Bias generation for common drain bi-directional switch driver

Abstract

The invention relates to common drain bidirectional switch driven bias voltage generation. The circuit includes a first driver (320), a second driver (330), and a bias generator (340). The first driver (320) has a first bias terminal (324), a first reference terminal (322), a first driver input (326), and a first driver output (328). The second driver (330) has a second bias terminal (334), a second reference terminal (332), a second driver input (336), and a second driver output (338). The bias generator (340) has a first input (342), a second input (344), a first bias output (346), and a second bias output (348), the first input (342) being coupled to the first reference terminal (322), the second input (344) being coupled to the second reference terminal (332), the first bias output (346) being coupled to the first bias terminal (324), and the second bias output (348) being coupled to the second reference terminal (332). The first bias output (346) is coupled to the first bias terminal (334), and the second bias output (348) is coupled to the second bias terminal (334), wherein the bias generator (340) may be configured to generate a first bias voltage at the first bias output (346) and a second bias voltage at the second bias output (348) based on a supply voltage.

Description

[0001] Cross-reference of related applications

[0002] This application claims the benefit and priority of U.S. Provisional Application No. 63 / 682,968, filed on August 14, 2024, entitled “Bias Generation for Common Drain Bidirectional Switch Driver,” which has been assigned to the assignee of this application and is hereby incorporated herein by reference in its entirety for all purposes. Technical Field

[0003] This application relates to bias generation in a common-drain bidirectional switch driver. Background Technology

[0004] A bidirectional switch can support bidirectional current flow between two switch terminals when it is in an enabled ("ON") state and can provide bidirectional voltage blocking between the two switch terminals when it is in a disabled ("OFF") state. The bidirectional switch may include one or more transistors series coupled between the two switch terminals, and the voltage at the control terminal (e.g., gate) of the one or more transistors can set the enabled / disabled state of the bidirectional switch. Summary of the Invention

[0005] The present invention is provided to illustrate the disclosed concepts in a simplified form, and these examples will be further described in the detailed description below (including the provided drawings).

[0006] According to some aspects, the circuit may include a first driver, a second driver, and a bias generator. The first driver has a first bias terminal, a first reference terminal, a first driver input, and a first driver output, and the first driver output may be configured to couple to a first gate of a first transistor. The second driver has a second bias terminal, a second reference terminal, a second driver input, and a second driver output. The bias generator has a first input, a second input, a first bias output, and a second bias output, the first input coupled to the first reference terminal, the second input coupled to the second reference terminal, the first bias output coupled to the first bias terminal, and the second bias output coupled to the second bias terminal, wherein the bias generator may be configured to generate a first bias voltage at the first bias output and a second bias voltage at the second bias output based on a power supply voltage.

[0007] According to some aspects, the circuit may include a pair of transistors, a first driver, a second driver, and a bias generator. The pair of transistors has a common drain, a first source, a second source, a first gate, and a second gate. The first driver has a first bias terminal, a first reference terminal, a first driver input, and a first driver output; the first reference terminal is coupled to the first source, and the first driver output is coupled to the first gate. The second driver has a second bias terminal, a second reference terminal, a second driver input, and a second driver output; the second reference terminal is coupled to the second source, and the second driver output is coupled to the second gate. The bias generator has a first input, a second input, a first bias output, and a second bias output; the first input is coupled to the first source, the second input is coupled to the second source, the first bias output is coupled to the first bias terminal, and the second bias output is coupled to the second bias terminal. The bias generator may be configured to generate a first bias voltage at the first bias output and a second bias voltage at the second bias output based on a power supply voltage.

[0008] Depending on certain aspects, the circuit may include a first input port, a first output port, and a second output port. The circuit may also include a first bidirectional switch and a second bidirectional switch. The first bidirectional switch is coupled between the first input port and the first output port, and includes a first switch driver, a second switch driver, and a first bias generator. The first bias generator is configured to generate a first bias voltage for the first switch driver and a second bias voltage for the second switch driver based on a first power supply voltage. The second bidirectional switch is coupled between the first input port and the second output port, and includes a third switch driver, a fourth switch driver, and a second bias generator. The second bias generator is configured to generate a third bias voltage for the third switch driver and a fourth bias voltage for the fourth switch driver based on a second power supply voltage.

[0009] The foregoing summary provides a fairly broad overview of various features of the embodiments of this disclosure in order to better understand the following detailed description. Additional features and advantages of such embodiments will be described below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used alone to define the scope of the claimed subject matter. The subject matter should be understood by referring to appropriate portions of the entire specification, any or all drawings, and each claim. The foregoing, together with other features and embodiments, will be described in more detail in the following description, claims, and accompanying drawings. Attached Figure Description

[0010] The following description of illustrative examples is based on the diagrams provided below.

[0011] Figure 1AThis is a schematic diagram of an example of a bidirectional switch containing two transistors with a common drain region.

[0012] Figure 1B This is a cross-sectional view of an example of a monolithic bidirectional switch.

[0013] Figure 2 This is a schematic diagram of an example of a circuit including a bidirectional switch and a circuit for controlling the bidirectional switch.

[0014] Figure 3 It is a block diagram of an example of a circuit including a bidirectional switch and a circuit for controlling the bidirectional switch.

[0015] Figure 4 It is a block diagram of an example of a circuit including a bidirectional switch and a circuit for controlling the bidirectional switch.

[0016] Figure 5 This is a schematic diagram of an example of a circuit including a bidirectional switch and a circuit for controlling the bidirectional switch.

[0017] Figure 6 This is a schematic diagram of another example of a circuit that includes a bidirectional switch and a circuit for controlling the bidirectional switch.

[0018] Figure 7 It is a block diagram of an example of a circuit including a bidirectional switch and a circuit for controlling the bidirectional switch.

[0019] Figure 8A This is a schematic diagram of an example of a circuit including a bidirectional switch and a circuit for controlling the bidirectional switch.

[0020] Figure 8B Explanation Figure 8A Examples of circuit operation.

[0021] Figure 9 It is a block diagram of an example of a circuit including a bidirectional switch and a circuit for controlling the bidirectional switch.

[0022] Figure 10 This is a schematic diagram of an example of a circuit including a bidirectional switch and a circuit for controlling the bidirectional switch.

[0023] Figure 11 This is a schematic diagram of an example of a circuit including a bidirectional switch and a circuit for controlling the bidirectional switch.

[0024] Figure 12 This is a schematic diagram of an example of a circuit including a bidirectional switch and a circuit for controlling the bidirectional switch.

[0025] Figure 13 This is a schematic diagram of an example of a circuit including a bidirectional switch and a circuit for controlling the bidirectional switch.

[0026] Figure 14A This is a schematic diagram of an example of a matrix converter with a shared bias power supply.

[0027] Figure 14B This is a schematic diagram of an example of a matrix converter with an additional shared bias power supply.

[0028] Figure 15 This is a schematic diagram of an example of a bidirectional switch.

[0029] The drawings and accompanying detailed description are provided to understand the features of various examples and do not limit the scope of the appended claims. Examples illustrated in the drawings and described in the accompanying detailed description can be readily used as the basis for modifications or designs of other examples within the scope of the appended claims. Those skilled in the art will readily recognize from the following description that alternative embodiments of the illustrated structures and methods may be employed without departing from the principles of this disclosure or the benefits proclaimed. Where possible, the same reference numerals may be used to refer to the same elements shared between the drawings. The drawings are drawn to clearly illustrate relevant elements or features and are not necessarily drawn to scale. Detailed Implementation

[0030] This disclosure generally relates to bidirectional switches. In some instances, the circuit may include a transistor-based bidirectional switch and two drivers for controlling the transistor-based bidirectional switch. The transistor-based bidirectional switch may include, for example, two gallium nitride (GaN)-based high electron mobility transistors (HEMTs) sharing a common drain region. The two drivers may be biased (e.g., powered) by a bias circuit that can generate respective bias voltages (e.g., supply voltages) for the two drivers using a single voltage supply / source (instead of using two separate voltage supplies).

[0031] GaN-based HEMTs may comprise a heterojunction formed of a channel layer (e.g., a GaN layer) and a barrier layer (e.g., an aluminum gallium nitride (AlGaN) layer). A high-density two-dimensional electron gas (2DEG) may be formed at the heterojunction to serve as a conductive channel. For example, the 2DEG may have a density greater than about 10. 13 cm -2The surface charge density of GaN-based HEMTs is high, resulting in low static on-state resistance. Due to their high breakdown field, high electron mobility, low static resistance, and high thermal conductivity, GaN-based HEMTs are attractive for high-frequency and high-power applications. For example, since current can flow from the drain to the source and vice versa in an HEMT during turn-on, and current can be blocked from flowing from the drain to the source in an HEMT during turn-off, GaN-based HEMTs can be used for bidirectional power switching. Due to the side-device structure and absence of a body diode in GaN-based HEMTs, monolithic bidirectional switches implemented using GaN-based HEMTs can be fabricated relatively easily. Furthermore, the low static on-state resistance of GaN-based HEMTs allows for lower power losses and lower voltage drops in GaN-based bidirectional switches.

[0032] In some instances, a GaN-based bidirectional switch may comprise two back-to-back HEMTs (e.g., where the drains of the two HEMTs are connected together) to form a dual-gate bidirectional switch sharing a common drain region. The source of the first HEMT forms the first terminal of the bidirectional switch, and the source of the second HEMT forms the second terminal of the bidirectional switch. Since the rated voltage of the HEMTs can depend on the gate-drain separation, using a common drain region provides the necessary gate-drain separation for a specific rated voltage in both directions, while reducing the overall distance between the two terminals of the bidirectional switch, and thus reducing the on-state resistance and power loss of the bidirectional switch. For example, the first HEMT of the bidirectional switch may initially be in the off state, with its gate and source having the same high voltage. The second HEMT may be a blocking transistor, and its gate may be a gate used to switch the bidirectional switch on or off, such that the common drain region between the gates of the two HEMTs can be used to block high voltage from reaching the second terminal of the bidirectional switch. Similarly, the second HEMT of the bidirectional switch can initially be in the off state, with its gate and source having the same high voltage. The gate of the first HEMT can be the gate used to switch the bidirectional switch on or off, so that the common drain region between the gates of the two HEMTs can be used to block high voltage from reaching the first terminal. Therefore, the distance between the gate and the corresponding source of each HEMT can be short, while the bidirectional switch can still achieve high voltage blocking in both directions due to the shared drain region. Thus, a monolithic bidirectional switch with a common drain region and dual gates can have reduced cell spacing (and therefore smaller device size) and lower on-state resistance (Ron), while achieving high voltage blocking.

[0033] Because the sources of the two transistors in a bidirectional switch are coupled to two switch terminals, and these terminals are at different voltage levels before the bidirectional switch is turned on (enabled), different voltage levels can be applied to the gates of the two transistors to turn on the bidirectional switch. Therefore, the gate of each transistor in the bidirectional switch can be controlled by a corresponding driver. Each driver may have a driver input, a reference terminal (e.g., coupled to the source of the transistor in the bidirectional switch), a bias terminal (e.g., a power supply terminal), and a driver output coupled to a control terminal (e.g., the gate) of the transistor-based bidirectional switch. A bias circuit can be used to set an appropriate bias voltage level at the bias terminals of the drivers so that the outputs of the drivers can properly turn on or off the corresponding transistors of the bidirectional switch. Because the reference terminals of the two drivers are coupled to the two terminals of the bidirectional switch, and these terminals are at different voltage levels before the bidirectional switch is turned on, the bias terminals of the two drivers can be at different voltage levels so that the outputs of the two drivers can properly turn on or off the two transistors of the bidirectional switch. In some bidirectional switch control circuits, two isolated voltage sources can be used to apply different voltage levels to the bias terminals of the two drivers. Such bidirectional switch control circuits may be less efficient, more expensive, and larger in size.

[0034] In some examples disclosed herein, the drivers of the two control terminals of a bidirectional switch can receive corresponding bias voltages from a bias generator that generates the corresponding bias voltages using a single voltage power supply / source. The bias generator may have a first input, a second input, a first bias output, and a second bias output. The first input may be coupled to a first switching terminal (e.g., the source of a first transistor) of a bidirectional switch (which may be coupled to a reference terminal of a first driver). The second input may be coupled to a second switching terminal (e.g., the source of a second transistor) of a bidirectional switch (which may be coupled to a reference terminal of a second driver). The first bias output may be coupled to a bias terminal of the first driver, and the second bias output may be coupled to a bias terminal of the second driver.

[0035] In some instances, the bias generator may include a maximum voltage selector coupled to first and second inputs and having an output. The bias generator may also include an isolated voltage source having a first (e.g., negative) power supply terminal coupled to the output of the maximum voltage selector, a first bootstrap circuit coupled between a second (e.g., positive) power supply terminal of the isolated voltage source and a first bias output, and a second bootstrap circuit coupled between a second power supply terminal of the isolated voltage source and a second bias output. In one instance, the maximum voltage selector may include a third transistor and a fourth transistor, which may have a common drain terminal coupled to the output of the maximum voltage selector.

[0036] In some instances, the bias generator may include a minimum voltage selector coupled to first and second inputs and having an output. The bias generator may also include an isolated voltage source having a first (e.g., negative) power supply terminal coupled to the output of the minimum voltage selector, a first bootstrap circuit coupled between a second (e.g., positive) power supply terminal of the isolated voltage source and the first bias output, and a second bootstrap circuit coupled between the second power supply terminal of the isolated voltage source and the second bias output. In one instance, the minimum voltage selector may include: a first switch located between the first input and output of the minimum voltage selector; and a second switch located between the second input and output of the minimum voltage selector.

[0037] In some instances, the bias generator may include a charge transfer circuit coupled between a first bias output and a second bias output. In some instances, the charge transfer circuit may include an auxiliary bidirectional switch. The auxiliary bidirectional switch may be controlled by two auxiliary drivers that receive the same bias voltage and the same reference voltage as the first or second driver. In one instance, the bias generator may further include: a first voltage source (e.g., a first bootstrap capacitor or an isolation voltage supply) coupled between a first input and a first bias output; a first startup circuit coupled between the second bias output and the first input and including a first output terminal coupled to the first bias output; a second voltage source (e.g., a second bootstrap capacitor or an isolation voltage supply) coupled between the second input and the second bias output; and a second startup circuit coupled between the first bias output and the second input and including a second output terminal coupled to the second bias output. In another example, the bias generator may further include: a voltage power supply having a positive terminal and a negative terminal coupled to a first input; a first bootstrap capacitor coupled between the first input and a first bias output; a first voltage regulator (e.g., a source follower) coupled between the positive terminal of the voltage power supply and the first bias output; a second bootstrap capacitor coupled between a second input and a second bias output; a second auxiliary bidirectional switch having a first terminal coupled to the positive terminal of the voltage power supply; and a second voltage regulator (e.g., a source follower) coupled between a second terminal of the second auxiliary bidirectional switch and a second bias output.

[0038] In another example, the bias generator may include a first bootstrap capacitor or a first voltage source coupled between a first input terminal and a first bias output terminal, and a second bootstrap capacitor or a second voltage source coupled between a second input terminal and a second bias output terminal. The charge transfer circuit may include a first bidirectional switch and a first voltage regulator (e.g., a source follower) coupled between the first and second bias output terminals, and a second bidirectional switch and a second voltage regulator (e.g., a source follower) coupled between the first and second bias output terminals. The first bidirectional switch may be coupled to the first bias output terminal, and the first voltage regulator may be coupled to the second bias output terminal. The second bidirectional switch may be coupled to the second bias output terminal, and the second voltage regulator may be coupled to the first bias output terminal. The first bidirectional switch may include an enhancement-mode transistor and a depletion-mode transistor, wherein the enhancement-mode transistor may include a first gate terminal coupled to the output terminal of the first driver terminal via a charge pump capacitor, and the depletion-mode transistor may include a second gate terminal coupled to the second input terminal of the bias generator (and the second terminal of the bidirectional switch).

[0039] In another example, the bias generator may include a voltage source coupled between a first input terminal and a first bias output terminal, and a bootstrap capacitor coupled between a second input terminal and a second bias output terminal. The charge transfer circuit may include an auxiliary bidirectional switch and a voltage regulator (e.g., a source follower) coupled between the first and second bias output terminals, wherein the auxiliary bidirectional switch is coupled to the first bias output terminal and the voltage regulator is coupled to the second bias output terminal. The charge transfer circuit may also include an auxiliary driver having a third bias terminal, a third reference terminal, and a third driver output terminal, wherein the third bias terminal is coupled to the first bias output terminal and the third reference terminal is coupled to the first input terminal. The auxiliary bidirectional switch may include an enhancement-mode transistor and a depletion-mode transistor, wherein the enhancement-mode transistor may have a first gate terminal coupled to the third driver output terminal via a charge pump capacitor, and the depletion-mode transistor may have a second gate terminal coupled to the second input terminal.

[0040] The bias generator disclosed herein can generate different bias voltages using a single voltage supply. It can charge the voltage source (e.g., a bootstrap capacitor) to bias the switch driver before startup when the voltage level of the voltage source is low, and can also replenish the voltage source after the bidirectional switch is turned on. In some instances, the bias generator may also include other control circuitry, such as control circuitry to control charge transfer circuitry and / or voltage regulators to reduce leakage or prevent current (and charge transfer) from flowing along paths with large voltage drops, thereby reducing the power loss of the bias generator.

[0041] Because the bias generation circuit disclosed herein can generate different bias voltages using a single voltage supply, the total number of voltage supply sources used in a power switch matrix (e.g., a matrix converter) can be significantly reduced. Furthermore, the bias generation circuit disclosed herein reduces power losses due to leakage and avoids power losses due to charge transfer along paths with large voltage drops. Therefore, systems using the common-drain bidirectional switch and bias generation circuit disclosed herein are cheaper and more efficient.

[0042] Various features are described below with reference to the figures. The illustrated examples may not possess all the aspects or advantages shown. The aspects or advantages described in connection with a particular example are not necessarily limited to that example and can be practiced in any other example, even if not so stated or explicitly described. Furthermore, the methods described herein may be described with a specific order of operations, but other methods according to other examples may be implemented with various other orders of operations (e.g., different serial or parallel executions involving various operations).

[0043] Various examples are described herein. While specific examples may illustrate various aspects of the features generally described above, examples may be incorporated into any combination of features generally described above (which are described in more detail in the examples below). For ease of reference, the three-dimensional xyz axes are illustrated in some figures. Some cross-sectional views of various semiconductor devices in this document serve as general depictions for illustrating various aspects or concepts of such semiconductor devices. More specifically, some drain contact structures illustrated in the cross-sectional views may not necessarily accurately depict the structure of such drain contact points beyond the extent described herein. The illustration of these drain contact structures is intended to illustrate various aspects or concepts of those drain contact structures.

[0044] Examples are described below in the context of HEMTs. Some examples may be implemented in enhancement-mode side-facing HEMTs for high-voltage (e.g., about 650V to about 1,200V) or low-to-medium-voltage (e.g., about 10V to about 100V, or about 10V to about 200V) applications. In other examples, the semiconductor device may comprise a bidirectional field-effect transistor (FET), a gated Schottky barrier diode (e.g., a gate-to-drain shorted structure or a gate-to-source shorted structure), or similar devices. Some examples may be implemented with any epitaxial structure, any field plate and / or ohmic contact structure, planar or three-dimensional structure (e.g., fin structure), and / or various other modifications. For illustrative purposes, some examples disclosed herein may focus on group III nitride-based devices, such as GaN-based HEMTs. However, this disclosure is not limited to GaN-based HEMTs or other HEMTs and may be applied to other devices formed from other semiconductor materials, such as silicon, other group III nitrides, or other III-V semiconductor materials.

[0045] In the following description, specific details are set forth for purposes of explanation in order to provide a thorough understanding of examples of this disclosure. However, it will be apparent, however, that various embodiments may be practiced without these specific details. For example, apparatuses, systems, structures, assemblies, integrated circuits, and other components may be shown as components in block diagram form to avoid obscuring examples with unnecessary details. In other cases, well-known apparatuses, processes, systems, structures, and techniques may be shown without the need for necessary details to avoid obscuring examples. The drawings and descriptions are not intended to be limiting. The terminology and expressions used in this disclosure are used as descriptive rather than limiting terms, and their use is not intended to exclude any equivalents of the features or portions thereof shown and described. The word “example” is used herein to mean “serving as an example, illustration, or description.” Any embodiment or design described herein as an “example” is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

[0046] A bidirectional switch can support bidirectional current flow when it is turned on and provide bidirectional voltage blocking when it is turned off. A bidirectional switch can be used, for example, as a bidirectional power switch for charger multiplexing, where the switch can be turned on to charge a battery using current from a power source to the battery, or to supply current from the battery to a load. The bidirectional switch can also be turned off to block current in either direction, for example, preventing the draw of a charged battery or preventing one battery from charging another. A bidirectional switch can be implemented using two back-to-back transistors (e.g., where the drains are connected together or where the sources are connected together) to form a bidirectional switch with a common drain or a common source. The two transistors can include, for example, metal-oxide-semiconductor field-effect transistors (MOSFETs) or HEMTs.

[0047] GaN-based HEMTs incorporate heterostructures that can induce a two-dimensional electron gas (2DEG) at the interface between two GaN-based materials with different band gaps. In one example, the heterostructure may consist of a GaN layer and an Al layer. x Ga (1-x) An N-layer is formed, where x is the aluminum concentration. The band gap of the GaN layer can be compared to that of Al. x Ga (1-x)The N-layer is narrow and, due to its wide bandgap, can be referred to as a barrier layer. Due to the bandgap mismatch, large conduction band shift, and spontaneous and piezoelectric polarization properties of the group III nitride layer, a high-mobility 2DEG can be generated in the GaN layer near the heterostructure interface, forming a conductive channel (hence the name "channel layer"). Compared to silicon-based transistors, GaN-based transistors typically exhibit high breakdown electric field, high electron mobility, low on-state resistance, high current, faster switching speed, high thermal conductivity, and excellent reverse recovery performance, making them more suitable for applications where low loss and high efficiency are expected, such as power electronic devices (e.g., power switches).

[0048] GaN-based transistors may include a gate structure located between a source structure and a drain structure. The drain structure may include metal contacts that are directly or indirectly (e.g., via tunneling) coupled to the channel layer and may form an ohmic contact with the channel layer. The source structure may include metal contacts that are directly or indirectly coupled to the channel layer and may form an ohmic contact with the channel layer. Depending on the gate structure, GaN-based transistors may be enhancement-mode (E-type) high electron mobility transistors (e-HEMTs) or depletion-mode (D-type) high electron mobility transistors (d-HEMTs). For example, the gate structure of an e-HEMT may include a p-GaN layer formed above a barrier layer and gate contacts (metal electrodes) formed on the p-GaN layer, which together form the p-GaN gate structure. The p-GaN layer of the gate structure may be doped with, for example, magnesium (Mg), which is a acceptor that allows the GaN layer to be p-type or p-doped. The p-GaN layer can deplete electrons in the 2DEG channel beneath the p-GaN gate structure, disabling the conductive path between the source and gate, and thus turning off the e-HEMT when no gate drive voltage is applied to the gate contacts. When a positive voltage above a threshold voltage is applied to the gate contacts, the gate structure attracts electrons to fill the 2DEG beneath the gate structure, thereby turning on the e-HEMT. Conversely, the gate structure of the d-HEMT may include an insulating layer (e.g., a dielectric layer) above a barrier layer and gate contacts (e.g., metal electrodes) on the insulating layer. When no voltage signal is applied to the gate contacts, the 2DEG beneath the gate structure is not depleted, enabling the conductive path in the channel layer between the drain and source structures even without a positive gate voltage. The d-HEMT can be turned off by applying a negative threshold voltage to the gate contacts to deplete electrons from the 2DEG beneath the gate structure. In some applications, such as switch-mode power supply applications (e.g., power switches), e-HEMT can be used instead of d-HEMT, for example, to reduce leakage current, reduce power loss, simplify drive circuitry, and / or improve device stability.

[0049] High-density two-dimensional electron gases (2DEGs) can be formed at the heterojunction of GaN-based HEMTs to serve as conductive channels. For example, the 2DEG can have a density greater than approximately 10⁻⁶. 13 cm -2 The surface charge density of GaN-based HEMTs is high, resulting in low static on-state resistance. Due to their high breakdown field, high electron mobility, low static resistance, and high thermal conductivity, GaN-based HEMTs are attractive for high-frequency and high-power applications. For example, since current can flow from the drain to the source and vice versa in an HEMT during turn-on and can be blocked from flowing from the drain to the source in an HEMT during turn-off, GaN-based HEMTs can be used for bidirectional power switches. Furthermore, the low static on-state resistance of GaN-based HEMTs allows for lower power losses and lower voltage drops in bidirectional switches. In some instances, a GaN-based bidirectional switch may comprise two back-to-back connected HEMTs (e.g., where the drains of the two HEMTs are connected together or the sources of the two HEMTs are connected together) to form a dual-gate bidirectional switch with a common drain region, thereby reducing the total distance between the two terminals of the bidirectional switch and thus reducing the on-state resistance of the bidirectional switch.

[0050] Figure 1A This is a schematic diagram of an example of a bidirectional switch 100 comprising two back-to-back connected transistors. Figure 1A In the example shown, the bidirectional switch 100 may include a first transistor 102 (e.g., an N-MOSFET or HEMT) and a second transistor 106 (e.g., an N-MOSFET or HEMT) connected back-to-back to share a common drain. The resistance of an N-channel MOSFET can be lower than that of a similarly sized P-channel MOSFET, and therefore more suitable for power switching. When the channel is on, there can be a lower voltage drop between the drain and source of transistors 102 and 106. When the gate voltage at the gate G1 of the first transistor 102 and the gate voltage at the gate G2 of the second transistor 106 are appropriately set (e.g., above a threshold voltage) to turn on both the first transistor 102 and the second transistor 106 so that the bidirectional switch 100 is turned on (in the enabled state), current can flow from the source S1 of the first transistor 102 to the source S2 of the second transistor 106 when the voltage level at the source S1 is higher than the voltage level at the source S2, or current can flow from the source S2 of the second transistor 106 to the source S1 of the first transistor 102 when the voltage level at the source S2 is higher than the voltage level at the source S1. The total voltage drop at the turned-on first transistor 102 and second transistor 106 can be low (e.g., close to zero).

[0051] When only one of the first transistor 102 and the second transistor 106 is turned on, current may flow in one direction, but this flow can be blocked in the opposite direction by the off transistor. For example, when the first transistor 102 is turned on and the second transistor 106 is turned off (e.g., by making the gate and source of the second transistor 106 have the same voltage), the second transistor 106 can be configured as a diode or otherwise operate like a diode. Current can flow from source S2 to source S1 through the diode-connected second transistor 106 (which operates in a manner similar to a forward-biased diode) and the first transistor 102 (which is turned on), and the voltage drop between source S2 and source S1 can approach the threshold voltage of the off second transistor 106, but the voltage at source S1 can be blocked from reaching source S2 by the diode-connected second transistor 106, which operates in a manner similar to a reverse-biased diode in blocking said voltage. Similarly, when the first transistor 102 is off (e.g., by making the gate and source of the second transistor 106 have the same voltage) and the second transistor 106 is on, current can be allowed to flow from source S1 to source S2 through the diode-connected first transistor 102 (which operates in a manner similar to a forward-biased diode) and the on second transistor 106, and the voltage drop between source S1 and source S2 can be close to the threshold voltage of the first transistor 102, but the voltage at source S2 can be blocked from reaching source S1 by the first transistor 102, which operates in a manner similar to a reverse-biased diode in blocking said voltage.

[0052] When both the first transistor 102 and the second transistor 106 are turned off, and therefore the bidirectional switch 100 is turned off (disabled), current (or a very small amount of current) is not allowed to flow between the sources S1 and S2. For example, the current from source S1 to source S2 can be blocked by the reverse-biased diode structure 108 formed by the turned-off second transistor 106, while the current from source S2 to source S1 can be blocked by the turned-off first transistor 102.

[0053] As described above, compared to silicon-based transistors, GaN-based HEMTs offer higher breakdown electric field, higher electron mobility, lower on-state resistance, higher current, faster switching speed, higher thermal conductivity, and superior reverse recovery performance. Therefore, they are better suited for applications where low loss and high efficiency are desired, such as power electronic devices or radio frequency (RF) circuits. GaN-based HEMTs allow current to flow from the drain to the source and vice versa when the HEMT is on (on state); they block current flow from the drain to the source when the HEMT is off (off state); and due to, for example, their high electron mobility, they have a lower static on-state resistance than MOSFETs (and therefore lower voltage drop and lower power loss). Therefore, GaN-based HEMTs are suitable for bidirectional switching, offering higher switching speeds and lower power loss and voltage drop. The absence of a body diode in GaN-based HEMTs also eliminates reverse recovery losses caused by the body diode, thus reducing switching losses. Furthermore, due to its side-mounted architecture, monolithic bidirectional switches implemented using GaN-based HEMTs can be fabricated relatively easily. In some instances, GaN-based bidirectional switches may comprise two back-to-back HEMTs to form a dual-gate bidirectional switch with a common drain or a common source.

[0054] Figure 1B This is a cross-sectional view of an example of a monolithic dual-gate bidirectional switch 105, which can be... Figure 1A An example of a bidirectional switch 100 is shown. A bidirectional switch 105 may be a bidirectional power switch implemented using a GaN-based HEMT. In the illustrated example, the bidirectional switch 105 includes two enhancement-mode HEMTs connected back-to-back to share a common drain region 135. The bidirectional switch 105 may include a substrate (not shown), a channel layer 110 grown on the substrate (e.g., comprising an undoped GaN layer), and a barrier layer 120 above the channel layer 110 (e.g., comprising undoped Al). x Ga (1-x) The substrate may comprise, for example, a bulk semiconductor substrate, a semiconductor-on-insulator (SOI) substrate, or another suitable substrate (e.g., a Qromis substrate technology (QST) substrate, a sapphire substrate, or another silicon-based substrate). The GaN material in the channel layer 110 has a greater potential than the Al material in the barrier layer 120. x Ga (1-x) N materials have a narrower band gap. Due to the band gap mismatch, large conduction band offset, and spontaneous polarization and piezoelectric polarization properties of the group III nitride layer, a high-mobility 2DEG can be generated in the channel layer 110 near the heterostructure interface to form a conductive channel in the channel layer 110.

[0055] A first gate structure 130 and a second gate structure 140 may be formed above the barrier layer 120. Each of the first gate structure 130 and the second gate structure 140 may include a p-GaN layer formed above the barrier layer 120 and a gate contact (e.g., a metal gate electrode) formed on the p-GaN layer, which together form a p-GaN gate structure. The p-GaN layer may be a GaN layer doped with, for example, magnesium (Mg). The p-GaN layer may deplete electrons in the 2DEG channel beneath the p-GaN gate structure, such that the path between the source and drain can be disabled when no gate drive voltage is applied to the gate contact. When a positive voltage above a threshold voltage is applied to the gate contact, the gate structure may attract electrons to fill the 2DEG beneath the gate structure, thereby turning on the enhancement-mode HEMT. A first source structure 132 and a second source structure 142 may be formed on or therein of the barrier layer 120. The common drain of the two HEMTs does not need to be touched, and therefore a drain structure does not need to be formed above the barrier layer 120. The source and gate structures can be electrically isolated through one or more dielectric layers (not shown) and can be accessed through interconnects (not shown) formed in the dielectric layers.

[0056] exist Figure 1B In the example shown, the first gate structure 130 of the first HEMT can be controlled by a first driver 150, while the second gate structure 140 of the second HEMT can be controlled by a second driver 160. The first driver 150 may have a reference terminal 152 coupled to the first source structure 132 and a bias terminal 154 (e.g., a power supply terminal) coupled to a voltage source, such that the driver output of the first driver 150 can have an appropriate voltage level relative to the first source structure 132 to properly turn on the first HEMT (e.g., at the voltage difference V between the gate and source). GS Equal to or greater than the threshold voltage V th (when) or turn off the first HEMT (e.g., in V) GS <V th Similarly, the second driver 160 may have a reference terminal 164 coupled to the second source structure 142 and a bias terminal 162 coupled to a voltage source, such that the driver output of the second driver 160 may have an appropriate voltage level relative to the second source structure 142 to properly turn on the second HEMT (e.g., at V). GS ≥V th (when) or turn off the second HEMT (e.g., in V) GS <V th hour).

[0057] As described above, when both the first HEMT and the second HEMT are on, the bidirectional switch 105 can be turned on (in the enabled state), and there can be low resistance and low voltage drop between the first source structure 132 and the second source structure 142. When only one of the first HEMT and the second HEMT is on, since the threshold voltage of the HEMT is not turned on, current can flow in one direction, and there is a voltage drop across the bidirectional switch 105, and current cannot flow in the opposite direction through the off HEMT. When both the first HEMT and the second HEMT are off, the bidirectional switch 105 can be turned off (in the disabled state), and current flow in both directions can be blocked, because current cannot flow from the drain of the unconnected HEMT to the source.

[0058] Additionally, as described above, when the first HEMT is turned on, the second gate structure 140 of the second HEMT can be used as a gate for controlling the switching of the bidirectional switch 105, so that the common drain region 135 can be used as a channel region to block the high voltage at the first source structure 132 from reaching the second source structure 142. Similarly, when the second HEMT is turned on, the first gate structure 130 of the first HEMT can be used as a gate for controlling the switching of the bidirectional switch 105, so that the common drain region 135 can be used as a channel region to block the high voltage at the second source structure 142 from reaching the first source structure 132. In both cases, the common drain region 135 can have a high voltage. Figure 1B As shown, the distance between the gate structure and the corresponding source structure of each HEMT can be relatively short, while the bidirectional switch 105 can still achieve high voltage blocking in both directions due to the shared drain region 135. Because of the shared drain region 135, the total channel length of the bidirectional switch 105 can be much shorter than the total channel length of two independent HEMTs, and therefore the bidirectional switch 105 can have a reduced cell pitch (and thus a smaller device size) and a lower on-resistance (Ron) while achieving high voltage blocking.

[0059] Since the two terminals of bidirectional switches 100 or 105 can be connected to the sources of two transistors and can be at different voltage levels before the bidirectional switch is turned on, different voltage levels can be applied to the gates of the two transistors to turn on the bidirectional switch. Thus, each transistor in the bidirectional switch can be controlled by a driver coupled to the gate of the transistor to provide an appropriate gate voltage. Each driver may have a driver input, a reference terminal (e.g., coupled to the source of the transistor in the bidirectional switch and therefore to the terminal of the bidirectional switch), a bias terminal (e.g., a power supply terminal), and a driver output coupled to the control terminal (e.g., the gate) of the transistor-based bidirectional switch. A bias circuit can be used to set an appropriate bias voltage level at the bias terminals of the drivers so that the outputs of the drivers can properly turn the transistors of the bidirectional switch on or off. Because the reference terminals of the two drivers are coupled to the two terminals of the bidirectional switch, and these two terminals can be at different voltage levels before the bidirectional switch is turned on, the bias terminals of the two drivers can be at different voltage levels so that the outputs of the two drivers can be at different levels to properly turn the two transistors of the bidirectional switch on or off. In some bidirectional switch control circuits, the bias circuit may include two voltage sources to apply different bias voltage levels to the bias terminals of the two drivers.

[0060] Figure 2 This is a schematic diagram of an example of a circuit 200 including a bidirectional switch 210 and circuitry for controlling the bidirectional switch 210. The bidirectional switch 210 may be formed of two transistors (e.g., HEMTs) having a common drain region 215. The bidirectional switch 210 may include a first terminal 212 (S1) that can be coupled to the source of a first transistor and a second terminal 216 (S2) that can be coupled to the source of a second transistor. The first transistor can be controlled by a first driver 220 via a gate 214 (G1), and the second transistor can be controlled by a second driver 230 via a gate 218 (G2). The first driver 220 may include a reference terminal 222, a bias terminal 224, an input terminal 226, and an output terminal 228. The reference terminal 222 may be coupled to the first terminal 212 (S1) of the bidirectional switch 210. The output terminal 228 may be coupled to the gate 214 (G1). The second driver 230 may include a reference terminal 232, a bias terminal 234, an input terminal 236, and an output terminal 238. Reference terminal 232 can be coupled to the second terminal 216 (S2) of bidirectional switch 210. Output terminal 238 can be coupled to gate 218 (G2).

[0061] When a voltage is applied between the first terminal 212 (S1) and the second terminal 216 (S2) and the bidirectional switch 210 is not turned on, the first terminal 212 (S1) and the second terminal 216 (S2) can be at different voltage levels. To turn on the bidirectional switch 210, the voltage level of the gate 214 (G1) can be at least greater than the voltage level of the first terminal 212 (S1) by the threshold voltage of the first transistor, and the voltage level of the gate 218 (G2) can be at least greater than the voltage level of the second terminal 216 (S2) by the threshold voltage of the second transistor. Since the first terminal 212 (S1) and the second terminal 216 (S2) (and therefore reference terminals 222 and 232) can be at different voltage levels, the bias terminals 224 and 234 can also be at different levels, so that the output voltage of the first driver 220 and the output voltage of the second driver 230 can be at different levels to turn on the first transistor and the second transistor. Figure 2 As shown, a first isolation power supply 225 can be used to apply a first bias voltage to the bias terminal 224 across the reference terminal 222 and the bias terminal 224, and a second isolation power supply 235 can be used to apply a second bias voltage to the bias terminal 234 across the reference terminal 232 and the bias terminal 234. Because the voltage levels at the reference terminals 222 and 232 are different, and the voltage levels at the bias terminals 224 and 234 are different, the first isolation power supply 225 or the second isolation power supply 235 cannot be used for both the first driver 220 and the second driver 230.

[0062] According to some examples disclosed herein, the drivers of the two control terminals of a bidirectional switch can receive corresponding bias voltages from a bias generator that generates the corresponding bias voltages using a single voltage supply. The bias generator may have a first input, a second input, a first bias output, and a second bias output. The first input may be coupled to a first switching terminal (e.g., the source of a first transistor) of a bidirectional switch (which may be coupled to a reference terminal of a first driver). The second input may be coupled to a second switching terminal (e.g., the source of a second transistor) of a bidirectional switch (which may be coupled to a reference terminal of a second driver). The first bias output may be coupled to a bias terminal of the first driver, and the second bias output may be coupled to a bias terminal of the second driver.

[0063] Figure 3This is a block diagram of an example of a circuit 300 including a bidirectional switch 310 and circuitry for controlling the bidirectional switch 310. The bidirectional switch 310 may be formed of two transistors (e.g., HEMTs) having a common drain region 315. The bidirectional switch 310 may include a first terminal 312 (S1) that can be coupled to the source of a first transistor and a second terminal 316 (S2) that can be coupled to the source of a second transistor. The first transistor has a gate 314 (G1) and can be controlled by a first driver 320, and the second transistor has a gate 318 (G2) and can be controlled by a second driver 330. The first driver 320 may include a reference terminal 322, a bias terminal 324, an input terminal 326, and an output terminal 328. The reference terminal 322 may be coupled to the first terminal 312 (S1) of the bidirectional switch 310. The output terminal 328 may be coupled to the gate 314 (G1). The second driver 330 may include a reference terminal 332, a bias terminal 334, an input terminal 336, and an output terminal 338. Reference terminal 332 can be coupled to the second terminal 316 (S2) of bidirectional switch 310. Output terminal 338 can be coupled to gate 318 (G2).

[0064] Bias generator 340 generates bias voltages for first driver 320 and second driver 330. Bias generator 340 may include a first input terminal 342, a second input terminal 344, a first bias output terminal 346, and a second bias output terminal 348. The first input terminal 342 is coupled to a reference terminal 322 of the first driver 320 and a first terminal 312 of the bidirectional switch 310 (S1). The second input terminal 344 is coupled to a second reference terminal 332 of the second driver 330 and a second terminal 316 of the bidirectional switch 310 (S2). The first bias output terminal 346 is coupled to a bias terminal 324 of the first driver 320. The second bias output terminal 348 is coupled to a bias terminal 334. Bias generator 340 generates a first bias voltage at the first bias output terminal 346 and a second bias voltage at the second bias output terminal 348 based on a single voltage supply.

[0065] During the commutation transition of the bidirectional switch 310 from an off state to an on state (both transistors of the bidirectional switch are on), the bias generator 340 can provide appropriate bias voltages to the first driver 320 and the second driver 330 so that the two drivers can provide sufficiently high voltages to turn on the first and second transistors of the bidirectional switch 310, respectively. In some instances, the bias generator 340 may include: a maximum voltage selector coupled to a first input 342 and a second input 344 and having an output; an isolation voltage source having a first (e.g., negative) power supply terminal coupled to the output of the maximum voltage selector; a first bootstrap circuit coupled between a second (e.g., positive) power supply terminal of the isolation voltage source and a first bias output 346; and a second bootstrap circuit coupled between a second power supply terminal and a second bias output 348. In one instance, the maximum voltage selector may include a third transistor and a fourth transistor, which may have a common drain terminal coupled to the output of the maximum voltage selector.

[0066] Figure 4 This is a block diagram of an example of a circuit 400 including a bidirectional switch 310 and circuitry for controlling the bidirectional switch 310. Circuit 400 may be an example of circuit 300 and may include the components described above. Figure 3 The first driver 320 and the second driver 330 are described. In circuit 400, bias generator 340 may include a maximum voltage selector 410 that selects the higher of two voltages at a first terminal 312 (S1) and a second terminal 316 (S2), and outputs the higher voltage at output terminal 412. Bias generator 340 may also include an isolated voltage source 420. In some embodiments, isolated voltage source 420 may be a current-isolated voltage power supply. For example, the isolated voltage source 420 may include a transformer with an alternating current (AC) power supply voltage as input on one side (e.g., the primary side) and a voltage rectifier circuit on the other side (e.g., the secondary side) to generate a direct current (DC) voltage. A terminal on the secondary side (e.g., the negative terminal of the isolated voltage source 420) may be coupled to the output 412 of a maximum voltage selector 410, such that the voltage level at the other terminal (e.g., the positive terminal) of the isolated voltage source 420 is the sum of the voltage level at the output 412 of the maximum voltage selector 410 and the DC voltage on the secondary side of the transformer. A first bootstrap circuit 430 and a second bootstrap circuit 440 may be coupled to the positive terminal of the isolated voltage source 420.

[0067] The first bootstrap circuit 430 has an input coupled to a first terminal 312 (S1) and a first bias output 346 coupled to a bias terminal 324 of a first driver 320. The first bootstrap circuit 430 can generate a first bias voltage at the first bias output 346 by bootstrapping the voltage at the first terminal 312 (e.g., by adding a voltage offset to the voltage). This allows the first bias voltage to track the voltage at the first terminal 312, which in turn allows the first driver 320, which receives the first bias voltage, to provide a driver voltage at the output terminal 328 that tracks (and exceeds) the voltage at the first terminal 312. Such a drive voltage allows the voltage difference between the gate 314 and the source S1 (first terminal 312) to exceed a threshold of the first transistor (bidirectional switch 310) having the gate 314, to fully turn on the first transistor, for example, when the voltage at the first terminal 312 (S1) rises from a low voltage to a high voltage due to the bidirectional switch 310 being turned on and connected between the first terminal 312 and a second terminal 316 (S2) having a high voltage.

[0068] Furthermore, the second bootstrap circuit 440 has an input coupled to the second terminal 316 (S2) and a second bias output 348 coupled to the bias terminal 334 of the second driver 330. The second bootstrap circuit 440 can generate a second bias voltage at the second bias output 348 by bootstrapping (e.g., adding a voltage offset to) the voltage at the second terminal 316. This allows the second bias voltage to track the voltage at the second terminal 316, which in turn allows the second driver 330, which receives the second bias voltage, to also provide a driver voltage at the output terminal 338 that tracks (and is offset beyond) the voltage at the second terminal 316. Such a drive voltage allows the voltage difference between the gate 318 and the source S2 (second terminal 316) to exceed the threshold of the second transistor (bidirectional switch 310) with the gate 318, to fully turn on the second transistor, for example, when the voltage at the second terminal 316 (S2) rises from a low voltage to a high voltage due to the bidirectional switch 310 being turned on and connected between the second terminal 316 and the first terminal 312 with a high voltage.

[0069] Furthermore, as described above, both the first bootstrap circuit 430 and the second bootstrap circuit 440 can be coupled to the positive terminal of the isolated voltage source 420. Therefore, both the first bootstrap circuit 430 and the second bootstrap circuit 440 can receive voltages exceeding the maximum voltage between the voltages at the source S1 (first terminal 312) and S2 (second terminal 316). This arrangement ensures that when the first driver 320 raises the voltage at the gate 314 (via the output terminal 328) to turn on the first transistor of the bidirectional switch 310 (e.g., when the voltage at the source S1 rises), charge can flow from the voltage source 420 through the first bootstrap circuit 430 to the first driver 320. This arrangement also ensures that when the second driver 330 raises the voltage at the gate 318 (via the output terminal 338) to turn on the second transistor of the bidirectional switch 310 (e.g., when the voltage at the source S2 rises), charge can flow from the voltage source 420 through the second bootstrap circuit 440 to the second driver 330. Further details regarding the maximum voltage selector 410, the first bootstrap circuit 430, and the second bootstrap circuit 440 are provided below. Figure 5 and Figure 6 Describe it.

[0070] Figure 5 This is a schematic diagram of an example of a circuit 500 including a bidirectional switch 310 and circuitry for controlling the bidirectional switch. Circuit 500 may be an example of circuit 400 and may include the elements described above. Figure 3 and 4 The first driver 320, the second driver 330, and the bias generator 340 are described. The bias generator 340 may include a maximum voltage selector 410, an isolation voltage source 420, a first bootstrap circuit 430, and a second bootstrap circuit 440, as described above regarding... Figure 4 As described.

[0071] In the illustrated example, the maximum voltage selector 410 may include transistors 512 and 514 sharing a common drain terminal 510, which may be the output terminal 412 of the maximum voltage selector 410. Transistors 512 and 514 may form an auxiliary common drain bidirectional switch having a first terminal (e.g., at the source of transistor 512) and a second terminal (e.g., at the source of transistor 514). The first and second terminals of the auxiliary common drain bidirectional switch formed by transistors 512 and 514 may be coupled to the first terminal 312 (S1) and the second terminal 316 (S2) of the bidirectional switch 310, respectively. The gates of transistors 512 and 514 may be coupled to gates 314 (G1) and 318 (G2), respectively. Therefore, the voltage level at the common drain terminal 510 may be similar to the voltage level at the common drain region 315 (which may be inaccessible).

[0072] In one example operation, the voltage level at the first terminal 312 (S1) is higher than that at the second terminal 316 (S2), and the voltage level at the source of transistor 512 (coupled to S1) may also be higher than that at the source of transistor 514 (coupled to S2). Both the first and second transistors of the bidirectional switch 310, as well as transistors 512 and 514, can initially be turned off, wherein the gate and source of each of these transistors are driven to the same voltage. Therefore, the voltage level at the common drain terminal 510 may be similar to the voltage level at the first terminal 312 (S1) (e.g., with a threshold voltage drop). Furthermore, in another example operation, the voltage level at the first terminal 312 (S1) is lower than that at the second terminal 316 (S2), the voltage level at the source of transistor 512 may be lower than that at the source of transistor 514, and therefore the voltage level at the common drain terminal 510 may be similar to (e.g., with a threshold voltage drop) the voltage level at the second terminal 316 (S2). Therefore, the voltage level at the common drain terminal 510 can track the higher of the voltage levels at the first terminal 312 (S1) and the second terminal 316 (S2). As explained, the common drain terminal 510 can be coupled to the negative terminal of the isolation voltage source 420.

[0073] In the illustrated example, the positive terminal of the isolation voltage source 420 may be coupled to the drain of the depletion-type transistor 520 of the first bootstrap circuit 430 and the drain of the depletion-type transistor 530 of the second bootstrap circuit 440. The depletion-type transistor 520 may have a gate terminal coupled to the first terminal 312 of the bidirectional switch 310. When the voltage difference between the gate terminal and the source terminal of the depletion-type transistor 520 is greater than a threshold value (e.g., a negative value, such as -20V), the depletion-type transistor 520 may be in the ON state, such that the voltage level at the source of the depletion-type transistor 520 can be pulled high by the positive terminal of the isolation voltage source 420. When the voltage level at the source of the depletion-type transistor 520 reaches a value such that the voltage difference between the gate terminal and the source terminal of the depletion-type transistor 520 is at or below a threshold value (e.g., ≤-20V), the depletion-type transistor 520 may be turned off. Therefore, the source of depletion-type transistor 520 can be pulled up by transistor 520 to a voltage level approximately a threshold (e.g., 20V) higher than the voltage level at the first terminal 312, and the voltage level at the source of depletion-type transistor 520 tracks (and exceeds) the voltage level at the first terminal 312. For example, if the voltage level at the first terminal 312 is 0V, the source of transistor 520 can be pulled up to 20V. Furthermore, if the voltage level at the first terminal 312 is 600V, the source of transistor 520 can be pulled up to approximately 620V. Additionally, depletion-type transistor 530 can operate in the same manner as depletion-type transistor 520, and therefore the source of depletion-type transistor 530 can be pulled up by transistor 530 to a voltage level approximately a threshold (e.g., 20V) higher than the voltage level at the second terminal 316.

[0074] In some instances, the first bootstrap circuit 430 may further include a diode 522 and a voltage regulator, which may include a source follower 526. The diode 522 allows current to flow from the depletion-type transistor 520 to the source follower 526 but blocks current in the opposite direction. The source follower 526 may include a transistor, with a resistor 524 coupled to the drain and gate terminals of the transistor. The source of the transistor may be coupled to a first bias output 346 of the bias generator 340, which may be coupled to a bias terminal of the first driver 320. The voltage regulator of the first bootstrap circuit 430 may further include a capacitor 528 and a Zener diode 529 coupled to the gate of the transistor in the source follower 526. The capacitor 528 may serve as a filter capacitor to reduce the high-frequency output impedance of the source follower 526. Current can flow from transistor 520 through resistor 524 to Zener diode 529, which, in response to the current, clamps the voltage difference between the gate of source follower 526 and reference terminal 322 of first driver 320 at the forward voltage (e.g., 5V) of the Zener diode. Source follower 526 can provide a voltage at first bias output terminal 346 / bias terminal 324 based on the voltage difference (having a threshold voltage drop) at reference terminal 322, and clamps / regulates the voltage to a certain value based on the voltage difference.

[0075] In some instances, the second bootstrap circuit 440 may include a diode 532 and a source follower 536. The diode 532 allows current to flow from the depletion-type transistor 530 to the source follower 536 but blocks current in the opposite direction. The source follower 536 may include a transistor with a resistor 534 coupled to the drain and gate terminals of the transistor. The source of the transistor in the source follower 536 may be coupled to a second bias output 348 of the bias generator 340, which may be coupled to a bias terminal of the second driver 330. The second bootstrap circuit 440 may also include a capacitor 538 and a Zener diode 539 coupled to the gate of the transistor in the source follower 536. The capacitor 538 may be used as a filter capacitor to reduce the high-frequency output impedance of the source follower 536. Current can flow from transistor 530 through resistor 534 to Zener diode 539, which, in response to the current, clamps the voltage difference between the gate of source follower 536 and reference terminal 332 of second driver 330 at the forward voltage (e.g., 5V) of the Zener diode. Source follower 536 can provide a voltage at second bias output 334 / bias terminal 348 based on the voltage difference (with a threshold voltage drop) at reference terminal 322, and clamps / regulates the voltage at a certain value based on the voltage difference.

[0076] When the voltage level at the second terminal 316 (S2) of the bidirectional switch 310 (e.g., several hundred volts, such as 600V) is higher than the voltage level at the first terminal 312 (S1) before the bidirectional switch 310 is activated (e.g., 0V), the voltage level at the output terminal 412 of the maximum voltage selector 410 (e.g., at the common drain terminal 510) can be close to the voltage level at the second terminal 316 (S2), for example, about 600V minus the threshold voltage of the second transistor. The voltage level at the positive terminal of the isolation voltage source 420 can be higher than the voltage level at the common drain terminal 510 than the supply voltage of the isolation voltage source 420. When the isolation voltage source 420 provides a 20V difference, the positive terminal of the isolation voltage source can be at 620V. Both depletion-type transistors 520 and 530 can initially be in the ON state, such that the sources of depletion-type transistors 520 and 530 can be pulled up at the positive terminal of the isolation voltage source 420. The current used to pull up the source of the depletion-type transistor 520 can, for example, flow from the second terminal 316 through the transistor 514, the isolation voltage source 420, the depletion-type transistor 520, the source follower 526, the first driver 320, and the gate of the transistor 512, to the load at the first terminal 312 of the bidirectional switch 310.

[0077] When the voltage level at the source of depletion-type transistor 520 reaches a certain level (e.g., approximately 20V as explained above), depletion-type transistor 520 can be turned off such that the voltage difference between the gate (e.g., at approximately 0V) and source of depletion-type transistor 520 is equal to the negative threshold voltage of depletion-type transistor 520. When the input terminal 326 of the first driver 320 is controlled to turn on the first transistor of the bidirectional switch 310, the voltage level at the source of depletion-type transistor 520 (e.g., up to approximately 20V) can be applied to the bias terminal 324 through diode 522 and source follower 526. This reduces the voltage level so that the first driver 320 can be properly biased at the bias terminal 324 (e.g., at a voltage approximately 5V higher than that at reference terminal 322) to produce an output that turns on the first transistor of bidirectional switch 310. Due to the voltage difference between the drain and source of the depletion-type transistor 520 and the current flowing through it, power loss may exist in the depletion-type transistor 520 before the first transistor and transistor 512 of the bidirectional switch 310 are turned on. After the first transistor of the bidirectional switch 310 is turned on (e.g., when the voltage across the first transistor is at V...), power loss may occur in the depletion-type transistor 520. GS (Above the Miller plateau), the voltage level at the first terminal 312 can be similar to the voltage level at the second terminal 316 (e.g., about 600V), and the voltage drop between the drain and source of the depletion-type transistor 520 can be lower (and therefore the power loss at the depletion-type transistor 520 can be lower).

[0078] Similarly, when the voltage level at the source of depletion-type transistor 530 reaches a certain level (e.g., approximately 620V as explained above), depletion-type transistor 530 can be turned off such that the voltage difference between the gate (e.g., approximately 600V) and source of depletion-type transistor 530 is lower than the negative threshold voltage of depletion-type transistor 530 (e.g., approximately -20V). When the input terminal 336 of the second driver 330 is controlled to turn on the second transistor of the bidirectional switch 310, the voltage level at the source of depletion-type transistor 530 (e.g., approximately 620V) can be applied to the bias terminal 334 through diode 532 and source follower 536. This reduces the voltage level so that the second driver 330 (e.g., with 600V at reference terminal 332) can be properly biased at the bias terminal 334 (e.g., at approximately 605V) to produce an output that turns on the second transistor of bidirectional switch 310.

[0079] Due to its symmetrical structure, circuit 500 can operate in a similar manner when the voltage level (e.g., several hundred volts, such as 600V) at the first terminal 312 (S1) of the bidirectional switch 310 is higher than the voltage level (e.g., 0V) at the second terminal 316 (S2). Therefore, circuit 500 provides bidirectional voltage blocking and switching.

[0080] Figure 6 This is a schematic diagram of an example of a circuit 600 including a bidirectional switch 310 and circuitry for controlling the bidirectional switch. Circuit 600 may be another example of circuit 400 and may include the elements described above. Figure 3 and 4 The first driver 320, the second driver 330, and the bias generator 340 are described. In the illustrated example, the bias generator 340 may include a maximum voltage selector 410, an isolation voltage source 420, and bootstrap circuits 430 and 440. For example, as described above... Figure 4 As described, the bias generator 340 in circuit 600 may include a bootstrap circuit 430, which may include a depletion-type transistor 520, a diode 522, and a voltage regulator (e.g., including a source follower 526). The bias generator 340 may also include a bootstrap circuit 440, which may include a depletion-type transistor 530, a diode 532, and a voltage regulator (e.g., including a source follower 536). Figure 6In the example shown, diodes 522 and 532 can be omitted. Resistor 524 can be coupled to the drain and gate terminals of source follower 526. The source of source follower 526 can be coupled to the first bias output 346 of bias generator 340, which can be coupled to the bias terminal of first driver 320. Zener diode 529 can adjust the voltage difference between the bias terminal 324 and the reference terminal 322 of first driver 320, such that the voltage difference between the bias terminal 324 and the reference terminal 322 of first driver 320 does not exceed the breakdown voltage of Zener diode 529. Similarly, resistor 534 can be coupled to the drain and gate terminals of source follower 536. The source of source follower 536 can be coupled to the second bias output 348 of bias generator 340, which can be coupled to the bias terminal of second driver 330. The Zener diode 529 can adjust the voltage difference between the bias terminal 334 and the reference terminal 332 of the second driver 330, so that the voltage difference between the bias terminal 334 and the reference terminal 332 of the second driver 330 does not exceed the breakdown voltage of the Zener diode 539.

[0081] exist Figure 6 In the example illustrated, bias generator 340 may further include capacitors 610 and 612 and drivers 620 and 622. Capacitors 610 and 612 may be bootstrap capacitors capable of providing bias voltages to the first driver 320 and the second driver 330. Drivers 620 and 622 may control the gates of source followers 526 and 536 respectively, and may turn off source followers 526 or 536 before the bidirectional switch 310 is turned on, such that before the bidirectional switch 310 is fully turned on (e.g., the voltage of the two transistors is reduced to V0), the bias generator 340 may also include capacitors 610 and 612 and drivers 620 and 622. GS (Greater than the Miller plateau) No charge can flow out of the depletion-type transistors 520 or 530, thus avoiding power loss caused by current flowing through the depletion-type transistors 520 or 530 and the large voltage drop across them before the bidirectional switch 310 is turned on. Before the source followers 526 / 536 are turned on, capacitors 610 and 612 can discharge to provide charge to the first driver 320 and the second driver 330, respectively, so that they can provide voltage to turn on the bidirectional switch 310.

[0082] After the bidirectional switch 310 is turned on (for example, the V of two transistors), GS (Greater than the Miller plateau), the first terminal 312 and the second terminal 316 may have the same or similar voltage levels, and the source followers 526 and 536 can be turned on. When the source followers 526 and 536 are turned on, the depletion-type transistor 520 and diode 522 of the first bootstrap circuit (which in) Figure 6(Optional) and voltage regulator (including source follower 526) and depletion-type transistor 530 and diode 532 (which in the second bootstrap circuit) of the second bootstrap circuit. Figure 6 (Optional) and voltage regulator (including source follower 536) can be as described above regarding Figure 5 The operation described generates two bias voltages at the first bias output terminal 346 and the second bias output terminal 348, which allows capacitors 610 and 612 to be charged to recover the charge lost when the source followers 526 and 536 and the bidirectional switch 310 are turned off.

[0083] For example, after the bidirectional switch 310 is turned on, the common drain terminal 510, the first terminal 312, the second terminal 316, the gate of the depletion-type transistor 520, and the gate of the depletion-type transistor 530 can all be at a high voltage level (e.g., about 600V), while the drains of the depletion-type transistors 520 and 530 can be at a voltage level higher than that at the common drain terminal 510 than the supply voltage of the isolation voltage source 420. Therefore, the voltage level at the source of the depletion-type transistors 520 and 530 can be higher than the voltage level at the gates of the depletion-type transistors 520 and 530 by up to the threshold voltage of the depletion-type transistor (e.g., about 20V). Therefore, the voltage drop between the drain and source of the depletion-type transistor 520 can be low (e.g., close to 0V), and the voltage drop between the drain and source of the depletion-type transistor 530 can be low (e.g., close to 0V). The voltage difference (e.g., up to about 20V) between the source and gate of depletion-type transistor 520 can be regulated by a voltage regulator in the first bootstrap circuit to provide a first bias voltage (e.g., about 5V higher than the voltage level at the first terminal 312) to charge capacitor 610. Similarly, the voltage difference (e.g., up to about 20V) between the source and gate of depletion-type transistor 530 can be regulated by a voltage regulator in the second bootstrap circuit to provide a second bias voltage (e.g., about 5V higher than the voltage level at the second terminal 316) to charge capacitor 612. Because the voltage drop across the current paths used to restore charge on capacitors 610 and 612 (e.g., across depletion-type transistors 520 and 530) is low, the power loss of bias generator 340 can be reduced.

[0084] In some instances, the bias generator 340 may include a minimum voltage selector coupled to a first input terminal 342 and a second input terminal 344 and having an output terminal. The bias generator may also include an isolated voltage source having a first (e.g., negative) power supply terminal coupled to the output terminal of the minimum voltage selector, a first bootstrap circuit coupled between a second (e.g., positive) power supply terminal of the isolated voltage source and a first bias output terminal 346, and a second bootstrap circuit coupled between the second power supply terminal of the isolated voltage source and a second bias output terminal 348. In one instance, the minimum voltage selector may include: a first switch located between the first input terminal 342 and the output terminal of the minimum voltage selector; and a second switch located between the second input terminal 344 and the output terminal of the minimum voltage selector.

[0085] Figure 7 This is a block diagram of an example of a circuit 700 including a bidirectional switch 310 and circuitry for controlling the bidirectional switch. Circuit 700 may be an example of circuit 300 and may include the components described above. Figure 3 The first driver 320 and the second driver 330 are described. In circuit 700, bias generator 340 may include a minimum voltage selector 710 that selects the lower of two voltages at a first terminal 312 (S1) and a second terminal 316 (S2) and outputs the lower voltage at output terminal 712. Bias generator 340 may also include an isolation voltage source 720, which may be similar to the isolation voltage source 420 described above. Voltage source 720 provides a voltage at the positive terminal by adding a voltage offset to the voltage output by minimum voltage selector 710. First bootstrap circuit 730 and second bootstrap circuit 740 may be coupled to the positive terminal of isolation voltage source 720 to generate a first bias voltage at a first bias output terminal 346 coupled to bias terminal 324 of first driver 320 and a second bias voltage at a second bias output terminal 348 coupled to bias terminal 334 of second driver 330. The first and second bias voltages can be generated by bootstrapping relative to the voltage at the positive terminal of voltage source 720. (The following is related to...) Figure 8A and 8B Examples of the minimum voltage selector 710, the first bootstrap circuit 730, and the second bootstrap circuit 740 are described.

[0086] Figure 8A This is a schematic diagram of an example of a circuit 800 including a bidirectional switch 310 and circuitry for controlling the bidirectional switch 310. Circuit 800 may be an example of circuit 700 and may include the elements described above. Figure 3 and 7The first driver 320, the second driver 330, and the bias generator 340 are described. The bias generator 340 in circuit 800 may include a minimum voltage selector 710, an isolation voltage source 720, a first bootstrap circuit 730, and a second bootstrap circuit 740, as described above regarding... Figure 7 As described.

[0087] The minimum voltage selector 710 may have a first input terminal (at the first input terminal 342 of the bias generator 340), a second input terminal (at the second input terminal 344 of the bias generator 340), and an output terminal 712 as described above. As described above, the first input terminal 342 and the second input terminal 344 of the bias generator 340 may be coupled to the first terminal 312 and the second terminal 316, respectively. The first input terminal 342 may be coupled to the output terminal 712 via switch 810, and the second input terminal 344 may be coupled to the output terminal 712 via switch 814. Optional diodes 812 and 816 may ensure that the output terminal 712 is at the lower of the two voltages at the first terminal 312 (S1) and the second terminal 316 (S2). Switches 810 and 814 may be controlled by a circuit (e.g., a voltage comparator not shown) that compares the voltage levels at the first terminal 312 (S1) and the second terminal 316 (S2). When the voltage level at the first terminal 312 (S1) is lower than the voltage level at the second terminal 316 (S2), the switch 810 can be closed, and when the voltage level at the second terminal 316 (S2) is lower than the voltage level at the first terminal 312 (S1), the switch 814 can be closed.

[0088] The first bootstrap circuit 730 may include a capacitor 820 coupled between a reference terminal 322 and a bias terminal 324 of the first driver 320, and a diode 830 coupled between the positive terminal and the bias terminal 324 of the isolation voltage source 720. The second bootstrap circuit 740 may include a capacitor 822 coupled between a reference terminal 332 and a bias terminal 334 of the second driver 330, and a diode 832 coupled between the positive terminal and the bias terminal 334 of the isolation voltage source 720. Capacitors 820 and 822 are bootstrap capacitors to provide a voltage difference between the respective bias terminals and reference terminals of the first driver 320 and the second driver 330. Diodes 830 and 832 are blocking diodes to prevent charge from flowing back from the bootstrap capacitors 820 / 832 to the positive terminal of the voltage source 720 when the voltage at the positive terminal is lower than that at the bias terminal.

[0089] Figure 8B Explanation Figure 8A An example of the operation of circuit 800. In Figure 8BIn the example described, the voltage level (e.g., several hundred volts, such as about 100V) of the first terminal 312 (S1) of the bidirectional switch 310 may be higher than that of the second terminal 316 (S2) (e.g., about 0V before the bidirectional switch 310 is turned on). When the bidirectional switch 310 is in the off state, the gate 314 has the same voltage as the source S1 (first terminal 312) to turn off the first transistor, and the gate 318 has the same voltage as the source S2 (second terminal 316) to turn off the second transistor. Furthermore, since the second terminal 316 has a lower voltage than the first terminal 312, the switch 814 can be closed and the switch 810 can be opened to connect the output terminal 712 to the second terminal 316, so that the output terminal 712 can initially be at about 0V. The isolation voltage source 720 may have a supply voltage, for example, about 5V, and therefore the positive terminal of the isolation voltage source 720 may be at about 5V, and the voltage levels at the first bias output terminal 346 and the second bias output terminal 348 may be close to 5V (for example, slightly below 5V due to the voltage drop across diodes 830 and 832). Therefore, the voltage level at the bias terminal 334 of the second driver 330 may be close to 5V, and the capacitor 822 may be charged to about 5V. Since the bias terminal 334 may be at about 5V and the reference terminal 332 may be at 0V, the second driver 330 may be properly biased such that when a suitable input is received at the second driver 330, it can generate a voltage level at the output terminal 338 and the gate 318 to turn on the second transistor of the bidirectional switch 310.

[0090] During commutation, the bidirectional switch 310 is turned on. The second driver 330 provides a voltage (e.g., 5V) at the output terminal 338 and gate 318 that is sufficiently high relative to the reference terminal 332 to turn on the second transistor, causing current to flow from the first terminal 312 to the second terminal 316. The gate 314 and source (S1) of the first transistor are both at 100V, conducting current and discharging the common drain 315 to a voltage similar to 100V (e.g., having a threshold voltage drop). The current also charges the second terminal 316 so that the voltage level at the second terminal 316 can rise from about 0V to about 100V, and therefore the voltage level at the output terminal 712 can rise from about 0V to about 100V. Thus, the positive terminal of the isolated voltage source 720 can be at about 105V. Charge (from...) Figure 8BArrow 350 indicates that the voltage can flow from the positive terminal of the isolation voltage source 720 through diode 830 to bootstrap capacitor 820, and the voltage level at the first bias output terminal 346 can be close to approximately 105V. Therefore, the voltage difference between the bias terminal 324 of the first driver 320 (e.g., at approximately 105V) and the reference terminal 322 (at approximately 100V) can be approximately 5V, and thus the first transistor of the bidirectional switch 310 can be turned on by the first driver 320. Simultaneously, the bootstrap capacitor 822 can maintain the voltage difference between the bias terminal 334 of the second driver 330 and the reference terminal 334, causing the voltage at the second bias output terminal 348 to also increase (e.g., from 5V to 105V), and the second driver 330 can also provide a sufficiently high voltage (relative to the second terminal 316) to continue turning on the second transistor of the bidirectional switch 310. Thus, both transistors of the bidirectional switch 310 can be turned on, and the bidirectional switch 310 can have a low on-state resistance.

[0091] Due to its symmetrical structure, circuit 800 can operate in a similar manner when the voltage level (e.g., several hundred volts) at the second terminal 316 (S2) of the bidirectional switch 310 is higher than the voltage level (e.g., 0V) at the first terminal 312 (S2). Therefore, circuit 800 provides bidirectional voltage blocking and switching.

[0092] In some instances, the bias generator 340 may include a charge transfer circuit coupled between a first bias output terminal 346 and a second bias output terminal 348. In some instances, the charge transfer circuit may include an auxiliary bidirectional switch. The auxiliary bidirectional switch may be controlled by two auxiliary drivers that receive the same bias voltage and the same reference voltage as the first driver or the second driver. In one instance, the bias generator 340 may further include: a first voltage source (e.g., a first bootstrap capacitor or an isolation voltage supply) coupled between a first input terminal 342 and a first bias output terminal 346; a first startup circuit coupled between a second bias output terminal 348 and a first input terminal 342 and including a first output terminal coupled to the first bias output terminal 346; a second voltage source (e.g., a second bootstrap capacitor or an isolation voltage supply) coupled between a second input terminal 344 and a second bias output terminal 348; and a second startup circuit coupled between a first bias output terminal 346 and a second input terminal 344 and including a second output terminal coupled to the second bias output terminal 348. In another example, the bias generator 340 may include: a voltage power supply having a positive terminal and a negative terminal coupled to a first input terminal 342; a first bootstrap capacitor coupled between the first input terminal 342 and a first bias output terminal 346; a first voltage regulator (e.g., including a source follower) coupled between the positive terminal of the voltage power supply and the first bias output terminal 346; a second bootstrap capacitor coupled between a second input terminal 344 and a second bias output terminal 348; a second auxiliary bidirectional switch having a first terminal coupled to the positive terminal of the voltage power supply; and a second voltage regulator (e.g., including a source follower) coupled between a second terminal of the second auxiliary bidirectional switch and the second bias output terminal 348.

[0093] Figure 9 This is a block diagram of an example of a circuit 900 including a bidirectional switch 310 and circuitry for controlling the bidirectional switch 310. Circuit 900 may be an example of circuit 300 and may include the components described above. Figure 3The first driver 320 and the second driver 330 are described. In circuit 900, bias generator 340 may include a charge transfer circuit 910 (e.g., an overflow circuit) coupled between a first bias output terminal 346 and a second bias output terminal 348. Bias generator 340 may also include a first bootstrap circuit 920 (or voltage source) and a second bootstrap circuit 930 (or voltage source). The first bootstrap circuit 920 may include a bootstrap capacitor 922 (or voltage source) and may be coupled between a first input terminal 342 and a first bias output terminal 346. The second bootstrap circuit 930 may include a bootstrap capacitor 932 (or voltage source) and may be coupled between a second input terminal 344 and a second bias output terminal 348. One of the first bootstrap circuit 920 or the second bootstrap circuit 930 may include or be coupled to a power supply (e.g., an isolated voltage source) to charge the respective bootstrap capacitor 922 / 932. During operation, charge can be transferred from one bootstrap circuit that includes or is coupled to a power source to another bootstrap circuit that does not include (or is not coupled to) a power source to equalize the voltages at the first bias output terminal 346 and the second bias output terminal 348.

[0094] Figure 10 This is a schematic diagram of an example of a circuit 1000 including a bidirectional switch 310 and circuitry for controlling the bidirectional switch 310. Circuit 1000 may be an example of circuit 900 and may include the components described above. Figure 3 and 9 The first driver 320 and the second driver 330 are described. In circuit 1000, bias generator 340 may include a charge transfer circuit, which includes an auxiliary bidirectional switch 1010 and corresponding control circuitry, such as auxiliary drivers 1020 and 1050 for driving the dual gates of the auxiliary bidirectional switch 1010. The charge transfer circuit can transfer charge from a voltage source (e.g., an isolation voltage supply) on one side of the auxiliary bidirectional switch 1010 to a voltage source (e.g., a bootstrap capacitor) on the other side of the auxiliary bidirectional switch 1010.

[0095] In the illustrated example, the bias generator 340 may include a first voltage source 1032 coupled between the bias terminal 324 and the reference terminal 322 of the first driver 320. Figure 10 (represented by a capacitor), and a second voltage source 1062 coupled between the bias terminal 334 and the reference terminal 332 of the second driver 330 (in Figure 10(The first voltage source 1032 may correspond to a first bootstrap circuit 920 (or a portion thereof), and the second voltage source 1062 may correspond to a second bootstrap circuit 930 (or a portion thereof). The first voltage source 1032 may also be coupled between a bias terminal and a reference terminal of an auxiliary driver 1020, and the second voltage source 1062 may also be coupled between a bias terminal and a reference terminal of an auxiliary driver 1050. One terminal (e.g., the positive terminal) of the first voltage source 1032 may be coupled to a first bias output terminal 346 of a bias generator 340. One terminal (e.g., the positive terminal) of the second voltage source 1062 may be coupled to a second bias output terminal 348 of a bias generator 340. One of the first voltage source 1032 and the second voltage source 1062 may be a voltage power supply, such as an isolated voltage power supply similar to the isolated voltage sources 420 or 720 described above. The other of the first voltage source 1032 and the second voltage source 1062 may be a bootstrap capacitor. First voltage source 1032 and second voltage source 1062 can bias first driver 320 and second driver 330 such that first driver 320 and second driver 330 can drive the dual gates of bidirectional switch 310 to turn on the two transistors of bidirectional switch 310 during normal operation. For illustrative purposes, circuit 1000 can be described using an example where first voltage source 1032 can be a voltage power supply and second voltage source 1062 can be a bootstrap capacitor. In another example, second voltage source 1062 can be a voltage power supply and first voltage source 1032 can be a bootstrap capacitor. In both cases, the voltage source / capacitor sets the voltage difference between the bias terminal and the reference terminal of the driver.

[0096] The auxiliary bidirectional switch 1010 may be a common-drain bidirectional switch similar to the bidirectional switch 310, or it may include two transistors whose drain terminals are connected together. For example, the auxiliary bidirectional switch 1010 may include transistors 1012 and 1014. As described above, transistors 1012 and 1014 may be HEMTs, such as GaN-based HEMTs. The source of transistor 1012 may be coupled to the positive terminal of a first bias output 346 and a first voltage source 1032 (e.g., a voltage power supply), while the source of transistor 1014 may be coupled to the positive terminal of a second bias output 348 and a second voltage source 1062 (e.g., a bootstrap capacitor). The gate of transistor 1012 may be driven by the output of auxiliary driver 1020 through charge pump capacitor 1024, and the gate of transistor 1014 may be driven by the output of auxiliary driver 1050 through charge pump capacitor 1054. Charge pump capacitors 1024 and 1054 can provide gate drive voltages higher than those at the outputs of auxiliary drivers 1020 and 1050 and the sources of transistors 1012 and 1014. The charge transfer circuit may also include a diode 1022 coupled between the gate and source of transistor 1012, and a diode 1052 coupled between the gate and source of transistor 1014. When the outputs of auxiliary drivers 1020 or 1050 are at a low voltage level, diodes 1022 and 1052 can increase the voltage level at the gate of transistors 1012 or 1014. After the bidirectional switch 310 is turned on by the drivers 320 and 330 biased by the first voltage source 1032 and the second voltage source 1062, the auxiliary bidirectional switch 1010 can also be turned on by the auxiliary drivers 1020 and 1050 biased by the first voltage source 1032 and the second voltage source 1062. This allows the auxiliary bidirectional switch 1010 (which may have low on-resistance and low voltage drop) to transfer charge from the first voltage source 1032 (e.g., a voltage power supply) to the capacitor of the second voltage source 1062 to replenish the capacitor of the second voltage source 1062, so that the second driver 330 can be properly biased.

[0097] The bias generator 340 may also include a startup circuit 1005 that appropriately biases the drivers of the bidirectional switch 310 and the auxiliary bidirectional switch 1010 when the bootstrap capacitor on the other side of the auxiliary bidirectional switch 1010 has a low voltage during startup. As shown, the startup circuit 1005 may include a bidirectional switch 1040 and a first voltage regulator (optional if the first voltage source 1032 contains a voltage power supply) on one side, and a bidirectional switch 1070 and a second voltage regulator (optional if the second voltage source 1062 contains a voltage power supply) on the other side. The first voltage regulator may include a source follower, which may include a transistor 1030 and a resistor 1036 coupled between the drain and gate of the transistor 1030, a Zener diode 1038 coupled to the gate of the transistor 1030, and a switch 1034 that controls the gate of the transistor 1030. The source of the source follower transistor 1030 may be coupled to the first bias output terminal 346. The bidirectional switch 1040 may include an E-type transistor 1042 and a D-type transistor 1044 with their drains shared or coupled together. Figure 1A and 1B An example of a bidirectional switch 1040 is shown. The second voltage regulator may include a source follower, which may include a transistor 1060 and a resistor 1066 coupled between the drain and gate of the transistor 1060, a Zener diode 1068 coupled to the gate of the transistor 1060, and a switch 1064 controlling the gate of the transistor 1060. The source of the transistor 1060 may be coupled to a second bias output 348. The bidirectional switch 1070 may include an E-type transistor 1072 and a D-type transistor 1074 sharing a common drain or having their drains coupled together. In some embodiments, the first and second voltage regulators may be part of bootstrap circuits 920 and 930, respectively.

[0098] When the bootstrap capacitor on one side of the bidirectional switch 310 is at a low voltage level during startup, the startup circuit 1005 can properly bias the driver of the bidirectional switch 310. For example, when the first voltage source 1032 contains a voltage supply, the first driver 320 can be properly biased and can turn on the first transistor of the bidirectional switch 310, but the second voltage source 1062 (e.g., a capacitor) may be at a low voltage level, so that the second driver 330 may not be properly biased and therefore may not be able to turn on the second transistor of the bidirectional switch 310 during startup. In one example, the second voltage regulator of the bidirectional switch 1070 and the startup circuit 1005 can charge the capacitor of the second voltage source 1062 so that the second driver 330 can be properly biased. For example, when the voltage level of the second voltage source 1062 is low, the D-type transistor 1074 can be in the ON state because the voltage difference between the gate and source of the D-type transistor 1074 (e.g., negative) is greater than the negative threshold voltage (e.g., about -20V). The gate and source of the E-type transistor 1072 can be at the sum of the supply voltage of the first voltage source 1032 and the voltage level of the first terminal 312, which can initially be high, or reach a high level when the second transistor of the bidirectional switch 310 (where its gate and source are at the same voltage) operates in a manner similar to a forward-biased diode and conducts current through the first transistor of the bidirectional switch 310 (which is turned on by the first driver 320). Therefore, the source of the D-type transistor 1074 can be at a level close to the voltage level of the first voltage source 1032 and the first bias output terminal 346. When the voltage level of the second voltage source 1062 is low, the switch 1064 can be turned off, allowing the transistor 1060 of the source follower of the second voltage regulator to be turned on. Therefore, current can flow from the first voltage source 1032 through the bidirectional switch 1070 and the second voltage regulator to the capacitor of the second voltage source 1062 to charge the capacitor, as... Figure 10 As shown, this allows the second driver 330 to be properly biased to turn on the second transistor of the bidirectional switch 310.

[0099] After the capacitor of the second voltage source 1062 is at a high level and the bidirectional switch 310 is turned on, the voltage levels at the first terminal 312 and the second terminal 316 of the bidirectional switch 310 are similar. The auxiliary bidirectional switch 1010 can be turned on for charge transfer (this may be referred to as overflow), and switch 1064 can be turned on to lower the voltage level at the gate of transistor 1060 and turn off the source follower. Therefore, charge cannot be transferred between the first voltage source 1032 and the second voltage source 1062 via the path including the bidirectional switch 1070 and the second voltage regulator, which could result in a larger voltage drop and higher power loss. However, charge can be transferred between the first voltage source 1032 and the second voltage source 1062 via the auxiliary bidirectional switch 1010, which can have a low voltage drop and therefore low power loss, to compensate for the capacitor of the second voltage source 1062.

[0100] If the second voltage source 1062 includes a voltage power supply and the first voltage source 1032 is a capacitor, then the bidirectional switch 1040 and the first voltage regulator in the startup circuit 1005 can be used in a similar manner to that described above regarding the bidirectional switch 1070 and the second voltage regulator.

[0101] Figure 11 This is a schematic diagram of an example of a circuit 1100 including a bidirectional switch 310 and circuitry for controlling the bidirectional switch 310. Circuit 1100 may be an example of circuit 900 and may include the components described above. Figure 3 and 9 The first driver 320 and the second driver 330 are described. In circuit 1100, bias generator 340 may include a charge transfer circuit, which includes an auxiliary bidirectional switch 1110 and corresponding control circuitry, such as auxiliary drivers 1120 and 1150 with dual gates for driving the auxiliary bidirectional switch 1110. The charge transfer circuit can transfer charge, for example, from a voltage power supply 1140 and / or capacitor 1130 to capacitor 1160. Bias generator 340 may also include a startup circuit 1170, which can properly bias the auxiliary driver 1150 when capacitor 1160 has a low voltage when the bidirectional switch 310 is started.

[0102] In the illustrated example, bias generator 340 may include a voltage power supply 1140 coupled to a first voltage regulator, the first voltage regulator including a transistor 1132, a resistor 1134 coupled between the drain and gate of transistor 1132, and a Zener diode 1136 coupled to the gate of transistor 1132. Transistor 1132 may function as a source follower. The source of transistor 1132 may be coupled to capacitor 1130 and a first bias output terminal 346. The first voltage regulator may generate a bias voltage from voltage power supply 1140 at the first bias output terminal 346 to bias the first driver 320 and the auxiliary driver 1120.

[0103] The voltage supply 1140 may also be coupled to a startup circuit 1170. The startup circuit 1170 may include a bidirectional switch 1172 and a second voltage regulator. The second voltage regulator may include a source follower, which may include a transistor 1178 and a resistor 1180 coupled between the drain and gate of the transistor 1178, a Zener diode 1182 coupled to the gate of the transistor 1178, and a switch 1184 controlling the gate of the transistor 1178. The source of the transistor 1178 may be coupled to a second bias output terminal 348 and a capacitor 1160. The bidirectional switch 1172 may include an E-type transistor 1174 sharing a common drain or having their drains coupled together, and a D-type transistor 1176.

[0104] The auxiliary bidirectional switch 1110 may be a common-drain bidirectional switch similar to bidirectional switch 310, or may include two transistors whose drain terminals are connected together. For example, the auxiliary bidirectional switch 1110 may include transistors 1112 and 1114. As described above, transistors 1112 and 1114 may be HEMTs, such as GaN-based HEMTs. The source of transistor 1112 may be coupled to a first bias output terminal 346, while the source of transistor 1114 may be coupled to a second bias output terminal 348. The gate of transistor 1112 may be driven by the output of auxiliary driver 1120 through capacitor 1124 (e.g., a charge pump capacitor), and the gate of transistor 1114 may be driven by the output of auxiliary driver 1150 through capacitor 1154. Capacitors 1124 and 1154 may provide gate drive voltages that may be higher than the outputs of auxiliary drivers 1120 and 1150 and the sources of transistors 1112 and 1114. The charge transfer circuit may further include a diode 1122 coupled between the gate and source of transistor 1112, and a diode 1152 coupled between the gate and source of transistor 1114. When the output of auxiliary driver 1120 or 1150 is at a low voltage level, diodes 1122 and 1152 can increase the voltage level at the gate of transistor 1112 or 1114. After bidirectional switch 310 is turned on by drivers 320 and 330, auxiliary bidirectional switch 1110 can also be turned on by auxiliary drivers 1120 and 1150, which are biased in the same manner as drivers 320 and 330, respectively, so that charge can be transferred from voltage power supply 1140 and / or capacitor 1130 to capacitor 1160 through the low-loss auxiliary bidirectional switch 1110 in the enabled state to replenish capacitor 1160, thereby allowing the second driver 330 to be properly biased.

[0105] The startup circuit 1170 can properly bias the second driver 330 when the capacitor 1160 has a low voltage level during startup of the bidirectional switch 310. For example, during startup, the capacitor 1130 may have a voltage level regulated by the first voltage regulator based on the input from the voltage supply 1140, such that the first driver 320 can be properly biased and can turn on the first transistor of the bidirectional switch 310, but the capacitor 1160 may be at a low voltage level, such that the second driver 330 may not be properly biased, and therefore may not be able to drive the gate of the second transistor of the bidirectional switch 310 to turn on the second transistor of the bidirectional switch 310. The second voltage regulator of the bidirectional switch 1172 and the startup circuit 1170 can charge the capacitor 1160 before startup so that the second driver 330 can be properly biased to turn on the second transistor of the bidirectional switch 310 during startup. For example, when the voltage level of capacitor 1160 is low, D-type transistor 1176 can be turned on because the voltage difference between the gate and source of D-type transistor 1176 is greater than the negative threshold voltage (e.g., about -20V). The gate and source of E-type transistor 1174 can be at the sum of the supply voltage of voltage power supply 1140 and the voltage level of the first terminal 312, which can initially be high, or reach a high level when the second transistor of bidirectional switch 310 (where its gate and source are at the same voltage) operates in a manner similar to a forward-biased diode and conducts current through the first transistor of bidirectional switch 310 (which is turned on by the first driver 320). Therefore, the voltage level of the source of D-type transistor 1074 can be close to the voltage level at the positive terminal of voltage power supply 1140. When the voltage level of capacitor 1160 is low, switch 1184 can be turned off, allowing transistor 1178 of the source follower of the second voltage regulator to be turned on. Therefore, current can flow from the voltage power supply 1140 through the bidirectional switch 1172 and the second voltage regulator to the capacitor 1160 to charge the capacitor 1160, so that the second driver 330 can be properly biased to turn on the second transistor of the bidirectional switch 310, thereby turning on the bidirectional switch 310.

[0106] After capacitor 1160 is at a high level and bidirectional switch 310 is turned on, switch 1184 can be turned on to reduce the voltage at the gate of transistor 1178 to turn off the source follower, and auxiliary bidirectional switches 1110 can be turned on by auxiliary drivers 1120 and 1150 controlled by control gates 1126 and 1156, respectively. For example, at the V of the first transistor in bidirectional switch 310 GS When the voltage exceeds a threshold (e.g., above the Miller plateau), control gate 1126 can control auxiliary driver 1120 to turn on transistor 1112. Similarly, at the V of the second transistor in bidirectional switch 310... GSWhen the voltage exceeds a threshold (e.g., above the Miller plateau), control gate 1156 can control auxiliary driver 1150 to turn on transistor 1114. Therefore, charge can be transferred between capacitor 1130 (and first bias output 346) and capacitor 1160 (and second bias output 348) via auxiliary bidirectional switch 1110, which can have a low voltage drop and therefore low power loss. Since the second source follower of startup circuit 1170 is turned off, charge can be transferred from voltage supply 1140 to capacitor 1160 without the path including bidirectional switch 1172 and second voltage regulator, which can have a large voltage drop and high power loss.

[0107] Figure 12 This is a schematic diagram of an example of circuit 1200, which includes a bidirectional switch 310 and circuitry for controlling the bidirectional switch 310. Circuit 1200 may be another example of circuit 900 and may include the components described above. Figure 3 and 9 The first driver 320 and the second driver 330 are described. In circuit 1200, the bias generator may include bootstrap circuits 1210 and 1250, and bidirectional switches 1230 and 1240, which together form a charge transfer circuit. The charge transfer circuit can transfer charge from a first voltage source (e.g., an isolation voltage source) of the first driver of the bidirectional switch 310 to a second voltage source (e.g., a bootstrap capacitor) of the second driver before and after the bidirectional switch 310 is turned on (for both switch-on and charge overflow). Bootstrap circuits 1210 and 1250 can adjust the bias voltage at the first bias output terminal 346 and the second bias output terminal 348 for both switch-on and charge overflow.

[0108] In the illustrated example, the bootstrap circuit 1210 may include: a first voltage source 1212 (which may be a capacitor or an isolated voltage source) coupled between the bias terminal 324 and the reference terminal 322 of the first driver 320; and a voltage regulator that may include a source follower formed by a transistor 1214 and a resistor 1216 coupled between the drain and source of the transistor 1214, and a Zener diode 1218 coupled between the gate of the transistor 1214 and the reference terminal 322 of the first driver 320 (and the first terminal 312(S1)) of the bidirectional switch 310. The gate of the transistor 1214 may be controlled by a driver 1215, which may in turn be controlled by a detector 1220, which detects the voltage difference (V) between the gate and source of the first transistor of the bidirectional switch 310. GSThe bootstrap circuit 1250 may include: a second voltage source 1252 (which may be a capacitor or an isolation voltage source) coupled between the bias terminal 334 and the reference terminal 332 of the second driver 330 (and the second terminal 316 (S2) of the bidirectional switch 310); and a voltage regulator that may include a source follower formed by the transistor 1254 and a resistor 1256 coupled between the drain and source of the transistor 1254, and a Zener diode 1258 coupled between the gate of the transistor 1254 and the reference terminal 332 of the second driver 330. The gate of the transistor 1254 may be controlled by a driver 1255, which may in turn be controlled by a detector 1260, which detects the voltage difference (V) between the gate and source of the second transistor of the bidirectional switch 310. GS ).

[0109] Bidirectional switch 1230 may include a D-type transistor 1232 and an E-type transistor 1234 with a shared drain or drains coupled together. The source and gate of the D-type transistor 1232 may be coupled to the drain of transistor 1214 and the first terminal 312 (S1) of bidirectional switch 310, respectively. The source and gate of the E-type transistor 1234 may be coupled to a second voltage source 1252 (and a second bias output terminal 348) and a capacitor 1262 (and a diode 1264), respectively. Bidirectional switch 1240 may include a D-type transistor 1244 and an E-type transistor 1242 with a shared drain or drains coupled together. The source and gate of the D-type transistor 1244 may be coupled to the drain of transistor 1254 and the second terminal 316 (S2) of bidirectional switch 310, respectively. The source and gate of the E-type transistor 1242 may be coupled to a first voltage source 1212 (and a first bias output terminal 346) and a capacitor 1222 (and a diode 1224), respectively.

[0110] During operation of the bidirectional switch 310, the first voltage source 1212 and the second voltage source 1252 can bias the first driver 320 and the second driver 330 so that the bidirectional switch 310 can be turned on by the first driver 320 and the second driver 330. After the bidirectional switch 310 is turned on, a charge transfer circuit (e.g., by enabling the source follower in the bootstrap circuit 1210 or 1250) can be activated to transfer charge between the first voltage source 1212 and the second voltage source 1252, thereby recovering the charge lost on the voltage source (e.g., a capacitor) during operation. In some cases, the voltage level of the voltage source may be lower when the bidirectional switch 310 is turned on, and the charge transfer circuit (e.g., by enabling the source follower in the bootstrap circuit 1210 or 1250) can be activated to transfer charge between the first voltage source 1212 and the second voltage source 1252, so that the voltage source with a lower initial voltage level can be charged to a higher voltage level to properly bias the driver, thereby turning on the corresponding transistor of the bidirectional switch 310.

[0111] In one example, the second voltage source 1252 may include a voltage power supply (e.g., an isolated voltage power supply), and the first voltage source 1212 may include a capacitor. During startup and charge transfer (e.g., overflow), charge can be transferred between the second voltage source 1252 and the first voltage source 1212 via the bidirectional switch 1230 and the source follower formed by the transistor 1214. For example, when the first terminal 312 (S1) of the bidirectional switch 310 has a first voltage level (e.g., several hundred volts, such as about 600V) higher than the second voltage level (e.g., 0V) of the second terminal 316 (S2) of the bidirectional switch 310, the common drain region 315 of the bidirectional switch 310 may be at approximately the first voltage level (with a threshold voltage drop) because both the gate and source of the first transistor of the bidirectional switch 310 are at the first voltage level. The second driver 330 can be appropriately biased via the second voltage source 1252, and thus may be able to turn on the second transistor of the bidirectional switch 310. Therefore, the voltage level at the second terminal 316 (S2) of the bidirectional switch 310 can be increased to a level close to the first voltage level, and the voltage level at the second bias output terminal 348 can be equal to the sum of the first voltage level and the power supply voltage of the second voltage source 1252. When the second transistor of the bidirectional switch 310 is turned on by the second driver 330, transistor 1234 can also be turned on by the second driver 330 through capacitor 1262, which can raise the output voltage of the second driver 330 to a level higher than the source voltage level of transistor 1234 by at least the threshold voltage of transistor 1234. As described above, when the output of the second driver 330 is at a low level, diode 1264 can raise the voltage level at the gate of transistor 1234. D-type transistor 1232 can initially conduct to increase the voltage level at the source of D-type transistor 1232 until the voltage level at the source of D-type transistor 1232 is higher than the threshold voltage (e.g., about 20V) than the voltage level at the gate of D-type transistor 1232 (which can be at the first voltage level). The voltage level at the source of the D-type transistor 1232 can be regulated by a voltage regulator in the bootstrap circuit 1210, such that the capacitor of the first voltage source 1212 can be charged to a higher voltage level if the capacitor has a lower initial voltage or is partially depleted during operation. Therefore, the output voltage at the first bias output terminal 346 can be at an appropriate level (e.g., about 5V higher than the voltage level at the first terminal 312 (S1) of the bidirectional switch 310) to provide a power supply voltage to the first driver 320 to fully turn on the first transistor of the bidirectional switch 310. Thus, when the bidirectional switch 310 has a higher voltage level at the first terminal 312 before the bidirectional switch 310 is turned on, the bidirectional switch 1230 and the voltage regulator in the bootstrap circuit 1210 can be used for charge transfer and startup of both.

[0112] When the second terminal 316 (S2) of the bidirectional switch 310 has a first voltage level (e.g., several hundred volts, such as about 600V) higher than the voltage level (e.g., about 0V) of the first terminal 312 (S1) of the bidirectional switch 310, the voltage level at the second bias output terminal 348 can be equal to the sum of the first voltage level and the supply voltage of the second voltage source 1252. Since the gate and source of the second transistor of the bidirectional switch 310 have the first voltage level, the common drain region of the bidirectional switch 310 can be at a level close to the first voltage level (with a threshold voltage drop). The second driver 330 can be properly biased by the second voltage source 1252, and thus can be able to turn on the second transistor of the bidirectional switch 310. However, the first terminal 312 (S1) can still be at a low level because the first transistor or the bidirectional switch 310 can not be turned on (e.g., due to the control signal at the input of the first driver 320 or the low bias voltage at the bias terminal 324). When the second transistor of the bidirectional switch 310 is turned on by the second driver 330, transistor 1234 can also be turned on by the second driver 330 through capacitor 1262. This can boost the output voltage of the second driver 330 to a level higher than the source of transistor 1234 by at least the threshold voltage of transistor 1234 at its gate voltage. D-type transistor 1232 may initially conduct to increase the voltage level at the source of D-type transistor 1232 (which may initially be low) until the voltage level at the source of D-type transistor 1232 is at a level higher than the gate of D-type transistor 1232 (e.g., at about 0V) by a threshold voltage (e.g., about 20V). The voltage level at the source of the D-type transistor 1232 can be regulated by the voltage regulator in the bootstrap circuit 1210, such that the capacitor of the first voltage source 1212 can be charged to a higher voltage level if the capacitor has a lower initial voltage or is partially depleted during operation, and the output voltage at the first bias output terminal 346 can be at an appropriate level (e.g., about 5V higher than the voltage level at the first terminal 312(S1) of the bidirectional switch 310) to supply power to the first driver 320 to turn on the first transistor of the bidirectional switch 310, so that the first terminal 312(S1) of the bidirectional switch 310 can be at a first voltage level (e.g., about 600V). Therefore, when the bidirectional switch 310 has a higher voltage level at the second terminal 316 before the bidirectional switch 310 is turned on, the bidirectional switch 1230 and the voltage regulator in the bootstrap circuit 1210 can also be used for charge transfer and startup of both.

[0113] Detector 1220 can detect the V of the first transistor of bidirectional switch 310. GS In the first transistor of the bidirectional switch 310, V GSBefore the voltage level exceeds a threshold (e.g., above the Miller plateau voltage), the first transistor may not be fully turned on, and the voltage level at the first terminal 312 (S1) may still be significantly lower than the voltage level at the second terminal 316 (S2) (e.g., when the second terminal 316 has a higher initial voltage level). It is expected that charge will be drawn from the first voltage source 1212 (e.g., a capacitor) to power the first driver 320, rather than through the bidirectional switch 1230 (which may have a large voltage drop and therefore greater losses). The detector 1220 can detect lower V... GS And control driver 1215 to turn off the source follower so that charge cannot be drawn through bidirectional switch 1230 to power the first driver 320. At the V of the first transistor in bidirectional switch 310 GS When the voltage exceeds a threshold (e.g., above the Miller plateau voltage), the first transistor of the bidirectional switch 310 can be fully turned on, such that the voltage level at the first terminal 312 is similar to the voltage level at the second terminal 316, and the voltage drop across the bidirectional switch 1230 can be low. The detector 1220 can detect higher V values. GS It also controls the driver 1215 to turn on the source follower so that current can be drawn through the bidirectional switch 1230 and the source follower for charge transfer (overflow).

[0114] Driver 1215 can also be controlled by an undervoltage lockout (UVLO) signal. When the voltage level of the capacitor in the first voltage source 1212 is low, the UVLO signal controls driver 1215 to turn on the source follower transistor 1214. Therefore, current can flow from the second voltage source 1252 through the bidirectional switch 1230 and the source follower to the capacitor in the first voltage source 1212 to charge the capacitor, allowing the first driver 320 to be properly biased to turn on the first transistor in the bidirectional switch 310. When the capacitor in the first voltage source 1212 is high, driver 1215 can lower the voltage level at the gate of transistor 1214 and turn off the source follower, so that current can be drawn from the capacitor in the first voltage source 1212 instead of through the bidirectional switch 1230 (which, as described, can have a large voltage drop and high power loss) to power the first driver 320.

[0115] Therefore, when the voltage level of the capacitor in the first voltage source 1212 is below the threshold, the transistor 1214 can be turned on by the driver 1215 to charge the capacitor through the bidirectional switch 1230. When the voltage level of the capacitor in the first voltage source 1212 is at or above the threshold, the driver 1215 can charge the capacitor through the first transistor of the bidirectional switch 310 as detected by the detector 1220. GSTransistor 1214 is turned off if the voltage drops below the threshold of the first transistor (and therefore the first transistor may be in a pre-Miller state and may not be fully turned on); and the V of the first transistor of the bidirectional switch 310, as detected by detector 1220, is also turned off. GS When the voltage is above the threshold of the first transistor (e.g., above the Miller plateau) and therefore the first transistor is fully turned on, transistor 1214 is turned on to transfer charge (overflow) through bidirectional switch 1230, so that the voltage drop and power loss on the charge transfer path can be lower.

[0116] When the first voltage source 1212 includes a voltage power supply and the second voltage source 1252 is a capacitor, the bidirectional switch 1240 and the second voltage regulator in the bootstrap circuit 1250 can be used to perform charge transfer (overflow) and startup in a manner similar to that described above with respect to the bidirectional switch 1230 and the first voltage regulator in the bootstrap circuit 1210. The detector 1260 and the driver 1255 can operate in a manner similar to that of the detector 1220 and the driver 1215, respectively, to control the source follower in the bootstrap circuit 1250.

[0117] Figure 13 This is a schematic diagram of an example of circuit 1300, which includes a bidirectional switch 310 and circuitry for controlling the bidirectional switch 310. Circuit 1300 may be another example of circuit 900 and may include the components described above. Figure 3 and 9 The first driver 320 and the second driver 330 are described. In circuit 1300, the bias generator may include a bootstrap circuit 1302, a voltage power supply 1310, and a charge transfer circuit, which may include a bidirectional switch 1330 and a drive circuit 1304. The first driver 320 may be powered by the voltage power supply 1310, which may include an isolated power supply as described above. The charge transfer circuit may transfer charge from the voltage power supply 1310 to a second voltage source (e.g., including a capacitor 1340) of the second driver 330.

[0118] The bidirectional switch 1330 may include an E-type transistor 1332 and a D-type transistor 1334 with shared or common drains coupled together. The source and gate of the D-type transistor 1334 may be coupled to the bootstrap circuit 1302 and the second terminal 316 (S2) of the bidirectional switch 310, respectively. The source and gate of the E-type transistor 1332 may be coupled to the voltage power supply 1310 (and the second bias output terminal 348) and the capacitor 1326 (and the diode 1324), respectively. The bidirectional switch 1330 may be controlled by a drive circuit 1304. The drive circuit 1304 may include an auxiliary driver 1320, a control gate 1322, a diode 1324, and a capacitor 1326. The auxiliary driver 1320 may have a reference terminal coupled to the first terminal 312 (S1) of the bidirectional switch 310 and a bias terminal coupled to the voltage power supply 1310 (and the first bias output terminal 346). The auxiliary driver 1320 can be controlled by the control gate 1322 to drive the gate of the E-type transistor 1332 through the capacitor 1326 (e.g., a charge pump capacitor). As described above, when the output of the auxiliary driver 1320 is low, the diode 1324 can pull up the gate of the transistor 1332. The bootstrap circuit 1302 may include a capacitor 1340 and a voltage regulator. The voltage regulator may include a source follower formed by a transistor 1342 and a resistor 1344 coupled between the drain and gate of the transistor 1342, and a Zener diode 1346. The source follower transistor 1342 may be controlled by a driver 1348, which may be controlled by the output of the detector 1362 and the control signal UVLO.

[0119] In one example, the first terminal 312 (S1) of the bidirectional switch 310 may have a first voltage level (e.g., several hundred volts, such as about 600V), which is higher than the second voltage level (e.g., about 0V) of the second terminal 316 (S2) of the bidirectional switch 310. Before the bidirectional switch 310 is turned on, the common drain region 315 of the bidirectional switch 310 may be close to the first voltage level (having a threshold voltage drop) because the gate and source of the first transistor of the bidirectional switch 310 are at the first voltage level, but the second terminal 316 (S2) of the bidirectional switch 310 may remain at a low voltage level. GS The second transistor V of the bidirectional switch 310 reaches the threshold. GSBefore the threshold is reached, the auxiliary driver 1320 can be left uncontrolled to turn on the transistor 1332 of the bidirectional switch 1330, and the detector 1362 can control the driver 1348 to turn off the transistor 1342, so that current does not flow in the path from the voltage power supply 1310 through the charge transfer circuit to the capacitor 1350. Before the bidirectional switch 310 is turned on, the path may have a large voltage drop due to the large voltage difference between the first terminal 312 (S1) and the second terminal 316 (S2) of the bidirectional switch 310, and therefore may have a large power loss if current flows in this path.

[0120] To turn on the bidirectional switch 310, a first driver 320, powered by a voltage supply 1310, can be controlled to drive the gate of the first transistor in the bidirectional switch 310 to turn on the first transistor. A second driver 330, powered by a capacitor 1340, can be controlled to turn on the second transistor in the bidirectional switch 310. Therefore, the voltage level at the second terminal 316 (S2) and the gate of transistor 1334 can be at the first voltage level at the first terminal 312 (S1) (e.g., approximately 600V). After the bidirectional switch 310 is turned on, for example, at V... GS The threshold voltage V of the two transistors of the bidirectional switch is greater than the threshold voltage V. TH When (e.g., above the Miller plateau voltage), the auxiliary driver 1320, biased by the voltage supply 1310, can be controlled by the control gate 1322 to turn on the transistor 1332. The source level of the transistor 1332 can be equal to the sum of the first voltage level at the first terminal 312 and the supply voltage of the voltage supply 1310. Because the transistor 1334 is a D-type transistor, the bidirectional switch 1330 can be in the ON state and have low resistance until the voltage level at the source of 1334 is about a threshold level (e.g., about 20V) higher than the voltage level at the gate of the transistor 1334 (e.g., about 600V). Therefore, the voltage level at the source of the transistor 1332 can be about the same as the voltage level at the source of the transistor 1334.

[0121] Detector 1362 can detect the V of the second transistor of bidirectional switch 310. GS Furthermore, the driver 1348 can control the transistor 1342 to turn on because the second transistor of the bidirectional switch 310 is fully turned on, and therefore the V of the second transistor of the bidirectional switch 310... GSThis voltage level can be greater than a threshold (e.g., above the Miller plateau). When transistor 1342 is turned on, the voltage difference between the source and gate of transistor 1334 (e.g., up to about 20V) can be regulated by the voltage regulator of bootstrap circuit 1302 to an appropriate voltage level (e.g., about 5V) at the second bias output terminal 348, so that charge can be transferred to capacitor 1340 to replenish it. Due to the low voltage drop along the charge transfer path, the loss during charge transfer can be low.

[0122] During the startup of bidirectional switch 310, when the voltage level of capacitor 1340 is low, the second driver 330 may not initially turn on the second transistor of bidirectional switch 310, and the voltage level at the second terminal 316 may remain low (e.g., about 0V). The gate and source of transistor 1332 have the same voltage, and the common drain of bidirectional switch 1330 may have a voltage level close to the voltage levels of the source and gate of transistor 1332 (with a threshold voltage drop). Alternatively or additionally, an auxiliary driver 1320 biased by voltage supply 1310 may be controlled by control gate 1322 to turn on transistor 1332. Because transistor 1334 is a D-type transistor, bidirectional switch 1330 may be in the ON state until the voltage level at the source of transistor 1334 is approximately a threshold level higher than the voltage level at the gate of transistor 1334 (e.g., about 0V). Driver 1348 can be controlled by control signal UVLO to turn on transistor 1342 of the source follower in the voltage regulator when the voltage level of capacitor 1340 is low. When transistor 1342 is turned on, the voltage difference between the gate and source of transistor 1334 can be adjusted by the voltage regulator of bootstrap circuit 1302 to an appropriate voltage level at the second bias output terminal 348 (e.g., about 5V higher than the voltage level at the second terminal 316), so that capacitor 1340 can be charged to a level that can properly bias the second driver 330 to turn on the second transistor of bidirectional switch 310 (and thus turn on bidirectional switch 310). After the voltage of capacitor 1340 exceeds a threshold, driver 1348 can be controlled to turn off transistor 1342. Therefore, when the first terminal 312 has a higher voltage than the second terminal 316 before the bidirectional switch 310 is turned on, the voltage regulators of the bootstrap circuit 1302, the bidirectional switch 1330, and the drive circuit 1304 can be used for charge transfer and start-up of the bidirectional switch 310.

[0123] In another example, the second terminal 316 (S2) of the bidirectional switch 310 may have a first voltage level (e.g., several hundred volts, such as about 600V) higher than the second voltage level (e.g., 0V) of the first terminal 312 (S1) of the bidirectional switch 310. Before the bidirectional switch 310 is turned on, since the gate and source of the second transistor of the bidirectional switch 310 are at the first voltage level, the common drain region of the bidirectional switch 310 may be at the first voltage level (with a threshold voltage drop), but the first terminal 312 (S1) of the bidirectional switch 310 may remain at a low voltage level. At the V of the first transistor of the bidirectional switch 310... GS The second transistor of the bidirectional switch 310 reaches a threshold (e.g., above the Miller plateau voltage) and V GS Before reaching a threshold (e.g., above the Miller plateau voltage), the auxiliary driver 1320 may not be controlled to turn on the transistor 1332 of the bidirectional switch 1330, and the detector 1362 may control the driver 1348 to turn off the transistor 1342, so that current may not flow through the bidirectional switch 1330 from the voltage supply 1310 to the capacitor 1340. Because the voltage difference between the first terminal 312 (S1) and the second terminal 316 (S2) of the bidirectional switch 310 is large, the path can have a large voltage drop, and therefore a large power loss when current flows through this path.

[0124] To turn on the bidirectional switch 310, a first driver 320, biased by a voltage supply 1310, can be controlled to drive the gate of the first transistor in the bidirectional switch 310 to turn on the first transistor. A second driver 330, biased by a capacitor 1340, can be controlled to turn on the second transistor in the bidirectional switch 310. Therefore, the voltage level at the first terminal 312 (S1) can rise from approximately 0V to a first voltage level at the second terminal 316 (S2) (e.g., approximately 600V). After the bidirectional switch 310 is turned on, for example, at V... GS When the threshold voltage of the two transistors of the bidirectional switch 310 is greater than that of the transistor (e.g., higher than the Miller plateau voltage), the auxiliary driver 1320, biased by the voltage supply 1310, can be controlled by the control gate 1322 to turn on the transistor 1332. Since the transistor 1334 is a D-type transistor, the bidirectional switch 1330 can remain on until the voltage level at the source of the transistor 1334 is approximately 20V higher than the voltage level at the gate of the transistor 1334 (e.g., approximately 600V). The detector 1362 can detect the Vt of the second transistor of the bidirectional switch. GSThe driver 1348 can control the transistor 1342 to turn on. Therefore, the voltage difference between the gate and source of transistor 1334 can be adjusted by the voltage regulator of the bootstrap circuit 1302 to an appropriate voltage level at the second bias output terminal 348 (e.g., approximately 5V above the first voltage level), so that charge can be transferred to capacitor 1340 to replenish it. Since both the first terminal 312 (S1) and the second terminal 316 (S2) are at approximately the first voltage level, the source of transistor 1332 can be at a voltage level approximately equal to the sum of the first voltage level and the voltage of the voltage supply 1310, and the source of transistor 1334 can be at a level approximately equal to or less than the sum of the absolute value of the first voltage level and the threshold voltage of transistor 1334. Therefore, the voltage drop across the bidirectional switch 1330 is low, and the charge transfer loss is low.

[0125] If the voltage level of capacitor 1340 is low during the activation of bidirectional switch 310, the second transistor of bidirectional switch 310 may not initially be turned on, and the voltage level at the first terminal 312 may remain low. The first driver 320 may turn on the first transistor of bidirectional switch 310 such that, since the gate and source of the second transistor of bidirectional switch 310 are at the first voltage level, the voltage level at the first terminal 312 (S1) may approach the first voltage level at the second terminal 316 (with a threshold voltage drop). The auxiliary driver 1320, biased by voltage supply 1310, may be controlled by control gate 1322 to turn on transistor 1332. Therefore, bidirectional switch 1330 may be in the on state until the voltage level at the source of D-type transistor 1334 is approximately a threshold level (e.g., approximately 20V) higher than the voltage level at the gate of transistor 1334 (e.g., approximately 600V). When the voltage level of capacitor 1340 is low, driver 1348 can be controlled by control signal UVLO to turn on transistor 1342 of the source follower in the voltage regulator. Therefore, the voltage difference between the gate and source of transistor 1334 can be adjusted by the voltage regulator of bootstrap circuit 1302 to an appropriate voltage level at the second bias output terminal 348 (e.g., about 5V higher than the voltage level at the second terminal 316) so that capacitor 1340 can be charged to a level that properly biases the second driver 330 to turn on the second transistor of bidirectional switch 310 (and thus turns on bidirectional switch 310). Therefore, when the first terminal 312 has a voltage lower than the second terminal 316 before bidirectional switch 310 is turned on, the voltage regulators of bootstrap circuit 1302, bidirectional switch 1330, and driver circuit 1304 can be used for charge transfer and activation of bidirectional switch 310.

[0126] Therefore, in circuit 1300, when the voltage level of capacitor 1340 is below a threshold, transistor 1342 can be turned on by driver 1348 to charge capacitor 1340 via bidirectional switch 1330. When the voltage level of capacitor 1340 is at or above the threshold, driver 1348 can activate the second transistor of bidirectional switch 310 as detected by detector 1362. GS Transistor 1342 is turned off if the voltage drops below the threshold of the second transistor (and therefore the second transistor may be in a pre-Miller state and may not be fully turned on); and the second transistor of the bidirectional switch 310 may be turned off if the voltage drops below the threshold detected by detector 1362. GS When the threshold of the second transistor is higher than that of the second transistor (e.g., higher than the Miller plateau) and therefore the second transistor is fully turned on, transistor 1342 is turned on to transfer charge (overflow) through bidirectional switch 1330, so that power loss on the charge transfer path can be lower.

[0127] As described above, the bidirectional power switch disclosed herein can be used in power switch matrices or switch networks, such as N×M power switch networks. In one example, the power switch network can be used as a matrix converter for AC power conversion. Using the techniques disclosed herein, the number of power supplies required to bias a large number of bidirectional switches in a switch matrix can be significantly reduced because two drivers of dual-gate bidirectional switches with different reference voltages can share the same voltage supply.

[0128] Figure 14A This is a schematic diagram of an example of a matrix converter 1400. The matrix converter 1400 may include three input ports and two output rails, which are connected by a switch matrix containing six bidirectional switches, such as the dual-gate bidirectional switch based on GaN HEMT described above. The three input ports may include input ports A, B, and C. Each input port may be coupled to the switch matrix via inductors 1410, 1412, or 1414. The two output rails may include a first output rail 1402 and a second output rail 1404. The switch matrix may include bidirectional switches 1420, 1422, and 1424, respectively, coupled between the first output rail 1402 and input ports A, B, and C. The switch matrix may also include bidirectional switches 1426, 1428, and 1430, respectively, coupled between the second output rail 1404 and input ports A, B, and C.

[0129] In the illustrated example, each bidirectional switch may include a drive circuit that uses two voltage sources to bias the two drivers of the bidirectional switch, as described above. Figure 2As described. Because one terminal of each of the bidirectional switches 1420, 1422, and 1424 is coupled to the first output rail 1402 and has the same voltage level (and therefore the same reference voltage for the driver), the drive circuitry for bidirectional switches 1420, 1422, and 1424 can share an isolation voltage power supply 1432. Similarly, because one terminal of each of the bidirectional switches 1426, 1428, and 1430 is coupled to the second output rail 1404 and has the same voltage level, the drive circuitry for bidirectional switches 1426, 1428, and 1430 can share an isolation voltage power supply 1440. One terminal of bidirectional switch 1420 and one terminal of bidirectional switch 1426 can both be coupled to input port A through inductor 1410 and have the same voltage level. Therefore, the drive circuitry for bidirectional switches 1420 and 1426 can share an isolation voltage power supply 1434. One terminal of bidirectional switch 1422 and one terminal of bidirectional switch 1428 can both be coupled to input port B through inductor 1412 and have the same voltage level. Therefore, the drive circuits of bidirectional switches 1422 and 1428 can share the isolation voltage power supply 1436. One terminal of bidirectional switch 1424 and one terminal of bidirectional switch 1430 can both be coupled to input port C through inductor 1414 and have the same voltage level. Therefore, the drive circuits of bidirectional switches 1422 and 1428 can share the isolation voltage power supply 1438. In this way, five isolated voltage power supplies can properly bias the drive circuit of matrix converter 1400.

[0130] Figure 14B This is a schematic diagram of an example of a matrix converter 1450 with a shared bias power supply. Similar to matrix converter 1400, matrix converter 1450 may include three input ports and two output rails connected by a switch matrix with six bidirectional switches (e.g., a dual-gate bidirectional switch based on GaN HEMT described above). The three input ports may include input ports A, B, and C. Each input port may be coupled to the switch matrix via inductors 1460, 1462, or 1464. The two output rails may include a first output rail 1452 and a second output rail 1454. The switch matrix may include bidirectional switches 1470, 1472, and 1474 coupled between the first output rail 1452 and input ports A, B, and C, respectively. The switch matrix may also include bidirectional switches 1476, 1478, and 1480 coupled between the second output rail 1454 and input ports A, B, and C, respectively.

[0131] exist Figure 14B In the examples shown, each bidirectional switch may include a bias generator that uses a voltage source to generate two bias voltages to bias the two drivers of the bidirectional switch, as described above. Figures 3 to 13As described. For example, bidirectional switch 1470 may include bias generator 1470a, bidirectional switch 1472 may include bias generator 1472a, bidirectional switch 1474 may include bias generator 1474a, bidirectional switch 1476 may include bias generator 1476a, bidirectional switch 1478 may include bias generator 1478a, and bidirectional switch 1480 may include bias generator 1480a. Furthermore, because bidirectional switches 1470, 1472, and 1474 are all coupled to the first output rail 1452, the bias generators 1470a, 1472a, and 1474a of bidirectional switches 1470, 1472, and 1474 may be coupled to the same isolation voltage supply 1482 to generate bias voltages for biasing the six drivers. Similarly, because bidirectional switches 1476, 1478, and 1480 are all coupled to the second output rail 1454, the bias generators 1476a, 1478a, and 1480a of the bidirectional switches 1476, 1478, and 1480 can each be coupled to the same isolated voltage supply 1484 to generate bias voltages for biasing the six drivers. Therefore, two isolated voltage supplies can be used to properly bias all the drive circuitry of the matrix converter 1450. Compared to the matrix converter 1400, the matrix converter 1450 can use fewer isolated voltage supplies by using the bias generation circuitry disclosed herein. The number of isolated voltage supplies used to bias the drivers can be reduced even more significantly when the switch matrix contains more bidirectional switches.

[0132] Figure 15 This is a cross-sectional view of an example of a monolithic bidirectional switch 1500, which includes an E-type transistor / switch and a D-type transistor / switch sharing a common drain region 1502. The bidirectional switch 1500 can be... Figures 10 to 13 Examples of bidirectional switches 1040, 1070, 1172, 1230, 1240, and 1330. For example... Figure 15 As shown, the bidirectional switch 1500 may include a substrate (not shown), a channel layer 1510 grown on the substrate (e.g., comprising an undoped GaN layer), and a barrier layer 1520 above the channel layer 1510 (e.g., comprising undoped Al). x Ga (1-x) The substrate may comprise, for example, a bulk semiconductor substrate, a semiconductor-on-insulator (SOI) substrate, or another suitable substrate (e.g., a Qromis substrate technology (QST) substrate, a sapphire substrate, or another silicon-based substrate). The GaN material in the channel layer 1510 has a greater potential than the Al material in the barrier layer 1520. x Ga (1-x)N materials have a narrower band gap. Due to the band gap mismatch, large conduction band offset, and spontaneous polarization and piezoelectric polarization properties of the group III nitride layer, high-mobility 2DEG can be generated in the channel layer 1510 near the heterostructure interface to form a conductive channel in the channel layer 1510.

[0133] A first gate structure 1530 may be formed above a barrier layer 1520. The first gate structure 1530 may include a p-GaN layer formed above the barrier layer 1520 and gate contacts (e.g., metal gate electrodes) formed on the p-GaN layer, which together form the p-GaN gate structure of an E-type transistor. The p-GaN layer may be a GaN layer doped with, for example, magnesium (Mg). The p-GaN layer can deplete electrons in the 2DEG channel beneath the p-GaN gate structure, such that the path between the source and drain can be disabled when no gate drive voltage is applied to the gate contacts. When a positive voltage above the gate threshold voltage is applied to the gate contacts, the gate structure can attract electrons to fill the 2DEG beneath the gate structure, thereby turning on the enhancement-mode / E-type transistor. The first source structure 1532 of the E-type transistor may be formed on or within the barrier layer 1520. A dielectric layer 1536 (e.g., silicon nitride (SiN)) covers the first gate structure 1530 and the first source structure 1532.

[0134] Furthermore, a second gate structure 1540 of the depletion-type / D-type transistor may be formed above the dielectric layer 1536. The second gate structure 1540 may be a metal layer. The second gate structure 1540 may accept a negative voltage to deplete electrons in the 2DEG channel below the second gate structure 1540, thereby turning off the D-type transistor. In the absence of a negative voltage, the path between the source and drain of the D-type transistor remains enabled. The second source structure 1542 of the D-type transistor may be formed on or within the barrier layer 1520 and covered by the dielectric layer 1536.

[0135] In this description, the term "coupled" may encompass a connection, communication, or signaling path that achieves a functional relationship consistent with this description. For example, if device A generates a signal to control device B to perform an action: (a) in a first instance, device A is coupled to device B via a direct connection; or (b) in a second instance, if intermediate component C does not alter the functional relationship between device A and device B, then device A is coupled to device B via intermediate component C such that device B is controlled by control signals generated by device A.

[0136] Furthermore, in this specification, the expression "based on" means "at least partially based on". Therefore, if X is based on Y, then X may vary with Y and any number of other factors.

[0137] A device “configured to” perform a task or function may be configured (e.g., programmed and / or hardwired) to perform a function during manufacturing by the manufacturer, and / or may be configured (or reconfigurable) by the user after manufacturing to perform a function and / or other additional or alternative functions. Configuration may be achieved through firmware and / or software programming of the device, through the construction and / or layout of hardware components, and through the interconnection of the device or a combination thereof.

[0138] As used herein, the terms “terminal,” “node,” “interconnect,” “pin,” and “lead” are used interchangeably. Unless specifically stated otherwise, these terms are generally used to refer to interconnections or ends between device elements, circuit elements, integrated circuits, devices, or other electronic or semiconductor components.

[0139] The circuits or devices described herein as containing certain components may be practically adapted to be coupled to those components to form the described circuit system or device. For example, a structure described as containing one or more semiconductor elements (e.g., transistors), one or more passive elements (e.g., resistors, capacitors, and / or inductors), and / or one or more power sources (e.g., voltage and / or current sources) may alternatively contain only semiconductor elements within a single physical device (e.g., a semiconductor die and / or integrated circuit (IC) package) and may be adapted to be coupled to at least some passive elements and / or sources to form the described structure, for example, by an end user and / or a third party at or after manufacturing.

[0140] While the use of specific transistors is described herein, other transistors (or equivalent devices) may be used alternatively with minimal alteration to the rest of the circuit system. For example, field-effect transistors (“FETs”) (e.g., n-channel FETs (NFETs) or p-channel FETs (PFETs)), bipolar junction transistors (BJTs, e.g., NPN or PNP transistors), insulated-gate bipolar transistors (IGBTs), and / or junction field-effect transistors (JFETs) may be used in place of or in combination with the devices described herein. Transistors may be depletion-mode devices, drain-extended devices, enhancement-mode devices, natural transistors, or other types of device structure transistors. Furthermore, the devices may be implemented on / above a silicon (Si) substrate, a silicon carbide (SiC) substrate, a gallium nitride (GaN) substrate, or a gallium arsenide (GaAs) substrate.

[0141] The claims may refer to the control input terminal and its current terminals of the transistor. In the context of a FET, the control input terminal is the gate, and the current terminals are the drain and source. In the context of a BJT, the control input terminal is the base, and the current terminals are the collector and emitter.

[0142] In this article, "FET on" or "enabled" means that a conductive channel exists in the FET and drain current can flow through it. "FET off" or "disabled" means that no conductive channel exists, and therefore drain current does not flow through the FET. However, a "disabled" FET can have current flowing through the body diode of the transistor.

[0143] The circuits described herein can be reconfigured to include additional or different components to provide functionality at least partially similar to that available before the component replacement. Unless otherwise stated, components shown as resistors generally represent any one or more elements coupled in series and / or parallel to provide the impedance represented by the resistor shown. For example, a resistor or capacitor shown and described herein as a single component may alternatively be multiple resistors or capacitors coupled in parallel between the same nodes. For example, a resistor or capacitor shown and described herein as a single component may actually be multiple resistors or capacitors coupled in series between the same two nodes as the single resistor or capacitor.

[0144] While some elements in the described examples are contained within the integrated circuit and others are external to the integrated circuit, in other examples, additional or fewer features may be incorporated into the integrated circuit. Furthermore, some or all of the features described as external to the integrated circuit may be contained within the integrated circuit, and / or some features described as internal to the integrated circuit may be incorporated externally. As used herein, the term "integrated circuit" means (i) incorporated in / above a semiconductor substrate; (ii) incorporated in a single semiconductor package; (iii) incorporated in the same module; and / or (iv) incorporated in / on the same printed circuit board.

[0145] The use of the phrase “grounding” in the preceding description includes chassis grounding, ground wire grounding, floating grounding, virtual grounding, digital grounding, general grounding, or any other form of grounding connection that is applicable to or suitable for the teachings of this description.

[0146] In this specification, unless otherwise stated, “about,” “approximately,” or “generally” preceding a parameter means within + / - 10% of the parameter, or, if the parameter is zero, within a reasonable range of values ​​approximately zero.

[0147] As used herein, the terms “and” and “or” can have a variety of meanings, and are expected to depend at least in part on the context in which they are used. Generally, “or” used to relate, for example, a list of A, B, or C, is intended to mean A, B, and C (used herein in an inclusive sense), and A, B, or C (used herein in an exclusive sense). Additionally, the term “one or more” as used herein can be in the singular form to describe any feature, structure, or characteristic, or to describe a combination of features, structures, or characteristics. However, it should be noted that this is merely an illustrative example, and the claimed subject matter is not limited to this example. Furthermore, the term “at least one of” used to relate, for example, a list of A, B, or C, can be interpreted as meaning A, B, C, or a combination of A, B, and / or C, such as AB, AC, BC, AA, ABC, AAB, ACC, AABBCCC, etc.

[0148] Although various examples have been described in detail, it should be understood that various changes, substitutions, and modifications can be made therein without departing from the scope defined by the appended claims. The apparatus, structure, material, and process discussed above are examples. Various procedures or components may be omitted, substituted, or added where appropriate in various examples. Furthermore, features described with respect to certain examples may be combined in various other examples. Different aspects and elements of examples may be combined in a similar manner. Moreover, technological evolution, and therefore numerous elements, do not limit the scope of this disclosure to examples of those particular examples.

[0149] Specific details are provided in the description to offer a thorough understanding of the examples. However, the examples can be practiced without these specific details. For example, well-known circuits, processes, systems, structures, and techniques may be shown without unnecessary details to avoid obscuring the examples. This description is merely illustrative and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the foregoing description of the examples will provide a illustrative description for those skilled in the art to implement various examples. Various changes can be made to the function and arrangement of the elements without departing from the spirit and scope of this disclosure. Modifications can be made to the described examples within the scope of the claims, and other examples are possible.

Claims

1. A circuit comprising: The first driver has a first bias terminal, a first reference terminal, a first driver input terminal and a first driver output terminal; The second driver has a second bias terminal, a second reference terminal, a second driver input terminal, and a second driver output terminal; and A bias generator has a first input terminal, a second input terminal, a first bias output terminal, and a second bias output terminal, wherein the first input terminal is coupled to a first reference terminal, the second input terminal is coupled to a second reference terminal, the first bias output terminal is coupled to the first bias terminal, and the second bias output terminal is coupled to the second bias terminal, wherein the bias generator is configured to generate a first bias voltage at the first bias output terminal and a second bias voltage at the second bias output terminal based on a power supply voltage.

2. The circuit of claim 1, wherein the bias generator comprises: A maximum voltage selector, coupled between the first input terminal and the second input terminal and having an output terminal; A voltage source having a first power terminal and a second power terminal, the first power terminal being coupled to the output terminal of the maximum voltage selector; A first bootstrap circuit is coupled between the second power supply terminal and the first bias output terminal; and The second bootstrap circuit is coupled between the second power supply terminal and the second bias output terminal.

3. The circuit of claim 2, wherein the maximum voltage selector comprises a third transistor and a fourth transistor, the third transistor and the fourth transistor having a common drain terminal coupled to the output terminal of the maximum voltage selector.

4. The circuit according to claim 3, wherein: The third transistor has a third gate and a third source, the third gate being coupled to the output of the first driver, and the third source being coupled to the first input of the bias generator; and The fourth transistor has a fourth gate and a fourth source, the fourth gate being coupled to the output of the second driver, and the fourth source being coupled to the second input of the bias generator.

5. The circuit according to claim 2, wherein the first bootstrap circuit comprises: A depletion-type transistor having a drain terminal, a gate terminal, and a source terminal, the drain terminal being coupled to a second power supply terminal, and the gate terminal being coupled to a first input terminal of the bias generator; and A source follower coupled between the first bias output of the bias generator and the source terminal of the depletion-type transistor.

6. The circuit according to claim 5, wherein: The first bootstrap circuit includes a diode coupled between the source follower and the source terminal of the depletion-type transistor; The source follower includes a control terminal coupled to a control driver; and The bias generator includes a capacitor coupled between the first bias output terminal and the first input terminal of the bias generator.

7. The circuit of claim 1, wherein the bias generator comprises: A minimum voltage selector, coupled between the first input terminal and the second input terminal and having an output terminal; A voltage source having a first power terminal and a second power terminal, the first power terminal being coupled to the output terminal of the minimum voltage selector; A first bootstrap circuit is coupled between the second power supply terminal and the first bias output terminal; and The second bootstrap circuit is coupled between the second power supply terminal and the second bias output terminal.

8. The circuit of claim 7, wherein the minimum voltage selector comprises: A first switch is located between the first input terminal and the output terminal of the minimum voltage selector; and The second switch is located between the second input terminal and the output terminal of the minimum voltage selector.

9. The circuit of claim 7, wherein the first bootstrap circuit comprises: A diode coupled between the second power supply terminal and the first bias output terminal of the bias generator; and A capacitor coupled between the first bias output terminal and the first input terminal of the bias generator.

10. The circuit of claim 1, wherein the bias generator includes a charge transfer circuit coupled between the first bias output terminal and the second bias output terminal.

11. The circuit of claim 10, wherein the charge transfer circuit comprises a common-drain bidirectional switch, the common-drain bidirectional switch comprising a third transistor having a third gate and a third source, and a fourth transistor having a fourth gate and a fourth source.

12. The circuit of claim 11, wherein the bias generator comprises: A third driver has a third bias terminal, a third reference terminal, and a third driver output terminal. The third reference terminal is coupled to the first input terminal, the third bias terminal is coupled to the first bias output terminal, and the third driver output terminal is coupled to the third gate of the third transistor through a first capacitor. A fourth driver has a fourth bias terminal, a fourth reference terminal and a fourth driver output terminal, the fourth reference terminal being coupled to the second input terminal, the fourth bias terminal being coupled to the second bias output terminal, and the fourth driver output terminal being coupled to the fourth gate of the fourth transistor through a capacitor.

13. The circuit of claim 10, wherein the bias generator comprises: A first capacitor or a first voltage source is coupled between the first input terminal and the first bias output terminal; A first startup circuit is coupled between the first bias output terminal and the second bias output terminal; A second capacitor or a second voltage source is coupled between the second input terminal and the second bias output terminal; and The second startup circuit is coupled between the second bias output terminal and the first bias output terminal.

14. The circuit of claim 13, wherein the first startup circuit comprises: A common-drain bidirectional switch having a first switch terminal and a second switch terminal, wherein the first switch terminal is coupled to the first bias output terminal; and A source follower coupled between the second switching terminal and the second bias output terminal of the common drain bidirectional switch.

15. The circuit of claim 14, wherein the common-drain bidirectional switch comprises an enhancement-mode transistor and a depletion-mode transistor, the depletion-mode transistor having a gate terminal coupled to the second input terminal of the bias generator.

16. The circuit of claim 10, wherein the bias generator comprises: A voltage source comprising a positive terminal and a negative terminal, wherein the negative terminal is coupled to the first input terminal; A first capacitor is coupled between the first input terminal and the first bias output terminal; A first source follower is coupled between the positive terminal of the voltage source and the first bias output terminal; A second capacitor is coupled between the second input terminal and the second bias output terminal; A common-drain bidirectional switch includes a first switch terminal and a second switch terminal, the first switch terminal being coupled to the positive terminal of the voltage source; and The second source follower is coupled between the second switch terminal and the second bias output terminal.

17. The circuit according to claim 10, wherein: The bias generator includes: A first capacitor or a first voltage source is coupled between the first input terminal and the first bias output terminal; and A second capacitor or a second voltage source is coupled between the second input terminal and the second bias output terminal; and The charge transfer circuit includes: A first bidirectional switch and a first source follower are coupled between the first bias output terminal and the second bias output terminal. The first bidirectional switch is coupled to the first bias output terminal, and the first source follower is coupled to the second bias output terminal. and The second bidirectional switch and the second source follower are coupled between the first bias output terminal and the second bias output terminal. The second bidirectional switch is coupled to the second bias output terminal, and the second source follower is coupled to the first bias output terminal.

18. The circuit according to claim 17, wherein: The first bidirectional switch includes an enhancement transistor and a depletion transistor; The enhancement transistor includes a first gate terminal coupled to the output of the first driver via a third capacitor; and The depletion-type transistor includes a second gate terminal coupled to the second input terminal of the bias generator.

19. The circuit according to claim 10, wherein: The bias generator includes: A voltage source, coupled between the first input terminal and the first bias output terminal; and A first capacitor is coupled between the second input terminal and the second bias output terminal; and The charge transfer circuit includes a common-drain bidirectional switch and a source follower coupled between the first bias output terminal and the second bias output terminal. The common-drain bidirectional switch is coupled to the first bias output terminal, and the source follower is coupled to the second bias output terminal.

20. The circuit according to claim 19, wherein: The charge transfer circuit includes a third driver, which has a third bias terminal, a third reference terminal, and a third driver output terminal. The third bias terminal is coupled to the first bias output terminal, and the third reference terminal is coupled to the first input terminal. The common-drain bidirectional switch includes an enhancement-mode transistor and a depletion-mode transistor. The enhancement-mode transistor has a first gate terminal coupled to the output of the third driver via a second capacitor, and the depletion-mode transistor has a second gate terminal coupled to the second input.

21. A circuit comprising: A pair of transistors having a common drain, a first source, a second source, a first gate, and a second gate; A first driver has a first bias terminal, a first reference terminal, a first driver input terminal and a first driver output terminal, wherein the first reference terminal is coupled to the first source and the first driver output terminal is coupled to the first gate. The second driver has a second bias terminal, a second reference terminal, a second driver input terminal and a second driver output terminal, wherein the second reference terminal is coupled to the second source and the second driver output terminal is coupled to the second gate. and A bias generator has a first input terminal, a second input terminal, a first bias output terminal, and a second bias output terminal, wherein the first input terminal is coupled to a first source terminal, the second input terminal is coupled to a second source terminal, the first bias output terminal is coupled to a first bias terminal, and the second bias output terminal is coupled to a second bias terminal, wherein the bias generator is configured to generate a first bias voltage at the first bias output terminal and a second bias voltage at the second bias output terminal based on a power supply voltage.

22. A circuit comprising: First input port; First output port; Second output port; A first bidirectional switch is coupled between the first input port and the first output port. The first bidirectional switch includes a first switch driver, a second switch driver, and a first bias generator. The first bias generator is configured to generate a first bias voltage for the first switch driver and a second bias voltage for the second switch driver based on a first power supply voltage. and A second bidirectional switch is coupled between the first input port and the second output port. The second bidirectional switch includes a third switch driver, a fourth switch driver, and a second bias generator. The second bias generator is configured to generate a third bias voltage for the third switch driver and a fourth bias voltage for the fourth switch driver based on a second power supply voltage.

23. The circuit of claim 22, further comprising: Second input port; A third bidirectional switch is coupled between the second input port and the first output port. The third bidirectional switch includes a fifth switch driver, a sixth switch driver, and a third bias generator. The third bias generator is configured to generate a fifth bias voltage for the fifth switch driver and a sixth bias voltage for the sixth switch driver based on the first power supply voltage. and A fourth bidirectional switch is coupled between the second input port and the second output port. The fourth bidirectional switch includes a seventh switch driver, an eighth switch driver, and a fourth bias generator. The fourth bias generator is configured to generate a seventh bias voltage for the seventh switch driver and an eighth bias voltage for the eighth switch driver based on the second power supply voltage.

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