LED driver, lighting device and LED based lighting application

Abstract

An LED driver for powering an LED fixture includes a power converter for converting an input power such as a rectified mains supply to an output power for powering the LED fixture; a control unit arranged to control an output characteristic of the power converter; optionally, a network terminal connected to the control unit for connecting the control unit to a network, the control unit being arranged to receive a control signal from the network via the network terminal for controlling the output characteristic; an application terminal connected to the control unit for connecting the control unit to a lighting device; the control unit being arranged to: provide a polling signal to the lighting device; receive, in response to the polling signal, a control signal for controlling the output characteristic.

Claims

1. An LED based lighting application comprising: an LED driver for powering an LED fixture, the LED driver comprising: a power converter for converting an input power to an output power for powering the LED fixture; a control unit arranged to control an output characteristic of the LED driver; and an application terminal connected to the control unit for connecting the control unit to a lighting device; wherein the lighting device comprises: an LED fixture and/or a sensor an i/o terminal connectable to the application terminal of the LED driver; and a control unit connected to the i/o terminal for providing a control signal to the application terminal of the LED driver; wherein the control unit of the LED driver is further arranged to convert the control signal to a command, to provide the command to a protocol stack of the control unit and to control the output characteristic based on the command.

2. The LED based lighting application according to claim 1, wherein the protocol stack is a DALI stack.

3. The LED based lighting application according to claim 1, wherein the control unit of the LED driver is further arranged to receive the control signal via the application terminal and control an output characteristic of the LED driver, based on the control signal.

4. The LED based lighting application according to claim 1, the stack further being accessible via a communication terminal of the LED driver.

5. The LED based lighting application according to claim 4, wherein the control unit of the LED driver is configured to provide the command to a communication network via the communication terminal.

6. The LED based lighting application according to claim 4, further comprising a second LED driver for powering a second LED fixture, the second LED driver comprising: a power converter for converting an input power to an output power for powering the second LED fixture; a control unit arranged to control an output characteristic of the second LED driver; and a communication terminal connected to the control unit for connecting the control unit to a communication network; wherein the control unit of the second LED driver is configured to receive the network command via the communication network and control the output characteristic of the second LED driver based on the command.

7. The LED based lighting application according to claim 1, wherein the output characteristic is controlled by adjusting a configuration parameter stored in the control unit of the LED driver, based on the control signal.

8. The LED based lighting application according to claim 1, wherein the control unit of the lighting device is arranged to receive configuration data or operating data of the LED fixture or sensor and generate the control signal based on the configuration data or operating data.

9. The LED based lighting application according to claim 1, further comprising: a communication terminal connected to the control unit of the LED driver for connecting the control unit of the LED driver to a communication network, the control unit of the LED driver being arranged to receive a further control signal from the communication network via the communication terminal for controlling the output characteristic.

10. The LED based lighting application according to claim 1, wherein a two-wire connection is provided connecting the application terminal and the i/o terminal.

11. The LED based lighting application according to claim 1, wherein the application terminal is further arranged to output the output power for powering the LED fixture and/or sensor.

12. The LED based lighting application according to claim 1, wherein the control unit of the lighting device is adapted to be powered via the i/o terminal.

13. The LED based lighting application according to claim 1, further comprising an auto-reverse bridge connected at the application terminal of the LED driver.

14. The LED based lighting application according to claim 1, further comprising an interface for coupling the sensor or LED fixture to the control unit of the lighting device.

15. The LED based lighting application according to claim 14, wherein the interface is a USB interface, a DMX interface or RF interface.

16. The LED based lighting application according to claim 1, wherein the output characteristic is an output characteristic of the power converter of the LED driver.

17. A method of controlling an LED based lighting application comprising: providing an LED driver for powering an LED fixture, the LED driver comprising: a power converter for converting an input power to an output power for powering the LED fixture; a control unit arranged to control an output characteristic of the LED driver; and an application terminal connected to the control unit for connecting the control unit to a lighting device; wherein the lighting device comprises: an LED fixture and/or a sensor an i/o terminal connectable to the application terminal of the LED driver; and a control unit connected to the i/o terminal for providing a control signal to the application terminal of the LED driver; wherein the control unit of the LED driver is further arranged to provide the steps of: converting the control signal to a command; providing the command to a protocol stack of the control unit; and controlling the output characteristic based on the command.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically depicts a general set-up of a lighting application according to the invention including an LED driver according to the invention.

(2) FIG. 2 schematically depicts an electronic circuit enabling the communication between an LED driver according to the invention and an LED fixture.

(3) FIG. 3 schematically depicts a voltage waveform of a polling signal and response signal as can be applied in the present invention.

(4) FIG. 4 schematically depicts various timing aspects of signals provided by either an LED driver or lighting device according to the invention.

(5) FIG. 5 schematically depicts a functional layout of an embodiment of a control unit as can be applied in an LED driver according to the invention.

(6) FIG. 6 schematically depicts an embodiment of an LED based lighting application according to the present invention.

(7) FIG. 7 schematically depicts an auto-reverse bridge as can be applied in an LED driver or lighting device or lighting application according to the invention.

(8) FIG. 8 schematically depicts the use of an auto-reverse bridge in a lighting application according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(9) FIG. 1 schematically depicts a lighting application according to an embodiment of the present invention operating in a network environment. The lighting application as shown comprises a plurality of ballasts/LED drivers or power supplies 100 arranged to power (one or more) LED fixtures 110 (also referred to as LED engines).

(10) In an embodiment, such an LED fixture can merely comprise one or more LEDs mounted in a fixture or socket or the like. More advanced LED fixtures may further include sensors such as ambient or occupancy sensors or may be adapted for connecting to such sensors, as schematically indicated by lines 160 and 170. Such connections may by either wired or wireless connections.

(11) The plurality of ballasts 100 is, as can be seen in FIG. 1, connected to a network 130, e.g. using DMX, 0-10V or DALI or alike as a communication protocol. As such, the ballasts each have a network terminal connected to a control unit of the ballast (not shown) for connecting to the network 130. Via the network 130, the ballasts 100 can further be connected to other components of the network which can e.g. include user interfaces such as sliders or knobs. Further components can also include a control unit (e.g. a DALI master control unit) co-ordinating communication between user interfaces and the power supplies. As can be seen in FIG. 1, the power supplies of the lighting applications are further provided with a further communication interface, indicated by the single wire bus 140 that enables communication between the LED fixture and the LED driver. In order to enable this, the power supplies 100 according to the present invention are provided with a further terminal (referred to as the application terminal, not shown)) allowing connecting the LED driver to the LED fixture and exchanging information between the LED fixture and the LED driver. Such communication interface (which is explained in more detail below) can e.g. be a single wire communication bus, preferably using the uni/o communication protocol. As shown in FIG. 1, the application terminal can be used to connect the LED driver 100 to the LED fixture 110, via the single wire bus 140. In accordance with the present invention, the application terminal may also be used for connecting other types of lighting devices (i.e. apart from LED fixtures) to the LED driver. Such lighting devices 120 can e.g. include sensors such as ambient or occupancy sensor which may thus be directly connected to the LED driver 100 using the application terminal (indicated by the connection 150).

(12) In such an arrangement, the LED driver can thus be controlled/adjusted based on a signal received from the lighting device 120 (e.g. an ambient sensor indicating an illumination at a particular location) directly received via the application terminal. As such, the lighting device 120 need not be connected to the network 130 for controlling the LED driver. As such, the use of an application terminal in an LED driver according to the present invention enables a local control or configuration of an LED driver by providing configuration data or operating data to the LED driver via a separate terminal, which can be used independent of a network.

(13) In an embodiment, further communication with a network may be made possible via a network terminal connected to the control unit. Using such network terminal, an LED driver according to the present invention can thus transmit and/or receive further control signals to/from further LED drivers connected via such a network terminal.

(14) Such arrangement may simplify the required architecture/design of such a lighting device; the lighting device need not comprise a DALI stack in order to communicate to the network. By using the communication bus connecting the i/o terminal of the lighting device to the application terminal, control signals from the lighting device can be distributed over the network. In case multiple lighting devices are connected to the application terminal, they may thus share the networking functionality provided by the LED driver.

(15) In an embodiment, the signals received from the lighting device are used to adjust a configuration parameter of the LED driver, e.g. stored in the control unit of the LED driver. The signals received may also be converted by the control unit of the LED driver to commands which can be provided to a so-called protocol stack, e.g. a DALI stack of the LED driver. Such a protocol stack can be considered part of the control unit of the LED driver.

(16) In FIG. 2, a more detailed description of the circuitry providing the communication via the application terminal of the LED driver is provided.

(17) In FIG. 2, reference numbers 220 represent the communication line or bus between an LED driver (on the left) and a control unit 210 of an LED fixture (in general a lighting device). The LED driver comprises a control unit uC connected to an application terminal 205 which can be used for communication between the LED driver and the control unit 210 of the LED fixture. In accordance with an embodiment of the invention, the LED driver can control the communication bus through its application terminal 205, e.g. connected to a low-impedance resistor 270. The control unit uC of the LED driver can. e.g. set the application terminal 205 to output at a low voltage or at a high voltage or it can configure the application terminal to be an input having a comparatively high impedance, thus enabling operating in three-state logic. When operating in the latter state, the control unit 210 can be allowed to control the voltage on the communication bus 220, which voltage can be read by the control unit uC of the LED driver via the application terminal when operating as an input.

(18) In case the application terminal is in such input mode, the bus voltage is pulled high by resistor 260 when no control unit 210 is actively controlling the bus. To avoid interference, a capacitor 280 in combination with resistor 260 can be applied to filter small spikes or disturbances to a certain degree.

(19) In an embodiment, the control unit 210 of the lighting device is powered from the bus 220 via a regulator 230. In such arrangement, the regulator 230 and its surrounding circuitry must be dimensioned to buffer some power in order to enable the control unit of the lighting device to remain operational when the bus voltage is low for several bit periods or when the bus has a low average voltage due to intermingled high and low bits. For such buffering, a capacitance such as capacitance 295 in FIG. 2 can be used.

(20) To receive data from the bus, the lower bus line of 220 is coupled to the control unit's ground while the upper bus line is coupled to an i/o terminal 215 of the lighting device using the diode/resistor combination 240. The control unit of the lighting device can short-circuit the bus 220 using its Tx output port. This port controls a current source 250 thus enabling a short-circuiting of the bus. (as an alternative to the current source, a switch (e.g. a FET) may be applied for short-circuiting the bus by switching a low-impedance resistor across it. Such short circuiting can thus take the form of an analogue voltage dip and can be considered by the control unit of the LED driver as a response signal indicating that the lighting device has an event to report. Subsequently, after receiving a query message from the master with its address in it, a specific slave can thus control its Tx port to reply using a message according to the uni/o protocol by a similar modulation of the bus voltage. Due to the capacitance of the communication bus, a recovery of the voltage after a short-circuiting may be comparatively slow. In order to speed up this recovery up to a voltage level that can be recognized as a 1, by briefly raising the Rx voltage. It can be noted that, by using a current source 250 (instead of a resistor in series with a switch), the current can be set such that smaller voltage dips can be caused; i.e. voltage dips that remain above 0V, e.g. a voltage dip of 0.5 V on a 5V communication bus. Such (minor) voltage dips may be observed by an analogue terminal at the LED driver side and thus recognised as bits. Using only minor voltage dips may cause less disturbance to the illumination of the LED fixture when the communication powering are provided via the same wires.

(21) The communication protocol as applied between the LED driver and the lighting device should be such that the interaction is organized such that LED driver and a lighting device connected to the LED driver write to the communication bus in an alternating fashion, and should further ensure that no more than 1 lighting device is writing to the communication bus at a certain time. FIG. 3 shows in more detail a communication protocol as can be applied when an LED driver is used to power one or more lighting devices such as LED fixtures or sensors.

(22) In order to ensure that the communication of the LED driver and the lighting device or devices is arranged in an alternating fashion, the LED driver, operating as master, can provide a polling signal to the lighting devices (operating as slaves) whereupon the lighting devices can send a response signal in order to inform the LED driver whether or not the lighting devices have an event to report; such event e.g. corresponding to the provision of a control signal based on configuration data or operating data.

(23) In FIG. 3, waveform 300 corresponds to the voltage on the communication bus in case where a master (i.e. the LED driver) polls (i.e. sends a polling signal) but no lighting device answers. Waveform 310 represents the case where the LED driver polls and at least 1 lighting device answers.

(24) In the latter case, the protocol is as follows: Assuming that any event handling (referring to any of the lighting devices having provided the LED driver with a control signal, e.g. comprising configuration or operating data) has been done, in response to a polling and subsequent reply (i.e. an earlier interaction), both the master and slave may enter a so-called polling mode. This can be automatic, e.g. at a predetermined rate; at specific time instances apart or through the master sending a specific broadcast message.

(25) When operating in the polling mode, the master may as an example, pull the communication bus (e.g. the upper bus line in FIG. 2) voltage low at time 320 (as can be seen in waveform 300), and sets its application terminal to high-impedance at time 330. Due to the use of one or more pull-up resistors at the application terminal (e.g. resistor 260 as shown in FIG. 2), the bus voltage will gradually return to the high (voltage) state, as can be seen in waveforms 300 and 310. Such pulling down of the communication bus voltage can be considered an example of providing a polling signal to the communication bus connecting the LED driver and the lighting devices. In an embodiment, the master (i.e. the LED driver) may then allow the time between instances 330 and 360 for slaves to answer, i.e. send a response signal in response to the polling signal. Such a response signal can e.g. be provided to the communication bus by any of the lighting devices connected, in case such lighting device wants to have an event handled. Such event e.g. corresponding to the lighting device have configuration or operating data to provide. In an embodiment, such a reply by the lighting device can be made by pulling the bus voltage low (at time 340) and release the bus again at time 350. Such pulling down and subsequent release of the communication bus voltage can be considered an example of providing a response signal to the communication bus in accordance with the present invention. At time instance 360 as indicated in FIG. 3, the master can leave polling mode and subsequently query each slave until the slave is found that reports the event, using the standard protocol. Such query can thus comprise a digital and sequential polling of all slaves one by one thus inquiring each slave about the events to report. In such query message, the address of a slave is comprised according to the uni/o protocol. As such, only one slave can respond to the query. Once such response is received, a further query message can be sent to obtain a control signal of a next slave.

(26) The advantage of the polling protocol as described, i.e. the sequence of providing a polling signal (by the LED driver) and a response signal (by any of the lighting devices) is that the amount of power needed to perform the polling is minimal. Further, when the polling signal is not followed by a response signal, the control unit of the LED driver need not start the query because there is no event to report. This has been found to be particularly useful since minimizing power is needed to achieve the very strict standby or low power requirements of the lighting industry.

(27) This can be illustrated by the following requirements:

(28) The power budget when the illumination set-point is 0 (i.e. no light output to be provided by the lighting application) or otherwise very low has been set very low in various regulations:

(29) smaller than 0.5 W standby for 100 W units

(30) smaller than 0.3 W standby for 50 W units

(31) In FIG. 4, more details are provided on a typical communication of data between the LED driver's control unit and a lighting device's control unit according to the present invention.

(32) FIG. 4 a) schematically shows the part of the standard UNI/O protocol that limits the bus speed when using the microprocessor at the peak of its interrupt abilities.

(33) In FIG. 4 a), waveform 410 represents a message as provided by a master (i.e. a LED driver) on the communication bus connecting the LED driver with one or more lighting devices (slaves) while waveform 420 represents a possible response signal (e.g. a control signal based on configuration and/or operating data of the lighting device) from an addressed slave. To generate the array of bits represented by waveform 410, i.e. the master bits, a typical master processor will program a regular interrupt to occur. Such an array of master bits can represent a signal provided to the one or more lighting devices, wherein the signal comprises an identifier of the lighting device. Typically, the signal is provided according to the uni/o protocol. The times at which these interrupts occur are represented by the array of interrupts 400 in FIG. 4 a). Such an array of interrupts thus representing a clock signal which, in this case is generated by the master processor, e.g. the control unit of the LED driver according to the invention. The interrupts are programmed to be fired as fast as the processor is able to. As the same interrupt is used to receive the bits from the slaves, an interrupt should be fired half-way a received bit in order to assess the bit. Assuming that the slave bits are defined to come in on the same clock as the master bits are sent, time period 440 determines that 2 neighboring interrupts are needed to switch over from sending master bits to receiving slave bits. Time period 440 is then equal to the fastest interrupt rate of the processor whereas time period 430 is twice this time period 440. This means that half of the interrupts are not used.

(34) In FIG. 4 b), it is illustrated how the communication over the bus can be speeded up by a factor of two. This is done by introducing a quarter bit delay time 490 in the response signal from the slave. In FIG. 4 b) 450 schematically represents the array of interrupts at maximum interrupt rate, waveform 460 represents a message as provided by the master while 470 represents a response by the slave. To speed up the bus by a factor of 2, a quarter bit delay time 490 is introduced in the slave's response. As can be seen, the response by the slave is delayed by bit relative to the clock signal of the master processor. As a result, as can be seen in FIG. 4 b), every interrupt can now be used to handle bits. This means that the communication bus can be driven at double the speed given the same fastest interrupt rate for a certain processor.

(35) Referring to FIGS. 3 and 4, the communication between the control unit of the LED driver and the control unit of the lighting device can thus comprise the following sequence of signals: a polling signal (e.g. as shown in FIG. 3) is provided on the communication bus between the LED driver and the one or more lighting devices connected; the polling signal being provided from the control unit of the LED driver (via the application terminal) to the control unit of a lighting device (via the i/o terminal of the lighting device); in response, a response signal (e.g. as shown in FIG. 3) can be provided by the lighting device in case the lighting device has an event to report (e.g. the provision of configuration data or operating data regarding the lighting device). In case more than one lighting device is connected, the lighting devices can be arranged to send the response signal on different instances relative to the instance of polling signal. By doing so, the control unit of the LED driver can distinguish the response signals. Alternatively, the response signals (e.g. an analogue voltage dip exerted on the communication bus by the lighting device) may overlap. In the latter case, the LED driver may subsequently send an query message (typically a signal according to the uni/o standard, the signal comprising an identifier of one of the lighting devices connected (see above) When the query message is received, the lighting device can send the signal related to the event to be reported (i.e. the first control signal as referred above), typically using the uni/o protocol or standard.

(36) As explained in FIG. 4, preferably, the signal related to the event to be reported is delayed relative to the interrupt rate that is used for the transmission of the query message or signal.

(37) As illustrated, by introducing a delay of e.g. bit between data signals (e.g. comprising an identifier or configuration or operating data) sent by the LED driver and the lighting device, the transmission over the communication bus connecting the application terminal and the i/o terminal can be increased by a factor of two.

(38) FIG. 5 schematically depicts a possible architecture of the control unit as can be applied in a LED driver or lighting application according to the invention.

(39) The control unit as schematically shown in FIG. 5 comprises an application interface 725 which may e.g. correspond to the application terminal as schematically shown in FIG. 2, whereby the application interface can be used for providing polling signals and receiving control signals (indicated by the arrow 730) to and from a lighting device such as an LED fixture or a sensor. In an embodiment, the application interface 725 may further comprise a bridge for converting the signals provided to and from the application terminal. In the arrangement as shown, the application interface is assumed to provide a conversion to SPI-compatible signals. In such arrangement, the control unit can further comprise a bridge 715 for interfacing with a protocol stack such as a DALI stack, which can be incorporated in the control unit such that control signals obtained via the application terminal (part of the application interface 725) can be provided to the DALI stack. Such a DALI stack 705 can be connected to the network terminal (not shown) of the control unit which can receive signals or commands 700 from e.g. a DALI network connected to the LED driver. In such arrangement, the network commands 700 may be provided by the DALI stack to what is called the master application-logic (MAL) 760. This part of the control unit (which may be integrated in a single processor also comprising the DALI stack, the application interface and the bridges 715 and 735 (see further on), or may be a separate controller) refers to the logic that controls the power converter of the LED driver. As such the commands or control signals received via the DALI stack (indicated by 745) may e.g. represent illumination set-points derived from the commands that are submitted as input to the DALI stack (either inputs from the network terminal or from the application terminal). In the arrangement of the control unit as shown, signals 730 as received via the application terminal may also be provided directly (indicated by arrow 750) to the master application-logic 760 via a bridge 735 receiving signals 740 from the application interface 725 as input. The bridge 735 thus provides an interface between the SPI compatible output of the application interface 725 and the master application logic 760. In an embodiment, the bridge 735 may also be arranged to adjust a parameter setting (e.g. in a memory unit 755 of the control unit) based on the control signals received (740). In such arrangement, the memory unit 755, which thus can take the form of a parameter database, can further be accessed by the master application-logic. As such, an adjustment or modification of a parameter stored in unit 755 may result in an adjustment or modification of an output characteristic of the LED driver controlled by the control unit.

(40) In an embodiment, the commands or control signals as provided to the DALI stack may not only be provided to the master application-logic 760 but may equally be provided to other applications that are connected to the network interface of the control unit.

(41) As an example, an occupancy sensor or ambient sensor connected to the application terminal may thus provide, via the bridge 715 a control signal to the DALI stack. Subsequently, this control signal can be provided (e.g. as a DALI command 700) to other applications such as other LED drivers that are also connected to the network. Such drivers may apply this signal in controlling an output characteristic of an LED fixture that is powered, f.e. by dimming the brightness.

(42) Similar to the control unit of the LED driver, the control unit of the lighting device can comprise one or more bridges or interfaces facilitating the conversion of an input signal (such as a sensor signal) to the appropriate format for transmission to the LED driver. In this respect, different types of interfaces are feasible. Examples are a USB interface, a DMX interface, an RF interface or the like. Using such a bridge or interface in the control unit of the lighting device facilitates coupling various types of devices such as sensors e.g. having different interfaces to the LED driver without having to certify the LED driver for each type of interface.

(43) In accordance with the present invention, the lighting device, or the control unit of the lighting device may process the input signal prior to being transmitted. As an example, the control unit can keep track of the accumulated operating hours of a lighting device and provide this information for maintenance purposes. The control unit can process a feedback signal from an ambient sensor to a control signal for the LED driver such that a desired brightness is obtained, taking ambient light conditions into account.

(44) In an embodiment of the present invention, the application terminal of the LED driver is equally applied for supplying the required power to the LED fixture. In such arrangement, the power required for powering the control unit of the LED fixture (i.e. corresponding to the lighting device in such arrangement) is preferable also derived from the power supply to power the LEDs of the LED fixture. In FIG. 6, such an arrangement is schematically depicted. FIG. 6 schematically shows an LED based lighting application comprising an LED driver 800 (referred to as driver) having an application terminal 805 that is used to power an array of LEDs 850 of an LED fixture comprising the array of LEDs and a control unit 810 (referred to as slave) comparable to the control unit 210 of FIG. 2. In the arrangement as shown, the LEDs are powered via the application terminal 805. Further, a slave supply 830 is provided for providing a supply voltage Vs to the control unit 810, the voltage being derived from the power supplied via the application terminal. As can be seen, only a two-wire connection needs to be present between the LED driver 800 and the LED fixture for both powering the LED fixture and arranging communication between the LED fixture and the LED driver.

(45) In such arrangement, communication between the LED driver and LED fixture can be arranged in various ways.

(46) As a first example, the LED driver can be (briefly) interrupted at a predetermined rate, thus generating a (brief) time frame that is used for communication. As an example, after every 3 ms, one can reserve 0.336 ms for communication. During said period of 0.336 ms, polling signals or control signals can be exchanged. Note that the use of a total period of 3.336 ms is particularly useful for synchronizing with video or TV systems.

(47) As a second example, a modulation of the duty cycle of the LED driver to the LEDs can be used for communication towards the lighting device. Modulation of the duty cycle of a LED of the LED fixture can be used to transmit (bit by bit) signals to the LED fixture.

(48) The arrangement as shown further comprises a level detector and limiter 860. Based on e.g. the voltage level detected (on the supply line 815), the control unit can determine whether to operate in a communication mode or LED powering mode, e.g. when the voltage is sufficiently below the total forward voltage of all connected LEDs, the communication mode is entered, otherwise LED powering mode is set.

(49) In an embodiment, the LED based lighting application according to the invention is provided with an auto-reverse bridge connected between the application terminal of the LED driver and the lighting device (See FIGS. 7-8). Such an auto-reverse bridge can e.g. be incorporated in either the LED driver or the lighting device, e.g. the LED fixture to be powered. Such an auto-reverse bridge facilitates the installation of the lighting application because, due to the bridge, the proper operation of the lighting application is ensured, regardless of the polarity of the connection between the LED driver and the lighting device.

(50) FIG. 7 schematically depicts an embodiment of such an auto-reverse bridge. The bridge as depicted comprises four FETs (540, 550, 560 and 570), two N-FETs (560 and 570) and two P-FETs (540, 550). The bridge is connected between a first terminal (510-500) and a second terminal (530-520). The first terminal (510-500) can e.g. be connected to the application terminal of a LED driver according to the invention, whereas the second terminal can e.g. be connected to the i/o terminal of a lighting device. As further can be seen, the gate terminals of FETs 550 and 560 are connected to 500 whereas the gate terminals of FETs 540 and 570 are connected to 510. In general, these connections between the gates of the FETs and the connections 500, 510 will comprise a passive component network (not shown).

(51) In such arrangement, the first terminal can e.g. be connected such that 510 is connected to the upper line of communication bus 220 of FIG. 2 whereas 500 is connected to the lower line. The connection may however also be reversed. As will be explained below, the auto-reverse bridge can ensure the proper operation in both situations.

(52) Assuming 510 is connected to the positive communication bus side and 500 is connected to the negative (or ground) bus side, the operation is as follows:

(53) In case the voltage at 510 is higher than the voltage at 500, the drain of P-MOSFET 550 will have a positive potential. The gate of 550 is pulled to the negative potential at connection 500 by the network (not shown) connecting the gate 550 and the connection 500. Once the gate voltage is lower than the drain voltage, FET 550 will conduct. When FET 550 starts to conduct, the body diode of FET 550 will be short-circuited and the source voltage will increase up to the level of the voltage 510 present on the drain. As such, the voltage at connection 530 will substantially correspond to the voltage on connection 510.

(54) As soon as the voltage at 510 is higher than the voltage at 500, the drain of FET 570 will have a negative voltage. The gate voltage of 570 is pulled to the positive bus voltage 510 via a passive component network. Once the gate voltage is higher than the drain voltage, the enhancement N-MOSFET 570 will conduct. As a result, the body diode of 570 is short-circuited and the source voltage of 570 will drop, substantially to the voltage 500 present on the drain. As such, the voltage at connection 520 will substantially correspond to the voltage on connection 500.

(55) When connections 500 and 510 are reversed, FETs 540 and 560 will essentially operate in the same way as FETs 550 and 570, resulting in the same desired connection between a LED driver and a lighting device.

(56) In FIG. 8, a bridge as depicted in FIG. 7 is arranged between a LED driver 900 and a lighting device 910 comparable to the LED driver and lighting device shown in FIG. 2.

(57) In an embodiment, the auto-reverse bridge is incorporated in a lighting device according to the invention. As such, no errors can be made when connecting the lighting device to the LED driver.

(58) As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the invention.

(59) The terms a or an, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language, not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention.

(60) 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.

(61) The term coupled, as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically.

(62) A single processor or other unit may fulfil the functions of several items recited in the claims.