Unidirectional anti-surge circuit and device

Abstract

The invention discloses a unidirectional anti-surge circuit and device. The unidirectional anti-surge circuit comprises a bidirectional TVS diode and a unidirectional diode. The bidirectional TVS diode comprises a P-type substrate, the P-type substrate comprises a first surface and a second surface which are oppositely arranged, and the first surface and the second surface are respectively diffused to form a first N-type diffusion region and a second N-type diffusion region and are respectively electrically connected with a first node and a second node; the unilateral diode comprises an anode and a cathode, the anode is electrically connected with the first node, and the cathode is electrically connected with the second node; when the voltage difference between the second node and the first node is larger than or equal to the breakdown voltage of the bidirectional TVS diode, electrons in the first N-type diffusion region or the second N-type diffusion region enter the P-type base region, and then conductance modulation is carried out on the P-type base region. The bidirectional TVS diode capable of generating the conductivity modulation effect is connected with the unidirectional diode in parallel, so that the unidirectional voltage hysteresis function is realized, and the clamping voltage of the unidirectional anti-surge circuit is further reduced.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a unidirectional surge protection circuit and device. Background Art

[0002] Unidirectional surge protection devices are one of the most commonly used electronic components. Their greatest feature is unidirectional conductivity. When the two ends of the circuit are subjected to a reverse transient high-energy impact, they can quickly change the high impedance between the two ends to a low impedance, absorb the surge power, and clamp the voltage at both ends to a fixed value, effectively protecting the precision components in the circuit from damage by various surge pulses.

[0003] With the rapid development of semiconductor technology, the critical dimensions of integrated circuits are shrinking, and operating voltages are also decreasing. Existing unidirectional surge protection devices cannot produce the conductivity modulation effect when avalanche breakdown occurs. Their resistance is large during breakdown, resulting in a high clamping voltage.

[0004] Therefore, in order to solve the above technical problems, it is necessary to provide a unidirectional surge protection circuit and device. Summary of the Invention

[0005] The object of the present invention is to provide a unidirectional surge protection circuit and device to reduce the clamping voltage and better protect the circuit.

[0006] In order to achieve the above-mentioned purpose, the technical solution provided by one embodiment of the present invention is as follows:

[0007] A unidirectional surge protection circuit, comprising a bidirectional TVS diode and a unidirectional diode connected in parallel between a first node and a second node, wherein the voltage of the first node is less than the voltage of the second node;

[0008] The bidirectional TVS diode includes a P-type substrate, the P-type substrate includes a first surface and a second surface opposite to each other, a first N-type diffusion region and a second N-type diffusion region are diffused on the first surface and the second surface, respectively, a P-type base region is located between the first N-type diffusion region and the second N-type diffusion region, and the first N-type diffusion region and the second N-type diffusion region are electrically connected to a first node and a second node, respectively;

[0009] The unidirectional diode includes an anode and a cathode, wherein the anode is electrically connected to the first node and the cathode is electrically connected to the second node; wherein,

[0010] When the voltage difference between the second node and the first node is greater than or equal to the breakdown voltage of the bidirectional TVS diode, electrons in the first N-type diffusion region enter the P-type base region, thereby modulating the conductivity of the P-type base region.

[0011] In one embodiment, the breakdown voltage of the unidirectional diode is greater than the breakdown voltage of the bidirectional TVS diode.

[0012] In one embodiment, the unidirectional diode is a Schottky diode or a rectifier diode.

[0013] In one embodiment, the first node is connected to the negative electrode of the external power supply or the ground, and the second node is connected to the positive electrode of the external power supply.

[0014] Another embodiment of the present invention provides a technical solution as follows:

[0015] A unidirectional surge protection device, comprising:

[0016] The packaging frame includes a frame body, a base island located on the frame body, and a first pin, wherein the first pin is electrically isolated from the base island;

[0017] A bidirectional TVS diode is packaged on a base island, the bidirectional TVS diode comprising a P-type substrate, the P-type substrate comprising a first surface and a second surface disposed opposite each other, a first N-type diffusion region and a second N-type diffusion region being diffusely formed on the first surface and the second surface, respectively, the P-type base region being located between the first N-type diffusion region and the second N-type diffusion region, a first metal electrode layer being provided on a surface of the first N-type diffusion region, a second metal electrode layer being provided on a surface of the second N-type diffusion region, the first metal electrode layer being packaged on the base island, and the second metal electrode layer being electrically connected to the first pin via a first bonding wire;

[0018] A unidirectional diode is packaged on the bidirectional TVS diode, the unidirectional diode comprising an anode metal layer and a cathode metal layer disposed opposite each other, one of the anode metal layer and the cathode metal layer being packaged on the second metal electrode layer of the bidirectional TVS diode, and the other being electrically connected to the base island via a second bonding wire;

[0019] When the absolute value of the voltage difference between the base island and the first pin is greater than or equal to the breakdown voltage of the bidirectional TVS diode, electrons in the first N-type diffusion region or the second N-type diffusion region enter the P-type base region, thereby modulating the conductivity of the P-type base region.

[0020] In one embodiment, the cathode metal layer of the unidirectional diode is encapsulated on the second metal electrode layer of the bidirectional TVS diode, the anode metal layer of the unidirectional diode is electrically connected to the base island via a second bonding wire, the first pin is connected to the positive electrode of the external power supply, and the base island is connected to the negative electrode of the external power supply or ground;

[0021] When the voltage difference between the first pin and the base island is greater than or equal to the breakdown voltage of the bidirectional TVS diode, electrons in the first N-type diffusion region enter the P-type base region, thereby modulating the conductivity of the P-type base region.

[0022] In one embodiment, the anode metal layer of the unidirectional diode is encapsulated on the second metal electrode layer of the bidirectional TVS diode, the cathode metal layer of the unidirectional diode is electrically connected to the base island via a second bonding wire, the first pin is connected to the negative electrode of the external power supply or the ground, and the base island is connected to the positive electrode of the external power supply;

[0023] When the voltage difference between the base island and the first pin is greater than or equal to the breakdown voltage of the bidirectional TVS diode, electrons in the second N-type diffusion region enter the P-type base region, thereby modulating the conductivity of the P-type base region.

[0024] In one embodiment, the packaging frame further includes a second pin electrically connected to the base island, and the cathode metal layer or the anode metal layer of the unidirectional diode is electrically connected to the second pin via a second bonding wire.

[0025] In one embodiment, the size of the unidirectional diode is smaller than that of the bidirectional TVS diode.

[0026] In one embodiment, the package frame includes a plurality of first pins; and / or,

[0027] The packaging frame is a DFN2020 packaging frame.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention connects a bidirectional TVS diode that can produce a conductivity modulation effect in parallel with a unidirectional diode to form a unidirectional surge protection circuit, thereby achieving a unidirectional voltage hysteresis function, further reducing the clamping voltage of the unidirectional surge protection circuit, and better protecting the circuit.

[0030] The present invention packages a bidirectional TVS diode and a unidirectional diode in parallel in a packaging frame to form a unidirectional surge protection device, which saves space on a printed circuit board and can independently control the performance parameters of the bidirectional TVS diode and the unidirectional diode. At the same time, the forward large current conducting capability of the unidirectional diode and the reverse conducting capability of the bidirectional TVS diode are utilized to achieve a balance between the forward and reverse surge current conducting capabilities, and the process is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1Schematic diagram of a unidirectional surge protection circuit in Example 1 of the present invention;

[0033] Figure 2 Schematic diagram of the structure of the bidirectional TVS diode in Example 1 of the present invention;

[0034] Figure 3 1 is a top view of a unidirectional surge protection device in Example 2 of the present invention;

[0035] Figure 4 2 is a cross-sectional view of a unidirectional surge protection device in Example 2 of the present invention;

[0036] Figure 5 1 is a comparison diagram of the clamping voltage of the unidirectional surge protection device in Comparative Example 1 and Example 2 of the present invention;

[0037] Figure 6 This is a comparison diagram of the minority carrier lifetime and minority carrier diffusion length in the N-type substrate and the P-type substrate in the present invention as a function of doping concentration.

[0038] Description of main reference numerals:

[0039] 11-base island, 1211-first pin, 1212-second pin, 1221-first bonding wire, 1222-second bonding wire, 21-bidirectional TVS diode, 211-P-type base region, 2121-first N-type diffusion region, 2122-second N-type diffusion region, 2131-first metal electrode layer, 2132-second metal electrode layer, 22-unidirectional diode, 221-N-type semiconductor layer, 222-P-type semiconductor layer, 2231-cathode metal layer, 2232-anode metal layer. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0041] Example 1:

[0042] Ginseng Figure 1 and Figure 2 As shown, this embodiment discloses a unidirectional surge protection circuit, which includes a bidirectional TVS diode 21 and a unidirectional diode 22 connected in parallel between a first node and a second node, and the voltage of the first node is less than the voltage of the second node;

[0043] The bidirectional TVS diode 21 includes a P-type substrate, which includes a first surface and a second surface opposite to each other. A first N-type diffusion region 2121 and a second N-type diffusion region 2122 are diffused on the first surface and the second surface, respectively. The P-type base region 211 is located between the first N-type diffusion region 2121 and the second N-type diffusion region 2122. The first N-type diffusion region 2121 and the second N-type diffusion region 2122 are electrically connected to a first node and a second node, respectively.

[0044] The unidirectional diode 22 includes an anode and a cathode, wherein the anode is electrically connected to the first node and the cathode is electrically connected to the second node;

[0045] When the voltage difference between the second node and the first node is greater than or equal to the breakdown voltage of the bidirectional TVS diode 21 , electrons in the first N-type diffusion region 2121 enter the P-type base region 211 , thereby modulating the conductivity of the P-type base region 211 .

[0046] Furthermore, the breakdown voltage of the unidirectional diode 22 is greater than the breakdown voltage of the bidirectional TVS diode 21 .

[0047] Specifically, the unidirectional diode 22 in this embodiment is a Schottky diode or a rectifier diode.

[0048] Illustratively, in this example, the first node is connected to the negative electrode of the external power supply or the ground, and the second node is connected to the positive electrode of the external power supply.

[0049] Specifically, the working principle of the unidirectional surge protection circuit in this embodiment is as follows:

[0050] The first node is grounded or connected to the negative pole of the external power supply, and the second node is connected to the positive pole of the external power supply. Under normal conditions, the unidirectional surge protection circuit is in the cut-off state; when a forward surge occurs, and the voltage difference between the second node and the first node is greater than or equal to the breakdown voltage of the bidirectional TVS diode 21, the electrons in the first N-type diffusion region 2121 enter the P-type base region 211 and accumulate in large quantities, modulating the conductivity of the P-type base region 211 and generating a conductivity modulation effect. At this time, the unidirectional surge protection circuit conducts through the bidirectional TVS diode 21 to conduct the surge, and under the action of the conductivity modulation effect, voltage hysteresis occurs in the bidirectional TVS diode 21, clamping the voltage of the protected circuit at a fixed value, protecting other devices from being affected by the surge and being damaged; when a reverse surge occurs, the unidirectional surge protection circuit conducts through the unidirectional diode 22 and conducts the surge.

[0051] Example 2:

[0052] Ginseng Figure 3 and Figure 4 As shown, this embodiment discloses a unidirectional surge protection device, which includes:

[0053] The packaging frame includes a frame body (not shown), a base island 11 located on the frame body, and a first pin 1211 , wherein the first pin 1211 is electrically isolated from the base island 11 ;

[0054] A bidirectional TVS diode is packaged on the base island 11. The bidirectional TVS diode includes a P-type substrate, which includes a first surface and a second surface disposed opposite each other. A first N-type diffusion region 2121 and a second N-type diffusion region 2122 are diffused on the first surface and the second surface, respectively. The P-type base region 211 is located between the first N-type diffusion region 2121 and the second N-type diffusion region 2122. A first metal electrode layer 2131 is provided on the surface of the first N-type diffusion region 2121, and a second metal electrode layer 2132 is provided on the surface of the second N-type diffusion region 2122. The first metal electrode layer 2131 is packaged on the base island 11, and the second metal electrode layer 2132 is electrically connected to the first pin 1211 via a first bonding wire 1221.

[0055] A unidirectional diode is packaged on the bidirectional TVS diode. The unidirectional diode includes an anode metal layer 2232 and a cathode metal layer 2231 that are arranged opposite each other. One of the anode metal layer 2232 and the cathode metal layer 2231 is packaged on the second metal electrode layer 2132 of the bidirectional TVS diode, and the other is electrically connected to the base island 11 via a second bonding wire 1222.

[0056] When the absolute value of the voltage difference between the base island 11 and the first pin 1211 is greater than or equal to the breakdown voltage of the bidirectional TVS diode, electrons in the first N-type diffusion region 2121 or the second N-type diffusion region 2122 enter the P-type base region 211, thereby modulating the conductivity of the P-type base region 211.

[0057] Illustratively, the packaging frame in this embodiment is a DFN2020 packaging frame.

[0058] In this embodiment, the bidirectional TVS diode has a symmetrical structure and does not need to distinguish between the cathode and the anode. Therefore, the connection mode of the unidirectional surge protection device in the circuit is determined by the cathode and the anode of the unidirectional diode.

[0059] Specifically, when the cathode metal layer 2231 of the unidirectional diode is encapsulated on the second metal electrode layer 2132 of the bidirectional TVS diode, and the anode metal layer 2232 is electrically connected to the base island 11 via the second bonding wire 1222, in the circuit, the first pin 1211 is connected to the positive electrode of the external power supply, and the base island 11 is connected to the negative electrode of the external power supply or ground. When a forward surge occurs and the voltage difference between the first pin 1211 and the base island 11 is greater than or equal to the breakdown voltage of the bidirectional TVS diode, electrons in the first N-type diffusion region 2121 enter the P-type base region 211, thereby modulating the conductivity of the P-type base region 211.

[0060] When the anode metal layer 2232 of the unidirectional diode is encapsulated on the second metal electrode layer 2132 of the bidirectional TVS diode, and the cathode metal layer 2231 is electrically connected to the base island 11 via the second bonding wire 1222, in the circuit, the first pin 1211 is connected to the negative terminal of the external power supply or ground, and the base island 11 is connected to the positive terminal of the external power supply. When a forward surge occurs and the voltage difference between the base island 11 and the first pin 1211 is greater than or equal to the breakdown voltage of the bidirectional TVS diode, electrons in the second N-type diffusion region 2122 enter the P-type base region 211, thereby modulating the conductivity of the P-type base region 211.

[0061] Illustratively, in this embodiment, the cathode metal layer 2231 of the unidirectional diode is packaged on the second metal electrode layer 2132 of the bidirectional TVS diode, and the anode metal layer 2232 is electrically connected to the base island 11 through the second bonding wire 1222 .

[0062] Preferably, the size of the unidirectional diode is smaller than that of the bidirectional TVS diode.

[0063] Illustratively, the unidirectional diode in this embodiment is a rectifier diode, including a P-type semiconductor layer 222 and an N-type semiconductor layer 221 , an anode metal layer 2232 is provided on the P-type semiconductor layer 222 , and a cathode metal layer 2231 is provided on the N-type semiconductor layer 221 .

[0064] The packaging frame in this embodiment includes a plurality of first pins. Preferably, the packaging frame in this embodiment includes two first pins.

[0065] The packaging frame in this embodiment further includes a second pin 1212 electrically connected to the base island 11 .

[0066] Illustratively, the anode metal layer 2232 of the unidirectional diode in this embodiment is electrically connected to the second pin 1212 through the second bonding wire 1222 .

[0067] Illustratively, the second pin 1212 in this embodiment is directly connected to the base island 11 .

[0068] Specifically, the working principle of the unidirectional surge protection device in this embodiment is as follows:

[0069] The cathode metal layer 2231 of the unidirectional diode is encapsulated on the second metal electrode layer 2132 of the bidirectional TVS diode, and the anode metal layer 2232 is electrically connected to the base island 11 through the second bonding wire 1222. In the circuit, the first pin 1211 is connected to the positive pole of the external power supply, and the base island 11 is connected to the negative pole of the external power supply or the ground. Under normal conditions, the unidirectional surge protection device is in the cut-off state. When a forward surge occurs and the voltage between the base island 11 and the first pin 1211 is greater than or equal to the breakdown voltage of the bidirectional TVS diode, electrons in the first N-type diffusion region 2121 enter the P-type base region 211. Since the internal structure of the bidirectional TVS diode needs to maintain electrical neutrality, the same number and concentration of holes will accumulate in the P-type base region 211. When the electrons are injected to a level equal to the hole concentration in the P-type base region 211, the additional accumulated hole concentration is equivalent to the hole doping concentration in the P-type base region 211, resulting in a decrease in the resistance of the P-type base region 211 and a significant increase in the conductivity. The unidirectional surge protection device is turned on through the bidirectional TVS diode, and voltage hysteresis occurs under the action of the conductivity modulation effect. As the current increases, the voltage will further drop, clamping the voltage of the protected circuit to a lower value, thereby better protecting the circuit. When a reverse surge occurs, the unidirectional surge protection device is turned on through the unidirectional diode and conducts the surge.

[0070] Specifically, to achieve conductivity modulation of the bidirectional TVS diode P-type base region 211 in the present invention, it is necessary to ensure that the concentration of accumulated minority carriers (i.e., electrons) in the P-type base region 211 reaches a certain value. The accumulation of minority carriers is directly related to the minority carrier lifetime and the time it takes for the minority carriers to drift through the P-type base region 211. Therefore, in order to stimulate the conductivity modulation effect of the P-type base region 211 under the action of an electric field, it is necessary to increase the minority carrier lifetime in the P-type base region 211 and reduce the time it takes for the minority carriers to drift through the P-type base region 211. The specific control method is as follows:

[0071] 1. By reducing the doping concentration of the P-type substrate, that is, controlling the resistivity of the P-type substrate, the number of recombination centers of minority carriers in the P-type base region 211 is controlled. The fewer the number of recombination centers, the longer the minority carrier lifetime.

[0072] 2. The time for minority carriers to drift through the P-type base region 211 is reduced by thinning the thickness of the P-type substrate.

[0073] It should be understood that the thickness of the P-type substrate and the resistivity of the P-type substrate should be coordinated with each other, and the above conditions must be met at the same time to produce a conductivity modulation effect in the bidirectional TVS diode. In theory, the smaller the thickness of the P-type substrate, the easier it is to stimulate the conductivity modulation of the P-type base region 211. However, if the thickness of the P-type substrate is too thin, it is not conducive to the preparation of the bidirectional TVS diode and is prone to fragmentation during the production process.

[0074] For example, the operating voltage of the unidirectional surge protection device in this embodiment is 24 V, the thickness of the P-type substrate is 220 μm, and the resistivity of the P-type substrate is 0.08-0.09 Ω·cm.

[0075] Comparative Example 1:

[0076] The unidirectional surge protection device in this comparative example is a conventional unidirectional surge protection device, including a unidirectional TVS diode and a packaging frame of conventional structure. The unidirectional TVS diode includes an N-type substrate, and the N-type substrate includes an N-type base region and a P-type diffusion region.

[0077] In this comparative example, the operating voltage of the unidirectional surge protection device is 24 V, the thickness of the N-type substrate is 360 μm, and the resistivity of the N-type substrate is 0.08 to 0.09 Ω·cm.

[0078] Compared with Example 2, the conventional unidirectional surge protection device cannot produce the conductivity modulation effect, so the clamping voltage is higher.

[0079] Ginseng Figure 5 The figure shows a comparison of the clamping voltages of Comparative Example 1 and Example 2 under the same test waveform. When avalanche breakdown occurs, the unidirectional surge protection device in Comparative Example 1 cannot produce a conductivity modulation effect, and no voltage hysteresis phenomenon occurs. When avalanche breakdown occurs, the unidirectional surge protection device in Example 2 can achieve conductivity modulation of the P-type base region 211 in the bidirectional TVS diode, and voltage hysteresis phenomenon occurs, and the clamping voltage is lower.

[0080] Table 1: Maximum peak current and clamping voltage at different test voltages

[0081]

[0082] The test results of the unidirectional surge protection devices in Example 2 and Comparative Example 1 at different test voltages are shown in Table 1. The surge test waveform is an 8 / 20μs waveform, and the measured parameters are the maximum peak current (I PP ) and clamping voltage (V C ).

[0083] As shown in Table 1, when the test voltage is the same, the unidirectional surge protection device in Example 2 has a lower clamping voltage and can withstand a higher maximum reverse peak current than that in Comparative Example 1. Furthermore, because the unidirectional surge protection device in Comparative Example 1 cannot produce a conductivity modulation effect when conducting, its resistance is relatively high during breakdown, resulting in severe heat generation and low surge withstand capability. When the test voltage exceeds 350V, the unidirectional surge protection device in Comparative Example 1 fails. However, the unidirectional surge protection device in Example 2 still functions normally when subjected to a test voltage of 510V, and the clamping voltage at this time is comparable to the clamping voltage measured for the unidirectional surge protection device in Comparative Example 1 at a test voltage of 200V.

[0084] Compared with Example 2, in Comparative Example 1, the thickness of the N-type substrate in the conventional unidirectional TVS diode is 360 μm, which is much larger than the thickness of the P-type substrate in the bidirectional TVS diode in Example 2. Minority carriers cannot accumulate in the N-type base region, and the conductivity modulation effect cannot be generated.

[0085] Ginseng Figure 6 The figure shows a comparison of the minority carrier lifetime and minority carrier diffusion length in N-type and P-type substrates. Compared with N-type substrates, P-type substrates have obvious advantages. Under the same doping concentration, the minority carrier lifetime and minority carrier diffusion length in P-type substrates are significantly better than those in N-type substrates.

[0086] Specifically, the operating voltage of the unidirectional surge protection devices in Example 2 and Comparative Example 1 is 24V. Under this operating voltage, in order to meet the surge current carrying capacity requirements of the device and reduce the loss of the device, the doping concentration of the substrate must reach 10 18 cm -3 As described above, the resistivity of the N-type substrate of the unidirectional TVS diode in Comparative Example 1 is the same as the resistivity of the P-type substrate of the bidirectional TVS diode in Example 1, both of which are 0.08-0.09 Ω·cm. At this time, only the P-type substrate can ensure a sufficiently long minority carrier lifetime and diffusion length.

[0087] It can be seen from the above technical solution that the present invention has the following beneficial effects:

[0088] The present invention connects a bidirectional TVS diode that can produce a conductivity modulation effect in parallel with a unidirectional diode to form a unidirectional surge protection circuit, thereby achieving a unidirectional voltage hysteresis function, further reducing the clamping voltage of the unidirectional surge protection circuit, and better protecting the circuit.

[0089] The present invention packages a bidirectional TVS diode and a unidirectional diode in parallel in a packaging frame to form a unidirectional surge protection device, which saves space on a printed circuit board and can independently control the performance parameters of the bidirectional TVS diode and the unidirectional diode. At the same time, the forward large current conducting capability of the unidirectional diode and the reverse conducting capability of the bidirectional TVS diode are utilized to achieve a balance between the forward and reverse surge current conducting capabilities, and the process is stable.

[0090] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0091] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A unidirectional surge protection circuit, characterized in that: The unidirectional surge protection circuit includes a bidirectional TVS diode and a unidirectional diode connected in parallel between a first node and a second node, and the voltage of the first node is less than the voltage of the second node; The bidirectional TVS diode includes a P-type substrate, the P-type substrate includes a first surface and a second surface opposite to each other, a first N-type diffusion region and a second N-type diffusion region are diffused on the first surface and the second surface, respectively, a P-type base region is located between the first N-type diffusion region and the second N-type diffusion region, and the first N-type diffusion region and the second N-type diffusion region are electrically connected to a first node and a second node, respectively; The unidirectional diode includes an anode and a cathode, wherein the anode is electrically connected to the first node and the cathode is electrically connected to the second node; wherein, When the voltage difference between the second node and the first node is greater than or equal to the breakdown voltage of the bidirectional TVS diode, electrons in the first N-type diffusion region enter the P-type base region, thereby modulating the conductivity of the P-type base region.

2. The unidirectional surge protection circuit according to claim 1, characterized in that: The breakdown voltage of the unidirectional diode is greater than the breakdown voltage of the bidirectional TVS diode.

3. The unidirectional surge protection circuit according to claim 1, characterized in that: The unidirectional diode is a Schottky diode or a rectifier diode.

4. The unidirectional surge protection circuit according to claim 1, characterized in that: The first node is connected to the negative electrode of the external power supply or the ground, and the second node is connected to the positive electrode of the external power supply.

5. A unidirectional surge protection device, characterized in that: The unidirectional surge protection device comprises: The packaging frame includes a frame body, a base island located on the frame body, and a first pin, wherein the first pin is electrically isolated from the base island; A bidirectional TVS diode is packaged on a base island, the bidirectional TVS diode comprising a P-type substrate, the P-type substrate comprising a first surface and a second surface disposed opposite each other, a first N-type diffusion region and a second N-type diffusion region being diffusely formed on the first surface and the second surface, respectively, the P-type base region being located between the first N-type diffusion region and the second N-type diffusion region, a first metal electrode layer being provided on a surface of the first N-type diffusion region, a second metal electrode layer being provided on a surface of the second N-type diffusion region, the first metal electrode layer being packaged on the base island, and the second metal electrode layer being electrically connected to the first pin via a first bonding wire; A unidirectional diode is packaged on the bidirectional TVS diode, the unidirectional diode comprising an anode metal layer and a cathode metal layer disposed opposite each other, one of the anode metal layer and the cathode metal layer being packaged on the second metal electrode layer of the bidirectional TVS diode, and the other being electrically connected to the base island via a second bonding wire; When the absolute value of the voltage difference between the base island and the first pin is greater than or equal to the breakdown voltage of the bidirectional TVS diode, electrons in the first N-type diffusion region or the second N-type diffusion region enter the P-type base region, thereby modulating the conductivity of the P-type base region.

6. The unidirectional surge protection device according to claim 5, characterized in that: The cathode metal layer of the unidirectional diode is encapsulated on the second metal electrode layer of the bidirectional TVS diode, the anode metal layer of the unidirectional diode is electrically connected to the base island through a second bonding wire, the first pin is connected to the positive electrode of the external power supply, and the base island is connected to the negative electrode of the external power supply or ground; When the voltage difference between the first pin and the base island is greater than or equal to the breakdown voltage of the bidirectional TVS diode, electrons in the first N-type diffusion region enter the P-type base region, thereby modulating the conductivity of the P-type base region.

7. The unidirectional surge protection device according to claim 5, characterized in that: The anode metal layer of the unidirectional diode is encapsulated on the second metal electrode layer of the bidirectional TVS diode, the cathode metal layer of the unidirectional diode is electrically connected to the base island through a second bonding wire, the first pin is connected to the negative electrode of the external power supply or the ground, and the base island is connected to the positive electrode of the external power supply; When the voltage difference between the base island and the first pin is greater than or equal to the breakdown voltage of the bidirectional TVS diode, electrons in the second N-type diffusion region enter the P-type base region, thereby modulating the conductivity of the P-type base region.

8. The unidirectional surge protection device according to claim 5, characterized in that: The packaging frame further includes a second pin electrically connected to the base island, and the cathode metal layer or the anode metal layer of the unidirectional diode is electrically connected to the second pin via a second bonding wire.

9. The unidirectional surge protection device according to claim 5, characterized in that: The size of the unidirectional diode is smaller than that of the bidirectional TVS diode.

10. The unidirectional surge protection device according to claim 5, characterized in that: The package frame includes a plurality of first pins; and / or, The packaging frame is a DFN2020 packaging frame.

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