Switching module

Abstract

[Problem] To provide a switching module that can achieve high-speed switching of GaN-FETs even with a simple and inexpensive configuration. [Solution] A switching module includes: a GaN-FET mounted on a substrate, a driving circuit connected to the gate electrode of the GaN-FET through a gate resistor, and a driving power supply that provides a driving voltage to the driving circuit; wherein the driving circuit has a configuration of connecting a plurality of logic IC circuits in parallel.

Description

[Technical Field]

[0001] The present invention relates to a switching module applicable to D-class amplifiers, etc., and particularly to a switching module comprising: a GaN-FET mounted on a substrate, a drive circuit connected to the gate electrode of the GaN-FET through a gate resistor, and a drive power supply for providing a drive voltage to the drive circuit. [Previous Technology]

[0002] High-frequency power supplies are power sources suitable for generating ultrasonic oscillations, induced current, or plasma, etc., and have the function of converting DC to high-frequency AC through the switching operation of a D-class amplifier. The D-class amplifier that performs this switching operation is characterized by high power efficiency and low heat generation. As a module containing power semiconductors that perform its switching operation, the use of FET (Field Effect Transistor) is widely known.

[0003] Conventional FETs, such as junction FETs and MOS FETs, are capable of high-speed control of the current flowing between the source and drain electrodes in response to the signal input to the gate electrode. In recent years, in pursuit of even faster switching speeds (high-frequency switching), GaN-FET devices using GaN (gallium nitride) have become increasingly used.

[0004] As a switching module using such a GaN-FET, for example, Patent Document 1 discloses a switching power supply that performs packet tracking drive on a transmitting amplifier based on the waveform of an input signal. This power supply includes: a transformer to which the input signal is input to the primary side; first to third switching sections connected to the secondary side of the transformer; an acceleration circuit with a resistor and capacitor connected in parallel; a Schottky diode with its anode grounded; and a power FET with its gate connected to the resistor and its source connected to the cathode of the Schottky diode. The first to third switching sections each have: a gate and a source connected to... The transformer's secondary side circuit includes an internal FET, an internal Schottky diode with its cathode connected to the gate of the internal FET, a Zinner diode with opposite polarity connected in series with the internal Schottky diode and its cathode connected to the source of the internal FET, and a capacitor connected in parallel with the Zinner diode; the source of the internal FET in the first switching section, the drain of the internal FET in the second switching section, and a resistor; the drain and source of the internal FET in the third switching section are connected in parallel with the acceleration circuit; the aforementioned power supply FET is an N-channel GaN-FET with a normally closed gate having a Schottky junction. With such a switching power supply, a high-efficiency, high-speed, high-amplitude switching power supply and switching method for high-frequency transmitters can be provided. [Previous Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2012-186563 [Summary of the Invention]

[0006] [The problem the invention aims to solve]

[0007] Compared to silicon in conventional MOS-FETs, GaN materials used in GaN-FETs have a wider bandgap and lower on-resistance. Furthermore, as a switching element, it has the advantage of operating at high speeds and high temperatures. As one example, GaN-FETs can operate at speeds that are more than 4 times faster in terms of voltage change (dV / dt) and more than 10 times faster in terms of current change (dI / dt) compared to conventional MOS-FETs.

[0008] During high-speed switching operations, the rise or fall of the gate current input to the gate electrode becomes steep. The gate current accompanying such a steep change is easily affected by the parasitic components of the FET, which can cause surges or ripples.

[0009] Therefore, when using GaN-FETs as switching modules, in order to suppress the generation of surges or ripples that accompany high-speed operation, a special gate drive circuit must be designed to input the gate current at the appropriate timing. For example, in Patent Document 1, a special circuit comprising a transformer, a Schottky diode, a Zener diode, and a capacitor is configured between the broadband driver that generates the gate current and the switching element.

[0010] However, when using diodes to rectify signals from the driver, such as Schottky diodes, leakage current occurs at high temperatures, so the operating ambient temperature must be lowered. On the other hand, because Zener diodes have reverse characteristics, they must be connected in parallel with a capacitor to speed up the response. Therefore, the gate drive circuit used to drive GaN-FETs has a complex configuration problem.

[0011] This invention was created to solve the aforementioned problems of conventional technology, and its purpose is to provide a switching module that can achieve high-speed switching of GaN-FETs even with a simple and inexpensive configuration. [Means of Solving the Problem]

[0012] In order to solve the above-mentioned problems, one of the representative embodiments of the present invention is a switching module, comprising: a GaN-FET mounted on a substrate, a driving circuit connected to the gate electrode of the GaN-FET through a gate resistor, and a driving power supply that provides a driving voltage to the driving circuit; wherein the aforementioned driving circuit has a configuration of connecting a plurality of logic IC circuits in parallel.

[0013] According to the present invention having such a configuration, by connecting the drive circuit that inputs the gate current to the gate electrode of the GaN-FET in parallel to a plurality of logic IC circuits, high-speed switching of GaN-FET can be achieved even with a simple and inexpensive configuration.

Implementation Method

[0015] Hereinafter, using Figures 1 to 5, specific examples of the switching module of the present invention will be described.

[0016] <Example 1> FIG1 is a block diagram of a high-frequency power supply device for an amplifier, applying the switching module of Example 1, a representative example of the present invention. FIG2 is a circuit diagram showing the equivalent connection circuit near the module of the switching module shown in FIG1. ​​Furthermore, FIG3 is a block diagram showing the outline of the drive power supply and drive circuit shown in FIG1. ​​Such a high-frequency power supply device is used, for example, in semiconductor manufacturing apparatuses where the amplifier output is 1kW or more and the output frequency is 0.3MHz or more.

[0017] As shown in Figure 1, the high-frequency power supply device 1 that appropriately uses the switching module of Embodiment 1 is one example, including: a DC power supply 10 that supplies the DC voltage for switching, a switching module 100H connected to the input terminal of one side (high side) of the DC power supply 10, a switching module 100L connected to the input terminal of the other side (low side) of the DC power supply 10, and a control unit 20 that outputs drive signals to these switching modules 100H and 100L.

[0018] Here, Figure 1 illustrates a high-frequency power supply device configured with a so-called half-wave bridge circuit including a pair of switching modules. However, it can also be configured as a high-frequency power supply device with a full-wave bridge circuit including two pairs of switching modules. Since switching modules 100H and 100L have the same configuration, in the following specific embodiments, only the configuration of the high-side switching module will be described, and the description of the low-side switching module will be omitted.

[0019] The switching module 100H of Embodiment 1 includes: a GaN-FET 120H mounted on a substrate 110H, a driving circuit 130H connected to the gate electrode G of the GaN-FET 120H via a connecting wire 140H, and a driving power supply 150H that provides driving voltage to the driving circuit 130H. As shown in FIG1, the control unit 20 is electrically connected to the high-side driving circuit 130H and the low-side driving circuit 130L via signal lines 22H and 22L, and outputs driving signals DsH and DsL to these driving circuits 130H and 130L respectively.

[0020] The substrate 110H is one example, and it is formed of a material with good thermal conductivity, such as beryllium oxide (BeO) or aluminum nitride (AlN). In this way, the heat generated during the driving of the module can be effectively diffused or dissipated.

[0021] The GaN-FET120H is a type of field-effect transistor (FET) device that uses GaN to form the current flow path. It is a power semiconductor with a "horizontal" structure in which the gate electrode G, source electrode S, and drain electrode D are located on the same plane. With this structure, the GaN-FET120H can achieve a switching speed higher than that of a conventional MOSFET.

[0022] The drive circuit 130H, as shown in FIG3, is configured to have a logic IC circuit composed of a plurality of TTL elements 132H1, 132H2, and 132H3 connected in parallel. FIG3 illustrates a case with three TTL elements 132H1 to 132H3; however, in this invention, the number of logic IC circuits can be arbitrary, as long as a plurality of them are connected in parallel.

[0023] One example of the connection wiring 140H system is a configuration comprising a bonding conductor BW made of gold, copper, or aluminum cable and a gate resistor Rg. As shown in Figure 3, this connection wiring 140H system, as an equivalent electrical connection circuit, simulates a configuration containing a gate resistor Rg, a floating inductance Ls, and an impedance component Rs. In this case, by selecting the impedance value of the gate resistor Rg based on the parasitic capacitance of the GaN-FET 120H, the attenuation rate of the gate-source voltage Vgs applied from the gate electrode G can be controlled.

[0024] The drive power supply 150H, as one example, includes: an inverter 152H that converts the input from a DC power supply to AC, a transformer 154H that transforms the AC input from the inverter 152H, and a converter 156H that converts the AC input from the transformer 154H back to DC. The output current from the converter 156H is input in parallel to each of the TTL elements 132H1 to 132H3 of the drive circuit 130H.

[0025] In the switching module 100H of the present invention, a GaN-FET 120H is used as the switching element. As a result, compared with a general MOSFET, the gate current IgH input to its gate electrode G from the drive circuit 130H can be reduced. As an example, when using a conventional silicon substrate MOSFET, the input capacitance Ciss is large (about 600~3000pF). Moreover, in order to use the device in the saturation region of the high-frequency band (e.g. 13.56MHz), the necessary gate voltage Vgs is also high (e.g., 12V or more). Therefore, the power supplied by the drive power supply for driving the drive circuit also needs to be large (e.g., 10W or more).

[0026] In contrast, the GaN-FET120H system used in Example 1 is smaller than that of a typical MOSFET (approximately 150~300pF). Furthermore, because the necessary gate voltage Vgs is 5V or less for use in the saturation region, the supply voltage of the drive power supply 150H can be approximately 1~2W. Moreover, because the GaN-FET system can be driven at high speeds compared to conventional silicon-based MOSFETs, the shift voltage slope (dV / dt) of the drain-source voltage Vds is larger (e.g., 100V / ns). Therefore, during high-speed driving, there is a possibility of switching malfunctions on the high-side, so it is desirable that the junction capacitance of the drive power supply supplying the gate voltage be as small as possible (e.g., 5pF or less).

[0027] In this embodiment 1, the transformer 154H of the drive power supply 150H is formed as shown in FIG3 as a coreless transformer having a pair of air-core coils 155H1 and 155H2. This reduces the size of the transformer 154H and the power supply capacity, and also reduces the combined capacitance of the power supply. Consequently, the overall footprint (area) of the transformer power supply can be reduced.

[0028] Next, the switching operation of the GaN-FET in the switching module 100H of Embodiment 1 shown in Figures 1 to 3 will be described.

[0029] For example, in the high-frequency power supply device 1 shown in FIG1, either the switching module 100H or 100L is switched on, thereby outputting the input from the DC power supply 10 as a high-frequency voltage VF. At this time, the control unit 20 sends the drive signal DsH or DsL used to drive the switching module 100H or 100L to either module via signal lines 22H and 22L.

[0030] As shown in Figure 2, the drive circuit 130H outputs a gate current IgH through the connection wiring 140H while receiving the drive signal DsH. The GaN-FET 120H, which receives the gate current IgH at the gate electrode G, becomes active, outputting the power input from the input terminal Vin to the output terminal Vout. By repeatedly performing this operation, the switching operation of the switching modules 100H and 100L on the high-side and low-side is executed.

[0031] As shown in Figure 3, in the drive circuit 130H of Embodiment 1, TTL elements 132H1~132H3 connected in parallel to the voltage from the drive power supply 150H form a logic IC circuit. At this time, the drive signal DsH from the control unit 20 is input to the TTL elements 132H1~132H3 connected in parallel, and gate currents Ig1~Ig3 are output from each element. These gate currents Ig1~Ig3 combine on the downstream side to become the gate current IgH.

[0032] Therefore, even if the output levels of the gate currents Ig1 to Ig3 from each TTL element 132H1 to 132H3 are small, the gate current IgH output from the drive circuit 130H can still be the desired level as the combined current of multiple gate currents. Furthermore, as the logic circuit constituting the logic IC circuit, any type such as AND circuit, OR circuit, or buffer circuit can be appropriately used.

[0033] The specific configuration of the switching module 100H in Embodiment 1 can be illustrated by the following examples.

[0034] For example, at a switching frequency of 13.56 MHz, the necessary gate drive power for the switching operation of the GaN-FET 120H illustrated in Example 1 is approximately 0.1 W. To obtain such gate drive power, it is sufficient to connect approximately 2 to 3 TTL elements 132H1 to 132H3 shown in FIG3 in parallel.

[0035] On the other hand, as mentioned above, even if the gate drive power of the GaN-FET 120H is large, it is only about a few W. Therefore, for the insulating transformer used to provide drive power to the drive power supply 150H of the drive circuit 130H, for example, for the air-core coils 155H1 and 155H2, using a material with a dielectric constant ε=1, the size of the coil diameter is suppressed to about 20 mm and the coil spacing is about 1 mm. In this way, the capacitance CtH between the windings of the air-core coils 155H1 and 155H2 can be suppressed to below 5 pF.

[0036] Furthermore, if a material with a dielectric constant ε higher than 1 is used as the material for the air-core coils 155H1 and 155H2, the coil diameter can be further reduced. Moreover, in Figure 3, a circular example is shown for the air-core coils 155H1 and 155H2, but the shape of the coil can also be polygonal, and the winding ratio can be arbitrarily selected.

[0037] With the above-described configuration, the switching modules 100H and 100L of Embodiment 1 are connected in parallel to the drive circuits 130H and 130L of the gate electrode G of GaN-FET 120H and 120L via the input gate currents IgH and IgL to a logic IC circuit composed of a plurality of TTL elements 132H1 to 132H3. Even with a simple and inexpensive configuration, high-speed switching of GaN-FET can be achieved.

[0038] <Example 2> Figure 4 is a block diagram showing the outline of the drive power supply and drive circuit of the switching module of Example 2. Here, in the switching module of Example 2, the same component symbols as in Example 1 are given to components that have the same or identical components as in Example 1, and further descriptions are omitted.

[0039] In the switching module 100H of Embodiment 2, the driving circuit 230H, as one example, as shown in FIG4, has a configuration of a logic IC circuit composed of a plurality of CMOS elements 232H1, 232H2, and 232H3 connected in parallel. Furthermore, similar to Embodiment 1, FIG4 illustrates a case with three CMOS elements 232H1 to 232H3; however, as long as a plurality of elements are connected in parallel, the number of logic IC circuits can be arbitrary.

[0040] In the driving circuit 230H of Embodiment 2, CMOS elements 232H1~232H3 connected in parallel to the voltage from the driving power supply 150H form a logic IC circuit. At this time, the driving signal DsH from the control unit 20 is input to the parallel-connected CMOS elements 232H1~232H3, and gate currents Ig1~Ig3 are output from each element. These gate currents Ig1~Ig3 combine on the rear side to become the gate current IgH.

[0041] Therefore, similar to the case in Figure 3, even if the output levels of the gate currents Ig1 to Ig3 from each CMOS element 232H1 to 232H3 are small, the gate current IgH output from the drive circuit 230H can still reach the desired level as a composite current of multiple gate currents. Since the power consumption of a typical CMOS element to obtain the same level of output is less than that of a TTL element, the drive circuit 230H of this modified example can further reduce the power consumption of the drive power supply 150H.

[0042] By having the above-described configuration, the switching modules 100H and 100L of Embodiment 2, in addition to the effects obtained by the switching module of Embodiment 1, can further simplify the structure of the drive power supply by using CMOS elements to construct the logic IC circuit. As a result, the overall size of the switching module can be miniaturized.

[0043] <Example 3> Figure 5 is a block diagram showing the outline of the drive power supply and drive circuit of the switching module of Example 3. Here, as in Example 2, in the switching module of Example 3, the same component symbols as in Example 1 are given to components that have the same or identical components as in Example 1, and further explanation is omitted.

[0044] As explained in Example 1, GaN-FETs are prone to switching malfunctions on the high-side during high-speed driving. Therefore, it is desirable to minimize the capacitance of the drive power supply that supplies the gate voltage (e.g., 5pF or less). In Example 3, a light-emitting device combining a light-emitting element and a photoelectric converter is used as the drive power supply.

[0045] That is, as shown in FIG5, in the switching module 100H of Embodiment 3, the driving power supply 350H is one example, which includes a light-emitting element 352H that emits light through input from a DC power supply, a light transmission mechanism 354H that transmits the light emitted from the light-emitting element 352H, and a photoelectric converter 356H that converts the transmitted light into electricity. Then, the electricity output from the photoelectric converter 356H is input to each of the plurality of parallel-connected TTL elements 132H1 to 132H3 of the logic IC circuit that serves as the driving circuit 130H.

[0046] The light-emitting element 352H, as one example, is configured to emit light when a semiconductor laser (LD) or light-emitting diode (LED) is powered on. This allows for a smaller drive power supply 350H and reduces the power consumption of the DC power supply. Furthermore, corresponding to the configuration of the photoelectric converter 356H described later, the light-emitting element 352H can also be appropriately used with light-emitting means such as lamps.

[0047] When the transmitted light is highly directional, such as laser light, the transmission mechanism 354H can appropriately use an optical system such as a lens arranged in the optical path or a transmission path such as an optical fiber. In particular, when the transmission mechanism 354H is constructed with an optical fiber, an insulated power supply can be constructed to suppress the capacitance CtH between the light-emitting element 352H and the photoelectric converter 356H to below 1pF by adjusting its fiber length. Moreover, by using optical fiber to transmit light, the light-emitting element 352H can be configured as a separate entity from the switching module 100H, which simplifies the overall configuration of the module.

[0048] The photoelectric converter 356H is one example, which can be configured to convert the input light energy of semiconductor elements such as photodiodes or photocrystals, or photovoltaic cells, into electricity. In this case, by shortening the distance between the light-emitting element 352H and the photoelectric converter 356H, the transmission mechanism 354H can be omitted and the power can be transmitted through the space between the two.

[0049] By having the above-described configuration, the switching modules 100H and 100L of Embodiment 3, in addition to the effects obtained in the switching module of Embodiment 2, reduce the driving power consumption of the driving power supply itself by configuring the driving power supply 150H and 150L as a light power supply device. As a result, the overall size of the switching module can be reduced. Furthermore, by adjusting the distance between the light-emitting element 352H and the photoelectric converter 356H, the power supply capacitance between them can be minimized, thereby suppressing malfunctions of the GaN-FET 120H.

[0050] Furthermore, the descriptions in the above embodiments are merely examples of switching modules related to the present invention, and the present invention is not limited to the implementation methods of each embodiment. Moreover, those skilled in the art can make various modifications without departing from the spirit of the present invention, and these modifications are not excluded from the scope of the present invention. [Simplified Explanation of the Diagram]

[0014] [Figure 1] is a block diagram of the switching module of Embodiment 1 applied to the high-frequency power supply device of the amplifier. [Figure 2] is a circuit diagram showing the equivalent connection circuit near the module of the switching module shown in Figure 1. [Figure 3] is a block diagram showing the outline of the driving power supply and driving circuit shown in Figure 1. [Figure 4] is a block diagram showing the outline of the driving power supply and driving circuit of the switching module of Embodiment 2. [Figure 5] is a block diagram showing the outline of the driving power supply and driving circuit of the switching module of Embodiment 3.

Claims

1. A switching module, comprising: a GaN-FET mounted on a substrate, a driving circuit connected to the gate electrode of the GaN-FET through a gate resistor, and a driving power supply providing a driving voltage to the driving circuit; wherein, The aforementioned driving circuit comprises: a plurality of logic IC circuits connected in parallel; the aforementioned driving power supply includes: a coreless transformer with an air-core coil; the aforementioned air-core coil is made of a material with a dielectric constant higher than 1, and the capacitance between the windings is less than 5pF.

2. As in request item 1, the switching module, where, The aforementioned logic IC circuits are composed of TTL or CMOS components.

Images