Abstract:
A circuit that electrically controls power includes at least one power control device and at least one heat extraction device. The at least one extraction device is in thermal contact with the at least one power control device. The heat extraction device is arranged such that it can be clamped to a fixed predefined electric potential and electrically insulated by the at least one power control device.

Description:
RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 to EP Application 06405290.5 filed in Europe on Jul. 7, 2006, and as a continuation application under 35 U.S.C. §120 to PCT/EP2007/055343 filed as an International Application on May 31, 2007 designating the U.S., the entire contents of which are hereby incorporated by reference in their entireties. 
     TECHNICAL FIELD 
     The present disclosure relates to electronic circuit arrangements for electrically controlling power, and relates in particular to arrangements for dissipating heat from power semiconductor components arranged in the power control devices, such as thyristor elements, IGBTs (Insulated Gate Bipolar Transistor), and power field effect transistors (Power FET), for example. 
     Interfaces between such power semiconductor components and the rest of the circuit arrangement or environment comprise electrical interfaces for the electrical connection of the power semiconductor components and thermal interfaces, which are designed in particular for efficiently dissipating heat that arises during the operation of the power semiconductor components. 
     Specifically, the present disclosure relates to a circuit arrangement for electrically controlling power with power semiconductor components, which comprises at least one power control device and at least one heat dissipating device having a thermal contact with the at least one power control device. 
     BACKGROUND INFORMATION 
     The heat dissipating devices for dissipating the heat generated in the power control devices are designed in particular with regard to avoiding excessively large differential voltages between electronic components and the heat dissipating devices, which are thermally and electrically conductive. 
     Circuit arrangements for electrically controlling power have voltage differences between individual circuit components, such as power semiconductor components, for example, among one another and between components and corresponding heat dissipating devices, such as cooling elements, for example, which voltage differences can reach high values through to breakdown voltages. 
     In known circuit arrangements, power semiconductor components are arranged on heat dissipating devices which are connected to a ground and are therefore grounded or put at ground potential. Such conventional power control devices for controlling three-phase AC currents and AC voltages are arranged with all the power control modules on a single heat dissipating device, which is clamped or connected to zero volts, such as ground M, for example, as shown in  FIG. 1 . The circuit arrangement in accordance with  FIG. 1  is designed in triple fashion for the power control of three-phase AC currents and AC voltages. The circuit arrangement in  FIG. 1  comprises three switching units E 1 , E 2  and E 3 . The individual switching units E 1 , E 2  and E 3  are in turn formed from power semiconductor components T 1   a , T 2   a  and T 3   a , T 4   a  respectively connected in series. 
     A capacitor C 1  is discharged via the series circuit comprising two resistors R 1  and R 2 . The other two power control devices E 2  and E 3  in  FIG. 1  are formed in a similar manner. All the power semiconductor components T 1   a , T 2   a , . . . , T 3   c , T 4   c  are arranged on a heat dissipating device W 0  for cooling. 
     Said heat dissipating device W 0  has not only a good thermal conductivity but also a high electrical conductivity. During operation of the circuit arrangement, care must be taken to ensure that voltage differences between connection points of the power semiconductor components, on the one hand, and the heat dissipating device W 0 , on the other hand, do not exceed a specific predetermined maximum potential difference value—that is to say a breakdown voltage. 
     For solving the problem it has been proposed to provide individual heat dissipating devices W 1 , W 2 , W 3 , W 4 , W 5  and W 6  for in each case a pair of power semiconductor components, as shown in  FIG. 2 . Although such an arrangement avoids large potential differences between all of the power semiconductor components and a single heat dissipating device W 0 , as shown in  FIG. 1 , the number of circuit components required is disadvantageously increased. 
     Disadvantageously, such an arrangement can only be provided for single-component or double-component arrangements. The potential of the corresponding heat conducting device W 1 -W 6  is thus clamped to a centre potential between the two power semiconductor components, which limits the voltage loading to approximately a quarter of the link voltage. 
     A significant disadvantage of the circuit arrangement shown in  FIG. 2  furthermore consists in the fact that such a high number of heat dissipating devices, in the case shown  18  heat dissipating devices for a three-phase system ( FIG. 2  shows the circuit components for just one phase), is extremely susceptible to faults and expensive. 
     Moreover, inexpediently it is not possible to provide such a heat dissipating arrangement for H bridge modules since the latter do not have a common centre potential point. Thus, a solution proposed in accordance with  FIG. 2  can reduce the dielectric voltage loading of single-switch packages or dual-switch packages, but disadvantageously a cooling method of this type cannot be used for more recent arrangements such as H bridge modules. 
     EP 0933 867 A1 specifies a generic electronic circuit arrangement for electrically controlling power, wherein, in FIG. 2b of EP 0933 867 A1 (reference symbols used below refer to EP 0933 867 A1), the heat dissipating device (14) is electrically connected to the power control device (10) and an electrical insulation (13) is disclosed only between the heat dissipating device (14) and cooling fins (0), but not between the heat dissipating device (14) and the power control device (10). 
     A further generic electronic circuit arrangement for electrically controlling power is specified in EP 0 802 619 A1. 
     SUMMARY 
     The thermal interfaces between power semiconductor components and the rest of the circuit arrangement or environment serve for dissipating heat. Electrical interfaces for the electrical connection of the power semiconductor components are additionally provided. Consequently, potential differences can occur between electronic components and heat dissipating devices. 
     An efficient heat dissipating device is disclosed for power control modules or power control devices for electrically controlling power which have a small number of individual components in conjunction with a high voltage breakdown strength. 
     This object is achieved according to the disclosure by means of a circuit arrangement for electrically controlling power. 
     A circuit arrangement for electrically controlling power, comprising: a) at least one power control device; and b) at least one heat dissipating device having a thermal contact with the at least one power control device; wherein c) the heat dissipating device is clamped to a fixedly predetermined electrical potential, and wherein d) the at least one heat dissipating device is arranged in a manner electrically insulated from the at least one power control device. 
     In another aspect, a power-control arrangement is disclosed. Such an arrangement comprises at least one power control device, and a heat extraction device in thermal contact with the at least one power control device, the heat extraction device being configured to be clamped to a defined electric potential, and to be electrically insulated by the at least one power control device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the disclosure is illustrated in the drawing and explained in more detail in the description below. 
       In the drawing: 
         FIG. 1  shows a conventional circuit arrangement for electrically controlling power with a single heat dissipating device; 
         FIG. 2  shows a further conventional circuit arrangement for electrically controlling power with a plurality of floating heat dissipating devices; and 
         FIG. 3  shows a power control device with electrically clamped heat dissipating devices in accordance with an exemplary embodiment of the present disclosure. 
     
    
    
     In the figures, identical reference symbols designate identical or functionally identical components or steps. 
     DETAILED DESCRIPTION 
     A central concept of the present disclosure consists in providing a minimum number of heat dissipating devices, wherein an individual heat dissipating device is clamped to a fixedly predetermined electrical potential. The fixedly predetermined potential can be an intermediate potential between two power control devices belonging to a power control module. 
     Therefore, the basic concept of the disclosure consists in providing per phase only three heat dissipating devices that are symmetrically clamped to a respective centre potential between the individual power control devices of a power control module. This firstly achieves an optimum reduction of a voltage loading between power semiconductor components and corresponding heat dissipating devices, wherein the number of components to be used is reduced by comparison with the prior art. 
     Furthermore, such an arrangement enables circuit arrangements for electrically controlling power to be designed in the form of dual H bridges. In this case, 3.3 kV standard components can be used for driver units designed for 4.16 kV. 
     A circuit arrangement according to the disclosure for electrically controlling power has at least one power control device and at least one heat dissipating device having a thermal contact with the at least one power control device, wherein the heat dissipating device is clamped to a fixedly predetermined electrical potential. The at least one heat dissipating device can be arranged in a manner electrically insulated from the at least one power control device. As a result, it is possible to obtain a further reduction of the voltage loading between power semiconductor components and corresponding heat dissipating devices. 
     In accordance with one exemplary embodiment of the present disclosure, the power control devices are formed by a series circuit comprising at least two power semiconductor components. In this case, a pair of power control devices forms a power control module. Three power control modules are expediently required for controlling one phase. 
     The power control devices of a module can be electrically connected to one another via a series circuit comprising discharge resistors. 
     In accordance with yet another exemplary embodiment of the present disclosure, the fixedly predetermined electrical potential to which the at least one heat dissipating device is clamped is determined by the discharge resistors. In this case, the discharge resistors represent voltage divider resistors. 
     In accordance with yet another exemplary embodiment of the present disclosure, the fixedly predetermined electrical potential to which the heat dissipating device is clamped amounts to a quarter of the link voltage of the circuit arrangements for electrically controlling power with respect to a ground potential. 
     In accordance with yet another exemplary embodiment of the present disclosure, the power control devices comprise first and second power control devices assigned to one another in such a way that they form a power control module, wherein the discharge resistors of the first and second power control devices clamp the fixedly predetermined electrical potential to a centre potential between connection points of the first and second power control devices. 
     Different heat conducting devices of different power modules can be clamped to different fixedly predeterminable electrical potentials independently of one another. 
     In accordance with yet another exemplary embodiment of the present disclosure, the at least one heat dissipating device is additionally electrically conductively connected to a connecting unit that electrically connects the at least two power semiconductor components of the power control devices to one another. 
     A circuit arrangement of this type achieves the object according to the disclosure, namely of providing electrical power control with efficient heat dissipation, wherein a small number of components are required, wherein a high voltage breakdown strength is simultaneously achieved. 
     An exemplary embodiment of the present disclosure will be described below with reference to  FIG. 3 . 
       FIG. 3  illustrates a circuit arrangement for electrically controlling power for one phase. Electrical three-phase power supplies require a circuit arrangement comprising three phase circuitry interconnections of the kind shown in  FIG. 3 . For illustrating a cooling arrangement according to the disclosure for a circuit arrangement for electrically controlling power it suffices to consider one phase in accordance with  FIG. 3 . 
     The principle underlying the disclosure is based neither on providing a single heat dissipating device put at ground potential, as described with reference to a first conventional circuit arrangement of  FIG. 1 , nor on providing a large number of individual heat dissipating devices (two thereof per power control module), which then have to be at a freely floating potential, as described with reference to  FIG. 2  above for a further conventional circuit arrangement for electrically controlling power. 
     As shown in  FIG. 3 , a phase of the circuit arrangement according to the disclosure for electrically controlling power has three heat dissipating devices  101   a ,  101   b  and  101   c . The three heat dissipating devices  101   a ,  101   b ,  101   c  shown are neither at a ground potential  102  nor are they freely floating. Rather, the basic concept of the disclosure is discernible in the circuit arrangement in  FIG. 3 , namely of clamping the heat dissipating devices  101   a - 101   c  to a fixedly predetermined potential, that is to say to the corresponding electrical potentials  103   a ,  103   b  and  103   c  of the heat dissipating devices  101   a ,  101   b  and  101   c , respectively, with respect to a reference potential, that is to say a ground potential  102 . 
     The circuit arrangement for controlling power comprises three separately identifiable blocks, that is to say power control modules  200   a ,  200   b  and  200   c . Each of said power control modules  200  has first and second power control devices  201 ,  202 , which are jointly cooled by an assigned heat dissipating device  101   a - 101   c.    
     Thus, the first and second power control devices  201   a ,  202   a  are arranged on the first heat dissipating device  101   a  and are thermally conductively connected thereto, the first and second power control devices  201   b ,  202   b  are arranged on the second heat dissipating device  101   b  and are thermally conductively connected thereto, while the first and second power control devices  201   c  and  202   c  are thermally conductively connected to the third heat dissipating device  101   c . Furthermore, the respective heat dissipating device  101   a ,  101   b ,  101   c  is arranged in a manner electrically insulated from the associated power control device  201   a ,  202   a ,  201   b ,  202   b ,  201   c ,  202   c , whereby it is possible to achieve a further reduction of the voltage loading between power semiconductor components T 1   a , T 2   a , T 3   a , T 4   a , T 1   b , T 2   b , T 3   b , T 4   b , T 1   c , T 2   c , T 3   c , T 4   c  of the respective power control device  201   a ,  202   a ,  201   b ,  202   b ,  201   c ,  202   c  and the corresponding heat dissipating device  101   a ,  101   b ,  101   c.    
     The first and second power control devices  201  and  202  are constructed in each case from a series circuit comprising power semiconductor components (e.g. IGBTs), wherein respective first connections of the power control devices are electrically connected to a common point, while first and second connection units  104   a  and  105   a  are connected to one another via a series circuit comprising two resistors R 1 , R 2 . 
     It should be pointed out that the reference symbols for the three separately identifiable power control modules  200   a ,  200   b ,  200   c  are provided with lower-case letters a, b, c in order to clarify the assignment to a corresponding power control module. 
     According to the disclosure, the discharge resistors R 1 , R 2 , which serve for discharging corresponding capacitors (capacitor units) C 1 , C 2 , form a voltage divider, wherein a centre tap at a junction point between the two resistors R 1  and R 2 , or respectively R 3  and R 4 , or R 5  and R 6  in each case forms a centre potential to which the corresponding heat dissipating device  101   a ,  101   b  or  101   c , respectively, is clamped. 
     It is assumed hereinafter that the ground potential  102  is 0V. This then results in a link voltage of +E/2 present at the first connection unit  104   a  of the first power control device  201   a  of the first power control module  200   a , while a negative link voltage (−E/2) is present at a second connection unit  105   b  of the second power control device  202   b  of the second power control module  200   b.    
     A second connecting unit  107   c  that electrically connects at least two power semiconductor components T 3   c , T 4   c  of the power control device  202   c  is referred to as a centre potential point and is electrically conductively connected to the heat dissipating device  101   c.    
     The respective voltage divider resistors, which are formed by identical resistors in an exemplary embodiment of the present disclosure, that is to say that R 1 =R 2  and R 3 =R 4 , have the effect that the respective heat dissipating devices  101   a ,  101   b  are clamped to an electrical potential  103   a  and  103   b , respectively, which has a value of a quarter of the link voltage (E/4) with respect to ground  102  (0V). 
     Furthermore, three reference potential detection units X 1 , X 2  and X 3  are provided, at which it is possible to detect corresponding reference potentials of the power module  200   a  with respect to an electrical potential  103   a  of the heat dissipating device  101   a.    
     Consequently, the object according to the disclosure is achieved, namely of providing a high voltage breakdown strength in conjunction with a reduction of the number of required components (in particular of the heat dissipating devices  101   a - 101   c ). 
     The circuit scheme for the arrangement of power control devices and heat dissipating devices as described with reference to  FIG. 3  can in particular be applied to circuit topologies having the following configurations:
         three level neutral point clamped (3LNPC);   three level active neutral point clamped (ANPC); and   ABB five-level topology (ABB5L).       

     In particular, the circuit arrangement and cooling arrangement described in accordance with the above exemplary embodiment with reference to  FIG. 3  is suitable for being used in medium voltage operation. 
     Although the present disclosure has been described above on the basis of various exemplary embodiments, it is not restricted thereto, but rather can be modified in diverse ways. 
     Moreover, the disclosure is not restricted to the application possibilities mentioned. 
     It will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the invention is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein. 
     LIST OF REFERENCE SYMBOLS 
     In the figures, identical reference symbols designate identical or functionally identical components or steps.
       101   a —Heat dissipating device     101   c        102  Ground potential     103   a —Electrical potential of the heat dissipating     103   c  device     104   a —First connection unit     104   c        105   a —Second connection unit     105   c        200   a , Power control module     200   b,        200   c        201   a —First power control device     201   c        202   a —Second power control device     202   c      E Link voltage potential   C 1 -C 2  Capacitor unit   R 1 -R 6  Discharge resistor   T 1 -T 6  Power semiconductor component   X 1 -X 3  Reference potential detection unit