LED LIGHTING SYSTEM

Abstract

The invention describes an LED lighting system (1) comprising a wireless communication arrangement (11, 12) for wireless transfer of signals (D.sub.10.sub._.sub.11, D.sub.11.sub._.sub.12, D.sub.4.sub._.sub.12, D.sub.5.sub._.sub.12) between devices (10, 11, 12, 4, 5) of the LED lighting system (1); at least one LED lamp (10) connectable to a mains power supply (2), which LED lamp (10) comprises a driver arrangement (100) with a control unit (102) for controlling the LED lamp (10) according to a received signal (D.sub.10.sub._.sub.11); a phase-cut detector (103A, 103B, 103C) realized to detect a phase-cut input (V.sub.cut) to the LED lamp (10); and a protection circuit (106) realized to prevent operation of the LED lamp (10) with the phase-cut input (V.sub.cut) if the phase-cut angle of the phase-cut input (V.sub.cut) exceeds a critical threshold, wherein said protection circuit (106) is adapted to prevent an exposure of the LED lamp to the phase-cut input. The invention further describes an LED lamp (10) comprising a driver arrangement (100); and a method of controlling an LED lighting system (1).

Claims

1. An LED lamp comprising a driver arrangement, which driver arrangement comprises: a control unit for controlling the LED lamp according to a received signal (D.sub.10.sub._.sub.11) received from a wireless communication arrangement of an LED lighting system; a phase-cut detector realized to detect a phase-cut input (V.sub.cut) to a driver of the driver arrangement; and a protection circuit realized to prevent operation of the LED lamp with the phase-cut input (V.sub.cut) as long as a phase-cut angle of the phase-cut input (V.sub.cut) exceeds a critical threshold, by preventing an exposure of the LED lamp to the phase-cut input.

2. An LED lamp according to claim 1, wherein the phase-cut detector is realized to detect a phase-cut angle (φ) of a phase-cut dimmer.

3. An LED lamp according to claim 1, wherein the phase-cut detector comprises an undervoltage detection circuit.

4. An LED lamp according to claim 1, wherein the phase-cut detector comprises an overcurrent detection circuit.

5. An LED lamp according to claim 2, wherein the phase-cut detector comprises a driver current monitoring circuit.

6. An LED lamp according to claim 1, wherein the protection circuit is realized to place the LED lamp in a standby mode of operation, and/or the protection circuit) is realized to issue a phase-cut angle correction signal (D.sub.5.sub._.sub.12) over a wireless communication arrangement to a remote-controlled dimmer device.

7. An LED lighting system comprising a wireless communication arrangement for wireless transfer of signals (D.sub.10.sub._.sub.11, D.sub.11.sub._.sub.12, D.sub.4.sub._.sub.12, D.sub.5.sub._.sub.12) between devices of the LED lighting system; and at least one LED lamp connectable to a mains power supply, which LED lamp is according to claim 1.

8. An LED lighting system according to claim 7, comprising a remote-controlled dimmer device, and wherein the protection circuit is realized to issue a phase-cut angle correction signal (D.sub.5.sub._.sub.12) over the wireless communication arrangement to the remote-controlled dimmer device.

9. An LED lighting system according to claim 7, wherein devices of the LED lighting system are realized to communicate according to a Zigbee specification.

10. A method of controlling an LED lighting system, which method comprises the steps of: providing a wireless communication arrangement for wireless transfer of signals (D.sub.10.sub._.sub.11, D.sub.11.sub._.sub.12, D.sub.4.sub._.sub.12, D.sub.5.sub._.sub.12) between devices of the LED lighting system; providing at least one LED lamp connectable to a mains power supply, which LED lamp comprises a driver arrangement with a control unit for controlling the LED lamp according to a received signal (D.sub.10.sub._.sub.11); detecting a phase-cut input (V.sub.cut) to the LED lamp; and preventing operation of the LED lamp with the phase-cut input (V.sub.cut) by preventing an exposure of the LED lamp to the phase-cut input, as long as a phase-cut angle of the phase-cut input (V.sub.cut) exceeds a critical threshold.

11. A method according to claim 10, wherein the step of preventing operation of the LED lamp with the phase-cut input (V.sub.cut) comprises a step of issuing a message (D.sub.10.sub._.sub.11, D.sub.11.sub._.sub.12, D.sub.4.sub._.sub.12) over the wireless communication arrangement for presentation by a software application running on a communications device of a user of the LED lighting system.

12. A method according to claim 11, wherein the message (D.sub.4.sub._.sub.12) comprises a set of instructions to assist the user in correcting a configuration of the LED lighting system.

13. A method according to claim 10, comprising the step of driving the LED lamp to generate a visual warning to a user of the LED lighting system.

14. A method according to claim 10, comprising the step of issuing a phase-cut angle correction signal (D.sub.5.sub._.sub.12) over the wireless communication arrangement to a remote-controlled dimmer device of the LED lighting system to adjust the phase-cut angle of the remote-controlled dimmer device to a minimum value.

15. A method according to claim 10, comprising the steps of: detecting a permissible input (V.sub.OK) to the LED lamp; and resuming operation of the LED lamp with the permissible input (V.sub.OK).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 shows a first embodiment of an LED lighting system according to the invention;

[0035] FIG. 2 shows voltage and current waveforms associated with a leading-edge phase-cut dimmer;

[0036] FIG. 3 shows a first embodiment of an LED lamp according to the invention;

[0037] FIG. 4 shows a second embodiment of an LED lamp according to the invention;

[0038] FIG. 5 shows a third embodiment of an LED lamp according to the invention;

[0039] FIG. 6 shows a second embodiment of an LED lighting system according to the invention.

[0040] In the drawings, like numbers refer to like objects throughout. Objects in the diagrams are not necessarily drawn to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] FIG. 1 shows a first embodiment of an LED lighting system 1 according to the invention. In this exemplary embodiment, the LED lighting system 1 comprises a protocol bridge 11 such as a Zigbee® bridge, and a router 12 which can communicate with the bridge over a wireless LAN, for example using an Ethernet protocol. The lighting system 1 comprises at least one LED lamp 10. To keep the drawing simple, only one LED lamp 10 is shown. The LED lamp 10 comprises a driver arrangement 100 with driver and control circuitry. The driver arrangement 100 has a communications interface to allow it to exchange data D.sub.10 11 with the bridge 11. In this way, the bridge 11 can send commands to the lamp 10, and the lamp 10 can send a report or feedback to the bridge 11. Furthermore, each lamp 10 of the lighting system 1 can act as a Zigbee® router in a mesh network and can forward commands (originating from the bridge 11) to other lamps of the lighting system 1. In this way, the physical range of the network can be extended. The bridge 11 and any LED lamps 10 can exchange data D.sub.10.sub._.sub.11 using a suitable protocol such as Zigbee® Light Link.

[0042] As explained above, the user of LED lamp 10 can install the lamp 10 in a lighting fixture that is connected to a mains power supply 2. A phase-cut dimmer 3 such as a wall-mounted dimmer 3 may be already present in the user's lighting setup. If the dimmer 3 is set to perform phase-cut on the mains voltage, the power supply to the lamp 10 will be characterized by a sudden voltage change on the leading edge or on the falling edge, depending on the type of phase-cut dimmer 3.

[0043] An example of an unacceptable or critical phase-cut input V.sub.cut is shown in FIG. 2. Here, a leading-edge dimmer set at a phase-cut angle φ of about 60° has cut a portion of the mains voltage (indicated by the dotted line) at the beginning of each half-cycle, resulting in the phase-cut input V.sub.cut. The result is a sudden voltage change, which in turn results in a spike in the current I.sub.spike through the output capacitor of the lamp's driver. The current spike at large phase-cut angles is problematic for the type of filter circuit that is generally used in a low power-factor LED driver design. In such a driver, a pi-filter is used to suppress electromagnetic interference (EMI), with a relatively large capacitor across the outputs of the filter. Such a phase-cut input V.sub.cut and the resulting current spike will eventually damage the LED lamp 10. Furthermore, the phase-cut results in a reduction in average voltage, which in turn increases the ripple current of the LED lamp, which in turn leads to a significant increase in temperature. To avoid damage resulting from current spikes and high temperatures, the LED lamp 10 according to the invention is provided with a phase-cut detector that can detect a phase-cut input to the LED lamp 10. If the phase-cut detector detects such a phase-cut input, the lighting system 1 applies a protection circuit to prevent operation of the LED lamp 10 with the phase-cut input. The phase-cut detector and protection circuit are explained below. FIG. 2 also indicates an acceptable or uncritical phase-cut input V.sub.OK (indicated by the broken line), for which the legacy phase-cut dimmer is set at a relatively small phase-cut angle φ.sub.OK of about 20°, corresponding to a low dimmer setting, i.e. maximum or near-maximum light output.

[0044] FIG. 3 shows a first embodiment of an LED lamp 10 according to the invention. This simplified diagram shows a driver arrangement 100 and an LED light source 110. The driver arrangement 100 comprises a driver 101, which is shown in a very simplified manner. Its function as a rectifier is indicated, and its output capacitor C is also indicated. A pi-filter for suppressing EMI is not shown, but it may be understood that the driver 101 comprises such a filter and that the output capacitor C is an element of the pi-filter. The LED light source 110 can comprise any number of LEDs in any suitable arrangement (for example white and coloured LEDs which can be mixed to provide a wide range of colours), indicated collectively by the LED symbol in the diagram. A microprocessor control unit 102 (MCU) is used to control the driver 101 to provide voltage and current according to the desired light output (the diagram indicates driver 101 and light source 110 in a very simplified manner; in an actual embodiment, different coloured LED strings are driven using appropriate circuitry to obtain the desired colour mix). As described above, the MCU 102 receives commands D.sub.10.sub._.sub.11 from a protocol bridge. The MCU 102 converts these commands D.sub.11.sub._.sub.11 into suitable control signals 104 for the lamp's driver(s) 101. In this exemplary embodiment, a phase-cut detector 103A is realised to detect an undervoltage V.sub.cut at the inputs to the driver 101. An undervoltage is detected when a phase-cut dimmer between the mains power and the LED lamp 10 has been set to reduce the average voltage. The phase-cut detector 103A generates a signal 105A that informs the MCU 102 when an undervoltage is detected, i.e. that the phase-cut angle is unacceptably large. To deal with this situation, the LED lamp 10 comprises a protection circuit 106. In this exemplary embodiment, the protection circuit 106 is realised as part of the MCU 102 but could of course be realized separately. The protection circuit 106 can be realized in hardware and/or software to react to the undervoltage at the driver inputs. For example, the protection circuit 106 can output a driver control signal 104 which instructs the driver 101 to place the LEDs 110 in standby, thus protecting the lamp circuitry from spike damage. The user may notice that the LED lamp 10 has been turned off. In a further development, the protection circuit 106 can output driver control signals 104 that instruct the driver 101 to cause the LEDs 110 to flash in a controlled manner, for example to flash once every second while at the same time reducing the light output, and then to place the lamp 10 a standby mode. This visual signal can inform the user that the lamp 10 is being “shut down” in a controlled manner, and may prompt him to check the dimmer setting. In a further development, the protection circuit 106 can issue a feedback message D.sub.10.sub._.sub.11 to the bridge, which in turn can send a message D.sub.11.sub._.sub.12 (as indicated in FIG. 1) to the WLAN router. If the user of the lighting system has a smartphone or other device running a suitable app, this can display a message forwarded by the router. For example, the feedback might result in an alert on the smartphone display, informing the user that the LED lamp 10 is connected to a dimmer set to perform phase-cut, and that corrective measures must be taken.

[0045] Of course, any of these responses can be combined in any appropriate manner. For example, to cover situations in which the user is not in the same room as the LED lamp 10 when this is switched on (e.g. in an burglar-deterrent lighting sequence) and therefore does not see the controlled flashing sequence when the lamp 10 is subsequently off again by the protection circuit 106; and/or does not look at his smartphone display when the alert is displayed and therefore does not see the warning message, the protection circuit 106 can instruct the driver to place the lamp 10 in standby mode if the phase-cut input is still present after a certain length of time. In this way, the lamp 10 is reliably protected from the adverse effects of a phase-cut input voltage and its high performance and long lifetime are safeguarded.

[0046] FIG. 4 shows a second simplified embodiment of an LED lamp 10 according to the invention, showing an alternative realization of a phase-cut detector 103B. In this case, the phase-cut detector 103B is realized as an overcurrent detector 103B which can detect a spike on the current through the output capacitor C. The presence of such a spike is notified to the MCU 102 in the form of a signal 105B, and the MCU 102 can react in any of the ways already described in Fig. above 3.

[0047] FIG. 5 shows a third simplified embodiment of an LED lamp 10 according to the invention, showing a further realization of a phase-cut detector 103C. In this case, the phase-cut detector 103C is realized as a driver output current monitor 103C which monitors the output current 107 of the driver 101 and compares this to an expected value. The driver output current is in the form of a modulated square wave at the switching frequency of the lamp's driver 101. To monitor the average driver output current, therefore, the phase-cut detector 103C comprises a first filter module 1031 for filtering and amplifying the driver output current. A further filter module 1032 serves to filter a pulse-width modulated (PWM) dimming signal originating from the MCU 102, and to bring this to a level corresponding to a maximum acceptable legacy dimmer setting, for example a level corresponding to 70% light output. The filter module outputs are compared in a comparator 1033, whose output 105C indicates to the MCU 102 when a phase-cut dimmer with an unacceptably large phase-cut angle is in active use with this lamp 10. The MCU 102 can respond as described in the preceding two embodiments, for example, the protection circuit 106 can output a driver control signal 104 which instructs the driver 101 to place the LEDs 110 in standby, thus protecting the lamp circuitry from spike damage.

[0048] FIG. 6 shows a second embodiment of an LED lighting system 1 according to the invention. This diagram shows further devices 4, 5 that can be included as part of the lighting system 1 of FIG. 1. Here, a smartphone 4 is included in the lighting system 1 by means of an app that runs on the smartphone 4, and which can exchange data D.sub.4.sub._.sub.12 with the WLAN router 12. A wireless dimmer 5 is also shown. This can be a radio-frequency (RF) controllable legacy “smart dimmer” 5 used to control dimming levels of a conventional light source such as a halogen lamp. Usually, such a dimmer is controlled by a hand-held remote control device. In the lighting system 1 according to the invention, the router 12 can also issue control signals D.sub.5.sub._.sub.12 to the dimmer 5.

[0049] The diagram shows an embodiment in which an LED lamp 10 according to the invention is used to retrofit an existing conventional lighting fixture. If the phase-cut detector of the lamp 10 detects a phase-cut voltage at the driver input and/or a spike on the output capacitor current as described above, the control unit 102 of the lamp 10 can react in any of the ways described above. In addition, the bridge 11 or WLAN router 12 can control the dimmer 5 to reduce the phase-cut angle to a minimum, i.e. to reduce the phase-cut to a minimum. This step can be carried out automatically upon detection of a phase-cut input, or after a certain length of time has elapsed without the user responding to a warning alert or to a flashing of the LED lamp 10.

[0050] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0051] For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements. The mention of a “unit” does not preclude the use of more than one unit.