Bidirectional electrostatic discharge protection circuit

Abstract

The invention provides a bidirectional electrostatic discharge protection circuit. The bidirectional electrostatic discharge protection circuit comprises a current bleeder tube, a positive trigger protection circuit and a negative trigger protection circuit, through the cooperation of the current bleeder tube and the positive trigger protection circuit, the current bleeder tube can be ensured to be conducted when a high voltage appears at the control end of the power switch tube, and the current flows to the control end of the current bleeder tube through the first current path so as to be discharged to the second end of the current bleeder tube. Through the cooperation of the current discharge tube and the negative trigger protection circuit, the current discharge tube can be ensured to be conducted when a high voltage appears at the second end of the power switch tube, and the current is discharged from the second end of the current discharge tube to the control end of the current discharge tube. Therefore, electrostatic protection is integrally designed in the direction from the control end to the second end of the power switch tube and the direction from the second end to the control end, the electrostatic protection capability of the device is improved, the voltage working range of the control end of the power switch tube is enlarged, and the robustness of the control end of the power switch tube is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrostatic protection, and in particular to a bidirectional electrostatic discharge protection circuit suitable for a power switch tube. Background Art

[0002] HEMTs (high electron mobility transistors), such as GaN HEMTs (gallium nitride high electron mobility transistors), have poor gate robustness and are very susceptible to damage, typically requiring the addition of electrostatic protection or voltage clamping circuits between the G and S gates. Existing solutions typically only provide ESD protection in one direction, such as adding only G to S protection without designing S to G protection. This results in a higher trigger voltage for the G to S protection and a lower trigger voltage for the S to G protection, making the S to G protection circuit prone to false triggering and reducing the operating voltage range of the device gate. Summary of the Invention

[0003] The present invention aims to provide a bidirectional electrostatic discharge protection circuit to solve the problem that the electrostatic protection design for HEMT in the prior art is only in one direction (e.g., from G to S), resulting in a narrow operating voltage range for the gate of the HEMT device.

[0004] To solve the above technical problems, the present invention provides a bidirectional electrostatic discharge protection circuit, which includes:

[0005] a current discharge tube, wherein a first end of the current discharge tube is connected to the control end of the power switch tube, and a second end of the current discharge tube is connected to the second end of the power switch tube;

[0006] a positive trigger protection circuit, configured to form a first current path between the control terminal of the power switch tube and the control terminal of the current discharge tube when the voltage of the control terminal of the power switch tube is greater than a first threshold voltage, and drive the current discharge tube to conduct;

[0007] The negative trigger protection circuit is configured to form a second current path between the second end of the power switch tube and the control end of the current discharge tube when the voltage of the second end of the power switch tube is greater than a second threshold voltage, and drive the current discharge tube to conduct.

[0008] Optionally, the current discharge tube and the power switch tube are both high electron mobility transistors or field effect transistors, the first end of the current discharge tube is the source, the second end of the current discharge tube is the drain, the control end of the current discharge tube is the gate, the control end of the power switch tube is the gate, and the second end of the power switch tube is the source.

[0009] Optionally, the first threshold voltage is equal to the second threshold voltage.

[0010] Optionally, the positive trigger protection circuit includes a first threshold voltage module, a first resistor, and a first switch tube, wherein the first end of the first threshold voltage module is connected to the control end of the power switch tube, the second end of the first threshold voltage module is connected to the second end of the power switch tube through the first resistor, the control end of the first switch tube is coupled to the control end of the power switch tube, the first end of the first switch tube is connected to the first end of the voltage threshold module, and the second end of the first switch tube is connected to the control end of the current discharge tube;

[0011] The negative trigger protection circuit includes a second threshold voltage module, a second resistor and a second switch tube. The first end of the second threshold voltage module is connected to the second end of the power switch tube, the second end of the second threshold voltage module is connected to the control end of the power switch tube through the second resistor, the control end of the second switch tube is coupled to the second end of the power switch tube, the first end of the second switch tube is connected to the first end of the second voltage threshold module, and the second end of the second switch tube is connected to the control end of the current discharge tube.

[0012] Optionally, the first threshold voltage module includes one or more first diodes, and the second threshold voltage module includes one or more second diodes.

[0013] Optionally, at least one of the first diode and the second diode is a transistor with a gate-source short circuit. Optionally, the control terminal of the first switching tube is connected to the control terminal of the power switching tube via a third resistor, and the control terminal of the second switching tube is connected to the second terminal of the power switching tube via a fourth resistor.

[0014] Optionally, the positive trigger protection circuit also includes a third diode, and the negative trigger protection circuit also includes a fourth diode. The control end of the first switch tube is connected to the cathode of the third diode, and the anode of the third diode is connected to the control end of the power switch tube. The control end of the second switch tube is connected to the cathode of the fourth diode, and the anode of the fourth diode is connected to the second end of the power switch tube.

[0015] Optionally, at least one of the third diode and the fourth diode is a transistor with a gate-source short-circuited connection.

[0016] Optionally, the first switching tube, the second switching tube and the current discharge tube are HEMT transistors, the first diode, the second diode, the third diode, and the second diode are HEMT transistors with gate-source short-circuited.

[0017] Optionally, the first switch tube, the second switch tube and the current discharge tube are MOS tubes, and the first diode, the second diode, the third diode and the fourth diode are MOS transistors with gate-source short-circuited.

[0018] The bidirectional ESD protection circuit described above, through the cooperation of the current bleeder and the positive trigger protection circuit, can ensure that when a high voltage appears at the control terminal of the power switch tube, the current bleeder tube conducts, and current flows through the first current path to the control terminal of the current bleeder tube, thereby discharging to the second terminal of the current bleeder tube. The cooperation of the current bleeder and the negative trigger protection circuit can ensure that when a high voltage appears at the second terminal of the power switch tube, the current bleeder tube conducts, and current is discharged from the second terminal of the current bleeder tube to the control terminal of the current bleeder tube. Thus, the present invention integrates ESD protection in both the direction from the control terminal to the second terminal of the power switch tube and in the direction from the second terminal to the control terminal, improving the ESD protection capability of the device, increasing the voltage operating range of the control terminal of the power switch tube, and enhancing the robustness of the control terminal of the power switch tube. For example, if the power switch tube is a HEMT, the present invention can integrate ESD protection on both the G and S terminals of the HEMT device, improving the ESD capability and gate robustness of the HEMT device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0020] Figure 1 Schematic diagram of an electrostatic protection circuit for HEMT in the prior art;

[0021] Figure 2 yes Figure 1 The relationship between ESD current and gate voltage of HEMT;

[0022] Figure 3 FIG. 4 is a schematic diagram of a bidirectional electrostatic discharge protection circuit according to an embodiment of the present invention.

[0023] Figure 4 1 is a schematic diagram of current flow when the voltage at the control terminal of a power switch tube in a bidirectional electrostatic discharge protection circuit according to an embodiment of the present invention is greater than a first threshold voltage;

[0024] Figure 5 1 is a schematic diagram of the current flow when the voltage at the second terminal of the power switch tube in the bidirectional electrostatic discharge protection circuit according to an embodiment of the present invention is greater than the second threshold voltage;

[0025] Figure 6 A diagram showing the relationship between the ESD current of a power switch tube and the voltage at the control terminal of the power switch tube in a bidirectional electrostatic discharge protection circuit according to an embodiment of the present invention;

[0026] Figure 7 A schematic diagram of a bidirectional electrostatic discharge protection circuit according to an embodiment of the present invention in which a first threshold voltage module and a second threshold voltage module are configured as transistors;

[0027] Figure 8 Another schematic diagram of a bidirectional electrostatic discharge protection circuit according to an embodiment of the present invention;

[0028] Figure 9 Another schematic diagram of a bidirectional electrostatic discharge protection circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] To make the objects, advantages, and features of the present invention more clearly apparent, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale. They are only used to conveniently and clearly assist in illustrating the purposes of the embodiments of the present invention. In addition, the structures shown in the drawings are often part of the actual structure. In particular, different drawings may need to illustrate different focuses and sometimes use different scales.

[0030] As used in the present invention, the singular forms "a", "an", and "the" include plural referents, the term "or" is generally used to include "and / or", the term "several" is generally used to include "at least one", and the term "at least two" is generally used to include "two or more". In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features specified as "first", "second", and "third" may explicitly or implicitly include one or at least two of the features, "one end" and "the other end" and "proximal end" and "distal end" generally refer to two corresponding parts, which not only include endpoints, and the terms "mounted", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be a communication between two elements or an interaction relationship between two elements. In addition, as used in the present invention, "one element is disposed on another element" generally only indicates that there is a connection, coupling, cooperation, or transmission relationship between the two elements, and the connection, coupling, cooperation, or transmission between the two elements may be direct or indirect through an intermediate element. It should not be understood as indicating or implying a spatial positional relationship between the two elements. That is, one element can be in any orientation, such as inside, outside, above, below, or to one side of another element, unless the content clearly indicates otherwise. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] Figure 1 FIG. 1 is a schematic diagram of an electrostatic protection circuit for HEMT in the prior art. Figure 1 As shown, the HEMT here can be, for example, a GaN HEMT. An electrostatic protection circuit is provided between the gate (G) and source (S) of the GaN HEMT (Q1). The electrostatic protection circuit includes cascaded diodes D9 to D12, a resistor R, and a transistor Q2. The source of the transistor Q2 is connected to the gate of the GaN HEMT, the drain of the transistor Q2 is connected to the source of the GaN HEMT, the gate of the transistor Q2 is connected to the cathode of the diode D12, and the cathode of the diode D12 is connected to the source of the GaN HEMT via the resistor R. The anode of the diode D9 is connected to the gate of the GaN HEMT.

[0032] The robustness of the gate of GaN HEMT is poor. By setting up the above-mentioned electrostatic protection circuit, the protection trigger voltage in the direction from the gate to the source of GaN HEMT can be increased. However, the above-mentioned solution only provides ESD protection in one direction (i.e., protection from G to S), and does not provide protection from S to G. As a result, the protection trigger voltage in the direction from G to S is larger, while the protection trigger voltage in the direction from S to G is lower. For example, see Figure 2 , the protection trigger voltage in the G to S direction is 8.2V, while the protection trigger voltage in the S to G direction is 1.7V. The S to G protection circuit is easily triggered by mistake, which reduces the operating voltage range of the device gate.

[0033] In view of this, an embodiment of the present invention provides a bidirectional electrostatic discharge protection circuit, which can design electrostatic protection functions in both the gate-to-source direction and the source-to-gate direction of the HEMT, thereby improving the operating voltage range of the HEMT gate.

[0034] See Figure 3 、 Figure 4 and Figure 5The bidirectional electrostatic discharge protection circuit includes a current bleeder tube T3, a positive trigger protection circuit, and a negative trigger protection circuit. The first end of the current bleeder tube T3 is connected to the control end of the power switch tube T4, and the second end of the current bleeder tube T3 is connected to the second end of the power switch tube T4. The positive trigger protection circuit is configured to form a first current path between the control end of the power switch tube T4 and the control end of the current bleeder tube T3 when the voltage at the control end of the power switch tube T4 is greater than a first threshold voltage. This allows current to flow through the first current path to the control end of the current bleeder tube T3, causing the current bleeder tube T3 to conduct. After the current bleeder tube T3 conducts, the current is discharged from the control end of the current bleeder tube T3 to the second end of the current bleeder tube T3. The negative trigger protection circuit is configured to form a second current path between the second end of the power switch tube T4 and the control end of the current discharge tube T3 when the voltage at the second end of the power switch tube T4 is greater than the second threshold voltage, so that current flows to the control end of the current discharge tube T3, driving the current discharge tube T3 to be turned on. After the current discharge tube T3 is turned on, the current is discharged from the second end of the current discharge tube T3 to the control end of the current discharge tube T3.

[0035] In one embodiment, the current discharge tube T3 and the power switch tube T4 are both HEMTs (high electron mobility transistors) or field effect transistors, for example, GaN HEMTs (gallium nitride high electron mobility transistors). The first end of the current discharge tube T3 is a source, the second end of the current discharge tube T3 is a drain, the control end of the current discharge tube T3 is a gate, the control end of the power switch tube T4 is a gate, the first end of the power switch tube T4 is a drain, and the second end of the power switch tube T4 is a source.

[0036] Thus, the present invention, through the cooperation of the current discharge tube T3 and the positive trigger protection circuit, can ensure that when a higher voltage appears at the control end of the power switch tube T4, the current discharge tube T3 is turned on, and the current flows to the control end of the current discharge tube T3 through the first current path, thereby discharging to the second end of the current discharge tube T3. Through the cooperation of the current discharge tube T3 and the negative trigger protection circuit, it can ensure that when a higher voltage appears at the second end of the power switch tube T4, the current discharge tube T3 is turned on, and the current is discharged from the second end of the current discharge tube T3 to the control end of the current discharge tube T3. Thus, the present invention integrates electrostatic protection in the direction from the control end to the second end of the power switch tube T4 and in the direction from the second end to the control end, thereby improving the electrostatic protection capability of the device, increasing the voltage operating range of the control end of the power switch tube T4, and improving the robustness of the control end of the power switch tube T4. For example, if the power switch tube T4 is a GaN HEMT, the present invention can integrate electrostatic protection at both the G / S ends of the GaN HEMT device, thereby improving the ESD capability and gate robustness of the HEMT device. Figure 6, the protection trigger voltage in the G to S direction is 8.2V, and the protection trigger voltage in the S to G direction can also be set to 8.2V, so the range of the protection trigger voltage is -8.2V to 8.2V.

[0037] In one embodiment, the first threshold voltage is equal to the second threshold voltage. In other embodiments, the first threshold voltage and the second threshold voltage may be different. It is understood that when the first threshold voltage is equal to the second threshold voltage, the protection trigger voltage from the control terminal to the second terminal and the protection trigger voltage from the second terminal to the control terminal of the power switch tube T4 are equal. When the first threshold voltage is different from the second threshold voltage, the protection trigger voltage from the control terminal to the second terminal and the protection trigger voltage from the second terminal to the control terminal of the power switch tube T4 are not equal.

[0038] For example, the circuit structure of the positive trigger protection circuit includes a first threshold voltage module (D1-D4), a first resistor R1, and a first switch tube T1. The first end of the first threshold voltage module is connected to the control end of the power switch tube T4, the second end of the first threshold voltage module is connected to the second end of the power switch tube T4 through the first resistor R1, the control end of the first switch tube T1 is coupled to the control end of the power switch tube T4, the first end of the first switch tube T1 is connected to the second end of the first voltage threshold module, and the second end of the first switch tube T1 is connected to the control end of the current bleeder tube T3. It can be understood that the first current path is the control end of the power switch tube T4 → the first threshold voltage module → the first switch tube T1 → the control end of the current bleeder tube T3. In this way, when the voltage at the control end of the power switch tube T4 is greater than the first threshold voltage set by the first threshold voltage module, the first threshold voltage module is turned on, so that current appears on the first resistor R1. The voltage at the control end of the power switch tube T4 controls the first switch tube T1 to be turned on. The voltage at the node between the first threshold voltage module and the first resistor R1 reaches a corresponding value, thereby controlling the current discharge tube T3 to be turned on, so that the current is discharged from the control end of the current discharge tube T3 to the second end of the current discharge tube T3.

[0039] For example, the circuit structure of the negative trigger protection circuit includes a second threshold voltage module (D8-D5), a second resistor R2, and a second switch tube T2. The first end of the second threshold voltage module is connected to the second end of the power switch tube T4, the second end of the second threshold voltage module is connected to the control end of the power switch tube T4 through the second resistor R2, the control end of the second switch tube T2 is coupled to the second end of the power switch tube T4, the first end of the second switch tube T2 is connected to the second end of the second voltage threshold module, and the second end of the second switch tube T2 is connected to the control end of the current bleeder tube T3. It can be understood that the second current path is the second end of the power switch tube T4 → the second threshold voltage module → the second switch tube T1 → the control end of the current bleeder tube T3. In this way, when the voltage at the second end of the power switch tube T4 is greater than the second threshold voltage set by the second threshold voltage module, the second threshold voltage module is turned on, so that current appears on the second resistor R2. The voltage at the second end of the power switch tube T4 controls the second switch tube T2 to be turned on. The voltage at the node between the second threshold voltage module and the second resistor R2 reaches a corresponding value, thereby controlling the current discharge tube T3 to be turned on, so that the current is discharged from the second end of the current discharge tube T3 to the control end of the current discharge tube T3.

[0040] For example, the first threshold voltage module includes a plurality of cascaded first diodes (for example, cascaded diodes D1 to D4), and the direction from the anode to the cathode of the first diode is from the control end to the second end of the power switch tube T4. The second threshold voltage module includes a plurality of cascaded second diodes (for example, cascaded diodes D8 to D5), and the direction from the anode to the cathode of the second diode is from the second end to the control end of the power switch tube T4. It is understandable that adjusting the number of first diodes can adjust the magnitude of the first threshold voltage, and adjusting the number of second diodes can adjust the magnitude of the second threshold voltage. The first diode and the second diode can be conventional diodes in the field. Alternatively, see Figure 7 At least one of the first diode and the second diode is a transistor with a gate-source short circuit. The transistor may be a HEMT or a MOS transistor. In other embodiments, the number of first diodes in the first threshold voltage module may be only one, and the number of second diodes in the second threshold voltage module may be only one.

[0041] For example, the first switch transistor T1 is a HEMT transistor or a MOS transistor, the control terminal of the first switch transistor T1 is a gate, the first terminal of the first switch transistor T1 is a source, and the first terminal of the first switch transistor T1 is a drain. The second switch transistor T2 is a HEMT transistor or a MOS transistor, the control terminal of the second switch transistor T2 is a gate, the first terminal of the second switch transistor T2 is a source, and the first terminal of the second switch transistor T2 is a drain.

[0042] In one embodiment, the control terminal of the first switch T1 is connected to the control terminal of the power switch T4 via a third resistor R3, and the control terminal of the second switch T2 is connected to the second terminal of the power switch T4 via a fourth resistor R4. The conduction speed of the first switch T1 can be controlled by adjusting the resistance of the third resistor R3, and the conduction speed of the second switch T2 can be controlled by adjusting the resistance of the fourth resistor R4.

[0043] In another embodiment, diodes may be used to replace the third resistor and the fourth resistor. For example, see Figure 8 The positive trigger protection circuit further includes a third diode D13, and the negative trigger protection circuit further includes a fourth diode D14. The control terminal of the first switch tube T1 is connected to the cathode of the third diode D13, and the anode of the third diode D13 is connected to the control terminal of the power switch tube T4. The control terminal of the second switch tube T2 is connected to the cathode of the fourth diode D14, and the anode of the fourth diode D14 is connected to the second terminal of the power switch tube T4. The third diode D13 and the fourth diode D14 can be conventional diodes in the art. Alternatively, see Figure 9 At least one of the third diode D13 and the fourth diode D14 is a transistor with a gate-source short-circuited connection, such as a MOS transistor with a gate-source short-circuited connection.

[0044] Although the present invention is disclosed above with reference to preferred embodiments, the above embodiments are not intended to limit the present invention. Any person skilled in the art can utilize the above disclosed technical content to make many possible changes and modifications to the technical solution of the present invention without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A bidirectional electrostatic discharge protection circuit, suitable for power switch tube, characterized in that: The bidirectional electrostatic discharge protection circuit comprises: a current discharge tube, wherein a first end of the current discharge tube is connected to the control end of the power switch tube, and a second end of the current discharge tube is connected to the second end of the power switch tube; a positive trigger protection circuit, configured to form a first current path between the control terminal of the power switch tube and the control terminal of the current discharge tube when the voltage of the control terminal of the power switch tube is greater than a first threshold voltage, and drive the current discharge tube to conduct; The negative trigger protection circuit is configured to form a second current path between the second end of the power switch tube and the control end of the current discharge tube when the voltage of the second end of the power switch tube is greater than a second threshold voltage, and drive the current discharge tube to conduct.

2. The bidirectional electrostatic discharge protection circuit according to claim 1, characterized in that: The current discharge tube and the power switch tube are both high electron mobility transistors or field effect transistors; the first end of the current discharge tube is the source, the second end of the current discharge tube is the drain, the control end of the current discharge tube is the gate, the control end of the power switch tube is the gate, and the second end of the power switch tube is the source.

3. The bidirectional electrostatic discharge protection circuit according to claim 1, wherein: The first threshold voltage is equal to the second threshold voltage.

4. The bidirectional electrostatic discharge protection circuit according to claim 1, wherein: The positive trigger protection circuit includes a first threshold voltage module, a first resistor, and a first switch tube. The first end of the first threshold voltage module is connected to the control end of the power switch tube, the second end of the first threshold voltage module is connected to the second end of the power switch tube through the first resistor, the control end of the first switch tube is coupled to the control end of the power switch tube, the first end of the first switch tube is connected to the second end of the first voltage threshold module, and the second end of the first switch tube is connected to the control end of the current discharge tube. The negative trigger protection circuit includes a second threshold voltage module, a second resistor and a second switch tube. The first end of the second threshold voltage module is connected to the second end of the power switch tube, the second end of the second threshold voltage module is connected to the control end of the power switch tube through the second resistor, the control end of the second switch tube is coupled to the second end of the power switch tube, the first end of the second switch tube is connected to the second end of the second voltage threshold module, and the second end of the second switch tube is connected to the control end of the current discharge tube.

5. The bidirectional electrostatic discharge protection circuit according to claim 4, characterized in that: The first threshold voltage module includes one or more first diodes, and the second threshold voltage module includes one or more second diodes.

6. The bidirectional electrostatic discharge protection circuit according to claim 5, characterized in that: At least one of the first diode and the second diode is a transistor with a gate and a source shorted.

7. The bidirectional electrostatic discharge protection circuit according to claim 4, characterized in that: The first switch tube is a transistor, and the second switch tube is a transistor.

8. The bidirectional electrostatic discharge protection circuit according to claim 4, characterized in that: The control end of the first switch tube is connected to the control end of the power switch tube through a third resistor, and the control end of the second switch tube is connected to the second end of the power switch tube through a fourth resistor.

9. The bidirectional electrostatic discharge protection circuit according to claim 4, characterized in that: The positive trigger protection circuit also includes a third diode, and the negative trigger protection circuit also includes a fourth diode. The control end of the first switch tube is connected to the cathode of the third diode, and the anode of the third diode is connected to the control end of the power switch tube. The control end of the second switch tube is connected to the cathode of the fourth diode, and the anode of the fourth diode is connected to the second end of the power switch tube.

10. The bidirectional electrostatic discharge protection circuit according to claim 9, characterized in that: At least one of the third diode and the fourth diode is a transistor with a gate-source short-circuited.

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