Patent ID: 12255525

DETAILED DESCRIPTION

In the descriptions of the figures below, identical elements or functions have been provided with the same reference symbols.

At present, circuit arrangements are already known for use in inverters which have semiconductor switches10,20which have power semiconductors consisting of a different semiconductor material, i.e., for example, one power semiconductor consisting of silicon carbide, for example an SiC-MOSFET, and one consisting of silicon, for example an Si-IGBT. In general, the power semiconductors consisting of silicon carbide are unipolar component parts, and the power semiconductors consisting of silicon are bipolar component parts.

In the case of the inverter, four switching states are generally passed through within a clock period of a modulation method, as shown inFIG.1using the example of space vector modulation first from 1 to 4 and then back from 4 to 1 (1 and 4 are the zero-voltage space vectors). The possible switchover point SP1, SP2from one semiconductor material to another semiconductor material or vice versa, i.e. from one power semiconductor to another power semiconductor, is at present always located at the end of a modulation period or at the start of the next, as shown inFIGS.2to4. The reason for this is that, until now, an updated item of switching information can only be processed after all of the transitions (1 to 4 and back again) have been passed through completely.

If the electrical clock period T_p is plotted over time, the pulse pattern illustrated by way of example inFIG.2results. What is shown is three phases u, v, w, and, per phase u, v, w, two semiconductor switches10,20, of which one is a high-side switch10and one a low-side switch20, each of which in turn has at least two power semiconductors consisting of a different semiconductor material and connected in parallel with one another. For example, one semiconductor material is silicon carbide SiC and the other is silicon Si. In addition, for example, one of the power semiconductors is a MOSFET, for example an SiC-MOSFET, and the other is an Si-IGBT.

The ratio of the area of the low-side switch20to the area of the high-side switch10results from the present modulation depth, which determines the duty cycle of the individual phases u, v, w. This modulation depth is proportional to the torque or phase current. Then, a new (electrical) clock period begins, in which, depending on the position of the motor, the same or an adjacent sextant of the transition diagram is passed through.

Since the modulation depth changes comparatively slowly, the duty cycle changes from clock period T_p1to clock period T_p2depending on the electrical frequency of the machine in order to modulate a sinusoidal current. When using the same pattern, the duty cycle of the low-side switch20therefore (in this example) doubles, as is shown inFIG.3.

At present, the switchover from one power semiconductor to another power semiconductor, i.e. from one semiconductor material to the other semiconductor material, or vice versa, takes place at the end of a clock period T_p; T_p1, T_p2(also referred to as clock cycle). As a result, this time in which the switch in question (in this case low-side switch20) is active is not doubled. However, it is also possible here for an undesired short pulse to arise, depending on the modulation depth.

In the case of relatively high modulation depths, which result in relatively high duty cycles, the opposite switch (i.e. the high-side switch10) increases its duty cycle, as is illustrated by way of example inFIG.4. The switch-on time of the low-side switch20decreases drastically, however. In the case of fixed switchover at the end of the clock period T_p; T_p1, T_p2, very short pulses of the low-side switch20therefore result primarily in the case of high modulation depths, i.e. long duty cycles.

Short pulse times are critical primarily for silicon semiconductors since they require a certain amount of time to reach a saturated state of their electron-hole plasma. If a disconnection of the component part takes place already before the saturated state is reached, an undesired switching response of the component part can result. Owing to the relatively high proportion of electrons in the total current, the component part can be switched off more quickly, which results in a higher overvoltage and can destroy the component part. In addition, chopping of the load current is possible, which likewise results in an overvoltage. In present silicon-based inverters, therefore, suppression of short pulses in the case of high modulation depths is implemented. The additional switchover of the semiconductor materials intensifies the problem further still, however. Therefore, an aim of the present disclosure is to determine an optimum switchover time between the semiconductor materials.

In the present prior art, as shown inFIGS.2to4, a switchover from one power semiconductor to another power semiconductor takes place in each case at the same switching point SP1and/or SP2at the start or at the end of a clock period T_p of the modulation method, which is generally pulse width modulation.

In order to address the abovementioned problems, in accordance with the present disclosure, actuation of a circuit arrangement takes place in such a way that the switchover no longer, as was previously the case, takes place at the same switching point SP1or/and SP2at the start or at the end of a clock period T_p of the modulation method. Therefore, a switchover between two different semiconductor materials can take place in each of the phases (in this embodiment three phases u, v, w are provided) independently of one another.

In each phase u, v, w, the switchover to the other semiconductor material now takes place at the first switching time SP1_u, Sp1_v, SP1_win a clock period T_p (FIG.5) or at the last switching time SP2_u; SP2_v; SP2_win a clock period T_p (FIG.6) at which switchover is possible between high-side switch10and low-side switch20(or vice versa).

Since, during this switchover time, a dead time also needs to be implemented, using hardware, to protect the semiconductors from bridge short circuits, the change of semiconductor material is particularly sensible here. Thus, the traction inverter can ensure a stable operation without additional switchover operations. The change therefore takes place during the normal change to the complementary switch, i.e. from high-side switch10to low-side switch20, or vice versa.

Before the conducting switch can be changed from the high side to the low side or from the low side to the high side, time is required in which both switches are switched off. This time is necessary since the semiconductor (the semiconductor component) requires a certain amount of time in order to change into the off state. This time is referred to as dead time and is dependent on the semiconductor used. Only after the dead time can the opposite switch be switched on again. During this dead time, the current is injected through the motor winding.

The proposed switchover strategy has the advantages that short pulses are effectively suppressed and that, during each switchover operation (apart from in the case of zero delay), one switch-on operation and one switch-off operation are saved, which results in fewer switching losses. In addition, a switchover of the three phases u, v, w now takes place independently of one another, i.e. the switchover takes place no longer (necessarily) as before at the same switching point SP1and/or SP2at the start or at the end of a clock period T_p of the modulation method.

In specific cases, in particular in the case of a switchover from silicon carbide to silicon, short-pulse suppression still needs to be implemented, depending on the modulation depth, in order to prevent damage to the component part. Short-pulse suppression is implemented, for example, by limiting the modulation depth.

In the examples shown in the figures, a clock period T_p; T_p1, T_p2always begins with a low-side switch20. However, it is also possible for a clock period T_p; T_p1, T_p2to begin with a high-side switch10. The basic concept remains unchanged thereby.

In the figures, in each case three phases u, v, w are illustrated, and the invention has been described with reference to the three phases u, v, w. However, the invention is not restricted to three phases u, v, w. It is also possible for only one, two or more than three phases u, v, w to be provided instead since the basic concept of the invention can also be applied to only one phase.

The power semiconductors can be unipolar component parts such as MOSFETs, JFETs, cascoden etc. but also bipolar component parts such as IGBTs. One semiconductor material is advantageously silicon, the other semiconductor material is advantageously silicon carbide, wherein other semiconductor materials suitable for the application can also be used.

By virtue of the proposed actuating method for a circuit arrangement used in an inverter, a high-efficiency inverter, which is used, for example, as drive inverter or traction inverter, can be achieved in which the switching losses during switchover from one active switch to another active switch (high side to low side or vice versa) are reduced. The circuit arrangement for which the method for actuating is proposed can be used in an inverter of an electronics module for actuating the electric drive of a vehicle equipped with an electric drive. It is also possible for electrified axles to be driven by the electric drive. The actuating method is advantageously operated via a control unit.

An electronics module within the scope of the present disclosure is used for operating an electric drive of a vehicle, in particular an electric vehicle and/or a hybrid vehicle, and/or electrified axles. The electronics module comprises an inverter. In addition, it can comprise a rectifier, a DC/DC converter, a transformer and/or another electrical converter or part of such a converter or a part thereof. In particular, the electronics module is used for energizing an electric machine, for example an electric motor and/or a generator. An inverter is preferably used for generating a polyphase alternating current from a direct current generated by means of a DC voltage of an energy source, for example a battery.

LIST OF REFERENCE SYMBOLS

1-4switching states10semiconductor switch (high-side, HS)20semiconductor switch (low-side, LS)u, v, w phaseSP1, SP2switching point previouslySP1_u, SP2_uswitching point phase uSP1_v, SP2_vswitching point phase vSP1_w, SP2_wswitching point phase wT_p; T_p1; T_p2electrical period