Switching Module

Abstract

To provide a switching module that can realize high-speed switching by GaN-FET even with a simple and inexpensive configuration.SOLUTION: A switching module includes a GaN-FET mounted on a substrate, a driver circuit connected to a gate electrode of this GaN-FET via a gate resistor, and a driver power supply that gives a drive voltage to this driver circuit, and the driver circuit has a configuration in which a plurality of logic IC circuits are connected in parallel.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a switching module applied to a class-D amplifier or the like, and in particular to a switching module including a GaN-FET mounted on a substrate, a driver circuit connected to the gate electrode of the GaN-FET via a gate resistor, and a driver power supply that provides a drive voltage to the driver circuit. [Background technology]

[0002] High-frequency power supplies are used as power sources for generating ultrasonic waves, induced power, plasma, etc., and have the function of converting direct current into high-frequency alternating current through the switching operation of a class-D amplifier. Class-D amplifiers that perform this type of switching operation are characterized by high power efficiency and low heat generation, and modules that use field-effect transistors (FETs) are known as modules that include power semiconductors that perform this switching operation.

[0003] Junction FETs and MOS FETs are known as FETs capable of performing such switching operations, and can control the current flowing between the source and drain electrodes at high speed in response to a signal input to the gate electrode. In recent years, GaN-FET elements using GaN (gallium nitride) have been increasingly used in order to further increase the speed of switching operations (high-frequency switching).

[0004] As an example of a switching module using such a GaN-FET, Patent Document 1 discloses a switching power supply that performs envelope tracking drive of a transmission amplifier based on the waveform of an input signal, and includes a transformer to which the input signal is input on its primary side, first to third switching units connected to the secondary side of the transformer, a speed-up circuit having a resistor and a capacitor connected in parallel, a Schottky diode with its anode grounded, and a power supply FET whose gate is connected to the resistor and whose source is connected to the cathode of the Schottky diode, and the first to third switching units include an in-circuit FET whose gate and source are connected to the secondary side of the transformer, The power supply includes an in-circuit Schottky diode whose cathode is connected to the gate of the in-circuit FET, a Zener diode connected in series with the in-circuit Schottky diode in reverse polarity and whose cathode is connected to the source of the in-circuit FET, and a capacitor connected in parallel to the Zener diode, the source of the in-circuit FET of the first switching unit is connected to the drain of the in-circuit FET of the second switching unit, and a resistor is connected, and the drain and source of the in-circuit FET of the third switching unit are connected in parallel to a speed-up circuit, and the power supply FET is a normally-off N-channel GaN-FET with a Schottky junction gate. Such a switching power supply is said to provide a high-efficiency, high-speed, large-amplitude switching power supply and switching method for high-frequency transmitters. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-186563 Summary of the Invention [Problem to be solved by the invention]

[0006] The GaN material used in GaN-FETs has a wider bandgap and lower on-resistance than the silicon used in general MOS-FETs, and is also advantageous as a switching element in that it can operate at high speeds and high temperatures. For example, GaN-FETs are said to be capable of operating at voltage changes (dV / dt) four times faster and current changes (dI / dt) ten times faster than regular MOS-FETs.

[0007] When switching speed is increased, the gate current input to the gate electrode rises or falls sharply. Such a steeply changing gate current is easily affected by parasitic components in the FET, which can cause surges and ringing.

[0008] For this reason, when applying GaN-FETs as switching modules, it is necessary to design a special gate drive circuit for inputting gate current at an appropriate timing in order to suppress surges, ringing, and other issues that accompany high speeds. For example, Patent Document 1 also has a configuration in which a special circuit including a transformer, Schottky diode, Zener diode, and capacitor is interposed between a wideband driver that generates gate current and the switching element.

[0009] However, when using diodes to rectify signals from the driver, for example, Schottky diodes generate leakage current at high temperatures, so the operating temperature must be lowered. On the other hand, Zener diodes have reverse characteristics, so they must be connected in parallel with a capacitor to speed up the response speed. These factors have led to the problem that the gate drive circuit for driving GaN-FETs has a complex configuration.

[0010] The present invention has been made to solve the above-mentioned conventional problems, and aims to provide a switching module that can achieve high-speed switching using GaN-FETs even with a simple and inexpensive configuration. [Means for solving the problem]

[0011] In order to solve the above problems, one representative aspect of the present invention is a switching module including a GaN-FET mounted on a substrate, a driver circuit connected to the gate electrode of the GaN-FET via a gate resistor, and a driver power supply that provides a drive voltage to the driver circuit, wherein the driver circuit has a configuration in which multiple logic IC circuits are connected in parallel.

[0012] According to the present invention having such a configuration, by configuring a driver circuit that inputs a gate current to the gate electrode of a GaN-FET by connecting multiple logic IC circuits in parallel, high-speed switching by the GaN-FET can be achieved even with a simple and inexpensive configuration. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a block diagram of a high-frequency power supply device in which a switching module according to a first embodiment is applied to an amplifier. [Figure 2] 2 is a circuit diagram showing an equivalent connection circuit in the vicinity of the switching module shown in FIG. 1. FIG. [Figure 3] 2 is a block diagram showing an outline of a driver power supply and a driver circuit shown in FIG. 1. FIG. [Figure 4] FIG. 10 is a block diagram showing an outline of a driver power supply and a driver circuit of a switching module according to a second embodiment. [Figure 5] FIG. 11 is a block diagram showing an outline of a driver power supply and a driver circuit of a switching module according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] A typical example of a switching module according to the present invention will be described below with reference to FIGS.

[0015] Example 1 Fig. 1 is a block diagram of a high frequency power supply device in which a switching module according to a first embodiment, which is a representative example of the present invention, is applied to an amplifier. Fig. 2 is a circuit diagram showing an equivalent connection circuit in the vicinity of the switching module shown in Fig. 1. Fig. 3 is a block diagram showing an outline of the driver power supply and driver circuit shown in Fig. 1. Such a high frequency power supply device is applicable, for example, to a high frequency power supply device for semiconductor manufacturing equipment in which the amplifier output is 1 kW or more and the output frequency is 0.3 MHz or more.

[0016] As shown in FIG. 1, a high-frequency power supply device 1 to which the switching module according to the first embodiment is applied includes, as an example, a DC power supply 10 that supplies a DC voltage to be switched, a switching module 100H connected to an input terminal on one side (high side) of the DC power supply 10, a switching module 100L connected to an input terminal on 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.

[0017] 1 illustrates a high-frequency power supply device configured as a so-called half-bridge circuit including a pair of switching modules, but a high-frequency power supply device configured as a full-bridge circuit including two pairs of switching modules may also be used. Note that, because 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 a description of the low-side switching module will be omitted.

[0018] A switching module 100H according to the first embodiment includes a GaN-FET 120H mounted on a substrate 110H, a driver circuit 130H connected to a gate electrode G of the GaN-FET 120H via a connection wiring 140H, and a driver power supply 150H that applies a drive voltage to the driver circuit 130H. As shown in Fig. 1, a control unit 20 is electrically connected to the high-side driver circuit 130H and the low-side driver circuit 130L via signal lines 22H and 22L, and outputs drive signals DsH and DsL to the driver circuits 130H and 130L, respectively.

[0019] The substrate 110H is formed of a material with good thermal conductivity, such as beryllium oxide (BeO) or aluminum nitride (AlN), for example, which allows the heat generated when the module is operated to be effectively dissipated or exhausted.

[0020] The GaN-FET120H is a type of field-effect transistor (FET) device in which the current path is formed from GaN, and is configured as a power semiconductor with a "lateral" structure in which the gate electrode G, source electrode S, and drain electrode D are all located on the same plane. This structure enables the GaN-FET120H to perform switching operations at higher speeds than general MOSFETs.

[0021] As an example, the driver circuit 130H has a configuration in which logic IC circuits each consisting of a plurality of TTL elements 132H1, 132H2, and 132H3 are connected in parallel, as shown in Fig. 3. Note that Fig. 3 illustrates an example in which three TTL elements 132H1 to 132H3 are included, but in the present invention, any number of logic IC circuits can be used as long as a plurality of elements are connected in parallel.

[0022] As an example, the connection wiring 140H includes a bonding wire BW made of, for example, gold, copper, or aluminum, and a gate resistor Rg. As shown in Figure 3, this connection wiring 140H is simulated as an electrical equivalent circuit including the gate resistor Rg, stray inductance Ls, and resistance component Rs. In this case, the attenuation rate of the gate-source voltage Vgs applied from the gate electrode G can be controlled by selecting the resistance value of the gate resistor Rg based on the parasitic capacitance of the GaN-FET 120H.

[0023] The driver power supply 150H includes, for example, an inverter 152H that converts input from a direct current power supply DC into alternating current, a transformer 154H that transforms the alternating current from the inverter 152H, and a converter 156H that reconverts the alternating current input from the transformer 154H into direct current. The output current from the converter 156H is input in parallel to each of the TTL elements 132H1 to 132H3 of the driver circuit 130H.

[0024] In the switching module 100H according to the present invention, by using a GaN-FET 120H as a switching element, the gate current IgH input to the gate electrode G from the driver circuit 130H can be made smaller than that of, for example, a general MOSFET. As an example, in a conventional MOSFET using a silicon substrate, the input capacitance Ciss is large (approximately 600 to 3000 pF) and the gate voltage Vgs required to use the element in the saturation region of a high frequency band (for example, 13.56 MHz) is also high (for example, 12 V or more), so the power supplied by the driver power supply to drive the driver circuit must also be large (for example, 10 W or more).

[0025] In contrast, the GaN-FET 120H used in Example 1 has a smaller capacitance (approximately 150 to 300 pF) than a typical MOSFET, and the gate voltage Vgs required for use in the saturation region is 5 V or less, allowing the supply voltage of the driver power supply 150H to be approximately 1 to 2 W. Furthermore, because GaN-FETs are capable of being driven at higher speeds than conventional MOSFETs using silicon substrates, the displacement voltage slope (dV / dt) of the drain-source voltage Vds becomes larger (e.g., 100 V / ns). This can cause switching malfunctions on the high-side during high-speed driving, so it is desirable to keep the coupling capacitance of the driver power supply that supplies the gate voltage as small as possible (e.g., 5 pF or less).

[0026] Therefore, in the first embodiment, the transformer 154H of the driver power supply 150H is formed as a coreless transformer having a pair of air-core coils 155H1 and 155H2, as shown in Fig. 3. This reduces the size of the transformer 154H, thereby reducing the power supply and the coupling capacitance of the power supply. As a result, it becomes possible to reduce the area (surface area) occupied by the entire transformer power supply.

[0027] Next, the switching operation of the GaN-FET in the switching module 100H according to the first embodiment shown in FIGS. 1 to 3 will be described.

[0028] 1, for example, by switching on either switching module 100H or 100L, the input from DC power supply 10 is output as high frequency voltage VF. At this time, control unit 20 transmits drive signal DsH or DsL for turning on switching modules 100H, 100L to either one of the modules via signal lines 22H, 22L.

[0029] 2, the driver circuit 130H outputs a gate current IgH via the connection wiring 140H while receiving the drive signal DsH. The GaN-FET 120H receives this gate current IgH at its gate electrode G, turns on, and outputs the power input from the input terminal Vin to the output terminal Vout. By repeating this operation, the switching operations of the high-side and low-side switching modules 100H and 100L are performed.

[0030] 3, in the driver circuit 130H according to the first embodiment, TTL elements 132H1 to 132H3 connected to a voltage from a driver power supply 150H are arranged in parallel to form a logic IC circuit. At this time, a drive signal DsH from the control unit 20 is input to the parallel-connected TTL elements 132H1 to 132H3, and gate currents Ig1 to Ig3 are output from the respective elements. These gate currents Ig1 to Ig3 join together at the subsequent stage to form a gate current IgH.

[0031] As a result, even if the output levels of the gate currents Ig1 to Ig3 from the individual TTL elements 132H1 to 132H3 are small, the gate current IgH output from the driver circuit 130H as a composite current of the multiple gate currents can be set to a desired level. Note that any type of logic circuit, such as an AND circuit, OR circuit, or buffer circuit, can be used as the logic circuit constituting the logic IC circuit.

[0032] The specific configuration of the switching module 100H according to the first embodiment can be exemplified as follows.

[0033] For example, when the switching frequency is set to 13.56 MHz, the gate drive power required for the switching operation of the GaN-FET 120H exemplified in Example 1 is approximately 0.1 W. To obtain such gate drive power, it is sufficient to connect two or three of the TTL elements 132H1 to 132H3 shown in FIG. 3 in parallel.

[0034] On the other hand, as described above, the gate drive power of the GaN-FET 120H is required to be at most a few watts, and therefore the insulating transformer used in the driver power supply 150H that supplies drive power to the driver circuit 130H can also be reduced in size to about a coil diameter of 20 mm and a coil spacing of 1 mm by using, for example, air-core coils 155H1 and 155H2 made of a material with a dielectric constant ε = 1. This allows the electrostatic capacitance CtH between the windings of the air-core coils 155H1 and 155H2 to be reduced to 5 pF or less.

[0035] It is possible to further reduce the coil diameter by using a material for the air core coils 155H1 and 155H2 with a dielectric constant ε higher than 1. Also, while Fig. 3 shows an example of circular air core coils 155H1 and 155H2, the coil shape may be polygonal, and the turns ratio can also be selected as desired.

[0036] By having the above-mentioned configuration, the switching modules 100H, 100L according to Example 1 can achieve high-speed switching using GaN-FETs even with a simple and inexpensive configuration by configuring the driver circuits 130H, 130L, which input gate currents IgH, IgL to the gate electrodes G of the GaN-FETs 120H, 120L, to be configured with logic IC circuits consisting of multiple TTL elements 132H1 to 132H3 connected in parallel.

[0037] <Example 2> 4 is a block diagram showing an outline of a driver power supply and a driver circuit of a switching module according to Example 2. Here, in the switching module according to Example 2, components having the same or similar configurations as those in Example 1 are assigned the same reference numerals as those in Example 1, and repeated description will be omitted.

[0038] In the switching module 100H according to the second embodiment, the driver circuit 230H has a configuration in which logic IC circuits each made up of a plurality of CMOS elements 232H1, 232H2, and 232H3 are connected in parallel, as shown in Fig. 4. As in the first embodiment, Fig. 4 illustrates an example in which three CMOS elements 232H1 to 232H3 are provided, but any number of logic IC circuits may be used as long as multiple elements are connected in parallel.

[0039] In the driver circuit 230H according to the second embodiment, CMOS elements 232H1 to 232H3 connected to a voltage from a driver power supply 150H are arranged in parallel to form a logic IC circuit. At this time, a drive signal DsH from the control unit 20 is input to the parallel-connected CMOS elements 232H1 to 232H3, and gate currents Ig1 to Ig3 are output from each element. These gate currents Ig1 to Ig3 join together at the subsequent stage to form the gate current IgH.

[0040] 3, even if the output levels of the gate currents Ig1-Ig3 from the individual CMOS elements 232H1-232H3 are small, the gate current IgH output from the driver circuit 230H as a composite current of the multiple gate currents can be set to a desired level. In this case, because a typical CMOS element consumes less power than a TTL element to obtain the same level of output, use of the driver circuit 230H according to this modified example makes it possible to further reduce the capacity of the driver power supply 150H.

[0041] By having the above-described configuration, the switching modules 100H and 100L according to Example 2 not only have the effects obtained with the switching module of Example 1, but also have the advantage that by configuring the logic IC circuit using CMOS elements, the structure of the driver power supply can be further simplified, thereby making it possible to reduce the overall size of the switching module.

[0042] Example 3 5 is a block diagram showing an outline of a driver power supply and a driver circuit of a switching module according to Example 3. Here, as in Example 2, in the switching module according to Example 3, components having the same or similar configurations as those in Example 1 are assigned the same reference numerals as those in Example 1, and repeated description will be omitted.

[0043] As explained in Example 1, since GaN-FETs can experience switching malfunctions on the high side when driven at high speed, it is desirable that the coupling capacitance of the driver power supply that supplies the gate voltage be as small as possible (for example, 5 pF or less). Therefore, in Example 3, an optical power supply device that combines a light-emitting element and a photoelectric converter is used as the driver power supply.

[0044] 5, in a switching module 100H according to the third embodiment, a driver power supply 350H includes, for example, a light-emitting element 352H that emits light in response to input from a direct-current power supply DC, a 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 electric power. The electric power output from the photoelectric converter 356H is input to each of a plurality of TTL elements 132H1 to 132H3 connected in parallel as a logic IC circuit of the driver circuit 130H.

[0045] The light emitting element 352H is, for example, a semiconductor laser (LD) or a light emitting diode (LED) that emits light when energized. This allows the driver power supply 350H to be further miniaturized and the power required for the direct current power supply DC to be reduced. Note that, depending on the configuration of the photoelectric converter 356H (described later), a light emitting means such as a lamp may be used as the light emitting element 352H.

[0046] For example, when the transmitted light is highly directional, such as the laser light described above, the transmission mechanism 354H can be an optical system, such as a mirror arranged on the optical path, or a transmission path, such as an optical fiber. In particular, when the transmission mechanism 354H is configured with an optical fiber, adjusting the fiber length can construct an isolated power supply in which the capacitance CtH between the light-emitting element 352H and the photoelectric converter 356H is suppressed to 1 pF or less. Furthermore, by adopting a method of transmitting light using an optical fiber, the light-emitting element 352H can be configured separately from the switching module 100H, further simplifying the configuration of the entire module.

[0047] The photoelectric converter 356H is configured as, for example, a semiconductor element such as a photodiode or a phototransistor, or a photocell or the like that can convert input light energy into electric power. In this case, by arranging the light emitting element 352H and the photoelectric converter 356H closely, the transmission mechanism 354H may be omitted and electric power may be transmitted via the space between them.

[0048] By having the above-described configuration, the switching modules 100H, 100L according to Example 3 have the effects obtained by the switching module of Example 2, and in addition, by configuring the driver power supplies 150H, 150L as optical power supply devices, the drive power of the driver power supplies themselves can be reduced, which results in a further reduction in the size of the entire switching module. Also, by adjusting the distance between the light-emitting element 352H and the photoelectric converter 356H, the power supply capacity (electrostatic capacitance) between them can be minimized, which makes it possible to suppress malfunction of the GaN-FET 120H.

[0049] The above-described embodiments are merely examples of the switching module according to the present invention, and the present invention is not limited to the embodiments of the embodiments. Furthermore, 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. [Explanation of symbols]

[0050] 1 High frequency power supply 10 DC power supply 20 Control Unit 22H, 22L signal line 100H, 100L Switching Module 110H, 110L board 120H, 120H GaN-FET 130H, 130L, 230H driver circuit 132H1, 132H2, 132H3 TTL elements 140H, 140L connection wiring 150H, 150L, ​​350H driver power supply 232H1, 232H2, 232H3 CMOS elements 352H Light-emitting element 354H Transmission mechanism 356H Photoelectric Converter G gate electrode D drain electrode S source electrode Rg Gate resistance IgH, IgL gate current Vgs Gate-source voltage DsH, DsL drive signal

Claims

1. A switching module including a GaN-FET mounted on a substrate, a driver circuit connected to a gate electrode of the GaN-FET via a gate resistor, and a driver power supply that applies a drive voltage to the driver circuit, the driver circuit has a configuration in which a plurality of logic IC circuits are connected in parallel, the driver power supply includes a coreless transformer having an air-core coil; The air-core coil is made of a material with a dielectric constant higher than 1, and the capacitance between the windings is 5 pF or less. A switching module characterized by:

2. 2. The switching module according to claim 1, wherein the logic IC circuit is made up of a TTL element or a CMOS element.

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