JP7083338B2 - Control of semiconductor switch in switch mode - Google Patents

Description

The present invention relates to a method and a circuit for controlling a semiconductor switch in a switch mode.

The switch path is controlled by the switching potential so that the switch path of the semiconductor switch is in the switch ON state or the switch OFF state according to the switching potential in the control electrode of the semiconductor switch, and the switch path is changed from the switch ON state to the switch OFF state. In the switching process, the switch path voltage in the switch path is measured, and when the switch path voltage reaches the maximum voltage, a limiting potential that makes the switch path conductive is applied to the control electrode in order to limit the switch path voltage to the maximum voltage. do.
The semiconductor switch is controllable via a control electrode, has a switch path that switches on or off depending on the switching potential in the control electrode of the semiconductor switch, and applies the switching potential to the control electrode. The drive unit can be connected to the control electrode, a voltage sensor that can be connected to the switch path is provided to measure the switch path voltage, and the drive unit is at least the switching process from the switch ON state to the switch OFF state of the switch path. When the switch path voltage reaches the maximum voltage, the switch path voltage is limited to the maximum voltage by applying a limiting potential to the control electrode to bring the switch path into a conductive state.
Further, the present invention includes a first electric terminal, a second electric terminal, at least one semiconductor switch, and a control circuit connected to a control electrode of at least one semiconductor switch, and the first electric terminal. It relates to a clocked energy converter configured to control a semiconductor switch to electrically connect a second electrical terminal.

Since the clocked energy converter, the semiconductor switch, and the control method of the semiconductor switch are well known in principle in the prior art, it is not necessary to separately present the literature in this regard. Semiconductor switches are often used so that clocked energy converters can convert electrical energy into the desired form. In this application, semiconductor switches generally operate in switch mode. The switch mode of the semiconductor switch causes a peculiar problem that the reliability of the circuit having the semiconductor switch is adversely affected, and thus the reliability of the clocked energy converter having such a semiconductor switch.

For example, in a switch-off process when the semiconductor switch does not have a return path, parasitic inductance and / or individual inductance can cause high voltage, especially short-term, high voltage peaks in the switch path of the semiconductor switch. The switchpath voltage across the switchpath can reach levels that cause damage or destruction of the semiconductor switch. Such damage to the semiconductor switch may accelerate the deterioration of the entire semiconductor switch.

Therefore, active clamping in a semiconductor switch is generally performed, for example, such as an insulated gate bipolar transistor (IGBT). The IGBT is a control path having an emitter terminal and a collector terminal as control path terminals, and has a control path whose conductivity can be controlled by a control electrode (in this case, a gate). When a switching potential is applied to the gate, the IGBT operates in switch mode. This control path behaves essentially like an electromechanical switch and is therefore also referred to below as the switch path. The switch path voltage (collector-emitter voltage in the IGBT) is fed back to the control electrode (gate in the IGBT) by an electronic circuit. As a result, incomplete conductivity of the switch path can be obtained, the voltage gradient of the switch path voltage can be reduced, and a reduction in the voltage peak in the switch OFF process can be achieved. Such a problem is not limited to the IGBT, but can occur in a general transistor switching operation. That is, it can also occur in bipolar transistors, field effect transistors (particularly metal oxide semiconductor field effect transistors (MOSFETs)) and the like.

The overvoltage applied to the switch path of the semiconductor switch can be limited to the maximum value fixed by the active clamp. The merit of this method is that it does not need to be set corresponding to the maximum overvoltage that can take the maximum value of the switch OFF speed, which generally lowers the switch OFF speed, but simply corresponds to the overvoltage generated in the switch path each time. It can be limited to a fixed set value, that is, a fixed default value. As a result, the switch OFF speed is maintained relatively high, and the switch loss of the semiconductor switch can be reduced as a whole.

Although such a method of the prior art is effective in the above contents, further improvement is desired. For example, the electrical strength of a switch path has been found to be clearly a function of the temperature of a semiconductor switch, especially the temperature of the chip. In general, the active clamp design minimizes electrical strength based on the switch path. According to this, the active clamp is active even when no temperature-based response of the semiconductor switch is required. As a result, the specifications of the semiconductor switch and the clocked energy converter including the semiconductor switch are unnecessarily limited.

An object of the present invention is to improve a method for controlling a semiconductor switch in a switch mode, a control circuit for the control, and a clocked energy converter.

As a solution, the present invention proposes the methods, control circuits, and clocked energy converters set forth in the independent claims.

An additional advantageous form is obtained by adopting the characteristics of the dependent claim.

The present invention is based on the finding that the maximum permissible switchpath voltage applied to a switchpath without damaging the switchpath or semiconductor switch is clearly a function of temperature. It has been found that the maximum permissible switchpath voltage at low temperatures, especially below freezing, is much lower than above freezing. Such dependence on temperature is, of course, related to the temperature of the switch path, eg, the temperature of the chip of the semiconductor switch. The effect of temperature-based switch path isolation is, of course, not limited to near freezing, and is significant at temperatures above and below freezing. However, in practice, the freezing point is of particular interest, especially with respect to clocked energy converters for automobiles. In principle, of course, other surrounding environments can also be factors in design-based constraints such as spatial distance and creepage distance. For example, if greater spatial and creepage distances are realized in semiconductor switches, other improvements in rapid switching can be obtained. However, if it is attempted to be set appropriately, a larger configuration is required, and the dimensions of the semiconductor switch become large.

The present invention utilizes such findings to measure the temperature of the switch path and determine the maximum voltage suitable for the method of the present invention as a function of the measured temperature.

As a result, according to the comprehensive method specifically proposed by the present invention, the temperature of the switch path is measured by the temperature sensor thermally connected to the switch path, and the maximum voltage is determined as a function of the measured temperature. To.

According to the comprehensive control circuit specifically proposed by the present invention, the drive unit has a temperature sensor thermally connected to the switch path to measure the temperature of the switch path, as a function of the measured temperature. It is configured to determine the maximum voltage.

According to the comprehensive clocked energy converter specifically proposed by the present invention, the control circuit according to the present invention is provided.

Thus, according to the present invention, the normally inflexible active clamp can only be addressed by the active clamp when necessary to protect the switch path from switch path voltages that exceed the maximum permissible switch path voltage. As such, it can be adjusted as a function of the measured temperature of the switch path. Thus, according to the present invention, active clamps are limited only when absolutely necessary. As a result, the disadvantages of active clamping (especially the efficiency and output loss of semiconductor switches) are reduced.

The semiconductor switch is preferably an electronic component, and in particular, a transistor such as a bipolar transistor, an IGBT, or a field effect transistor (including a junction gate field effect transistor).

The transistor has a controllable path as a switch path between two electrodes formed in the semiconductor switch. In a bipolar transistor, these electrodes are a collector terminal and an emitter terminal. In field effect transistors, these electrodes are the drain terminal and the source terminal. The switch path and its conductivity are regulated by the charge on the control electrodes. The control electrode is a base terminal in a bipolar transistor and a gate terminal in a field effect transistor.

In switch mode, the switching potential corresponding to the control electrode is used as a charge and assigned to a particular switch state of the semiconductor switch or its switch path, respectively. The first switching potential is assigned to the switch ON state of the switch path, and the second switching potential is assigned to the switch OFF state of the switch path. When the switch path is switched on, the electrical resistance of the switch path is very low, and even if there is a high current suitable for the switch path, the voltage is virtually zero, or the residual voltage is in the switch path anyway. It has been released. On the other hand, in the switch OFF state, the electric resistance is very high, and even if a high switch path voltage exists in the switch path, essentially no current flows. In any case, some residual current or leakage current is generated.

In the switch mode of the semiconductor switch, essentially only the switch ON state and the switch OFF state of the switch path are assumed. The intermediate state occurs only at the time of transition from the switch ON state to the switch OFF state or from the switch OFF state to the switch ON state. This distinguishes it from the linear mode in which the conductivity of the control path of the transistor can be adjusted essentially continuously as a function of the charge of the control electrode. Generally, this does not occur in switch mode.

In particular, when the switch state of the switch path changes from the switch ON state to the switch OFF state, it is transient to the switch path based on the switch OFF speed due to other switching elements with which the semiconductor switch cooperates, such as inductance and parasitic inductance. Overvoltage occurs. The active clamp allows the semiconductor switch to operate in linear mode during periods of overvoltage, i.e., deviate from the strict switch mode in order to limit the switch path voltage to the maximum voltage. The limiting potential works for this. Due to the limiting potential acting on the control electrode, the switch path becomes incompletely conductive, and if the switch path voltage is essentially maintained, a current flows so that the switch path voltage is limited to the maximum voltage, and energy is dissipated. Will be done. Here, the switchpath voltage is measured and may be used to control the active clamp. In this way, the control path can be controlled by the charge of the control electrode so that the switch path voltage does not exceed the maximum voltage.

In principle, the temperature sensor may be any suitable temperature sensor thermally connected to the switch path to measure the temperature of the switch path. Therefore, the temperature sensor may be integrally configured with a semiconductor chip that also has a switch path at the same time. Further, for example, the temperature sensor may be arranged separately so as to be in contact with the region of the cooling surface of the semiconductor switch, particularly the semiconductor switch, particularly to be in contact with the cooling surface. In addition, the temperature sensor may be placed on the thermally connected heat sink of the switch path so that the thermal energy released during the proper operation of the semiconductor switch can be removed. In principle, the temperature sensor may be an electrical resistor whose electrical resistance changes as a function of temperature.

The sensor signal of the temperature sensor generated by the temperature sensor as a function of the measured temperature is evaluated by the control unit to which the temperature sensor is connected. Then, based on the signal from the temperature sensor, if the switch path does not directly correspond to the signal, the control unit determines the temperature of the switch path. Then, the maximum voltage for the function of the active clamp is determined in consideration of the determined temperature. Given this determined maximum voltage with respect to the function of the active clamp, the active clamp functions during normal operation of the semiconductor switch to the extent necessary to protect the switch path from voltages above the maximum voltage. In addition, the temperature may be measured continuously or repeatedly by a temperature sensor in order to redetermine or update the maximum voltage. In this way, the function of the active clamp can be adjusted even during the normal operation of the semiconductor switch.

In determining the maximum voltage, regardless of the measured temperature, the control unit may start with a predetermined maximum voltage that can ensure proper operation over the entire temperature range. At this time, the predetermined maximum voltage is the minimum value, and by maintaining the value, the switch path is protected from the influence of the overvoltage regardless of the temperature of the switch path.

Starting from a given maximum voltage, the drive unit then performs the corresponding additions taking into account the measured temperature to determine the maximum voltage. If the temperature of the switch path is clearly above the freezing point, a corresponding factor is provided, for example, from a given maximum voltage to determine the maximum voltage at which the active clamp is performed. Of course, other determination methods may be adopted. For example, the maximum voltage may be determined by referring to a table in which the corresponding values such as the measured temperature and the maximum voltage are stored.

One of the advantageous improvements of the present invention is that the switch path operates outside the switch mode due to the limiting potential. This mode is preferably a linear mode. This simultaneously provides a linear mode that allows current flow so that the switch path voltage is limited to the maximum voltage, allowing the maximum voltage to be applied to the switch path. Therefore, a limiting potential suitable for this is applied to the control electrode.

The limiting potential may be the potential determined for the reference electrode of the switch path. For example, it is an emitter terminal in a bipolar transistor and a source terminal in a field effect transistor. Therefore, a voltage is applied to the control electrode facing the reference electrode of the semiconductor switch so that the desired potential can be provided to the control electrode as a limiting potential.

One of the improvements is that the switching edge of the switching potential is adjusted, at least in the switching process from the switch ON state to the switch OFF state of the switch path, as a function of the switch path voltage that has reached the maximum voltage. The function of the active clamp may be further improved in this way. That is, due to the switching potential acting on the switching edge. A transition state between the switch-on and switch-off states may be used to achieve or support the preferred function of the active clamp.

The temperature sensor preferably comprises at least two series of electrical resistances. The value of the electrical resistance of at least one resistor may vary as a function of temperature. In this way, the temperature of the switch path can be easily measured. Examples of electrical resistance whose resistance value changes as a function of temperature include positive temperature coefficient (PTC) resistance. The temperature sensor may be used as a voltage sensor that simultaneously measures the switch path voltage.

It is particularly advantageous to assume that the resistance whose resistance value changes as a function of temperature is a negative temperature coefficient (NTC) resistance. NTC resistance is particularly suitable for temperature measurement because it has a favorable characteristic curve for measuring temperature. In addition, NTC resistors are particularly cost-effective to produce and can be easily assembled into the semiconductor switch housing. It will be apparent to those skilled in the art that if NTC resistors are used instead of PTC resistors, the switch structure will be adjusted to provide temperature measurement functionality. This kind of strategy should not be explained in detail here. Instead, the relevant literature is cited as follows: For example, “Kleine Elektronik-Formelsammlung fur Radio- Fernsehpraktiker und Elektroniker” [Small Electronics Formulary for Radio / Television Practitioners and Electronics Engineers] by Georg Rose, Franzis-Verlag Munich, 1977.

One of the improvements of the present invention is that the drive unit includes a comparison circuit to which a temperature sensor is connected. The comparison circuit is configured to evaluate the value of the measured signal from the temperature sensor, compares it with a predetermined comparison value, and if the measured signal value is larger than the comparison value, sends the comparison signal to the drive unit. Preferably, the comparison circuit comprises an operational amplifier operating in comparator mode. It is particularly advantageous for the comparator to have a feedback element that allows the accuracy of the comparison threshold to be easily adjusted. For example, the comparison value is provided by a voltage source that supplies as constant a voltage as possible. The comparison value is preferably not a function of temperature. In this way, the influence of temperature is avoided as much as possible in the comparison circuit. In this way, the reliable operation of the comparison circuit is ensured, and improper operation of the active clamp that exceeds the maximum voltage, for example, can be almost avoided. The comparison circuit supplies a comparison signal used by the drive unit to apply a limiting potential to the control electrodes. For this purpose, the drive unit has a suitable adaptive circuit.

It is particularly advantageous if the drive unit is configured to supply a limiting potential so as to overlay the comparison signal on the switching potential in the switch OFF state. In this way, another functional unit may be provided in the drive unit so that the function of the active clamp is easily integrated into the drive unit. The overlay is realized by overlaying the switching potential and the limiting potential with a combinational circuit such as an adder or subtractor.

Further, it is preferable that the drive unit has a series connection consisting of a diode and an electric resistance. Here, in this series connection, one connector is connected to the control electrode and the other connector is connected to the comparison circuit. In this way, the comparison circuit is separated from the circuit section of the drive unit that supplies the switching potential. The function of series connection is not based on the sequence in which diodes and resistors are placed in series. On the contrary, only the polarity of the diode is involved in the disconnection function.

The advantages, features, and effects described for the methods of the invention and the control circuits of the invention also apply, of course, to clocked energy converters. Furthermore, the merits and features described as the method of the present invention also apply to the control circuit of the present invention and vice versa.

Additional merits and features will be clarified by the following description of the exemplary form with reference to the accompanying drawings. In the figure, the same reference numerals indicate unified configurations and functions.

It is a schematic diagram explaining the active clamp by two graphs. It is a schematic circuit diagram of the 1st control circuit which has the drive circuit and the control circuit for the active clamp of the IGBT, and the active clamp is generated by the use of a Zener diode. It is a schematic circuit diagram of another control circuit for a drive circuit, and has an active clamp function as shown in FIG. It is a schematic diagram of the switch OFF process in an IGBT, and the chip temperature of the IGBT is lower than the freezing point. It is a schematic diagram similar to FIG. 4, but the chip temperature exceeds the freezing point. It is a schematic diagram which showed the typical characteristic curve of NTC resistance in a graph. It is a schematic circuit diagram of the control circuit of the present invention connected to an IGBT, and the active clamp function uses the maximum voltage of the switch path of the IGBT as a function of temperature.

FIG. 1 is a schematic diagram showing the switching behavior of the IGBT 10 with an active clamp. The X-axis 60 in the graph of FIG. 1 shows the time axis, and the Y-axis 62 in the graph of FIG. 1 shows the current flowing through the switch path 12 of the IGBT 10 and the switch path voltage of the switch path 12 of the IGBT 10. The current is shown in graph 70 and the corresponding voltage is shown in graph 64. Further, the straight line specified by reference numeral 66 in FIG. 1 indicates the maximum voltage of the active clamping function. The straight line specified by reference numeral 68 in FIG. 1 indicates the supply voltage to the IGBT 10, and the supply voltage in this case is the intermediate circuit voltage of the DC voltage intermediate circuit (details are not shown).

As can be seen from FIG. 1, at time t1, the IGBT 10 and its switch path 12 are in the switch ON state. At time t1, the switch path 12 is switched off by an appropriate switching potential. As a result, as can be seen from graph 64, the switch path voltage begins to rise at time t1.

Graph 70 in FIG. 1 shows that the current flowing through the switch path 12 decreases with a time delay. At time t2, the switch path 12 of the IGBT 10 is in the switch OFF state. From the graph 70, it can be seen that the current is so small that it cannot be shown. As a result, the switch path voltage of graph 64 approaches the supply voltage corresponding to the straight line 68.

It can be seen that the switch path voltage is limited to the maximum voltage 66 near the center of FIG. Depending on the switching specifications, the switch path voltage may exceed the maximum voltage 66 at this point. However, the active clamp limits the switchpath voltage to a maximum voltage of 66.

The schematic schematics of FIGS. 2 and 3 show an example of a typical circuit that detects transient overvoltages in the switch path 12 of the IGBT 10, and the properly embodied drive unit 20 includes a feedback element. There is.

FIG. 2 shows a first embodiment comprising a drive unit 20 that provides a power amplifier (details not shown) for the control signal of the gate 14 of the IGBT 10 in a known manner. Here, the output of the power amplifier is connected to the gate 14 of the IGBT 10 via a resistance diode network. Further, a series connection of the Zener diode 72, the electrical resistance 74, and the diode 76 is connected between the collector 52 of the IGBT 10 and the gate 14 of the IGBT 10. The Zener diode 72 is designed to specify a maximum voltage 66 with respect to the Zener voltage.

When the gate control voltage is removed from between the gate 14 and the emitter 50, as soon as the switch path voltage reaches the Zener voltage between the collector 52 of the IGBT 10 and the emitter 50, the switch path 12 of the IGBT 10 becomes conductive again and the Zener The diode becomes conductive so that the gate 14 is charged with an additional charge. In this way, the active clamping effect shown in FIG. 1 can be obtained.

FIG. 3 shows another embodiment of the active clamping function, in which a comparator 80 is provided and a switching voltage 84 is applied. On the output side, the comparator 80 is connected to the gate 14 of the IGBT 10 via the gate resistance 82. In this case, the evaluation circuit 78 is connected to the collector 52 of the IGBT 10 and transmits the evaluation signal corresponding to the comparator 80. As soon as the gate voltage is removed and the switch path voltage between the collector 52 and the emitter 50 reaches the specified maximum voltage 66, the switch path 12 of the IGBT 10 is switched to the conductive state by the comparator 80. And again, it is limited to the maximum voltage 66 in FIG.

In the form of the circuits of FIGS. 2 and 3, the minimum breaking property is assumed in this regard based on the switch path 12. This occurs when the switch path 12 of the IGBT 10 is cold and therefore the IGBT 10 needs to be switched off more slowly than is possible at high temperatures.

As the temperature rises, the cutoff property of the switch path 12 of the semiconductor circuit improves, so that the voltage range applicable to the switch OFF process also widens. In this way, the switch OFF speed can be increased at higher chip temperatures or higher switch path 12 temperatures. Since the active clamp is planned here by design, the active clamp is already effective before the operating condition of the semiconductor switch 10 requires. Typical behavior of the semiconductor switch 10 at different chip temperatures is shown in FIGS. 4 and 5.

This means that the potential for operation at the minimum possible output loss is used at a fixed level where the maximum voltage 66 is fixed, or at an adjustable level where the maximum voltage 66 is not a function of temperature. There is.

FIG. 4 is a first schematic diagram showing the switch-off process at a temperature below the freezing point, similar to FIG. In this case, the switch OFF process is slowed down so that the active clamp is no longer needed at this point. This graph essentially corresponds to the graph already described with reference to FIG. 1, so please refer to the description. In this case, the chip temperature is below the freezing point. The straight line 86 shows the maximum electrical strength of the switch path 12 at this temperature. As can be seen from FIG. 4, the switch path voltage between the collector 52 and the emitter 50 shown in Graph 64 does not exceed the straight line 86. Therefore, it is not necessary to generate an active clamp.

FIG. 5 is similar to FIG. 4, but the chip temperature is higher than the freezing point. As can be seen from FIG. 5, a higher maximum permissible voltage is possible here for the switch path 12, which is shown by a straight line 88 in FIG. As a result, higher switch speeds are possible during switching of the IGBT 10, and thus the voltage between the collector 52 and the emitter 50 of the IGBT 10 can also be increased, as shown in FIG. Again, no active clamp occurs at the selected switch speed.

In the present invention, the maximum voltage 66 can be adjusted by utilizing the effects described with reference to FIGS. 4 and 5. Therefore, it is possible to realize a higher switch speed at a higher chip temperature, the output loss of the IGBT 10 is reduced as a whole, and the efficiency is improved. Therefore, in the present embodiment of the present invention, an electric resistance 16 that can be changed as a function of temperature and is configured as an NTC resistance is provided in this case. By using the electrical resistance 16 in the feedback circuit of the drive unit 20, the maximum voltage 66 can be changed as a function of the temperature of the switch path 12. Here, the characteristic of the negative temperature coefficient of the NTC resistance as shown in FIG. 6 is used.

FIG. 6 is a schematic diagram in which the X-axis 92 shows the temperature and the Y-axis 90 shows the resistance value. Graph 94 shows the curve of the electric resistance value with respect to the temperature. As can be seen from FIG. 6, the electric resistance value decreases as the temperature rises.

FIG. 7 is a schematic circuit diagram showing a control circuit 44 that controls a semiconductor switch (here, IGBT 10) in the switch mode. In this case, the IGBT 10 is a component of a clocked energy converter (details not shown), which is an inverter here. Alternatively, the energy converter may be a converter, a DC / DC converter, or the like.

The IGBT 10 is arranged in a circuit topology (details not shown) that causes a parasitic inductance 46 in the collector terminal 52. The inductance 46 is arranged in series with the IGBT 10. The series connection of the IGBT 10 and the inductance 46 is connected to an intermediate circuit DC voltage (details are not shown). Further, the switch path 12 of the IGBT 10 is arranged in parallel with the diode 48. Here, the diode 48 is an inverting diode. Therefore, the anode of the diode 48 is connected to the emitter 50 of the IGBT 10, and the cathode of the diode 48 is connected to the collector 52 of the IGBT 10. The inverting diode 48 allows current to flow against the polarity of the IGBT 10.

The IGBT 10 includes a switch path 12, which is controlled via a gate 14 as a control electrode and is configured to be in a switch ON state or a switch OFF state based on the switching potential of the gate 14 of the IGBT 10. ing. In this case, the control circuit 44 comprises a voltage sensor 18 connected to the switch path 12 to measure the switch path voltage and a drive unit 20 that may be connected to the gate 14 to apply a switching potential to the gate 14. There is. The drive unit 20 measures the switch path voltage of the switch path 12 at least once during the process of switching the switch path 12 from the switch ON state to the switch OFF state, and when the switch path voltage reaches the maximum voltage 66, the drive unit 20 measures the switch path voltage. In order to limit the switch path voltage to the maximum voltage 66 by making the switch path 12 conductive, the limiting potential is configured to be applied to the gate 14.

Further, the drive unit 20 has a temperature sensor 96 thermally connected to the switch path 12 in order to measure the temperature of the switch path 12. Further, the drive unit 20 is configured to determine the maximum voltage 66 as a function of the measured temperature.

The temperature sensor 96 has two electric resistances 16 and 22 arranged in series, and one of the resistances 16 can change the electric resistance value as a function of temperature. In this case, the resistor 16 is an NTC resistor, as already described with reference to FIG.

Further, the drive unit 20 has a comparison circuit 26 to which the temperature sensor 96 is connected and configured to evaluate the value of the measurement signal from the temperature sensor 96. The comparison circuit 26 compares the measured signal value with the predetermined comparison value 28, and if the measured signal value is larger than the comparison value 28, transmits the comparison signal 30 to the drive unit 20. In this case, the comparison value 28 is provided by a constant voltage source connected to the comparator as the comparator 26. In this case, the comparison value 28 is connected to the inverting terminal of the comparator 26.

The drive unit 20 is configured to overlay the comparison signal 30 on the switching potential in the switch OFF state so as to supply the limiting potential. Overlaying is done at gate 14 of the IGBT 10. Therefore, the drive unit 20 has series connections 32 and 34 composed of electric resistances 36 and 38 and diodes 40 and 42, respectively. In the series connections 32, 34, one connector is connected to the control electrode 14 or the other control terminal of the drive unit 20, and the other connector is connected to the comparison circuit 26, here the output terminal of the comparator that provides the comparison signal 30. ing.

The voltage sensor 18 and the temperature sensor 96 are integrally configured. The center tap of the voltage sensor 18 is connected to the inverting input terminal of the comparator 26. When the voltage at the center tap is higher than the voltage of the constant voltage source and the comparator 26 transmits the output signal as the comparison signal 30, the limiting potential is supplied to the gate 14 via the series connections 32 and 34 according to the value, and the switch path. The voltage is limited to the maximum voltage 66. The maximum voltage 66 is a function of the resistance values of the resistors 16 and 22, and is a voltage from a constant voltage source. Since the resistance 16 is an NTC resistance and is thermally connected to the semiconductor chip of the IGBT 10, the resistance value of the resistance 16 changes as a function of the temperature of the semiconductor chip, that is, as a function of the temperature of the switch path 12. Depending on the circuit topology, the maximum voltage 66 also changes as a function of the temperature of the switch path 12. In this way, the maximum voltage 66 can be appropriately adjusted so that the active clamping function is improved.

The typical embodiments described above illustrate the methods of the invention and the principles of the control circuits of the invention. This is merely intended by the invention of the invention and is not intended to limit the invention. Of course, one of ordinary skill in the art will make appropriate changes as necessary without departing from the core idea of the present invention. Also, of course, the individual features can be combined with each other as desired and needed. Further, as a matter of course, the present invention is not limited to the IGBT, and can be applied to other switching elements, particularly a transistor having a switching operation. The same is true for clocked energy converters.

Moreover, the characteristics of the corresponding device are brought specifically to the characteristics of the method and vice versa.

Claims (8)

It is a method of controlling the semiconductor switch (10) in the switch mode.
The switch path (12) of the semiconductor switch (10) is switched on or off according to the switching potential applied to the control electrode (14) of the semiconductor switch (10). 12) is controlled by the switching potential.
In the switching process from the switch ON state to the switch OFF state of the switch path (12), the switch path voltage in the switch path (12) is measured, and when the switch path voltage reaches the maximum voltage, the switch path voltage is applied. The method of applying a limiting potential to the control electrode (14) to bring the switch path (12) into a conductive state in order to limit it to the maximum voltage.
The temperature of the switch path (12) is measured by a temperature sensor (96) thermally connected to the switch path (12) and the maximum voltage is determined as a function of the measured temperature.
When the value of the measurement signal from the temperature sensor (96) is evaluated and compared with the predetermined comparison value (28), and the measurement signal value is larger than the comparison value (28), the comparison signal (30). A method of overlaying the switching potential in the switch OFF state to supply the limiting potential . The method according to claim 1, wherein the switch path (12) operates by the limiting potential in a mode other than the switch mode. The method according to claim 1 or 2, when the switching edge of the switching potential reaches the maximum voltage, the switch is turned off from the switch ON state of at least the switch path (12) as a function of the switch path voltage. A method that is tuned during the switching process to state. A control circuit (44) for controlling a semiconductor switch (10).
The semiconductor switch (10) can be controlled via the control electrode (14), and the switch is turned on or off depending on the switching potential of the control electrode (14) of the semiconductor switch (10). The drive unit (20) can be connected to the control electrode (14) to provide the path (12) and apply the switching potential to the control electrode (14), and to measure the switch path voltage. A voltage sensor (18) that can be connected to the switch path (12) is provided.
The drive unit (20) applies a limiting potential to the control electrode (14) when the switch path voltage reaches the maximum voltage at least in the switching process from the switch ON state to the switch OFF state of the switch path (12). A control circuit that limits the switch path voltage to the maximum voltage by applying the switch path (12) to a conductive state.
The drive unit (20) comprises a temperature sensor (96) thermally connected to the switch path (12) to measure the temperature of the switch path (12) as a function of the measured temperature. It is configured to determine the maximum voltage (66).
The drive unit (20) includes a comparison circuit (26) to which the temperature sensor (96) is connected, and the comparison circuit (26) evaluates the value of the measurement signal from the temperature sensor (96). The measurement signal value is compared with a predetermined comparison value (28), and when the measurement signal value is larger than the comparison value (28), the comparison signal (30) is transmitted to the drive unit (20). Being done
The drive unit (20) is a control circuit configured to overlay the comparison signal (30) on the switching potential in the switch OFF state in order to supply the limiting potential . The control circuit according to claim 4, wherein the temperature sensor (96) includes at least two electric resistances (16, 22) arranged in series, and the electric resistance value of at least one of the resistances (16). Is a control circuit that changes as a function of the temperature. The control circuit according to claim 5, wherein the electrical resistance (16) that changes as a function of the temperature is an NTC resistance or a PTC resistance. The control circuit according to any one of claims 4 to 6 , wherein the drive unit (20) is connected in series (32, 34) including an electric resistance (36, 38) and a diode (40, 42). Equipped with
The series connection (32, 34) is a control circuit in which one terminal is connected to the control electrode (14) and the other terminal is connected to the comparison circuit (26). It comprises a first electrical terminal, a second electrical terminal, at least one semiconductor switch (10), and a control circuit connected to a control electrode (14) of the at least one semiconductor switch (10).
A clocked energy converter configured to control the semiconductor switch (10) in order to electrically connect the first electric terminal and the second electric terminal.
A clocked energy converter in which the control circuit includes the control circuit (44) according to any one of claims 4 to 7 .

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