CN109041320B

CN109041320B - LED tube

Info

Publication number: CN109041320B
Application number: CN201810428458.5A
Authority: CN
Inventors: 张清富; 李志峰; 杨旭生; 陈玉立
Original assignee: Ledvance GmbH
Current assignee: Ledvance GmbH
Priority date: 2018-05-07
Filing date: 2018-05-07
Publication date: 2020-12-08
Anticipated expiration: 2038-05-07
Also published as: CN109041320A

Abstract

The application discloses an LED tube for being installed in a lamp. The LED tube includes: a first pair of contact pins disposed at a first end of the LED tube and a second pair of contact pins disposed at a second end of the LED tube; an array of LEDs; an LED driver for driving the LED array; the circuit comprises a switching device, and the switching device is used for switching the LED tube from a first working state to a second working state. The first operating state is suitable for supplying power to the LED driver from a single end of the LED tube through one pair of contact pins, and the second operating state is suitable for supplying power to the LED tube from two ends through two pairs of contact pins. The switch device is configured to automatically adjust the operating state of the LED tube when the LED tube is installed in and powered from a light fixture.

Description

LED tube

Technical Field

The present application relates generally to the field of LED tubes, and more particularly to LED tubes for replacing fluorescent tubes.

Background

Due to the high efficiency and robustness of Light Emitting Diodes (LEDs), LED-based lamps offer an attractive alternative to conventional lamps such as incandescent lamps or low pressure gas discharge fluorescent lamps. However, replacing a fluorescent tube by an LED tube is not always straightforward, especially since the electrical ballasts used in existing fluorescent tube luminaires are usually configured for receiving and powering low-pressure gas discharge lamps instead of LED lamps. Furthermore, since there are different types of electrical ballasts in use, the LED tubes require different driver configurations to match the existing electrical ballasts. Furthermore, replacing the fluorescent tubes with LED tubes may also lead to safety issues, i.e. there is a risk of electric shock to the person installing the LED tubes in the luminaire initially configured for the fluorescent tubes.

Disclosure of Invention

It is an object of the present application to provide an LED tube that enables easy and safe replacement of an existing fluorescent tube.

According to a first aspect, an LED tube for mounting in a luminaire is provided. In particular, the lamp may be a lamp for receiving a fluorescent low-pressure gas discharge tube and may be equipped with a ballast suitable for operating the aforementioned fluorescent tube. The LED tube has a substantially tubular body, in particular a body similar to a fluorescent tube to be replaced by the LED tube. The LED tube includes a first pair of contact pins disposed at a first end thereof and a second pair of contact pins disposed at a second end thereof. In particular, the first and second pairs of contact pins may be adapted to electrically connect the LED tube to a luminaire designed for a fluorescent tube.

The LED tube further comprises an LED array, an LED driver for driving the LED array, and in particular an electrical circuit for providing an electrical connection between the LED driver and the contact pins, the electrical circuit having switching means for switching the LED tube from a first operating state suitable for powering the LED driver from one end of the LED tube via one pair of contact pins to a second operating state suitable for powering the LED tube from both ends via two pairs of contact pins. The switching device is configured to automatically adjust the operating state of the LED tube when the LED tube is powered from the luminaire, in particular when the LED tube is installed in the luminaire and the luminaire is switched on, or when the LED tube is inserted into the luminaire with the power supply switched on. In other words, the switching device is configured to recognize an operating state of the LED tube, which is required when the LED tube is being installed in the lamp, and to automatically switch the operating state of the LED tube when necessary.

In this way, the LED tube can automatically adapt to the lamp, in particular to the ballast used in the lamp. For example, if an LED tube is being installed into a light fixture having a standard electrical control device (ECG) designed for fluorescent tubes, the switching device will recognize that the LED tube is installed in the forward light fixture and will adjust the operating state or mode of the LED tube accordingly. However, if the LED tube is being installed in a luminaire configured to be powered from a single end, in particular from an AC power source or from a CCG (current control device), the switching arrangement will recognize this situation and the LED tube will remain in a first operating state or mode of operation suitable for powering the LED from the single end of the LED tube. Thus, the LED tube is adapted and ready to operate safely with different configurations of the lamp and different ballasts, whereby the same LED driver can be used without any further adjustments to the LED tube or the lamp. Furthermore, the LED tube has a single driver used in both operating states, making the LED tube simple and cost-effective to manufacture.

In a first operating state of the LED tube, the second pair of contact pins may be electrically isolated from the first pair of contact pins. In this specification, electrically isolated means that the impedance between the first and second pairs of contact pins is high enough to prevent significant current flow between the first and second pairs of contact pins, which represents a safety issue for the person installing the LED tube.

The LED tube may include a first filament circuit associated with the first pair of contact pins and a second filament circuit associated with the second pair of contact pins. In particular, the first and second filament circuits may include one or more filament resistors that serve as replacements for the filaments of the fluorescent lamp, thereby enabling the ballast configured for the fluorescent tube to operate the LED tube.

At least one of the first filament circuit and the second filament circuit may be configured as an AC filter. The AC filter may be used as a low pass filter for filtering out undesired high frequency transients.

The switching device may have a first control input and a second control input for activating the switching device, in particular by means of electrical signals applied to the first control input and the second control input, wherein the first control input is electrically connected to the first pair of contact pins or to the first filament circuit and the second control input is electrically connected to the second pair of contact pins or to the second filament circuit.

Since the control input of the switching means is electrically connected to the first pair of contact pins and the second end contact pin, the switching means can be activated if an electrical signal, in particular an electrical signal associated with the ECG of the luminaire, is detected. In this case, the LED tube will automatically adopt its configuration when inserted into the luminaire.

The switching device may be equipped with a frequency detection circuit such that the switching device is activated upon detection of a particular frequency of an electrical signal applied to a control input of the switching device. By detecting the characteristic frequency of the electrical signal for a particular ECG, the ECG of the luminaire can be reliably identified.

The switch arrangement may comprise at least one normally closed contact for electrically connecting the LED driver to the first pair of contact pins and a normally open contact for electrically disconnecting the LED driver from the second pair of contact pins. Thus, in a normal or unpowered state, the LED tube is in a first operational state suitable for powering the LED tube by the first pair of contact pins, while the second pair of contact pins at the second end of the LED tube remain electrically isolated, so that the LED tube can be safely installed in the luminaire even if the luminaire power supply is not switched off.

The switching device may be a high impedance switching device. In particular, the switching device may comprise a high impedance primary circuit for controlling a secondary circuit having on and off contacts. In this specification, high impedance means that the impedance is high enough to limit the current flowing through the primary circuit of the switching device such that the current through the primary circuit does not exceed a specified allowable safety limit. Thus, the current flowing through the primary circuit of the switching device cannot cause any injury to the person mounting the LED tube.

The switching device may be a relay, in particular a high impedance relay having a primary circuit comprising a high impedance electromagnet and a secondary circuit having on-off contacts. By means of the electrical separation of the primary and secondary circuits of the relay, a reliable isolation of the two ends of the LED tube in the first state can be achieved.

According to another aspect, a method of operating an LED tube is provided. The LED tube comprises an LED array, an LED driver for driving the LED array, a first pair of contact pins arranged at the first end of the LED tube and a second pair of contact pins arranged at the second end of the LED tube, and the LED tube can work in a first working state suitable for supplying power to the LED tube from a single end through one pair of contact pins and in a second working state suitable for supplying power to the LED tube from two ends through two pairs of contact pins. The operation method of the LED tube comprises the following steps:

-bringing the LED tube in a first operating state;

-powering the LED tube by a power supply;

-determining that the LED tube is suitable for the operating state of the power supply;

-switching the operating state of the LED tube to the second operating state if it is determined that the operating state suitable for the power supply is not the first operating state of the LED tube.

The method enables automatic adjustment of the LED tube configuration or operating state for a luminaire, in particular for a power supply or an electrical ballast used in the luminaire.

In a first operating state, the second pair of contact pins may be electrically isolated from the first pair of contact pins and the LED driver. No significant current can flow between the first and second pairs of contact pins due to the electrical isolation or high impedance between the first and second pairs of contact pins (such current could be dangerous to the person installing the LED tube).

The method may include monitoring at least one electrical signal applied to the LED tube, wherein the LED tube is adapted to determine the operating state of the power supply based on the monitoring of the at least one electrical signal. Based on the monitoring results, the LED tube may automatically adjust its configuration for the ballast of the fixture when installed into and powered by the fixture.

The switching of the LED tube from the first operating state to the second operating state is achieved by a switching device, which is activated by at least one electrical signal applied to the LED tube.

The at least one electrical signal applied to the LED tube may be an electrical signal applied to the first and second pair of contact pins from both ends of the LED tube, in particular when the LED tube is being inserted into a powered luminaire (so-called hot-swap). Based on the electrical signals applied to the first and second pairs of contact pins from both ends of the LED tube, it can be easily determined whether the luminaire into which the LED tube is inserted is configured for operating the LED tube in the second operating state.

The method enables safe use and versatile use of the LED tube, especially with different luminaires having different ballast configurations, whereby the same LED driver is used for different ballast configurations.

Drawings

In the following description, details describing embodiments of the present application will be provided. It will be apparent, however, to one skilled in the art that the embodiments may be practiced without the foregoing details.

Some portions of these embodiments have similar elements. Similar elements may have the same name or similar element number. Where appropriate, the description of one element is applied by reference to another similar element, to reduce repetition of text and not to limit the invention.

Fig. 1 shows a circuit diagram of an LED tube according to an embodiment, the LED tube being brought into a first operating state during a first half-cycle of an AC power source.

Fig. 2 shows a circuit diagram of the LED tube of fig. 1, the LED tube being brought into a first operating state during a second half-cycle of the AC power source.

Fig. 3 shows a circuit diagram of the LED tube of fig. 1, the LED tube being brought into a second operating state during a first half-cycle of the AC power source.

Fig. 4 shows a circuit diagram of the LED tube of fig. 1, the LED tube being brought into a second operating state during a second half-cycle of the AC power source.

Fig. 5 shows a circuit diagram of another LED tube according to another embodiment.

Fig. 6 shows a schematic diagram of a switching device for the LED tube of fig. 1 according to an embodiment.

Detailed Description

Fig. 1 shows a circuit diagram of an LED tube according to an embodiment, which is in a first operating state during a first half cycle of an AC power source. . The LED tube 1 includes a substantially tubular body 2. The LED tube 1 further comprises a first filament circuit 50, a second filament circuit 60, an LED light engine 30 and a switching device 40. The first and

second filament circuits

50, 60 are connected to the LED light engine 30 via the switching device 40.

The first filament circuit 50 includes a first contact pin P1, a second contact pin P2, a first fuse F1, a first filament resistor R1, a second filament resistor R2, and a capacitor C1. The first and second contact pins P1 and P2 form a first pair of contact pins and are disposed in a first base (not shown) at a first end of the body 2 of the LED tube. The first contact pin P1 is electrically connected to a first end of the first fuse F1. A second terminal of the first fuse F1 is connected to a first terminal of a first filament resistor R1. A second terminal of the first filament resistor R1 is connected to a first terminal of a capacitor C1. A second terminal of the capacitor C1 is connected to a second terminal of the resistor R2. A first end of the resistor R2 is connected to the second contact pin P2.

The second filament circuit 60 includes a third contact pin P3, a fourth contact pin P4, a second fuse F2, a third resistor R3, and a fourth resistor R4. The third and fourth contact pins P3 and P4 form a second pair of contact pins and are disposed in a first base (not shown) at the first end of the body 2 of the LED tube. The third contact pin P3 is electrically connected to a first end of the second fuse F2. A second terminal of the second fuse F2 is connected to a first terminal of a third filament resistor R3. A second end of the third filament resistor R3 is connected to a second end of the fourth filament resistor R4. A first end of the fourth filament resistor R4 is connected to a fourth contact pin P4.

The LED light engine 30 includes an LED array 20, represented by LEDs D1, D2, and D3 in fig. 1 by way of example, the LED light engine 30 further includes an LED driver circuit having a rectifier bridge 70 and a voltage regulator 80, wherein an output side of the rectifier 70 is connected to an input side of the voltage regulator 80. The rectifier bridge 70 includes four diodes D4, D5, D6, and D7. The voltage regulator 80 includes an inductor L, a diode D8, a transistor T, and a smoothing capacitor C. The resistor R5 is connected in series with the LEDs D1, D2 and D3.

The switching device 40 includes

contacts

41, 42, 43 and a contactor 44, and is configured such that the contact 42 is in contact with the

contact

41 or 43, respectively.

A second end of the first resistor R1 is electrically connected by a wire 91 to a first input of the LED light engine 30, i.e., the junction of diodes D4 and D6. A second end of the second filament resistor R2 is electrically connected to the contact 41 of the switching device 40 by a lead 92.

The contacts 42 of the switching device 40 are electrically connected to a second input of the LED light engine 30 by wires 93. The contact 43 of the switching device 40 is electrically connected to the second ends of the third and fourth filament resistors R3 and R4 by a lead 94.

The first and second pairs of contact pins are configured to provide a mechanical and/or electrical connection of the LED tube to a lamp, which may have a ballast configured to receive a fluorescent low voltage discharge tube or LED tube. In operation, the rectifier bridge 70 rectifies the AC power applied to the LED tubes for driving the LED array 20. The inductor L, diode D8, transistor T and smoothing capacitor C are connected to stabilize and regulate the voltage provided to the LED array 20. The resistor R5 is used to limit the current flowing through the LEDs D1, D2 and D3.

The filament resistors R1, R2, R3 and R4 are used as substitutes for the filaments of fluorescent lamps, thereby enabling the ballast configured for fluorescent tubes to operate the LED tubes, and particularly ensuring that the ballast designed for operating fluorescent tubes also matches the LED tubes. The output side of the capacitor C1 connected to the resistors R1 and R2 forms an RC circuit that can be used as an AC filter, particularly for filtering out high frequency transients.

The switching device 40 may be actuated by an electrical signal applied to the switching device 40, specifically to the

contacts

41 and 43 via the

leads

92 and 94. In the initial or non-energized state of the switching device, the contactor 44 connects the

contacts

41 and 42. This position of the contactor 44 of the switching device corresponds to a first operating state of the LED tube. After activation of the switching device 40, the contactor 44 is switched to the second position, in which the contactor 44 connects the

contacts

42 and 43 of the switching device 40 and the

contacts

41 and 42 are disconnected, resulting in a second configuration or a second operating state of the LED tube 1.

Thus, the position of the contactor 44 shown in fig. 1 corresponds to an unpowered or default state of the switching device 40, resulting in a first configuration or operating state of the LED tube. In a first operating state of the LED tube, the second end of the second filament resistor R2 is electrically connected to the second input of the rectifier bridge 70 via the

leads

92 and 93, the

contacts

41 and 42 of the switching device 40 and the contactor 44.

Thus, in the first configuration, the LED light engine may be powered by the first pair of contact pins P1 and P2. . The first configuration or first operating state of the LED tube 1 is particularly suitable for a luminaire configured for a single-ended power supply.

The arrows in fig. 1 indicate current paths in the LED tube in the first operation state during the first half cycle of the AC power applied to the first and second contact pins P1 and P2. In the first half period, a positive voltage is applied to the first contact pin P1 with respect to the second contact pin P2. In this case, current flows from the first contact pin P1 through the first fuse F1, the first filament resistor R1, the wire 91 to the first input of the rectifier bridge 70, i.e., to the junction of the diodes D4 and D6. Further, the current flows back to the rectifier bridge 70 through the diode D4, the inductance L, the diode D8, the LED D1, the D2, and the D3, and the resistor R5. The current flows to the second contact pin P2 through diode D7, contact 42, contactor 44, contact 41, lead 92 and second filament resistor R2.

Fig. 2 illustrates a circuit diagram of the LED tube of fig. 1 in a first operation state during a second half-cycle of the AC power applied to the first and second contact pins P1 and P2. In the second half period, a negative voltage is applied to the first contact pin P1 with respect to the second contact pin P2. In this case, current flows from the second contact pin P2 through the second filament resistor R2, contact 41, contactor 44, contact 42, wire 93 to the second input of the rectifier bridge 70, i.e., the junction of diodes D5 and D7. Further, the current flows back to the rectifier bridge 70 through the diode D5, the inductance L, the diode D8, the LED D1, the D2, and the D3, and the resistor R5. The current flows to the first contact pin P1 through the diode D6, the wire 91, the first filament resistor R1 and the first fuse F1. However, in this case, when the LED tube 1 is being installed into a light fixture configured for receiving a light pipe having a double-ended power supply, the switching device 40 may be activated once a voltage is applied between the first and

second filament circuits

50 and 60, and thus between the

wires

92 and 94. As a result of the activation of the switching device, the contactor 44 changes its position such that the

contacts

42 and 43 of the switching device 40 are connected and the

contacts

Fig. 3 shows a circuit diagram of the LED tube shown in fig. 1 in a second operation state during a first half cycle of the AC power applied between the first pair of contact pins P1, P2 and the second pair of contact pins P3, P4. In a second operating state of the LED tube, the

contacts

41 and 42 are disconnected and the

contacts

42 and 43 are connected via the contactor 44 of the switching device 40. Thus, in this configuration, the second input of the rectifier bridge 70, i.e., the junction of the diodes D5 and D7, is connected to the second ends of the third and fourth filament resistors R3 and R4 via the lead 93, the contact 42, the contactor 44, the contact 43, and the lead 94. If power is applied across the LED tube 1, in particular if an AC voltage is applied between the first and second pairs of contact pins P1, P2, P3, P4, the LED light engine 30 can be powered from both ends of the LED tube 1, from the first and second pairs of contact pins P1, P2, P3, P4. Thus, by switching to the second operating state upon detection of the application of an electrical signal from both sides of the LED tube, the LED tube automatically adjusts itself and adapts its electrical configuration to the power supply or ballast implemented in the luminaire in which the LED tube is inserted. The arrows in fig. 3 indicate the current path in the LED tube in the second operating state during the first half cycle of the AC power applied between the first pair of contact pins P1, P2 and the second pair of contact pins P3, P4. In the first half-cycle, a positive voltage is applied to the first pair of contacts P1, P2 with respect to the second pair of contacts P3, P4. As indicated by the arrows, current flows from the first contact pin P1 through the first fuse F1 through the first filament resistor R1 and from the second contact pin P2 through the second filament resistor R2 through the capacitor C1. Further, current flows from the second terminal of the first filament resistor R1 through the wire 91 to the first input of the rectifier bridge 70, i.e., the junction of the diodes D4 and D6. Further, the current flows back to the rectifier bridge 70 through the diode D4, the inductor L, the diode D8, the LED D1, the D2, and the D3, the resistor R5. Current flows to the second pair of contact pins P3, P4 through diode D7, lead 93, contact 42, contactor 44, contact 43, lead 94, third filament resistor R3 and fourth filament resistor R4.

Fig. 4 shows a circuit diagram of the LED tube shown in fig. 1 in a second operation state during a second half period of the AC power applied between the first pair of contact pins P1, P2 and the second pair of contact pins P3, P4. In the second half-cycle, a positive voltage is applied to the second pair of contacts P3, P4 with respect to the first pair of contacts P1, P2. As indicated by the arrows, current flows from the third and fourth contact pins P3 and P4 through the third and fourth filament resistors R3 and R4 and further through the wire 94, the contact 43, the contactor 44, the contact 42, the wire 93 to the second input of the rectifier bridge 70, i.e., the junction of the diodes D5 and D7. Further, the current flows back to the rectifier bridge 70 through the diode D5, the inductor L, the diode D8, the LED D1, the D2, and the D3, the resistor R5. Current flows to the first contact pin P1 through the diode D6, the lead wire 91, the first filament resistor R1, the first fuse F1. Current also flows through the capacitor C1, the second filament resistor R2 to the second contact pin P2.

In the initial state of the LED tube 1, no voltage is applied to the switching device 40, the

contacts

42 and 43 are disconnected and the

contacts

41 and 42 are connected via the contactor 44. Thus, in this initial state, both inputs of the rectifier 70 are electrically connected to the first pair of contact pins P1, P2. Thus, in this initial state, the LED tube 1 is configured to operate by supplying power to the first pair of contact pins P1 and P2, while the second pair of contact pins P3, P4 are electrically disconnected from the LED light engine 30 by the switching device 40. Thus, the initial state of the LED tube 1 corresponds to the operational state of the LED tube in which it is operated by supplying power to the first pair of contact pins P1 and P2, while the second pair of contact pins P3, P4 is electrically deactivated since the second pair of contact pins P3, P4 is disconnected from the LED light engine 30.

Fig. 5 shows a circuit diagram of an LED tube according to another embodiment. The LED tube 1' of fig. 5 essentially corresponds to the LED tube 1 of fig. 1, the working principle of which has been described above. However, in the LED tube 1 'of fig. 5, a specific type of switching device 40' is implemented, which includes a relay (not shown) and a frequency detection circuit (not shown).

Unlike the switching device 40 of fig. 1, the switching device 40 'has six

contacts

41, 42, 43, 47, 48, 49 and two contactors 44, 44'. Similar to the switching device 40 of fig. 1, the switching device 40 'of fig. 5 may be actuated by applying an electrical signal to the switching device 40', specifically via the

conductors

92 and 94.

The positions of the contactors 44 and 44 'of the switching device 40' as shown in fig. 5 correspond to the first operating state of the LED tube. In this state, the output side of the second filament resistor R2 is connected by wire 92 to contact 41 and to the second input of the LED light engine 30 via contactor 44 and contact 42. Thus, the switching device 40' is configured for single-ended supply of power on pins P1 and P2. On the other hand, the second pair of contact pins P3, P4 are electrically isolated from the LED light engine 30 by the switching device 40', similar to the circuit in fig. 1 and 2.

Upon detecting an electrical signal applied to the

wires

92 and 94, the switching device 40 ' is activated and switches to a second state in which the

contacts

42 and 43 are connected through the contactor 44 and the contacts 47 and 48 are connected through the contactor 44 ', thereby connecting the wire 94 to the second input of the LED light engine 30 through the

contacts

48, 47, 43, 42, the contactors 44 ', 44 and the wire 92. This configuration of the switching device 40' corresponds to a second operating state of the LED tube 1, see fig. 3 and 4. By providing a dual-contactor switch arrangement, reliable isolation of the second pair of contact pins P3, P4 from the circuitry of the LED tube (and in particular from the LED light engine 30) can be achieved. Specifically, even if one of the contactors 44 and 44' is soldered or molded in a closed state, the second contactor still achieves electrical isolation, thus reducing the risk of a person installing the LED tube being clicked.

Fig. 6 shows a schematic view of a switching device according to an embodiment. In particular, fig. 6 shows a possible variant of the switching device 40 for the LED tube of fig. 1, which in this embodiment is a high impedance relay comprising a high impedance electromagnet 45 and a drive shaft 46, the drive shaft 46 being operatively connected with the electromagnet 45 and the contactor 44. Upon receiving a sufficiently strong electrical signal, such as an AC voltage signal from mains or from the ballast of the light fixture, at the first and

second control inputs

95 and 96 via the connection lines 92 and 94, the electromagnet 45 is activated so that the contactor 44 moves from its first position electrically connecting the

contacts

41 and 42 to its second position connecting the

contacts

42 and 43. Thus, the electrical wire 93 leading to the second input of the commutator bridge 70 switches from the wire 92 connected to the second output of the first filament circuit 50 to the wire 94 connected to the second filament circuit 60.

Although an electromechanical switching device is shown, those skilled in the art will appreciate that other types of switching devices may be implemented. The switching means may be provided in the form of an electrical switch based on a high power transistor, such as a MOSFET, designed to switch the LED tube circuit between different configurations or topologies depending on the lamp in which the LED tube is mounted. In particular, the first and second filament circuits may each be configured as an AC filter circuit, and the switching device may comprise a signal monitor for monitoring at least one electrical signal applied to the contact pins P1, P2, P3, P4 and a switching unit configured to switch the LED tube to a specific operation mode upon detection of an electrical signal indicating that the luminaire is configured to operate with the LED tube in that specific operation state.

While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments.

Description of the reference numerals

1, 1' LED tube

2-pipe (shape) body

20 LED array

30 LED light engine

40, 40' switching device

41 contact

42 contact

43 contact

44 contact

44' contactor

45 electromagnet

46 drive shaft

47 contact

48 contact

49 contact

50 first filament circuit

60 second filament circuit

70 rectifier bridge

80 voltage regulator

91 wire

92 conducting wire

93 conducting wire

94 conducting wire

95 control input

96 control input

C capacitor

C1 capacitor

D1 LED

D2 LED

D3 LED

D4 diode

D5 diode

D6 diode

D7 diode

D8 diode

EM electromagnet

F1 electric fuse

F2 electric fuse

P1 contact pin

P2 contact pin

P3 contact pin

P4 contact pin

L-shaped inductor

R1 resistor

R2 resistor

R3 resistor

R4 resistor

R5 resistor

Claims

1. An LED tube for mounting in a luminaire, the LED tube comprising:

-a first pair of contact pins (P1, P2) arranged at a first end of the LED tube (1, 1') and a second pair of contact pins (P3, P4) arranged at a second end of the LED tube (1);

-an array of LEDs (20);

-an LED driver for driving the LED array (20);

-an electrical circuit with a switching means (40,40 ') for switching the LED tube (1) from a first operating state suitable for powering the LED driver from one end of the LED tube via one pair of contact pins to a second operating state suitable for powering the LED tube (1) from both ends via two pairs of contact pins, wherein the switching means (40, 40') is configured to automatically adjust the operating state of the LED tube (1) when the LED tube (1,1 ') is powered from a fixture, wherein the LED tube further comprises a first filament circuit (50) associated with the first pair of contact pins (P1, P2) and a second filament circuit (60) associated with the second pair of contact pins (P3, P4), and wherein the switching means (40, 40') has a first contact (41) connected to the first filament circuit (50), a second contact (42) connected to the LED driver, A third contact (43) connected to the second filament circuit (60), and a contactor (44) configured to contact the second contact (42) with the first contact (41) in the first operating state and to contact the second contact (42) with the third contact (43) in the second operating state.

2. The LED tube according to claim 1, wherein in a first operational state of the LED tube (1, 1'), the second pair of contact pins (P3, P4) is electrically isolated from the first pair of contact pins (P1, P2).

3. The LED tube of claim 1, wherein the first filament circuit (50) is configured as an AC filter.

4. The LED tube according to claim 1, wherein the switch device (40,40 ') has a first control input (95) and a second control input (96) for activating the switch device (40, 40'), and wherein the first control input (95) is electrically connected with the first pair of contact pins (P1, P2) and the second control input (96) is electrically connected with the second pair of contact pins (P3, P4).

5. The LED tube according to claim 1, wherein the switching device (40, 40') has at least one normally closed contact for connecting the LED driver to the first pair of contact pins (P1, P2) and a normally open contact for disconnecting the LED driver from the second pair of contact pins (P3, P4).

6. The LED tube according to claim 1, wherein the switching device (40, 40') is a high impedance switching device.

7. LED tube according to claim 1, wherein the switching device (40, 40') is an electromechanical switching device.

8. An operation method of an LED tube according to any one of claims 1 to 7, the method comprising:

-bringing the LED tube in the first operating state;

-powering the LED tube by a power supply;

-switching said LED tube from said first operating state to said second operating state if it is determined that the operating state suitable for said power supply is not the first operating state of said LED tube.

9. The method of claim 8, wherein in the first operating state, the second pair of contact pins is electrically isolated from the first pair of contact pins.

10. The method of claim 8, further comprising monitoring at least one electrical signal applied to the LED tube, and wherein the operational status of the LED tube suitable for the power supply is determined based on the monitoring of the at least one electrical signal.

11. The method of claim 10, wherein switching the LED tube from the first operating state to the second operating state is accomplished by a switching device activated by the at least one electrical signal applied to the LED tube.

12. The method of claim 10, wherein the at least one electrical signal applied to the LED tube is an electrical signal applied to the first and second pairs of contact pins from both ends of the LED tube.