The invention is dedicated to a control circuit for at least two drivers where the drivers are each configured to switch on and off electrically driven switching elements which are electrically connected to each other.

The invention is dedicated also to a switching unit and to a switching system comprising such a control circuit.

The invention is dedicated also to a power supply system and a plasma system comprising a switching unit or a switching system.

When switching elements are connected to each other it is often very important to switch them on and off simultaneously. It is a challenge to drive the switching elements individually exactly in such a way that they are changing their on -off- resista nee at the same time. In case of high voltage switching very often serial connected switching elements are used. This switching elements should be switched on and off at the same time. If one switching element is late in switching on, it has to carry the full high voltage for which it is often not designed. It is a further challenge that switching elements do not always have the same delay time from getting the signal to switch on to the output really being switched on. So, switching elements must be driven with an individual driving signal which should compensate the differences of different delay times.

This is also a challenge in power supplies with RF-output at high voltages. Such power supplies often work with switching elements. For example, in a switched push-pull amplifier or in a switched bridge amplifier the power transistors connected together need to be switched in an extremely synchronized manner.

It is an object of this invention to generate pulses to switch on and off electrically driven switching elements precise, stable and repeatable. The object is solved by a control circuit according to claim 1 and/or by a switching unit according to claim 11, a switching system according to claim 15, a power supply system according to claim 16 and/or a plasma system according to claim 17. Further preferred aspects of the invention are covered by the dependent claims and the description.

In one aspect of the invention a control circuit for at least two drivers is disclosed, the drivers are each configured to switch on and off electrically driven switching elements which are electrically connected to each other, the control circuit comprises:

- a first parallel-to-serial-converter comprising a first parallel input port and a first serial output-port connectable to a first driver,

- a second, in particular identical, parallel-to-serial-converter comprising a second parallel input port and a second serial output-port connectable to a second driver,

- a processor unit configured to

- send a first data package stream to the first parallel input port and

- send a second data package stream to the second parallel input port, where

- the both package streams are configured to be converted, in particular by the parallel-to-serial-converter, to serial-data-streams at the outputports and

- the serial data-streams are configured to control the drivers.

In a further aspect of the invention the control circuit may comprise or is built as a logical programmable unit, in particular a field programmable gate array (FPGA). The logical programmable unit, in particular the FPGA, may comprise the processor unit. The logical programmable unit, in particular the FPGA, may comprise the first and second parallel-to-serial-converter.

The invention is based on the use of gigabyte transceivers with built-in parallel-to-serial-converters built into the FPGA system, originally designed for fast communication. These transceivers and their parallel-to-se- rial-converters work at a very high frequency at their outputs in the order of one to several GHz. Processing such fast signals would be very difficult with standard integrated circuits. The transceivers built into the FPGA comprise these dedicated serializer blocks. Due to the high serialization factor, the frequency with which data must be processed is significantly reduced. Appropriate FPGA software enables generating the desired control waveforms.

In a further aspect of the invention the control circuit may comprise a non-volatile memory with a computer readable program in this memory, the program executable by the processor unit, where the program is configured to force the processor unit to generate the first and second data package stream.

In a further aspect of the invention the control circuit may comprise a system clock generator configured to generate a system clock, where the frequency of the serial-data-streams at the output-ports may be higher than the frequency of the system clock.

In a further aspect of the invention the control circuit may be configured to adjust time parameters such as phase, pulse width, frequency and dead time of the electrically driven switching elements.

The time parameters such as phase, pulse width, frequency and dead time may be driven within time-intervals which are smaller than the time interval of the system clock, in particular 2 times or more than 2 times smaller, in particular 4 times or more than 4 times smaller, in particular 8 times or more than 8 times smaller, in particular 16 times or more than 16 times smaller, in particular 32 times or more than 32 times smaller, in particular 64 times or more than 64 times smaller.

In a further aspect of the invention the control circuit may comprise a built-in transceiver. This built-in transceiver may comprise one of the par- allel-to-serial-converters. In a further aspect of the invention the control circuit may comprise a built-in serializer-deserializer unit which is preferably built in the transceiver. This built-in serializer-deserializer unit may comprise one of the parallel-to-serial-converters.

In a further aspect of the invention the control circuit may comprise multiple transceivers and/or multiple serializer-deserializers.

In a further aspect of the invention the multiple transceivers and/or multiple serializer-deserializers may be clocked by the same system clock.

In a further aspect of the invention the first and second data package stream may be configured such that the electrically driven switching elements are synchronized at their outputs.

In a further aspect of the invention the control circuit may comprise a data interface configured to get data from an external data processing device.

In a further aspect of the invention a switching unit may comprise at least two electrically driven switching elements, and

- at least two drivers, the drivers are each configured to switch on and off the electrically driven switching elements which are electrically connected to each other, and

- a control circuit as described in this disclosure.

In a further aspect of the invention the switching unit may comprise at least two control circuits as described in this disclosure, in particular drivable or driven by one identical system clock.

In a further aspect of the invention the switching system may comprise a switching unit as described in this disclosure and an external data processing device. In a further aspect of the invention the switching system may comprise a switching unit as described in this disclosure and an external clock generator.

In the figures some examples of the invention are shown schematically and described in more detail in the following description. The figures show:

Fig. 1 Switching unit with a control circuit according to the invention.

Fig. 2 Time diagrams comprising data package streams.

Fig. 3 Switching system with two control circuits according to the invention.

Fig. 4 A more detailed view of a switching system.

Fig. 5 A plasma system with a power supply system comprising a switching system.

In Fig. 1 is shown a switching unit 100 comprising at least two electrically driven switching elements 12, 13 and at least two drivers 10, 11, the drivers are each configured to switch on and off the electrically driven switching elements 12 13 which are electrically connected to each other with a connection 17.

The switching elements may be transistors, in particular MOSFETs. They may be built as VMOS or LDMOS transistors. They may be built as Si- based transistors or SiC-, or GaN-based transistors to be able to switch high power and high voltage.

The switching unit 100 further comprises a control circuit 1. The control circuit 1 comprises a first parallel-to-serial-converter 2 and a second par- allel-to-serial-converter 3. The first parallel-to-serial-converter 2 comprises a first parallel input port 4 and a first serial output-port 6 connectable to a first driver 10. The second parallel-to-serial-converter 3 comprises a second parallel input port 5 and a second serial output-port 7 connectable to a second driver 11.

The control circuit 1 further comprises a processor unit 8. The processor unit 8 may be configured to send a first data package stream 21 (example shown in Fig. 2) to the first parallel in-put port 4 and send a second data package stream 22 to the second parallel input port 5.

The both package streams 21, 22 are configured to be converted by both parallel-to-serial-converters 2, 3 to serial-data-streams 23, 24 at the out- put-ports 6, 7. The serial data-streams 23, 24 are configured to control the drivers 10, 11.

The control circuit 1 comprises a non-volatile memory 15. This memory 15 may comprise a computer readable program. The program may be executable by the processor unit 8. The program is configured to force the processor unit 8 to generate the first and second data package stream 21, 22.

The control circuit further comprises a system clock generator 9. This system clock generator 9 may be configured to generate a system clock 29. The frequency of the serial-data-streams 23, 24 at the out-put-ports 6,7 may be higher than the frequency of the system clock 29. In particular, the time shift of the serial-data-streams 23, 24 at the out-put-ports 6,7 may be in shorter time intervals than the frequency of the system clock 29, in particular 2 times or more than 2 times shorter, in particular 4 times or more than 4 times shorter, in particular 8 times or more than 8 times shorter, in particular 16 times or more than 16 times shorter, in particular 32 times or more than 32 times shorter, in particular 64 times or more than 64 times shorter.

The control unit 1 comprises a data interface 14 configured to get data from an external data processing device 31 (shown in Fig, 3 and 4). To generate the control waveforms, a FPGA system was used, equipped with built-in gigabyte transceivers enabling sending and receiving data at a very high frequency. Such a transceiver has in its architecture a serializer, also called parallel-to-serial-converter 2, 3, and deserializer with adjustable data package length. The deserializer may be unused in this configuration. Most systems currently available on the market have a maximum serialization factor of 64. For a correct operation, a serializer operating at a certain frequency needs to provide input data at a frequency reduced by a serialization factor, for example: if the serializer operating frequency is 5 GHz and serialization factor is 64 the system clock needs only to be 5000 MHz/64 = 78,125 MHz. This allows data to be processed at a much lower frequency than the output signal is generated. By clocking multiple transceivers from the same system clock 29 and starting the serialization process at the same time, synchronization between multiple outputs is ensured. By providing the appropriate data on the serializer, one can get the desired signal at the output. The data source can be a software data generator or one of the deserializer inputs working with the same clock. The signal source for the receiver can be a signal from a digi- tal-to-analog converter to which samples are generated inside the FPGA system or from another independent device. The externally reference signal applied to many FPGAs allows easy synchronization between signals generated by many FPGAs. The choice of reference data source can be selected at any time. In order to obtain the set parameters of the output signals such as filling, phase shift and dead time, the data before feeding to the serializer should be properly processed. The processing process involves changing the value of '1' to 'O' or 'O' to '1' in subsequent data packages of data from the source of the pattern. Data packages can also be rewritten by the appropriate number of registers by the desired value. In this way, one may shift the signal in time and extend or shorten the pulse duration for each output signal independently.

In Fig. 2 this is shown in one example. In the first time diagram the system clock 29 is shown. With each rising edge of the system clock a data package stream 21 is written into the parallel-to-serial-converter 2. Here are shown two different data package streams 21a and 21b Data package stream 21a with 0 0 1 1 1 1 1 1;

Data package stream 21b with 1 1 1 1 1 0 0 0; These both data package streams 21a, 21b are serialized by the parallel- to-serial-converter 2 to the converted serial-data-stream 23, which is shown in Fig. 2 second diagram.

In the third diagram again the same system clock 29 is shown. With each rising edge of the system clock a data package stream 22 is written into the parallel-to-serial-converter 3. Here are shown two different data package streams 22a and 22b

Data package stream 22a with 0 0 0 1 1 1 1 1;

Data package stream 22b with 1 1 1 1 1 1 1 0;

These both data package streams 22a, 22b are serialized by the parallel- to-serial-converter 3 to the converted serial-data-stream 24, which is shown in Fig. 2 forth diagram.

Data package stream 22a is different from data package stream 21a. Data package stream 22b is different from data package stream 21b. Therefore the converted serial-data-stream 24 is different from the converted serial-data-stream 23, which can be seen with the dotted lines from the second to the fourth diagram.

So, in this example, the rising edge of the serial-data-stream 24 is delayed by one time interval and the falling edge serial-data-stream 24 is delayed by two time intervals. These time intervals are much smaller than the system clock 29. A very accurate driver signal may be generated in this way.

In Fig. 3 is shown a switching system 101 with two control circuits 1' and 1". All reference numbers of Fig. 1 are used here with additional apostrophes and have the same meaning, respectively.

The switching system 101 comprises two switching units 100', 100" as described in this document and an external data processing device 31. The external data processing device 31 may exchange data via the data interfaces 14', 14".

The system clock generators 9', 9" are here externally triggered by an external clock generator 39.

In Fig. 4 is shown a more detailed view of a switching system 101 with a control circuit 1, which may be a FPGA. All reference numbers of Fig. 1 are used here and have the same meaning, respectively. The control unit 8 is here shown in two parts with an arithmetic unit 8a and a processing unit 8b. The control unit 1 of this example comprises more than two of the parallel-to-serial-converters 2, 3 which is shown by several additional par- allel-to-serial-converters 2a, 2b, 2c.

The control unit 1 of this example further comprises a parameter controller 41. With such a parameter controller 41 it is possible to receive parameter values from the CPU and assign them to appropriate processing functions.

The control unit 1 of this example further comprises a sine data generator 42. With such a data generator 42 it is possible to generate reference signal samples at a selected frequency.

The switching system 101 of this example further comprises a Digital-to- Analog Converter (DAC) 43 connected to the sine data generator 42. With such a DAC 43 it is possible to convert a digital signal to an analog signal. The generated analog signal may be used as a reference source in particular after filtering out the unwanted spectrum harmonics of the analog signal.

The switching system 101 of this example further comprises a filter 44 connected to the output of the Digital-to-Analog Converter 43 in order to suppress unwanted harmonics of the signal to form a precise sine-signal. This sine-signal is leaded to a comparator 44 which generates a rectangular, digital signal. This signal is leaded to a deserializer 47 in the control circuit 1.

The control unit 1 of this example further comprises a second deserializer 48 for signals coming from another device 46. With such a device 46 it is possible to add synchronization to a further device instead of an analog reference signal.

The invention may be implemented using FPGA with built-in transceivers capable of operating at a maximum frequency of 17 GHz. Due to the desired resolution of output parameters adjustment, the parallel-to-serial- converters may be clocked at 10 GHz, which gives a resolution of 100 ps. With a serialization factor of 64, the frequency of processing and delivering data to the serializer may be then at about 156,25 MHz, which may be then also the frequency of the system clock 29. The FPGA may be connected to the external data processing device 31 (computer) to allow easy parameter setting from the computer's software. The processing algorithm in the FPGA gets parameter settings from the CPU and then modifies the input reference data for each output independently. The reference data source is selected between software data generator and signals from two deserializers 47, 48 where receivers are connected to an external junction (for other devices) and compared with digital to analog converter 43. Source data for digital to analog converter 43 may be in the FPGA software.

In Fig. 5 is shown a plasma system 500 comprising a power supply system 501 and a plasma process unit 503. The power supply system 501 may be a power supply system with an R.F output signal to supply power with more than 1 kW and frequencies higher than 1 MHz to the plasma process unit 503. The plasma process unit 503 may be used for deposition, etching or treating atomic layers in processes like semiconductor manufacturing or glass coating or display manufacturing. Between the power supply system 501 and a plasma process unit 503 an optional impedance matching unit 502 may be placed and connected in order to match the output impedance of the power supply system 501 to the input impedance of the plasma process unit 503. The power supply system 501 comprises an aforementioned switching unit 100 and/or a switching system 101. Such a switching unit 100 and/or a switching system 101 may be used in extremely advantageous way in such a plasma system 500.