Transient voltage suppression device with clamping characteristic

Abstract

A transient voltage suppression device includes a first transient voltage suppression diode having a first clamping characteristic, and a second bounce diode having a second clamping characteristic in series with the first transient voltage suppression diode. The first transient voltage suppression diode and the second jump-back diode are electrically connected in parallel to the load.

Description

BACKGROUND

[0001] Conventional clamping protection schemes include the use of transient voltage suppression (TVS) diodes. Voltage surges occur when a transient voltage increases the voltage across a load above the voltage for which the load was designed to operate. Such overvoltage can damage the circuitry of the load. By using a TVS diode, when an overvoltage surge occurs in a circuit, the TVS diode clamps (i.e., limits) the voltage to a clamping voltage. However, utilizing conventional TVS diodes can not provide effective protection to protect a circuit from some overvoltages. BRIEF DESCRIPTION OF DRAWINGS

[0002] A more detailed understanding can be had from the following description, given by way of example in conjunction with the accompanying drawings wherein:

[0003] Figure 1 is a schematic diagram of an example electronic circuit including transient voltage protection;

[0004] Figure 2 is a graphical representation of the operation of a transient voltage suppression (TVS) diode;

[0005] Figure 3 is a graphical representation of the operation of a snap-back diode;

[0006] Figure 4 is a schematic diagram of a TVS protection device according to an example embodiment;

[0007] Figure 5 is a block diagram of a stacked TVS protection device according to an example embodiment;

[0008] Figure 6A Example components of a stacked TVS protection device are shown;

[0009] Figure 6B Example components of a stacked TVS protection device according to an alternative example embodiment are shown; and

[0010] Figure 7 is a plan view of a side-by-side arrangement of TVS protection devices according to an example embodiment. DETAILED DESCRIPTION

[0011] Overvoltages in electronic circuits can cause significant damage to components in the electronic circuit. To protect an electronic circuit from overvoltages, protection can be employed. In some examples, protection circuitry such as a transient voltage suppression (TVS) diode can be utilized in circuitry to protect a load from overvoltages.

[0012] TVS diodes operate by connecting in parallel with a load to protect across a source voltage. The TVS diode does not operate when the voltage level across the protected load is maintained at a level for operation of the load. The operating voltage across the load allows the necessary operating current to flow through the load to operate.

[0013] However, when a transient voltage surge occurs, the TVS diode turns on to protect the protected load from the overvoltage. By turning on, the TVS diode clamps (limits) the voltage to a safe level to maintain the voltage across the load at a level at which the load can continue to work while the potentially damaging current is directed away from the load. The advantage of using a TVS diode is that voltage transient surges can be prevented from damaging the circuit while the circuit maintains operation at the safe clamped voltage level.

[0014] These TVS protection devices operate when an overvoltage surge is detected to prevent damaging current from flowing through areas of the circuitry that can be damaged due to an increase in current, for example, due to the overvoltage. As mentioned above, in one example, the protection device clamps and limits the voltage across the protected circuitry. By clamping the voltage across the protected circuitry, even if the clamped transient current continues to flow through the protected load, the excess current is re-routed to another path that prevents it from flowing through the protected circuitry and device.

[0015] A conventional TVS diode, such as will be described in more detail below, includes a clamping characteristic that allows it to effectively clamp the voltage for the protected load to maintain a safe operating voltage. Another type of diode, referred to as a snapback diode, which will also be described in further detail below, includes a different clamping characteristic that includes the advantage of a lower clamping ratio than a conventional TVS diode. However, once turned on, a snapback diode can not turn off to allow the operating power (i.e., voltage) to maintain operation of the protected load.

[0016] As mentioned above, one example for protecting a circuit is with a conventional TVS diode. However, as mentioned above, voltage suppression with a conventional TVS diode can not provide adequate protection to the protected load. Thus, utilizing both a TVS diode and a snapback diode together can provide enhanced circuit protection and performance. For example, by utilizing a conventional TVS diode connected in series with a snapback diode, the clamping ratio (discussed in more detail below) of the combined protection scheme can approach 1.0, which provides more effective protection by limiting any surge voltage to a safe level while providing the appropriate operating voltage for the protected load to operate.

[0017] A method for circuit protection includes providing 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 a load.

[0018] A transient voltage suppression device includes 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 a load.

[0019] A transient voltage suppression device includes a first transient voltage suppression diode having a first clamping characteristic and a snapback diode having a second clamping characteristic in series with the first transient voltage suppression diode.

[0020] Described herein is a transient voltage suppression method and device in which the first transient voltage suppression diode has a voltage clamping ratio greater than 1.0.

[0021] Described herein is a transient voltage suppression method and device in which the clamping voltage of the first transient voltage suppression diode is higher than the breakdown voltage of the first transient voltage suppression diode.

[0022] Described herein is a transient voltage suppression method and device in which the second snapback diode has a voltage clamping ratio less than 1.0.

[0023] Described herein is a transient voltage suppression method and device in which the clamping voltage of the second snapback diode is less than the breakdown voltage of the second snapback diode.

[0024] Described herein is a transient voltage suppression method and device in which the clamping ratio of the first transient voltage suppression diode and the second snapback diode connected in series is substantially 1.0.

[0025] Described herein is a transient voltage suppression method and device in which a first terminal of the first transient voltage suppression diode is connected to a reference voltage, a first terminal of the second snapback diode is connected to a source voltage that is a source voltage of a load, and a second terminal of the first transient voltage suppression diode is connected to a second terminal of the second snapback diode.

[0026] Described herein is a transient voltage suppression method and device in which a first conductive layer is disposed on a first side of the first transient voltage suppression diode.

[0027] Described herein is a transient voltage suppression method and device in which a second conductive layer is disposed on a first side of the second snapback diode.

[0028] A transient voltage suppression method and apparatus is described herein, where a first conductive layer is soldered to a first side of a first transient voltage suppression diode and a second conductive layer is soldered to a first side of a second snapback diode.

[0029] A transient voltage suppression method and apparatus is described herein, where a solder layer connects a second side of a first transient voltage suppression diode to a second side of a second snapback diode.

[0030] Figure 1 is a schematic diagram of an example electronic circuit 100 that includes transient voltage protection. Note that the electronic circuit 100 can be found in many devices that can experience potentially transient voltage surges that, if left unchecked, can cause damage to circuitry (i.e., a load). In one example, integrated circuits (ICs) can be protected by a transient voltage protection device from damaging voltage surges caused by overvoltage. These ICs can be used in any number of applications, such as computers, control units, and any other device that utilizes ICs that can experience damaging overvoltage.

[0031] As can be seen from Figure 1 , the electronic circuit 100 includes a load component (protected component) connected across a source voltage (indicated as positive (+) source and negative (-) source). A TVS diode is connected to the positive source similar to the protected load and to a reference voltage (e.g., ground). As described above, the TVS diode is connected in parallel to the load component. In this way, the voltage drop across the TVS diode is the same as the protected load. Thus, the TVS diode is operable to change the voltage across the protected load because the TVS diode experiences the same voltage.

[0032] Upon a transient voltage exceeding a threshold, the TVS diode shorts the positive terminal of the source to the reference voltage. Thus, the clamped transient current flows through the protected load. The excess transient current created by the overvoltage (i.e., transient voltage) flows through the TVS diode to the reference (e.g., ground).

[0033] Thus, the overvoltage does not cause damage to the protected load by subjecting the protected load to potentially damaging voltage surges from the overvoltage. This provides protection in a device containing the electronic circuit from overvoltage. In one example, as described above, the potentially damaging excess transient current caused by the overvoltage is prevented from flowing through the protected load. Instead, this excess transient current created by the overvoltage is routed away from the load while only allowing the clamped operating current to flow through the protected load.

[0034] The clamping of the TVS diode is explained in further detail below.

[0035] Figure 2is a graphical representation 200 of the operation of a TVS diode. From Figure 2 It can be seen from

[0036] That is, Figure 2 shows a current-voltage (I-V) curve of a TVS diode. The I-V curve shows the relationship between the voltage across the diode and the current. From Figure 2 It can be seen from T is the current at the breakdown voltage (V BR ), and I PP is the peak current at the clamping voltage (V C ). The breakdown voltage is the voltage at which the TVS diode operates (i.e., turns on) and begins to conduct current through itself. The clamping voltage is the voltage level at which the TVS diode clamps or otherwise limits the voltage across the protected load.

[0037] The TVS diode includes a clamping ratio equal to the clamping voltage (V C ) divided by the breakdown voltage (V BR ) of the diode. Thus, the clamping ratio can be calculated according to the following equation:

[0038] Clamping Ratio (CR) = V C / V BR It can be seen from Figure 2 The clamping ratio of a TVS diode is greater than 1 (i.e., CR > 1.0). By clamping the voltage at the clamping voltage, the TVS diode provides the advantage of overvoltage protection for the protected load. However, because the clamping voltage is higher than the breakdown voltage, the protected load can also be subjected to excess voltage.

[0039] Referring back to Figure 1 and Figure 2 , it can be desirable for the clamping ratio to be close to or at 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 clamping voltage V C . With a clamping ratio of 1.0 or substantially 1.0, the clamping voltage is close to the breakdown voltage of the TVS diode. This provides for clamping the voltage at the voltage at which the TVS diode turns on and provides a safe operating voltage level for the protected load.

[0040] Because the protected load is also connected in parallel to the TVS diode, the clamping voltage V Cis the voltage across the protected load. Thus, the transient surge current flows through the TVS diode to ground, while the clamped transient current flows through the protected load. In this way, the protected load is protected from the higher surge current flowing through it that would cause potential damage. At the same time, as a result of the clamped voltage flowing through the protected load, the protected load continues to operate by the clamped current.

[0041] The breakdown voltage (V BR ) of the TVS diode needs to be high enough to maintain normal operation of the protected load. Otherwise, the voltage needed for the protected load to operate will be clamped. In this case, the protected load will not be able to operate.

[0042] As shown in Figure 2 , the clamping voltage (V C ) of the TVS diode is higher than the breakdown voltage (V BR ) of the TVS diode. Thus, there is an amount of potential overvoltage that can occur across the protected load. In some cases, the protected load can be subjected to a voltage surge that is 10%, 20%, or more of the breakdown voltage. This level of voltage surge from the overvoltage can potentially be damaging because the protected load can not be rated to be exposed to this level of overvoltage.

[0043] Since some devices, such as advanced integrated circuit (IC) chips, can not be able to withstand a surge overvoltage that the TVS diode is not able to prevent, it can be beneficial to provide protection for voltages closer to the breakdown voltage. In this case, the surge voltage is limited to a safe level that allows the protected load to operate. For example, it can be desirable to have a clamping ratio as close to 1.0 as possible. As mentioned above, by having a clamping ratio as close to 1.0 as possible, protection is provided against potentially damaging overvoltages from voltage surges. In addition, the protected load continues to receive sufficient power to operate. To make the clamping ratio of the TVS device closer to 1.0, a kickback diode can be utilized in the protection circuit that is added to the TVS diode.

[0044] Figure 3 is a graphical representation 300 of the operation of the kickback diode. As can be seen from Figure 3 , the kickback diode exhibits different characteristics than the TVS diode plot shown in Figure 2 . For example, the clamping voltage is less than the breakdown voltage. Thus, for example, the clamping ratio of the kickback diode is less than 1 (i.e., CR<1.0).

[0045] Again referring back to Figure 1 , and by way of example only, the operation of the kickback diode can be described by replacing the TVS diode in Figure 1 with the kickback diode. The kickback diode clamps the overvoltage at V C and the protected load continues to operate at V BRoperates (i.e., turns on).

[0046] As Figure 3 shown, I T is the current at the breakdown voltage (V BR ) and I PP is the peak current at the clamping voltage (V C ). The breakdown voltage is the voltage at which the kickback diode operates (i.e., turns on) and begins to conduct current through itself. The clamping voltage is the voltage level at which the kickback diode clamps or otherwise limits the voltage across the protected load.

[0047] As Figure 3 can be seen, the clamping voltage (V C ) is less than the breakdown voltage (V BR ). In this case, the clamping ratio (CR) can be shown to be less than 1.0. Thus, the clamping voltage (V C ) is less than the normal operating voltage of the protected load.

[0048] While the above can provide protection for the protected device, the clamping voltage being less than the breakdown voltage (V BR ) can result in the kickback diode not being able to turn off once turned on, as the voltage drop across the kickback diode can remain less than the voltage drop across the protected load. In this case, if the clamping voltage across the kickback diode remains below the required operating voltage of the protected load, then no current will flow through the protected load.

[0049] That is, the clamping voltage (V C ) being less than the breakdown voltage will not allow the kickback diode to turn off once turned on. This will prevent the required power from being received by the protected load.

[0050] However, to overcome the shortcomings of the TVS diode, the kickback diode can be arranged in electrical series with the TVS diode across the source voltage, for example, as shown in Figure 1 That is, the TVS diode, as shown in Figure 1 , can be a combination TVS diode having the performance shown in Figure 2 , electrically connected in series with the kickback diode, and the two diodes are connected in parallel as a whole to the protected load. In this arrangement, a clamping ratio of 1.0 or very close to 1.0 can be achieved, providing more effective protection for the protected device. For example, the two diodes (regular TVS diode and kickback diode) are combined into a single device.

[0051] Thus, the protection scheme of connecting a conventional TVS diode in series with a snapback diode takes advantage of the characteristics of each type of diode. That is, the conventional TVS diode having a clamping ratio greater than 1.0, when combined in series with the snapback diode having a clamping ratio less than 1.0, together achieve a clamping ratio of substantially 1.0, thereby allowing for more effective protection of the protected load, while also allowing the protected load to maintain operation.

[0052] Figure 4 is a schematic diagram of a TVS protection device 400 (e.g., a surface mount TVS clamp diode including a series connection of a conventional TVS diode and a snapback diode) according to example embodiments. As shown, a first terminal of a first diode 401 (e.g., a conventional TVS diode) is connected to an electrode designated as electrode 1. Electrode 1 can be connected to Figure 4 the positive source terminal as shown. Figure 1

[0053] A first terminal of a second diode 402 (e.g., a snapback diode) is connected to a second terminal of diode 401. A second terminal of second diode 402 can be connected to a second electrode (designated as electrode 2). Electrode 2 can then be connected to Figure 1 the reference terminal as shown.

[0054] Thus, in the circuit shown in Figure 4 , current flows from electrode 1 to electrode 2 through diode 401 and diode 402. That is, diode 401 and diode 402 are connected in series with respect to electrodes 1 and 2.

[0055] Thus, if 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 will flow from the positive terminal to the reference terminal through both diode 401 and 402, in parallel with the protected load shown in Figure 1 . In this way, the diode pair of diode 401 and diode 402 acts as a transient voltage suppression circuit that protects the protected load in Figure 1 .

[0056] As previously described, by connecting the entire TVS protection device 400 in parallel with the protected load, the TVS protection device 400 is subjected to the same voltage level as the protected load. In this case, the TVS protection device 400 operates based on the overvoltage that will be across the protected load in order to turn it on.

[0057] ​It should be noted that although in the example embodiment, the TVS diode is depicted as diode 401 and the kickback diode is depicted as diode 402, the diodes can be connected in series in any order. That is, diode 401 can be the kickback diode and diode 402 can be the TVS diode. Additionally, the physical arrangement of diodes 401 and 402 can be provided in different forms.

[0058] The arrangement of diodes 401 and 402 includes a clamping ratio that is close to or equal to 1.0 (i.e., CR = 1.0). Having a clamping ratio of substantially 1.0 provides more effective protection to the protected load as compared to a clamping ratio that is greater than 1.0 or less than 1.0.

[0059] Figure 5 is a block diagram of a stacked TVS protection device 500 in accordance with an example embodiment. That is, in Figure 5 , the diode pair of diode 401 and diode 402 are physically arranged one on top of the other in a chip package.

[0060] Referring to Figure 4 and Figure 5 , electrode 1 is shown connected to a first side and terminal of a regular TVS chip (e.g., diode 401). The first side and terminal can be a bottom side of diode 401. Electrode 2 is shown connected to a first side of a kickback diode chip (e.g., diode 402). In this example, the first side and terminal of the kickback diode chip can be a top side of diode 402.

[0061] A second side of diode 401 is then connected to a second side of diode 402. In Figure 5 the example shown, the second side of diode 401 can be a top side of diode 401 and the second side of diode 402 can be a bottom side of diode 402.

[0062] In the above manner, a series circuit is formed between electrode 1, diode 401, diode 402, and electrode 2. Referring again to Figure 1 , 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 of the circuit shown in Figure 1 . Thus, the series circuit formed between electrode 1 and electrode 2 operates in parallel with the protected load shown in Figure 1

[0063] By connecting diode 401 and diode 402 in series, the pair is subjected to the same voltage as the protected load in order to protect it. Moreover, due to the series connection of diodes 401 and 402, the same current will flow through the pair of diodes 401 and 402.

[0064] ​Figure 6A Example components of a stacked TVS protection device 600 are shown in accordance with example embodiments. For example, Figure 6A Example components of a stacked TVS protection device 600 are shown in accordance with example embodiments. For example, Figure 5 Example configurations and structural components of the diodes shown in FIG. 4B. A first conductive layer (e.g., a copper slug) 404 can be soldered 406 to the flyback diode chip 402 on a first side of the flyback diode chip 402.

[0065] A second conductive layer 405 (e.g., another copper slug) can be soldered 406 to a first side of the regular TVS chip 401. An additional solder layer 406 can be provided between the regular TVS chip 401 and the flyback diode chip 402 to connect a second side of the regular TVS chip 401 and a second side of the flyback diode chip 402. Again, it should be noted that the order of the chips can be varied. That is, while the regular TVS chip 401 is shown on the bottom side of the assembly and the flyback diode chip 402 is shown on the top side, the two chips can be swapped.

[0066] Figure 6B Example components of a stacked TVS protection device 601 are shown in accordance with alternative example embodiments. As Figure 6B shown, no first conductive layer 404, second conductive layer 405, and solder layer 406 connecting them to their respective chips 401 and 402 are provided.

[0067] Further, as noted above, the physical arrangement of the regular TVS chip 401 and the flyback diode chip 402 can be varied. For example, the regular TVS chip 401 and the flyback diode chip 402 can be physically arranged side-by-side, rather than one stacked on top of the other.

[0068] Figure 7 is a plan view of a side-by-side arrangement 700 of TVS protection devices in accordance with example embodiments. In this arrangement, the regular TVS chip 401 and the flyback diode chip 402 are arranged side-by-side. Additionally, electrode 1 is shown connected to a first terminal of the flyback diode chip 402, while electrode 2 is shown connected to a first terminal of the regular TVS chip 401. The second terminals of the regular TVS chip 401 and the flyback diode chip 402 are connected together, similar to Figure 5 .

[0069] In this arrangement, electrode 1 can be connected to the positive terminal of the circuit shown in Figure 1 , while electrode 2 can be connected to the reference terminal shown in Figure 1 . Again, this forms a series circuit from electrode 1 through the regular TVS chip 401 and the flyback diode chip 402 to electrode 2.

[0070] Again, as noted above, the examples shown refer to electrode 1 being connected toFigure 1 the positive terminal of the circuit shown in Figure 1 and electrode 2 is connected to the reference terminal of the circuit shown in Figure 1 However, it should be noted that in an alternative arrangement, 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 of the circuit shown in

[0071] Thus, similar to the arrangement shown in Figure 5 the circuit formed between electrode 1 and electrode 2 by diodes 401 and 402 is a series circuit. Furthermore, for example, the series circuit formed from electrode 1 to electrode 2 operates in parallel with the circuit through the protected load in Figure 1

[0072] It will be appreciated that based on the disclosure herein, many variations are possible. Although features and elements are described above in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements.​

Claims

1. A method for circuit protection comprising: providing a first transient voltage suppression diode having a first clamping characteristic; and providing a second snapback diode having a second clamping characteristic in series with the first transient voltage suppression diode, wherein the first transient voltage suppression diode and the second snapback diode are electrically connected in parallel to a load.

2. The method of claim 1, wherein, The first transient voltage suppression diode has a voltage clamping ratio greater than 1.

0.

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

4. The method of claim 1, wherein, The second snapback diode has a voltage clamping ratio less than 1.

0.

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

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

0.

7. The method of claim 1, wherein, A first terminal of the first transient voltage suppression diode is connected to a reference voltage, a first terminal of the second snapback diode is connected to a source voltage that is a source voltage of the load, and a second terminal of the first transient voltage suppression diode is connected to a second terminal of the second snapback diode.

8. A transient voltage suppression device comprising: 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, wherein the first transient voltage suppression diode and the snapback diode are electrically connected in parallel to a load.

9. The apparatus of claim 8, wherein, The first transient voltage suppression diode has a voltage clamping ratio greater than 1.

0.

10. The apparatus of claim 9, wherein, The clamping voltage of the first transient voltage suppression diode is higher than the breakdown voltage of the first transient voltage suppression diode.

11. The apparatus of claim 8, wherein, The second snapback diode has a voltage clamping ratio less than 1.

0.

12. The apparatus of claim 11, wherein, The clamping voltage of the second snapback diode is less than the breakdown voltage of the second transient voltage suppression diode.

13. The apparatus of claim 8, wherein, The clamping ratio of the first transient voltage suppression diode and the second snapback diode connected in series is substantially 1.

0.

14. The apparatus of claim 8, wherein, A first terminal of the first transient voltage suppression diode is connected to a reference voltage, a first terminal of the second snapback diode is connected to a source voltage that is a source voltage of the load, and a second terminal of the first transient voltage suppression diode is connected to a second terminal of the second snapback diode.

15. The apparatus of claim 14, wherein, The first transient voltage suppression diode is physically arranged above the second snapback diode.

16. The apparatus of claim 15, wherein, The first transient voltage suppression diode is physically arranged adjacent to the second snapback diode.

17. A transient voltage suppression device comprising: 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.

18. The device of claim 17, further comprising a first conductive layer disposed on a first side of the first transient voltage suppression diode.

19. The apparatus of claim 18, further comprising a second conductive layer disposed on a first side of the second flyback diode.

20. The apparatus of 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 flyback diode.

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