LED lighting circuit and LED lamp comprising same

Abstract

An LED lighting circuit includes: an LED device including a first LED string (D1,..., D72) having a first tap (20) between two LEDs in the first LED string (D1,..., D72) and a second LED string (D73,..., D144) having a second tap (22) between two LEDs in the second LED string (D73,..., D144), the first LED string and the second LED string being connected in parallel; a power supply device (23) adapted to receive an input power and to provide an output power to the LED device; a bidirectional conduction means (24) connected between the first tap (20) and the second tap (22), the bidirectional conduction means (24) being adapted to be triggered to be conducted when a voltage potential difference between the first tap (20) and the second tap (22) exceeds a threshold, where a current conducted by the bidirectional conduction means (24) is adapted to generate a fault signal at a first detection output (240); and a control circuit (27) connected to the first detection output (240) and adapted to control the power supply device (23) to reduce the output power upon receipt of the fault signal.

Description

Technical Field

[0001] The present invention relates to the field of LED lighting circuits, and in particular to fault protection in LED lighting circuits. Background Art

[0002] In some high-power and compact light engines, up to several hundred LEDs are used to provide high lighting power. In order to prevent the output voltage / LED voltage from being too high (to meet safety regulations), the LEDs are divided into multiple strings connected in parallel, and a large current is provided to drive them. The LED strings are designed / binned to be nominally identical, so the strings will share the current almost evenly. Nominally identical here means that the nominal current, forward voltage, impedance, etc. of the strings are almost the same. Of course, this includes the tolerance of each LED chip. In some applications, the drive current of each LED string is very close to the maximum current limit at which the LED string can operate safely. If one LED in one LED string fails as an open circuit connection, the related string stops working. The current flowing through the string will be distributed among the other strings and may exceed the maximum current limit of the other strings and damage the other strings, causing the entire light engine to fail. Due to high temperatures and stresses in high-power applications, the risk of failures such as open circuits increases due to wire bonding cracks and pad cracks.

[0003] Figure 1 An example is shown: the total current from the driver is 5.2A, and the LEDs are divided into 4 nominally identical strings 1 to 4, each string is allocated 1.3A on average, and each LED has a current of 1.3A flowing through it. The maximum current limit for each LED is 1.5A. If, for example, LED D71 in the LEDs is damaged (open circuit), the string 1 where the damaged LED D71 is located cannot allow any current to flow, and the total current of the string will be distributed by the other 3 strings 2, 3 and 4, that is, each of the other 3 strings will be allocated a current of 1.73A, which exceeds the maximum current limit of 1.5A that the LED string can withstand. This will cause the other 3 LED strings to quickly fail as well.

[0004] US20080157689A1 discloses the use of a bidirectional element that is triggered by an open LED and bypasses the LED. The current is routed to another LED in another string. The problem in this prior art is that the other LED must withstand its original current in its own string as well as the current bypassed from the failed LED in a different string, so it may receive an overcurrent and also fail.

[0005] There are known methods for LED fault detection. For example, the current of each string is sampled by a sense resistor in the string and compared with a threshold via a comparator. If the current is less than the threshold, the string can be considered to be an open circuit fault, and a signal indicating the event will be generated and sent to the driver, which reduces the output current accordingly. However, these known methods inevitably face problems such as affecting efficiency and power supply difficulties. Furthermore, the LED board side is usually isolated from the controller of the driver, so the signal obtained on the LED board side also needs to be level-shifted to the controller of the driver via an isolator.

[0006] EP 2161969 A2 discloses a series connection of a plurality of LED strings, wherein each LED string is connected in parallel with a bypass circuit that senses a fault in the string.

[0007] EP 2390672A2 discloses a bidirectional optical coupler.

[0008] DE 10 2004 032 456 B3 discloses LED circuits connected in parallel, each LED circuit comprising a boost converter and an LED string.

[0009] EP 2763503 A2 and WO 2004068909 A1 disclose LED strings connected in parallel. Summary of the invention

[0010] The invention is defined by the claims.

[0011] The basic idea of ​​the present invention is to provide a bidirectional conductive device across the parallel LED string to sense the change in potential across the string and generate a fault signal if the change is sensed and send the fault signal to a control circuit to reduce the power provided to the string.

[0012] A first aspect of the present invention provides an LED lighting circuit, comprising: an LED device, comprising: a first LED string having a first tap between two LEDs in the first LED string; and a second LED string having a second tap between two LEDs in the second string (D73, ..., D144), the first LED string and the second LED string being connected in parallel; a power supply device, which is suitable for receiving input power and providing output power to the LED device; a bidirectional conduction device, which is connected between the first tap and the second tap, and is suitable for being triggered to conduct when the voltage potential difference between the first tap and the second tap exceeds a threshold, wherein the current conducted by the bidirectional conduction device is suitable for generating a fault signal at a first detection output; and a control circuit, which is connected to the first detection output and is suitable for controlling the power supply device to reduce the output power when the fault signal is received.

[0013] The combination of a bidirectional conduction device and a control circuit provides low cost, low power loss and effective fault protection. For single fault protection when two parallel LED strings are used (it is reasonable to assume that only a single LED string will fail instead of two or more strings), one bidirectional conduction device can monitor both LED strings, so there is no need to provide a corresponding monitoring circuit for each LED string. When the LED string is intact, the bidirectional conduction device is not triggered, so there is no power loss in normal operation of the LED lighting circuit. The fault signal is directly generated from the current conducted by the bidirectional conduction device and sent to the control circuit, and this does not require a separate comparator as in the known method, so the cost is relatively low. Last but not least, the control circuit actively reduces the output power so that the remaining LED string is still working without being powered off, and the LED lighting circuit remains reliably operating.

[0014] In another embodiment, the bidirectional conductive device comprises a current limiting component to limit the current in the bidirectional conductive device to less than 50 mA.

[0015] Since the bidirectional conductive device needs to maintain a fault signal in the event of a fault, the bidirectional conductive device also needs to be protected against faults. This embodiment uses a current limiting current to prevent overcurrent in the bidirectional conductive device, and it increases the reliability of the bidirectional conductive device.

[0016] In another embodiment, the bidirectional conductive device includes an optical coupler having a light emitting side and a light receiving side, the light emitting side being connected between a first tap and a second tap and being suitable for emitting light when the potential between the first tap and the second tap exceeds a threshold value, and the light receiving side being connected to a control circuit as a first detection output and being suitable for generating a fault signal when light emitted by the light emitting side is received.

[0017] Optocouplers are low-cost components that can be triggered by voltage differences and provide level shifting / isolation. In addition, optocouplers have a long operating life to continuously maintain fault signals. The power consumption of optocouplers is also very low, making the power loss in fault protection also low.

[0018] In another embodiment, to emit light from a bidirectional signal, the light emitting side includes a pair of LEDs connected in anti-parallel; or a rectifier circuit and an LED. Bidirectional optocouplers with integrated anti-parallel LEDs are mature off-the-shelf products and are immediately available. Alternatively, a rectifier circuit and an LED may also be used.

[0019] In a low-cost embodiment, the current limiting component comprises a resistor. The resistance of the resistor may be several hundred ohms.

[0020] In one embodiment, the first LED string and the second LED string are connected in parallel to the same output of the power supply and are nominally identical, and the first and second taps are in the same relative position in each respective string.

[0021] In this embodiment, since the LED strings are identical and connected in parallel, and the taps are at the same location, if both LED strings are intact, the voltage potential across the two taps will be essentially zero, otherwise the potentials will be different and can be detected by the bidirectional conduction device.

[0022] In an alternative embodiment, the LED strings may be driven at different outputs of the power supply. For example, a first current regulating circuit powers a first LED string, and a second current regulating circuit powers a second LED string. In this case, in the first instance where both LED strings are intact, the potential across the two LED strings may be different, and the bidirectional conductive device may be designed to tolerate and not respond to the difference; and when one string is disconnected, the potential will also change significantly, and the bidirectional conductive device may be designed to detect / respond to such significant changes and send a fault signal. For example, when both strings are intact, the potential across the two taps may be 3V, and is insufficient to turn on the bidirectional conductive element; when one string is disconnected, the potential increases to 9V, and turns on the bidirectional conductive element.

[0023] In another embodiment, the first tap and the second tap are near the end of the string. Placing the tap and the bidirectional conduction device near the end of the LED string makes the board layout of the circuit easier. The tap and the bidirectional conduction device can also be placed in the middle of the string.

[0024] In another embodiment, the tap and the bidirectional conduction device are at least two LEDs away from the end of the string. In this embodiment, if one LED string is disconnected, the potential between the taps in the LED string is the forward voltage of at least two LEDs, and is therefore sufficient to activate the optocoupler.

[0025] In one embodiment, the LED lighting circuit further comprises a temperature detection device adapted to detect a temperature associated with the LED device and to generate a temperature signal at a second detection output if the temperature exceeds a temperature limit, and the control circuit is further connected to the second detection output and adapted to control the power supply device to reduce the output power based on the temperature signal, wherein the first detection output and the second detection output are connected together and to the control circuit.

[0026] In this embodiment, the LED lighting circuit also includes thermal protection, and the open circuit protection and thermal protection use a single interface to send protection signals to the control circuit. This embodiment has the advantage of low cost because only a single interface is used for the open circuit fault signal and the over-temperature temperature signal.

[0027] In another embodiment, the temperature detection device includes a temperature-dependent resistor thermally coupled to the LED device, an optical coupler having a light emitting side and a light receiving side, the light receiving side being connected to a control circuit as a second detection output, and a power supply circuit suitable for supplying power to the light emitting side of the optical coupler, wherein the temperature-dependent resistor is suitable for deactivating or reducing the output power of the power supply circuit when the temperature exceeds a temperature limit.

[0028] This embodiment provides a low-cost implementation of a temperature detection device based on a temperature-dependent resistor such as an NTC (negative temperature coefficient) or PTC (positive temperature coefficient) resistor thermally coupled to an LED device. For example, the temperature-dependent resistor and the LED device are closely placed on the same PCB, so that the temperature-dependent resistor can reliably detect the temperature of the LED device.

[0029] In another embodiment, the LED lighting circuit includes an LED device and a replica of the bidirectional conductive device connected to each other, and the first detection outputs of the two bidirectional conductive devices are connected together and to the control circuit.

[0030] In this embodiment, four or more LED strings can be divided into different pairs, and each pair has a bidirectional conduction device to detect an open circuit in one of the LED strings in the pair. Since the solution is low-cost and only requires a few components, it is quite easy to scale up the number of LED strings according to actual needs and provide fault detection and protection for these LED strings.

[0031] In addition, the fault signals from the bidirectional conductive device are adapted to be superimposed, and the power supply device is adapted to reduce the output power according to the superimposed fault signal.

[0032] In this embodiment, the superimposed fault signal indicates how many pairs of LED strings have failed, and the power supply device can reduce the output power accordingly. For example, in a two-pair configuration, if the superimposed fault signal indicates that only one string in one pair has failed, the control circuit can control the power supply device to reduce the output power to 75%; and if the superimposed fault signal indicates that both pairs have respective faulty strings, the control circuit can control the power supply device to reduce the output power to 50%. This embodiment intelligently adjusts the output power to match the remaining LED strings and keep them working under nominal operating conditions, avoiding overpowering or underpowering the remaining LED strings.

[0033] In a second aspect of the present invention, there is provided an LED lamp comprising the LED lighting circuit according to the above aspects and embodiments.

[0034] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] For a better understanding of the invention, and in order to more clearly show how the invention may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0036] Figure 1 shows a fault occurring in an LED lighting circuit without fault detection and protection;

[0037] Figure 2 An LED lighting circuit with fault detection and protection according to an embodiment of the present application is shown;

[0038] Figure 3 Shows Figure 2 Operation of the LED lighting circuit when a portion of the first string is disconnected;

[0039] Figure 4 Shows Figure 2 operation of the LED lighting circuit when another portion of the first string is disconnected;

[0040] Figure 5 Shows Figure 2 operation of the LED lighting circuit in when a portion of the second string is disconnected; and

[0041] Figure 6 Shows Figure 2 The LED lighting circuit is operated when another part of the second string is disconnected. DETAILED DESCRIPTION

[0042] The present invention will be described with reference to the accompanying drawings.

[0043] It should be understood that the detailed description and specific examples, although indicating exemplary embodiments of the apparatus, system and method, are for illustrative purposes only and are not intended to limit the scope of the invention. These and other features, aspects and advantages of the apparatus, system and method of the present invention will become better understood from the following description, the appended claims and the accompanying drawings. It should be understood that the drawings are only schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings to represent the same or similar components.

[0044] like Figure 2As shown, the LED lighting circuit includes an LED device, which includes a first LED string including LEDs D1 to D70, D71, D72 and a second LED string including LEDs D73 to D142, D143 and D144. The first LED string includes a tap 20, and the second LED string includes a tap 22. The first LED string and the second LED string are coupled in parallel.

[0045] The power supply device 23 is adapted to receive input power IN and provide output power to the LED device.

[0046] The bidirectional conductive device 24 is connected between the first tap 20 in the first LED string D1 to D72 and the second tap 22 in the second LED string D73 to D144, and the bidirectional conductive device 24 is suitable for being triggered to be turned on when the potential difference between the first tap 20 and the second tap 22 exceeds a threshold value, and the current conducted by the bidirectional conductive device 24 is suitable for generating a fault signal at the first detection output 240.

[0047] The control circuit 27 is connected to the first detection output 240 and is adapted to control the power supply device 23 to reduce the output power when receiving the fault signal.

[0048] The power supply device can be a two-stage power supply, which includes a first PFC stage connected to the AC input and generating a bus voltage, and a second current regulation stage that further converts the bus voltage into a desired output current. The current regulation stage generally has the ability to regulate the output current, and the control circuit 27 can instruct the current regulation stage to reduce the output power / current. The control circuit can be implemented by a discrete circuit or an integrated circuit.

[0049] Preferably, in order to limit the current through the bidirectional conductive component to reduce power loss and prevent damage, the bidirectional conductive device 24 may include a current limiting component to limit the current in the bidirectional conductive device to less than 50 mA. In a low-cost embodiment, the current limiting element is a resistor R1, and its resistance is several hundred ohms, such as 470 ohms.

[0050] In one example, the bidirectional conductive component includes an optical coupler U1 having a light emitting side A-K connected between a first tap 20 and a second tap 22 and adapted to emit light when the potential between the first tap 20 and the second tap 22 exceeds a threshold, and a light receiving side C-E connected to a control circuit 27 as a first detection output 240 and adapted to generate a fault signal when receiving light emitted by the light emitting side A-K. In this embodiment, the light emitting side includes a pair of LEDs connected in anti-parallel so that it responds to a positive or negative (i.e., bidirectional) potential difference between the first tap 20 and the second tap 22. In an alternative embodiment, the anti-parallel LEDs can be replaced by a rectifier circuit and an LED.

[0051] Preferably, the first LED string D1 to D72 and the second LED string D73 to D144 are connected in parallel and are nominally identical, and the first tap 20 and the second tap 22 are in the same relative position in the respective string. In this embodiment, each tap is at the anode of the second to last LED in each string.

[0052] In this embodiment, in addition to open circuit protection, the LED lighting circuit also has over-temperature protection. The LED lighting circuit includes a temperature detection device 26, which is suitable for detecting the temperature associated with the LED device, and if the temperature exceeds the temperature limit, a temperature signal is generated at the second detection output 260, and the control circuit 27 is also connected to the second detection output 260, and is suitable for controlling the power supply device to reduce the output power when the temperature signal is received. In order to minimize the number of connections to the control circuit, since both the fault signal and the temperature signal are used to trigger the protection to reduce the output power, the two signals can be mixed, and the first detection output 240 and the second detection output 260 are connected together and connected to the control circuit. Figure 2 In the circuit, the first detection output 240 and the second detection output 260 are connected to the NTC+ and NTC− terminals of the control circuit 27 .

[0053] Regarding over-temperature protection, the temperature detection device 26 includes: a temperature-dependent resistor R_NTC; an optocoupler U3 having a light emitting side A-K and a light receiving side C-E connected to the control circuit 27 as a second detection output 260; and a power supply circuit R5, which is suitable for supplying power to the light emitting side of the optocoupler U3, wherein when the temperature exceeds the temperature limit, the temperature-dependent resistor R_NTC is suitable for optionally activating the power supply circuit via a comparison circuit including TL431 U4.

[0054] More specifically, resistor R8 can set the temperature limit, capacitor C1 is a negative feedback capacitor, resistors R5, R6 are current limiting resistors, and resistor R7 is the power supply for the comparison circuit U4.

[0055] The description will first explain the thermal protection and then the open circuit protection, which notifies the control circuit via the same output used by the thermal protection. When the temperature of the LED board carrying the LED device increases, the temperature of the resistor R_NTC increases, while the resistance of the resistor R_NTC decreases, and the voltage at the electrode 2 of the comparator U4 increases. When the voltage rises to 2.5V, the comparator U4 closes its electrodes 1 and 3, which causes U3 to be powered and the impedance of the illumination receiving side C-E of the optocoupler U3 is reduced, thereby reducing the voltage at the second detection output 260. The control circuit 27 detects the reduced resistance value of U3_CE+R6 to R6, or detects the reduced voltage on the second detection output 260, and controls the power supply device 23 to reduce the output power / current, thereby preventing further overtemperature.

[0056] As for open circuit protection, Figure 3 It shows how the bidirectional conduction device works.

[0057] For example, for startup, both the first LED string and the second LED string are intact as a normal operating state. Assume that the total output current is 5.2A and the current through each parallel string is 1.3A. Because the forward voltage difference of the LEDs D71+D72 in the first LED string and the LEDs D143+D144 in the second LED string is substantially zero or very small, the potential across the first tap 20 and the second tap 22 is almost zero, and the optocoupler U1 cannot work. The bidirectional conduction device does not output a fault signal to the first protection output terminal 240. The control circuit 27 does not receive the fault signal and does not control the power supply device 23 to reduce the output power / current.

[0058] exist Figure 3 In the embodiment, when any LED in D1-D70 of the first LED string D1-D72 is disconnected as shown by the cross icon, the output voltage of the power supply device is applied to the series connection of LEDs D73-D142, optocoupler U1, resistor R1, and LEDs D71 and D72. In other words, the voltage of LEDs D143 and D144 is applied to optocoupler U1, resistor R1, and LEDs D71 and D72. At this time, the optocoupler U1 and LEDs D71 and D72 will be more or less turned on and current will flow, LEDs D71 and D72 are in low current conduction, and the voltage difference on the K-A terminals of the optocoupler U1 makes U1 work and reduces the impedance of the C-E terminals of U1. The voltage on the first protection output 240 is reduced, and the reduced voltage is sent to the control circuit 27 through R2 as a fault signal. The control circuit 27 controls the power supply device 23 to reduce the total output current from, for example, 5.2A to 3.9A, so that the LED currents in the LED strings 2, 3, and 4 are restored to 1.3A.

[0059] exist Figure 4 In the example, when any LED of D71-D72 in the first LED string D1-D72 is disconnected as shown by the cross icon, the output voltage of the power supply device 23 is applied to the LEDs D1 to D70, the resistor R1, the optocoupler U1, and the LEDs D142 and D144. At this time, the optocoupler U1 will be more or less turned on and current will flow, and the voltage difference on the A-K terminals of the optocoupler U1 makes U1 work and reduces the impedance of the C-E terminals of U1. The voltage on the first protection output 240 is reduced, and the reduced voltage is sent to the control circuit through R2 as a fault signal. The control circuit controls the power supply device 23 to reduce the corresponding total output current to, for example, 3.9A, so that the LED current in strings 2, 3 and 4 is restored to 1.3A.

[0060] The bidirectional conduction arrangement can also monitor the fault of another string. Figure 5 In the example, when any LED of D143-D144 in the second LED string D74-D144 is disconnected as shown by the cross icon, the output voltage of the power supply device 23 is applied to the LEDs D73 to D142, the optocoupler U1, the resistor R1, and the LEDs D71 and D72. At this time, the optocoupler U1 will be more or less turned on and current will flow, the voltage difference on the K-A terminals of the optocoupler U1 makes U1 work, and the impedance of the C-E terminals of U1 is reduced. The voltage on the first protection output 240 is reduced, and the reduced voltage is sent to the control circuit 27 through the resistor R2 as a fault signal. The control circuit 27 controls the power supply device 23 to reduce the total output current to, for example, 3.9A, so that the LED current in the strings 1, 3 and 4 is restored to 1.3A.

[0061] exist Figure 6 In the embodiment, when any LED in the second LED string D73-D142 is disconnected as shown by the cross icon, the output voltage of the power supply device 23 is applied to the LEDs D1-D70, the resistor R1, the optocoupler U1, and the LEDs D143 and D144. In other words, the voltage of the LEDs D71 and D72 is applied to the resistor R1, the optocoupler U1, and the LEDs D143 and D144. At this time, the optocoupler U1 and the LEDs D143 and D144 are more or less turned on and current flows, the LEDs D143 and D144 are in low current conduction, and the voltage difference on the A-K terminals of the optocoupler U1 causes U1 to operate, and the impedance of the C-E terminals of U1 is reduced. The voltage on the first protection output terminal 240 is reduced, and the reduced voltage is sent to the control circuit 27 through the resistor R2 as a fault signal. The control circuit 27 controls the power supply device 23 to reduce the total output current from, for example, 5.2A to 3.9A, so that the LED currents in the LED strings 1, 3, and 4 are restored to 1.3A.

[0062] Assuming a single fault condition for the parallel strings of LEDs D1 to D72 and LEDs D73 to D144, in other words, the present embodiment can monitor and protect against a single fault in the two strings while ignoring the situation where both strings fail.

[0063] Preferably, the LED lighting circuit includes a replica of the LED device and the bidirectional conductive device. The first LED string of the replica is D145 to D216, and the second LED string of the replica is D217 to D288. The bidirectional conductive device 24' is a replica. The operation of the bidirectional conductive device 24' when monitoring and protecting any one of the two LED strings D145 to D216 and D217 to 288 is similar to the above.

[0064] In the event that one of the LED strings D1 to D72 and D73 to D144 and one of the strings D145 to D216 and D217 to D288 fails, both bidirectional conductive components 24 and 24' are triggered, and the impedance of the C-E terminals of the optocouplers U1 and U2 becomes low impedance, and the voltage at the detection output 240 / 240' is further reduced to a level lower than when only one of the four strings fails. The control circuit 27 can sense this lower level and will control the power supply device 23 to reduce the output power / current to an even lower value, such as 2.6A, so that the LED current in the two remaining LED strings is restored to 1.3A.

[0065] By studying the drawings, the disclosure and the appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0066] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0067] If the term "suitable for" is used in the claims or description, it should be noted that the term "suitable for" is intended to be equivalent to the term "configured to". If the term "arranged" is used in the claims or description, it should be noted that the term "arranged" is intended to be equivalent to the term "system" and vice versa.

[0068] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. An LED lighting circuit, comprising: An LED device, comprising a first LED string (D1, ..., D72) having a first tap (20) and a second LED string (D73, ..., D144) having a second tap (22), wherein the first tap (20) is located between two LEDs in the first LED string (D1, ..., D72), and the second tap (22) is located between two LEDs in the second LED string (D73, ..., D144), wherein the first LED string and the second LED string are connected in parallel; A power supply device (23) adapted to receive input power and provide output power to the LED device; a bidirectional conductive device (24) connected between the first tap (20) and the second tap (22) and adapted to be triggered to conduct when a voltage potential difference between the first tap (20) and the second tap (22) exceeds a threshold, wherein a current conducted by the bidirectional conductive device (24) is adapted to generate a fault signal at a first detection output (240); as well as A control circuit (27) is connected to the first detection output (240) and is adapted to control the power supply device (23) to reduce the output power when receiving the fault signal. 2 . The LED lighting circuit according to claim 1 , wherein the bidirectional conductive device comprises a current limiting component to limit the current in the bidirectional conductive device to less than 50 mA.

3. The LED lighting circuit according to claim 1 or 2, wherein the bidirectional conductive device comprises: an optical coupler having a light emitting side and a light receiving side, the light emitting side being connected between the first tap and the second tap and being adapted to emit light when the potential between the first tap and the second tap exceeds the threshold value; The light receiving side is connected to the control circuit as the first detection output and is adapted to generate the fault signal upon receiving light emitted by the light emitting side; The light emitting side comprises: A pair of LEDs connected in anti-parallel; or Rectifier circuit and an LED. The LED lighting circuit according to claim 2 , wherein the current limiting component comprises a resistor.

5. The LED lighting circuit of claim 1, wherein the first LED string (D11, ..., D72) and the second LED string (D73, ..., D144) are nominally identical, and the first tap and the second tap are in the same relative position in the respective strings.

6. The LED lighting circuit of claim 5, wherein the first tap and the second tap are near an end of the string, optionally at least two LEDs away from the end of the string.

7. The LED lighting circuit according to claim 1, further comprising: temperature detection means adapted to detect a temperature associated with said LED arrangement and to generate a temperature signal at a second detection output if said temperature exceeds a temperature limit, and The control circuit is also connected to the second detection output and is adapted to control the power supply device to reduce the output power when receiving the temperature signal. The first detection output and the second detection output are connected together and connected to the control circuit.

8. The LED lighting circuit according to claim 7, wherein the temperature detection device comprises: a temperature dependent resistor (R_NTC) thermally coupled to the LED device, an optical coupler (U3) having a light emitting side and a light receiving side, the light receiving side being connected to the control circuit as the second detection output, and a power supply circuit adapted to supply power to the light emitting side of the optical coupler (U3), Wherein the temperature dependent resistor (R_NTC) is adapted to activate the power supply circuit when the temperature exceeds the temperature limit.

9. The LED lighting circuit according to claim 1, 7 or 8, further comprising duplicates of the LED device and the bidirectional conductive device connected to each other, and The first detection outputs of the two bidirectionally conductive devices are connected together and connected to the control circuit.

10. The LED lighting circuit according to claim 9, wherein the fault signals from the bidirectional conductive device are suitable for being superimposed, and the power supply device is suitable for reducing the output power according to the superimposed fault signals.

11. An LED lamp, comprising the LED lighting circuit according to any one of claims 1 to 10.

Images