Light emitting diode (LED) based lighting device having circuit for detecting the presence of a human body in contact with a live voltage

Abstract

A lighting device based on a light emitting diode (LED) is arranged to be connected to an alternating current (AC) mains power supply, the lighting device comprising: a zero-crossing detection module arranged to detect a zero-crossing in an AC voltage supplied by the AC mains power supply; a detection pulse module arranged to provide a detection pulse based on the detected zero-crossing; a human body detection module arranged to determine: a current drawn from the AC mains power supply during the provided detection pulse, and to determine the presence of a human body based on the determined current; wherein the detection pulse module is arranged to provide the detection pulse during a rising positive edge of the AC voltage.

Description

Technical Field

[0001] The present disclosure relates to LED-based lighting devices having circuits for detecting human presence, and more particularly to detecting human presence in a power loop. Background Art

[0002] Fluorescent TL tubes are inherently safe because the gas inside the tube must first be ignited before there is a conductive path between the two ends of the tube. This safety is necessary when the tube is installed into a fixture while the lamp holder is energized. In this case, for example, when one end of the tube is plugged into a socket and energized while the other end is not energized, the pins on the free ends should not have a dangerous live voltage.

[0003] With gas-filled fluorescent tubes, this is not a problem. However, when using a retrofitted light-emitting diode (LED) tube, there is a conductive path between the two ends of the tube. When the pins are touched by a person, the internal LED driver tends to conduct current and begin to operate, which often exceeds safety limits and causes a shock hazard.

[0004] For example, the problem can be solved by isolating one side of the TLED from the mains. But in such a solution, the glow starter of the tube must be replaced by a short circuit to make the lamp work. Another known solution to such a problem is to adopt a single-ended input scheme for the TLED. However, such a tube is related to the direction in which the TLED is installed, and the person installing the TLED should be aware of this. In addition, single-ended TLEDs are only popular in certain areas of the world. Single-ended TLEDs can be converted to double-ended TLEDs, but additional circuits or components need to be added, which increases the complexity and cost of the TLED. This is undesirable.

[0005] Another commercially available TLED is a double-terminal TLED, in which the TLED can be installed in any physical orientation. Such a configuration exposes the installer to the risk of electric shock caused by leakage current when the person installing the tube comes into contact with one of the pins during installation. A known solution is to install an additional electrical safety switch inside the TLED, thereby preventing the flow of current before the TLED is correctly installed. Such a solution also involves additional components and thus increases the cost of the TLED.

[0006] Therefore, a solution is needed that ensures safety while not increasing the cost of the equipment. Summary of the invention

[0007] It would be advantageous to implement a light emitting diode (LED) based lighting device arranged for detecting the presence of a human body in a power loop.

[0008] In order to better solve one or more of these problems, in a first aspect of the present disclosure, there is provided a light emitting diode (LED) based lighting device, the light emitting diode (LED) based lighting device being arranged for connection to an alternating current (AC) mains power supply, the lighting device comprising:

[0009] - a zero crossing detection module arranged for detecting a zero crossing in the AC voltage supplied by said AC mains power supply;

[0010] - a detection pulse module arranged for providing a detection pulse based on said detected zero crossing;

[0011] a human body detection module arranged for determining: a current drawn from said AC mains supply during said detection pulse provided, and for determining the presence of a human body based on said current determined,

[0012] Wherein the detection pulse module is arranged for providing the detection pulse after the detected zero crossing.

[0013] The detection pulse module may thus be arranged for providing the detection pulse during a positive rising edge of the rectified AC voltage.Preferably, the detection pulse starts at the same time as a zero crossing is detected.

[0014] The above principles relate to LED-based lighting devices, and more specifically to double-ended LED-based lighting devices. Here, it may be necessary to perform human body model detection before the LED-based lighting device is actually turned on. This ensures that the installation of the LED-based lighting device can be performed safely.

[0015] Such functionality may be embodied in a pin safety detection circuit that proves the presence of a human body after AC mains power is applied. In the event that mains power is detected and no human presence is detected, a driver in the LED-based lighting device is enabled to turn on the LED-based lighting device.

[0016] The presence of a human body in the power loop can be detected by measuring the mains impedance. When the mains voltage reaches a certain threshold, current is drawn from the mains supply. Based on the peak value of the mains current, it can be inferred whether a human body is present. That is, if the peak value is much lower than expected, a human body may be present in the power loop. Such a detection test can be performed once or several times before enabling the driver.

[0017] One of the advantages of the present disclosure is that it enables a large number of LED-based lighting devices to be connected to one circuit breaker and still be able to successfully perform human detection. This will be explained in more detail with reference to the accompanying drawings.

[0018] One aspect of the present invention is to measure the current during a detection pulse. The detection pulse is provided by a detection pulse module.

[0019] In any case, two scenarios can be compared. The first scenario involves the concept of a human body not being present. The second scenario involves the concept of a human body actually being present in the power loop. Obviously, for the second scenario, the total impedance perceived in the power loop is higher, since the human body can be modeled by a relatively large impedance.

[0020] The effect of the above is that the current drawn from the AC mains may be different in the two scenarios. The current drawn in the first scenario may be higher than the current in the second scenario. The ratio between the currents in the two scenarios can be said to be related to the accuracy with which the presence of a human body can be detected.

[0021] One of the inventors' understandings is that it is beneficial when the detection pulse is after a zero crossing of the AC mains voltage. In case the detection pulse is after a zero crossing, the ratio between the two measurement currents mentioned above can be improved.

[0022] In one embodiment, the LED-based lighting device further comprises:

[0023] - a mains peak detection module, arranged to detect a peak voltage of said AC voltage,

[0024] And wherein the detection module is further arranged to determine the duration of the detection pulse based on the detected peak voltage.

[0025] The inventors have found that in order to improve the accuracy of the detection process, the detection pulse may be adjusted depending on the applied AC mains (eg 277 Vac or 120 Vac).

[0026] In one example, the human body detection module is arranged to determine the presence of the human body based on:

[0027] - a determined ratio between said current and a predetermined current.

[0028] The predetermined current may be the current drawn from the AC mains when no human body is present in the power loop. This may thus form some kind of calibration current. If the determined current is much lower than the calibration current, it may be inferred that a human body is present in the power loop. In this way, the ratio between the determined current and the predetermined current may form an input for determining whether a human body is present.

[0029] In another example, the LED-based lighting device further includes:

[0030] - a current limiter arranged to ensure a constant current drawn from said AC mains supply during said detection pulse provided.

[0031] During the duration of the detection pulse, the current drawn from the AC mains may vary. During the duration of the detection pulse, the amount of current drawn from the AC mains may increase. This makes the process of detecting a human body less accurate. A current limiter may ensure that the current drawn during the detection pulse remains constant so that accuracy may be improved.

[0032] In yet another example, the detection pulse module is arranged for providing a calibration pulse, wherein an end of the calibration pulse and a start of the detection pulse both correspond to the detected zero crossing.

[0033] Wherein the human detection module is further arranged to determine: the current drawn from the AC mains power supply during the calibration pulse provided, and wherein the current limiter is further arranged to ensure: no current is drawn from the AC mains power supply during the calibration pulse provided.

[0034] In another example, the human body detection module is further arranged to measure a voltage of the AC mains when the calibration pulse starts, and determine the presence of a human body based on the measured voltage.

[0035] The above examples can be summarized as follows. In order to eliminate or reduce the effect of the series inductance of the cable line present between the mains and the LED-based lighting device, and even with the large inductance of the EM ballast, it may be necessary to ensure that the current is constant during the measurement. This is achieved by using a current limiter as described above.

[0036] It has also been found that in order to accurately measure the resistance of the entire chain, i.e. the resistance of the cable and the resistance of the human body (if present), the falling slope of half a cycle of the time it takes for the sine wave to go from the trigger voltage to zero volts (and therefore no current flowing during that particular time) without the current limiter being turned on can be measured. At the rising slope, i.e. just after zero volt detection, the current limiter can be turned on again.

[0037] The difference between the no-load mains and the loaded mains can then be determined. The current through the current limiter is also known. The current is stable and equal to a specific set current such that the voltage across the series inductor is equal to zero. The resistance of the current loop can then be determined.

[0038] In another example, the calibration pulse has the same duration as the detection pulse.

[0039] In a second aspect of the present disclosure, there is provided a method of determining the presence of a human body by a light emitting diode (LED) based lighting device according to any of the examples provided above.

[0040] The method comprises the following steps:

[0041] - detecting a zero crossing of the AC voltage supplied by the AC mains by means of the zero crossing detection module;

[0042] - providing, by the detection pulse module, the detection pulse based on the detected zero crossing;

[0043] - determining, by the human body detection module, the current drawn from the AC mains power supply during the provided detection pulse, and determining the presence of the human body based on the determined current;

[0044] Wherein the detection pulse module is arranged for providing the detection pulse after the detected zero crossing.

[0045] Note that the advantages and definitions disclosed with respect to the embodiments of the first aspect of the present invention also correspond to the embodiments of the second aspect of the present invention, ie the method of determining the presence of a human body in a power loop.

[0046] In one example, the LED-based lighting device further comprises a mains peak detection module arranged to detect a peak voltage of the AC voltage, and wherein the method further comprises the following steps:

[0047] - Determining, by the detection module, the duration of the detection pulse based on the detected peak voltage.

[0048] In another example, the human body detection module is arranged to determine the presence of the human body based on:

[0049] - a determined ratio between said current and a predetermined current.

[0050] In another example, the LED-based lighting device further includes:

[0051] - a current limiter arranged to ensure a constant current drawn from said AC mains supply during said detection pulse provided.

[0052] In yet another example, the detection pulse module is arranged for providing a calibration pulse, wherein an end of the calibration pulse and a start of the detection pulse both correspond to the detected zero crossing.

[0053] Wherein the human detection module is further arranged to determine: the current drawn from the AC mains power supply during the calibration pulse provided, and wherein the current limiter is further arranged to ensure: no current is drawn from the AC mains power supply during the calibration pulse provided.

[0054] In another example, the method further comprises the following steps:

[0055] - by means of the human body detection module, at the start of the calibration pulse, measuring the voltage of the AC mains, and determining the presence of a human body based on the measured voltage.

[0056] In one example, the calibration pulse has the same duration as the detection pulse.

[0057] In a third aspect of the present disclosure, a computer program product is provided, comprising a computer-readable medium having instructions stored thereon, which instructions, when executed by a light emitting diode (LED)-based lighting device, cause the LED-based lighting device to implement a method according to any example provided above.

[0058] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 An LED-based lighting device according to the prior art is shown;

[0060] Figure 2 Another LED-based lighting device according to the prior art is shown, wherein the LED-based lighting device includes a pin safety circuit;

[0061] Figure 3 A mains power supply system having a plurality of LED-based lighting devices cascaded in parallel is shown;

[0062] Figure 4 A simulation circuit illustrating the concepts of the present disclosure is shown;

[0063] Figure 5 shows building blocks of an integrated circuit IC arranged to perform the method according to the present disclosure;

[0064] Figure 6 shows a graph utilizing a calibration pulse and a detection pulse;

[0065] Figure 7 Another graph utilizing a calibration pulse and a detection pulse is shown. DETAILED DESCRIPTION

[0066] Figure 1 An LED based lighting device 1 according to the prior art is shown.

[0067] Figure 1Possible scenarios during installation of different types of tubes are illustrated. As indicated by reference numeral 1, fluorescent TL tubes are intrinsically safe because the gas inside the tube 6 must first be ignited before there is a conductive path between the two ends of the tube. The tube 6 is connected to an alternating AC mains voltage supply 4, such as is common in domestic buildings. The tube 6 or the fixture in which the tube 6 is mounted may include additional elements, such as a ballast 5 and a jumper or starting element 9.

[0068] This safety is necessary when the tube 6 is mounted in the fixture and the lamp holder is powered (ie mains voltage is present). When one end of the tube is plugged into a socket and powered and the other end is not powered, the pins at the free end should not be live.

[0069] For gas filled fluorescent tubes such as 6 this is not a problem, but when LED lighting 7 is used there is a conductive path between the ends of the tube as shown at 2. When the pins are touched by a person 10, i.e. a human body is present in the power loop, the internal LED driver tends to conduct current which often exceeds safety limits and causes a shock hazard.

[0070] A known solution to this problem is to apply the mains input only on one side of the tube as indicated by reference numeral 3. The other side is thus electrically isolated from the mains 4. In this case there is no conducting path between the two sides of the tube, but the glow starter must be replaced by a short circuit 9 for the lamp 8 to operate.

[0071] Figure 2 A single-ended tube 20 and a double-ended tube 21 known from the prior art are schematically illustrated. Since a TLED has four input terminals, there are two main input schemes on the market: single-ended 20 and double-ended 21. The double-ended input scheme is unsafe unless pin safety measures are taken inside the lamp. The single-ended tube 20 includes two sets of terminals 22, 25. Internal components such as a driver 23 and a light emitting diode LED array 24 are connected to only one set of terminals 22.

[0072] Therefore, a disadvantage of a single ended input is that the installer needs to be aware of which of the two sets of terminals 22, 25 should be connected to the mains 4 and then install the lamp accordingly. If the lamp is installed incorrectly, the lamp will not light up.

[0073] To solve this problem, a single-ended input tube can be made orientation independent by adding a jumper (not shown). In this way, the lamp will only work in either installation. However, adding a jumper increases cost.

[0074] As is apparent from reference numeral 21, the two-terminal tube can operate regardless of the orientation in which it is installed, since the two sets of terminals 26, 29 are short-circuited internally and connected to internal components such as the driver 27 and the LED array 28. However, during installation, for example, if the terminal 26 is inserted first, a person (i.e., a human body) who comes into contact with the terminal 29 is at risk of receiving an electric shock, because the other end 29 is not electrically insulated from the first end 26.

[0075] The present disclosure relates to the introduction of a pin safety circuit, which is arranged to detect the presence of a human body in a power loop based on measured impedance. When the mains voltage reaches a certain threshold, a current can be drawn from the mains voltage 4. Based on the peak value of the current, it can be inferred whether a human body is present. In other words, if the peak current is much smaller than the expected value, it can be inferred that a human body is present in the power loop.

[0076] One of the advantages of the present disclosure relates to a system 31 wherein Figure 3 As shown, a single mains power supply 34 is arranged to supply power to a plurality of LED based lighting devices 32, 33 cascaded in parallel.

[0077] By turning on multiple LED-based lighting devices at the same time, the ramp-up of the received current can be reduced. The mains power supply can sense a large inductor, i.e., a collective inductor that simulates multiple LED-based lighting devices (AC source inductance multiplied by the number of parallel lamps). This may cause each LED-based lighting device to falsely detect a human body. In other words, each LED-based lighting device can detect this reduced current, which can be similar to a human body present in the power loop. However, in this particular scenario, the reduced current is caused by the parallel-cascaded LED-based lighting devices, rather than by the presence of a human body in the power loop.

[0078] The above also Figure 4 Instructions, Figure 4 An analog circuit 41 is shown illustrating the concepts of the present disclosure. Figure 4 Thus an equivalent circuit is shown when utilizing multiple parallel cascaded LED based lighting devices.

[0079] Here, the mains voltage is indicated with reference numeral 46 , the human body is indicated with reference numeral 45 , and the LED-based lighting device is indicated with reference numeral 42 .

[0080] Impedance 44 and inductor 43 are provided, which simulate the AC source impedance and the presence of multiple LED-based lighting devices. In other words, the value of impedance 44 can correspond to N times the output resistance of the mains power supply, where N is related to the number of LED-based lighting devices. The value of inductor 43 can correspond to N times the output inductance of the mains power supply, where N is related to the number of LED-based lighting devices.

[0081] From the above, it should be apparent that the current received by the LED-based lighting device 42 (ie, the ramp-up) is also related to the number of LED-based lighting devices in the system.

[0082] According to the present disclosure, an LED-based lighting device 42 includes:

[0083] - a zero crossing detection module arranged for detecting a zero crossing in the AC voltage supplied by said AC mains power supply;

[0084] - a detection pulse module arranged for providing a detection pulse based on said detected zero crossing;

[0085] a human body detection module arranged for determining: a current drawn from said AC mains supply during said detection pulse provided, and for determining the presence of a human body based on said current determined,

[0086] Wherein the detection pulse module is arranged to provide the detection pulse after the detected zero crossing.

[0087] The inventors have found that detecting the presence of a human body in the power loop of the system should be performed after a detected zero crossing, for example at a rising positive edge of the received AC mains voltage. This increases the accuracy of determining the presence of a human body.

[0088] Figure 5 shows building blocks of an integrated circuit IC 51 arranged for performing the method according to the present disclosure;

[0089] The IC may have a zero crossing detection module 52 arranged for detecting zero crossings in the AC voltage provided by the AC mains supply.

[0090] The IC may further include a voltage generating circuit 55 for generating power required for normal operation of the IC.

[0091] Furthermore, a mains peak detection and a pulse width timer may be provided as indicated with reference numerals 54 and 53 .

[0092] It is found that the voltage level of the AC mains voltage, such as 277V or 120V, may have an effect on the width of the detection pulse. Therefore, the mains peak detection circuit 54 can determine the voltage of the received AC mains voltage and can then command the pulse width timer 53 to set a specific pulse width for the detection pulse.

[0093] The pulse width timer may then provide a detection pulse to the human detection module 56 based on the detected zero crossing.

[0094] Figure 6 A graph using a calibration pulse and a detection pulse is shown.

[0095] Figure 6 A further improvement of the above detection method is disclosed.The resistance of the HBM can be measured more accurately so that accurate results can be obtained even in the case of high bulk series inductances, such as are present in EM ballasts.

[0096] It is further improved to place longer cables and very large number of LED-based lighting devices in parallel and it can still successfully perform human presence detection.

[0097] Type B TLED lamps (eg, having mains connections at both ends) may require a mains test to be performed before switching on to ensure safe installation.

[0098] The detection method may utilize narrow detection pulses. Mains inductance, such as cables, transformers, may have a major influence on the rate of rise of the detection current, and its influence increases with the number of lamps connected in parallel. Therefore, the maximum number of lamps that can be connected in parallel may be limited.

[0099] Figure 6 Two further enhancements of the proposed method are involved.

[0100] 1. When the voltage measurement takes place, the influence of the mains cable inductance and the EM ballast inductance is eliminated or reduced by ensuring that the sense current is constant. To this end, a current limiting circuit, i.e., a current limiter, can be introduced.

[0101] 2. The line resistance can be measured by measuring the voltage difference across the current limiter when the detection current is not drawn and when the detection current is drawn, that is, the line resistance is equal to (Vunloaded-Vloaded) / I. In the absence of detection current, the voltage Vunloaded across the current limiter is equal to the mains.

[0102] This level is predefined and equal to Vtriggertrack. In order to ensure that the voltage Vloaded is measured at the correct moment within the mains half-cycle, the dual slope principle can be implemented when the detection current is drawn. That is, a timer is used to measure the time interval from the moment when the mains crosses the level Vtrigger until the mains falling slope (i.e., the first slope) of the zero crossing. Then, the same timer can be used to set the length of the detection pulse (i.e., the second slope), and the detection pulse is generated after the mains zero crossing. In this way, the detection pulse ends at the moment when the rising slope of the unloaded mains crosses Vtrigger. The voltage Vloaded is measured at the end of the detection pulse. As described in point 1, the influence of line inductance is eliminated by ensuring that the detection current is constant at the end of the detection pulse.

[0103] Note that once the current change is zero, i.e., constant current, there is no voltage drop across the series inductance, so the voltage drop is only resistive, which is equal to the human body resistance plus the series resistance of the wiring. Voltage drop can be measured using constant current.

[0104] Preferably, the measurement time from Vtrigger to zero volts (ie the calibration pulse) may be equal to the detection pulse. This may be achieved in a number of ways.

[0105] With analog circuits, the dual slope principle can be used, where the same time as the measurement time from Vtrigger to 0V and the rising voltage is generated, during this time slot the voltage can be measured and the voltage drop can be determined with a constant current limiter.

[0106] A digital counter is used which generates the same time in the rising slope as the measurement time from Vtrigger to 0V for detecting the voltage.

[0107] Figure 7 Another graph 61 is shown where a calibration pulse and a detection pulse are used.

[0108] Here, reference numerals 62, 63 and 64 relate to timers for detecting pulses. Reference numeral 64 is a timer which increases until the end of the platform. Reference numeral 63 decreases the timer 62 from the platform to zero.

[0109] The corresponding currents are indicated with reference numerals 65, 66 and 67. Here, the current is shown increasing to a region with a constant current as indicated by reference numeral 65. The voltage is then measured at the end of the detection pulse as indicated by reference numeral 66. The current then decreases with a slow slope as indicated by reference numeral 67 to avoid high di / dt.

[0110] In any of the above-mentioned pin safety circuits or detection methods, a stable mains voltage is assumed. In the case of unstable mains voltage (e.g., voltage fluctuations between each mains cycle exceed a threshold), measurement may lead to misunderstanding of the measurement result. As a precaution, the detection of the detection pulse can be postponed until the detection of a stable mains is established. This can be achieved, for example, by sampling several mains cycles (e.g., three or more cycles) and comparing the voltage difference between these cycles. When the difference is within an acceptable threshold, the pin safety circuit or detection method can be activated or executed.

[0111] In addition to or as an alternative to any of the above-described pin safety circuits or detection methods, compensation for the nonlinear behavior of diodes present in LED-based lighting devices (e.g., diodes in rectifier circuits) may be introduced. Instead of drawing no current from the AC mains during the calibration pulse, a small current may be drawn. This current is less than the current drawn during the detection pulse. Even when a small current is drawn, the voltage drop across the diode remains relatively stable due to the nonlinear voltage-current characteristic behavior of the diode. If more current is drawn with the aid of the diode, the voltage will change with a delay, but not as significantly as at the moment when a very small current is drawn to when no current is drawn. Therefore, the nonlinear effect of the diode affecting the measurement will be significantly reduced.

[0112] By studying the drawings, the disclosure and the appended claims, those skilled in the art can understand and implement other variations of the disclosed embodiments when practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "an" or "a" does not exclude a plurality. A single processor or other unit can implement the functions of several items recorded in the claims. The fact that certain measures are recorded in mutually different dependent claims does not mean that a combination of these measures cannot be used advantageously. The computer program can be stored / distributed on an appropriate medium, such as an optical storage medium or solid-state medium provided with or as part of other hardware, but can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems. Any figure mark in the claims should not be interpreted as limiting its scope.

Claims

1. A lighting device (1) based on a light emitting diode (LED), arranged to be connected to an alternating current (AC) mains power supply, comprising: - a zero crossing detection module (52) arranged for detecting a zero crossing in the AC voltage supplied by said AC mains power supply; - a detection pulse module arranged for providing a detection pulse based on said detected zero crossing; - a human body detection module (56) arranged for determining the current drawn from said AC mains power supply during said detection pulse provided, and for determining the presence of a human body based on said determined current; as well as - a current limiter arranged to ensure a constant current drawn from said AC mains supply during said detection pulse provided, wherein the detection pulse module is arranged for providing the detection pulse after the detected zero crossing, wherein the detection pulse module is arranged for providing a calibration pulse, wherein both the end of the calibration pulse and the start of the detection pulse correspond to the detected zero crossing, The human body detection module (56) is further arranged to determine the current drawn from the AC mains power supply during the calibration pulse provided, and the current limiter is further arranged to ensure that during the calibration pulse provided, no current is drawn from the AC mains power supply, or a current lower than the current drawn during the detection pulse is drawn from the AC mains power supply.

2. The LED-based lighting device (1) according to claim 1, wherein the LED-based lighting device further comprises: - a mains peak detection module (54) arranged to detect a peak voltage of said AC voltage, And wherein the mains peak detection module (54) is further arranged to determine the duration of the detection pulse based on the detected peak voltage.

3. The LED-based lighting device (1) according to claim 1, wherein the human body detection module (56) is arranged to determine the presence of the human body based on: - A ratio between the determined current and a predetermined current.

4. The LED-based lighting device (1) according to claim 2, wherein the human body detection module (56) is arranged to determine the presence of the human body based on: - A ratio between the determined current and a predetermined current.

5. The LED-based lighting device (1) according to claim 1, wherein: No current is drawn from the AC mains supply during the calibration pulse provided, wherein the human body detection module (56) is further arranged for measuring the voltage of the AC mains supply at the start of the calibration pulse and for determining the presence of a human body based on the measured voltage.

6. The LED-based lighting device (1) according to any one of claims 1 to 5, wherein the calibration pulse has the same duration as the detection pulse.

7. The LED based lighting device (1) according to any one of claims 1 to 5, wherein the detection of the detection pulse is postponed until the detection of a stable AC mains power supply is established.

8. A method for determining the presence of a human body by means of a lighting device (1) based on a light emitting diode (LED) according to any one of claims 1 to 6, wherein the method comprises the following steps: - detecting, by means of the zero crossing detection module (52), a zero crossing in the AC voltage supplied by the AC mains power source; - providing, by the detection pulse module, the detection pulse based on the detected zero crossing; - determining, by means of the human body detection module (56), the current drawn from the AC mains power supply during the provided detection pulse, and determining the presence of the human body based on the determined current; Wherein the detection pulse module is arranged to provide the detection pulse after the detected zero crossing.

9. The method according to claim 8, wherein the LED-based lighting device (1) further comprises a mains peak detection module (54), the mains peak detection module being arranged for detecting a peak voltage of the AC voltage, and wherein the method further comprises the following steps: - Determining the duration of the detection pulse based on the detected peak voltage by the mains peak detection module (54).

10. The method according to any one of claims 8 to 9, wherein the human body detection module (56) is arranged to determine the presence of the human body based on: - A ratio between the determined current and a predetermined current.

11. The method according to claim 10, wherein the method further comprises the following steps: - measuring the voltage of the AC mains power supply at the beginning of the calibration pulse by the human body detection module (56) and determining the presence of a human body based on the measured voltage.

12. The method of claim 11, wherein the calibration pulse has the same duration as the detection pulse.

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