Power Semiconductor Module and Circuit Arrangement Comprising at Least Two Power Semiconductor Switch Modules

1. Field of the invention

The invention relates to the field of power electronics.

It proceeds from a circuit arrangement or from a power semiconductor module in accordance with the preamble of the corresponding independent claims.

2. Discussion of background

European Patent Application EP-A2-0 417 747 has already described such a circuit arrangement or such a power semiconductor module.

In that case, the circuit arrangement comprises at least two power semiconductor switch modules having a package, two main connections and two gate connections. The power semiconductor modules used are constructed correspondingly.

A module comprises, as a rule, a plurality of semiconductor components which can be combined to form a logic functional unit. Examples are rectifiers, individual switches comprising antiparallel diodes or entire phase assemblies. Such modules (thyristor, transistor, IGBT, diode modules) are nowadays widespread in the power region of 1,200 V and a few 100 A and are primarily used in industrial drives.

In order to obtain a required performance, a plurality of components of one type are, as a rule, connected in parallel in one module. Thus, for example, each IGBT half-bridge module for 150 A, 1,200 V may contain six parallel-connected IGBTs and two parallel-connected antiparallel diodes per switching function.

At present, upper limits are imposed on the performance of modules (in particular in relation to current carrying capacity) since modules cannot be constructed with any size desired. The difficulties lie in the reliability problems, which increase considerably with the overall size, and the parallel connection of a large number of components, which becomes increasingly more difficult.

In addition, with increasing size of the modules, one of their outstanding characteristics is lost, namely the modularity, i.e. the increase in the electrical power not through ever larger components but by connecting ever more similar components in parallel. For these reasons, the unlimited connectability of modules in parallel would be a desirable characteristic.

Unfortunately, limits are imposed on the connectability of modules in parallel. Since, after all, the electrical parameters of the modules are never quite identical, the forward, reverse and switching behavior of the modules may be different. In the case of parallel connection, this may result in oscillations or overloading of individual modules until they are destroyed. The publication mentioned at the outset attempts to counteract this by attempting to reduce the inductance of the commutating circuit by means of a special arrangement of the electrodes.

However, this does not take account of the abovementioned problems, which are due to parameter differences. As a rule, this problem is solved by preselecting the modules to be connected in parallel in relation to critical parameters. As a result, it later becomes virtually impossible in the application to replace a single module in a parallel circuit. A further possibility is that the modules are not exploited up to their specified performance ("derating").

In a new category of modules, the so-called integrated or intelligent modules (integrated power modules, IPM), additional functions, such as triggering of the components to be switched, logic for recognizing faults (e.g. excess temperature, overcurrent, undervoltage of the supply) and electrical isolation of the triggering and fault signals are incorporated in the module.

Added to the problems described above in the case of the parallel connection of such modules, which parallel connection is required for high powers, are those of the triggering, fault detection and fault processing, etc. which do not function precisely simultaneously.

Thus, for example, a slight variation in the voltage supply of the receiver of an optical waveguide used for the potential-free transmission of the triggering signal and incorporated in the module may result in a propagation time delay of a few 100 nsec, which has a considerable adverse effect on the parallel connection of such modules.

Accordingly, one object of the invention is to provide a novel circuit arrangement and a power semiconductor module in which the abovementioned problems can be avoided in the case of parallel connection. In particular, it is intended that the power semiconductor module can be connected in parallel with other modules without preselection and derating up to the full specified performance.

This object is achieved in a circuit arrangement or a module of the type mentioned at the outset by the features of the corresponding independent claim.

The essence of the invention is therefore that the power semiconductor module has, in addition to the gate connection and the main connections, a number of signal connections which are interconnected when a plurality of modules is connected in parallel. In addition, only a single, freely selectable power semiconductor module is connected to the control device.

If a plurality of modules according to the invention are connected in parallel, this results in a common signal bus which is driven by that module which is connected to the control device. The latter module therefore functions as master, while the others have the function of a slave.

Preferably, the connection between the gate connections and the control device is made in a potential-free manner and, in particular, using optical waveguides. In addition, the modules may be mounted on a heat sink.

In addition, there may be provided between the gate connections and the signal connections an interface which is responsible for the required signal matching. Said interface may be provided either only in the case of the master or in the case of all the parallel-connected modules.

Further exemplary embodiments emerge from the corresponding subclaims.

The advantage of the construction according to the invention is, in particular, that a plurality of modules according to the invention can be connected in parallel without preselection or derating since the master governs the other modules, with the result that the problems mentioned at the outset are eliminated. In addition, only one type of module has to be manufactured and only one potential-free connection has to be provided. This reduces the user's production costs considerably. However, the operating costs can also be reduced effectively since, firstly, the uniform loading, governed by the master, of all the modules increases the service life and, secondly, a defective module can be replaced within the parallel connection without difficulty.

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing, wherein the sole drawing (FIG. 1) shows the parallel connection of four power semiconductor modules according to the invention.

Referring now to the drawing, FIG. 1 shows the structure of a power semiconductor module (1) according to the invention. This may be any power semiconductor module, for example a GTO, thyristor, IGBT or diode module.

The module (1) always comprises a package (2) having, for example, two main connections (3.1, 3.2), at least one gate connection (5.1, 5.2) and a number of signal connections (4.1-4.4). The gate connection comprises, for example, a first connection for signals to be conducted away from the module and a second connection for signals to be conducted to it. It is, in particular, of potential-free design and may be connected, for example, via optical waveguides (8) to a control device, which is not shown. Preferably, the power semiconductor modules (1) are mounted on a heat sink (6) which has, for example, a coolant flowing through it. In this case, coolant connections (7.1, 7.2) are provided on the heat sink (6). According to a preferred constructional variant, the liquid connections (7.1 and 7.2) and the optical waveguide connections (5.1 and 5.2) are disposed on the same side.

According to the invention, the power semiconductor module (1) also has a number (four are shown) of signal connections (4.1-4.4). The signal connections may comprise, for example,

a first path for triggering the switches,

a second path for fault signals,

a third path for clocking the power semiconductor modules, and

a fourth path via which the gate electrodes of the switches can be connected.

If a plurality of modules (1) according to the invention are connected in parallel, a signal bus consequently results which has, for example, the above signals. Preferably, the signal connections (4.1-4.4) are disposed on a separate side of the package.

In addition, there may be incorporated in the power semiconductor modules (1) an interface which converts the signals coming from the control device and transmitted via the optical waveguides into suitable signals for the signal bus. The signal connections (4.1-4.4) are therefore connected signalwise to the gate connections (5.1, 5.2).

The arrangement becomes particularly inexpensive if only that module (1) which is connected to the control device is provided with an interface.

If a plurality of power semiconductor modules (1) according to the invention is connected in parallel, a circuit arrangement consequently results in which

only one, freely selectable power semiconductor module (1) is connected to a control device via gate connections (5.1, 5.2),

a number of signal connections (4.1-4.4) which can be connected signalwise to the gate connections (5.1, 5.2) are interconnected and form a signal bus.

Since only one module is connected to the control device, it functions as a master which the other modules follow. In this way, it is possible to avoid the problems mentioned at the outset and encountered when a plurality of modules is connected in parallel.

In total, the invention provides a power semiconductor module which can be used without difficulty up to maximum powers in an arrangement comprising parallel-connected modules.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.