Patent Description:
Power over Coaxia (PoC) technique may be widely used in data signal (e.g., a network signal, a video signal, an image signal, an audio signal) and power signal transmission. In a PoC system, a power supply equipment and a powered device may exchange a data signal and a power signal via a coaxial cable. An electrical surge may sometimes occur between the power supply equipment and the powered device. The electrical surge refers to a transient overvoltage of an electric device that exceeds a steady value, which degrades wiring insulation and destroys the electronic device. The electrical surge may be generated by an internal cause (e.g., a start, a stop, or a malfunction of the electronic device), and/or an external cause (e.g., a lightning strike). Thus, it is desirable to provide an electrical surge protection circuit for the PoC system, thereby avoiding the electrical surge being damaged by the electrical surge. an example of prior art can be found in <CIT> and in <CIT>.

The present invention is defined by the attached independent claims. Other preferred embodiments may be found in the dependent claims. The present application discloses a circuit, comprising:a coaxial cable interface (J);a data module (<NUM>) configured to receive or output a data signal;a power module (<NUM>) configured to receive or output a power signal;a power signal transmission branch electrically coupled between the coaxial cable interface and the power module, wherein the power signal transmission branch includes an inductor (L) that allows the power signal to pass; and a data signal transmission branch electrically coupled between the coaxial cable interface (J) and the data module (<NUM>), wherein the data signal transmission branch includes a capacitor (C3) that allows the data signal to pass, a resistor (R1), a first electrical surge protection circuit (<NUM>) configured to release a surge current on the data signal transmission branch, and a second electrical surge protection circuit (<NUM>), and the first electrical surge protection circuit (<NUM>) includes a first protection device and a gas discharge tube (GDT) that are connected in series;a common branch electrically coupled between the coaxial cable interface (J) and a connection node (<NUM>) between the power signal transmission branch and the data signal transmission branch; anda fourth electrical surge protection circuit (<NUM>) configured to release an electrical surge on the common branch, one end of the fourth electrical surge protection circuit (<NUM>) being coupled to the common branch, and another end being coupled to the ground, wherein the data module (<NUM>) is coupled to the coaxial cable interface (J) via the second electrical surge protection circuit (<NUM>), the resistor (R1), the first electrical surge protection circuit (<NUM>), and the capacitor (C3) sequentially.

In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant disclosure. However, it should be apparent to those skilled in the art that the present disclosure may be practiced without such details. In other instances, well-known methods, procedures, systems, components, and/or circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present disclosure. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present disclosure is not limited to the embodiments shown, but to be accorded the widest scope consistent with the claims.

It will be understood that the term "system," "engine," "unit," "module," and/or "block" used herein are one method to distinguish different components, elements, parts, section or assembly of different level in ascending order. However, the terms may be displaced by other expression if they may achieve the same purpose.

It will be understood that when a unit, engine, module, or block is referred to as being "on," "connected to," or "coupled to" another unit, engine, module, or block, it may be directly on, connected or coupled to, or communicate with the other unit, engine, module, or block, or an intervening unit, engine, module, or block may be present, unless the context clearly indicates otherwise.

The terminology used herein is for the purposes of describing particular examples and embodiments only and is not intended to be limiting. It will be further understood that the terms "include" and/or "comprise," when used in this disclosure, specify the presence of integers, devices, behaviors, stated features, steps, elements, operations, and/or components, but do not exclude the presence or addition of one or more other integers, devices, behaviors, features, steps, elements, operations, components, and/or groups thereof.

An aspect of the present disclosure relates to a circuit. The circuit may include a coaxial cable interface, a data module, a power module, a power signal transmission branch, and a data signal transmission. The data module may be configured to receive or output a data signal. The power module may be configured to receive or output a power signal. The power signal transimission branch may be electrically coupled between the coaxial cable interface and the power module, and include an inductor that allows the power signal to pass. The data signal transmission branch may be electrically coupled between the coaxial cable interface and the data module. The data signal transmission branch may include a capacitor that allows the data signal to pass and a first electrical surge protection circuit configured to release a surge current on the data signal transmission branch.

According to some embodiments, a fourth electrical surge protection circuit may be coupled to a common branch, which is coupled between the coaxial cable interface and a connection node between the power signal transmission branch and the data signal transmission branch. Similar to the function of the first electrical surge protection circuit, the fourth electrical may be configured to release an electrical surge on the common branch. According to some embodiments, the data signal transmission branch may further include a second electrical surge protection circuit configured to release a residual electrical surge after the electrical surge releasing performed by the fourth electrical surge protection circuit and/or the first electrical surge protection circuit. The data module may be coupled to the coaxial cable via the second electrical surge protection circuit, the first electrical surge protection circuit and the capacitor sequentially, thereby protecting the data module from an electrical surge more reliably. According to some embodiments, the power signal transmission branch may include a third electrical surge protection circuit coupled between the coaxial cable interface and the power module. The third surge protection circuit may be configured to release an electrical surge received from the connection node, thereby protecting the power module from an electrical surge more reliably. In some conditions, one or more (e.g., the third and/or fourth electrical surge protection circuits) of the abovementioned electrical surge protection circuits may include a GDT or a rectifier bridge that is connected sequentially to a protection device of the corresponding electrical surge protection circuit, which reduces a parasitic capacitance in the corresponding electrical surge protection circuit, thereby reducing an affect of the parasitic capacitance on the data signal.

<FIG> illustrates a schematic diagram of an exemplary Power over Coaxial (PoC) system <NUM> according to some embodiments of the present disclosure. The PoC system <NUM> may use a single coxial cable to transmit both of the power signal and the data signal, which reduces the wiring cost and improves the convenience and security for installing the components of the PoC system <NUM>. As used herein, the power signal may include a direct current (DC) signal. The data signal may include one or more alternating current (AC) signals (e.g., a network signal, a video signal, an image signal, an audio signal). As shown in <FIG>, the PoC system <NUM> may include a power sourcing equipment (PSE) <NUM>, a powered device (PD) <NUM>, and a coaxial cable <NUM>. The PSE <NUM> may be electrically coupled to the PD <NUM> via the coaxial cable <NUM>. The coaxial cable <NUM> may be coupled to the PSE <NUM> via a connection node A, and coupled to the PD <NUM> via a connection node B.

The PSE <NUM> may be configured to supply electric power to the PD <NUM>. In some embodiments, the PSE <NUM> may be used to manage a power supply process in the PoC system <NUM>. The PSE <NUM> may have a similar function as a network switch (e.g., a Power over Ethernet (PoE) network switch) that supplies power to powered devices. In some embodiments, the PES <NUM> may be also used to obtain and process the data signal from the PD <NUM>. For example, the PSE <NUM> may include a digital video recorder that receives the video signal from the PD <NUM> and performs a video processing operation on the video signal.

As shown in <FIG>, the PSE <NUM> may include a power module <NUM>, a data signal blocking circuit <NUM>, a power signal blocking circuit <NUM>, and a data module <NUM>. The power module <NUM> may be configured to provide a power signal for the PoC system <NUM> or a component (e.g., the PSE <NUM>, the PD <NUM>) thereof. The power module <NUM> may include a power source or a power adapter coupled to an external power source. The data signal blocking circuit <NUM> and the power signal blocking circuit <NUM> may be used to separate the power signal and the data signal, respectively. For example, the data signal blocking circuit <NUM> may allow the power signal to pass through while block the data signal, such that no data signal may reach at the power module <NUM>. In some embodiments, the power signal may be a DC signal and the data signal may be an AC signal. The data signal blocking circuit <NUM> may include an inductor (e.g., an inductor L shown in <FIG>), which presents low impedance to a DC signal, and high impedance to an AC signal. Thus, the data signal blocking circuit <NUM> may allow the power signal to pass and block the AC signal (e.g., the data signal). As another example, the power signal blocking circuit <NUM> may allow the data signal to pass through while block the power signal, such that no power signal may reach at the data module <NUM>. The power signal blocking circuit <NUM> may include a capacitor C1, which presents low impedance to an AC signal, and high impedance to an DC signal. Thus, the power signal blocking circuit <NUM> may allow the data signal to pass and block the DC signal (e.g., the power signal). As shown in <FIG>, the left end of the capacitor C1 may be coupled to the data module <NUM>, and the right end of the capacitor C1 may be coupled to the connection node A. The data module <NUM> may be configured to process the data signal, which is received from the PD <NUM> and passed by the power signal blocking circuit <NUM>. For example, the data module <NUM> may store a video signal obtained from the PD <NUM>. As another example, the data module <NUM> may perform a video processing operation (e.g., a lowpass filtering, a video compensation) on the video signal. In some embodiments, the power module <NUM> and the data module <NUM> may be integrated into one module.

The PD <NUM> may be a device that is powered to realize certain functions, e.g., implementing the video surveillance. For example, the PD <NUM> may be powered by the PSE <NUM> by receiving the power signal via the coaxial cable <NUM>, or the PD <NUM> may be powered by an external power source (not shown in <FIG>) via other cables. The PD <NUM> may be a terminal device of the PoC system <NUM> that may generate the data signal and transmit the data signal to the PSE <NUM> for further processing. In some embodiments, the PD <NUM> may be a PoC device that supports a PoC technique or a non-PoC device which does not support the PoC technique. The PoC technique may refer to an operation of exchanging both of the power signal and the data singla between two devices via a coaxial cable. In some embodiments, the PD <NUM> may include an IP phone, a notebook computer, an IP camera, a Wireless Local Area Network access point (not shown in <FIG>), or the like, or a combination thereof.

As shown in <FIG>, the PD <NUM> may include a power receiving module <NUM>, a data signal blocking circuit <NUM>, a power signal blocking circuit <NUM>, and a data module <NUM>. The power receiving module <NUM> may receive the power signal via the coaxial cable <NUM> and the data signal blocking circuit <NUM>, as indicated by the dashed-dotted arrowed line indicative of a power signal transmission direction, and power on the data module <NUM>. The data signal blocking circuit <NUM> may have a similar function and/or configuration with that of the data signal blocking circuit <NUM>. For example, the data signal blocking circuit <NUM> may allow the power signal to pass through and block the data signal, such that no data signal may reach the power receiving module <NUM> via the data signal blocking circuit <NUM>. The power signal blocking circuit <NUM> may have a similar function and/or configuration with that of the power signal blocking circuit <NUM>. For example, the power signal blocking circuit <NUM> may allow the data signal to pass through and block the power signal, such that no power signal may reach the data module <NUM>. As shown in <FIG>, the power signal blocking circuit <NUM> may include a capacitor C2. The data module <NUM> may be configured to generate the data signal or receive the data signal from a signal source. The data module <NUM> or the signal source may include an image sensor, a video sensor, an audio sensor, or the like. For example, the video sensor may be part of a video surveillance system and generate a video signal corresponding to a specific scene. The data module <NUM> may transmit the data signal to the PSE <NUM> via the power signal blocking circuit <NUM> and the coaxial cable <NUM>, as indicated by the dashed-dotted arrowed line indicative of a data signal transmission direction. In some embodiments, the power receiving module <NUM> and the data module <NUM> may be two components integrated into the PD <NUM> (e.g., a camera). Alternatively or additionally, the power receiving module <NUM> and the data module <NUM> may be independent devices that are connected with each other. For example, the data module <NUM> may be a camera that includes a port for connecting with the power receiving module <NUM>.

The coaxial cable <NUM> may be configured to exchange the power signal and/or the data signal between the PSE <NUM> and the PD <NUM>. As shown in <FIG>, according to the dashed-dotted arrowed line indicative of the power signal transmission direction, the power signal may be transmitted from the power module <NUM>, via the data signal blocking circuit <NUM>, the node A, the coaxial cable <NUM>, the node B, and the data signal blocking circuit <NUM> sequentially, and received by the power receiving module <NUM>. According to the dashed-dotted arrowed line indicative of the data signal transmission direction, the data signal may be outputted by the data module <NUM>, via the power signal blocking circuit <NUM>, the node B, the coaxial cable <NUM>, the node A, and the power signal blocking circuit <NUM> sequentially, and received by the data module <NUM>. The coaxial cable <NUM> may be an RG-<NUM> coaxial cable, a <NUM>-<NUM> coaxial cable, an RG-<NUM> coaxial cable, an RG-<NUM> coaxial cable, an RG-<NUM> coaxial cable, an RG-<NUM> coaxial cable, an RG-<NUM> coaxial cable, or the like, or a combination thereof.

It should be noted that the above description of the PoC system <NUM> is intended to be illustrative, and not to limit the scope of the present disclosure. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments. For example, the PoC system <NUM> may include one or more additional components. Additionally or alternatively, one or more components of the PoC system <NUM> described above may be omitted. As another example, two or more components of the PoC system <NUM> may be integrated into a single component.

<FIG> illustrates schematic diagrams of exemplary electrical surge protection circuits according to some embodiments of the present disclosure. As used herein, an electrical surge refers to a transient transition in voltage, current, or transferred energy in an electric device that exceeds a steady value. The electrical surge may include a surge voltage and a surge current. A surge voltage refers to an overvoltage spike applied on the electrical device that exceeds a normal operation voltage of the electric device. A surge current refers to an overcurrent spike drawn by the electrical device that exceeds a normal operation current of the electric device. In essence, the electrical surge may be a violent pulse that occurs in just a few millionths of a second, which is possibly caused by a heavy equipment, a short circuit, a power switching, a large engine, and lightning induced energy. In such cases, an electrical surge protection circuit may be introduced to protect the PoC system (e.g., the PoC system <NUM>) from being damaged by the electrical surge. For illustration purposes, the electrical surge protection circuits <NUM>-<NUM> hereinafter are illustrated to protect the PSE <NUM> from the electrical surge. In some alternative embodiments, it shall be noted that the electrical surge protection circuits <NUM>-<NUM> may also be integrated into a powered device (e.g., the PD <NUM>) to protect the powered device from the electrical surge in a similar manner, which is not to be repeated in the disclosure.

<FIG> illustrates a schematic diagram of an exemplary electrical surge protection circuit <NUM> according to some embodiments of the present disclosure. The electrical surge protection circuit <NUM> may include a coaxial cable interface J, a data signal transmission branch, a power signal transmission branch, and a common branch. The data signal transmission branch may be electrically coupled between the coaxial cable interface J and the data module <NUM>. As shown in <FIG>, the data signal transmission branch includes a capacitor C3, an electrical surge protection circuit <NUM> (also referred as to a first electrical surge protection circuit), a resistor R1, and an electrical surge protection circuit <NUM> (also referred as to a second electrical surge protection circuit). The power signal transmission branch may be electrically coupled between the coaxial cable interface J and the power module <NUM>. As shown in <FIG>, the power signal transmission branch includes an inductor L and an electrical surge protection circuit <NUM> (also referred as to a third electrical surge protection circuit). The common branch may be electrically coupled between the coaxial cable interface J and a connection node O between the power signal transmission branch and the data signal transmission branch. That is to say, the coaxial cable interface J is coupled to the data module <NUM> via the common branch and the data signal transmission branch, and coupled to the power module <NUM> via the common branch and the power signal transmission branch.

The coaxial cable interface J may be configured to receive a coaxial cable of a PoC system (e.g., the coaxial cable <NUM> of the PoC system <NUM> in <FIG>). The coaxial cable interface J may be coupled between the PSE <NUM> and a powered device (e.g., PD <NUM>). Via the coaxial interface J, the power signal may be transmitted from the common branch to the powered device, and the data signal generated by the powered device may be transmitted to the common branch for further transmission.

The data signal transmission branch may be configured to transmit the data signal from the common branch to the data module <NUM>. In the data signal transmission branch, the data module <NUM> may be coupled to the coaxial cable interface J via the electrical surge protection circuit <NUM>, the resistor R1, the electrical surge protection circuit <NUM>, and the capacitor C3 sequentially. One end of the electrical surge protection circuit <NUM> may be coupled to the capacitor C3, and another end of the electrical surge protection circuit <NUM> may be coupled to the ground. One end of the electrical surge protection circuit <NUM> may be coupled to the resistor R1, and another end of the electrical surge protection circuit <NUM> may be coupled to the ground.

The capacitor C3 may be configured to allow the data signal to pass and block the power signal (i.e., an AC coupling), such that no power signal in the DC form may reach the data signal transmission branch. In some embodiments, the capacitor C3 may have a relatively large capacitance, e.g., <NUM> microfarads (µF). Since a capacitor with large capacitance presents a low impedanceto a surge current, the surge current may pass through the capacitor C3 easily. Thus, the electrical surge protection circuit <NUM> set between the capacitor C3 and the data module <NUM> may be configured to release the surge current. In some embodiments, when an electrical surge comes in the common branch of the electrical surge protection circuit <NUM> via the coaxial cable interface J, most of the electrical surge may pass through the capacitor C3, and be released at least partially by the electrical surge protection circuit <NUM>. Thus, due to the electrical surge released by the electrical surge protection circuit <NUM>, a voltage on the common branch may be smaller than a threshold. In some embodiments, the electrical surge coming in the electrical surge protection circuit <NUM> via the coaxial cable interface J may include the electrical surge flowing to the data signal transmission branch (also referred to as first electrical surge) and an electrical surge flowing to the power signal transmission branch (also referred to as third electrical surge). Since a majority of the electrical surge on the common branch flows to the data signal transmission branch due to the large-capacitance capacitor C3, the third electrical surge may be relatively small, thus protecting the power signal transmission branch to some extent. In some embodiments, if the first electrical surge is of a low surge voltage, the electrical surge protection circuit <NUM> may reduce the surge voltage to a desirable level, thereby protecting a subsequent branch of the data signal transmission branch after the electrical surge protection circuit <NUM> from a damage brought by the first electrical surge.

The resistor R1 may be configured to perform an impedance matching between a data module of the powered device (e.g., the data module <NUM> of the PD <NUM>) and the data module <NUM>, so as to maximize a power transfer from the powered device to the data module <NUM>. The resistor R1 may be further configured to control a voltage applied on a subsequent path of the data signal transmission branch after the resistor R1. The electrical surge protection circuit <NUM> may be configured to release a second electrical surge remained after an electrical surge releasing performed by the electrical surge protection circuit <NUM>. In some embodimetns, the second electrical surge may also be referred as a residual electrical surge. In some embodiments, a clamping voltage of the electrical surge protection circuit <NUM> may be set to be greater than a clamping voltage of the electrical surge protection circuit <NUM>. An operation voltage of an electrical surge protection device (e.g., a gas discharge tube (GDT), a transient voltage suppressor (TVS), a thyristor surge suppressor (TSS), a varistor) refers to a voltage that causes the electrical surge protection device to start to short or clamp. A clamping voltage of the electrical surge protection device (or an electrical surge protection circuit including the electrical surge protection device) refers to a certain voltage that the electrical surge protection device is limited to, after the electrical surge protection device has shorted or clamped. At the clamping voltage, the electrical surge protection device may pass a relatively large current flow. The clamping voltage of the electrical surge protection device may be greater than the operation voltage thereof. A working voltage of the electrical surge protection device refers to a voltage at which the electrical surge protection device is designed to work. The working voltage of the electrical surge protection device is always smaller than the operation voltage thereof. At a voltage equal to or smaller than the working voltage, the electrical surge protection device may be kept from shorting. In some embodiments, the electrical surge protection device for protecting a circuit from the electrical surge may have an working voltage that has a correlation (e.g., a linear correlation) with a working voltage of the protected circuit. For example, the working voltage of the electrical surge protection device may be substantially equal to a product of the working voltage of the protected circuit and a suitable value (e.g., <NUM>, <NUM>). The suitable value may be estimated based on experience. In some embodiments, the working voltage of the electrical surge protection device may include a breakdown voltage (also referred to as a DC spark-over voltage) of the GDT, an off-state voltage (also referred to as a stand-off voltage) of the TVS or the TSS, an allowable voltage of the varistor, or the like. Since the electrical surge protection circuit <NUM> may release most of the electrical surge on the data signal transmission branch, the power consumption of the electrical surge protection circuit <NUM> may be greater than the power consumption of the electrical surge protection circuit <NUM>.

The power signal transmission branch may be configured to transmit the power signal from the power module <NUM> to the common branch for powering the powered device, or to the data signal transmission branch for powering the data module <NUM>. In the power signal transmission branch, the power module <NUM> may be coupled to the coaxial cable interface J via the electrical surge protection circuit <NUM> and the inductor L sequentially. One end of the electrical surge protection circuit <NUM> may be coupled the inductor L, and another end of the electrical surge protection circuit <NUM> may be coupled to the ground. The inductor L may be configured to allow the power signal in the DC form to pass and block the data signal, thus preventing an undesired coupling caused by the electrical surge coming from the common branch. In some embodiments, the inductor L may be a hundred-microhenry (µH) level inductor. The electrical surge protection circuit <NUM> may be configured to release the third electrical surge, so as to protect the power module <NUM> from a damage caused by the third electrical surge.

The common branch may be configured to transmit the data signal received via the coaxial cable interface J to the data signal transmission branch, and transmit the power signal received from the power signal transmission branch to the coaxial interface J. That is, a signal on the common branch may be a combination of the power signal and the data signal (e.g., a high defination video signal).

<FIG> illustrates a schematic diagram of another exemplary electrical surge protection circuit <NUM> according to some embodiments of the present disclosure. The electrical surge protection circuit <NUM> may be an exemplary embodiment of the electrical surge protection circuit <NUM> as described in connection with <FIG>. As shown in <FIG>, the electrical surge protection circuit <NUM> may include a first protection device, wherein one end of the first protection device is coupled to the capacitor C3, and another end of the first protection device is coupled to the ground. The electrical surge protection circuit <NUM> may include a second protection device, one end of the second electrical surge protection circuit is coupled to the resistor R1, and another end of the second electrical surge protection circuit is coupled to the ground. The electrical surge protection circuit <NUM> may include a third protection device and a rectifier that are connected in series, wherein one end of the third protection devic is coupled to the inductor L, and another end of the third protection device is coupled to a rectifier bridge D1.

In some embodiments, the first protection device may include a gas discharge tube (GDT), a transient voltage suppressor (TVS) (e.g., an unidirectional TVS), a thyristor surge suppressor (TSS, also referred to as a voltage switched transient voltage suppressor), a varistor, or the like, or any combination thereof. For example, if the first protection device includes or is the GDT, the GDT may create a short circuit to release the first electrical surge, once triggered by the first electrical surge. The GDT may continue conducting (called a follow-on current) until all electric current on the data transmission branch sufficiently diminishes and the gas discharge quenches. Since the first protection device is coupled to the data signal transmission branch that filers out the power signal, the GDT may be protected from the follw-on current remained after the first electrical surge has been released by the GDT, which may destroy the GDT (e.g., causing the GDT to overheat). As another example, if the first protection device includes or is the TVS, a resistance between two ends of the TVS may be changed from high to low extremely quickly to release the first electrical surge, once the TVS is subjected to the first electrical surge. The TVS may have a high electrical surge absorbing capacility. In some embodiments, the parasitic capacitance of the first protection device may need to satisfy a certain condition, and a power of the first electrical surge may be smaller than a maximum power that the first protection device is able to release. Since the parasitic capacitance may damage a high-frequency data signal, the smaller the capacitance of the first protection device is, the better the data transmission branch may be. Merely by way of example, the certain condition for the parasitic capacitance of the first protection device may include that the parasitic capacitance of the first protection device is smaller than a certain value. In some embodiments, the GDT usually has a small parasitic capacitance (for example, smaller than <NUM> picofarad (pF)). If the first protection device includes the GDT, the first protection device may be regarded as satisfying the certain condition. In some embodiments, the parasitic capacitance of the TVS or TSS has a positive correlation with a current flow capacity, that is, the greater electrical surge current the TVS or the TSS is able to release, the greater the parasitic capacitance of the TVS or TSS may be. If the first protection device includes the TVS or TSS, the parasitic capacitance of the first protection device may need to be smaller than the certain value (e.g., 10pF), and the power of the first protection device may need to be greater than the power of the first electrical surge. In some embodiments, the working voltage of the first protection device may need to be greater than a voltage of the data signal transmitted on the data signal transmission branch, to ensure that the first protection device does not short due to a voltage fluctuation of the data signal within its normal voltage range. In this way, an electrical surge protection device may be selected from one or more electrical surge protection devices as the first protection device, by comparing the voltage of the data signal with working voltage levels of one or more electrical surge protection devices. As described above, there may be a correlation between a value of the working voltage of the electrical surge protection device and a value of the working voltage of the protected circuit. In some embodiments, an electrical surge protection device may be selected from one or more electrical surge protection devices as the first protection device, by determining a product of the voltage of the data signal and a suitable value, and comparing the determined product with the working voltage levels of one or more electrical surge protection devices. For example, the working voltage of the first protection device may be a smallest working voltage level of its type (e.g., the abovementioned GDT, TSS, TVS) that is greater than a product of the voltage of the data signal and the suitable value, since an electrical surge protection with a smaller working voltage level has a better electrical surge releasing performace. For illustration, the voltage of the data signal transmitted on the data signal transmission branch is equal to <NUM> volts (V) hereinafter. In some embodiments, the first protection device may be a GDT with a breakdown voltage equal to <NUM> V and a capacitance smaller than <NUM> pF. In some embodiments, the first protection device may be a TSS with an off-state voltage equal to 6V and a capacitance smaller than <NUM> pF. In some embodiments, the first protection device may be a TVS with an off-state voltage equal to 5V and a capacitance smaller than <NUM> pF, or the like. As shown in <FIG>, the first protection device is a GDT1.

In some embodiments, the second protection device may include a TVS, e.g., a TVS1 in <FIG>. Similar to the first protection device, a working voltage of the second protection device may need to be greater than the voltage of the data signal transmitted on the data signal transmission branch. Also, a parasitic capacitance of the TVS1 may be smaller than a certain value (e.g., 10pF). Since the second protection device is used to release the electrical surge remained after the electrical surge releasing of the first protection device, the second protection device may have a lower power consumption than that of the first protection device, and the working voltage of the second protection device may be smaller than that of the first protection device to achieve a better electrical surge releasing performace. For example, the TVS1 may have an off-state voltage equal to the voltage of the data signal (i.e., <NUM>. 3V) and a capacitance smaller than 1pF.

In some embodiments, the third protection device may include a TVS, e.g., a TVS2 in <FIG>. In some embodiments, a working voltage of the third protection device may be greater than a voltage of the power signal transmitted on the power signal transmission branch. Optionally, a difference between the working voltage of the third protection device and the voltage of the power signal may be as small as possible. For illustration, the voltage of the power signal transmitted on the power signal transmission branch is equal to 48V hereinafter. In some embodiments, an off-state voltage of the TVS2 may be equal to 58V. Referring back to <FIG>, a POC line may include the common branch, a line between the capacitor C1 and the connection node A, a line between the data signal blocking circuit <NUM> and the connection node A, a line between the capacitor C2 and the connection node B, a line between the data signal blocking circuit <NUM> and the connection node B. Since the third electrical surge protection circuit <NUM> is close to the POC line,a first data signal (e.g., a high-frequency data signal thereof) transmitted on the POC line may be attenuated by the parasitic capacitance of the electrical surge protection circuit <NUM>. Thus, a second data signal received by the data module <NUM> via the data signal transmission branch may be different from the first data signal. To improve the quality of the second data signal, the parasitic capacitance of the electrical surge protection circuit <NUM> may need to be decreased. To this end, the TVS2 may be coupled to the rectifier bridge D1 that has a capacitance smaller than that of the TVS2, which reduces the parasitic capacitance in the electrical surge protection circuit <NUM> to be smaller than the capacitance of the rectifier bridge D1. The rectifier bridge may include a full-bridge rectifier and a half-bridge rectifier, which reduces the parasitic capacitance in the electrical surge protection circuit <NUM> and has a desirable current flow capacity. For example, as shown in <FIG>, the rectifier bridge is a full-bridge rectifier D1 composed of four diodes. As another example, the rectifier bridge may also be composed of two diodes connected in parallel, wherein directions (poles) of the two diodes are opposite. Due to a low clamping voltage of the TVS2, the rectifier bridge D1 may have a low voltage drop for conducting, thereby avoiding the subsequent branch of the power signal transmission branch being affected by an electrical surge remained after an electrical surge releasing performed by the electrical surge protection circuit <NUM>.

<FIG> illustrates a schematic diagram of another exemplary electrical surge protection circuit <NUM> according to some embodiments of the present disclosure. The electrical surge protection circuit <NUM> may be similar to the electrical surge protection circuit <NUM> as described in connection with <FIG>, except that the electrical surge protection circuit <NUM> may further include an electrical surge protection circuit <NUM> (also referred as to a fourth electrical surge protection circuit). One end of the electrical surge protection circuit <NUM> may be coupled to the common branch, and another end of the electrical surge protection circuit <NUM> may be coupled to the ground.

The electrical surge protection circuit <NUM> may be configured to release an electrical surge on the common branch. In such case, the electrical surge may be firstly reduced by the electrical surge releasing by the electrical surge protection circuit <NUM>, and then form the first electrical surge and the second electrical surge as described above. Once the electrical surge comes in the common branch via the coaxial cable interface J, the electrical surge protection circuit <NUM> may absorb a surge current and suppress a surge voltage to a lower level, which protects subsequent branches (i.e., the data signal transmission branch and the power signal transmission branch) from damaging, and avoids an overvoltage on the coaxial cable (e.g., the coaxial cable <NUM>) connected to the coaxial interface J. In some embodiments, if the electrical surge coming in the common branch is high, the electrical surge protection circuit <NUM> may effectively avoid an arc discharge generated by an electrical breakdown of air that is caused by the electrical surge.

<FIG> illustrates a schematic diagram of another exemplary electrical surge protection circuit <NUM> according to some embodiments of the present disclosure. The electrical surge protection circuit <NUM> may be an exemplary embodiment of the electrical surge protection circuit <NUM> as described in connection with <FIG>. As shown in <FIG>, the electrical surge protection circuit <NUM> may be similar to the electrical surge protection circuit <NUM> as described in connection with <FIG>, except that the electrical surge protection circuit <NUM> may further include the electrical surge protection circuit <NUM>. The electrical surge protection circuit <NUM> may include a fourth protection device and a GDT that are connected in series. The fourth protection device may include a TVS, a varistor, or the like. For example, as shown in <FIG>, the electrical surge protection circuit <NUM> may include an unidirectional TVS3 and a GDT2. Similar to the first and second protection device(s), a working voltage of the fourth protection device may need to be greater than the voltage of the data signal transmitted on the common branch. As shown in <FIG>, the first, second, or third protection device(s) releases an electrical surge remained after the electrical surge releasing of the fourth protection device, the working voltage of the fourth protection device may be greater than that of the first, second, or third protection device, so as to achieve a better electrical surge releasing performace. For illustration, the voltage of the power signal transmitted on the common branch is equal to 48V, and the voltage of the data signal transmitted on the common branch is equal to <NUM>. 3V hereinafter. In some embodiments, an off-state voltage of the TVS3 may be equal to 58V. As another example, since the electrical surge may undergo further electrical surge releasing performed by the electrical surge protection circuit(s) <NUM>-<NUM>, the fourth protection device may be a varistor with a clamping voltage higher than the clamping voltage of the TVS3. In some embodiments, an allowable voltage of the varistor may be equal to 65Vdc.

In some embodiments, the data signal transmitted on the common branch may include a high-frequency signal that is sensitive to parasitic capacitance. To reduce the influence on the transmission of the data signal, the electrical surge protection circuit <NUM> shall have a small capacitance. As described elsewhere in the present disclosure, the GDT usually has a small parasitic capacitance (typically, smaller than <NUM> pF). As a front - stage protection device coupled to the common branch, the TVS3 may have a large power and a large capacitance (typically, a hundred-pF level). A capacitance of the GDT2 may be smaller than a capacitance of the TVS3. By coupling the GDT2 to the TVS3 in series, the capacitance of the electrical surge protection circuit <NUM> may be reduced to be smaller than the capacitance of the GDT2, thereby improving the quality of data signal transmission. Merely by way of example, for the TVS3 with capacitance equal to 1000pF and the GDT2 with capacitance smaller than 1pF, the capacitance of the electrical surge protection circuit <NUM> may be lowered below 1pF. Since the TVS3 may return to a high-resistance state after the electrical surge releasing, the GDT2 may be protected from a follow-on current. In some embodiments, the GDT2 may have a breakdown voltage equal to 90V and a capacitance smaller than 1pF.

<FIG> illustrates a schematic diagram of another exemplary electrical surge protection circuit <NUM> according to some embodiments of the present disclosure. The electrical surge protection circuit <NUM> may be similar to the electrical surge protection circuit <NUM> as described in connection with <FIG>, except that in the electrical surge protection circuit <NUM>, the electrical surge protection circuit <NUM> is removed. In such case, in the data signal transmission branch, the electrical surge circuit <NUM> may release an electrical surge remained after a releasing of the electrical surge protection circuit <NUM> to a desired level.

It should be noted that the above descriptions of the electrical surge protection circuits <NUM>-<NUM> are intended to be illustrative, and not to limit the scope of the present disclosure. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments. For example, one or more of the electrical surge protection circuits <NUM>-<NUM> may include one or more additional components (e.g., one or more additional electrical surge protection circuit). Additionally or alternatively, one or more components of the one or more of the electrical surge protection circuits <NUM>-<NUM> described above may be omitted. For example, in the electrical surge protection ciecuits <NUM> or <NUM>, the electrical surge protection circuit <NUM> may be removed. In some embodiments, the first, second, third, and fourth protection devices may include other components.

Having thus described the basic concepts, it may be rather apparent to those skilled in the art after reading this detailed disclosure that the foregoing detailed disclosure is intended to be presented by way of example only and is not limiting. Various alterations, improvements, and modifications may occur and are intended to those skilled in the art, though not expressly stated herein. These alterations, improvements, and modifications are intended to be suggested by this disclosure and are within the spirit and scope of the exemplary embodiments of this disclosure.

Claim 1:
A circuit, comprising:
a coaxial cable interface (J);
a data module (<NUM>) configured to receive or output a data signal;
a power module (<NUM>) configured to receive or output a power signal;
a power signal transmission branch electrically coupled between the coaxial cable interface and the power module, wherein the power signal transmission branch includes an inductor (L) that allows the power signal to pass; and
a data signal transmission branch electrically coupled between the coaxial cable interface (J) and the data module (<NUM>), characterised in that:
the data signal transmission branch includes a capacitor (C3) that allows the data signal to pass, a resistor (R1), a first electrical surge protection circuit (<NUM>) configured to release a surge current on the data signal transmission branch, and a second electrical surge protection circuit (<NUM>), and the first electrical surge protection circuit (<NUM>) includes a first protection device and a gas discharge tube (GDT) that are connected in series;
a common branch electrically coupled between the coaxial cable interface (J) and a connection node (O) between the power signal transmission branch and the data signal transmission branch; and
a fourth electrical surge protection circuit (<NUM>) configured to release an electrical surge on the common branch, one end of the fourth electrical surge protection circuit (<NUM>) being coupled to the common branch, and another end being coupled to the ground, wherein
the data module (<NUM>) is coupled to the coaxial cable interface (J) via the second electrical surge protection circuit (<NUM>), the resistor (R1), the first electrical surge protection circuit (<NUM>), and the capacitor (C3) sequentially.