Patent Publication Number: US-10323838-B2

Title: LED tube lamp

Description:
RELATED APPLICATIONS 
     This application is a Continuation application of U.S. patent application Ser. No. 15/426,785, filed on Feb. 7, 2017, which is a Continuation application of U.S. patent application Ser. No. 15/210,989, filed on Jul. 15, 2016, which is a Continuation-In-Part application of U.S. patent application Ser. No. 15/066,645, filed on Mar. 10, 2016, which is a Continuation-In-Part application of U.S. patent application Ser. No. 14/865,387, filed on Sep. 25, 2015. 
     In addition, U.S. patent application Ser. No. 15/066,645, from which U.S. patent application Ser. No. 15/210,989 claims priority as a Continuation-In-Part also claims priority under 35 U.S.C. 119(e) to Chinese Patent Applications Nos.: CN 201510530110.3 filed on 2015 Aug. 26; and CN 201510645134.3 filed on 2015 Oct. 8. 
     In addition, U.S. patent application Ser. No. 15/210,989, from which U.S. patent application Ser. No. 15/426,785 claims priority as a Continuation-In-Part application of U.S. patent application Ser. No. 15/205,011, filed on Jul. 8, 2016, which is a Continuation-In-Part application of U.S. patent application Ser. No. 15/150,458, filed on May 10, 2016, which is a Continuation-In-Part Application of U.S. patent application Ser. No. 14/865,387, filed on Sep. 25, 2015, which claims priority under 35 U.S.C. 119(e) to the following Chinese Patent Applications filed in the Chinese Patent Office: CN 201510557717.0 filed on 2015 Sep. 6; and CN 201510595173.7 filed on 2015 Sep. 18. U.S. patent application Ser. No. 15/150,458, filed on 2016 May 10 is also a Continuation-In-Part application of U.S. patent application Ser. No. 14/699,138, filed on 2015 Apr. 29, now U.S. Pat. No. 9,480,109. 
     In addition, U.S. patent application Ser. No. 15/210,989, from which U.S. patent application Ser. No. 15/426,785 claims priority as a Continuation also claims priority under 35 U.S.C. 119(e) to Chinese Patent Application Nos.: CN 201510848766.X, filed on Nov. 27, 2015; CN 201610132513.7, filed on Mar. 9, 2016; CN 201610142140.1, filed on Mar. 14, 2016; CN 201610452437.8, filed on Jun. 20, 2016; CN 201510726365.7, filed on Oct. 30, 2015; and CN 201610044148.4, filed on Jan. 22, 2016. 
    
    
     TECHNICAL FIELD 
     The disclosed embodiments relate to the features of light emitting diode (LED) lighting. More particularly, the disclosed embodiments describe various improvements for LED tube lamps. 
     BACKGROUND 
     LED lighting technology is rapidly developing to replace traditional incandescent and fluorescent lighting. LED tube lamps are mercury-free in comparison with fluorescent tube lamps that need to be filled with inert gas and mercury. Thus, it is not surprising that LED tube lamps are becoming a highly desired illumination option among different available lighting systems used in homes and workplaces, which used to be dominated by traditional lighting options such as compact fluorescent light bulbs (CFLs) and fluorescent tube lamps. Benefits of LED tube lamps include improved durability and longevity and far less energy consumption. Therefore, when taking into account all factors, they would typically be considered as a cost effective lighting option. 
     Currently, LED tube lamps used to replace traditional fluorescent lighting devices can be primarily categorized into two types. One is for ballast-compatible LED tube lamps, e.g., T-LED lamp, which directly replace fluorescent tube lamps without rewiring the lighting fixture; and the other one is for ballast-bypass LED tube lamps, which omit traditional ballast on their circuit and directly connect the commercial electricity to the LED tube lamp. The latter LED tube lamp is suitable for the new surroundings in fixtures with new driving circuits and LED tube lamps. The ballast-compatible type LED tube lamp is also known as “Type-A” LED tube lamp, and the ballast-bypass type LED tube lamp provided with a lamp driving circuit is also known as a “Type-B” LED tube lamp. Compared to the ballast-compatible type LED tube lamp, the ballast-bypass type LED tube lamp has better luminous efficacy and longer life time since the power consumption and the malfunction concerns of the ballast can be excluded. 
     For the ballast-bypass type LED tube lamp, the power supply configuration can be categorized into two types. One is single-end power supply configuration, which receives the external AC signal merely through one side of the LED tube lamp; and the other one is dual-end power supply configuration, which receives the external AC signal through both sides of the LED tube lamp. In order to fulfill the light emitting requirements of traditional fluorescent lamps, the circuits of the traditional fluorescent lamp fixtures are designed and disposed for providing the AC signal through both ends of the lamp. For the purpose of replacing traditional fluorescent lamps, an LED tube lamp having the dual-end power supply configuration can be popularized much easier since the installation is simpler than the single-end power supply configuration. 
     However, there are some drawbacks in the dual-end power supply configuration. For example, when an LED tube lamp has an architecture with dual-end power supply and one end cap thereof is inserted into a lamp socket but the other is not, an electric shock situation could take place for the user touching the metal or conductive part of the end cap which has not been inserted into the lamp socket. 
     In the U.S. patent publication Ser. No. 20130335959, filed on Jun. 15, 2012, or the U.S. patent publication a solution of disposing a mechanical structure on the end cap for preventing electric shock is proposed. In this electric shock protection design, the connection between the external power and the internal circuit of the tube lamp can be cut off or established by the mechanical component&#39;s interaction/shifting when a user installs the tube lamp, so as to achieve the electric shock protection. However, due to the physical characteristics of the mechanical components, the mechanical fatigue may inevitably cause the reliability and durability of the electric shock protection to be limited. 
     On the other hand, although the ballast-bypass type and the ballast-compatible type LED tube lamps can be configured in the dual-end power supply configuration, there are many different considerations in the power supply circuit design. For example, due to the frequency of the voltage provided from the ballast being much higher than the frequency of the voltage directly provided from the commercial electricity/AC mains, the skin effect occurs when the leakage current is generated in the ballast-compatible type LED tube lamp, and thus the human body would not be harmed by the leakage current. Therefore, since the ballast-bypass type LED tube lamp has higher risk of electric shock/hazard, compared to the ballast-compatible type, it is preferred that the ballast-bypass type LED tube lamp have extremely low leakage current for meeting strict safety requirements. 
     In the PCT patent application WO2015/066566, filed on Oct. 31, 2014, a solution of utilizing an electronic switch in the power supply circuit for preventing electric shock is proposed. In this electric shock protection design, a transistor/switch is disposed in series with the input rectification stage of the fluorescent lamp replacement and the LED load, and a current flowing through the sense resistor will be detected for determining whether the fluorescent lamp replacement is correctly connected to the ballast. WO2015/066566 does not address the electric shock problem in the ballast-bypass type LED tube lamp. 
     In detail, compared to the power supply (typically an AC powerline or commercial electricity) for a ballast-bypass type LED tube lamp, the signal provided by a ballast (especially electronic ballast) has relatively high frequency or voltage. Further, for purposes such as one of driving a filament of a fluorescent lamp, a ballast may have to output a relatively high starting voltage as to excite electrons from the filament. So the starting voltage from a ballast can be as high as 1200 volts. On the other hand, the ballast-bypass type LED tube lamp is typically powered by commercial electricity with frequency as low as e.g. 50 Hz or 60 Hz and voltage as low as or below about 300 volts. Based on the above characteristics difference between power supplies for the direct replacement type LED tube lamp and the ballast-bypass type LED tube lamp, the benchmark and behavior for detecting the installation state is significantly different between the two types of LED tube lamps. For example, since the waveform of the current flowing through the sense resistor may be significantly different between the two types of LED tube lamps, utilizing the same determination criteria to determine whether the LED tube lamp is correctly installed is ineffective and will likely result in incorrect or inaccurate detection results. Thus, if the shock hazard detection of WO2015/066566 is applied to the ballast-bypass type LED tube lamp, a wrong detection result is relatively likely to occur, for example, because of the offset of the input voltage/current that may occur for lower frequency power signals. 
     Further, according to the circuit structure of WO2015/066566, a bias circuit is configured for starting the shock hazard detection, in which the input terminals of the bias circuit are connected to the ballast output at one side of the fixture. Therefore, the bias circuit can form a loop with the ballast and be powered up when one end of the LED tube lamp is installed on the corresponding socket/tombstone of the fixture. However, since there is only one output on each side of the fixture for providing the dual-end power so that the loop of the bias circuit cannot be formed, the shock hazard detection circuit of WO2015/066566 cannot be implemented in most of the ballast-bypass type LED tube lamps. 
     SUMMARY 
     It is specially noted that the present disclosure may actually include one or more embodiments of inventions claimed currently or not yet claimed, and for avoiding confusion due to unnecessarily distinguishing between those possible embodiments of inventions at the stage of preparing the specification, the possible plurality of inventions herein may be collectively referred to as “the (present) invention” herein. 
     Various embodiments are summarized in this section, and may be described with respect to the “present invention,” which terminology is used to describe certain presently disclosed embodiments, whether claimed or not, and is not necessarily an exhaustive description of all possible embodiments, but rather is merely a summary of certain embodiments. Certain of the embodiments described below as various aspects of the “present invention” can be combined in different manners to form an LED tube lamp or a portion thereof. 
     The present disclosure provides a ballast-bypass type LED tube lamp includes a lamp tube, two end caps, an LED module and a power supply module according to one or more embodiments of the present invention. Each end cap has an external connection terminal and couples to a respective end of the lamp tube, in which the external connection terminals are configured to receive an external driving signal having a frequency of 50 Hz or 60 Hz. The LED module is disposed in the lamp tube. The power supply module is configured to provide a DC driving signal to the LED module according to the external driving signal. The power supply module includes a rectifying circuit, a filtering circuit, a driving circuit and a detection module. The rectifying circuit is coupled to the external connection terminals, for rectifying the external driving signal to produce a rectified signal. The filtering circuit is coupled to the rectifying circuit, for filtering the rectified signal to produce a filtered signal. The driving circuit is coupled to the filtering circuit, for converting the filtered signal into the DC driving signal. The detection module has a first detection terminal coupled to the rectifying circuit and a second detection terminal coupled to the filtering circuit. The detection module temporarily conducts the first and the second detection terminals during a detection stage, so that a pulse current is generated when the LED tube lamp is powered on. The detection module performs a detection based on the pulse current, so as to determine whether to conduct or cut off the current path between the first and the second detection terminals after the detection stage. 
     The present disclosure provides a power supply module for supplying power to an LED module according to one or more embodiments of the present invention. The power supply module includes a rectifying circuit, a filtering circuit, a driving circuit and a detection module. The rectifying circuit has two input terminals for receiving an input signal and configured to rectify the input signal to produce a rectified signal. The filtering circuit is coupled to the rectifying circuit, for filtering the rectified signal to produce a filtered signal. The driving circuit is coupled to the filtering circuit, for converting the filtered signal into the DC driving signal. The detection module has a first detection terminal coupled to the rectifying circuit and a second detection terminal coupled to the filtering circuit. A leakage loop conducts when one of the input terminals receives the input signal and the other one of the input terminals is connected to ground via a resistive object. A pulse current is detected by the detection module when the leakage loop is conducted. 
     The present disclosure provides a LED tube lamp adapted to be installed on a lamp holder according to one or more embodiments of the present invention. The LED tube lamp includes a lamp tube, two end caps and an LED module. Each end cap has a conductive part and couples to a respective end of the lamp tube, in which the conductive parts are configured to be connected to the lamp holder. The LED module is disposed in the lamp tube. A first current is detected from the LED tube lamp when the conductive parts on both end caps are connected to the lamp holder. A second current is detected from the LED tube lamp when the conductive parts on both end caps are connected to the lamp holder. The maximum transient response of the first current is less than the minimum transient response of the second current. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a plane cross-sectional view schematically illustrating an LED tube lamp according to some exemplary embodiments; 
         FIG. 2  is a block diagram of an exemplary power supply system for an LED tube lamp according to some exemplary embodiments; 
         FIG. 3  is a block diagram of an exemplary LED lamp according to some exemplary embodiments; 
         FIG. 4  is a schematic diagram of a rectifying circuit according to some exemplary embodiments; 
         FIG. 5  is a schematic diagram of an exemplary filtering circuit according to some exemplary embodiments; 
         FIG. 6  is a block diagram of an exemplary power supply module in an LED lamp according to some exemplary embodiments; 
         FIG. 7  is a block diagram of a driving circuit according to some exemplary embodiments; 
         FIG. 8  is a schematic diagram of an exemplary driving circuit according to some exemplary embodiments; 
         FIG. 9  is a block diagram of an LED tube lamp according to some exemplary embodiments; 
         FIG. 10A  is a block diagram of an installation detection module according to some exemplary embodiments; 
         FIG. 10B  is a schematic diagram of a detection pulse generating module according to some exemplary embodiments; 
         FIG. 10C  is a schematic diagram of a detection determining circuit according to some exemplary embodiments; 
         FIG. 10D  is a schematic diagram of a detection result latching circuit according to some exemplary embodiments; 
         FIG. 10E  is a schematic diagram of a switch circuit according to some exemplary embodiments; 
         FIG. 11A  is a block diagram of an installation detection module according to some exemplary embodiments; 
         FIG. 11B  is a schematic diagram of a detection pulse generating module according to some exemplary embodiments; 
         FIG. 11C  is a schematic diagram of a detection result latching circuit according to some exemplary embodiments; 
         FIG. 11D  is a schematic diagram of a switch circuit according to some exemplary embodiments; and 
         FIG. 11E  is a schematic diagram of a detection determining circuit according to some exemplary embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present disclosure provides a novel LED tube lamp. The present disclosure will now be described in the following embodiments with reference to the drawings. The following descriptions of various embodiments of this invention are presented herein for purpose of illustration and giving examples only. It is not intended to be exhaustive or to be limited to the precise form disclosed. These example embodiments are just that—examples—and many implementations and variations are possible that do not require the details provided herein. It should also be emphasized that the disclosure provides details of alternative examples, but such listing of alternatives is not exhaustive. Furthermore, any consistency of detail between various examples should not be interpreted as requiring such detail—it is impracticable to list every possible variation for every feature described herein. The language of the claims should be referenced in determining the requirements of the invention. 
     In the drawings, the size and relative sizes of components may be exaggerated for clarity. Like numbers refer to like elements throughout. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items and may be abbreviated as “/”. 
     It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers, or steps, these elements, components, regions, layers, and/or steps should not be limited by these terms. Unless the context indicates otherwise, these terms are only used to distinguish one element, component, region, layer, or step from another element, component, region, or step, for example as a naming convention. Thus, a first element, component, region, layer, or step discussed below in one section of the specification could be termed a second element, component, region, layer, or step in another section of the specification or in the claims without departing from the teachings of the present invention. In addition, in certain cases, even if a term is not described using “first,” “second,” etc., in the specification, it may still be referred to as “first” or “second” in a claim in order to distinguish different claimed elements from each other. 
     It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. 
     It will be understood that when an element is referred to as being “connected” or “coupled” to or “on” another element, it can be directly connected or coupled to or on the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). However, the term “contact,” as used herein refers to direct connection (i.e., touching) unless the context indicates otherwise. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element&#39;s or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     Terms such as “same,” “equal,” “planar,” or “coplanar,” as used herein when referring to orientation, layout, location, shapes, sizes, amounts, or other measures do not necessarily mean an exactly identical orientation, layout, location, shape, size, amount, or other measure, but are intended to encompass nearly identical orientation, layout, location, shapes, sizes, amounts, or other measures within acceptable variations that may occur, for example, due to manufacturing processes. The term “substantially” may be used herein to emphasize this meaning, unless the context or other statements indicate otherwise. For example, items described as “substantially the same,” “substantially equal,” or “substantially planar,” may be exactly the same, equal, or planar, or may be the same, equal, or planar within acceptable variations that may occur, for example, due to manufacturing processes. 
     Terms such as “about” or “approximately” may reflect sizes, orientations, or layouts that vary only in a small relative manner, and/or in a way that does not significantly alter the operation, functionality, or structure of certain elements. For example, a range from “about 0.1 to about 1” may encompass a range such as a 0%-5% deviation around 0.1 and a 0% to 5% deviation around 1, especially if such deviation maintains the same effect as the listed range. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and/or the present application, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     As used herein, items described as being “electrically connected” are configured such that an electrical signal can be passed from one item to the other. Therefore, a passive electrically conductive component (e.g., a wire, pad, internal electrical line, etc.) physically connected to a passive electrically insulative component (e.g., a prepreg layer of a printed circuit board, an electrically insulative adhesive connecting two devices, an electrically insulative underfill or mold layer, etc.) is not electrically connected to that component. Moreover, items that are “directly electrically connected,” to each other are electrically connected through one or more passive elements, such as, for example, wires, pads, internal electrical lines, resistors, etc. As such, directly electrically connected components do not include components electrically connected through active elements, such as transistors or diodes. Directly electrically connected elements may be directly physically connected and directly electrically connected. 
     Embodiments may be described, and illustrated in the drawings, in terms of functional blocks, units and/or modules. Those skilled in the art will appreciate that these blocks, units and/or modules are physically implemented by electronic (or optical) circuits such as logic circuits, discrete components, analog circuits, hard-wired circuits, memory elements, wiring connections, and the like, which may be formed using semiconductor-based fabrication techniques or other manufacturing technologies. In the case of the blocks, units and/or modules being implemented by microprocessors or similar, they may be programmed using software (e.g., microcode) to perform various functions discussed herein and may optionally be driven by firmware and/or software. Alternatively, each block, unit and/or module may be implemented by dedicated hardware, or as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions. Also, each block, unit and/or module of the embodiments may be physically separated into two or more interacting and discrete blocks, units and/or modules. Further, the blocks, units and/or modules of the various embodiments may be physically combined into more complex blocks, units and/or modules. 
     If any terms in this application conflict with terms used in any application(s) from which this application claims priority, or terms incorporated by reference into this application or the application(s) from which this application claims priority, a construction based on the terms as used or defined in this application should be applied. 
     Referring to  FIG. 1 , an LED tube lamp ( 500 ) may include an LED light strip  2 . In certain embodiments, the LED light strip  2  may be formed from a bendable circuit sheet, for example that may be flexible. As described further below, the bendable circuit sheet, also described as a bendable circuit board, or a flexible or non-rigid tape. The bendable circuit sheet may have ends thereof passing across a transition region of the lamp tube of the LED tube lamp to be connected to a power supply module  5 . In some embodiments, the ends of the bendable circuit sheet may be connected to a power supply module  5  in an end cap of the LED tube lamp. For example, the ends may be connected in a manner such that a portion of the bendable circuit sheet is bent away from the lamp tube and passes through the transition region where a lamp tube narrows, and such that the bendable circuit sheet vertically overlaps part of a power supply within an end cap of the LED tube lamp. 
     Referring to  FIG. 2 , an alternating current (AC) power source  508  is used to supply an AC supply signal, and may be an AC powerline with a voltage rating, for example, in 100-277V and a frequency rating, for example, of 50 Hz or 60 Hz. The power supply module and power source  508  described above may include various elements for providing power to the LED light strip ( 2 ). For example, they may include power converters or other circuit elements for providing power to the LED light strip ( 2 ). The AC power source  508  is directly coupled to the pins  501  and  502 , which then receive the AC supply signal as the AC driving signal. 
     In some embodiments, the LED tube lamp may be power-supplied at its both end caps respectively having two conductive pins, which are coupled to the lamp driving circuit to concurrently receive the AC driving signal. In certain embodiments, each end cap of the LED tube lamp  500  could have only one conductive pin for receiving the AC driving signal. For example, it is not required to have two conductive pins used in each end cap for the purpose of passing electricity through the both ends of the LED tube lamp. The conductive pins  501  and  502  are correspondingly configured at both end caps of the LED tube lamp  500 , and the AC power source  508  is the same as those mentioned above. 
       FIG. 3  is a block diagram of an LED lamp according to one embodiment. Referring to  FIG. 3 , the power supply module of the LED lamp includes a rectifying circuit  510 , a filtering circuit  520 , and may further include some parts of an LED lighting module  530 . The rectifying circuit  510  is coupled to two pins  501  and  502  to receive and then rectify an external driving signal, so as to output a rectified signal at two rectifying output terminals  511  and  512 . In some embodiments, the external driving signal may be the AC driving signal or the AC supply signal described with reference to  FIG. 2 . In some embodiments, the external driving signal may be a direct current (DC) signal without altering the LED tube lamp. The filtering circuit  520  is coupled to the rectifying circuit for filtering the rectified signal to produce a filtered signal. For instance, the filtering circuit  520  is coupled to the rectifying circuit output terminals  511  and  512  to receive and then filter the rectified signal, so as to output a filtered signal at two filtering output terminals  521  and  522 . The LED lighting module  530  is coupled to the filtering circuit  520  to receive the filtered signal for emitting light. For instance, the LED lighting module  530  may include a circuit coupled to the filtering output terminals  521  and  522  to receive the filtered signal and thereby to drive an LED unit (not shown) in the LED lighting module  530  to emit light. Details of these operations are described below in accordance with certain embodiments. 
     Although there are two rectifying output terminals  511  and  512  and two filtering output terminals  521  and  522  in the embodiments shown in  FIG. 3 , in practice the number of ports or terminals for coupling between the rectifying circuit  510 , the filtering circuit  520 , and the LED lighting module  530  may be one or more depending on the needs of signal transmission between the circuits or devices. 
     In addition, the power supply module of the LED lamp described in  FIG. 3 , and embodiments of a power supply module of an LED lamp described below, may each be used in the LED tube lamp  500  in  FIGS. 1 and 2 , and may instead be used in any other type of LED lighting structure having two conductive pins used to conduct power, such as LED light bulbs, personal area lights (PAL), plug-in LED lamps with different types of bases (such as types of PL-S, PL-D, PL-T, PL-L, etc.), etc. Further, the implementation for LED light bulbs may provide better effects on protecting from electric shock as combining this invention and the structures disclosed in PCT patent application WO2016045631. 
       FIG. 4  is a schematic diagram of a rectifying circuit according to an embodiment. Referring to  FIG. 4 , a rectifying circuit  610 , i.e. a bridge rectifier, includes four rectifying diodes  611 ,  612 ,  613 , and  614 , configured to full-wave rectify a received signal. The diode  611  has an anode connected to the output terminal  512 , and a cathode connected to the pin  502 . The diode  612  has an anode connected to the output terminal  512 , and a cathode connected to the pin  501 . The diode  613  has an anode connected to the pin  502 , and a cathode connected to the output terminal  511 . The diode  614  has an anode connected to the pin  501 , and a cathode connected to the output terminal  511 . 
     When the pins  501  and  502  receive an AC signal, the rectifying circuit  610  operates as follows. During the connected AC signal&#39;s positive half cycle, the AC signal is input through the pin  501 , the diode  614 , and the output terminal  511  in sequence, and later output through the output terminal  512 , the diode  611 , and the pin  502  in sequence. During the connected AC signal&#39;s negative half cycle, the AC signal is input through the pin  502 , the diode  613 , and the output terminal  511  in sequence, and later output through the output terminal  512 , the diode  612 , and the pin  501  in sequence. Therefore, during the connected AC signal&#39;s full cycle, the positive pole of the rectified signal produced by the rectifying circuit  610  keeps at the output terminal  511 , and the negative pole of the rectified signal remains at the output terminal  512 . Accordingly, the rectified signal produced or output by the rectifying circuit  610  is a full-wave rectified signal. 
     When the pins  501  and  502  are coupled to a DC power supply to receive a DC signal, the rectifying circuit  610  operates as follows. When the pin  501  is coupled to the positive end of the DC power supply and the pin  502  to the negative end of the DC power supply, the DC signal is input through the pin  501 , the diode  614 , and the output terminal  511  in sequence, and later output through the output terminal  512 , the diode  611 , and the pin  502  in sequence. When the pin  501  is coupled to the negative end of the DC power supply and the pin  502  to the positive end of the DC power supply, the DC signal is input through the pin  502 , the diode  613 , and the output terminal  511  in sequence, and later output through the output terminal  512 , the diode  612 , and the pin  501  in sequence. Therefore, no matter what the electrical polarity of the DC signal is between the pins  501  and  502 , the positive pole of the rectified signal produced by the rectifying circuit  610  keeps at the output terminal  511 , and the negative pole of the rectified signal remains at the output terminal  512 . 
     Therefore, the rectifying circuit  610  in this embodiment can output or produce a proper rectified signal regardless of whether the received input signal is an AC or DC signal. 
       FIG. 5  is a schematic diagram of the filtering unit according to an embodiment of the present invention. Referring to  FIG. 5 , the filtering circuit  520  includes a filtering unit  723  coupled to two rectifying output terminals  511  and  512  to receive and to filter out ripples of a rectified signal from the rectifying circuit  510 . Accordingly, the waveform of a filtered signal is smoother than that of the rectified signal. 
     The filtering unit  723  includes a pi filter circuit including a capacitor  725 , an inductor  726 , and a capacitor  727 . The pi filter circuit looks like the symbol π in its shape or structure. The capacitor  725  has an end connected to the output terminal  511  and coupled to the filtering output terminal  521  through the inductor  726 , and has another end connected to the output terminal  512  and the filtering output terminal  522 . The inductor  726  is coupled between output terminal  511  and the filtering output terminal  521 . The capacitor  727  has an end connected to the filtering output terminal  521  and coupled to the output terminal  511  through the inductor  726 , and has another end connected to the output terminal  512  and the filtering output terminal  522 . 
     As seen between the output terminals  511  and  512  and the filtering output terminals  521  and  522 , the filtering unit  723  has an inductor  726  and a capacitor  727 , which perform the function of low-pass filtering like the capacitor  725  does. Therefore, the filtering unit  723  has a better ability to filter out high-frequency components to output a filtered signal with a smoother waveform. 
     The LED module  530  has an anode connected to a filtering output terminal  521 , a cathode connected to a filtering output terminal  522 , and includes at least one LED unit, such as the light source mentioned above. The LED unit may refer to a single string of LEDs arranged in series, and an LED module may refer to a single LED unit, or a plurality of LED units connected to a same two nodes (e.g., arranged in parallel). 
       FIG. 6  is a block diagram of a power supply module in an LED lamp according to an embodiment. As shown in  FIG. 6 , the power supply module of the LED lamp includes a rectifying circuit  510 , a filtering circuit  520 , and may further include some parts of an LED lighting module  530 . The LED lighting module  530  in this embodiment comprises a driving circuit  1530  and an LED module  630 . The driving circuit  1530  comprises a DC-to-DC converter circuit, and is coupled to the filtering output terminals  521  and  522  to receive a filtered signal and then perform power conversion for converting the filtered signal into a driving signal at the driving output terminals  1521  and  1522 . The LED module  630  is coupled to the driving output terminals  1521  and  1522  to receive the driving signal for emitting light. In some embodiments, the current of LED module  630  is stabilized at an objective current value. 
       FIG. 7  is a block diagram of the driving circuit according to an embodiment. Referring to  FIG. 7 , a driving circuit includes a controller  1531 , and a conversion circuit  1532  for power conversion based on a current source, for driving the LED module to emit light. The conversion circuit  1532  includes a switching circuit  1535  and an energy storage circuit  1538 . And the conversion circuit  1532  is coupled to the filtering output terminals  521  and  522  to receive and then convert a filtered signal, under the control by the controller  1531 , into a driving signal at the driving output terminals  1521  and  1522  for driving the LED module. Under the control by the controller  1531 , the driving signal output by the conversion circuit  1532  comprises a steady current, making the LED module emitting steady light. 
       FIG. 8  is a schematic diagram of the driving circuit according to an exemplary embodiment. Referring to  FIG. 8 , a driving circuit  1830  in this embodiment comprises a DC-to-DC converter circuit having a controller  1831  and a converter circuit. The converter circuit includes an inductor  1832 , a diode  1833  for “freewheeling” of current, a capacitor  1834 , and a switch  1835 . The driving circuit  1830  is coupled to the filtering output terminals  521  and  522  to receive and then convert a filtered signal into a driving signal for driving an LED module connected between the driving output terminals  1521  and  1522 . 
     The switch  1835  has a first terminal coupled to the filtering output terminal  521 , a second terminal coupled to the cathode of freewheeling diode  1833 , and a control terminal coupled to the controller  1831  to receive a control signal from the controller  1831  for controlling current conduction or cutoff between the first and second terminals of the switch  1835 . The anode of freewheeling diode  1833  is connected to the filtering output terminal  522  and the driving output terminal  1522 . The inductor  1832  has an end connected to the second terminal of switch  1835 , and another end connected to the driving output terminal  1521 . The capacitor  1834  is coupled between the driving output terminals  1521  and  1522  to stabilize the voltage between the driving output terminals  1521  and  1522 . 
     The controller  1831  is configured for controlling when to turn the switch  1835  on (in a conducting state) or off (in a cutoff state) according to a current detection signal S 535  and/or a current detection signal S 531 . When the switch  1835  is switched on, a current of a filtered signal is input through the filtering output terminal  521 , and then flows through the switch  1835 , the inductor  1832 , and the driving output terminals  1521  and  1522 , and then flows out from the filtering output terminal  522 . During this flowing of current, the current through the inductor  1832  and the voltage of the capacitor  1834  both increase with time, so the inductor  1832  and the capacitor  1834  are in a state of storing energy. On the other hand, when the switch  1835  is switched off, the inductor  1832  is in a state of releasing energy and thus the current through it decreases with time. In this case, the current through the inductor  1832  circulates through the driving output terminals  1521  and  1522 , the freewheeling diode  1833 , and back to the inductor  1832 . 
     In some embodiments the capacitor  1834  is an optional element, so it can be omitted and is thus depicted in a dotted line in  FIG. 8 . When the capacitor  1834  is omitted, no matter whether the switch  1835  is turned on or off, the current through the inductor  1832  will flow through the driving output terminals  1521  and  1522  to drive the LED module to continue emitting light. 
     As described above, because the controller  1831  included in the driving circuit  1830  is configured for controlling when to turn a switch  1835  on (in a conducting state) or off (in a cutoff state) according to a current detection signal S 535  and/or a current detection signal S 531 , the driving circuit  1830  can maintain a stable current flow through the LED module. Therefore, the color temperature may not change with current to some LED modules, such as white, red, blue, or green LED modules. For example, an LED can retain the same color temperature under different illumination conditions. In some embodiments, because the inductor  1832  plays the role of the energy-storing circuit releases the stored power when the switch  1835  cuts off, the voltage/current flowing through the LED module remains above a predetermined voltage/current level so that the LED module may continue to emit light maintaining the same color temperature. In this way, when the switch  1835  conducts again, the voltage/current flowing through the LED module does not need to be adjusted to go from a minimum value to a maximum value. Accordingly, the LED module lighting with flickering can be avoided, the entire illumination can be improved, the lowest conducting period can be smaller, and the driving frequency can be higher. 
     Referring to  FIG. 9 , a block diagram of an LED tube lamp including a power supply module in accordance with certain embodiments is illustrated. Compared to the LED lamp shown in  FIG. 3 , the LED tube lamp of  FIG. 9  includes a rectifying circuit  510 , a filtering circuit  520 , and an LED lighting module  530 , and further includes an installation detection module  2520 . The installation detection module  2520  is coupled to the rectifying circuit  510  via an installation detection terminal  2521  and is coupled to the filtering circuit  520  via an installation detection terminal  2522 . The installation detection module  2520  detects the signal passing through the installation detection terminals  2521  and  2522  and determines whether to cut off an LED driving signal (e.g., an external driving signal) passing through the LED tube lamp based on the detected result. The installation detection module  2520  includes circuitry configured to perform the steps of detecting the signal passing through the installation detection terminals  2521  and  2522  and determining whether to cut off an LED driving signal, and thus may be referred to as an installation detection circuit, or more generally as a detection circuit or cut-off circuit. When an LED tube lamp is not yet installed on a lamp socket or holder, or in some cases if it is not installed properly or is only partly installed (e.g., one side is connected to a lamp socket, but not the other side yet), the installation detection module  2520  detects a smaller current compared to a predetermined current (or current value) and determines the signal is passing through a high impedance through the installation detection terminals  2521  and  2522 . In this case, in certain embodiments, the installation detection circuit  2520  is in a cut-off state to make the LED tube lamp stop working. Otherwise, the installation detection module  2520  determines that the LED tube lamp has already been installed on the lamp socket or holder (e.g., when the installation detection module  2520  detects a current equal to or larger than a predetermined current and determines the signal is passing through a low impedance through the installation detection terminals  2521  and  2522 ), and maintains conductive state to make the LED tube lamp working normally. 
     For example, in some embodiments, when a current passing through the installation detection terminals  2521  and  2522  is greater than or equal to a specific, defined installation current (or a current value), which may indicate that the current supplied to the LED lighting module  530  is greater than or equal to a specific, defined operating current, the installation detection module  2520  is conductive to make the LED tube lamp operate in a conductive state. For example, a current greater than or equal to the specific current value may indicate that the LED tube lamp has correctly been installed in the lamp socket or holder. When the current passing through the installation detection terminals  2521  and  2522  is smaller than the specific, defined installation current (or the current value), which may indicate that the current supplied to the LED lighting module  530  is less than a specific, defined operating current, the installation detection module  2520  cuts off current to make the LED tube lamp enter in a non-conducting state based on determining that the LED tube lamp has been not installed in, or does not properly connect to, the lamp socket or holder. In certain embodiments, the installation detection module  2520  determines conducting or cutting off based on the impedance detection to make the LED tube lamp operate in a conducting state or enter non-conducting state. The LED tube lamp operating in a conducting state may refer to the LED tube lamp including a sufficient current passing through the LED module to cause the LED light sources to emit light. The LED tube lamp operating in a cut-off state may refer to the LED tube lamp including an insufficient current or no current passing through the LED module so that the LED light sources do not emit light. Accordingly, the occurrence of electric shock caused by touching the conductive part of the LED tube lamp which is incorrectly installed on the lamp socket or holder can be efficiently avoided. 
     Referring to  FIG. 10A , a block diagram of an installation detection module in accordance with certain embodiments is illustrated. The installation detection module includes a switch circuit  2580 , a detection pulse generating module  2540 , a detection result latching circuit  2560 , and a detection determining circuit  2570 . Certain of these circuits or modules may be referred to as first, second, third, etc., circuits as a naming convention to differentiate them from each other. 
     The detection determining circuit  2570  is coupled to and detects the signal between the installation detection terminals  2521  (through a switch circuit coupling terminal  2581  and the switch circuit  2580 ) and  2522 . The detection determining circuit  2570  is also coupled to the detection result latching circuit  2560  via a detection result terminal  2571  to transmit the detection result signal to the detection result latching circuit  2560 . The detection determining circuit  2570  may be configured to detect a current passing through terminals  2521  and  2522  (e.g., to detect whether the current is above or below a specific current value). 
     The detection pulse generating module  2540  is coupled to the detection result latching circuit  2560  via a pulse signal output terminal  2541 , and generates a pulse signal to inform the detection result latching circuit  2560  of a time point for latching (storing) the detection result. For example, the detection pulse generating module  2540  may be a circuit configured to generate a signal that causes a latching circuit, such as the detection result latching circuit  2560  to enter and remain in a state that corresponds to one of a conducting state or a cut-off state for the LED tube lamp. The detection result latching circuit  2560  stores the detection result according to the detection result signal (or detection result signal and pulse signal), and transmits or provides the detection result to the switch circuit  2580  coupled to the detection result latching circuit  2560  via a detection result latching terminal  2561 . The switch circuit  2580  controls the state between conducting or cut off between the installation detection terminals  2521  and  2522  according to the detection result. 
     Referring to  FIG. 10B , a schematic diagram of a detection pulse generating module in accordance with certain embodiments is illustrated. A detection pulse generating module  2640  may be a circuit that includes multiple capacitors  2642 ,  2645 , and  2646 , multiple resistors  2643 ,  2647 , and  2648 , two buffers  2644  and  2651 , an inverter  2650 , a diode  2649 , and an OR gate  2652 . The capacitor  2642  may be referred to as a first capacitor  2642 , the capacitor  2645  may be referred to as a second capacitor  2645 , and the capacitor  2646  may be referred to as a third capacitor  2646 . The resistor  2643  may be referred to as a first resistor  2643 , the resistor  2647  may be referred to as a second resistor  2647 , and the resistor  2648  may be referred to as a third resistor  2648 . The buffer  2644  may be referred to as a first buffer  2644  and the buffer  2651  may be referred to as a second buffer  2651 . The diode  2649  may be referred to as a first diode  2649  and the OR gate  2652  may be referred to as a first OR gate  2652 . With use or operation, the capacitor  2642  and the resistor  2643  connect in series between a driving voltage (e.g., a driving voltage source, which may be a node of a power supply), such as VCC usually defined as a high logic level voltage, and a reference voltage (or potential), such as ground potential in this embodiment. The connection node between the capacitor  2642  and the resistor  2643  is coupled to an input terminal of the buffer  2644 . In this exemplary embodiment, the buffer  2644  includes two inverters connected in series between an input terminal and an output terminal of the buffer  2644 . The resistor  2647  is coupled between the driving voltage, e.g., VCC, and an input terminal of the inverter  2650 . The resistor  2648  is coupled between an input terminal of the buffer  2651  and the reference voltage, e.g. ground potential in this embodiment. An anode of the diode  2649  is grounded and a cathode of the diode  2649  is coupled to the input terminal of the buffer  2651 . First ends of the capacitors  2645  and  2646  are jointly coupled to an output terminal of the buffer  2644 , and second, opposite ends of the capacitors  2645  and  2646  are respectively coupled to the input terminal of the inverter  2650  and the input terminal of the buffer  2651 . In this exemplary embodiment, the buffer  2651  includes two inverters connected in series between an input terminal and an output terminal of the buffer  2651 . An output terminal of the inverter  2650  and an output terminal of the buffer  2651  are coupled to two input terminals of the OR gate  2652 . According to certain embodiments, the voltage (or potential) for “high logic level” and “low logic level” mentioned in this specification are all relative to another voltage (or potential) or a certain reference voltage (or potential) in circuits, and further may be described as “logic high logic level” and “logic low logic level.” 
     When an end cap of an LED tube lamp is inserted into a lamp socket and the other end cap thereof is electrically coupled to a human body, or when both end caps of the LED tube lamp are inserted into the lamp socket, the LED tube lamp is conductive with electricity. At this moment, the installation detection module (e.g., the installation detection module  2520  as illustrated in  FIG. 9 ) enters into a detection stage. The voltage on the connection node of the capacitor  2642  and the resistor  2643  is high initially (equals to the driving voltage, VCC) and decreases with time to zero finally. The input terminal of the buffer  2644  is coupled to the connection node of the capacitor  2642  and the resistor  2643 , so the buffer  2644  outputs a high logic level signal at the beginning and changes to output a low logic level signal when the voltage on the connection node of the capacitor  2642  and the resistor  2643  decreases to a low logic trigger logic level. As a result, the buffer  2644  is configured to produce an input pulse signal and then remain in a low logic level thereafter (stops outputting the input pulse signal.) The width for the input pulse signal may be described as equal to one (initial setting) time period, which is determined by the capacitance value of the capacitor  2642  and the resistance value of the resistor  2643 . 
     Next, the operations for the buffer  2644  to produce the pulse signal with the initial setting time period will be described below. Since the voltage on a first end of the capacitor  2645  and on a first end of the resistor  2647  is equal to the driving voltage VCC, the voltage on the connection node of both of them is also a high logic level. The first end of the resistor  2648  is grounded and the first end of the capacitor  2646  receives the input pulse signal from the buffer  2644 , so the connection node of the capacitor  2646  and the resistor  2648  has a high logic level voltage at the beginning but this voltage decreases with time to zero (in the meantime, the capacitor stores the voltage being equal to or approaching the driving voltage VCC.) Accordingly, initially the inverter  2650  outputs a low logic level signal and the buffer  2651  outputs a high logic level signal, and hence the OR gate  2652  outputs a high logic level signal (a first pulse signal) at the pulse signal output terminal  2541 . At this moment, the detection result latching circuit  2560  (as illustrated in  FIG. 10A ) stores the detection result for the first time according to the detection result signal received from the detection determining circuit  2570  (as illustrated in  FIG. 10A ) and the pulse signal generated at the pulse signal output terminal  2541 . During that initial pulse time period, as illustrated in  FIG. 10A , the detection pulse generating module  2540  outputs a high logic level signal, which results in the detection result latching circuit  2560  outputting the result of that high logic level signal. 
     When the voltage on the connection node of the capacitor  2646  and the resistor  2648  decreases to the low logic trigger logic level, the buffer  2651  changes to output a low logic level signal to make the OR gate  2652  output a low logic level signal at the pulse signal output terminal  2541  (stops outputting the first pulse signal.) The width of the first pulse signal output from the OR gate  2652  is determined by the capacitance value of the capacitor  2646  and the resistance value of the resistor  2648 . 
     The operation after the buffer  2644  stops outputting the pulse signal is described as below. For example, the operation may be initially in an operating stage. Since the capacitor  2646  stores the voltage being almost equal to the driving voltage VCC, and when the buffer  2644  instantaneously changes its output from a high logic level signal to a low logic level signal, the voltage on the connection node of the capacitor  2646  and the resistor  2648  is below zero but will be pulled up to zero by the diode  2649  rapidly charging the capacitor  2646 . Therefore, the buffer  2651  still outputs a low logic level signal. 
     In some embodiments, when the buffer  2644  instantaneously changes its output from a high logic level signal to a low logic level signal, the voltage on the one end of the capacitor  2645  also changes from the driving voltage VCC to zero instantly. This makes the connection node of the capacitor  2645  and the resistor  2647  have a low logic level signal. At this moment, the output of the inverter  2650  changes to a high logic level signal to make the OR gate output a high logic level signal (a second pulse signal) at the pulse signal output terminal  2541 . The detection result latching circuit  2560  as illustrated in  FIG. 10A  stores the detection result for a second time according to the detection result signal received from the detection determining circuit  2570  (as illustrated in  FIG. 10A ) and the pulse signal generated at the pulse signal output terminal  2541 . Next, the driving voltage VCC charges the capacitor  2645  through the resistor  2647  to make the voltage on the connection node of the capacitor  2645  and the resistor  2647  increase with time to the driving voltage VCC. When the voltage on the connection node of the capacitor  2645  and the resistor  2647  increases to reach a high logic trigger logic level, the inverter  2650  outputs a low logic level signal again to make the OR gate  2652  stop outputting the second pulse signal. The width of the second pulse signal is determined by the capacitance value of the capacitor  2645  and the resistance value of the resistor  2647 . 
     As those mentioned above, in certain embodiments, the detection pulse generating module  2640  generates two high logic level pulse signals in the detection stage, which are the first pulse signal and the second pulse signal. These pulse signals are output from the pulse signal output terminal  2541 . Moreover, there is an interval with a defined time between the first and second pulse signals (e.g., an opposite-logic signal, which may have a low logic level when the pulse signals have a high logic level), and the defined time is determined by the capacitance value of the capacitor  2642  and the resistance value of the resistor  2643 . 
     From the detection stage entering the operating stage, the detection pulse generating module  2640  does not produce the pulse signal any more, and keeps the pulse signal output terminal  2541  on a low logic level potential. As described herein, the operating stage is the stage following the detection stage (e.g., following the time after the second pulse signal ends). The operating stage occurs when the LED tube lamp is at least partly connected to a power source, such as provided in a lamp socket. For example, the operating stage may occur when part of the LED tube lamp, such as only one side of the LED tube lamp, is properly connected to one side of a lamp socket, and part of the LED tube lamp is either connected to a high impedance, such as a person, and/or is improperly connected to the other side of the lamp socket (e.g., is misaligned so that the metal contacts in the socket do not contact metal contacts in the LED tube lamp). The operating stage may also occur when the entire LED tube lamp is properly connected to the lamp socket. 
     Referring to  FIG. 10C , a detection determining circuit in accordance with certain embodiments is illustrated. An exemplary detection determining circuit  2670  includes a comparator  2671  and a resistor  2672 . The comparator  2671  may also be referred to as a first comparator  2671  and the resistor  2672  may also be referred to as a fifth resistor  2672 . A negative input terminal of the comparator  2671  receives a reference logic level signal (or a reference voltage) Vref, a positive input terminal thereof is grounded through the resistor  2672  and is also coupled to a switch circuit coupling terminal  2581 . Referring to  FIG. 10A , the signal flowing into the switch circuit  2580  from the installation detection terminal  2521  outputs to the switch circuit coupling terminal  2581  to the resistor  2672 . When the current of the signal passing through the resistor  2672  reaches a certain level (for example, bigger than or equal to a defined current for installation, (e.g. 2 A) and this makes the voltage on the resistor  2672  higher than the reference voltage Vref (referring to two end caps inserted into the lamp socket) the comparator  2671  produces a high logic level detection result signal and outputs it to the detection result terminal  2571 . For example, when an LED tube lamp is correctly installed on a lamp socket, the comparator  2671  outputs a high logic level detection result signal at the detection result terminal  2571 , whereas the comparator  2671  generates a low logic level detection result signal and outputs it to the detection result terminal  2571  when a current passing through the resistor  2672  is insufficient to make the voltage on the resistor  2672  higher than the reference voltage Vref (referring to only one end cap inserted into the lamp socket.) Therefore, in some embodiments, when the LED tube lamp is incorrectly installed on the lamp socket or one end cap thereof is inserted into the lamp socket but the other one is grounded by an object such as a human body, the current will be too small to make the comparator  2671  output a high logic level detection result signal to the detection result terminal  2571 . 
     Referring to  FIG. 10D , a schematic detection result latching circuit according to some embodiments of the present invention is illustrated. A detection result latching circuit  2660  includes a D flip-flop  2661 , a resistor  2662 , and an OR gate  2663 . The D flip-flop  2661  may also be referred to as a first D flip-flop  2661 , the resistor  2662  may also be referred to as a fourth resistor  2662 , and the OR gate  2663  may also be referred to as a second OR gate  2663 . The D flip-flop  2661  has a CLK input terminal coupled to a detection result terminal  2571 , and a D input terminal coupled to a driving voltage VCC. When the detection result terminal  2571  first outputs a low logic level detection result signal, the D flip-flop  2661  initially outputs a low logic level signal at a Q output terminal thereof, but the D flip-flop  2661  outputs a high logic level signal at the Q output terminal thereof when the detection result terminal  2571  outputs a high logic level detection result signal. The resistor  2662  is coupled between the Q output terminal of the D flip-flop  2661  and a reference voltage, such as ground potential. When the OR gate  2663  receives the first or second pulse signals from the pulse signal output terminal  2541  or receives a high logic level signal from the Q output terminal of the D flip-flop  2661 , the OR gate  2663  outputs a high logic level detection result latching signal at a detection result latching terminal  2561 . The detection pulse generating module  2640  only in the detection stage outputs the first and the second pulse signals to make the OR gate  2663  output the high logic level detection result latching signal, and thus the D flip-flop  2661  decides the detection result latching signal to be the high logic level or the low logic level the rest of the time, e.g., including the operating stage after the detection stage. Accordingly, when the detection result terminal  2571  has no high logic level detection result signal, the D flip-flop  2661  keeps a low logic level signal at the Q output terminal to make the detection result latching terminal  2561  also keep a low logic level detection result latching signal in the detection stage. On the contrary, once the detection result terminal  2571  has a high logic level detection result signal, the D flip-flop  2661  outputs and keeps a high logic level signal (e.g., based on VCC) at the Q output terminal. In this way, the detection result latching terminal  2561  keeps a high logic level detection result latching signal in the operating stage as well. 
     Referring to  FIG. 10E , a schematic switch circuit according to some embodiments is illustrated. A switch circuit  2680  includes a transistor, such as a bipolar junction transistor (BJT)  2681 , as being a power transistor, which has the ability of dealing with high current/power and is suitable for the switch circuit. The BJT  2681  may also be referred to as a first transistor  2681 . The BJT  2681  has a collector coupled to an installation detection terminal  2521 , a base coupled to a detection result latching terminal  2561 , and an emitter coupled to a switch circuit coupling terminal  2581 . When the detection pulse generating module  2640  produces the first and second pulse signals, the BJT  2681  is in a transient conduction state. This allows the detection determining circuit  2670  to perform the detection for determining the detection result latching signal to be a high logic level or a low logic level. When the detection result latching circuit  2660  outputs a high logic level detection result latching signal at the detection result latching terminal  2561 , the BJT  2681  is in the conducting state to make the installation detection terminals  2521  and  2522  conducting. In contrast, when the detection result latching circuit  2660  outputs a low logic level detection result latching signal at the detection result latching terminal  2561  and the output from detection pulse generating module  2640  is a low logic level, the BJT  2681  is cut-off or in the blocking state to make the installation detection terminals  2521  and  2522  cut-off or blocking. 
     Since the external driving signal is an AC signal and in order to avoid the detection error resulting from the logic level of the external driving signal being just around zero when the detection determining circuit  2670  detects, the detection pulse generating module  2640  generates the first and second pulse signals to let the detection determining circuit  2670  perform two detections. So the issue of the logic level of the external driving signal being just around zero in a single detection can be avoided. In some cases, the time difference between the productions of the first and second pulse signals is not multiple times of half one cycle of the external driving signal. For example, it does not correspond to the multiple phase differences of 180 degrees of the external driving signal. In this way, when one of the first and second pulse signals is generated and unfortunately the external driving signal is around zero, it can be avoided that the external driving signal is again around zero when the other pulse signal is generated. 
     The time difference between the productions of the first and second pulse signals, for example, an interval with a defined time between both of them can be represented as following:
 
the interval=( X+Y )( T/ 2),
 
     where T represents the cycle of an external driving signal, X is a natural number, 0&lt;Y&lt;1, with Y in some embodiments in the range of 0.05-0.95, and in some embodiments in the range of 0.15-0.85. 
     Furthermore, in order to avoid the installation detection module entering the detection stage from misjudgment resulting from the logic level of the driving voltage VCC being too small, the first pulse signal can be set to be produced when the driving voltage VCC reaches or is higher than a defined logic level. For example, in some embodiments, the detection determining circuit  2670  works after the driving voltage VCC reaching a high enough logic level in order to prevent the installation detection module from misjudgment due to an insufficient logic level. 
     According to the examples mentioned above, when one end cap of an LED tube lamp is inserted into a lamp socket and the other one floats or electrically couples to a human body or other grounded object, the detection determining circuit outputs a low logic level detection result signal because of high impedance. The detection result latching circuit stores the low logic level detection result signal based on the pulse signal of the detection pulse generating module, making it as the low logic level detection result latching signal, and keeps the detection result in the operating stage, without changing the logic value. In this way, the switch circuit keeps cutting-off or blocking instead of conducting continually. And further, the electric shock situation can be prevented and the requirement of safety standard can also be met. On the other hand, when two end caps of the LED tube lamp are correctly inserted into the lamp socket, the detection determining circuit outputs a high logic level detection result signal because the impedance of the circuit for the LED tube lamp itself is small. The detection result latching circuit stores the high logic level detection result signal based on the pulse signal of the detection pulse generating module, making it as the high logic level detection result latching signal, and keeps the detection result in the operating stage. So, the switch circuit keeps conducting to make the LED tube lamp work normally in the operating stage. 
     In some embodiments, when one end cap of the LED tube lamp is inserted into the lamp socket and the other one floats or electrically couples to a human body, the detection determining circuit outputs a low logic level detection result signal to the detection result latching circuit, and then the detection pulse generating module outputs a low logic level signal to the detection result latching circuit to make the detection result latching circuit output a low logic level detection result latching signal to make the switch circuit cutting-off or blocking. As such, the switch circuit blocking makes the installation detection terminals, e.g. the first and second installation detection terminals, blocking. As a result, the LED tube lamp is in non-conducting or blocking state. 
     However, in some embodiments, when two end caps of the LED tube lamp are correctly inserted into the lamp socket, the detection determining circuit outputs a high logic level detection result signal to the detection result latching circuit to make the detection result latching circuit output a high logic level detection result latching signal to make the switch circuit conducting. As such, the switch circuit conducting makes the installation detection terminals, e.g. the first and second installation detection terminals, conducting. As a result, the LED tube lamp operates in a conducting state. 
     Thus, according to the operation of the installation detection module, a first circuit, upon connection of at least one end of the LED tube lamp to a lamp socket, generates and outputs two pulses, each having a pulse width, with a time period between the pulses. The first circuit may include various of the elements described above configured to output the pulses to a base of a transistor (e.g., a BJT transistor) that serves as a switch. The pulses occur during a detection stage for detecting whether the LED tube lamp is properly connected to a lamp socket. The timing of the pulses may be controlled based on the timing of various parts of the first circuit changing from high to low logic levels, or vice versa. 
     The pulses can be timed such that, during that detection stage time, if the LED tube lamp is properly connected to the lamp socket (e.g., both ends of the LED tube lamp are correctly connected to conductive terminals of the lamp socket), at least one of the pulse signals occurs when an AC current from a driving signal is at a non-zero level. For example, the pulse signals can occur at intervals that are different from half of the period of the AC signal. For example, respective start points or mid points of the pulse signals, or a time between an end of the first pulse signal and a beginning of the second pulse signal may be separated by an amount of time that is different from half of the period of the AC signal (e.g., it may be between 0.05 and 0.95 percent of a multiple of half of the period of the AC signal). During a pulse that occurs when the AC signal is at a non-zero level, a switch that receives the AC signal at the non-zero level may be turned on, causing a latch circuit to change states such that the switch remains permanently on so long as the LED tube lamp remains properly connected to the lamp socket. For example, the switch may be configured to turn on when each pulse is output from the first circuit. The latch circuit may be configured to change state only when the switch is on and the current output from the switch is above a threshold value, which may indicate a proper connection to a light socket. As a result, the LED tube lamp operates in a conducting state. 
     On the other hand, if both pulses occur when a driving signal at the LED tube lamp has a near-zero current level, or a current level below a particular threshold, then the state of the latch circuit is not changed, and so the switch is only on during the two pulses, but then remains permanently off after the pulses and after the detection mode is over. For example, the latch circuit can be configured to remain in its present state if the current output from the switch is below the threshold value. In this manner, the LED tube lamp remains in a non-conducting state, which prevents electric shock, even though part of the LED tube lamp is connected to an electrical power source. 
     It is worth noting that according to certain embodiments, the width of the pulse signal generated by the detection pulse generating module is between 10 μs to 1 ms, and it is used to make the switch circuit conducting for a short period when the LED tube lamp conducts instantaneously. In some embodiments, a pulse current is generated to pass through the detection determining circuit for detecting and determining. Since the pulse is for a short time and not for a long time, the electric shock situation will not occur. Furthermore, the detection result latching circuit also keeps the detection result during the operating stage (e.g., the operating stage being the period after the detection stage and during which part of the LED tube lamp is still connected to a power source), and no longer changes the detection result stored previously complying with the circuit state changing. A situation resulting from changing the detection result can thus be avoided. In some embodiments, the installation detection module, such as the switch circuit, the detection pulse generating module, the detection result latching circuit, and the detection determining circuit, could be integrated into a chip and then embedded in circuits for saving the circuit cost and layout space. 
     As discussed in the above examples, in some embodiments, an LED tube lamp includes an installation detection circuit comprising a first circuit configured to output two pulse signals, the first pulse signal output at a first time and the second pulse signal output at a second time after the first time, and a switch configured to receive an LED driving signal and to receive the two pulse signals, wherein the two pulse signals control turning on and off of the switch. The installation detection circuit may be configured to, during a detection stage, detect during each of the two pulse signals whether the LED tube lamp is properly connected to a lamp socket. When it is not detected during either pulse signal that the LED tube lamp is properly connected to the lamp socket, the switch may remain in an off state after the detection stage. When it is detected during at least one of the pulse signals that the LED tube lamp is properly connected to the lamp socket, the switch may remain in an on state after the detection stage. The two pulse signals may occur such that they are separated by a time different from a multiple of half of a period of the LED driving signal, and such that at least one of them does not occur when the LED driving signal has a current value of substantially zero. It should be noted that although a circuit for producing two pulse signals is described, the disclosure is not intended to be limiting as such. For example, a circuit may be implemented such that a plurality of pulse signals may occur, wherein at least two of the plurality of pulse signals are separated by a time different from a multiple of half of a period of the LED driving signal, and such that at least one of the plurality of pulse signals does not occur when the LED driving signal has a current value of substantially zero. 
     Referring to  FIG. 11A , an installation detection module according to an exemplary embodiment is illustrated. The installation detection module includes a detection pulse generating module  2740  (which may also be referred to as a detection pulse generating circuit/module or a first circuit), a detection result latching circuit  2760  (which may also be referred to as a second circuit), a switch circuit  2780  (which may also be referred to as a third circuit), and a detection determining circuit  2770  (which may also be referred to as a fourth circuit). The detection pulse generating module  2740  is coupled (e.g., electrically connected) to the detection result latching circuit  2760  via a path  2741  (also referred to as a third path), and is configured to generate at least one pulse signal. A path as described herein may include a conductive line connecting between two components, circuits, or modules, and may include opposite ends of the conductive line connected to the respective components, circuits or modules. The detection result latching circuit  2760  is coupled (e.g., electrically connected) to the switch circuit  2780  via a path  2761  (also referred to as a fourth path), and is configured to receive and output the pulse signal(s) from the detection pulse generating module  2740 . The switch circuit  2780  is coupled (e.g., electrically connected) to one end (e.g., a first installation detection terminal  2521 ) of a power loop of an LED tube lamp and the detection determining circuit  2770 , and is configured to receive the pulse signal(s) output from the detection result latching circuit  2760 , and configured to conduct (or turn on) during the pulse signal(s) so as to cause the power loop of the LED tube lamp to be conductive. The detection determining circuit  2770  is coupled (e.g., electrically connected) to the switch circuit  2780 , the other end (e.g., a second installation detection terminal  2522 ) of the power loop of the LED tube lamp and the detection result latching circuit  2760 , and is configured to detect at least one sampling signal on the power loop when the switch circuit  2780  and the power loop are conductive, so as to determine an installation state between the LED tube lamp and a lamp socket. The detection determining circuit  2770  is further configured to transmit detection result(s) to the detection result latching circuit  2760  for next control. In some embodiments, the detection pulse generating module  2740  is further coupled (e.g., electrically connected) to the output of the detection result latching circuit  2760  to control the time of the pulse signal(s). 
     In some embodiments, one end of a first path  2781  (also referred to as a first path) is coupled to a first node of the detection determining circuit  2770  and the opposite end of the first path  2781  is coupled to a first node of the switch circuit  2780 . In some embodiments, a second node of the detection determining circuit  2770  is coupled to the second installation detection terminal  2522  of the power loop and a second node of the switch circuit  2780  is coupled to the first installation detection terminal  2521  of the power loop. In some embodiments, one end of a path  2771  (also referred to as a second path) is coupled to a third node of the detection determining circuit  2770  and the opposite end of the second path  2771  is coupled to a first node of the detection result latching circuit  2760 , one end of a third path  2741  is coupled to a second node of the detection result latching circuit  2760  and the opposite end of the third path  2741  is coupled to a first node of the detection pulse generating circuit  2740 . In some embodiments, one end of a fourth path  2761  is coupled to a third node of the switch circuit  2780  and the opposite end of the fourth path  2761  is coupled to a third node of the detection result latching circuit  2760 . In some embodiments, the fourth path  2761  is also coupled to a second node of the detection pulse generating circuit  2740 . 
     In some embodiments, the detection determining circuit  2770  is configured for detecting a signal between the first installation detection terminal  2521  and the second installation detection terminal  2522  through the first path  2781  and the switch circuit  2780 . For example, because of the above configuration, the detection determining circuit  2770  is capable of detecting and determining whether a current passing through the first installation detection terminal  2521  and the second installation detection terminal  2522  is below or above a predetermined current value and transmitting or providing a detection result signal to the detection result latching circuit  2760  via the second path  2771 . 
     In some embodiments, the detection pulse generating circuit  2740  generates a pulse signal through the detection result latching circuit  2760  to make the switch circuit  2780  working in a conducting state during the pulse signal. Meanwhile, as a result, the power loop of the LED tube lamp between the installation detection terminals  2521  and  2522  is thus conducting as well. The detection determining circuit  2770  detects a sampling signal on the power loop and generates a signal based on a detection result to inform the detection result latching circuit  2760  of a time point for latching (storing) the detection result received by the detection result latching circuit  2760  from the detection determining circuit  2770 . For example, the detection determining circuit  2770  may be a circuit configured to generate a signal that causes a latching circuit, such as the detection result latching circuit  2760  to enter and remain in a state that corresponds to one of a conducting state or a cut-off state for the LED tube lamp. The detection result latching circuit  2760  stores the detection result according to the detection result signal (or detection result signal and pulse signal), and transmits or provides the detection result to the switch circuit  2780  coupled to the third node of the detection result latching circuit  2760  via the fourth path  2761 . The switch circuit  2780  receives the detection result transmitted from the detection result latching circuit  2760  via the third node of the switch circuit  2780  and controls the state between conducting or cut off between the installation detection terminals  2521  and  2522  according to the detection result. 
     The detail circuit architecture and the entire operation thereof of each of the detection pulse generating module  2740  (or circuit), the detection result latching circuit  2760 , the switch circuit  2780 , and the detection determining circuit  2770  will be described below. 
     Referring to  FIG. 11B , a detection pulse generating module according to an exemplary embodiment is illustrated. The detection pulse generating module  2740  includes: a resistor  2742  (which also may be referred to as a sixth resistor), a capacitor  2743  (which also may be referred to as a fourth capacitor), a Schmitt trigger  2744 , a resistor  2745  (which also may be referred to as a seventh resistor), a transistor  2746  (which also may be referred to as a second transistor), and a resistor  2747  (which also may be referred to as an eighth resistor). 
     In some embodiments, one end of the resistor  2742  is connected to a driving signal, for example, Vcc, and the other end of the resistor  2742  is connected to one end of the capacitor  2743 . The other end of the capacitor  2743  is connected to a ground node. In some embodiments, the Schmitt trigger  2744  has an input end and an output end, the input end connected to a connection node of the resistor  2742  and the capacitor  2743 , the output end connected to the detection result latching circuit  2760  via the third path  2741  ( FIG. 11A ). In some embodiments, one end of the resistor  2745  is connected to the connection node of the resistor  2742  and the capacitor  2743  and the other end of the resistor  2745  is connected to a collector of the transistor  2746 . An emitter of the transistor  2746  is connected to a ground node. In some embodiments, one end of the resistor  2747  is connected to a base of the transistor  2746  and the other end of the resistor  2747  is connected to the detection result latching circuit  2760  ( FIG. 11A ) and the switch circuit  2780  ( FIG. 11A ) via the fourth path  2761 . In certain embodiments, the detection pulse generating module  2740  further includes: a Zener diode  2748 , having an anode and a cathode, the anode connected to the other end of the capacitor  2743  to the ground, the cathode connected to the end of the capacitor  2743  (the connection node of the resistor  2742  and the capacitor  2743 ). 
     Referring to  FIG. 11C , a detection result latching circuit according to an exemplary embodiment is illustrated. The detection result latching circuit  2760  includes: a D flip-flop  2762  (which also may be referred to as a second D flip-flop), having a data input end D, a clock input end CLK, and an output end Q, the data input end D connected to the driving signal mentioned above (e.g., Vcc), the clock input end CLK connected to the detection determining circuit  2770  ( FIG. 11A ); and an OR gate  2763  (which also may be referred to as a third OR gate), having a first input end, a second input end, and an output end, the first input end connected to the output end of the Schmitt trigger  2744  ( FIG. 11B ), the second input end connected to the output end Q of the D flip-flop  2762 , the output end of the OR gate  2763  connected to the other end of the resistor  2747  ( FIG. 11B ) and the switch circuit  2780  ( FIG. 11A ). 
     Referring to  FIG. 11D , a switch circuit according to an exemplary embodiment is illustrated. The switch circuit  2780  includes: a transistor  2782  (which also may be referred to as a third transistor), having a base, a collector, and an emitter, the base connected to the output of the OR gate  2763  via the fourth path  2761  ( FIG. 11C ), the collector connected to one end of the power loop, such as the first installation detection terminal  2521 , the emitter connected to the detection determining circuit  2770  ( FIG. 11A ). In some embodiments, the transistor  2782  may be replaced by other equivalently electronic parts, e.g., a MOSFET. 
     Referring to  FIG. 11E , a detection determining circuit according to an exemplary embodiment is illustrated. The detection determining circuit  2770  includes: a resistor  2774  (which also may be referred to as a ninth resistor), one end of the resistor  2774  connected to the emitter of the transistor  2782  ( FIG. 11D ), the other end of the resistor  2774  connected to the other end of the power loop, such as the second installation detection terminal  2522 ; a diode  2775  (which also may be referred to as a second diode), having an anode and a cathode, the anode connected to an end of the resistor  2744  that is not connected to a ground node; a comparator  2772  (which also may be referred to as a second comparator), having a first input end, a second input end, and an output end; a comparator  2773  (which also may be referred to as a third comparator), having a first input end, a second input end, and an output end; a resistor  2776  (which also may be referred to as a tenth resistor); a resistor  2777  (which also may be referred to as an eleventh resistor); and a capacitor  2778  (which also may be referred to as a fifth capacitor). 
     In some embodiments, the first input end of the comparator  2772  is connected to a predefined signal, for example, a reference voltage, Vref=1.3V, but the reference voltage value is not limited thereto, the second input end of the comparator  2772  is connected to the cathode of the diode  2775 , and the output end of the comparator  2772  is connected to the clock input end of the D flip-flop  2762  ( FIG. 11C ). In some embodiments, the first input end of the comparator  2773  is connected to the cathode of the diode  2775 , the second input end of the comparator  2773  is connected to another predefined signal, for example, a reference voltage, Vref=0.3V, but the reference voltage value is not limited thereto, and the output end of the comparator  2773  is connected to the clock input end of the D flip-flop  2762  ( FIG. 11C ). In some embodiments, one end of the resistor  2776  is connected to the driving signal mentioned above (e.g., Vcc) and the other end of the resistor  2776  is connected to the second input end of the comparator  2772  and one end of the resistor  2777  that is not connected to a ground node and the other end of the resistor  2777  is connected to the ground node. In some embodiments, the capacitor  2778  is connected to the resistor  2777  in parallel. In certain embodiments, the diode  2775 , the comparator  2773 , the resistors  2776  and  2777 , and the capacitor  2778  may be omitted, and the second input end of the comparator  2772  may be directly connected to the end of the resistor  2774  (e.g., the end of the resistor  2774  that is not connected to the ground node) when the diode  2775  is omitted. In certain embodiments, the resistor  2774  may include two resistors connected in parallel based on the consideration of power consumption having an equivalent resistance value ranging from about 0.1 ohm to about 5 ohm. 
     In some embodiments, some parts of the installation detection module may be integrated into an integrated circuit (IC) in order to provide reduced circuit layout space resulting in reduced manufacturing cost of the circuit. For example, the Schmitt trigger  2744  of the detection pulse generating module  2740 , the detection result latching circuit  2760 , and the two comparators  2772  and  2773  of the detection determining circuit  2770  may be integrated into an IC, but the disclosure is not limited thereto. 
     An operation of the installation detection module will be described in more detail in accordance with some example embodiments. In one exemplary embodiment, the capacitor voltage may not mutate; the voltage of the capacitor in the power loop of the LED tube lamp before the power loop being conductive is zero and the capacitor&#39;s transient response may appear to have a short-circuit condition; when the LED tube lamp is correctly installed to the lamp socket, the power loop of the LED tube lamp in transient response may have a smaller current-limiting resistance and a bigger peak current; and when the LED tube lamp is incorrectly installed to the lamp socket, the power loop of the LED tube lamp in transient response may have a bigger current-limiting resistance and a smaller peak current. This embodiment may also meet the UL standard to make the leakage current of the LED tube lamp less than 5 MIU. The following table illustrates the current comparison in a case when the LED tube lamp works normally (e.g., when the two end caps of the LED tube lamp are correctly installed to the lamp socket) and in a case when the LED tube lamp is incorrectly installed to the lamp socket (e.g., when one end cap of the LED tube lamp is installed to the lamp socket but the other one is touched by a human body). 
     
       
         
           
               
               
               
             
               
                   
               
               
                   
                 Correct installation 
                 Incorrect installation 
               
               
                   
               
             
            
               
                 Maximum transient current 
                   
                 
                   
                     
                       
                         
                           i 
                           
                             pk 
                             ⁢ 
                             _ 
                             ⁢ 
                             max 
                           
                         
                         = 
                         
                           
                             
                               V 
                               
                                 in 
                                 ⁢ 
                                 _ 
                                 ⁢ 
                                 pk 
                               
                             
                             
                               
                                 R 
                                 fuse 
                               
                               + 
                               500 
                             
                           
                           = 
                           
                             
                               
                                 305 
                                 × 
                                 1.414 
                               
                               
                                 10 
                                 + 
                                 500 
                               
                             
                             = 
                             
                               845 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               mA 
                             
                           
                         
                       
                     
                   
                 
               
               
                   
               
               
                 Minimum transient current 
                 
                   
                     
                       
                         
                           i 
                           
                             pk 
                             ⁢ 
                             _ 
                             ⁢ 
                             min 
                           
                         
                         = 
                         
                           
                             
                               ΔV 
                               in 
                             
                             
                               R 
                               fuse 
                             
                           
                           = 
                           
                             
                               50 
                               10 
                             
                             = 
                             
                               5 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               A 
                             
                           
                         
                       
                     
                   
                 
               
               
                   
               
            
           
         
       
     
     As illustrated in the above table, in the part of the denominator: R fuse  represents the resistance of the fuse of the LED tube lamp. For example, 10 ohm may be used, but the disclosure is not limited thereto, as resistance value for R fuse  in calculating the minimum transient current i pk   _   min  and 510 ohm may be used as resistance value for R fuse  in calculating the maximum transient current i pk   _   max  (an additional 500 ohms is used to emulate the conductive resistance of human body in transient response). In the part of the numerator: maximum voltage from the root-mean-square voltage (Vmax=Vrms*1.414=305*1.414) is used in calculating the maximum transient current i pk   _   max  and minimum voltage difference, for example, 50V (but the disclosure is not limited thereto) is used in calculating the minimum transient current i pk   _   min . Accordingly, when the LED tube lamp is correctly installed to the lamp socket (e.g., when two end caps of the LED tube lamp are installed to the lamp socket correctly) and works normally, its minimum transient current is 5 A. But, when the LED tube lamp is incorrectly installed to the lamp socket (e.g., when one end cap is installed to the lamp socket but the other one is touched by human body), its maximum transient current is only 845 mA. Therefore, certain examples of the disclosed embodiments use the current which passes transient response and flows through the capacitor in the LED power loop, such as the capacitor of the filtering circuit, to detect and determine the installation state between the LED tube lamp and the lamp socket. For example, such embodiments may detect whether the LED tube lamp is correctly installed to the lamp socket. Certain examples of the disclosed embodiments further provide a protection mechanism to protect the user from electric shock caused by touching the conductive part of the LED tube lamp which is incorrectly installed to the lamp socket. The embodiments mentioned above are used to illustrate certain aspects of the disclosed invention but the disclosure is not limited thereto. 
     Further, referring to  FIG. 11A  again, in some embodiments, when an LED tube lamp is being installed to a lamp socket, after a period (e.g., the period utilized to determine the cycle of a pulse signal), the detection pulse generating module  2740  outputs a first high level voltage rising from a first low level voltage to the detection result latching circuit  2760  through the third path  2741 . The detection result latching circuit  2760  receives the first high level voltage, and then simultaneously outputs a second high level voltage to the switch circuit  2780  and the detection pulse generating module  2740  through the fourth path  2761 . In some embodiments, when the switch circuit  2780  receives the second high level voltage, the switch circuit  2780  conducts to cause the power loop of the LED tube lamp to be conductive as well. In this exemplary embodiment, the power loop at least includes the first installation detection terminal  2521 , the switch circuit  2780 , the first path  2781 , the detection determining circuit  2770 , and the second installation detection terminal  2522 . In the meantime, the detection pulse generating module  2740  receives the second high level voltage from the detection result latching circuit  2760 , and after a period (e.g., the period utilized to determine the width (or period) of pulse signal), its output from the first high level voltage falls back to the first low level voltage (the first time of the first low level voltage, the first high level voltage, and the second time of the first low level voltage form a first pulse signal). In some embodiments, when the power loop of the LED tube lamp is conductive, the detection determining circuit  2770  detects a first sampling signal, such as a voltage signal, on the power loop. When the first sampling signal is greater than or equal to a predefined signal, such as a reference voltage, the installation detection module determines that the LED tube lamp is correctly installed to the lamp socket according to the application principle of this disclosed embodiments described above. Therefore, the detection determining circuit  2770  included in the installation detection module outputs a third high level voltage (also referred to as a first high level signal) to the detection result latching circuit  2760  through the second path  2771 . The detection result latching circuit  2760  receives the third high level voltage (also referred to as the first high level signal) and continues to output a second high level voltage (also referred to as a second high level signal) to the switch circuit  2780 . The switch circuit  2780  receives the second high level voltage (also referred to as the second high level signal) and maintains conductive state to cause the power loop to remain conductive. The detection pulse generating module  2740  does not generate any pulse signal while the power loop remains conductive. 
     However, in some embodiments, when the first sampling signal is smaller than the predefined signal, the installation detection module, according to certain exemplary embodiments as described above, determines that the LED tube lamp has not been correctly installed to the lamp socket. Therefore, the detection determining circuit  2770  outputs a third low level voltage (also referred to as a first low level signal) to the detection result latching circuit  2760 . The detection result latching circuit  2760  receives the third low level voltage (also referred to as the first low level signal) and continues to output a second low level voltage (also referred to as a second low level signal) to the switch circuit  2780 . The switch circuit  2780  receives the second low level voltage (also referred to as the second low level signal) and then keeps blocking to cause the power loop to remain open. Accordingly, the occurrence of electric shock caused by touching the conductive part of the LED tube lamp which is incorrectly installed on the lamp socket can be sufficiently avoided. 
     In some embodiments, when the power loop of the LED tube lamp remains open for a period (a period that represents the cycle of pulse signal), the detection pulse generating module  2740  outputs the first high level voltage rising from the first low level voltage to the detection result latching circuit  2760  through the third path  2741  once more. The detection result latching circuit  2760  receives the first high level voltage, and then simultaneously outputs a second high level voltage to the switch circuit  2780  and the detection pulse generating module  2740 . In some embodiments, when the switch circuit  2780  receives the second high level voltage, the switch circuit  2780  conducts again to cause the power loop of the LED tube lamp (in this exemplary embodiment, the power loop at least includes the first installation detection terminal  2521 , the switch circuit  2780 , the path  2781 , the detection determining circuit  2770 , and the second installation detection terminal  2522 ) to be conductive as well. In the meantime, the detection pulse generating module  2740  receives the second high level voltage from the detection result latching circuit  2760 , and after a period (a period that is utilized to determine the width (or period) of pulse signal), its output from the first high level voltage falls back to the first low level voltage (the third time of the first low level voltage, the second time of the first high level voltage, and the fourth time of the first low level voltage form a second pulse signal). In some embodiments, when the power loop of the LED tube lamp is conductive again, the detection determining circuit  2770  also detects a second sampling signal, such as a voltage signal, on the power loop yet again. When the second sampling signal is greater than or equal to the predefined signal, the installation detection module determines, according to certain exemplary embodiments described above, that the LED tube lamp is correctly installed to the lamp socket. Therefore, the detection determining circuit  2770  outputs a third high level voltage (also referred to as a first high level signal) to the detection result latching circuit  2760  through the path  2771 . The detection result latching circuit  2760  receives the third high level voltage (also referred to as the first high level signal) and continues to output a second high level voltage (also referred to as a second high level signal) to the switch circuit  2780 . The switch circuit  2780  receives the second high level voltage (also referred to as the second high level signal) and maintains a conductive state to cause the power loop to remain conductive. The detection pulse generating module  2740  does not generate any pulse signal while the power loop remains conductive. 
     In some embodiments, when the second sampling signal is smaller than the predefined signal, the installation detection module determines, according to certain exemplary embodiments described above, that the LED tube lamp has not been correctly installed to the lamp socket. Therefore, the detection determining circuit  2770  outputs the third low level voltage (also referred to as the first low level signal) to the detection result latching circuit  2760 . The detection result latching circuit  2760  receives the third low level voltage (also referred to as the first low level signal) and continues to output the second low level voltage (also referred to as the second low level signal) to the switch circuit  2780 . The switch circuit  2780  receives the second low level voltage (also referred to as the second low level signal) and then keeps blocking to cause the power loop to remain open. 
     Next, referring to  FIG. 11B - FIG. 11E  at the same time, in some embodiments when an LED tube lamp is being installed to a lamp socket, the capacitor  2743  is charged by the driving signal, for example, Vcc, through the resistor  2742 . And when the voltage of the capacitor  2743  rises enough to trigger the Schmitt trigger  2744 , the Schmitt trigger  2744  outputs a first high level voltage rising from a first low level voltage in an initial state to an input end of the OR gate  2763 . After the OR gate  2763  receives the first high level voltage from the Schmitt trigger  2744 , the OR gate  2763  outputs a second high level voltage to the base of the transistor  2782  and the resistor  2747 . When the base of the transistor  2782  receives the second high level voltage from the OR gate  2763 , the collector and the emitter of the transistor  2782  are conductive to further cause the power loop of the LED tube lamp (in this exemplary embodiment, the power loop at least includes the first installation detection terminal  2521 , the transistor  2782 , the resistor  2744 , and the second installation detection terminal  2522 ) to be conductive as well. In the meantime, the base of the transistor  2746  receives the second high level voltage from the OR gate  2763  through the resistor  2747 , and then the collector and the emitter of the transistor  2746  are conductive and grounded to cause the voltage of the capacitor  2743  to be discharged to the ground through the resistor  2745 . In some embodiments, when the voltage of the capacitor  2743  is not enough to trigger the Schmitt trigger  2744 , the Schmitt trigger  2744  outputs the first low level voltage falling from the first high level voltage (a first instance of a first low level voltage at a first time, followed by a first high level voltage, followed by a second instance of the first low level voltage at a second time form a first pulse signal). When the power loop of the LED tube lamp is conductive, the current passing through the capacitor in the power loop, such as, the capacitor of the filtering circuit, by transient response flows through the transistor  2782  and the resistor  2774  and forms a voltage signal on the resistor  2774 . The voltage signal is compared to a reference voltage, for example, 1.3V, but the reference voltage is not limited thereto, by the comparator  2772 . When the voltage signal is greater than and/or equal to the reference voltage, the comparator  2772  outputs a third high level voltage to the clock input end CLK of the D flip-flop  2762 . In the meantime, since the data input end D of the D flip-flop  2762  is connected to the driving signal, the D flip-flop  2762  outputs a high level voltage (at its output end Q) to another input end of the OR gate  2763 . This causes the OR gate  2763  to keep outputting the second high level voltage to the base of the transistor  2782 , and further results in the transistor  2782  and the power loop of the LED tube lamp remaining in a conducting state. Besides, since the OR gate  2763  keeps outputting the second high level voltage to cause the transistor  2746  to be conductive to the ground, the capacitor  2743  is unable to reach enough voltage to trigger the Schmitt trigger  2744 . 
     However, when the voltage signal on the resistor  2774  is smaller than the reference voltage, the comparator  2772  outputs a third low level voltage to the clock input end CLK of the D flip-flop  2762 . In the meantime, since the initial output of the D flip-flop  2762  is a low level voltage (e.g., zero voltage), the D flip-flop  2762  outputs a low level voltage (at its output end Q) to the other input end of the OR gate  2763 . Moreover, the Schmitt trigger  2744  connected by the input end of the OR gate  2763  also restores outputting the first low level voltage, the OR gate  2763  thus keeps outputting the second low level voltage to the base of the transistor  2782 , and further results in the transistor  2782  to remain in a blocking state (or an off state) and the power loop of the LED tube lamp to remain in an open state. Still, since the OR gate  2763  keeps outputting the second low level voltage to cause the transistor  2746  to remain in a blocking state (or an off state), the capacitor  2743  is charged by the driving signal through the resistor  2742  once again for next (pulse signal) detection. 
     In some embodiments, the cycle (or interval) of the pulse signal is determined by the values of the resistor  2742  and the capacitor  2743 . In some embodiments, the cycle of the pulse signal may include a value ranging from about 3 milliseconds to about 500 milliseconds and in some embodiments may range from about 20 milliseconds to about 50 milliseconds. In some embodiments, the width (or period) of the pulse signal is determined by the values of the resistor  2745  and the capacitor  2743 . In some embodiments, the width of the pulse signal may include a value ranging from about 1 microsecond to about 100 microseconds and in some embodiments may range from about 10 microseconds to about 20 microseconds. The Zener diode  2748  provides a protection function but it may be omitted in certain cases. The resistor  2742  may include two resistors connected in parallel based on the consideration of power consumption in certain cases, and its equivalent resistance may include a value ranging from about 0.1 ohm to about 5 ohm. The resistors  2776  and  2777  provides the function of voltage division to make the input of the comparator  2773  bigger than the reference voltage, such as 0.3V, but the value of the reference voltage is not limited thereto. The capacitor  2778  provides the functions of regulation and filtering. The diode  2775  limits the signal to be transmitted in one way. 
     In some embodiments, a period (or a width) of the first pulse signal is between 10 microseconds-1 millisecond, a period (or a width) of the second pulse signal is between 10 microseconds-1 millisecond. 
     In some embodiments, a period (or a width) of the first pulse signal is between 1 microsecond-100 microseconds, a period (or a width) of the second pulse signal is between 1 microsecond-100 microseconds. 
     In some embodiments, at least two protection elements, such as two fuses, are respectively connected between the internal circuits of the LED tube lamp and the conductive pins of the LED tube lamp, and which are on the power loop of the LED tube lamp. In some embodiments, four fuses are used for an LED tube lamp having power-supplied at its both end caps respectively having two conductive pins. In this case, for example, two fuses are respectively connected between two conductive pins of one end cap and between one of the two conductive pins of this end cap and the internal circuits of the LED tube lamp; and the other two fuses are respectively connected between two conductive pins of the other end cap and between one of the two conductive pins of the other end cap and the internal circuits of the LED tube lamp. In some embodiment, the capacitance between a power supply (or an external driving source) and the rectifying circuit of the LED tube lamp may be ranging from 0 to about 100 pF. In some embodiments, the abovementioned installation detection module may be configured to use an external power supply. 
     According to the design of the power supply module, the external driving signal may be a low frequency AC signal (e.g., commercial power), input into the LED tube lamp through a drive architecture of dual-end power supply. 
     According to the design of the rectifying circuit in the power supply module, there may be a dual rectifying circuit. First and second rectifying circuits of the dual rectifying circuit are respectively coupled to the two end caps disposed on two ends of the LED tube lamp. The dual rectifying circuit may comprise, for example, two half-wave rectifier circuits, two full-wave bridge rectifying circuits or one half-wave rectifier circuit and one full-wave bridge rectifying circuit. 
     According to the design of the pin in the LED tube lamp, there may be two pins in single end (the other end has no pin), two pins in corresponding ends of two ends, or four pins in corresponding ends of two ends. The designs of two pins in single end and two pins in corresponding ends of two ends are applicable to a signal rectifying circuit design of the rectifying circuit. The design of four pins in corresponding ends of two ends is applicable to a dual rectifying circuit design of the rectifying circuit, and the external driving signal can be received by two pins in only one end or any pin in each of two ends. 
     A protection circuit may be additionally added to protect the LED module. The protection circuit detects the current and/or the voltage of the LED module to determine whether to enable corresponding over current and/or over voltage protection. 
     The above-mentioned exemplary features of the present invention can be accomplished in any combination to improve the LED tube lamp, and the above embodiments are described by way of examples only. The present invention is not herein limited, and many variations are possible without departing from the spirit of the present invention and the scope as defined in the appended claims.