Cascade-based switching device with voltage clamp circuit

Abstract

A switching device includes: a first power transistor die including a normally on power transistor; a second power transistor die including a normally-off power transistor having: a drain electrically connected to a source of the normally-on power transistor to form a cascade device; and a capacitor electrically connected between the gate of the normally-on power transistor and the source of the normally-off power transistor. The two power transistors have at most half the voltage of the maximum rated drain-to-source voltage of a switching device. The second power transistor die further includes a voltage clamp circuit having: a normally-off clamp transistor having a drain electrically connected to the gate of the normally-on power transistor; and a source electrically connected to the source of the normally off power transistor; and diode (s) between the drain and gate of the normally off clamped transistor. Additional switching device embodiments are described.

Description

Background Art

[0001] A high breakdown voltage (e.g., greater than 800V) switching device can be realized by connecting a lower rated normally-off power transistor (e.g., 650V or less) and a lower rated normally-on power transistor (e.g., 650V or less) in a cascade configuration. However, the midpoint voltage at the node between the normally-off power transistor and the normally-on power transistor drifts under static DC blocking conditions (i.e., when blocking a constant voltage). The drifting midpoint voltage under static DC blocking conditions eventually causes the normally-on power transistor to turn on, which transfers the entire blocking voltage (e.g., 800V or more) of the switching device to the normally-off power transistor that is not rated for such a high voltage. Therefore, the normally-off power transistor may be damaged or destroyed.

[0002] Therefore, a need exists for improved cascode-based switching devices. Summary of the invention

[0003] According to an embodiment of the switching device, the switching device includes: a first power transistor die, which includes a normally-on power transistor, the normally-on power transistor having a voltage of at most half of the maximum rated drain-to-source voltage of the switching device; a second power transistor die, which includes a normally-off power transistor, the normally-off power transistor having a voltage of at most half of the maximum rated drain-to-source voltage of the switching device, wherein the drain of the normally-off power transistor is electrically connected to the source of the normally-on power transistor to form a cascade device; and a first capacitor, which is electrically connected between the gate of the normally-on power transistor and the source of the normally-off power transistor, wherein the second power transistor die also includes a voltage clamping circuit, the voltage clamping circuit including: a normally-off clamping transistor, the normally-off clamping transistor having: a drain, which is electrically connected to the gate of the normally-on power transistor; and a source, which is electrically connected to the source of the normally-off power transistor; and one or more diodes between the drain and the gate of the normally-off clamping transistor.

[0004] According to another embodiment of the switching device, the switching device includes: a first power transistor die, which includes a first bidirectional power switch, the first bidirectional power switch includes a first source, a second source, a normally closed gate and a normally open gate; a second power transistor die, which includes a second bidirectional power switch, the second bidirectional power switch includes: a first source, which is electrically connected to the second source of the first bidirectional power switch to form a cascade device; a second source; a normally closed gate; and a normally open gate; a first capacitor, which is electrically connected between the normally open gate of the second bidirectional power switch and the first source of the first bidirectional power switch; and a second capacitor, which is electrically connected between the normally open gate of the first bidirectional power switch and the second source of the second bidirectional power switch, wherein the first power transistor die also includes a first voltage clamping circuit, the first voltage clamping circuit The circuit includes: a first bidirectional clamp switch, the first bidirectional clamp switch having: a first gate; a second gate; a first source, which is electrically connected to the first source of the first bidirectional power switch; and a second source, which is electrically connected to the normally open gate of the second bidirectional power switch; and one or more diodes between the first gate and the second source of the first bidirectional clamp switch, wherein the second power transistor die also includes a second voltage clamp circuit, the second voltage clamp circuit includes: a second bidirectional clamp switch, the second bidirectional clamp switch having: a first gate; a second gate; a first source, which is electrically connected to the normally open gate of the first bidirectional power switch; and a second source, which is electrically connected to the second source of the second bidirectional power switch; and one or more diodes between the second gate and the first source of the second bidirectional clamp switch.

[0005] According to another embodiment of the switching device, the switching device includes: a first normally closed switch; a second normally closed switch; a first bidirectional power switch, which includes: a first source, which is electrically connected to the drain of the first normally closed switch; a second source; a first normally open gate, which is electrically connected to the source of the first normally closed switch; and a second normally open gate; a second bidirectional power switch, which includes: a first source, which is electrically connected to the second source of the first bidirectional power switch to form a cascade device; a second source, which is electrically connected to the drain of the second normally closed switch; a first normally open gate; and a second normally open gate, which are electrically connected to the source of the second normally closed switch; a first capacitor, which is electrically connected between the source of the first normally closed switch and the first normally open gate of the second bidirectional power switch; a second capacitor, which is electrically connected to the second normally open gate of the first bidirectional power switch a first voltage clamping circuit, comprising: a first bidirectional clamping switch, the first bidirectional clamping switch having: a first gate; a second gate; a first source, which is electrically connected to the source of the first normally-off switch; and a second source, which is electrically connected to the first normally-open gate of the second bidirectional power switch; and one or more diodes between the first gate and the second source of the first bidirectional clamping switch; and a second voltage clamping circuit, comprising: a second bidirectional clamping switch, the second bidirectional clamping switch having: a first gate; a second gate; a first source, which is electrically connected to the second normally-open gate of the first bidirectional power switch; and a second source, which is electrically connected to the source of the second normally-off switch; and one or more diodes between the second gate and the first source of the second bidirectional clamping switch.

[0006] Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The elements in the drawings are not necessarily to scale with respect to each other. The same reference numerals designate corresponding similar parts. The features of the various illustrated embodiments may be combined unless they exclude each other. The embodiments are depicted in the drawings and are detailed in the subsequent description.

[0008] Figure 1 A circuit schematic diagram of an embodiment of a unidirectional cascade switch device is illustrated.

[0009] Figure 2 and Figure 3 Several waveforms associated with the operation of a unidirectional cascade switching device are illustrated.

[0010] Figure 4 FIG. 1 is a circuit diagram of another embodiment of a unidirectional cascade switch device.

[0011] Figure 5 A circuit schematic diagram of an embodiment of a bidirectional cascade switch device based on a pair of asymmetric bidirectional switches is illustrated.

[0012] Figure 6 FIG. 1 is a circuit diagram of another embodiment of a bidirectional cascade switch device.

[0013] Figure 7 A circuit schematic diagram of an embodiment of a bidirectional cascade switch device based on a symmetric bidirectional power switch stacked between low voltage MOS switch devices in a cascade configuration is illustrated. DETAILED DESCRIPTION

[0014] The embodiments described herein provide a switching device implemented using discrete and / or bidirectional switching devices, which are arranged in a cascade configuration and have a lower breakdown voltage than the switching device, while maintaining the same number of active gates as a single high voltage device and utilizing the entire device in terms of voltage blocking and current conduction. For example, in the case of a 1.2kV rated switching device, the discrete and / or bidirectional switching device used to implement the switching device can have a breakdown voltage of 650V. However, the embodiments described herein can be applied to voltage levels other than 650V, and the resulting switching device can have a blocking voltage less than or greater than 1.2kV. For example, the switching device disclosed herein can have a breakdown voltage of at least 800V, and depending on the number of devices arranged in a cascade configuration, the switching device disclosed herein can be implemented using a discrete and / or bidirectional switching device having a breakdown voltage of up to half of the breakdown voltage of the switching device. In each case, the switching device includes a voltage clamping circuit that stabilizes the midpoint voltage of the cascade device under static DC blocking conditions.

[0015] Described next with reference to the figures are exemplary embodiments of a switching device.

[0016] Figure 1 An embodiment of a switching device 100 is illustrated. According to the embodiment, the switching device 100 is a unidirectional cascaded discrete device based on a first power transistor die (chip) 102 including a normally-on (i.e., depletion-mode) power transistor Q1 and a second power transistor die 104 including a normally-off (i.e., enhancement-mode) power transistor Q2. Both the normally-on power transistor Q1 and the normally-off power transistor Q2 have a voltage at most half the maximum rated drain-to-source (D-to-S) voltage of the switching device 100.

[0017] For the normally-on power transistor Q1, when no voltage is applied to the gate terminal G1 of the normally-on power transistor Q1, there is a current conduction channel between the drain terminal D1 and the source terminal S1 of the normally-on power transistor Q1. For the normally-off power transistor Q2, when no appropriate voltage is applied to the gate terminal G2 of the normally-off power transistor Q2, there is no current conduction channel between the drain terminal D2 and the source terminal S2 of the normally-off power transistor Q2.

[0018] In one embodiment, the power transistor dies 102, 104 are corresponding GaN dies, the normally-on power transistor Q1 is a normally-on GaN transistor, the normally-off power transistor Q2 is a normally-off GaN transistor, and the maximum rated drain-to-source voltage of the switching device 100 is 800V or higher, for example 1.2kV or higher. In GaN technology, the polarization difference between the GaN channel layer and the AlGaN barrier layer produces a 2-dimensional (2D) "sheet" with no compensating charge. The 2D charge sheet is typically positive and causes the formation of a 2D electron gas even in the absence of doping. Therefore, GaN devices tend to be normally-on devices unless additional device engineering techniques are applied, such as utilizing acceptor doping barriers, gate engineering, etc., to make the device normally-off.

[0019] The drain D2 of the normally-off power transistor Q2 is electrically connected to the source S1 of the normally-on power transistor Q1 to form a cascade device. According to this configuration, the drain D1 of the normally-on power transistor Q1 forms the drain D of the cascade switching device 100, and the source S2 of the normally-off power transistor Q2 forms the source S of the cascade switching device 100. The cascade switching device 100 has a single actively controlled (driven) gate G formed by the gate G2 of the normally-off power transistor Q2.

[0020] In order to maximize the use of these two power transistors Q1, Q2, Figure 1 The switching device 100 in also includes a voltage blocking device 106, which is electrically connected between the gate G1 of the normally-on power transistor Q1 and the source S2 of the normally-off power transistor Q2. When the cascade device formed by the power transistors Q1 and Q2 is disconnected, the voltage blocking device 106 blocks a portion of the drain-to-source voltage "VDS" across the switching device 100. In one embodiment, the voltage blocking device 106 is a capacitor C1, which has: a first terminal 108, which is electrically connected to the gate G1 of the normally-on power transistor Q1; and a second terminal 110, which is electrically connected to the source S2 of the normally-off power transistor Q2. For example, if the power transistors Q1 and Q2 are rated for 650V, the voltage blocking capacitor C1 can be in the pF range.

[0021] Figure 1The switching device 100 in also includes a voltage clamp circuit 112, which is included in the second power transistor die 104. The voltage clamp circuit 112 stabilizes the midpoint voltage "VM" of the cascode device under static DC blocking conditions. The midpoint voltage VM of the cascode device is the voltage at the node between the normally-off power transistor Q2 and the normally-on power transistor Q1. Without the voltage clamp circuit 112 or with a poor voltage clamp circuit including only a diode Dcl, the midpoint voltage VM will drift under static DC blocking conditions, i.e., when the switching device 100 blocks a constant voltage.

[0022] exist Figure 1 The voltage clamp circuit 112 shown in FIG. 1 includes a normally-off clamp transistor Q3, such as a normally-off GaN transistor, having a drain D3 electrically connected to the gate G1 of the normally-on power transistor Q1 and a source S3 electrically connected to the source S2 of the normally-off power transistor Q2. As used herein, the term "electrically connected" means a connection directly or through one or more intermediate electrical devices (such as resistors, diodes, capacitors, inductors, transistors, etc.). For example, in Figure 1 , the drain D3 of the normally-off clamp transistor Q3 is shown as being directly connected to the gate G1 of the normally-on power transistor Q1 without any intervening electrical devices, while the source S3 of the normally-off clamp transistor Q3 is shown as being connected to the source S2 of the normally-off power transistor Q2 through the voltage clamp device Z1.

[0023] Figure 1 The voltage clamp circuit 112 in also includes one or more diodes Dc1, such as (one or more) ESD (electrostatic discharge) diodes between the drain D3 and the gate G3 of the normally-off clamp transistor Q3.

[0024] exist Figure 1 , the voltage clamp circuit 112 further includes a pull-down device 114 that prevents the normally-off clamp transistor Q3 from turning on during dynamic switching of the switch device 100. In one embodiment, the pull-down device 114 includes a normally-on pull-down transistor Q4 (such as a normally-on GaN transistor) and a voltage clamp Z1. The normally-on pull-down transistor Q4 of the pull-down device 114 has a drain D4 electrically connected to a gate G3 of the normally-off clamp transistor Q3; a source S4 electrically connected to a source S3 of the normally-off clamp transistor Q3; and a gate G4 electrically connected to a source S2 of the normally-off power transistor Q2.

[0025] The voltage clamp Z1 of the pull-down device 114 is electrically connected between the source S4 of the normally-on pull-down transistor Q4 and the source S2 of the normally-off power transistor Q2. The voltage clamp Z1 is illustrated as a Zener diode because the voltage clamp Z1 behaves like a Zener diode, but can be implemented using a string of one or more ESD diodes. The pull-down device 114 can also include a resistor R1 electrically connected between the gate G3 and the source S3 of the normally-off clamp transistor Q3.

[0026] As in Figure 1 As shown in FIG. 1 , the drain D2 of the normally-off power transistor Q2 and the drain D3 of the normally-off clamping transistor Q3 are not the same node. In addition, the clamping voltage "V_clamp" of the clamping circuit 112 can be controlled by the number of diodes Dcl in the chain between the gate G3 and the drain D3 of the normally-off clamping transistor Q3. The simulation shows that under 800V DC blocking conditions, the midpoint voltage VM of the cascaded device is stable within seconds. For example, in the case of 140 ESD diodes Dcl in the chain between the gate G3 and the drain D3 of the normally-off clamping transistor Q3, the simulation shows that the midpoint voltage VM stabilizes at 444V after 1 second. In the case of 130 ESD diodes Dcl in the chain between the gate G3 and the drain D3 of the normally-off clamping transistor Q3, the midpoint voltage VM stabilizes at 414V after 1 second. In the case of 120 ESD diodes Dcl in the chain between the gate G3 and the drain D3 of the normally-off clamping transistor Q3, the midpoint VM stabilizes at 383V after 1 second. In each case, and once stabilized, the midpoint voltage VM of the cascode device no longer drifts due to leakage. Further, for this simulation, the power dissipation of the voltage clamp circuit 112 is only 4.4 μW at 800 V DC blocking.

[0027] Figure 2 and Figure 3 Several waveforms associated with the operation of the switching device 100 including the voltage clamp circuit 112 are illustrated. Figure 2 The upper portion of FIG. 1 plots the gate voltage of the normally-on power transistor Q1 (' VGH1 ') with the voltage clamp circuit 112 and the gate voltage of the normally-on power transistor Q1 (' VGH2 ') with the suboptimal voltage clamp circuit including only the diode Dcl. Figure 2 The lower portion of FIG. 1 plots the power dissipation of the voltage clamp circuit 112 ('P_clamp1') and the power dissipation of a suboptimal voltage clamp circuit ('P_clamp2'). Figure 3Plotted are the drain to source voltage and midpoint voltage ('VDS1', 'VM1') with the voltage clamp circuit 112 and the drain to source voltage and midpoint voltage ('VDS2', 'VM2') with a suboptimal version of the voltage clamp circuit 112. The VDS and VM voltages are simulated during hard switching from 800V.

[0028] In the case of a poor voltage clamp circuit including only diode Dcl, the Miller capacitance of the normally-off clamp transistor Q3 is neglected and the normally-off clamp transistor Q3 will experience a pseudo turn-on during most dynamic switching events. Such pseudo turn-on events will create additional losses and cause VM drift, which is detected by comparing Figure 2 VGH1 waveform and VGH2 waveform and comparison Figure 3 For the case of a poor voltage clamp circuit including only diode Dcl, both the gate voltage VGH2 and the midpoint voltage VM2 continue to decrease with each switching cycle.

[0029] Furthermore, the power consumption P_clamp2 for the case of a suboptimal voltage clamp circuit including only a diode Dcl increases significantly with each switching cycle, while Figure 1 The power consumption P_clamp1 of the voltage clamp circuit 112 shown in FIG. 1 is negligible in comparison. Further simulations have shown that during hard switching of about 3 to 4 A for Figure 1 The power consumption P_clamp1 of the voltage clamp circuit 112 shown in FIG. 1 is 4 nJ per switching cycle (~0.4 mW at 100 kHz). For soft switching, Figure 1 The power consumption P_clamp1 of the voltage clamp circuit 112 shown in FIG. 1 is 2 nJ per switching cycle (at 500 kHz, ˜1 mW).

[0030] Figure 1 The switching device 100 in further includes an overvoltage protection circuit 116, which protects the gate G1 of the normally-on power transistor Q1 from an overvoltage condition in the negative direction when the normally-off power transistor Q2 is turned off. When the normally-off power transistor Q2 is turned off, the overvoltage protection circuit 116 turns off the normally-on power transistor Q1 so that the cascade device formed by the power transistors Q1 and Q2 is actively controlled only by the gate G2 of the normally-off power transistor Q2. Therefore, only the normally-off gate G2 of the normally-off power transistor Q2 is actively controlled (driven) to control the cascade structure, and synchronous driving of the normally-open gate G1 of the normally-on power transistor Q1 is not required.

[0031] In one embodiment, the overvoltage protection circuit 116 includes one or more diodes “DOVP”, which are connected in series between the gate G1 of the normally-on power transistor Q1 and the source S1 of the normally-on power transistor Q1. The number of diodes DOVP depends on the total forward voltage of the overvoltage protection circuit 116, which should be greater than the negative threshold voltage of the normally-on power transistor Q1 in an absolute sense to turn off the normally-on power transistor Q1. Therefore, the overvoltage protection circuit 116 may include a single diode DOVP, which has: an anode, which is electrically connected to the source S1 of the normally-on power transistor Q1; and a cathode, which is electrically connected to the gate G1 of the normally-on power transistor Q1. In the case of multiple diodes DOVP connected in series, for example, as in Figure 1 As shown in FIG. 1 , the anode of the first diode DOVP in the series chain is electrically connected to the source S1 of the normally-on power transistor Q1, and the cathode of the last diode DOVP in the series chain is electrically connected to the gate G1 of the normally-on power transistor Q1. For example, the diode(s) DOVP, such as the ESD structure(s), may be monolithically integrated in the same die 102 as the normally-on power transistor Q1. The diode(s) DOVP of the overvoltage protection circuit 116 also sets the gate-to-source voltage of the normally-on power transistor Q1 during shutdown.

[0032] In one embodiment, the overvoltage protection circuit 116 may include a capacitor C2 connected in parallel with one or more diodes DOVP of the overvoltage protection circuit 116. Figure 1 , capacitor C2 of overvoltage protection circuit 116 is monolithically integrated in the same die 102 as normally-on power transistor Q1 , for example, as a metal-insulator-metal capacitor structure. Figure 1 Also shown is a voltage blocking capacitor C1 monolithically integrated in the same die 104 as the normally-off power transistor Q2, for example as a metal-insulator-metal capacitor structure.

[0033] Figure 4 Another embodiment of a unidirectional cascade switch device 100 is shown. Figure 4 The embodiment illustrated in Figure 1 The embodiment shown in FIG. Figure 4 In the embodiment, the capacitor C2 and the voltage blocking capacitor C1 of the overvoltage protection circuit 116 are discrete components. That is, the capacitor C2 and the voltage blocking capacitor C1 of the overvoltage protection circuit 116 are external to the power transistor dies 102 and 104. In this case, the capacitor C2 and the voltage blocking capacitor C1 of the overvoltage protection circuit 116 can be co-packaged with the power transistor dies 102 and 104. Figure 1 and Figure 4The switch device embodiment illustrated in can be extended to three or more cascaded power transistors to produce a higher total rated voltage for the switch device 100, wherein the breakdown voltage X_Q of each power transistor forming the cascaded switch device is given by X_Q=X_SW / N, where X_SW is the breakdown voltage of the entire cascaded switch device and N is the number of cascaded power transistors. Figure 1 and Figure 4 For a single normally-on transistor cascaded with a normally-off transistor as shown in , N=2 and X_Q=1 / 2*X_SW. For two normally-on transistors cascaded with a normally-off transistor, N=3 and X_Q=1 / 3*X_SW and so on.

[0034] Described next is an embodiment of a bidirectional cascade switch device based on a symmetrical and / or asymmetrical bidirectional switch. The solid-state bidirectional switch has: a first source terminal; a second source terminal; a compound semiconductor substrate, such as, for example, a GaN substrate; a common drift region in the compound semiconductor substrate and connected in series between the two source terminals; a first gate; and a second gate. In the case of a symmetrical bidirectional switch, the two gates are normally open gates. In the case of an asymmetrical bidirectional switch, one gate is a normally open gate (i.e., a depletion type) and the other gate is a normally closed gate (i.e., an enhancement type). For a normally open gate, there is a current conduction channel near the gate in the absence of any voltage applied to the gate. For a normally closed gate, there is no current conduction channel near the gate in the absence of a suitable voltage applied to the gate.

[0035] Figure 5 An embodiment of a bidirectional cascade switch device 200 based on a pair of asymmetric bidirectional switches BDSA, BDSB is illustrated. The first asymmetric bidirectional switch BDSA includes a first source S1A, a second source S2A, a normally closed gate G1A, and a normally open gate G2A. The second asymmetric bidirectional switch BDSB includes: a first source S1B, which is electrically connected to the second source S2A of the first asymmetric bidirectional switch BDSA to form a cascade device; a second source S2B; a normally closed gate G2B; and a normally open gate G1B.

[0036] The asymmetric bidirectional switches BDSA, BDSB may be provided as discrete dies 202, 204. For example, a first asymmetric bidirectional switch BDSA may be included in a first GaN die 202 and have a voltage of at most half (1 / 2) of the maximum rated source-to-source (S2B to S1A) voltage of the bidirectional cascade switch device 200. A second asymmetric bidirectional switch BDSB may be included in a second GaN die 204 and have a voltage of at most half (1 / 2) of the maximum rated source-to-source voltage of the bidirectional cascade switch device 200. The maximum rated source-to-source voltage of the bidirectional cascade switch device 200 may be 800V or higher, for example 1.2 kV or higher. The asymmetric bidirectional switches BDSA, BDSB may alternatively be monolithically integrated in the same die. In either case, the common drift regions / compound semiconductor substrates of the asymmetric bidirectional switches BDSA, BDSB are electrically isolated from each other to ensure that each asymmetric bidirectional switch BDSA, BDSB can safely block its own individual voltage.

[0037] The bidirectional cascade switch device 200 further includes a first capacitor C1A, which is electrically connected between the normally open gate G1B of the second bidirectional power switch BDSB and the first source S1A of the first bidirectional power switch BDSA. The second capacitor C1B is electrically connected between the normally open gate G2A of the first bidirectional power switch BDSA and the second source S2B of the second bidirectional power switch BDSB.

[0038] The first power transistor die 202 further includes a first voltage clamp circuit 206, which includes a first bidirectional clamp switch BDSC and one or more diodes Dcl1. The first bidirectional clamp switch BDSC has: a first gate G1C; a second gate G2C; a first source S1C, which is electrically connected to a first source S1A of the first bidirectional power switch; and a second source S2C, which is electrically connected to a normally open gate G1B of a second bidirectional power switch BDSB. The one or more diodes Dcl1 of the first voltage clamp circuit 206 are electrically connected between the first gate G1C and the second source S2C of the first bidirectional clamp switch BDSC.

[0039] The second power transistor die 204 further includes a second voltage clamp circuit 208, which includes a second bidirectional clamp switch BDSD and one or more diodes Dcl2. The second bidirectional clamp switch has: a first gate G1D; a second gate G1D; a first source S1D, which is electrically connected to the normally open gate G2A of the first bidirectional power switch BDSA; and a second source S2D, which is electrically connected to the second source S2B of the second bidirectional power switch BDSB. The one or more diodes Dcl1 of the second voltage clamp circuit 208 are electrically connected between the second gate G2D and the first source S1D of the second bidirectional clamp switch BDSD.

[0040] The first voltage clamp circuit 206 may further include a first pull-down device 210 that prevents the first bidirectional clamp switch BDSC from turning on during dynamic switching of the switching device 200. The second voltage clamp circuit 208 may also include a second pull-down device 212 that prevents the second bidirectional clamp switch BDSD from turning on during dynamic switching of the switching device 200.

[0041] In one embodiment, the first pull-down device 210 includes a first normally-open pull-down transistor Q5 and a first voltage clamp ZA1. The first normally-open pull-down transistor Q5 has a drain D5 electrically connected to a first gate G1C of a first bidirectional clamp switch BDSC, a source S5 electrically connected to a first source S1C of the first bidirectional clamp switch BDSC, and a gate G5 electrically connected to a first source S1A of a first bidirectional power switch BDSA. The first voltage clamp ZA1 of the first pull-down device 210 is electrically connected between the source S5 of the first normally-open pull-down transistor Q5 and the first source S1A of the first bidirectional power switch BDSA.

[0042] The second pull-down device 212 may also include a second normally-open pull-down transistor Q6 and a second voltage clamp ZB1. The second normally-open pull-down transistor Q6 has a drain D6 electrically connected to a second gate S2D of the second bidirectional clamp switch BDSD; a source S6 electrically connected to a second source S2D of the second bidirectional clamp switch BDSD; and a gate G6 electrically connected to a second source S2B of the second bidirectional power switch BDSB. The second voltage clamp ZB1 of the second pull-down device 212 is electrically connected between the source S6 of the second normally-open pull-down transistor Q6 and the second source S2B of the second bidirectional power switch BDSB.

[0043] The first pull-down device 210 may further include a resistor RA1 electrically connected between the first gate G1C and the first source S1C of the first bidirectional clamp switch BDSC. The second pull-down device 212 may also include a resistor RB1 electrically connected between the second gate G2D and the second source S2D of the second bidirectional clamp switch BDSD.

[0044] Figure 5 The bidirectional cascade switch device 200 further includes a first overvoltage protection circuit 214 and a second overvoltage protection circuit 216. When the normally closed gate G2B of the second bidirectional power switch BDSB is turned off, the first overvoltage protection circuit 214 turns off the normally open gate G2A of the first bidirectional power switch BDSA, so that the normally open gate G2A of the first bidirectional power switch BDSA is passively controlled by the normally closed gate G2B of the second bidirectional power switch BDSB. When the normally closed gate G1A of the first bidirectional power switch BDSA is turned off, the second overvoltage protection circuit 216 similarly turns off the normally open gate G1B of the second bidirectional power switch BDSB, so that the normally open gate G1B of the second bidirectional power switch BDSB is passively controlled by the normally closed gate G1A of the first bidirectional power switch BDSA.

[0045] In one embodiment, the first overvoltage protection circuit 214 includes one or more diodes DOVPA, which are connected in series between the normally open gate G2A and the second source S2A of the first bidirectional power switch BDSA. The anode of the first diode in the one or more diodes DOVPA of the first overvoltage protection circuit 214 is electrically connected to the second source S2A of the first bidirectional power switch BDSA. The cathode of the last diode in the one or more diodes DOVPA of the first overvoltage protection circuit 214 is electrically connected to the normally open gate G2A of the first bidirectional power switch BDSA. The capacitor C2A can be connected in parallel with the one or more diodes DOVPA of the first overvoltage protection circuit 214.

[0046] The second overvoltage protection circuit 216 may similarly include one or more diodes DOPPB, which are connected in series between the normally open gate G1B and the first source S1B of the second bidirectional power switch BDSB. The anode of the first diode in the one or more diodes DOPPB of the second overvoltage protection circuit 216 is electrically connected to the first source S1B of the second bidirectional power switch BDSB. The cathode of the last diode in the one or more diodes DOPPB of the second overvoltage protection circuit 216 is electrically connected to the normally open gate G1B of the second bidirectional power switch BDSB. The capacitor C2B may be connected in parallel with the one or more diodes DOPPB of the second overvoltage protection circuit 216.

[0047] The first overvoltage protection circuit 214 may further include an additional diode DA1 having an anode electrically connected to the cathode of the last diode among the one or more diodes DOVPA of the first overvoltage protection circuit 214 and a cathode electrically connected to the anode of the first diode among the one or more diodes DOVPA of the first overvoltage protection circuit 214. The second overvoltage protection circuit 216 may similarly include an additional diode DB1 having an anode electrically connected to the cathode of the last diode among the one or more diodes DOPPB of the second overvoltage protection circuit 216 and a cathode electrically connected to the anode of the first diode among the one or more diodes DOPPB of the second overvoltage protection circuit 216.

[0048] exist Figure 5 In the embodiment, both the first gate G1C and the second gate G2C of the first bidirectional clamp switch BDSC are normally closed gates. Both the first gate G1D and the second gate G2D of the second bidirectional clamp switch BDSD are also normally closed gates.

[0049] Figure 6 Another embodiment of a bidirectional cascade switch device 200 is shown. Figure 6 The embodiment illustrated in Figure 5 The embodiment shown in FIG. Figure 6 , the first gate G1C of the first bidirectional clamp switch BDSC is a normally closed gate, and the second gate G2C of the first bidirectional clamp switch BDSC is a normally open gate. Similarly, the first gate G1D of the second bidirectional clamp switch BDSD is a normally open gate, and the second gate G2D of the second bidirectional clamp switch BDSD is a normally closed gate.

[0050] form Figure 5 and Figure 6 The bidirectional power switches BDSA, BDSB of the bidirectional cascade switch device 200 shown in FIG. 2 may be provided as discrete dies 202, 204. For example, each bidirectional power switch BDSA, BDSB may be included in a separate GaN die 202, 204 and have at most half (1 / 2) of the maximum rated source-to-source (S2B to S1A) voltage of the switch device 200. The maximum rated source-to-source (S2B to S1A) voltage of the switch device 200 may be 800V or higher, such as 1.8kV or higher.

[0051] Capacitors C1A, C1B, C2A, C2B and voltage clamp circuits 206, 208 are Figure 5 and Figure 62 are shown as being integrated in the corresponding power transistor dies 202 , 204 . However, the capacitors C1A, C1B, C2A, C2B may alternatively be external components co-packaged with the power transistor dies 202 , 204 .

[0052] Figure 5 and Figure 6 The two stacked asymmetric bidirectional power switches BDSA, BDSB in are used to block the entire (e.g., 800V or higher) source-to-source voltage of the bidirectional cascade switch device 200, wherein the two devices BDSA, BDSB are always 100% utilized. Further, only two active gates G1A, G2B are required to fully operate the bidirectional cascade switch device 200. The bidirectional cascade switch device approach can be further extended to provide higher blocking voltage capabilities, as described in more detail below.

[0053] More generally, the bidirectional cascade switch device method uses at least two bidirectional power switches electrically connected in a cascade configuration, wherein a first bidirectional power switch (eg, Figure 5 and Figure 6 BDSA in) and a second bidirectional power switch (eg, Figure 5 and Figure 6 The BDSB in each of the first and second bidirectional power switches has a normally open gate and a normally closed gate. Any remaining bidirectional power switches cascaded between the first and second bidirectional power switches have a first normally open gate and a second normally open gate. The bidirectional cascade switch device 200 is composed of the first bidirectional power switch (e.g., Figure 5 and Figure 6 The normally closed gate of the BDSA in Figure 5 and Figure 6 G1A in) and a second bidirectional power switch (eg, Figure 5 and Figure 6 The normally closed gate of the BDSB in Figure 5 and Figure 6 Each normally open gate of at least two bidirectional power switches (e.g., Figure 5 and Figure 6 G2A and G1B in the circuit are protected by an overvoltage protection circuit (e.g. Figure 5 and Figure 6 214 and 216 in the bidirectional power switch) are electrically connected to the source of another of the at least two bidirectional power switches, and the overvoltage protection circuit blocks the source-to-source (eg, Figure 5 and Figure 6 The voltage from S2B to S1A in the circuit.

[0054] Described below are embodiments of bidirectional cascade switch devices based on symmetrical bidirectional power switches and low voltage (eg, 20V) MOS devices.

[0055] Figure 7 An embodiment of a bidirectional cascade switch device 300 based on symmetrical bidirectional power switches BDSX, BDSY stacked between low voltage MOS switch devices LV1, LV2 in a cascade configuration is illustrated. The low voltage MOS switch devices LV1, LV2 are normally closed switches because the two low voltage MOS switch devices LV1, LV2 are enhancement mode devices. For example, Figure 7 The normally-off MOS switch devices LV1, LV2 in are referred to as “low voltage” because they have a lower breakdown voltage (e.g., 20V) than the symmetrical bidirectional power switches BDSX, BDSY, which may be 650V rated GaN devices.

[0056] At least two bidirectional power switches BDSX, BDSY are electrically connected in a cascade configuration between a first normally-off MOS switch device LV1 and a second normally-off MOS switch device LV2. Each bidirectional power switch BDSX, BDSY has a first normally-open gate G1X, G1Y and a second normally-open gate G2X, G2Y and is therefore considered symmetrical.

[0057] A first source S1X of the first bidirectional power switch BDSX is electrically connected to a drain DLV1 of the first normally-off MOS switch device LV1. A first normally-open gate G1X of the first bidirectional power switch BDSX is electrically connected to a source SLV1 of the first normally-off MOS switch device LV1.

[0058] The first source S1Y of the second bidirectional power switch BDSY is electrically connected to the second source S2X of the first bidirectional power switch BDSX to form a cascade device. The second source S2Y of the second bidirectional power switch BDSY is electrically connected to the drain DLV2 of the second normally-off MOS switch device LV2. The second normally-open gate S2Y of the second bidirectional power switch BDSY is electrically connected to the source SLV2 of the normally-off MOS switch device LV2.

[0059] The first capacitor C1A is electrically connected between the source SLV1 of the first normally-off MOS switch device LV1 and the first normally-open gate G1Y of the second bidirectional power switch BDSY. The second capacitor C1B is electrically connected between the second normally-open gate G2X of the first bidirectional power switch BDSX and the source SLV2 of the second normally-off MOS switch device LV2.

[0060] The first voltage clamp circuit 206, which can be monolithically integrated with the first bidirectional power switch BDSX, includes a first bidirectional clamp switch BDSC and one or more diodes Dcl1. The first bidirectional clamp switch BDSC has: a first gate G1C; a second gate G2C; a first source S1C, which is electrically connected to the source SLV1 of the first normally-off MOS switch device LV1; and a second source S2C, which is electrically connected to the first normally-open gate G1Y of the second bidirectional power switch BDSY. The one or more diodes Dcl1 of the first voltage clamp circuit 206 are electrically connected between the first gate G1C and the second source S2C of the first bidirectional clamp switch BDSC.

[0061] The second voltage clamping circuit 208, which can be monolithically integrated with the second bidirectional power switch BDSY, includes a second bidirectional clamping switch BDSD and one or more diodes Dcl2. The second bidirectional clamping switch BDSD has: a first gate G1D; a second gate G2D; a first source S1D, which is electrically connected to the second normally-open gate G2X of the first bidirectional power switch BDSX; and a second source S2D, which is electrically connected to the source SLV2 of the second normally-off MOS switch device LV2. The one or more diodes Dcl2 of the second voltage clamping circuit 208 are electrically connected between the second gate G2D and the first source S1D of the second bidirectional clamping switch BDSD.

[0062] The gates G1C, G2C of the first bidirectional clamp switch BDSC and the gates G1D, G2D of the second bidirectional clamp switch BDSD are both normally closed gates, for example, as described previously in this document. Figure 5 Therefore, in Figure 7 The first bidirectional clamp switch BDSC and the second bidirectional clamp switch BDSD shown in FIG. 1 are considered to be symmetrical. However, the first bidirectional clamp switch BDSC and the second bidirectional clamp switch BDSD may alternatively be asymmetrical. For example, the first gate G1C of the first bidirectional clamp switch BDSC and the second gate G2D of the second bidirectional clamp switch BDSD may be normally closed gates, while the second gate G2C of the first bidirectional clamp switch BDSC and the first gate G1D of the second bidirectional clamp switch BDSD may be normally open gates, for example, as previously described herein. Figure 6 Just as described.

[0063] As previously explained herein, the first voltage clamp circuit 206 may further include a first pull-down device 210 that prevents the first bidirectional clamp switch BDSC from turning on during dynamic switching of the switching device 300. The second voltage clamp circuit 208 may also further include a second pull-down device 212 that prevents the second bidirectional clamp switch BDSD from turning on during dynamic switching of the switching device 300.

[0064] In one embodiment, the first pull-down device 210 includes a first normally-open pull-down transistor Q5 and a first voltage clamp ZA1. The first normally-open pull-down transistor Q5 has a drain D5 electrically connected to a first gate G1C of a first bidirectional clamp switch BDSC; a source S5 electrically connected to a first source S1C of the first bidirectional clamp switch BDSC; and a gate G5 electrically connected to a source SLV1 of a first normally-off MOS switch device LV1. The first voltage clamp ZA1 of the first pull-down device 210 is electrically connected between the source S5 of the first normally-open pull-down transistor Q5 and the source SLV1 of the first normally-off MOS switch device LV1. The first pull-down device may further include a resistor RA1 electrically connected between the first gate G1C and the first source S1C of the first bidirectional clamp switch BDSC.

[0065] The second pull-down device 212 may similarly include a second normally-open pull-down transistor Q6 and a second voltage clamp ZB1. The second normally-open pull-down transistor Q6 has a drain D6 electrically connected to a second gate G2D of a second bidirectional clamp switch BDSD; a source S6 electrically connected to a second source S2D of a second bidirectional clamp switch BDSD; and a gate G6 electrically connected to a source SLV2 of a second normally-off MOS switch device LV2. The second voltage clamp ZB1 of the second pull-down device 212 is electrically connected between the source S6 of the second normally-open pull-down transistor Q6 and the source SLV2 of the second normally-off MOS switch device LV2. The second pull-down device 212 may also include a resistor RB1 electrically connected between the second gate G2D and the second source S2D of the second bidirectional clamp switch BDSD.

[0066] Figure 7 The bidirectional cascade switch device 300 may also include: the first overvoltage protection circuit 214 previously described in this document, which is used for the two normally open gates G1X and G2X of the first bidirectional power switch BDSX; and the second overvoltage protection circuit 216, which is used for the two normally open gates G1Y and G2Y of the second bidirectional power switch BDSY.

[0067] Compared with stacked asymmetric bidirectional power switches BDSA and BDSB Figure 5 and Figure 6 The embodiments in the examples are different. Figure 7 The illustrated embodiment uses stacked symmetrical bidirectional power switches BDSX, BDSY, both of which have a pair of normally open gates G1X / G2X, G1Y / G2Y. Figure 7In the embodiment, the first source S1X of the first bidirectional power switch BDSX is electrically connected to the first normally-off MOS switch device LV1 to form a cascode device separated from the main cascode, so as to enable the normally-off function. Similarly, the second source S2Y of the second bidirectional power switch BDSY is electrically connected to the second normally-off MOS switch device LV2, so as to enable the normally-off function.

[0068] In addition Figure 5 and Figure 6 The difference from the embodiment shown in FIG. 1 is that the sources of the two voltage clamping circuits 206 and 208 are electrically connected to the sources SLV1 and SLV2 of the corresponding normally-off MOS switch devices LV1 and LV2, and are not directly coupled to any terminals of the symmetrical bidirectional power switches BDSX and BDSY included in the same die, wherein the die terminals are connected by Figure 1 and Figures 4 to 7 Depending on the semiconductor technology used to manufacture the bidirectional power switches BDSX, BDSY and the normally-off MOS switch devices LV1, LV2, the normally-off MOS switch devices LV1, LV2 may or may not be integrated in the same die as the corresponding bidirectional power switches BDSX, BDSY.

[0069] Figure 7 A first normally-off MOS switch device LV1 implemented in a different die from the first bidirectional power switch BDSX and a second normally-off MOS switch device LV2 implemented in a different die from the second bidirectional power switch BDSY are shown. However, the first normally-off MOS switch device LV1 may alternatively be integrated in the same (first) die with the first bidirectional power switch BDSX, and the second normally-off MOS switch device LV2 may be integrated in the same (second) die with the second bidirectional power switch BDSY.

[0070] Although the present disclosure is not so limited, the following numbered examples demonstrate one or more aspects of the present disclosure.

[0071] Example 1. A switching device, comprising: a first power transistor die, comprising a normally-on power transistor, the normally-on power transistor having a voltage of at most half of a maximum rated drain-to-source voltage of the switching device; a second power transistor die, comprising a normally-off power transistor, the normally-off power transistor having a voltage of at most half of a maximum rated drain-to-source voltage of the switching device, wherein the drain of the normally-off power transistor is electrically connected to the source of the normally-on power transistor to form a cascade device; and a first capacitor electrically connected between a gate of the normally-on power transistor and a source of the normally-off power transistor, wherein the second power transistor die further comprises a voltage clamping circuit, the voltage clamping circuit comprising: a normally-off clamping transistor, the normally-off clamping transistor having: a drain electrically connected to the gate of the normally-on power transistor; and a source electrically connected to the source of the normally-off power transistor; and one or more diodes between the drain and the gate of the normally-off clamping transistor.

[0072] Example 2. The switching device of Example 1, wherein the normally-on power transistor is a normally-on GaN transistor, wherein the normally-off power transistor is a normally-off GaN transistor, and wherein the maximum rated drain-to-source voltage of the switching device is 800 V or higher.

[0073] Example 3. The switching device of Example 1 or 2, wherein the voltage clamp circuit further comprises a pull-down device configured to prevent the normally-off clamp transistor from turning on during dynamic switching of the switching device.

[0074] Example 4. The switching device of Example 3, wherein the pull-down device comprises: a normally-on pull-down transistor having: a drain electrically connected to a gate of a normally-off clamp transistor; a source electrically connected to a source of the normally-off clamp transistor; and a gate electrically connected to a source of a normally-off power transistor; and a voltage clamp between the source of the normally-on pull-down transistor and the source of the normally-off power transistor.

[0075] Example 5. The switch device of Example 4, wherein the pull-down device further comprises: a resistor electrically connected between the gate and the source of the normally-off clamp transistor.

[0076] Example 6. The switching device of any one of Examples 1 to 5 further comprises an overvoltage protection circuit configured to: when the normally-off power transistor is turned off, turn off the normally-on power transistor so that the cascode device is actively controlled only by the gate of the normally-off power transistor.

[0077] Example 7. A switching device as described in Example 6, wherein the overvoltage protection circuit includes one or more diodes, the one or more diodes are connected in series between the gate and the source of the normally-on power transistor, wherein the anode of the first diode of the one or more diodes of the overvoltage protection circuit is electrically connected to the source of the normally-on power transistor, and wherein the cathode of the last diode of the one or more diodes of the overvoltage protection circuit is electrically connected to the gate of the normally-on power transistor.

[0078] Example 8. The switching device of Example 7 further includes: a capacitor connected in parallel with the one or more diodes of the overvoltage protection circuit.

[0079] Example 9. A switching device, comprising: a first power transistor die, comprising a first bidirectional power switch, the first bidirectional power switch comprising a first source, a second source, a normally closed gate, and a normally open gate; a second power transistor die, comprising a second bidirectional power switch, the second bidirectional power switch comprising: a first source, which is electrically connected to the second source of the first bidirectional power switch to form a cascade device; a second source; a normally closed gate; and a normally open gate; a first capacitor, which is electrically connected between the normally open gate of the second bidirectional power switch and the first source of the first bidirectional power switch; and a second capacitor, which is electrically connected between the normally open gate of the first bidirectional power switch and the second source of the second bidirectional power switch, wherein the first power transistor die also comprises a first voltage clamping circuit, the first voltage clamping circuit comprising : A first bidirectional clamp switch, the first bidirectional clamp switch having: a first gate; a second gate; a first source, which is electrically connected to the first source of the first bidirectional power switch; and a second source, which is electrically connected to the normally open gate of the second bidirectional power switch; and one or more diodes between the first gate and the second source of the first bidirectional clamp switch, wherein the second power transistor die also includes a second voltage clamp circuit, the second voltage clamp circuit includes: a second bidirectional clamp switch, the second bidirectional clamp switch having: a first gate; a second gate; a first source, which is electrically connected to the normally open gate of the first bidirectional power switch; and a second source, which is electrically connected to the second source of the second bidirectional power switch; and one or more diodes between the second gate and the first source of the second bidirectional clamp switch.

[0080] Example 10. The switching device of Example 9, wherein the first power transistor die is a first GaN die and the first bidirectional power switch has a voltage at most half of the maximum rated source-to-source voltage of the switching device, wherein the second power transistor die is a second GaN die and the second bidirectional power switch has a voltage at most half of the maximum rated source-to-source voltage of the switching device, and wherein the maximum rated source-to-source voltage of the switching device is 800 V or higher.

[0081] Example 11. A switching device as described in Example 9 or 10, wherein the first voltage clamp circuit further includes a first pull-down device configured to prevent the first bidirectional clamp switch from being turned on during dynamic switching of the switching device, and wherein the second voltage clamp circuit further includes a second pull-down device configured to prevent the second bidirectional clamp switch from being turned on during dynamic switching of the switching device.

[0082] Example 12. A switching device as described in Example 11, wherein the first pull-down device includes: a first normally-open pull-down transistor having: a drain electrically connected to a first gate of a first bidirectional clamp switch; a source electrically connected to a first source of the first bidirectional clamp switch; and a gate electrically connected to a first source of a first bidirectional power switch; and a first voltage clamp between the source of the first normally-open pull-down transistor and the first source of the first bidirectional power switch, wherein the second pull-down device includes: a second normally-open pull-down transistor having: a drain electrically connected to a second gate of a second bidirectional clamp switch; a source electrically connected to a second source of the second bidirectional clamp switch; and a gate electrically connected to a second source of the second bidirectional power switch; and a second voltage clamp between the source of the second normally-open pull-down transistor and the second source of the second bidirectional power switch.

[0083] Example 13. The switch device of Example 12, wherein the first pull-down device further comprises a resistor electrically connected between the first gate and the first source of the first bidirectional clamp switch, and wherein the second pull-down device further comprises a resistor electrically connected between the second gate and the second source of the second bidirectional clamp switch.

[0084] Example 14. The switching device as described in any one of Examples 9 to 13 further includes: a first overvoltage protection circuit, which is configured to: when the normally closed gate of the second bidirectional power switch is turned off, turn off the normally open gate of the first bidirectional power switch, so that the normally open gate of the first bidirectional power switch is passively controlled by the normally closed gate of the second bidirectional power switch; and a second overvoltage protection circuit, which is configured to: when the normally closed gate of the first bidirectional power switch is turned off, turn off the normally open gate of the second bidirectional power switch, so that the normally open gate of the second bidirectional power switch is passively controlled by the normally closed gate of the first bidirectional power switch.

[0085] Example 15. A switching device as described in Example 14, wherein the first overvoltage protection circuit includes one or more diodes connected in series between the normally open gate and the second source of the first bidirectional power switch, the anode of the first diode of the one or more diodes of the first overvoltage protection circuit is electrically connected to the second source of the first bidirectional power switch, and the cathode of the last diode of the one or more diodes of the first overvoltage protection circuit is electrically connected to the normally open gate of the first bidirectional power switch, wherein the second overvoltage protection circuit includes one or more diodes connected in series between the normally open gate and the first source of the second bidirectional power switch, the anode of the first diode of the one or more diodes of the second overvoltage protection circuit is electrically connected to the first source of the second bidirectional power switch, and the cathode of the last diode of the one or more diodes of the second overvoltage protection circuit is electrically connected to the normally open gate of the second bidirectional power switch.

[0086] Example 16. A switching device as described in Example 15, wherein the first overvoltage protection circuit further includes an additional diode, the additional diode having: an anode electrically connected to the cathode of the last diode of the one or more diodes of the first overvoltage protection circuit; and a cathode electrically connected to the anode of the first diode of the one or more diodes of the first overvoltage protection circuit, wherein the second overvoltage protection circuit further includes an additional diode, the additional diode having: an anode electrically connected to the cathode of the last diode of the one or more diodes of the second overvoltage protection circuit; and a cathode electrically connected to the anode of the first diode of the one or more diodes of the second overvoltage protection circuit.

[0087] Example 17. The switching device of Example 15 or 16 further includes: a first capacitor connected in parallel with the one or more diodes of the first overvoltage protection circuit; and a second capacitor connected in parallel with the one or more diodes of the second overvoltage protection circuit.

[0088] Example 18. The switching device of any of Examples 9 to 17, wherein both the first gate and the second gate of the first bidirectional clamp switch are normally closed gates, and wherein both the first gate and the second gate of the second bidirectional clamp switch are normally closed gates.

[0089] Example 19. A switching device as described in any of Examples 9 to 17, wherein the first gate of the first bidirectional clamp switch is a normally closed gate and the second gate of the first bidirectional clamp switch is a normally open gate, and wherein the first gate of the second bidirectional clamp switch is a normally open gate and the second gate of the second bidirectional clamp switch is a normally closed gate.

[0090] Example 20. A switching device, comprising: a first normally closed switch; a second normally closed switch; a first bidirectional power switch, comprising: a first source, which is electrically connected to the drain of the first normally closed switch; a second source; a first normally open gate, which is electrically connected to the source of the first normally closed switch; and a second normally open gate; a second bidirectional power switch, comprising: a first source, which is electrically connected to the second source of the first bidirectional power switch to form a cascade device; a second source, which is electrically connected to the drain of the second normally closed switch; a first normally open gate; and a second normally open gate, which are electrically connected to the source of the second normally closed switch; a first capacitor, which is electrically connected between the source of the first normally closed switch and the first normally open gate of the second bidirectional power switch; and a second capacitor, which is electrically connected between the second normally open gate of the first bidirectional power switch and the second normally open gate of the second bidirectional power switch. a first voltage clamping circuit, comprising: a first bidirectional clamping switch, the first bidirectional clamping switch having: a first gate; a second gate; a first source, which is electrically connected to the source of the first normally-off switch; and a second source, which is electrically connected to the first normally-open gate of the second bidirectional power switch; and one or more diodes between the first gate and the second source of the first bidirectional clamping switch; and a second voltage clamping circuit, comprising: a second bidirectional clamping switch, the second bidirectional clamping switch having: a first gate; a second gate; a first source, which is electrically connected to the second normally-open gate of the first bidirectional power switch; and a second source, which is electrically connected to the source of the second normally-off switch; and one or more diodes between the second gate and the first source of the second bidirectional clamping switch.

[0091] Example 21. The switching device of Example 20, wherein the first voltage clamp circuit further comprises a first pull-down device configured to prevent the first bidirectional clamp switch from turning on during dynamic switching of the switching device, and wherein the second voltage clamp circuit further comprises a second pull-down device configured to prevent the second bidirectional clamp switch from turning on during dynamic switching of the switching device.

[0092] Example 22. A switching device as described in Example 21, wherein the first pull-down device includes: a first normally-open pull-down transistor having: a drain electrically connected to a first gate of a first bidirectional clamp switch; a source electrically connected to a first source of the first bidirectional clamp switch; and a gate electrically connected to a source of a first normally-off switch; and a first voltage clamp between the source of the first normally-open pull-down transistor and the source of the first normally-off switch, wherein the second pull-down device includes: a second normally-open pull-down transistor having: a drain electrically connected to a second gate of a second bidirectional clamp switch; a source electrically connected to a second source of the second bidirectional clamp switch; and a gate electrically connected to a source of a second normally-off switch; and a second voltage clamp between the source of the second normally-open pull-down transistor and the source of the second normally-off switch.

[0093] Example 23. The switch device of Example 22, wherein the first pull-down device further comprises a resistor electrically connected between the first gate and the first source of the first bidirectional clamp switch, and wherein the second pull-down device further comprises a resistor electrically connected between the second gate and the second source of the second bidirectional clamp switch.

[0094] As used herein, the terms "having," "comprising," "including," "comprising," and the like are open-ended terms that indicate the presence of stated elements or features but do not preclude additional elements or features. The quantifiers "a," "an," and the pronoun "the" are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.

[0095] Unless otherwise expressly indicated, the expression "and / or" should be interpreted as including all possible conjunctions and disjunctions. For example, the expression "A and / or B" should be interpreted as meaning only A, only B, or both A and B. Unless otherwise expressly indicated, the expression "at least one of..." should be interpreted in the same way as "and / or". For example, the expression "at least one of A and B" should be interpreted as meaning only A, only B, or both A and B.

[0096] It is to be understood that the features of the various embodiments described herein may be combined with each other, unless specifically indicated otherwise.

[0097] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that various replacements and / or equivalent implementations may replace the specific embodiments shown and described without departing from the scope of the present invention. The present application is intended to cover any adaptation or variation of the specific embodiments discussed herein. Therefore, the present invention is intended to be limited only by the claims and their equivalents.

Claims

1. A switching device, comprising: a first power transistor die including a normally-on power transistor having a voltage at most half of a maximum rated drain-to-source voltage of the switching device; a second power transistor die comprising a normally-off power transistor having a voltage at most half of the maximum rated drain-to-source voltage of the switching device, wherein the drain of the normally-off power transistor is electrically connected to the source of the normally-on power transistor to form a cascaded device; and a first capacitor electrically connected between the gate of the normally-on power transistor and the source of the normally-off power transistor, Wherein the second power transistor die further comprises a voltage clamp circuit, the voltage clamp circuit comprising: a normally-off clamp transistor, the normally-off clamp transistor having: a drain electrode electrically connected to a gate electrode of the normally-on power transistor; and a source electrically connected to the source of the normally-off power transistor; and one or more diodes between the drain and gate of the normally-off clamp transistor.

2. The switching device of claim 1, wherein the normally-on power transistor is a normally-on GaN transistor, wherein the normally-off power transistor is a normally-off GaN transistor, and wherein the maximum rated drain-to-source voltage of the switching device is 800V or higher. 3 . The switching device of claim 1 , wherein the voltage clamp circuit further comprises a pull-down device configured to prevent the normally-off clamp transistor from turning on during dynamic switching of the switching device.

4. The switching device of claim 3, wherein the pull-down device comprises: a normally-on pull-down transistor having: a drain electrically connected to the gate of the normally-off clamp transistor; a source electrically connected to a source of the normally-off clamp transistor; and a gate electrically connected to a source of the normally-off power transistor; and A voltage clamp is provided between the source of the normally-on pull-down transistor and the source of the normally-off power transistor.

5. The switch device of claim 4, wherein the pull-down device further comprises: A resistor is electrically connected between the gate and source of the normally-off clamp transistor.

6. The switching device of claim 1 further comprising an overvoltage protection circuit configured to turn off the normally-on power transistor when the normally-off power transistor is turned off so that the cascode device is actively controlled only by the gate of the normally-off power transistor.

7. A switching device as described in claim 6, wherein the overvoltage protection circuit includes one or more diodes, which are connected in series between the gate and the source of the normally-on power transistor, wherein the anode of the first diode of the one or more diodes of the overvoltage protection circuit is electrically connected to the source of the normally-on power transistor, and wherein the cathode of the last diode of the one or more diodes of the overvoltage protection circuit is electrically connected to the gate of the normally-on power transistor.

8. The switching device according to claim 7, further comprising: A capacitor is connected in parallel with the one or more diodes of the overvoltage protection circuit.

9. A switching device, comprising: A first power transistor die including a first bidirectional power switch including a first source, a second source, a normally closed gate, and a normally open gate; a second power transistor die comprising a second bidirectional power switch, the second bidirectional power switch comprising: a first source electrically connected to a second source of the first bidirectional power switch to form a cascaded device; a second source; a normally closed gate; and a normally open gate; a first capacitor electrically connected between the normally-open gate of the second bidirectional power switch and the first source of the first bidirectional power switch; and a second capacitor electrically connected between the normally-open gate of the first bidirectional power switch and the second source of the second bidirectional power switch, The first power transistor die further includes a first voltage clamp circuit, the first voltage clamp circuit including: a first bidirectional clamp switch, the first bidirectional clamp switch having: a first gate; a second gate; a first source, which is electrically connected to the first source of the first bidirectional power switch; and a second source, which is electrically connected to the normally open gate of the second bidirectional power switch; and one or more diodes between the first gate and the second source of the first bidirectional clamp switch, The second power transistor die also includes a second voltage clamping circuit, which includes: a second bidirectional clamping switch, the second bidirectional clamping switch having: a first gate; a second gate; a first source, which is electrically connected to the normally open gate of the first bidirectional power switch; and a second source, which is electrically connected to the second source of the second bidirectional power switch; and one or more diodes between the second gate and the first source of the second bidirectional clamping switch.

10. The switching device of claim 9, wherein the first power transistor die is a first GaN die and the first bidirectional power switch has a voltage at most half of the maximum rated source-to-source voltage of the switching device, wherein the second power transistor die is a second GaN die and the second bidirectional power switch has a voltage at most half of the maximum rated source-to-source voltage of the switching device, and wherein the maximum rated source-to-source voltage of the switching device is 800 V or higher.

11. The switching device of claim 9, wherein the first voltage clamping circuit further comprises a first pull-down device configured to prevent the first bidirectional clamping switch from being turned on during dynamic switching of the switching device, and wherein the second voltage clamping circuit further comprises a second pull-down device configured to prevent the second bidirectional clamping switch from being turned on during dynamic switching of the switching device.

12. The switching device according to claim 11, The first pull-down device comprises: A first normally-on pull-down transistor having: a drain electrically connected to a first gate of a first bidirectional clamp switch; a source electrically connected to a first source of the first bidirectional clamp switch; and a gate electrically connected to a first source of the first bidirectional power switch; and a first voltage clamp between the source of the first normally-on pull-down transistor and the first source of the first bidirectional power switch, The second pull-down device comprises: a second normally-on pull-down transistor having: a drain electrically connected to a second gate of the second bidirectional clamp switch; a source electrically connected to a second source of the second bidirectional clamp switch; and a gate electrically connected to a second source of the second bidirectional power switch; and a second voltage clamp between the source of the second normally-on pull-down transistor and the second source of the second bidirectional power switch.

13. The switching device of claim 12, wherein the first pull-down device further comprises a resistor electrically connected between the first gate and the first source of the first bidirectional clamp switch, and wherein the second pull-down device further comprises a resistor electrically connected between the second gate and the second source of the second bidirectional clamp switch.

14. The switching device according to claim 9, further comprising: a first overvoltage protection circuit configured to: when the normally closed gate of the second bidirectional power switch is turned off, turn off the normally open gate of the first bidirectional power switch so that the normally open gate of the first bidirectional power switch is passively controlled by the normally closed gate of the second bidirectional power switch; and The second overvoltage protection circuit is configured to turn off the normally open gate of the second bidirectional power switch when the normally closed gate of the first bidirectional power switch is turned off, so that the normally open gate of the second bidirectional power switch is passively controlled by the normally closed gate of the first bidirectional power switch.

15. The switching device according to claim 14, wherein the first overvoltage protection circuit comprises one or more diodes, the one or more diodes are connected in series between the normally open gate and the second source of the first bidirectional power switch, the anode of the first diode among the one or more diodes of the first overvoltage protection circuit is electrically connected to the second source of the first bidirectional power switch, and the cathode of the last diode among the one or more diodes of the first overvoltage protection circuit is electrically connected to the normally open gate of the first bidirectional power switch, The second overvoltage protection circuit includes one or more diodes, which are connected in series between the normally-open gate and the first source of the second bidirectional power switch, the anode of the first diode among the one or more diodes of the second overvoltage protection circuit is electrically connected to the first source of the second bidirectional power switch, and the cathode of the last diode among the one or more diodes of the second overvoltage protection circuit is electrically connected to the normally-open gate of the second bidirectional power switch.

16. The switching device according to claim 15, wherein the first overvoltage protection circuit further comprises an additional diode having: an anode electrically connected to a cathode of a last diode among the one or more diodes of the first overvoltage protection circuit; and a cathode electrically connected to an anode of a first diode among the one or more diodes of the first overvoltage protection circuit, The second overvoltage protection circuit also includes an additional diode, which has: an anode electrically connected to the cathode of the last diode among the one or more diodes of the second overvoltage protection circuit; and a cathode electrically connected to the anode of the first diode among the one or more diodes of the second overvoltage protection circuit.

17. The switching device of claim 15, further comprising: a first capacitor connected in parallel with the one or more diodes of the first overvoltage protection circuit; and A second capacitor is connected in parallel with the one or more diodes of the second overvoltage protection circuit.

18. The switching device of claim 9, wherein both the first gate and the second gate of the first bidirectional clamp switch are normally closed gates, and wherein both the first gate and the second gate of the second bidirectional clamp switch are normally closed gates.

19. The switching device of claim 9, wherein the first gate of the first bidirectional clamp switch is a normally closed gate and the second gate of the first bidirectional clamp switch is a normally open gate, and wherein the first gate of the second bidirectional clamp switch is a normally open gate and the second gate of the second bidirectional clamp switch is a normally closed gate.

20. A switching device, comprising: First normally closed switch; Second normally closed switch; A first bidirectional power switch, comprising: a first source, which is electrically connected to the drain of the first normally closed switch; a second source; a first normally open gate, which is electrically connected to the source of the first normally closed switch; and a second normally open gate; A second bidirectional power switch, comprising: a first source electrically connected to a second source of the first bidirectional power switch to form a cascade device; a second source electrically connected to a drain of a second normally-off switch; a first normally-open gate; and a second normally-open gate electrically connected to a source of the second normally-off switch; a first capacitor electrically connected between a source of the first normally-off switch and a first normally-open gate of the second bidirectional power switch; a second capacitor electrically connected between the second normally-open gate of the first bidirectional power switch and the source of the second normally-off switch; A first voltage clamp circuit, comprising: a first bidirectional clamp switch, the first bidirectional clamp switch having: a first gate; a second gate; a first source electrically connected to a source of a first normally closed switch; and a second source electrically connected to a first normally open gate of a second bidirectional power switch; and one or more diodes between the first gate and the second source of the first bidirectional clamp switch; and The second voltage clamping circuit includes: a second bidirectional clamping switch, the second bidirectional clamping switch having: a first gate; a second gate; a first source, which is electrically connected to the second normally-open gate of the first bidirectional power switch; and a second source, which is electrically connected to the source of the second normally-off switch; and one or more diodes between the second gate and the first source of the second bidirectional clamping switch.

21. A switching device as described in claim 20, wherein the first voltage clamping circuit also includes a first pull-down device, which is configured to prevent the first bidirectional clamping switch from being turned on during dynamic switching of the switching device, and wherein the second voltage clamping circuit also includes a second pull-down device, which is configured to prevent the second bidirectional clamping switch from being turned on during dynamic switching of the switching device.

22. The switching device according to claim 21, The first pull-down device comprises: A first normally-on pull-down transistor having: a drain electrically connected to a first gate of a first bidirectional clamp switch; a source electrically connected to a first source of a first bidirectional clamp switch; and a gate electrically connected to a source of a first normally-off switch; and a first voltage clamp between the source of the first normally-on pull-down transistor and the source of the first normally-off switch, The second pull-down device comprises: a second normally-open pull-down transistor having a drain electrically connected to a second gate of the second bidirectional clamp switch, a source electrically connected to a second source of the second bidirectional clamp switch, and a gate electrically connected to a source of the second normally-off switch; and a second voltage clamp between the source of the second normally-on pull-down transistor and the source of the second normally-off switch.

23. A switching device as described in claim 22, wherein the first pull-down device further includes a resistor, which is electrically connected between the first gate and the first source of the first bidirectional clamp switch, and wherein the second pull-down device further includes a resistor, which is electrically connected between the second gate and the second source of the second bidirectional clamp switch.

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