Transient voltage suppression device with distinctive clamping characteristics

Abstract

The transient voltage suppression device comprises a first transient voltage suppression diode having a first clamping characteristic, and a second snapback diode having a second clamping characteristic, connected in series with the first transient voltage suppression diode. The first transient voltage suppression diode and the second snapback diode are electrically connected in parallel to the load device.

Description

[Background technology]

[0001] Conventional fixed protection methods utilize transient voltage suppression diodes (TVS diodes), which act as transient voltage suppressors (TVS). In this case, if a transient voltage higher than the design voltage at which the load device operates occurs, a voltage surge is generated. This transient voltage can cause circuit damage to the load device. Therefore, when an overvoltage surge occurs in the circuit, the TVS diode fixes (i.e., clamps) this voltage to a clamping voltage. However, with conventional TVS diodes, there are cases where effective protection cannot be provided to the circuit from some overvoltages. [Brief explanation of the drawing]

[0002] The present invention should be understood in detail from the following description of the embodiments illustrated in the attached drawings. [Figure 1] Figure 1 is a schematic diagram showing an exemplary electronic circuit with transient voltage protection functionality. [Figure 2] Figure 2 is a graphical representation of the operation of a transient voltage suppression (TVS) diode. [Figure 3] Figure 3 is a graph illustrating the operation of a snapback diode. [Figure 4] Figure 4 is a schematic diagram showing a TVS protection device according to an exemplary embodiment. [Figure 5] Figure 5 is a block diagram showing a stacked TVS protection device according to an exemplary embodiment. [Figure 6A] Figure 6A shows an example of a stacked TVS protection device. [Figure 6B] Figure 6B shows an example of a stacked TVS protection device according to another exemplary embodiment. [Figure 7] Figure 7 is a plan view showing a side-by-side configuration of TVS protection devices according to an exemplary embodiment. [Modes for carrying out the invention]

[0003] Overvoltage in electronic circuits can be a serious cause of damage to components within those circuits. Protection can be used to protect electronic circuits from overvoltage. For example, transient voltage suppression (TVS) diodes can be used in the circuit to protect load devices from overvoltage.

[0004] The TVS diode operates in parallel with the load device to protect against the application of source voltage. When the voltage level applied to the load device (protected load) remains at the level necessary for the load device to operate, the TVS diode does not operate, and the necessary operating current flows to the load device based on the voltage applied to it.

[0005] However, when a transient voltage surge occurs, the TVS diode turns on, protecting the protected load from overvoltage. When the TVS diode turns on, the voltage across the TVS diode is clamped at a safe level, so that damaging currents avoid the load device, and the voltage applied to the load device remains at a level that allows the load device to continue functioning. One advantage of using a TVS diode is that it can prevent circuit damage caused by transient voltage surges by maintaining circuit operation at a safe clamped voltage level.

[0006] These TVS protection devices activate when an overvoltage surge is detected, preventing harmful currents from flowing to circuit areas that could be damaged, for example, by increased current due to the overvoltage. As mentioned above, one example is that the protection device fixes and clamps the voltage across the entire circuit being protected. By fixing the voltage across the entire circuit being protected, excess current flows to another circuit, so even if the clamped transient current were to flow to the protected load, this excess current would not flow to the protected circuit or device.

[0007] Conventional TVS diodes, such as the TVS diode described in more detail below, have a clamping characteristic, which allows them to clamp (fix and limit) the voltage for the protected load device, maintaining a safe operating voltage. Another type of diode, called a snapback diode, described in more detail below, has different clamping characteristics and offers the advantage of a lower clamping ratio than conventional TVS diodes. However, once a snapback diode is turned on, it may not turn off in order to maintain the operation of the protected load by the drive power supply (i.e., voltage).

[0008] As mentioned above, one way to protect a circuit is to use a conventional TVS diode. However, as described above, using a conventional TVS diode for voltage suppression may not adequately protect the load being protected. Therefore, using a TVS diode and a snapback diode together can improve circuit protection and performance. For example, by connecting a conventional TVS diode in series with a snapback diode, the clamp ratio of the combined protection type (explained in detail below) can be brought closer to 1.0. This allows surge voltages to be suppressed to a safe level even when an appropriate operating voltage is set to drive the load being protected, providing effective protection.

[0009] The circuit protection method includes using a first transient voltage suppression diode having a first clamping characteristic and a second snapback diode having a second clamping characteristic in series with the first transient voltage suppression diode. The first transient voltage suppression diode and the second snapback diode are electrically connected in parallel to the load device.

[0010] The transient voltage suppression device has a first transient voltage suppression diode having a first clamping characteristic and a second snap-back diode connected in series with the first transient voltage suppression diode and having a second clamping characteristic. The first transient voltage suppression diode and the second snap-back diode are electrically connected in parallel to a load device.

[0011] The transient voltage suppression device has a first transient voltage suppression diode having a first clamping characteristic and a snap-back diode connected in series with the first transient voltage suppression diode and having a second clamping characteristic.

[0012] In the transient voltage suppression method and device disclosed in this specification, the voltage clamping ratio (voltage limiting ratio) of the first transient voltage suppression diode is greater than 1.0.

[0013] In the transient voltage suppression method and device disclosed in this specification, the clamping voltage (the voltage at which the device is exposed to the maximum rated surge current) of the first transient voltage suppression diode is higher than the breakdown voltage (dielectric breakdown voltage) of the first transient voltage suppression diode.

[0014] In the transient voltage suppression method and device disclosed in this specification, the voltage clamping ratio of the second snap-back diode is less than 1.0.

[0015] In the transient voltage suppression method and device disclosed in this specification, the clamping voltage of the second snap-back diode is less than the breakdown voltage of the second snap-back diode.

[0016] In the transient voltage suppression method and device disclosed in this specification, the clamping ratio of the first transient voltage suppression diode and the second snap-back diode connected in series is substantially 1.0.

[0017] In the transient voltage suppression method and device disclosed herein, the first terminal of a first transient voltage suppression diode is connected to a reference voltage, the first terminal of a second snapback diode is connected to a source voltage which is the power supply voltage of a load device, and the second terminal of the first transient voltage suppression diode is connected to the second terminal of the second snapback diode.

[0018] In the transient voltage suppression method and device disclosed herein, a first conductive layer is located on the first side of a first transient voltage suppression diode.

[0019] In the transient voltage suppression method and device disclosed herein, the second conductive layer is located on the first side of the second snapback diode.

[0020] In the transient voltage suppression method and device disclosed herein, a first conductive layer is soldered to the first side of a first transient voltage suppression diode, and a second conductive layer is soldered to the first side of a second snapback diode.

[0021] In the transient voltage suppression method and device disclosed herein, the second side of the first transient voltage suppression diode is connected to the second side of the second snapback diode with a solder layer.

[0022] Figure 1 is a schematic diagram showing an exemplary electronic circuit 100 with transient voltage protection. Note that the electronic circuit 100 is incorporated into a device that is potentially prone to transient voltage surges, and if these surges are not suppressed, they could damage the circuit (i.e., the load device). For example, an integrated circuit (IC) can be protected from harmful voltage surges caused by overvoltage by a transient protection device. These ICs can be used in numerous fields, including computers, control units, and other devices that utilize ICs that could cause damage.

[0023] As clearly shown in Figure 1, the electronic circuit 100 has a load device (a load to be protected) to which its ends are connected to a power supply voltage (shown as a positive (+) source and a negative (-) source). The TVS diode is connected to the same positive source and reference voltage (e.g., ground, earth voltage) as the load to be protected. As described above, the TVS diode is connected in parallel to the load device. With this configuration, the voltage drop across the TVS diode is the same as that of the load to be protected. Therefore, since the TVS diode receives the same voltage as the load to be protected, the TVS diode can operate in response to voltage changes across the load to be protected.

[0024] When the transient voltage exceeds the threshold, the TVS diode short-circuits the positive terminal of the source to the reference voltage. Consequently, the clamped transient current flows to the protected load. The excess transient current generated from the overvoltage (i.e., transient voltage) passes through the TVS diode and flows to the reference voltage (e.g., ground, earth).

[0025] Therefore, even if the protected load is exposed to a potentially harmful voltage surge from an overvoltage, this overvoltage will not damage the load device. This protects the device, including the electronic circuitry, from overvoltage. In one example, as described above, no potentially harmful excessive transient current due to the overvoltage flows through the protected load. Instead, this excessive transient current, generated by the overvoltage, is released from the load device, with only the clamped operating current flowing through the protected load.

[0026] The clamping operation of the TVS diode is explained in more detail below.

[0027] Figure 2 is a graph showing the operation of a TVS diode. As shown in Figure 2, the horizontal axis represents the reverse voltage operation of the TVS diode, and the vertical axis represents the reverse current operation of the TVS diode.

[0028] That is, FIG. 2 is a diagram showing the current-voltage (I-V) curve of a TVS diode. The I-V curve shows the relationship between the voltage and current across the diode. As shown in FIG. 2, I T is the current at the breakdown voltage (V BR ), and I PP is the peak current at the clamp voltage (V C ). The breakdown voltage is the voltage at which the TVS diode operates (i.e., turns on) and current begins to flow through itself. The clamp voltage is the voltage level at which the TVS diode clamps or limits the voltage across the load to be protected.

[0029] The clamp ratio (CR) of a TVS diode is the value obtained by dividing the clamping voltage of the diode (clamping voltage: V C ) by the breakdown voltage of the diode (V BR ). Therefore, the clamp ratio can be calculated according to the following formula. Clamp ratio (CR) = V C / V BR Formula 1 As shown explicitly in FIG. 2, the clamp ratio of a TVS diode is greater than 1 (i.e., CR > 1.0). By clamping the voltage at the clamp voltage, the TVS diode provides the advantage of protecting the load to be protected from overvoltage. However, since the clamp voltage is higher than the breakdown voltage, there is a possibility that an excessive voltage is applied to the load to be protected.

[0030] Returning to FIGS. 1 and 2 for explanation, it is desirable that the clamp ratio be as close to 1.0 as possible or 1.0. When an overvoltage surge exceeds the breakdown voltage of the TVS diode, the TVS diode turns on, and the voltage across the TVS diode is maintained at the clamp voltage V C . When the clamp ratio is 1.0 or substantially 1.0, the clamp voltage is approximated to the breakdown voltage of the TVS diode. Therefore, not only can the voltage be clamped at the voltage at which the TVS diode turns on, but also the safe operating voltage level of the load to be protected can be ensured.

[0031] Since the load to be protected is also connected in parallel to the TVS diode, the clamp voltage V C This is the voltage across the protected load. Therefore, with the clamped transient current flowing through the protected load, the transient surge current flows through the TVS diode and is grounded. In this way, the protected load is protected from larger surge currents that could potentially cause damage. At the same time, the protected load continues to operate because the clamped voltage flows through it due to the clamped current.

[0032] TVS diode breakdown voltage (V BR The voltage must be high enough to sustain the normal operation of the protected load. Otherwise, the voltage required for the protected load to operate will be clamped, in which case the protected load will be unable to operate.

[0033] As shown in Figure 2, the clamp voltage of the TVS diode (V C ) is the breakdown voltage (V) of the TVS diode. BR It is higher than ). Therefore, some degree of overvoltage may be applied across the protected load. Depending on the circumstances, the protected load may experience voltage surges of 10%, 20%, or more of the breakdown voltage. This level of voltage surge from an overvoltage can potentially cause damage because the protected load may not be rated to withstand this level of overvoltage.

[0034] Some devices (such as high-quality integrated circuit (IC) chips) cannot withstand surge overvoltages that cannot be prevented by TVS diodes, making protection at a voltage closer to the breakdown voltage more effective. In this case, the surge voltage is limited to a safe level in which the protected load can operate. For example, it is desirable to bring the clamp ratio as close to 1.0 as possible. As mentioned above, bringing the clamp ratio as close to 1.0 as possible protects against potentially damaging overvoltages caused by voltage surges. Furthermore, it ensures that the protected load continues to receive sufficient power to operate. To bring the clamp ratio of a TVS device closer to 1.0, a snack-back diode is added to the TVS diode in the protection circuit.

[0035] Figure 3 is a graph showing the operation of a snap diode. As shown in Figure 3, this snapback diode exhibits different characteristics from the TVS diode graph shown in Figure 2. For example, the clamp voltage is lower and smaller than the breakdown voltage. Therefore, the clamp ratio of the snapback diode is less than 1 (i.e., CR < 1.0).

[0036] Returning to Figure 1, although this is just one example, the operation of a snapback diode can be explained by replacing the TVS diode in Figure 1 with a snapback diode. A snapback diode can handle overvoltages V C Clamp it to V BR It operates (i.e., turns on).

[0037] As shown in Figure 3, I T The breakdown voltage (V BR This is the current in I PP The clamp voltage (V C The peak current at ) is the breakdown voltage. The breakdown voltage is the voltage at which the snapback TVS diode operates (i.e., turns on) and begins to pass current through itself. The clamp voltage is the voltage level at which the snapback diode clamps, or limits the voltage across the protected load.

[0038] As can be understood from Figure 3, the clamp voltage (V C ) is the breakdown voltage (V BR It is lower than ). In this case, the clamp ratio (CR) is less than 1.0 as shown in the figure. Therefore, the clamp voltage (V C ) is lower than the normal operating voltage of the protected load.

[0039] The above method can provide protection for the load to be protected, but the clamp voltage is the breakdown voltage (V BR If the value is less than ), the snapback diode will not be able to turn off after it has been turned on once. The voltage drop across the snapback diode may remain lower than the voltage drop across the protected load. In such a case, if the clamp voltage across the snapback diode remains lower than the required operating voltage of the protected load, no current will flow to the protected load.

[0040] In other words, once it is turned on, the clamp voltage (V C Since the voltage is lower than the breakdown voltage, the snapback diode will not turn off. As a result, the power required for the protected load will not be supplied.

[0041] To overcome the shortcomings of TVS diodes, for example, the source voltage and TVS diode shown in Figure 1 can be electrically connected in series with a snapback diode. That is, the TVS diode shown in Figure 1 is a TVS diode that operates as shown in Figure 2, electrically connected in series with a snapback diode, and the entire configuration of both diodes is connected in parallel to the load to be protected. In this configuration, a clamp ratio of 1.0 or very close to it can be obtained, and the load to be protected can be protected more effectively. For example, these two diodes (conventional TVS diode and snapback diode) can be incorporated into a single device.

[0042] Therefore, the conventional protection method of connecting a TVS diode in series with a snapback diode utilizes the characteristics of each type. Specifically, by connecting a conventional TVS diode with a clamp ratio greater than 1.0 in series with a snapback diode with a clamp ratio less than 1.0, a clamp ratio of 1.0 can be effectively achieved, allowing the protected load to be protected more effectively while maintaining operation.

[0043] Figure 4 is a schematic diagram showing a TVS protection device 400 according to an exemplary embodiment (e.g., a surface-mount TVS clamp diode having a conventional TVS diode and a snapback diode connected in series). As shown in Figure 4, the first terminal of the first diode 401 (e.g., a conventional TVS diode) is connected to the electrode indicated by reference numeral 1. Electrode 1 can be connected to the positive source terminal shown in Figure 1.

[0044] The first terminal of the second diode 402 (for example, a snapback diode) is connected to the second terminal of diode 401. The second terminal of the second diode 402 can be connected to the second electrode (indicated by reference numeral 2). Next, electrode 2 can be connected to the reference terminal shown in Figure 1.

[0045] Therefore, in the circuit shown in Figure 4, current flows from electrode 1 to electrode 2 through both diode 401 and diode 402. That is, diode 401 and diode 402 are connected in series with respect to electrodes 1 and 2.

[0046] Therefore, when electrode 1 is connected to the positive terminal of the circuit shown in Figure 1, and electrode 2 is connected to the reference terminal in Figure 1, current flows in parallel from the positive terminal to the reference terminal through both diodes 401 and 402 to the protected load shown in Figure 1. In this way, diodes 401 and 402, which are a single diode pair, operate as a transient voltage suppression circuit that protects the protected load in Figure 1.

[0047] As described above, by connecting the entire TVS protection device in parallel with the load to be protected, the same voltage level as the load to be protected is applied. In this case, the TVS protection device 400 operates and turns on based on the overvoltage acting across the load to be protected.

[0048] In the exemplary embodiment, the TVS diode is diode 401 and the snapback diode is diode 402, but these diodes can be connected in series in any order. That is, diode 401 can be used as a snapback diode and diode 402 can be used as a TVS diode. Furthermore, the physical arrangement of diodes 401 and 402 can be implemented in various forms.

[0049] The clamp ratio of the diode 401 and diode 402 configuration is close to or equal to 1.0 (i.e., CR = 1.0). By setting the clamp ratio to effectively 1.0, the protected load with a clamp ratio greater than or less than 1.0 can be protected more effectively.

[0050] Figure 5 is a block diagram showing a stacked TVS protection device 500 according to an exemplary embodiment. Specifically, in Figure 5, a diode pair consisting of diode 401 and diode 402 is physically arranged stacked vertically within a chip package.

[0051] Referring to Figures 4 and 5, electrode 1 is connected to the first side and terminals of a conventional TVS chip (e.g., diode 401) as shown. The first side and terminals can be formed on the lower bottom side of diode 401. Electrode 2 is connected to the first side of a snapback diode chip (e.g., diode 402) as shown. In this embodiment, the first side and terminals of the snapback diode chip may be formed on the upper side of diode 402.

[0052] In this embodiment, the second side of diode 401 is connected to the second side of diode 402. In the embodiment shown in Figure 5, the second side of diode 401 can be located on the upper side of diode 401, and the second side of diode 402 can be located on the bottom side of diode 402.

[0053] As described above, a series circuit is formed between electrode 1, diode 401, diode 402, and electrode 2. Referring to Figure 1, electrode 1 can similarly be connected to the positive terminal of the circuit shown in Figure 1, and electrode 2 can be connected to the reference terminal of the circuit shown in Figure 1. Therefore, the series circuit formed between electrode 1 and electrode 2 operates in parallel with respect to the protected load shown in Figure 1.

[0054] By connecting diodes 401 and 402 in series, the diode pair is subjected to the same voltage as the load being protected, thereby protecting it. Furthermore, the series connection ensures that the same current flows through the diode pair of diodes 401 and 402.

[0055] Figure 6A shows an exemplary assembly method of a stacked TVS protection device 600 according to an exemplary embodiment. For example, Figure 6A shows an exemplary configuration and structural assembly method of the diode shown in Figure 5. The first conductive layer (e.g., copper slag) 404 can be soldered to the first side of the snapback diode chip 402 (indicated by reference numeral 406).

[0056] A second conductive layer 405 (for example, another copper slag) can be soldered to the first side of the conventional TVS chip 401 (indicated by reference numeral 406). Another solder layer 406 can be provided between the conventional TVS chip 401 and the snapback diode chip 402 connected to the second side of the TVS chip 401 and the snapback diode chip 402. Here again, the order of the chips can be changed. That is, the conventional TVS chip 401 is located on the bottom side of the device as shown in the figure, and the snapback diode chip 402 is located on the top side as shown in the figure, but the mounting positions of these two chips can be swapped.

[0057] Figure 6B shows an exemplary assembly method of a stacked TVS protection device 601 according to another exemplary embodiment. As shown in Figure 6B, the first conductive layer 404, the second conductive layer 405, and the solder layer 406 connecting these conductive layers to the respective chips 401 and 402 are not provided.

[0058] Furthermore, as mentioned above, the physical configuration of the conventional TVS chip 401 and snapback chip 402 can be modified. For example, instead of stacking them vertically, the conventional TVS chip 401 and snapback diode chip 402 can be physically placed side by side.

[0059] Figure 7 is a plan view showing a juxtaposed configuration 700 of a TVS protection device according to an exemplary embodiment. In this configuration, a conventional TVS chip 401 and a snapback diode chip 402 are placed side by side. Furthermore, electrode 1 is connected to the first terminal of the snapback diode chip 402 as shown, and electrode 2 is connected to the first terminal of the conventional TVS chip 401 as shown. The second terminals of the conventional TVS chip 401 and the snapback diode chip 402 are connected together as in Figure 5.

[0060] In this configuration, electrode 1 can be connected to the positive terminal of the circuit shown in Figure 1, and electrode 2 can be connected to the reference terminal shown in Figure 1. Here as well, a series circuit from electrode 1 to electrode 2 is formed via the conventional TVS chip 401 and snapback diode chip 402.

[0061] To reiterate, as described above, in this embodiment, electrode 1 is connected to the positive terminal in Figure 1, and electrode 2 is connected to the reference terminal in Figure 1. In an alternative configuration, electrode 2 can be connected to the positive terminal of the circuit shown in Figure 1, and electrode 1 can be connected to the reference terminal in Figure 1.

[0062] Therefore, similar to the configuration shown in Figure 5, the circuit formed between electrode 1 and electrode 2 via diodes 401 and 402 is a series circuit. Furthermore, the series circuit formed between electrode 1 and electrode 2 operates in parallel with, for example, the circuit of the protected load in Figure 1.

[0063] Many modifications are possible based on this disclosure. While features and elements have been described above in specific combinations, each feature and element can be used alone without being used in combination with other features and elements, or in various combinations with other features and elements, or not used in combination with other features and elements at all. [Explanation of Symbols]

[0064] 1, 2 electrodes 100 electronic circuits 200, 300 Graph Display 400 TVS protection device 401, 402 diodes 500, 600, 601 Stacked TVS Protection Devices 401 TVS chip 402 Snapback Diode Chip 404 First conductive layer 405 Second conductive layer 406 Handa Formation 700 TVS protection device juxtaposition configuration

Claims

1. A method of circuit protection, A first transient voltage suppression diode having a first clamping characteristic is provided, and A second snapback diode is provided, having a second clamping characteristic and connected in series with the first transient voltage suppression diode. The first transient voltage suppression diode and the second snapback diode are electrically connected in parallel to the load device. A method for protecting a circuit, characterized by the following features.

2. The method according to claim 1, wherein the voltage clamp ratio of the first transient voltage suppression diode is greater than 1.

0.

3. The method according to claim 2, wherein the clamp voltage of the first transient voltage suppression diode is higher than the breakdown voltage of the first transient voltage suppression diode.

4. The method according to claim 1, wherein the voltage clamp ratio of the second snapback diode is less than 1.

0.

5. The method according to claim 4, wherein the clamping voltage of the second snapback diode is lower than the breakdown voltage of the second transient suppression diode.

6. The method according to claim 1, wherein the clamp ratio of the first transient voltage suppression diode and the second snapback diode connected in series is substantially 1.

0.

7. The method according to claim 1, wherein the first terminal of the first transient voltage suppression diode is connected to a reference voltage, the first terminal of the second snapback diode is connected to a source voltage which is the power supply voltage of the load device, and the second terminal of the first transient voltage suppression diode is connected to the second terminal of the second snapback diode.

8. A first transient voltage suppression diode having a first clamping characteristic, and It has a second snapback diode having a second clamping characteristic and connected in series with the first transient voltage suppression diode, The first transient voltage suppression diode and the snapback diode are electrically connected in parallel to the load device. A device that suppresses transient voltages, characterized by the following features.

9. The device according to claim 8, wherein the voltage clamp ratio of the first transient voltage suppression diode is greater than 1.

0.

10. The device according to claim 9, wherein the clamp voltage of the first transient suppression diode is higher than the breakdown voltage of the first transient suppression diode.

11. The device according to claim 8, wherein the voltage clamping ratio of the second snapback diode is less than 1.

0.

12. The device according to claim 11, wherein the clamp voltage of the second snapback diode is lower than the breakdown voltage of the second transient suppression diode.

13. The device according to claim 8, wherein the clamp ratio of the first transient suppression diode and the second snapback diode connected in series is substantially 1.

0.

14. The device according to claim 8, wherein the first terminal of the first transient suppression diode is connected to a reference voltage, the first terminal of the second snapback diode is connected to a source voltage which is the power supply voltage of the load device, and the second terminal of the first transient suppression diode is connected to the second terminal of the second snapback diode.

15. The device according to claim 14, wherein the first transient suppression diode is physically located on the second snapback diode.

16. The device according to claim 15, wherein the first transient voltage suppression diode is physically adjacent to the second snapback diode.

17. A first transient voltage suppression diode having a first clamping characteristic, and It has a second clamping characteristic and a second snapback diode connected in series with the first transient voltage suppression diode. A transient voltage suppression device characterized by the following features.

18. Furthermore, the device according to claim 17, wherein the first conductive layer is located on the first side of the first transient voltage suppression diode.

19. Furthermore, the device according to claim 18, wherein the second conductive layer is located on the first side of the second snapback diode.

20. The device according to claim 19, wherein the first conductive layer is soldered to the first side of the first transient voltage suppression diode, and the second conductive layer is soldered to the first side of the second snapback diode.

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