments of the semiconductor-near drive device 14 have in common that, depending on the switching state of a desired control signal S _n and a sign of a determined measurement voltage u _M, an actual control signal S _T i is generated semi-conductor close. In general, in the switching state "ON" of the setpoint control signal S _n and a positive measuring voltage u _M, the actual control signal S _T i has the switching state "ON". If, however, the sign of the determined measuring voltage u _{M is} negative, then the actual control signal S _T i has the switching state "OFF". Is the desired control signal S _n in the switching state "OFF", so is the actual control signal S _T i, regardless of the sign of the determined measurement voltage u _M also in the switching state "OFF".

Since the sign of an output current of a bridge branch 2 of two reverse-conducting IGBTs Tl and T2 is determined with the aid of a determined measurement voltage u _{M in the} device according to the invention for driving a reverse-conducting IGBT, this device according to the invention is part of the semiconductor-near drive device 14 one each reverse conducting IGBT Tl or T2. A current flowing through a backward-conducting IGBT T1 or T2 of two RC-IGBTs T1 and T2 connected electrically in series is thus not measured directly, as a result of which the interface between the control 16 and the drive device 14 close to the semiconductor remains unchanged.

Claims

claims

1. A method for driving a backward conductive IGBT (T1, T2), wherein from its collector-emitter voltage (U _CE ) a measuring voltage (u _M ) is determined, and wherein depending on a sign of the determined measuring voltage ( u _M ) and a switching state of its desired control signal (S _n ^* , S _τ ^* ₂ ), then this backward conductive IGBT (Tl, T2) is driven with a gate-emitter voltage above a threshold voltage, if this Sign is positive and the desired control signal (S _n ^* , S _τ ^* ₂ ) in the switching state is "ON".

2. The method according to claim 1, wherein a sign of the ascertained

Measuring voltage (u _M ) is negative and the desired control signal (S _f1 , S _f2 ) is in the "OFF" switching state, a reverse-conducting IGBT (Tl, T2) is not with a gate-emitter voltage above the Threshold voltage is controlled.

3. Device for controlling a backward conductive IGBT (Tl, T2) with a driver circuit (20), the output side with a gate terminal (G) of the backward conductive IGBTs (Tl, T2) is electrically connected, characterized in that is electrically parallel to the collector-emitter path of the backward conductive IGBTs (Tl, T2), a voltage divider (24,32) is connected, the output (22) with an input (26) of an evaluation device (18) is linked, the output side tig is connected to an input of the driver circuit (20), wherein an emitter terminal (E) of the backward conductive IGBTS (Tl, T2) serves as a reference potential.

4. Device for controlling a backward-conducting IGBT (T1, T2) with a driver circuit (20), which is connected on the output side to a gate terminal (G) of the backward-conducting IGBT (T1, T2) in an electrically conductive manner, characterized in that a decoupling circuit (36) is electrically connected in parallel with the collector-emitter path of the backward-conducting IGBT (T1, T2) whose output (22) is linked to an input (26) of an evaluation device (18) on the output side is connected to an input of the driver circuit (20), wherein an emitter terminal (E) of the backward conductive IGBTS (T1, T2) serves as a reference potential.

5. Apparatus according to claim 3 or 4, characterized in that the evaluation device (18) is supplied to a desired control signal (S ^ ₁ , S ^ ₂ ) and a reference voltage (u _R ).

6. Apparatus according to claim 3 or 4, characterized in that the evaluation device (18) has a state table, in the switching states for desired control signals (S ^ ₁ , S ^ ₂ ) and actual control signals (Sτi, S _T 2) and the sign of the determined measuring voltage (u _M ) of a backward conductive IGBTs (Tl, T2) are stored.

7. Device according to claim 3, characterized in that the voltage divider (24) has a measuring range bounded on both sides.

8. Device according to claim 3, characterized in that the voltage divider (32) has a measuring range limited on one side.

9. The device according to claim 4, characterized in that the decoupling circuit (36) has at least one high-voltage diode (38), a voltage source (40) with a series resistor (42) and a voltage divider (44), said voltage divider (44) electrically parallel to the series connection of the voltage source (40) and the series resistor (42) is connected and wherein this parallel circuit is electrically connected in series with the high-voltage diode (38).

10. The device according to claim 4, characterized in that the Abkoppelschaltung (36) has at least one high-voltage diode (38), a current source and a voltage divider (44), said voltage divider (44) is electrically connected in parallel to the series circuit of the power source and this Parallel circuit is electrically connected in series with the high-voltage diode (38).

11. The device according to claim 3, wherein the voltage divider is designed as an ohmic voltage divider.

12. The device according to claim 3, wherein the voltage divider is designed as a capacitive voltage divider.

13. The device according to claim 3, wherein the voltage divider is designed as an ohmic-capacitive voltage divider.

14. Device according to one of the preceding claims, characterized in that these and the driver circuit (20) form a structural unit.