Hybrid switch device

Abstract

A hybrid switch device includes a first switch component, a second switch component, and a controller. The first switch component is independently controlled. The second switch component is connected to the first switch component in parallel, and the second switch component is independently controlled. The controller provides a control signal to respectively control the first switch component and the second switch component according to a power operating point of a operating curve. Under a light load below the power operating point, the control signal controls the first switch component to be turned on, and under a heavy load above the power operating point, the control signal controls the second switch component to be turned on so as to optimize switching performance under hybrid operation of the first switch component and the second switch component.

Description

Technical Field

[0001] This invention relates to a hybrid switching device, and more particularly to a hybrid switching device that combines a silicon carbide metal oxide semiconductor field-effect transistor and a silicon-based insulated gate bipolar transistor. Prior Technology

[0002] When using power transistor switches, a single switching element is usually not suitable for all operating conditions. For example, a single switching element has its advantages and disadvantages under light or heavy loads. Therefore, using only a single switching element for operation under different conditions will not achieve optimal performance.

[0003] Therefore, how to design a hybrid switching device, especially a hybrid switching device that combines silicon carbide metal oxide semiconductor field-effect transistors and silicon-based insulated gate bipolar transistors, to solve the problems and technical bottlenecks of the existing technology, is an important research topic for the inventors of this case. Summary of the Invention

[0004] The purpose of this invention is to provide a hybrid switching device. The hybrid switching device includes a first switching element, a second switching element, and a controller. The first switching element can be controlled independently. The second switching element is connected in parallel with the first switching element and can also be controlled independently. The controller generates a control signal and controls the first and second switching elements respectively according to the power operating point of the operating curve. Specifically, under light load conditions below the power operating point, the control signal controls the first switching element to turn on; under heavy load conditions above the power operating point, the control signal controls the second switching element to turn on, thereby optimizing the switching efficiency under hybrid operation of the first and second switching elements.

[0005] In one embodiment, under light load conditions below the power operating point, the control signal controls the second switching element to turn off; under heavy load conditions above the power operating point, the control signal controls the first switching element to turn off.

[0006] In one embodiment, under light load conditions below the power operating point, the operating curve is the first forward characteristic curve of the first switching element; under heavy load conditions above the power operating point, the operating curve is the second forward characteristic curve of the second switching element.

[0007] In one embodiment, the first switching element is a metal-oxide-semiconductor field-effect transistor, and the second switching element is an insulated-gate bipolar transistor.

[0008] In one embodiment, the metal oxide semiconductor field-effect transistor system is a silicon carbide-based metal oxide semiconductor field-effect transistor, and the insulating gate bipolar transistor system is a silicon-based insulating gate bipolar transistor.

[0009] In one embodiment, the silicon carbide metal oxide semiconductor field-effect transistor includes a first switch, a second resistor, a second resistor, and a first diode. The first resistor is connected in series with the first switch to form a first series path. The first diode is connected in series with the second resistor to form a second series path. The first series path is connected in parallel with the second series path.

[0010] In one embodiment, the silicon-based insulated gate bipolar transistor includes a second switch, a second diode, a third resistor, a fourth resistor, and a third diode. The second diode is connected in series with the second switch. The third resistor is connected in series with the second diode to form a third series path. The third diode is connected in series with the fourth resistor to form a fourth series path. The third series path is connected in parallel with the fourth series path.

[0011] In one embodiment, the number of second switching elements is greater than the number of first switching elements.

[0012] In one embodiment, the ratio of the number of first switching elements to the number of second switching elements is 1:3.

[0013] In one embodiment, the ratio of the number of first switching elements to the number of second switching elements is 2:2.

[0014] In one embodiment, the control signal includes a first control signal and a second control signal, used to control the first switching element and the second switching element respectively.

[0015] In one embodiment, when the number of silicon carbide metal oxide semiconductor field-effect transistors (MOSFETs) and the number of silicon-based insulated-gate bipolar transistors (SBBTs) are each one, the portion of the total current allocated to the MOSFET is I_total * I_SiC_ratio, and the portion of the total current allocated to the SBBT is I_total * (1 - I_SiC_ratio). Here, I_total represents the magnitude of the total current, and I_SiC_ratio represents the proportion of the total current allocated to the MOSFETs.

[0016] In one embodiment, when the forward voltage of the silicon carbide metal oxide semiconductor field-effect transistor is less than the starting voltage of the silicon-based insulated-gate bipolar transistor, I_SiC_ratio is 1; when the forward voltage of the silicon carbide metal oxide semiconductor field-effect transistor is less than the forward voltage of the silicon-based insulated-gate bipolar transistor, I_SiC_ratio is less than 1 and greater than 0.5; when the forward voltage of the silicon carbide metal oxide semiconductor field-effect transistor is equal to the forward voltage of the silicon-based insulated-gate bipolar transistor, I_SiC_ratio is 0.5; when the forward voltage of the silicon carbide metal oxide semiconductor field-effect transistor is greater than the forward voltage of the silicon-based insulated-gate bipolar transistor, I_SiC_ratio is less than 0.5 and greater than 0.

[0017] In one embodiment, when the number of silicon carbide metal oxide semiconductor field-effect transistors is one and the number of silicon-based insulated gate bipolar transistors is N, where N is a positive integer greater than 1, the silicon carbide metal oxide semiconductor field-effect transistor is controlled to flow through a portion of the total current at the optimal power efficiency point, and the remaining N silicon-based insulated gate bipolar transistors flow the remaining current.

[0018] Therefore, the hybrid switching device provided by the present invention has the following features and advantages: The design strategy of the present invention combines the use of SiC-MOSFET and Si-IGBT to give full play to the advantages of both under different operating conditions and to complement their shortcomings, thereby achieving the best performance and efficiency of the system using the hybrid switching device.

[0019] To gain a deeper understanding of the techniques, means, and effects employed by this invention to achieve its intended purpose, please refer to the following detailed description and accompanying drawings. It is believed that the purpose, features, and characteristics of this invention can be understood in a thorough and specific manner from these drawings. However, the accompanying drawings are provided for reference and illustration only and are not intended to limit the scope of this invention. Simple Explanation of the Diagram

[0020] Figure 1: A waveform diagram showing the forward characteristics of the first and second switching elements of the hybrid switching device of the present invention.

[0021] Figure 2A: is a circuit symbol diagram of the first switching element of the present invention, which is a silicon carbide metal oxide semiconductor field-effect transistor.

[0022] Figure 2B: This is the equivalent circuit diagram of the silicon carbide-based metal oxide semiconductor field-effect transistor in Figure 2A.

[0023] Figure 3A: is a circuit symbol diagram of the second switching element of the present invention, which is a silicon-based insulated gate bipolar transistor.

[0024] Figure 3B is the equivalent circuit diagram of the silicon-based insulated gate bipolar transistor in Figure 3A.

[0025] Figure 4A: is a circuit diagram of the hybrid switching device of the present invention used in parallel.

[0026] Figure 4B: is the equivalent circuit diagram of the hybrid switching devices used in parallel in Figure 4A.

[0027] Figure 5: A circuit diagram of a preferred embodiment of the application of the hybrid switching device of the present invention.

[0028] Figure 6: This is a waveform diagram showing the forward characteristics of the first and second switching elements of the hybrid switching device of the present invention, as well as the forward characteristics under hybrid drive. Implementation

[0029] The technical content and detailed description of the present invention are explained below with reference to the accompanying drawings.

[0030] Please refer to Figure 1, which is a circuit symbol diagram of the first switching element of the present invention being a silicon carbide-based metal oxide semiconductor field-effect transistor. Specifically, the hybrid switching device includes a first switching element 10 and a second switching element 20, wherein, as shown in Figure 1, the forward characteristics of the first switching element 10 and the second switching element 20 are shown. As can be seen from Figure 1, the horizontal axis represents the forward voltage of the switching element, and the vertical axis represents the forward current of the switching element. Furthermore, Figure 1 further reveals the forward characteristic curve of the first switching element 10, i.e., the first forward characteristic curve CV1, and reveals the forward characteristic curve of the second switching element 20, i.e., the second forward characteristic curve CV2.

[0031] In the foregoing embodiments, the first switching element 10 and the second switching element 20 may be, but are not limited to, any power semiconductor element type selected from insulated-gate bipolar transistors, silicon carbide power elements, silicon power elements, and / or gallium nitride power elements; wherein, the first switching element 10 and the second switching element 20 are power semiconductor elements with different forward characteristics; when below the power operating point P, under the same forward voltage, the forward current of the first switching element 10 is higher than that of the second switching element 20; and when above the power operating point P, under the same forward voltage, the forward current of the first switching element 10 is lower than that of the second switching element 20; therefore, the hybrid switching device of the present invention combines the advantages of the first switching element 10 and the second switching element 20, and when the forward current is above the power operating point P, the second switching element 20 is used as the operating switch.

[0032] In the foregoing embodiments, the first switching element 10 and the second switching element 20 are further power semiconductor elements of different power semiconductor element types and with different forward characteristics.

[0033] Please refer to Figures 2A and 2B, which are respectively circuit symbol diagrams of the first switching element 10 of the present invention being a silicon carbide metal-oxide-semiconductor field-effect transistor and the equivalent circuit diagram of the silicon carbide metal-oxide-semiconductor field-effect transistor in Figure 2A; and Figures 3A and 3B, which are respectively circuit symbol diagrams of the second switching element 20 of the present invention being a silicon-based insulated-gate bipolar transistor and the equivalent circuit diagram of the silicon-based insulated-gate bipolar transistor in Figure 3A. In the present invention, the first switching element 10 is a metal-oxide-semiconductor field-effect transistor (MOSFET), and the second switching element 20 is an insulated-gate bipolar transistor (IGBT). More specifically, the metal-oxide-semiconductor field-effect transistor (MOSFET) is a silicon carbide metal-oxide-semiconductor field-effect transistor (SiC-MOSFET), and the insulated-gate bipolar transistor (IGBT) is a silicon-based insulated-gate bipolar transistor (Si-IGBT).

[0034] As shown in Figure 2B, the first switching element 10, namely the silicon carbide metal oxide semiconductor field-effect transistor, includes a first switch 11, a first resistor 12, a second resistor 13, and a first diode 14. The first resistor 12 is connected in series with the first switch 11 to form a first series path. The first diode 14 is connected in series with the second resistor 13 to form a second series path. The first series path is connected in parallel with the second series path.

[0035] As shown in Figure 3B, the second switching element 20, namely the silicon-based insulated gate bipolar transistor, includes a second switch 21, a second diode 22, a third resistor 23, a fourth resistor 24, and a third diode 25. The second diode 22 is connected in series with the second switch 21. The third resistor 23 is connected in series with the second diode 22 to form a third series path. The third diode 25 is connected in series with the fourth resistor 24 to form a fourth series path. The third series path is connected in parallel with the fourth series path.

[0036] As shown in Figure 1, the two forward characteristic curves CV1 and CV2 are used to compare the forward characteristics of the first switching element 10 and the second switching element. For the first switching element 10, which is a silicon carbide metal-oxide-semiconductor field-effect transistor (SiC-MOSFET), the horizontal axis represents the forward voltage of the SiC-MOSFET, i.e., Vds, which is the voltage drop when current is turned on. For the second switching element 20, which is a silicon-based insulated-gate bipolar transistor (Si-IGBT), the horizontal axis represents the forward voltage of the Si-IGBT, i.e., Vce. Furthermore, for the first switching element 10, which is a silicon carbide metal-oxide-semiconductor field-effect transistor (SiC-MOSFET), the vertical axis represents the forward current of the SiC-MOSFET, i.e., Ids, which is the current that the switching element can conduct. For the second switching element 20, which is a silicon-based insulated-gate bipolar transistor (Si-IGBT), the vertical axis represents the forward current of the Si-IGBT, i.e., Ice.

[0037] Furthermore, for the first switching element 10 (see the first forward characteristic curve CV1), its curve is closer to linear, indicating a lower on-state voltage drop. Therefore, the first switching element 10 is more advantageous under high-frequency and high-current conditions. For the second switching element 20 (see the second forward characteristic curve CV2), at lower forward voltages, the forward current flowing through it is very small. Only after the forward voltage exceeds approximately 1 volt does the forward current begin to rise rapidly. Therefore, the second switching element 20 has a higher on-state voltage drop under high-current conditions.

[0038] Referring again to Figure 1, under light load conditions (i.e., low current region), the first switching element 10 (taking SiC-MOSFET as an example) has the following advantages: 1. Extremely low conduction loss: Since the on-resistance of SiC-MOSFET is extremely low and changes little with temperature rise, and the current is small under light load, the conduction loss ratio is even lower and the efficiency is higher; 2. Ultra-fast switching speed: SiC-MOSFET has a higher switching speed because its parasitic capacitance and charge are relatively low. In light load applications, high-frequency switching operation is usually critical. SiC-MOSFET can significantly reduce switching losses and EMI electromagnetic interference. Furthermore, the advantage of switching speed makes it suitable for high-frequency operation, greatly improving light load efficiency; 3. No parasitic reverse recovery current: The body diode of SiC-MOSFET has extremely low reverse recovery current, which can be almost ignored. In light load, high-frequency applications, the losses caused by reverse recovery of the body diode are greatly reduced.

[0039] Under heavy load conditions (i.e., high current regions), the second switching element 20 (taking Si-IGBT as an example) has the following advantages: 1. Strong high current handling capability: Under heavy load conditions, its current capacity can reach hundreds of amperes or even higher, and it can stably handle high power requirements; 2. High withstand voltage capability: It is usually designed as a high withstand voltage switch, and the high withstand voltage range is usually beneficial to the needs of high voltage applications; 3. Good temperature stability: It has stable performance under heavy load and high temperature environments.

[0040] Therefore, the hybrid switching device of the present invention combines the advantages of the first switching element 10 and the second switching element 20. When the forward current is lower than the power operating point P, the first switching element 10 is used as the operating switch; when the forward current is higher than the power operating point P, the second switching element 20 is used as the operating switch.

[0041] The hybrid switching device of the present invention uses a first switching element 10 and a second switching element 20 in combination. Please refer to Figures 4A and 4B, which are respectively circuit diagrams of the hybrid switching device 100 used in parallel and equivalent circuit diagrams of the hybrid switching device 100 used in parallel in Figure 4A. The hybrid switching device used in parallel includes a first switching element 10, a second switching element 20, and a controller 50 (see Figure 5 for details). The first switching element 10 can be independently controlled to be turned on or off. The second switching element 20 is connected in parallel with the first switching element 10, and the second switching element 20 can be independently controlled to be turned on or off. The controller 50 generates a control signal Sc and controls the first switching element 10 and the second switching element 20 respectively according to the power operating point of the operating curve.

[0042] As previously stated, and referring to Figure 1, the operating curve refers to the operation with the power operating point P as the dividing line. When the forward current is below the power operating point P, the system operates under the first forward characteristic curve CV1, meaning that the control signal Sc of the controller 50 turns on the first switching element 10 and turns off the second switching element 20. Conversely, when the forward current is above the power operating point P, the system operates under the second forward characteristic curve CV2, meaning that the control signal Sc of the controller 50 turns on the second switching element 20 and turns off the first switching element 10. In other words, under light load conditions below the power operating point P, the control signal Sc turns on the first switching element 10 and turns off the second switching element 20; under heavy load conditions above the power operating point P, the control signal Sc turns on the second switching element 20 and turns off the first switching element 10, thereby optimizing the switching efficiency under mixed operation of the first switching element 10 and the second switching element 20.

[0043] Please refer to Figure 5, which is a circuit diagram of a preferred embodiment of the hybrid switching device of the present invention. In this embodiment, the hybrid switching device 100 of the present invention is applied to a complete inverter bridge arm, which has an upper bridge arm BU and a lower bridge arm BL, wherein the switching architecture of the upper bridge arm BU is symmetrical to that of the lower bridge arm BL. In use, at least one first switching element 10 can be combined with at least one second switching element 20. Taking the preferred embodiment of Figure 5 as an example, taking the upper bridge arm BU as an example, the number of second switching elements 20 is greater than the number of first switching elements 10, that is, the number of Si-IGBTs is greater than the number of SiC-MOSFETs. Further, as shown in Figure 5, the ratio of the number of first switching elements 10 to the number of second switching elements 20 is 1:3, that is, when the number of first switching elements 10 in the upper bridge arm BU is one, the number of second switching elements 20 in the upper bridge arm BU is three, and so on. However, in different embodiments, the ratio of the number of first switching elements 10 to the number of second switching elements 20 can be 2:2. Therefore, when the number of first switching elements 10 in the upper bridge arm BU is two, the number of second switching elements 20 in the upper bridge arm BU is two, and so on. Similarly, for the switching architecture of the symmetrical lower bridge arm BL, when the number of first switching elements 10 in the lower bridge arm BL is two, the number of second switching elements 20 in the lower bridge arm BL is two, and so on.

[0044] Furthermore, according to the aforementioned operating principle of the power operating point based on the operating curve, under light load conditions where the load is lower than the power operating point, the first switching element 10 is controlled to be conducting, that is, the first switching element 10 is controlled to conduct by the first control signal Sc1 in the control signal Sc generated by the controller 50. Conversely, under heavy load conditions where the load is higher than the power operating point, the second switching element 20 is controlled to be conducting, that is, the second switching element 20 is controlled to conduct by the second control signal Sc2 in the control signal Sc generated by the controller 50. Thereby, the switching energy efficiency under the hybrid operation of the first switching element 10 and the second switching element 20 is optimized.

[0045] Please refer to FIG. 6, which is a schematic waveform diagram illustrating the forward characteristics of the first switching element and the second switching element and the forward characteristics under hybrid driving of the hybrid switching device of the present invention. FIG. 6 aims to illustrate the current distribution strategy of SiC-MOSFET and Si-IGBT. More specifically, the current distribution ratio is adjusted by controlling the forward voltage Vds of the SiC-MOSFET and the forward voltage Vce of the Si-IGBT, so that the system can operate at the optimal power efficiency. FIG. 6 shows the performance of a single SiC-MOSFET at 25°C and 175°C, the performance of a single Si-IGBT at 25°C and 175°C, and the performance of a hybrid combination of the two at 25°C and 175°C.

[0046] The following description takes a hybrid switching device including a single SiC-MOSFET and a single Si-IGBT as an example. Assuming the total current is I_total, and the ratio of the current flowing through the SiC-MOSFET to the total current I_total is I_SiC_ratio, therefore the ratio of the current flowing through the Si-IGBT to the total current I_total is (1-I_SiC_ratio). And the current distribution ratio I_SiC_ratio is adjusted according to the forward voltage Vds and the forward voltage Vce. In an embodiment of the present invention, when Vds<Vt0, I_SiC_ratio=1, that is, all current flows to the SiC-MOSFET. In other words, the current flowing to the SiC-MOSFET is I_total, and the current flowing to the Si-IGBT is 0. Wherein, Vt0 shown in FIG. 6 is the threshold voltage of the Si-IGBT.

[0047] When Vds<Vce,1> When I_SiC_ratio > 0.5, the current flowing through the SiC-MOSFET is greater than the current flowing through the Si-IGBT. When Vds = Vce and I_SiC_ratio = 0.5, the current flowing through the SiC-MOSFET is equal to the current flowing through the Si-IGBT, meaning the SiC-MOSFET and Si-IGBT share the current. When Vds > Vce and 0.5 > I_SiC_ratio > 0, the current flowing through the Si-IGBT is greater than the current flowing through the SiC-MOSFET.

[0048] Therefore, the current distribution ratio between SiC-MOSFET and Si-IGBT is controlled based on the Vgs of SiC-MOSFET and the relative magnitudes of Vt0 or forward voltage Vce and Vgs at the temperature of Si-IGBT. In this way, the optimal efficiency can be achieved by controlling the current distribution ratio between SiC-MOSFET and Si-IGBT.

[0049] It is worth mentioning that the temperatures shown in Figure 6 refer to the operating temperatures of the chips, such as the forward characteristics of a single Si-IGBT, a single SiC-MOSFET, and a hybrid switching element at an operating temperature of 25 degrees Celsius, or the forward characteristics of a single Si-IGBT, a single SiC-MOSFET, and a hybrid switching element at an operating temperature of 175 degrees Celsius. Incidentally, since SiC-MOSFETs and Si-IGBTs have different characteristics, the operating temperatures of the two switching elements in combination may not be the same, but information on hybrid drive can be found based on the forward characteristics at a specific temperature.

[0050] Furthermore, the onset voltage Vt0 of Si-IGBT varies at different temperatures. Moreover, the power operating point P (see Figure 1), i.e., the position where the forward voltage Vds equals the forward voltage Vce, also varies.

[0051] Furthermore, the single and hybrid drive characteristics of the aforementioned switching elements can satisfy both DC to AC and AC to DC applications. Moreover, although Figure 6 shows the forward characteristics of the first and second switching elements and the forward characteristics under hybrid drive, the same principles apply to the reverse characteristics of the first and second switching elements and the reverse characteristics under hybrid drive.

[0052] Furthermore, when the ratio of SiC-MOSFETs to Si-IGBTs is 1:N, where N is a positive integer greater than 1, the SiC-MOSFETs can be preferentially controlled to operate at their optimal power efficiency point, carrying only the portion of the total current. The remaining current is then borne by the Si-IGBTs. In other words, when multiple Si-IGBTs are connected in parallel, the current distribution ratio is adjusted based on the temperature conditions of each Si-IGBT to maintain the optimal power efficiency after the combination.

[0053] In summary, the present invention has the following features and advantages: the design strategy of combining SiC-MOSFET and Si-IGBT is designed to leverage the advantages of both under different operating conditions and to complement their shortcomings, thereby achieving the best performance and efficiency of the system using the hybrid switching device.

[0054] The above description is merely a detailed explanation and illustration of preferred embodiments of the present invention. However, the features of the present invention are not limited thereto and are not intended to limit the present invention. The scope of the present invention should be determined by the following claims. All embodiments that conform to the spirit of the claims and similar variations thereof should be included in the scope of the present invention. Any variations or modifications that can be easily conceived by those skilled in the art within the field of the present invention can be covered by the following claims.

[0055] 100: Hybrid switching device 10: First switching element 20: Second switching element 11: First Switch 12: First resistor 13: Second resistor 14: First Dipolar Body 21: Second Switch 22: Second Dipolar Body 23: Third resistor 24: Fourth resistor 25: Third Dipolar Body 50: Controller CV1: First forward characteristic curve CV2: Second forward characteristic curve P: Power Operating Point Sc: Control signal Sc1: First control signal Sc2: Second control signal BU: Upper Bridge Arm BL: Lower bridge arm

Claims

1. A hybrid switching device, comprising: A first switching element, which can be controlled independently; A second switching element is connected in parallel with the first switching element, and the second switching element can be controlled independently; A controller is provided to generate a control signal and control the first switching element and the second switching element respectively according to a power operating point of an operating curve. The forward characteristics of the first and second switching elements are as follows: below the power operating point, under the same forward voltage, the forward current of the first switching element is higher than that of the second switching element; above the power operating point, under the same forward voltage, the forward current of the first switching element is lower than that of the second switching element. Under a light load below the power operating point, the control signal controls the first switching element to conduct alone; under a heavy load above the power operating point, the control signal controls the second switching element to conduct alone. Under a light load below the power operating point, the second switching element remains completely off and does not perform switching; under a heavy load above the power operating point, the first switching element remains completely off and does not perform switching, thereby optimizing the switching efficiency under mixed operation of the first and second switching elements.

2. The hybrid switching device as claimed in claim 1, wherein under light load conditions below the power operating point, the control signal controls the second switching element to remain in a fully off state and not to perform switching; under heavy load conditions above the power operating point, the control signal controls the first switching element to remain in a fully off state and not to perform switching.

3. The hybrid switching device as claimed in claim 1, wherein under light load below the power operating point, the operating curve is a first forward characteristic curve of the first switching element; and under heavy load above the power operating point, the operating curve is a second forward characteristic curve of the second switching element.

4. The hybrid switching device as claimed in claim 1, wherein the first switching element is a metal oxide semiconductor field-effect transistor and the second switching element is an insulated gate bipolar transistor.

5. The hybrid switching device as described in claim 4, wherein the metal oxide semiconductor field-effect transistor system is a silicon carbide metal oxide semiconductor field-effect transistor, and the insulating gate bipolar transistor system is a silicon-based insulating gate bipolar transistor.

6. The hybrid switching device as claimed in claim 5, wherein the silicon carbide-based metal oxide semiconductor field-effect transistor comprises: The first switch; A first resistor is connected in series with the first switch to form a first series path; A second resistor; A first diode is connected in series with the second resistor to form a second series path; wherein the first series path is connected in parallel with the second series path.

7. The hybrid switching device as claimed in claim 5, wherein the silicon-based insulated gate bipolar transistor comprises: A second switch; A second diode is connected in series with the second switch; A third resistor, connected in series with the second diode to form a third series path; a fourth resistor; A third diode is connected in series with the fourth resistor to form a fourth series path; wherein the third series path is connected in parallel with the fourth series path.

8. The hybrid switching device as claimed in claim 1, wherein the number of the second switching elements is greater than the number of the first switching elements.

9. The hybrid switching device as claimed in claim 8, wherein the ratio of the number of the first switching element to the number of the second switching element is 1:

3.

10. The hybrid switching device as claimed in claim 8, wherein the ratio of the number of the first switching element to the number of the second switching element is 2:

2.

11. The hybrid switching device as claimed in claim 1, wherein the control signal includes a first control signal and a second control signal for controlling the first switching element and the second switching element, respectively.

12. The hybrid switching device as described in claim 5, wherein when the number of silicon carbide metal oxide semiconductor field-effect transistors and the number of silicon-based insulated-gate bipolar transistors are each one, the portion of the total current allocated to the silicon carbide metal oxide semiconductor field-effect transistors is I_total*I_SiC_ratio, and the portion of the total current allocated to the silicon-based insulated-gate bipolar transistors is I_total*(1-I_SiC_ratio); wherein, I_total represents the total current, and I_SiC_ratio represents the proportion of the total current allocated to the silicon carbide metal oxide semiconductor field-effect transistor.

13. The hybrid switching device as claimed in claim 12, wherein I_SiC_ratio is 1 when a forward voltage of the silicon carbide metal oxide semiconductor field-effect transistor is less than a starting voltage of the silicon-based insulated-gate bipolar transistor; I_SiC_ratio is less than 1 and greater than 0.5 when the forward voltage of the silicon carbide metal oxide semiconductor field-effect transistor is less than a forward voltage of the silicon-based insulated-gate bipolar transistor; I_SiC_ratio is 0.5 when the forward voltage of the silicon carbide metal oxide semiconductor field-effect transistor is equal to the forward voltage of the silicon-based insulated-gate bipolar transistor; and I_SiC_ratio is less than 0.5 and greater than 0 when the forward voltage of the silicon carbide metal oxide semiconductor field-effect transistor is greater than the forward voltage of the silicon-based insulated-gate bipolar transistor.

14. The hybrid switching device as claimed in claim 5, wherein the number of silicon carbide metal oxide semiconductor field-effect transistors is one, and the number of silicon-based insulated gate bipolar transistors is N, where N is a positive integer greater than 1, wherein the silicon carbide metal oxide semiconductor field-effect transistor is controlled to flow through a portion of the total current at an optimal power efficiency point, and the remaining N silicon-based insulated gate bipolar transistors flow the remaining current.

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