Cascode cascade type switching device with voltage dividing and current limiting structure

Abstract

The utility model discloses a cascode cascade type switching device with a voltage dividing and current limiting structure. The cascode cascade type switching device comprises a grid end, a source end, a drain end, a low-voltage enhanced field effect transistor, a high-voltage depletion field effect transistor and a current limiting structure. The current-limiting structure comprises a plurality of current-limiting depletion type field-effect tubes, and when the switching device is turned on, the grid electrode and source electrode voltages of the current-limiting depletion type field-effect tubes can limit the source electrode and drain electrode voltages of the adjacent current-limiting depletion type field-effect tubes. The breakdown caused by overlarge voltage of the source electrode and the drain electrode of the current-limiting depletion type field effect transistor is avoided, and the working reliability of the current-limiting depletion type field effect transistor and the whole switching device is improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing technology, and in particular relates to a common source cascade switching device with a voltage divider and current limiting structure. Background Technology

[0002] Common-source cascaded switching devices are composed of a low-voltage enhancement-mode MOSFET and a high-voltage depletion-mode MOSFET using a common-source cascade configuration. Figure 1 It is a cascaded common-source cascode switching device with a current-limiting structure, wherein the drain of the high-voltage depletion-mode field-effect transistor 15 is the drain 13 of the switching device, the gate of the low-voltage enhancement-mode field-effect transistor 14 is the gate 11 of the switching device, and the source of the low-voltage enhancement-mode field-effect transistor 14 is the source 12 of the switching device, thus achieving the enhancement-mode function.

[0003] Figure 1 The cascaded common-source cascode switching device also has a current-limiting depletion-type MOSFET 16 between the source of the low-voltage enhancement-mode MOSFET 14 and the gate of the high-voltage depletion-type MOSFET 15 as a current-limiting structure. This current-limiting structure can effectively control the magnitude of the turn-on current when the gate voltage of the high-voltage depletion-type MOSFET 15 changes, thereby stabilizing the turn-on speed of the switching device and improving the ability to control the voltage stress of the secondary-side synchronous transistor in the circuit.

[0004] However, when a smaller turn-on current or turn-on speed is required, it is necessary to reduce the absolute value of the threshold voltage of the current-limiting depletion field-effect transistor 16, such as by reducing the gate dielectric thickness of the current-limiting depletion field-effect transistor 16. This will reduce the reliability of the current-limiting depletion field-effect transistor 16, and thus affect the reliability of the entire switching device.

[0005] Therefore, there is a need to provide a common-source cascaded switching device with a current-limiting structure that has high reliability. Utility Model Content

[0006] The present invention aims to solve the above problems and provides a common source cascade switching device with a voltage divider and current limiting structure that has high reliability.

[0007] The common-source cascade switching device with a voltage divider and current limiting structure includes:

[0008] The gate terminal is used to receive the voltage signal from the driver.

[0009] The source and drain terminals are used to form a switching channel for an external load, and two semiconductor channels are provided between the source and drain terminals;

[0010] A low-voltage enhancement-mode field-effect transistor (LVFET) is provided, wherein the gate of the LVFET serves as the gate terminal of a switching device for receiving a voltage signal from a driver; the drain of the LVFET is connected to the source of a high-voltage depletion-mode field-effect transistor (DHMT); the source of the LVFET serves as the source terminal of the switching device; and the source of the LVFET is connected to the gate of the DHMT through a current-limiting structure.

[0011] The high-voltage depletion-type field-effect transistor, wherein the drain of the high-voltage field depletion-type field-effect transistor serves as the drain terminal of the switching device;

[0012] The current limiting structure includes multiple current-limiting depletion-type field-effect transistors (FETs). The gate of the first current-limiting depletion-type FET is connected to the gate of the high-voltage depletion-type FET, and the source of the first current-limiting depletion-type FET is connected to the gate of the high-voltage depletion-type FET. The gate of the nth current-limiting depletion-type FET is connected to the source of the (n-1)th current-limiting depletion-type FET, and the source of the nth current-limiting depletion-type FET is connected to the drain of the (n-1)th current-limiting depletion-type FET. The drain of the last current-limiting depletion-type FET is connected to the source of the low-voltage enhancement-type FET, where n is a positive integer greater than 1.

[0013] Compared to existing technologies, the cascaded common-source cascode switching device of this invention features a voltage divider and current-limiting structure. It incorporates multiple current-limiting depletion-type field-effect transistors (FETs) and current-limiting resistors as a current-limiting structure. When the switching device is turned on, the gate-source voltage (threshold voltage) of the current-limiting depletion-type FET can limit the source-drain voltage of adjacent current-limiting depletion-type FETs, preventing breakdown caused by excessive source-drain voltage and thus affecting the reliability of the current-limiting depletion-type FETs. This allows users to reduce the gate current of high-voltage depletion-type FETs by lowering their threshold voltage without affecting the reliability of the current-limiting depletion-type FETs or the entire switching device. This effectively solves the technical problem of poor reliability in existing cascaded common-source cascode switching devices. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a common-source cascaded switching device with a current-limiting structure;

[0015] Figure 2 This is a schematic diagram of the common-source cascaded switching device with a voltage divider and current limiting structure according to this utility model;

[0016] Figure 3This is a schematic diagram showing the variation curves of the gate voltage Vg_HEMT1 and the gate current Ig_HEMT1 of the high-voltage depletion-mode field-effect transistor in the cascaded common-source cascode switching device with voltage divider and current limiting structure of this utility model. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] This utility model discloses a common-source, common-gate cascaded switching device with a voltage divider and current limiting structure. Please refer to [reference needed]. Figure 2 , Figure 2 This is a schematic diagram of the common source cascade type switching device with voltage divider and current limiting structure of this utility model.

[0019] The switching device 20 includes a gate terminal 21, a source terminal 22, a drain terminal 23, a low-voltage enhancement-mode field-effect transistor 24, a high-voltage depletion-mode field-effect transistor 25, and a current-limiting structure 26. The gate terminal 21 is used to receive the voltage signal from the driver; the source terminal 22 and the drain terminal 23 are used to form a switching channel for an external load, and two semiconductor channels (the low-voltage enhancement-mode field-effect transistor 24 and the high-voltage depletion-mode field-effect transistor 25) are provided between the source terminal 22 and the drain terminal 23.

[0020] The gate of the low-voltage enhancement-mode field-effect transistor 24 serves as the gate terminal 21 of the switching device 20, used to receive the voltage signal from the driver; the drain of the low-voltage enhancement-mode field-effect transistor 24 is connected to the source of the high-voltage depletion-mode field-effect transistor 25, the source of the low-voltage enhancement-mode field-effect transistor 24 serves as the source terminal 22 of the switching device 20, and the source of the low-voltage enhancement-mode field-effect transistor 24 is connected to the gate of the high-voltage depletion-mode field-effect transistor 25 through a current-limiting structure 26; the drain of the high-voltage depletion-mode field-effect transistor 25 serves as the drain terminal 23 of the switching device 20.

[0021] The current limiting structure 26 includes multiple current-limiting depletion-type field-effect transistors (FETs) and a current-limiting resistor 262. The gate of the first current-limiting depletion-type field-effect transistor 2611 is connected to the gate of the high-voltage depletion-type field-effect transistor 25. The source of the first current-limiting depletion-type field-effect transistor 2611 is connected to the gate of the high-voltage depletion-type field-effect transistor 25 through the current-limiting resistor 262. The gate of the nth current-limiting depletion-type field-effect transistor 261n is connected to the source of the (n-1)th current-limiting depletion-type field-effect transistor 2613. The source of the nth current-limiting depletion-type field-effect transistor 261n is connected to the drain of the (n-1)th current-limiting depletion-type field-effect transistor 2613. The drain of the last current-limiting depletion-type field-effect transistor 261n is connected to the source of the low-voltage enhancement-type field-effect transistor 24, where n is a positive integer greater than 1. For example, the gate of the second current-limited depletion field-effect transistor 2612 is connected to the source of the first current-limited depletion field-effect transistor 2611, the source of the second current-limited depletion field-effect transistor 2612 is connected to the drain of the first current-limited depletion field-effect transistor 2611, the gate of the last current-limited depletion field-effect transistor 261n is connected to the source of the second-to-last current-limited depletion field-effect transistor 2613, the source of the last current-limited depletion field-effect transistor 261n is connected to the drain of the second-to-last current-limited depletion field-effect transistor 2613, and the drain of the last current-limited depletion field-effect transistor 261n is connected to the source of the low-voltage enhancement-mode field-effect transistor 24.

[0022] The threshold voltage of the current-limiting depletion-type field-effect transistor in the switching device of this invention 20 should be greater than the threshold voltage Vth_HEMT1 of the high-voltage depletion-type field-effect transistor 25. Here, the threshold voltage refers to the maximum gate voltage of the current-limiting depletion-type field-effect transistor in a high-resistance state (this voltage can be adjusted within a certain range).

[0023] Please refer to Figure 1 For example, reducing the threshold voltage (source-gate threshold voltage) of the current-limiting depletion field-effect transistor 16 can reduce the turn-on current of the switching device. The gate current of the high-voltage depletion field-effect transistor 15 can be equal to Vth_HEMT2 / R_HEMT2, where Vth_HEMT2 is the threshold voltage of the current-limiting depletion field-effect transistor and R_HEMT2 is the gate-source internal resistance of the current-limiting depletion field-effect transistor.

[0024] However, when the absolute value of the gate voltage of the high-voltage depletion field-effect transistor 15 is too high, it will cause the source and drain voltage of the current-limiting depletion field-effect transistor 16 to be too large, which may lead to the breakdown of the current-limiting depletion field-effect transistor and affect the working stability of the current-limiting depletion field-effect transistor and the entire switching device.

[0025] In this embodiment, the threshold voltages of the multiple current-limiting depletion-type field-effect transistors are equal. Thus, when the switching device 20 is turned on, the gate voltage Vg_HEMT1 of the high-voltage depletion-type field-effect transistor 25 increases. However, the gate voltage Vg_HEMT1 of the high-voltage depletion-type field-effect transistor 25 is less than the threshold voltage of the current-limiting depletion-type field-effect transistor. Therefore, when the high-voltage depletion-type field-effect transistor 25 is turned on, each current-limiting depletion-type field-effect transistor is still in a high-resistance state, that is, the source and gate voltages of each current-limiting depletion-type field-effect transistor are the threshold voltages. At this time, the gate current of the high-voltage depletion field-effect transistor is a constant value. This constant value is determined by the threshold voltage of the current-limiting depletion field-effect transistor, the gate-source internal resistance of the current-limiting depletion field-effect transistor, and the current-limiting resistor 262. The gate current of the high-voltage depletion field-effect transistor 25 can be equal to Vth_HEMT2 / (R_HEMT2 + Rg), where Vth_HEMT2 is the threshold voltage of the current-limiting depletion field-effect transistor, R_HEMT2 is the gate-source internal resistance of the current-limiting depletion field-effect transistor, and Rg is the resistance value of the current-limiting resistor 262.

[0026] Since the source-drain voltage of the nth current-limiting depletion-type field-effect transistor (FET) is equal to the gate-source voltage of the (n+1)th current-limiting depletion-type FET, the source-drain voltages of all current-limiting depletion-type FETs except the last one are also threshold voltages. The source-drain voltage of the last current-limiting depletion-type FET is equal to the gate voltage of the high-voltage depletion-type FET minus the voltage of the current-limiting resistor 262 and the source-gate voltages of the other current-limiting depletion-type FETs. If the switching device consists of five current-limiting depletion-type FETs, then the source-drain voltage of the last current-limiting depletion-type FET is equal to the gate voltage of the high-voltage depletion-type FET minus the voltage of the current-limiting resistor 262 and the source-drain voltages of the four current-limiting depletion-type FETs.

[0027] Therefore, as Figure 1 The gate voltage of the high-voltage depletion field-effect transistor when it is turned on is -20V. If a current-limiting structure of a single current-limiting depletion field-effect transistor is used, and a current-limiting resistor is connected between the source of the single current-limiting depletion field-effect transistor and the gate of the high-voltage depletion field-effect transistor, then the voltage division of the current-limiting resistor is -2V, and the source-drain voltage of the current-limiting depletion field-effect transistor is -18V.

[0028] If adopted Figure 2After implementing the current-limiting structure of the multi-current-limiting depletion-type field-effect transistors in this embodiment, the source-drain voltage of the last current-limiting depletion-type field-effect transistor can be determined by the gate voltage of the high-voltage depletion-type field-effect transistor, the threshold voltage of the current-limiting depletion-type field-effect transistor, and the number of current-limiting depletion-type field-effect transistors. For example, if five current-limiting depletion-type field-effect transistors are used, and the source-gate threshold voltage of each current-limiting depletion-type field-effect transistor is -2V, then the voltage division of the current-limiting resistor 262 is -2V. The source-drain voltages of the first four current-limiting depletion-type field-effect transistors are also -2V. Therefore, the source-drain voltage of the last current-limiting depletion-type field-effect transistor is -10V. This voltage is relatively low, effectively preventing the last current-limiting depletion-type field-effect transistor from being broken down (it is difficult to withstand a source-drain voltage of -18V), thus affecting the reliability of the current-limiting depletion-type field-effect transistor.

[0029] Since the source-drain voltage of the current-limited depletion field-effect transistor can be effectively controlled, the gate current of the high-voltage depletion field-effect transistor 25 can be adjusted by adjusting the threshold voltage of the current-limited depletion field-effect transistor. For example, the gate current of the high-voltage depletion field-effect transistor 25 can be reduced by decreasing the threshold voltage of the current-limited depletion field-effect transistor (which will not reduce the reliability of the current-limited depletion field-effect transistor) and simultaneously increasing the number of current-limited depletion field-effect transistors (reducing the absolute value of the source-drain voltage of the last current-limited depletion field-effect transistor).

[0030] During the turn-on process of switching device 20, the curves showing the changes in gate voltage Vg_HEMT1 and gate current Ig_HEMT1 of high-voltage depletion-mode field-effect transistor 25 are as follows: Figure 3 As shown in the figure, when the gate voltage Vg_HEMT1 of the high-voltage depletion-type field-effect transistor 25 is less than the threshold voltage Vth_HEMT2 of the current-limiting depletion-type field-effect transistor, the gate current Ig_HEMT1 (turn-on current) of the high-voltage depletion-type field-effect transistor 25 is a constant value. At this time, the user can effectively control the turn-on speed of the switching device 20 through this gate current Ig_HEMT1.

[0031] Under the discharge effect of the high-voltage depletion-mode MOSFET 25, the gate voltage Vg_HEMT1 continues to increase (the absolute value of the gate voltage gradually approaches zero). When the gate voltage Vg_HEMT1 of the high-voltage depletion-mode MOSFET 25 is greater than or equal to the threshold voltage Vth_HEMT2 of the current-limiting depletion-mode MOSFET, the first current-limiting depletion-mode MOSFET 2611 turns on and is in a low-resistance state. Subsequently, the gate voltages of other current-limiting depletion-mode MOSFETs will also sequentially exceed the threshold voltage Vth_HEMT2 of the current-limiting depletion-mode MOSFET. 2 (The source-drain voltage of the current-limiting depletion field-effect transistor when it is turned on is approximately equal to the gate-source voltage of the next current-limiting depletion field-effect transistor when it is turned on). The current-limiting depletion field-effect transistors are turned on sequentially according to their numbers. For example, the first current-limiting depletion field-effect transistor 2611, the second current-limiting depletion field-effect transistor 2612, the second to last current-limiting depletion field-effect transistor 2613, and the last current-limiting depletion field-effect transistor 261n are turned on sequentially. At this time, the current-limiting depletion field-effect transistors are in a low-resistance state, which effectively avoids the situation where some current-limiting depletion field-effect transistors are still in a high-resistance state after some of them are turned on.

[0032] When the switching device 20 is turned off, the gate voltage Vg_HEMT1 of the high-voltage depletion-type field-effect transistor 25 is greater than or equal to the threshold voltage of all current-limiting depletion-type field-effect transistors. All current-limiting depletion-type field-effect transistors are in a low-resistance state. At this time, the current of the current-limiting depletion-type field-effect transistors is the maximum, thereby achieving a faster turn-off speed and reducing turn-off losses.

[0033] Since the switching device in this embodiment mainly generates a constant gate turn-on current through the threshold voltage of the current-limiting depletion-type field-effect transistor (FET), the gate-source internal resistance of the current-limiting FET, and the current-limiting resistor, a failure of one of the current-limiting FETs (such as a short circuit) will not significantly affect the current-limiting effect. At the same time, the gate voltages of multiple current-limiting FETs can effectively limit the source-drain voltage of the current-limiting FET, effectively avoiding breakdown caused by excessive source-drain voltage, and improving the operational stability of the current-limiting FET and the entire switching device.

[0034] Preferably, in some embodiments, the current limiting structure of the switching device may not include the current limiting resistor 262, but the gate-source resistance of the first current-limiting depletion-type field-effect transistor 2611 may be directly increased as the current limiting resistor. This can further simplify the current limiting structure of the switching device. The working principle of the switching device is the same as or similar to that described in the above embodiments.

[0035] Therefore, in this embodiment, the switching device 20 can control the turn-on current and thus the turn-on speed through the current-limiting depletion field-effect transistor during the turn-on phase. Furthermore, the source-drain voltage of the depletion field-effect transistor can be reduced by adjusting the number of current-limiting depletion field-effect transistors. In the turn-off phase, the switching device 20 can achieve a large current, thereby achieving a faster turn-off speed and reducing turn-off losses. This improves the operational reliability of the current-limiting depletion field-effect transistor and the entire switching device.

[0036] The current-limiting structure of the switching device in this embodiment can be fabricated through external packaging integration. The structures of the current-limiting depletion-type field-effect transistor (FET) and the high-voltage depletion-type field-effect transistor in the current-limiting structure include, but are not limited to, metal-oxide-semiconductor field-effect transistors (MOSFETs), metal-insulation-semiconductor field-effect transistors (MISFETs), metal-semiconductor field-effect transistors (MESFETs), and high-electron-mobility transistors (HEMTs). The materials of the current-limiting depletion-type field-effect transistor and the high-voltage depletion-type field-effect transistor include, but are not limited to, gallium nitride, silicon carbide, and silicon.

[0037] The aforementioned current-limiting depletion-mode MOSFET can be integrated into the same chip as a high-voltage depletion-mode MOSFET, or it can be integrated into the same chip as a low-voltage enhancement-mode MOSFET. Furthermore, the current-limiting depletion-mode MOSFET, the high-voltage depletion-mode MOSFET, and the low-voltage enhancement-mode MOSFET can also be packaged into a single device.

[0038] This invention discloses a cascaded common-source cascode switching device with a voltage divider and current limiting structure. It incorporates multiple current-limiting depletion-type field-effect transistors (FETs) and current-limiting resistors as a current-limiting structure. When the switching device is turned on, the gate-source voltage (threshold voltage) of the current-limiting depletion-type FET limits the source-drain voltage of adjacent current-limiting depletion-type FETs, preventing breakdown caused by excessive source-drain voltage and thus affecting the reliability of the current-limiting depletion-type FETs. In this way, users can reduce the turn-on current of high-voltage depletion-type FETs by lowering the threshold voltage of the current-limiting depletion-type FETs without affecting the operational reliability of the current-limiting depletion-type FETs or the entire switching device. This effectively solves the technical problem of poor operational reliability in existing cascaded common-source cascode switching devices.

[0039] Although the present invention has been disclosed through the above embodiments, the scope of protection of the present invention is not limited thereto. Any deductions, substitutions, etc., made to the above components without departing from the concept of the present invention shall fall within the scope of the claims of the present invention.

Claims

1. A cascaded common-source cascode switching device with a voltage divider and current limiting structure, characterized in that, include: The gate terminal is used to receive the voltage signal from the driver. The source and drain terminals are used to form a switching channel for an external load, and two semiconductor channels are provided between the source and drain terminals; A low-voltage enhancement-mode field-effect transistor (LVFET), wherein the gate of the LVFET serves as the gate terminal of a switching device for receiving a voltage signal from a driver. The drain of the low-voltage enhancement-mode field-effect transistor is connected to the source of the high-voltage depletion-mode field-effect transistor. The source of the low-voltage enhancement-mode field-effect transistor serves as the source terminal of the switching device, and the source of the low-voltage enhancement-mode field-effect transistor is connected to the gate of the high-voltage depletion-mode field-effect transistor through a current-limiting structure. The high-voltage depletion-type field-effect transistor, wherein the drain of the high-voltage depletion-type field-effect transistor serves as the drain terminal of the switching device; The current limiting structure includes multiple current-limiting depletion-type field-effect transistors (FETs). The gate of the first current-limiting depletion-type FET is connected to the gate of the high-voltage depletion-type FET, and the source of the first current-limiting depletion-type FET is connected to the gate of the high-voltage depletion-type FET. The gate of the nth current-limiting depletion-type FET is connected to the source of the (n-1)th current-limiting depletion-type FET, and the source of the nth current-limiting depletion-type FET is connected to the drain of the (n-1)th current-limiting depletion-type FET. The drain of the last current-limiting depletion-type FET is connected to the source of the low-voltage enhancement-type FET, where n is a positive integer greater than 1.

2. The cascaded switching device with a voltage divider and current limiting structure according to claim 1, characterized in that, The threshold voltage of the current-limiting depletion-type field-effect transistor is greater than the threshold voltage of the high-voltage depletion-type field-effect transistor.

3. The cascaded common-source switch device with voltage divider and current limiting structure according to claim 2, characterized in that, The threshold voltages of the multiple current-limiting depletion-type field-effect transistors are equal.

4. The cascaded common-source switch device with voltage divider and current limiting structure according to claim 3, characterized in that, When the switching device is turned on, the gate voltage of the high-voltage depletion-type field-effect transistor increases; when the gate voltage of the high-voltage depletion-type field-effect transistor is less than the threshold voltage of the current-limiting depletion-type field-effect transistor, the gate current of the high-voltage depletion-type field-effect transistor is a constant value.

5. The cascaded common-source switch device with voltage divider and current limiting structure according to claim 4, characterized in that, The constant current value is determined by the threshold voltage of the current-limiting depletion field-effect transistor and the gate-source internal resistance of the current-limiting depletion field-effect transistor.

6. The cascaded switching device with a voltage divider and current limiting structure according to claim 3, characterized in that, When the switching device is turned on, the gate voltage of the high-voltage depletion type field-effect transistor increases; when the gate voltage of the high-voltage depletion type field-effect transistor is greater than or equal to the threshold voltage of the current-limiting depletion type field-effect transistor, the current-limiting depletion type field-effect transistor is in a low-resistance state.

7. The cascaded common-source switch device with voltage divider and current limiting structure according to claim 3, characterized in that, When the switching device is turned off, the gate voltage of the high-voltage depletion type field-effect transistor is greater than or equal to the threshold voltage of the current-limiting depletion type field-effect transistor, and the current-limiting depletion type field-effect transistor is in a low-resistance state.

8. The cascaded switching device with a voltage divider and current limiting structure according to claim 1, characterized in that, The current-limiting depletion-type field-effect transistor and the high-voltage depletion-type field-effect transistor are structured as metal-oxide-semiconductor field-effect transistors, metal-insulator-semiconductor field-effect transistors, metal-semiconductor field-effect transistors, or high electron mobility transistors.

9. The cascaded common-source switch device with a voltage divider and current limiting structure according to claim 1, characterized in that, The materials of the current-limiting depletion-type field-effect transistor and the high-voltage depletion-type field-effect transistor are gallium nitride, silicon carbide, or silicon.

Images