Patent Description:
LED based illumination systems are currently widely used for both domestic and professional illumination.

Compared to conventional illumination systems such as incandescent or halogen lamps, LED based illumination systems may have a large variation in functionality which results in a large variation in power or powering requirements. Typically, LED based luminaires are powered using a power converter, also referred to as an LED driver, which converts an available power supply, e.g. a mains power supply, to a convenient power supply for the LED based luminaire or illumination system. Because of the large available variation in LED based luminaires and a corresponding large variation in power requirements, one cannot merely connect an arbitrary LED driver to an arbitrary LED based luminaire. More specifically, one needs to be sure that the power supply as generated by the particular LED driver, e.g. characterised by an output voltage and current, is suitable to drive the particular LED based luminaire. Phrased differently, one needs to ensure that the power supply as generated by the LED driver matches with the power requirements of the LED based luminaire.

In known arrangements, such a matching between an LED driver and a LED based luminaire has to be done manually, whereby the available output power of the LED driver is set so as to match with the requirements of the LED based luminaire. Alternatively, a setting or initialisation of the LED driver's output power may also be realised by the LED driver exchanging information with the LED based luminaire, e.g. via a communication terminal. Typically, the requirement to match an operation of a particular LED driver to a particular LED based luminaire may require either the LED driver or the luminaire to have multiple input or output terminals. <CIT> discloses a method relating to the configuration of LED driver for an LED fixture by identifying the fixture, sending a configuration request to a database via a communication network, and configuring the LED driver based on the received configuration data. <CIT> pertains to a control circuit for at least one LED or LED array, primarily in the context of driving LEDs mounted on circuit boards with constant current sources, and it allows LED modules to transmit operational parameters to a driver module through a module identification channel, facilitating compatibility and control adjustments between different LED modules and driver modules. <CIT> relates to the transmission of power and data simultaneously over the same line, using techniques like pulse width modulation for power regulation and frequency variation or impedance alteration for data transmission, enabling devices to be powered and communicate data effectively over a single line. <CIT> discloses a control device for a light source, particularly for powering one or more LEDs, with a power factor correction circuit, offering adjustable DC voltage based on readings from an electrical component on an LED module, allowing for precise adaptation to various LED currents and reducing issues related to hard switching and heat dissipation. <CIT> describes lighting systems for transit vehicles, specifically LED-based lighting fixtures with various features like power regulation, temperature control, and dimming capabilities, as well as a networked control system for these fixtures, aiming to address the limitations of traditional fluorescent lighting systems in such vehicles.

It would be desirable to further facilitate an automated matching between an LED driver and a LED based luminaire or LED based light.

The invention is defined by a method of initializing an LED driver in accordance with claim <NUM>, and by an LED driver in accordance with claim <NUM>.

To better address one or more of these concerns, in an aspect of the invention, there is provided a method of initializing an LED driver to power an LED light engine comprising one or more LEDs, the method comprising:.

According to a further aspect of the present invention, there is provided an LED driver for powering an LED light engine, the LED driver comprising:.

According to a non-claimed embodiment, there is provided an LED light engine comprising.

These and other aspects of the invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description and considered in connection with the accompanying drawings in which like reference symbols designate like parts.

<FIG> schematically shows a lighting system <NUM> according to the present invention, the lighting system <NUM> comprising an LED driver <NUM> according to the present invention and an LED light engine <NUM> according to the present invention. In the embodiment as shown, the LED driver <NUM> comprises an input terminal <NUM> for receiving a supply power Pin, and an output terminal <NUM> for outputting a required power Pout for powering the light engine <NUM>. Pin can e.g. be provided via a rectified mains supply power or a DC power source. The output power Pout can e.g. be a DC current or a pulsed DC current for powering the LED or LEDs <NUM> of the LED light engine <NUM>. The output power Pout as generated by the LED driver <NUM> can e.g. be provided to the light engine <NUM> via the input terminal <NUM> of the LED light engine <NUM>. In the embodiment as shown, the LED driver <NUM> comprises a power converter <NUM> that is configured to convert the supply power as received via the input terminal <NUM> to the required output power Pout for powering the light engine <NUM>. The power converter <NUM> can e.g. be a switched mode power converter such as a Buck, Boost or hysteretic converter. The power converter <NUM> can e.g. be configured to supply a suitable current to the light engine <NUM> for powering the LED or LEDs <NUM>. The supplied current may return to the power converter either via a ground terminal, in which case the LED or LEDs <NUM> are connected between the input terminal <NUM> and the ground terminal <NUM>, or via a dedicated return terminal (not shown). In the embodiment as shown, the power converter <NUM> can be controlled by a control unit or controller <NUM>, e.g. comprising a processor or microcontroller. In accordance with the present invention, the LED driver <NUM> further comprises a control terminal <NUM> which can be applied by the control unit or controller <NUM> for retrieving information of the light engine <NUM> and/or for communicating with the light engine <NUM>. In this respect, the control terminal <NUM> may aIso be referred to as a communication terminal. In the embodiment as shown, the LED light engine <NUM> further comprises a control terminal <NUM> which is configured to be connected to the control terminal <NUM> of the LED driver <NUM>. In accordance with an embodiment of the present invention, the LED driver may be configured to perform an initialization method when the control terminal <NUM> of the LED driver <NUM> is connected to the control terminal <NUM> of the LED light engine <NUM>.

Unlike incandescent conventional lighting applications, light engines comprising LEDs or LED groups may come with a large variety of power requirements. As such, depending on the type of light engine used, the LED driver powering the light engine needs to provide the required power in the appropriate manner for the particular light engine. In particular, the output voltage of the output terminal may e.g. depend on the number of LEDs of the light engine arranged in series. The current requirements may e.g. depend on the number of LEDs that are applied in parallel.

In general, an LED driver may be designed to supply a power within a certain range, e.g. specified as an available voltage range for the output voltage and an available current range for the output current, i.e. the current that can be supplied to the light engine.

In order to ensure that an LED driver provides a suitable power (e.g. both voltage and current matching the light engine requirement) for the light engine, an initialisation of the LED driver is typically performed.

One possible manner to initialize and LED driver is to manually control the possible output of the LED driver, e.g. setting a maximum output voltage and a maximum output current, thus ensuring that the light engine is not damages.

It has also been proposed to initialise a light engine by providing it with a resistor having a predetermined value, whereby, when an LED driver is connected to the light engine, the LED driver can readout the resistance value, and based on the determined value, initialize an operation of the LED driver, thereby ensuring providing the appropriate power to the light engine. Such a resistor may e.g. be referred to as an R-init resistor, as it enables a setting or initialisation of a desired or required output power for the LED driver.

Alternatively, a light engine can be provided with a tag or even with a processor or processing unit whereby information about the light engine can be exchanged via the tag or processor with the control unit of the LED driver. Within the meaning of the present invention, a tag refers to a device which can store data, e.g. in a memory of the tag. The tag is further configured such that the data as stored may be retrieved via a terminal of the tag, e.g. by means of digital communication.

The initialisation data or configuration data that may be derived from an R-init value or which may be retrieved from a tag may e.g. include values for a nominal current, a maximum current, maximum or nominal output voltage or maximum or nominal power. In addition, the initialisation data or configuration data may also provide details on how the particular light engine should be powered. In particular, the initialisation data or configuration data may include information on the modulation method that is to be applied to control the light engine. According to an aspect of the present invention, a method has been devised enabling an LED driver to initialize irrespective of whether the light engine has been provided with a resistor to set the power requirements or with a tag or processor. The method is schematically depicted in <FIG> schematically shows a method of initializing an LED driver according to an embodiment of the present invention, the method comprises:.

The method according to present invention may be described with reference to <FIG> and <FIG> as follows:
In a first step <NUM> of the initialization method according to the present invention, a control terminal <NUM> of the LED driver <NUM> is connected to a control terminal <NUM> of the LED light engine <NUM>.

In a second step <NUM>, the method comprises determining whether or not the control terminal <NUM> of the LED light engine <NUM> is a communication terminal or not. This can be realised by transmitting or outputting a communication signal from the control terminal <NUM> of the LED driver <NUM> to the control terminal <NUM> of the LED light engine <NUM>.

In a third step <NUM>, the method comprises establishing that the control terminal <NUM> of the LED light engine <NUM> is a communication terminal if a reply communication signal to the communication signal is received within a predetermined period. By doing so, the control terminal <NUM> of the LED driver can establish that the LED light engine <NUM> that is to be powered is equipped with a tag or processor which has the ability to communicate with the LED driver <NUM>. In case the control terminal <NUM> of the LED light engine is identified as a communication terminal, the method comprises:
a fourth step <NUM> of perform an initialisation of the LED driver <NUM> by exchanging configuration data between the LED driver <NUM> and the LED light engine <NUM>. In this step, the control unit <NUM> of the LED driver <NUM> may e.g. be configured to retrieve, via the control terminal <NUM>, information regarding the required power settings for powering the LED light engine with which it communicates. Such power settings may e.g. include a maximum output voltage, a maximum output current, a nominal current value, etc..

As will be appreciated by the skilled person, various lighting communication protocols may be applied to communicate between the LED driver <NUM> and the LED light engine <NUM>. Such protocols e.g. include <NUM>-10V, Dali, DMX, or any dedicated communication protocol agreed between the LED driver manufacturer and the LED light engin manufacturer.

In case the control terminal <NUM> of the LED light engine is identified as not being a communication terminal, the method comprises the step <NUM> of determining an impedance value observed at the control terminal <NUM> of the LED light engine and performing an initialisation of the LED driver based on the impedance value.

In the embodiment shown in <FIG>, the LED based light engine or LED light engine <NUM> comprises an impedance <NUM> that is connected to the control terminal <NUM>. When the LED driver <NUM> has established that the control terminal <NUM> is not a communication terminal, when no reply to the communication signal is received within the predetermined period, the control unit <NUM> can assess the impedance value, e.g. a resistance value, of the impedance <NUM>. Such an assessment can e.g. include supplying a current to the control terminal <NUM> of the LED light engine <NUM> and measuring the voltage at the communication terminal <NUM>. Alternatively, the control terminal <NUM> may provide a voltage to the control terminal <NUM> and determine the impedance <NUM> based on a current measurement of a current to the control terminal <NUM>. In yet another embodiment, use can be made of a voltage supply available in the LED driver, whereby said voltage supply is connected to the control terminal <NUM> of the light engine through a resistor of the LED driver, thus obtaining a voltage divider. Such an embodiment is schematically illustrated in <FIG>.

<FIG> schematically shows a lighting system <NUM> according to the present invention, the lighting system <NUM> comprising an LED driver <NUM> according to the present invention and an LED light engine <NUM> according to the present invention.

In the embodiment as shown, the LED driver <NUM> comprises an input terminal <NUM> for receiving a supply power Pin, and an output terminal <NUM> for outputting a required power Pout for powering the light engine <NUM>. Pin can e.g. be provided via a rectified mains supply power or a DC power source. The output power Pout can e.g. be a DC current or a pulsed DC current for powering the LED or LEDs <NUM> of the LED light engine <NUM>. The output power Pout as generated by the LED driver <NUM> can e.g. be provided to the light engine <NUM> via the input terminal <NUM> of the LED light engine <NUM>. In the embodiment as shown, the LED driver <NUM> comprises a power converter <NUM> that is configured to convert the supply power as received via the input terminal <NUM> to the required output power Pout for powering the light engine <NUM>. The power converter <NUM> can e.g. be a switched mode power converter such as a Buck, Boost or hysteretic converter. The power converter <NUM> can e.g. be configured to supply a suitable current to the light engine <NUM> for powering the LED or LEDs <NUM>. The supplied current may return to the power converter either via a ground terminal, in which case the LED or LEDs <NUM> are connected between the input terminal <NUM> and the ground terminal <NUM>, or via a dedicated return terminal (not shown). In the embodiment as shown, the power converter <NUM> can be controlled by a control unit or controller <NUM>, e.g. comprising a processor or microcontroller. In accordance with the present invention, the LED driver <NUM> further comprises a control terminal <NUM> which can be applied by the control unit or controller <NUM> for retrieving information of the light engine <NUM> and/or for communicating with the light engine <NUM>. In an embodiment of the present invention, the control terminals as applied, e.g. control terminals <NUM> and <NUM> or terminal <NUM> may be single wire terminals or single terminals. In such case, the LED driver and the LED based light engine may have a common ground or ground terminal. In the embodiment as shown, LED driver <NUM> further comprises a circuit for determining a value of a resistance, e.g. an R-init resistance that is connected to the control terminal <NUM>. In particular, the LED driver as shown comprises a resistor <NUM> that is connected to a supply voltage V of the LED driver and which voltage V can be connected, through resistor <NUM> to the control terminal <NUM> of the LED driver <NUM>. In order to provide this connection, the control unit or controller <NUM> of the LED driver <NUM> may be configured to control the operation of a switch <NUM>. When switch <NUM> is closed, the resistor <NUM> and the R-init resistor of the light engine <NUM> form a voltage divider. Switch <NUM> may e.g. be a MOSFET or the like. As such, when the supply voltage V and the resistor <NUM> are known, the value of the resistor R-init can be determined, based on the voltage at the control terminal <NUM>. In the embodiment as shown, said voltage is provided to the control unit <NUM> via and A/D converter <NUM>. Based on the received signal from the A/D converter <NUM>, the control unit <NUM> may determine the value of the R-init resistor of the light engine and determine, e.g. by accessing a database, any configuration data for the LED driver, in order to power the particular light engine <NUM> in a suitable manner.

In the embodiment as shown in <FIG>, component <NUM> is referred to as an impedance, e.g. a resistor, which value can be determined by the LED driver <NUM> or <NUM> and which value can be used in an initialisation of the LED driver <NUM> or <NUM>. It can be pointed out that the impedance <NUM> need not be a single component but may be a combination of components. By doing so, the information that can be deduced from a value of the impedance which is measured or determined by the LED driver can be increased. This increased or additional information may e.g. be applied to further configure or initialise the LED driver, so as to better drive the LED light engine.

As an example, the impedance can e.g. be a resistor with a parallel capacitor. By suitable application of a current to the terminal <NUM> and monitoring the voltage at the terminal, or applying a voltage to the terminal <NUM> and monitoring the current to the terminal, one can assess both the values of the resistor and the capacitor. In this particular example, the values can e.g. be detemined based on a time constant at which the generated voltage or current changes. In particular the rise or fall timing can be used to determine the time constant of the RC (resistor-capacitor) circuit that is applied as impedance. Known measurement methods for determining an impedance value or values can be applied. In such embodiment, the resistor value can e.g. be used to set a nominal current to be supplied to the light engine, whereas the capacitor value may e.g. be applied to define a nominal color set point to be generated or another parameter associated with the operation of the LED driver. As will be appreciated, other examples of impedances having multiple components can be considered as well, e.g. including more complex arrays or resistors or capacitors or other components such as Zener diodes.

Based on the impedance value, the LED driver <NUM> or <NUM> may thus be configured or initialized for powering the LED light engine <NUM>. Such a configuration or initialization may e.g. involve comparing the determined impedance value with a list of impedance values in a database, e.g. a lookup table. For the example of the resistor and capacitor, the LED driver can e.g. be provided with a lookup table have a list of possible resistor and capacitor values and the associated operating parameters. Such a lookup table may e.g. comprise, for each of the possible impedance values, the required power settings for powering the LED light engine. Such power settings may e.g. include a maximum output voltage, a maximum output current, a nominal current value, a color set point, etc. Such a database may be readily available in the LED driver, e.g. in a memory unit of the control unit <NUM>. Alternatively, the LED driver <NUM> or <NUM> may be configured to access an external database via any suitable means of communications. In such embodiment, the determined impedance value can be used as an identifier for selecting one or more operating parameters for the LED driver. By doing so, a more detailed set of operating parameters can be selected. This can be illustrated as follows: the detection of an impedance value or values can be considered an analog detection. In order for this detection or determination to be reliable, the amount of values that can be chosen may be rather limited, e.g. in a range between <NUM> and <NUM> or <NUM>. In case of a one to one correspondence between a determined impedance value and an operating parameter, the selection of values for the operating parameter (e.g. an nominal current) would be limited as well. Alternatively, the impedance value or values as determined can be used as identifiers which can be associated with sets of operating parameters that are e.g. stored in a remote database or in a memory unit of the LED driver. In such case, a particular resistance value may e.g. be associated with a particular set of operating parameters, e.g. including a nominal current, a maximum current, a nominal color set point, a control range for the color set point, a path in a color space to be followed, etc. Such a set of parameters may e.g. be referred to as an illumination profile. In such case, the database or the LED driver memory unit can e.g. comprise n different illumination profiles that can be used by the LED driver, whereby an impedance value, e.g. a resistance value or an capacitor value, or a combination of both values, is used to select the appropriate illumination profile.

In an embodiment of the present invention, the LED light engine may be configured in such manner that the initialization method according to the present invention can be performed using only a single connection between the LED driver and the LED light engine. In such embodiment, the initialization method is thus performed by connecting a single control terminal of the LED driver to a single control terminal of the LED light engine.

In such embodiment, the LED light engine may still include a tag or even a processor or processing unit. In accordance with an embodiment of the present invention, such a tag or processor can then be powered or supplied with a supply voltage via the single connection. <FIG> schematically shows such an embodiment of an LED light engine <NUM> according to the present invention.

In the embodiment as shown, the LED light engine <NUM> comprises one or more LEDs <NUM> which can e.g. be powered via a power input terminal <NUM>. In the embodiment as shown, the LED light engine <NUM> further comprises a control terminal <NUM> which can be used for communicating with an LED driver, e.g. for exchanging information <NUM> during an initialization process of the LED driver. The control terminal <NUM> is connected to a processing or control unit <NUM> of the LED light engine, said processing or control unit <NUM> being configured to communicate, via the communication terminal <NUM> with an LED driver to which it can be connected. The processing or control unit <NUM> comprises a power-supply pin or terminal <NUM>. In the embodiment as shown, the LED light engine further comprises an energy storage element <NUM>, e.g. a capacitance or capacitor, which can be charged via the control terminal <NUM> and which is connected to the power-supply pin or terminal <NUM> of the processing or control unit <NUM>.

In the embodiment as shown, the processing or control unit <NUM> may thus be powered by the energy storage element <NUM>, the energy storage element <NUM> being chargeable via the control terminal <NUM>. In order to apply the above described initialisation method to an LED light engine <NUM> as shown in <FIG>, the initialisation method may e.g. comprises the step of outputting, prior to the outputting of a communication signal as provided in step <NUM> of the initialisation method, a power supply signal from the control terminal of the LED driver, e.g. terminal <NUM>, to the control terminal of the LED based light engine, e.g. control terminal <NUM>. The outputting of a power supply signal may e.g. comprise providing a sufficiently high DC voltage at the control terminal of the LED driver, in order to charge the energy storage element <NUM>. It can be noted that the power supply signal used to charge the energy storage element <NUM> can also be considered to be part of the communication signal. By doing so, the voltage at the power-supply pin or terminal <NUM> can be raised up to a level at which the processing or control unit <NUM> may start operating, e.g. start communicating with the LED driver.

By enabling the LED light engine to be powered via the control terminal, there is no longer a need to connect the LED driver and the LED light engine via two connections; a single connection is thus sufficient.

In addition to being provided with a tag or control unit or R-init resistor or impedance, LED based lighting applications such as LED light engines may also be equipped with temperature sensors. Such sensor or sensors may e.g. be used to assess the operating temperature of the LED or LEDs of the LED light engine. Knowledge of the operating temperature may e.g. be used to adjust or control the current to the LED or LEDs, in order to ensure a desired or required lifetime of the LED or LEDs.

According to an aspect of the present invention, there is provided an LED based light engine or LED light engine that further includes a temperature sensor, e.g. a temperature dependent resistor such as an NTC (negative temperature coefficient) resistor. Such an LED light engine may e.g. be combined with an LED driver according to the present invention, to form a lighting system according to the present invention. A temperature sensor such as an NTC may be applied in an LED based light engine according to the present invention to determine or monitor a temperature of the LED based light engine. By doing so, one can ensure that the LED based light engine is not operated above a maximum temperature. Based on the temperature as sensed, the LED driver may, when needed, adjust the power supplied to the LED based light engine, in order to keep the LED based light engine in a safe operating area. In an embodiment, a temperature sensor such as an NTC may be used in an LED based light engine according to the present invention to determine a die temperature of one or more LEDs of the LED based light engine. Knowledge of the die temperature of an LED may be used by the LED driver to determine the amount of light or light intensity emitted or generated by the LED, as the generated amount of light depends both on the temperature of the die and the current through the LED. An accurate knowledge of the amount of light as generated, obtained by means of the die temperature measurement, enable a more accurate generation of a desired colour by the LED based light engine; a desired colour is typically generated by a combination or mixing the generated light of a plurality of LEDs having a different colour. As such, the more accurate the actual amount of light as generated by such plurality of LEDs is known, the more accurate a desired or required combination or mixing of generated light can be obtained.

In an embodiment of the present invention, the temperature sensor (or sensors) is arranged in such manner in the LED light engine that no additional or separate terminal is required to assess or read-out the temperature sensor.

Various options exist to realise such an arrangement.

A first example of an LED light engine according to the present invention that includes a temperature sensor is schematically shown in <FIG>.

<FIG> schematically shows an LED light engine <NUM> that comprises one or more LEDs <NUM> which can e.g. be powered via a power input terminal <NUM>. In the embodiment as shown, the LED light engine <NUM> further comprises a control terminal <NUM> which can be used for communicating with an LED driver. In the embodiment as shown, the LED light engine <NUM> comprises a temperature sensor <NUM> that is connected to the control terminal <NUM>. In the embodiment as shown, the temperature sensor <NUM> is assumed to be a temperature dependent resistor, i.e. a resistor of which the resistance value changes. As such, assuming a temperature operating range from T1 to T2, (e.g. from -<NUM> to <NUM>), the resistance value of the temperature sensor <NUM> will vary from a value R1 to R2.

In the embodiment as shown, the LED light engine does not comprise an R-init resistor or impedance, nor does it include a processing or control unit such as control unit <NUM> as shown in <FIG>. Nevertheless, the LED light engine <NUM> as schematically shown may still be applied in an initialisation method according to the present invention.

As illustrated in <FIG>, the initialisation method according to the present invention comprises the step <NUM> of initialising an LED driver based on a detected impedance value.

As described above, such a configuration or initialization may e.g. involve comparing the determined impedance value with a list of impedance values in a database, e.g. a lookup table.

Such a database may e.g. comprise, for each of the possible impedance values, the required power settings for powering the LED light engine.

When the resistance value of the temperature sensor <NUM> is selected in such manner that it does not correspond to any value available in the impedance value database, the initialisation method may involve initialising the LED driver according to its nominal setting or operating conditions.

As such, an embodiment of the initialisation method according to the present invention may involve the following steps:
In case it is determined that the control terminal of the LED light engine is not a communication terminal, the LED driver may:.

In order to determine the resistance value of the temperature sensor <NUM>, similar methods as described above with respect to the determination of the R-init value may be applied. In particular, the LED driver (not shown) that needs to be initialised may apply a suitable signal (a voltage or current) <NUM> to the control terminal <NUM>, in order to determine the resistance value.

By applying the above, in accordance with an embodiment of the present invention, an LED driver may be configured, based on a senses impedance value of a temperature sensor, e.g. a temperature resistor. As will be appreciated by the skilled person, the temperature dependency of the temperature resistor may need to be taken into account to assess whether or not the sensed impedance is an R-init resistor or a temperature dependent resistor such as an NTC. With reference to the above given example, the resistance range or characteristic of the temperature sensor <NUM>, i.e. the resistance range from R1 to R2, should be selected in such manner that it does not overlap with resistance values present in the database of R-init values that is applied or accessed by the LED driver.

In an alternative embodiment, illustrated in <FIG>, the LED based light engine according to the present invention comprises both a tag or processing unit and a temperature sensor. Such embodiment can e.g. be considered a combination of the embodiments of <FIG>. In the embodiment as shown, the LED based light engine <NUM> comprises one or more LEDs <NUM> which can e.g. be powered via a power input terminal <NUM>. In the embodiment as shown, the LED light engine <NUM> further comprises a control terminal <NUM> which can be used for communicating with an LED driver, e.g. for exchanging information <NUM> during an initialization process of the LED driver. The control terminal <NUM> is connected to a processing or control unit <NUM> of the LED light engine, said processing or control unit <NUM> being configured to communicate, via the control terminal <NUM> with an LED driver to which it can be connected. The processing or control unit <NUM> comprises a power-supply pin or terminal <NUM>. In the embodiment as shown, the LED light engine further comprises an energy storage element <NUM>, e.g. a capacitance or capacitor, which can be charged via the control terminal <NUM> and which is connected to the power-supply pin or terminal <NUM> of the processing or control unit <NUM>.

In the embodiment as shown, the processing or control unit <NUM> may thus be powered by the energy storage element <NUM> as described above, with reference to <FIG>.

In the embodiment as shown, the LED light engine <NUM> further comprises a temperature sensor <NUM>, which can e.g. be similar or the same as the temperature sensor <NUM> of <FIG>. The temperature sensor <NUM> may e.g. be a temperature dependent resistor, i.e. a resistor of which the resistance value changes. As such, assuming a temperature operating range from T1 to T2, (e.g. from -<NUM> to <NUM>), the resistance value of the temperature sensor <NUM> will vary from a value R1 to R2. In the embodiment as shown, the temperature sensor <NUM> is connected to the control terminal <NUM> of the LED light engine <NUM> and can be read-out in a similar manner as discussed with reference to <FIG>.

In the embodiment as shown, the LED light engine further comprises a diode <NUM> that is configured to ensure that the energy storage element <NUM>, e.g. a capacitance, is not discharged or depleted via the temperature sensor <NUM>.

In <FIG>, yet another embodiment of a LED light engine according to the present invention is schematically shown. <FIG> schematically shows an LED light engine <NUM> that comprises one or more LEDs <NUM> which can e.g. be powered via a power input terminal <NUM>. In the embodiment as shown, the LED light engine <NUM> further comprises a control terminal <NUM> which can be used for communicating with an LED driver (not shown), as indicated by the arrow <NUM>. In the embodiment as shown, the LED light engine <NUM> comprises an R-init resistor <NUM> connected to a control terminal <NUM>, in a similar manner as in the LED light engine <NUM> as described above.

In the embodiment as shown, the LED light engine <NUM> further comprises a temperature dependent resistor <NUM> which is connectable in parallel to the R-init resistor <NUM>. In the embodiment as shown, the LED light engine <NUM> comprises a circuit <NUM>, <NUM>, <NUM>, that is configured to connect the temperature sensing element <NUM> in parallel to the R-init resistor <NUM>. In the embodiment as shown, the circuit <NUM>, <NUM>, <NUM> comprises a switch <NUM> and a resistor pair <NUM>, <NUM> forming a voltage divider, the circuit being configured to connect the temperature dependent resistor <NUM> in parallel to the R-init resistor <NUM>, when a supply voltage for the LED light engine <NUM> is provided to the supply terminal <NUM>. In particular, the resistor divider <NUM>, <NUM> and switch <NUM> are configured to close the switch <NUM> when a supply voltage is present at terminal <NUM>, thereby connecting the temperature sensing element <NUM>, e.g. an NTC, in parallel to the R-init resistor <NUM>. In case no supply voltage is present at the terminal <NUM>, switch <NUM> will be in an open state. In such state, the temperature sensing element <NUM> cannot be detected or observed at the control terminal <NUM>. By doing so, the circuit <NUM>, <NUM>, <NUM> ensures that, during an initialisation, only the R-init resistor <NUM> is observed or detected at the control terminal <NUM>. As such, the aforementioned initialisation process may be performed, whereby an LED driver that is connected to the control terminal <NUM> may be initialised based on a sensed or determined value of the R-init resistor <NUM>. Once the initialisation process of the LED driver is performed, the LED driver's power output terminal may be connected to the power input terminal <NUM> of the LED based light engine <NUM>. As a result, from then on, the impedance as measured at the control terminal <NUM> also includes the impedance of the temperature sensing element <NUM>, e.g. an NTC resistor. As such, during normal operation, the sensed impedance can then be used to assess the temperature of the LED light engine that is operated. Note that in this case, the same control terminal of the LED light engine has a dual functionality, depending on the operating mode:.

By doing so, there is no additional terminal needed at the LED driver or at the LED based light engine to assess, during normal operation, the temperature of the LED based light engine. The design and manufacturing of both the LED driver and the LED based light engine may thus be simplified, more compact and less expensive.

In the embodiment as shown in <FIG>, the LED light engine <NUM> comprises an R-init resistor <NUM> which can be sensed, during an intialisation process, in order to initialize an LED driver that is connected to the control terminal <NUM>. Alternatively, the LED based light engine <NUM> can be equipped with a tag or processing unit, in a similar manner as e.g. shown in <FIG> or <FIG>.

In a similar manner as described with respect to <FIG>, such an embodiment may be combined with a temperature resistor and circuit as shown in <FIG>, thereby enabling the control terminal of the LED light engine to have a dual functionality.

The various embodiments of the LED driver and LED light engine as describe above enable to minimize the number of terminals for the LED driver and LED light engine, while still maintaining the flexibility of initializing the LED driver, i.e. ensuring that the power as supplied by the LED driver matches or suits the LED light engine.

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. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the invention.

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.

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

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

The terms program, software application, and the like as used herein, are defined as a sequence of instructions designed for execution on a computer system. A program, computer program, or software application may include a subroutine, a function, a procedure, an object method, an object implementation, an executable application, an applet, a servlet, a source code, an object code, a shared library/dynamic load library and/or other sequence of instructions designed for execution on a computer system.

Claim 1:
Method of initializing an LED driver (<NUM>, <NUM>) to power an LED light engine (<NUM>, <NUM>, <NUM>, <NUM>) comprising one or more LEDs (<NUM>, <NUM>, <NUM>, <NUM>), the method comprising:
- connecting a control terminal (<NUM>, <NUM>) of the LED driver to a control terminal (<NUM>, <NUM>, <NUM>, <NUM>) of the LED light engine, (<NUM>);
characterized by:
- determining whether the control terminal of the LED light engine is a communication terminal by outputting a communication signal from the control terminal of the LED driver to the control terminal of the LED light engine, (<NUM>);
- establishing that the control terminal of the LED light engine is a communication terminal if a reply communication signal to the communication signal is received within a predetermined period, (<NUM>), wherein the control terminal of the LED light engine is not a communication terminal when no reply to the communication signal is received within the predetermined period;
wherein:
- if the control terminal of the LED light engine is a communication terminal, perform an initialisation of the LED driver by exchanging configuration data between the LED driver and the LED light engine, (<NUM>);
- if the control terminal of the LED light engine is not a communication terminal, determining an impedance value (<NUM>) observed at the control terminal of the LED light engine and performing an initialisation of the LED driver based on the impedance value, (<NUM>).