Patent Publication Number: US-9848468-B1

Title: Visible light communication enabling lighting driver

Description:
RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 62/268,172, filed Dec. 16, 2015, and titled “Visible Light Communication Enabled Lighting Driver,” the entire content of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to lighting drivers and fixtures, and more particularly to lighting drivers for use with lighting fixtures to enable visible light communication by the lighting fixtures. 
     BACKGROUND 
     Communicating with LED based lighting fixtures involves varying the current that flows through the LED light sources of the lighting fixtures based on the information being sent. Varying of the current to reflect the information being sent results in changes in the intensity of light emitted by the LED light sources. To avoid detection of the change in the emitted light by occupants, the varying of the current needs to be performed at a fast enough rate. However, most constant current drivers (e.g., switching regulators) are unable to quickly change their current output because of a slow control loop. While a slow control loop may be desirable during an operation of a light fixture to illuminate an area (e.g., to avoid flicker), slow change in current is undesirable during visible light communication due to the likelihood of detection of the change by occupants. 
     Thus, a driver that allows relatively fast current changes during visible light communication and relatively slow current changes during illumination by LED light sources is desirable. 
     SUMMARY 
     The present disclosure relates generally to lighting drivers and fixtures, and more particularly to lighting drivers for use with lighting fixtures to enable visible light communication by the lighting fixtures. In an example embodiment, a visible light communication enabling lighting driver includes a processor configured to generate a compensator signal based on a first signal during a constant current mode and based on a second signal during a constant voltage mode. The first signal corresponds to a current through an LED light source coupled to an output of the driver, and the second signal corresponds to a voltage at the output of the driver. The driver further includes a controller to control, based on the compensator signal, an amount of power provided by the driver to the LED light source. The driver also includes a constant current source circuit to be coupled to the LED light source. During the constant current mode, a flow of the current through the constant current source circuit is disabled by the processor, and, during the constant voltage mode, disabling the flow of the current through the constant current source circuit disables a flow of the current through the LED light source. 
     In another example embodiment, a visible light communication enabled lighting fixture includes an LED light source to emit a light and a driver. The driver includes a processor configured to generate a compensator signal based on a first signal during a constant current mode and based on a second signal during a constant voltage mode. The first signal corresponds to a current through the LED light source coupled to an output of the driver. The second signal corresponds to a voltage at the output of the driver. The driver further includes a controller to control, based on the compensator signal, an amount of power provided by the driver to the LED light source. The driver also includes a constant current source circuit coupled to the LED light source. During the constant current mode, a flow of the current through the constant current source circuit is disabled by the processor, and, during the constant voltage mode, disabling the flow of the current through the constant current source circuit disables a flow of the current through the LED light source. 
     In another example embodiment, a method of enabling visible light communication by a lighting fixture includes providing, by a driver, power to an LED light source and generating, by a processor of the driver, a compensator signal based on a first signal during a constant current mode and based on a second signal during a constant voltage mode. The first signal corresponds to a current through the LED light source coupled to an output of the driver, and the second signal corresponds to a voltage at the output of the driver. The method further includes controlling based on the compensator signal, by a controller, an amount of power provided by the driver to the LED light source, and controlling, by the processor, a flow of the current through the constant current source circuit. During the constant current mode, the flow of the current through the constant current source circuit is disabled, and, during the constant voltage mode, enabling the flow of the current through the constant current source circuit enables a flow of the current through the LED light source and disabling the flow of the current through the constant current source circuit disables the flow of the current through the LED light source. 
     These and other aspects, objects, features, and embodiments will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG. 1  illustrates a lighting fixture including a driver according to an example embodiment; 
         FIG. 2  illustrates the lighting fixture of  FIG. 1  including a constant current source circuit according to an example embodiment; 
         FIG. 3  illustrates the lighting fixture of  FIG. 1  including a constant current source circuit according to another example embodiment; 
         FIG. 4  illustrates the lighting fixture of  FIG. 1  including a constant current source circuit according to another example embodiment; and 
         FIGS. 5A and 5B  illustrate a flowchart of a method of operating the driver of the lighting fixture of  FIGS. 1-4  according to an example embodiment. 
     
    
    
     The drawings illustrate only example embodiments and are therefore not to be considered limiting in scope. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Additionally, certain dimensions or placements may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements. 
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     In the following paragraphs, particular embodiments will be described in further detail by way of example with reference to the figures. In the description, well known components, methods, and/or processing techniques are omitted or briefly described. Furthermore, reference to various feature(s) of the embodiments is not to suggest that all embodiments must include the referenced feature(s). 
     Turning now to the drawings,  FIG. 1  illustrates a lighting fixture  100  including a driver  102  according to an example embodiment. The lighting fixture  100  includes the driver  102  and an LED light source  104 . The driver  102  provides power to the LED light source  104 . The LED light source  104  may emit light to illuminate an area. In some example embodiments, the LED light source  104  may include a number of LEDs and the light emitted by the LED light source  104  may be used in visible light communication. For example, the LED light source  104  may emit light for visible light communication to identify the lighting fixture  100  during commission of the lighting fixture  100 . 
     In some example embodiments, the driver  102  may operate in a constant current mode or in a constant voltage mode (i.e., a visible light communication (VLC) mode). For example, the mode of operation of the driver  102  may be selected based on a mode selection signal, Mode. To illustrate, the signal, Mode, may have a first value corresponding to the constant current mode and a second value corresponding to the constant voltage mode. The mode selection signal, Mode, may be provided to the driver  102  by a user, for example, via a wireless interface device coupled to or integrated in the driver  102  or by other means such as a wired connection or a physical interface on the driver  102 . 
     In some example embodiments, the driver  102  receives power from an alternating current (AC) power source via a connection  106  and provides power to the LED light source  104 . The driver  102  may include a controller  112 , a processor  114  (e.g., a microprocessor), an optocoupler  120 , and a constant current (CC) source circuit  140 . The controller  112  may control the amount of power that is provided to the LED light source  104  based on feedback information received from the processor  114  through the optocoupler  120 . 
     To illustrate, the driver  102  may include a rectifier  108  and a transformer  110 . An AC power signal is received by the rectifier  108  via the connection  106 , and the rectifier  108  may rectify the AC signal and output a rectified signal. The rectified signal from the rectifier  108  is provided to the transformer  110 , which delivers power to the LED light source  104 . The transformer  110  may deliver power to the LED light source  104  through a diode  126  that, for example, prevents back flow of current to the transformer  110 . 
     The amount of power that the transformer  110  provides to the LED light source  104  is controlled based on a control signal provided by the controller  112 . For example, the controller  112  may provide a control signal through a PWM output of the controller  112 . To illustrate, a transistor  136  is coupled to the transformer  110  such that the operation the transformer  110  depends on the state of the transistor  136  (e.g., whether the transistor  136  is on or off and durations). The transfer of power from the primary side of the transformer  110  to the secondary side of the transformer  110  depends on the state of the transistor  136  that is controlled by the controller  112 . 
     The controller  112  controls the transistor  136  using the control signal provided to the gate terminal of the transistor  136 . For example, the controller  112  may control current flow through the transistor  136  using the control signal (e.g., a PWM signal) provided via the PWM output of the controller  112 . Because the transistor  136  is controlled by the control signal provided to the controller  112  and the operation of the transformer  110  depends on the transistor  136 , the amount of power that the transformer  110  provides to the LED light source  104  may depend on the pulse width of the control signal. That is, by controlling current flow through the transistor  136  based on the pulse width of the control signal on the PWM output of the controller  112 , the controller  112  may control the amount of power provided to the LED light source  104 . 
     In some example embodiments, a Sense input of the controller  112  is used to detect whether excessive current is flowing through the primary side of the transformer  110  and thus through the transistor  136  and a resistor  138  that is in series with the transistor  136 . For example, in response to determining that excessive current is flowing through the primary side of the transformer  110 , the controller  112  may shut off current flow by turning off the transistor  136  using the control signal on the PWM output. By turning off the transistor  136 , the controller  112  may protect the driver  102  as well as the light source  104  from being damaged from excessive power. 
     In some example embodiments, the controller  112  may adjust the control signal provided to the transistor  136  based on a feedback signal received from the optocoupler  120 . The controller  112  may receive the feedback signal from the optocoupler  120  via a connector  158  (e.g., one or more electrical wires or traces) coupled to a feedback (FB) input of the controller  112 . For example, the voltage level of the feedback signal at the FB input of the controller  112  may be 1.2 volts to indicate that the power provided to the LED light source  104  should be maintained. Voltage levels below 1.2 volts may indicate the need to decrease the power, and voltage levels above 1.2 volts indicate the need to increase the power. 
     The optocoupler  120  generates the feedback signal on the connection  158  based on a compensator signal provided to the optocoupler  120 . For example, the compensator signal may be generated by the processor  114  and provided to the optocoupler  120  via a connection  150  (e.g., one or more electrical wires or traces). The processor  114  may generate the compensator signal based on the amount of current that flows through the LED light source  104 , a voltage level at the output connection  152  coupled to the LED light source  104 , or the amount of power provided to the LED light source  104 . 
     To illustrate, the processor  114  may include a compensator  116 , analog-to-digital converters (ADCs)  122 ,  124 , and a selection switch  118 . The ADC  122  converts an analog signal related to the amount of current that flows through LED light source  104  into a digital output signal that is provided to the selection switch  118 . The ADC  124  converts an analog signal related to the voltage level at the LED light source  104  (i.e., at the output connection  152 ) into a digital output signal that is provided to the selection switch  118 . The selection switch  118  may provide the digital output signal from the ADC  122  or the digital output signal from the ADC  124  to the compensator  116  based on the mode selection signal, Mode, provided to the processor  112 . To illustrate, the selection switch  118  selects the digital output signal of the ADC  122  when the signal, Mode, has the first value, and the selection switch  118  selects the digital output signal of the ADC  124  when the signal, Mode, has the second value. 
     In some example embodiments, the analog signal provided to the ADC  122  is generated based on the current flowing through a resistor  134 . To illustrate, a transistor  130  is coupled to and between the LED light source  104  and the resistor  134  forming a current path between the LED light source  104  and the resistor  134 . The transistor  130  is controlled (e.g., turned on or off) by an enable signal, ENB, generated by the processor  114  and provided to a gate terminal of the transistor  130  via a connection  156 . To illustrate, a current path through the transistor  130  may be controlled using the signal, ENB. For example, the current flow through the resistor  134  may be disabled by turning off the transistor  130  using the enable signal, ENB, and may be enabled by turning on the transistor  130  using the signal, ENB. 
     In some example embodiments, an amplifier  132  is coupled to an electrical node between the resistor  134  and the transistor  130  such that the current through the resistor  134  results in a voltage at the input of the amplifier  132 . When a current path from the LED light source  104  to ground through the CC source circuit  140  is disabled, all or substantially all of the current flowing through the LED light source  104  passes through resistor  134 . The voltage level at the input of the amplifier  132  thus corresponds to and is indicative of the amount of current flowing through the LED light source  104  and the resistor  134 . The ADC  122  receives the analog signal from the amplifier  132  via a connection  154 . A change in the amount of current flowing through the LED light source  104  is reflected in the voltage level at the input of the amplifier  132 , which results in a change in the analog signal provided to the ADC  122  by the amplifier  132 . The selection switch  118  provides the digital output signal from the ADC  122  to the compensator  116  during the constant current mode. 
     During the constant current mode, the compensator  116  may compare the digital output signal from the ADC  122  against a value (e.g., a digital value stored in a memory device of the driver  102 ) corresponding to an amount of current that is desired/expected to flow through the LED light source  104 . The compensator  116  generates the compensator signal that is provided to the optocoupler  120  via the connection  150  based on the comparison. The compensator signal may indicate whether the actual current flowing through the LED light source  104  is the same, less or more than the desired/expected amount of the current. A particular amount of the current may be desired or expected to flow through the LED light source  104  based on the configuration and/or a setting (e.g., dimmer setting) of the driver  102 . 
     To maintain a constant current amount flowing through the LED light source  104  during the constant current mode, the controller  112  may adjust and/or maintain the amount of power provided to the LED light source  104  based on the feedback signal generated from the compensator signal and provided to the FB input of the controller  112 . Because the feedback signal is derived from the compensator signal through the optocoupler  120 , the feedback signal also indicates whether the amount of actual current through the LED light source  104  is the same, less or more than the desired/expected amount of current through the LED light source  104 . By using the feedback signal received via the connection  158 , the controller  112  may adjust and/or maintain the amount of power provided to the LED light source  104  in order to maintain a constant current amount flowing through the LED light source  104 . 
     Although the CC source circuit  140  is coupled to the LED light source  104 , during the constant current mode, the current path from the LED light source  104  to ground through the CC source circuit  140  is disabled to maintain the amount of current flowing through the resistor  134  the same or close to the same as the amount of current flowing through the LED light source  104 . 
     In some example embodiments, resistors  144 ,  146  form a voltage divider circuit, and the ADC  124  receives an analog signal via a connection  160  coupled to an electrical node  142  between the voltage divider resistors  144 ,  146  and generates the digital output signal provided to the selection switch  118 . That is, a divided voltage signal of the voltage divider circuit formed by the resistors  144 ,  146 , is provided to the ADC  124 . Because the resistor  144  is coupled to the LED light source  104  at a node  148  via the connection  152 , the voltage at the node  142  coupled to the ADC  124  is related to and indicative of the actual voltage at the LED light source  104  (i.e., at the node  148 ). 
     During the constant voltage mode (i.e., VLC mode), the compensator  116  may compare the digital output signal from the ADC  124  against a value corresponding to a voltage level desired/expected at the output connection  152  (i.e., at the node  148 ) and may generate the compensator signal based on the comparison. The compensator signal may indicate whether the actual output voltage at the LED light source  104  is the same, less or more than the desired/expected voltage. The desired/expected voltage at the LED light source  104  may be determined by the processor  114  based on the voltage across the LED light source  104  as determined by the processor  114  during the constant current mode and based on design parameters of the CC source circuit  140  available to the processor  114 . To maintain a constant voltage at the LED light source  104  during the constant voltage mode, the controller  112  may adjust and/or maintain the amount of power provided to the LED light source  104  based on the feedback signal derived from the compensator signal. 
     During the constant voltage mode (i.e., during the VLC mode), the processor  114  generates a data signal, DS, at an output, DO, of the processor  114  that is coupled to the CC source circuit  140 . During the VLC mode, the current path through the resistor  134  is disabled by the processor  114  using the enable signal, ENB, that is provided to the transistor  130 . Current flow through the CC source circuit  140  to ground is adjusted (i.e., disabled, enabled, increased, and decreased) based on the voltage level of the data signal, DS, that may be an analog signal or a digital signal. When the CC source circuit  140  is enabled and the transistor  130  is turned off, the amount of current flowing through the LED light source  104  depends on design parameters of the CC source circuit  140 . During the constant current mode, the data signal, DS, is set to a level that disables the current path through the CC source circuit  140  to ground. 
     During the VLC mode, the light emitted by the LED light source  104  may be turned on or off by enabling and disabling current flow through the LED light source  104  based on the data signal, DS, that transitions between voltage levels corresponding to digital ‘1’ and ‘0’ values. By turning on or off the transistor  306  using the data signal, DS, at the output DO, the light emitted by the LED light source  104  may be turned on or off to communicate the data represented by the data signal, DS. The intensity level of the light emitted by the LED light source  104  may also be changed by changing the amount of current flowing through the LED light source  104  based on the analog voltage level of the data signal, DS, that can range between on and off levels or based on multiple digital signals as explained with respect to  FIG. 4 . By turning on or off the LED light source  104  or by changing the intensity level of the light emitted by the LED light source  104  based on the data signal, DS, the lighting fixture  100  may be used to communicate information represented by the digital signal (e.g., the identity of the lighting fixture  100 ) using visible light communication. 
     During the constant voltage mode (i.e., during the VLC mode), the driver  102  enables relatively faster switching of the light emitted by the LED light source  104  between on and off states as well as between different intensity levels, which enables visible light communication by the lighting fixture  100 . For example, during a commissioning process, the lighting fixture  100  may be used to communicate identifier information of the lighting fixture  100  using the light emitted by the LED light source  104 . Although the light emitted by the LED light source  104  may provide illumination during the constant voltage mode, operating in the constant current mode may be preferable when the emitted light is not used for visible light communication. During the constant current mode, the driver  102  enables the lighting fixture  100  to adjust the emitted light at a relatively slower rate, which reduces or avoids issues such as light flicker. The driver  102  also operates more efficiently because power is not lost in the CC source circuit  140  and in the CC source circuits  210 ,  310 ,  410  described below during the constant current mode. Thus, with the capability of operating in the two modes, the driver  102  enables the LED light source  104  to be used optimally for visible light communication and for illumination. 
     In some alternative embodiments, some of the components shown in  FIG. 1  may be combined, replaced by other components, or omitted without departing from the scope of this disclosure. For example, the transistor  130 ,  136  may be other types of transistors than shown in  FIG. 1 . Further, the LED light source  104  may include more or fewer LEDs than shown. In some alternative embodiments, the data signal, DS, may include one or more signals. 
       FIG. 2  illustrates the lighting fixture  100  of  FIG. 1  including a constant current (CC) source circuit  210  according to an example embodiment. The CC source circuit  210  may be an embodiment of the CC source circuit  140  of  FIG. 1 . Referring to  FIGS. 1 and 2 , in some example embodiments, the CC source circuit  210  includes an amplifier  202 , a transistor  204 , and a resistor  206 . The transistor  204  is coupled in series with the LED light source  104 , and the resistor  206  is coupled to the transistor  204  and forms a current path to ground. An input of the amplifier  202  is coupled to an OA output (which corresponds to the DO output shown in  FIG. 1 ) of the processor  114 . A second input of the amplifier  202  is coupled to a node  208  between the transistor  204  and the resistor  206 . When the transistor  204  is turned on by the output signal of the amplifier  202 , a current path from the LED light source  104  to ground is established through the transistor  204  and the resistor  206 . The current path to ground can be disabled by turning off the transistor  204 . 
     During the constant voltage mode, the current path through the resistor  134  is disabled, and the voltage level at the OA output of the processor  114  is reflected at the node  208 . Because the voltage level at the OA output is reflected at the node  208 , the current flowing through the resistor  206 , and thus through the LED light source  104 , is a constant current that is determined based on the voltage level at the node  208  and the resistance of the resistor  206 . Changing the voltage level at the node  208  changes the current through the resistor  206 , and thus through the LED light source  104 . By varying the voltage level of the data signal, DS, at OA output (e.g., analog voltage levels generated using a digital-to-analog converter (DAC) in the processor  114 ), the transistor  204  may linearly change the voltage level at the node  208 , thereby changing the current through the LED light source  104 . 
     During the constant voltage mode, relatively fast change in the current flowing through the LED light source  104  may be achieved because the feedback path through the ADC  124  is able to maintain the voltage at the node  148  (i.e., at the connection  152 ) at a reasonably constant level accounting for the voltage across the LED light source  104  and across the CC source circuit  210 . 
     Although particular components are shown in  FIG. 2 , in some alternative embodiments, some components may be combined or replaced with other components without departing from the scope of this disclosure. 
       FIG. 3  illustrates the lighting fixture  100  of  FIG. 1  including the CC source circuit  310  according to another example embodiment. The CC source circuit  310  may be an embodiment of the CC source circuit  140  of  FIG. 1 . Referring to  FIGS. 1 and 3 , in some example embodiments, the CC source circuit  310  includes a resistor  302 , a transistor  304 , a transistor  306 , and another resistor  308 . During the constant voltage mode, the current path through the resistor  134  is disabled, and because the voltage across the resistor  308  is limited to the base-emitter voltage of the transistor  304 , the current flowing through the transistor  304 , and thus through the LED light source  104 , is a constant current that is determined based the base-emitter voltage of the transistor  304  and the resistance of the resistor  308 . By turning on or off the transistor  306  using the data signal, DS, at the output OA (which corresponds to the DO output shown in  FIG. 1 ), the light emitted by the LED light source  104  may be turned on or off to communicate the data in the data signal, DS. 
     During the constant voltage mode, relatively fast change in the current flowing through the LED light source  104  may be achieved because the feedback path through the ADC  124  is able to maintain the voltage at the node  148  (i.e., at the connection  152 ) at a reasonably constant level accounting for the voltage across the LED light source  104  and across the CC source circuit  310 . 
     Although particular components are shown in  FIG. 3 , in some alternative embodiments, some components may be combined or replaced with other components without departing from the scope of this disclosure. 
       FIG. 4  illustrates the lighting fixture  100  of  FIG. 1  including a CC source circuit  410  according to another example embodiment. The CC source circuit  410  may be an embodiment of the CC source circuit  140  of  FIG. 1 . Referring to  FIGS. 1 and 4 , in some example embodiments, the CC source circuit  410  includes multiple CC source sub-circuits  402 ,  404 ,  406 . Each of the CC source sub-circuits  402 ,  404 ,  406 , included in the CC source circuit  410  of  FIG. 4  may correspond to the CC source circuit  310  of  FIG. 3 , where each CC source sub-circuit  402 ,  404 ,  406  is controlled by a respective data signal, DSA, DSB, DSC, (collectively, the data signal, DS) at outputs, OA, OB, or OC, (which correspond to the DO output of  FIG. 1 ) of the processor  114 . For example, the same data may be sent using data signals, DS, on all three outputs, OA, OB, or OC. Alternatively, the data signal, DS, at one of the outputs, OA, OB, or OC, may be set to a fixed signal level while the data signal, DS, at the remaining outputs, OA, OB, OC, have changing levels. 
     As another example, the data signal, DS, at two of the outputs, OA, OB, OC, may be set to the same or different fixed signal levels while the data signal, DS, at the remaining output, OA, OB, or OC, has changing levels. As yet another example, the data signal, DS, at all of the outputs, OA, OB, OC, may have changing levels. The intensity level of the light emitted by the LED light source  104  changes based on the voltage levels of the data signal, DS, at the outputs, OA, OB, OC, where the intensity level of the light communicates the information in the data signal, DS, using visible light communication. As described above, the data signal, DS, may be multiple data signals (e.g., digital or analog signals), where a respective one of the multiple signals is provided on each of the outputs, OA, OB, OC, of the processor  114 . 
     The feedback path through the ADC  124  continues to operate to maintain the voltage at the node  148  at a constant level accounting for the voltage across the LED light source  104  and across the CC source circuit  140 . 
     During the constant voltage mode, relatively fast change in the current flowing through the LED light source  104  may be achieved because the feedback path through the ADC  124  is able to maintain the voltage at the node  148  (i.e., at the connection  152 ) at a reasonably constant level accounting for the voltage across the LED light source  104  and across the CC source circuit  410 . 
     Different components of the driver  102  may be combined or replaced with functionally equivalent components without departing from the scope of this disclosure. Further, some functions described above may be implements using hardware, software, or a combination thereof. In some alternative embodiments, the CC source circuit  410  may have more or fewer than three CC source sub-circuits. 
       FIGS. 5A and 5B  (collectively “ FIG. 5 ”) illustrate a flowchart of a method  500  of operating the driver of the lighting fixture  100  of  FIGS. 1-4  according to an example embodiment. Referring to  FIGS. 1-5 , the method  500  includes, at  502 , resetting and restoring configurations of the driver  102 , which includes loading programmed settings from non-volatile memory, determining how the user wants the driver  102  to start (i.e., full power, last settings, custom level) and running a regulation/compensator algorithm/operations by the processor  114  to produce the control signal (e.g., a PWM signal) by the controller  112 . At step  504 , a determination is made whether the VLC mode (i.e., constant voltage mode) is selected via the mode selection input signal, Mode. If the VLC mode is not selected (i.e., constant current mode is selected), the method  500  continues at step  506  with reading/determining the analog current level (i.e., current through the light source  104 ) through the ADC  122  of the processor  114 . At step  508 , the method  500  continues with performing the compensation algorithm/operation on a number of samples (from the ADC  122 ) of the current by comparing against the expected/desired current amount. At step  510 , the method  500  includes performing adjustment of the current through the LED light source  104  using the PWM signal (or another control signal) provided to the transformer  126 , where the PWM signal is generated based on the feedback signal received by the controller  112  from the optocoupler  120  via the feedback (FB) input of the controller  112 . 
     If the VLC mode (i.e., constant voltage mode) is selected as determined at step  504 , the method  500  includes, at step  512 , changing the current setpoint (i.e., expected/desired amount of current through the LED light source  104 ) to equal to the hardware current (i.e., the maximum current the driver  102  is designed to provide a load) and waiting for regulation (i.e., a complete feedback cycle through the controller  112 , the transformer  110 , the LED light source  104 , and the ADC  122 ). At step  514 , the method  500  includes measuring/determining the voltage of the LED light source  104  under the adjusted current level (i.e., current setpoint), for example, as described above with respect to  FIG. 1 . At step  516 , the method  500  includes adding a predetermined offset (i.e., based on the expected voltage drop across the CC source circuit  140 ,  210 ,  310 ,  410 , which is known because of known parameter values of the CC source circuit  140 ,  210 ,  310 ,  410 ) to the measurement from the step  514  and making the sum the new voltage regulation setpoint. 
     At step  518 , the method  500  includes changing a regulation signal (i.e., signal provided to the selection switch  118  based on the selection signal, Mode,) from load current to load voltage and disabling the constant current path (i.e., turning off the transistor  130 ), which changes the operation mode of the processor  114  from the constant current mode to the constant voltage mode (i.e., VLC mode). 
     At step  520 , the method  500  includes running the compensation algorithm/operations by the compensator  116  on the most recent ‘n’ voltage samples (from the ADC  124 ) by comparing the samples against expected/desired voltage the LED light source  104 . The number of samples, n, depends on a desired level of accuracy as should be understood by those of ordinary skill in the art with the benefit of this disclosure. At step  522 , the method  500  includes enabling the constant current path (i.e., current path through the CC source  140 ,  210 ,  310 ,  410 ) depending on the data signal, DS, at the output, OA, of the processor  112  with respect to  FIGS. 1-3 , and at the outputs, OA, OB, OC, of the processor  112  with respect to  FIG. 4 . At step  524 , the method  500  includes determining whether the VLC mode is deselected (i.e., whether the mode selection signal, Mode, has changed and no longer corresponds to the VLC mode). 
     If the VLC mode has not changed based on the determination at step  524 , the method  500  returns to and continues with step  520 . If the VLC mode is no longer selected based on the determination at step  524 , the method  500  continues with step  526  by allowing the capacitor  128  to discharge before enabling the constant current path (i.e., the path through the transistor  130 ) and changing the regulation signal (i.e., signal provided to the selector  118  based on the mode selection signal, Mode,) from load voltage to load current, which changes the operation mode of the processor  114  from the constant voltage mode (i.e., VLC mode) to the constant current mode. The method  500  returns to step  506  if the VLC mode is no longer selected. Alternatively, the step  500  may return to step  504 . 
     Although a particular order of steps of the method  500  are shown in  FIGS. 5A and 5B , in some alternative embodiments, some of the steps may be performed in a different order than shown without departing from the scope of this disclosure. In some example embodiments, some steps of the method  500  may be skipped or otherwise omitted without departing from the scope of this disclosure. 
     Although particular embodiments have been described herein, the descriptions are by way of example. The features of the embodiments described herein are representative and, in alternative embodiments, certain features, elements, and/or steps may be added or omitted. Additionally, modifications to aspects of the embodiments described herein may be made by those skilled in the art without departing from the spirit and scope of the following claims, the scope of which are to be accorded the broadest interpretation so as to encompass modifications and equivalent structures.