Abstract: An Illumination system comprising a light source (1010) and a control unit (CU1) for controlling the light source is described. The control unit is arranged to operate in a first state to control a first illumination parameter of the light source and in a second state to control a second illumination parameter, a transition from the first state to the second state is obtained by providing a pulling force to a control element of the control unit.

Abstract: Various embodiments relate to a circuit arrangement for operating at least one discharge lamp. In order to prevent intrinsic flicker at low dimming settings and low temperatures, according to various embodiments, a direct current which is fed into the discharge lamp so as to avoid striated discharges at relatively high dimming settings is reduced or entirely eliminated.

Abstract: An array of LEDs having output light in different wavelength ranges. A control circuit connected to the array includes a temperature variable resistance component and a switch selectively connecting the component to the array. The control circuit limits the current applied to at least some of the LEDs during initial energization of the LEDs prior to steady-state operation of the LEDs. Variations over time of a color correlated temperature (CCT) of output light of the energized array are reduced.

Abstract: There is provided a discharge lamp controlling apparatus mounted on vehicles or others. The apparatus includes a discharge lamp, a power control section, a signal inputting section, and a storage which are united with each other. The signal inputting section allows a power command signal to be inputted from the outside of the apparatus, the power command signal being for commanding the value of power supplied to the discharge lamp, and extracts from the inputted power command signal commanded power values which command the value of the power. The storage section stores therein, at least, the newest commanded power value among the extracted commanded power values. The power control section controls the power supplied to the discharge lamp based on the newest command values stored in the storage section.

Abstract: Apparatus and methods for detecting lamp failure in a rapid thermal processing (RTP) tool are provided. Lamp failure detection systems are provided that can accommodate DC and/or AC voltages. The systems sample voltage signals along a circuit path formed by at least two serially connected lamps, calculate a voltage drop across the first lamp of the at least two serially connected lamps based on the sampled voltage signals, and determine whether a lamp failure has occurred based on a relationship between the voltage drop across the first lamp and a total voltage applied to the circuit path.

Abstract: A filter device (10) for filtering high-frequency interferences, such as due to switching flanks of a DC converter, has a current path (4) between an input (2) and an output (3), and an inductor (L) in the current path (4), wherein the inductor (L) is disposed in the current path (4) as a first component and is connected to the input (2), and wherein a reverse polarity protective diode (D) is disposed in series with the inductor (L) downstream thereto.

Abstract: A device (7) is caused to enter an active mode by determining a coarse level of interest; determining a more refined level of interest in response to determining the coarse level of interest; and causing a device (7) to enter an active mode, in response to determining the refined level of interest.

Abstract: A lighting device for a solid-state light source includes a DC power source circuit section which flows a current in a solid-state light source by using a charging/discharging current or either one of charging and discharging currents of a inductor connected in series to a switching element, and a current control section having a first switching control unit for changing an ON width of the switching element depending on a dimming level and a second switching control unit for controlling an ON timing of the switching element. The second switching control unit changes a time until the switching element is turned on from a zero-crossing of the discharging current of the inductor such that the time becomes substantially the same when the dimming level is equal to or greater than a predetermined level, and the time becomes longer when the dimming level is less than the predetermined level.

Abstract: The embodiments of the present circuit and method disclose a circuit to bypass a target circuit when an open status is detected. The present circuit may comprise a sample circuit, a monitoring circuit and a bypass circuit. The sample circuit may comprise a capacitor coupled to the target circuit. The monitoring circuit may be coupled to the capacitor and may have an output configured to generate an output signal selectively indicating the open status. The bypass circuit may comprise a switch, wherein the switch has a control terminal coupled to the output of the monitoring circuit and wherein the switch may be configured to be selectively turned ON to bypass the target circuit in accordance with the output of the monitoring circuit.

Abstract: A lighting device has a direct-current power generation circuit, a rectangular-wave generation circuit, a pulse generating circuit, lamp-voltage detection means, and pulse-generation command means. The direct-current power generation circuit generates direct-current power from external power. The rectangular-wave generation circuit converts the direct-current power to rectangular-wave alternating-current power. The pulse generating circuit superposes high-voltage pulses on the rectangular-wave power output from the rectangular-wave generation circuit and starts a discharge lamp. The lamp-voltage detection means detects, in digital form, a lamp voltage supplied to the discharge lamp. The pulse-generation command means issues a pulse generation command to the pulse generating circuit when the value detected by the lamp-voltage detection means reaches a predetermined no-load-voltage determination level.

Abstract: A tunable LED lamp for producing biologically-adjusted light having a housing, a power circuit, a driver circuit disposed within the housing and electrically coupled with the power circuit, and a plurality of LED dies electrically coupled to and driven by the driver circuit. The driver circuit may drive the plurality of LED dies to emit a phase-shift light having a first spectral power distribution, a general illuminating light having a second spectral power distribution, and a pre-sleep light having a third spectral power distribution. The phase-shift light may be configured to affect a first biological effect in an observer, and the pre-sleep light may be configured to affect a second biological effect in an observer. The LED lamp may include an intermediate base to couple the lamp to an Edison screw base. The LED lamp may be configured to operate responsive to a three-way switch.

Abstract: A dimmable light emitting lamp configured to interface with cat-ear dimmer switches. The lamp includes one or more light emitting devices. The lamp also includes circuitry configured to receive an input voltage and provide regulated current to the one or more light emitting devices. The input voltage has a first voltage pulse that does not represent a dimming level of a dimmer switch and a second voltage pulse that represents the dimming level of the dimmer switch. The circuitry determines a first duration corresponding to a length of the first voltage pulse and a second duration corresponding to a length of the second voltage pulse responsive to first duration. The circuitry adjusts the regulated current to the light emitting devices according to the second duration to adjust output light intensity of the light emitting devices.

Abstract: A method for determining a light intensity based on current battery charge status and specified run time.

Abstract: The present disclosure provides a light emitting element drive device for driving a plurality of LED strings. The device comprises a power supply circuit, a plurality of current sources, a plurality of error amplifiers, a plurality of first diodes and a control circuit. The power supply circuit provides a driving voltage to each of the LED strings. The inverted input terminal of each error amplifier is coupled to a second terminal of the corresponding LED string. Each error amplifier output the voltage difference between the second terminal of the corresponding LED string and a first reference voltage. The anode of each first diode is coupled to the output terminal of the corresponding error amplifier, and the cathodes of the diodes are coupled to each other. The control circuit adjusts the driving voltage of the power supply circuit according to the cathode voltage of the conducted first diode.

Abstract: An electronic ballast is provided with a filament heating circuit having a Q factor clamped at a certain range of preheat frequency. An inverter circuit includes a controller and a pair of switches coupled between positive and negative terminals of a power supply. The switches respond to control signals from the controller to oscillate at an operating frequency and generate an output voltage. An inverter tank is coupled to an inverter output terminal and includes a first capacitor, a primary winding of a filament heating transformer coupled on a first end in series with the first capacitor, a second capacitor coupled to the second end of the primary winding, and a clamping circuit coupled to the second capacitor. The clamping circuit during a preheat mode of operation clamps an amplitude of the voltage across the primary winding to an amplitude of the input voltage from the power supply.

Abstract: The present invention relates to a method for driving and to an associated command and control device for discharge lamps (2), for example high pressure sodium lamps (2), supplied by an alternating current electrical supply network. Both the method and the device provide the use of an electronic microprocessor (7) receiving on the input side data relating to the current drawn by the lamp (7) and connected on the output side to a power switch (6) for high frequency switching of the alternating current supply to the lamp.

Abstract: A driver (10) for driving a LED (2) comprises: an ACDC converter (5) receiving AC mains voltage and generating DC output current; a chopper (6) receiving the DC output current and provide a regularly interrupted output current; a clock generator (20) generating a clock signal (SCL); a controller (50) receiving a user input signal (SU) indicating a dimming level, receiving the clock signal, receiving a mains signal (SM) representing the actual phase of the mains voltage, and generating a control signal (SC) for the chopper. The chopper is responsive to the controller's control signal as regards the switching moments of the output current. The controller calculates the required duty cycle on the basis of the user input signal. The controller synchronizes its control signal with the mains signal. The controller sets an arbitrary value for the phase difference of the output control signal with respect to the input mains signal.

Abstract: A system and method includes a controller that is configured to coordinate (i) a low impedance path for a dimmer current, (ii) attaching a dimmer to a power converter system at the leading edge of a phase-cut, rectified input voltage, (iii), control of switch mode power conversion, and (iv) an inactive state to, for example, reduce the dimmer current while allowing a dimmer to function normally from cycle to cycle of an alternating current (AC) supply voltage. In at least one embodiment, the dimmer functions normally when the dimmer conducts at a correct phase angle indicated by a dimmer input setting and avoids prematurely resetting while conducting. In at least one embodiment, by coordinating functions (i), (ii), (iii), and (iv) the controller controls a power converter system that is compatible with a triac-based dimmer.

Abstract: In embodiments of the present invention, a method and system is provided for designing improved intelligent, LED-based lighting systems. The LED based lighting systems may include fixtures with one or more of rotatable LED light bars, integrated sensors, onboard intelligence to receive signals from the LED light bars and control the LED light bars, and a mesh network connectivity to other fixtures.

Abstract: A tunable LED lamp for producing biologically-adjusted light having a housing, a power circuit, a driver circuit disposed within the housing and electrically coupled with the power circuit, and a plurality of LED dies electrically coupled to and driven by the driver circuit. The driver circuit may drive the plurality of LED dies to emit a phase-shift light having a first spectral power distribution, a general illuminating light having a second spectral power distribution, and a pre-sleep light having a third spectral power distribution. The phase-shift light may be configured to affect a first biological effect in an observer, and the pre-sleep light may be configured to affect a second biological effect in an observer. The LED lamp may be configured to fit in a troffer fixture. The LED lamp may also be a troffer fixture.

Abstract: An electronic device for a lighting system, comprising a TRIAC dimmer configured to receive a mains supply voltage and provide a phase cut voltage to the electronic device and having a control loop configured to control a duty cycle of a switched voltage converter that receives the rectified input voltage and provides drive current to a light emitting semiconductor device. The control loop has an error amplifier that is coupled to receive a sense voltage that is indicative of a current through the light emitting semiconductor device, the error amplifier is configured to provide a feedback signal to a pulse width modulation logic configured to control the duty cycle of the switched voltage converter to provide a constant drive current to the light emitting semiconductor device in response to the sense voltage, the error amplifier being coupled to receive a reference voltage that is a function of the input voltage.

Abstract: A lighting apparatus includes: a lighting circuit; a dimming signal circuit; and a feedforward control circuit. The lighting circuit receives an output which is rectified and smoothed commercial power, and supplies power to a light source Lamp. The dimming signal circuit sends a timing signal to the lighting circuit, wherein the timing signal is a signal for switching an output of the lighting circuit periodically to an ON state and either of an OFF state and a dimmed state. The feedforward control circuit detects either of an input voltage of the lighting circuit and an input voltage of the smoothing circuit, and sends a control signal to the dimming signal circuit, wherein the control signal is a signal for correcting a lighting time so that a light output of the light source can become a desired value.

Abstract: A lighting system includes a plurality of organic light emitting diode (OLED) devices. By selecting the plurality of OLED devices, or by selectively controlling the plurality of OLED devices, the color characteristics of the lighting system can be tuned. The lifetime of the lighting system can be improved.

Abstract: A dimmable LED driver circuit comprises a resonant DC-DC converter coupled to an output circuit. The converter comprises a half bridge or full bridge switching circuit coupled to a resonant circuit. An output of the resonant circuit is rectified and fed to the output circuit. The output circuit may comprise at least one LED series or shunt switch for switching an LED unit on and off. A control circuit controls the switches of the switching circuit at a variable switching frequency. The control circuit is also configured for controlling the switching circuit for amplitude modulating the converter and for pulse-width modulating the converter at a first pulse-width modulation frequency lower than the switching frequency. The control circuit is may further be configured for controlling the switching of the LED switch at a second pulse-width modulation frequency lower than the switching frequency.

Abstract: A lighting device has a power-factor correction circuit 6, a step-down chopper circuit 8, a full-bridge circuit 10, control ICs for these circuits and a driving-voltage supply circuit 14. The supply circuit 14 supplies a driving voltage to the control ICs. The control IC outputs the on/off driving voltage to a switching element of the corresponding circuit 6 to 10. The lighting device also has a detector 16 and judgment equipment 18. The detector 16 detects the driving voltage supplied from the supply circuit 14. The judgment equipment 18 instructs the control ICs to start outputting the on/off driving voltages in the order from the control IC close to the power source 2 to the control IC close to the discharge lamp 4 when the driving voltage detected by the detector 16 reaches a predetermined value during the time when the driving voltage supplied from the supply circuit 14 rises.

Abstract: A modularized LED lamp is disclosed. Embodiments of the present invention provide an LED lamp in which digital and/or analog communication takes place between the LED module and the power supply unit (PSU) of the lamp. A controller in the LED module sends signals to the PSU, allowing separation of the two parts so that each part can be manufactured independently as opposed to being manufactured as a calibrated, matched pair. The LED module, by way of its controller, provides information to the PSU that allows the power supply to adjust its drive current appropriately. The PSU controller can also respond to operating temperature variations of the LEDs in order to provide thermal shutdown, brightness compensation, and other control if needed. In some embodiments, a controller in the PSU also responds to an external dimming input.

Abstract: Exemplary lighting devices have sensors, intelligence in the form of programmed processors and communication capabilities. Such a device is configured to monitor one or more conditions external to a lighting device not directly related to operational performance of the respective lighting device. One or more such devices can work in a networked system, to support a variety of applications separate and in addition to the lighting related functions of the devices(s).

Abstract: The invention relates to a method for defining an operational parameter of an operational device for lighting means. According to the method,: a voltage supply of the operational device is preferably switched on/off manually, an on/off switching is evaluated by the operational device as to whether at least one first predetermined criterion is fulfilled, for example, time constants or repetition rates, in this is the case, a continuous, preferably cyclic change of the predetermined operational parameters is switched on by the operational device, the changed operational parameter is returned to the user directly or indirectly, optically and/or acoustically, and the actual value of the changed operational parameters is maintained at a moment in time for a subsequent operation of the lighting means to which an additional on/off switching of the voltage supply fulfills at least one second criterion.

Abstract: Enhanced active preload circuits for an LED driver implementing phase-angle dimming are disclosed. The enhanced active preload circuits may be used with any type of phase-angle control dimmer that either controls the leading edge or trailing edge of the line voltage cycle. In one example, the enhanced active preload circuitry may be used with an isolated or non-isolated LED driver converter having a Triac leading edge phase-angle control dimmer by directly sensing (e.g., by sensing the dimming level using an output/load voltage signal or output/load current signal) or indirectly sensing (e.g., by sensing a signal of output or bias winding) the Triac conduction angle. The enhanced active preload circuitry may advantageously improve performance of the LED driver by extending the dimming ratio at deep dimming and by adjusting the preload sinking current in response to a preload control signal.

Abstract: An embodiment of the present invention is directed to a method and circuit to control light emitting diode (LED) output. The method includes receiving a line voltage signal which powers a lighting circuit comprising an LED and determining an adjustment of a threshold based on a variation of the line voltage signal and/or a controller delay or other practical controller limitation or imperfection. The method further includes dynamically adjusting a threshold or other reference of a controller which controls a switch of said lighting circuit for compensating for line variations to maintain a substantially uniform LED current.

Abstract: In order to keep the advantage of PWM dimming control scheme and make the LED driver high reliability and the LED lamp long lifetime, it is required that the frequency of PWM dimming control scheme is related with or the same as the output frequency of existed dimmers; and the output PWM dimming pulse is covered by the output pulse from dimmers further. The present invention discloses a novel “LED dimming control” scheme to make that the frequency of PWM dimming control scheme is related with or the same as the output frequency of dimmers; and the output PWM dimming pulse is covered by the output pulse from the dimmers further. In this way, it can guarantee that as PWM dimming pulse comes, the output from the dimmer can offer enough power to the LED driver and the LED driver can output the required LED driving current without flicker.

Abstract: In a power supply device according to one embodiment, a reference signal (Vref1), which changes from a value corresponding to a maximum current in a full lighting state to that corresponding to a minimum current in case of a deepest dimming depth, and a reference signal (Vref2), which changes from a value corresponding to a load voltage at the time of a maximum current in a full lighting state to that corresponding to a minimum current in case of the deepest dimming depth, are prepared in accordance with dimming depths of a dimming signal. In a shallow dimming depth region close to a full lighting state, the reference signal (Vref1) is selected to apply constant-current control to light-emitting diodes in a current control mode. In a deep dimming depth region, the reference signal (Vref2) is selected to apply constant-voltage control to the diodes in a voltage control mode.

Abstract: The embodiments disclosed herein describe a method of a power controller for monitoring for unsafe operating conditions of a drive transistor in a switching power converter of a LED lamp system by predicting the power dissipation of the drive transistor based on knowledge of the current through the drive transistor and a continuous observation of the voltage across the drive transistor. When the drive transistor approaches unsafe operating conditions, the power controller turns off the drive transistor.

Abstract: A discharge lamp ballast apparatus includes an F/F 10 for maintaining the on or off operation of a high-side switching device Q1 of an inverter in synchronization with a rising edge and falling edge of a main signal, and a return unit 9 for generating a signal for returning, even if the output Q of the F/F is inverted owing an unforeseen situation, the output to the polarity to be output normally; and returns the output of the F/F 10 to the first polarity to be output normally using the return signal.

Abstract: To power and control multiple different electronic circuit nodes, this document introduces a single-wire multiple-circuit power and control system. Specifically, individually controlled circuit node units are arranged in a series configuration that is driven by a power and control unit located at the head of the series. Each of the individually controlled circuit node units may comprise more than one output circuit that is also individually controllable. The head-end power and control unit provides both electrical power and control signals down a single wire to drive all of the individual circuit node units in the series in a manner that allows each individual circuit node unit to be controlled individually or in assigned groups.

Abstract: A DC power source unit 37 is provided which boosts source voltage from a power source portion 36. A lighting circuit 38 is provided which supplies DC voltage to loads, the DC voltage being obtained by stepping down output current of the DC power source circuit 37. A control circuit 39 is provided which controls the lighting circuit 38 in accordance with at least either voltage or current of LEDs 25 and controls the DC power source unit 37 so that a ratio of output voltage to voltage of the LEDs 25 becomes a preset fixed ratio.

Abstract: An LED lighting device may include a first constant current source, a switched mode power supply, a plurality of LEDs between the switched mode power supply and the first constant current source, and powered by the switched mode power supply, and a voltage divider between the switched mode power supply and the plurality of LEDs. In various embodiments, the voltage divider may include a plurality of switches. Each switch may be configured to transition between open and closed based on a lighting state of an LED of the plurality of LEDs to vary a divided feedback voltage provided to the switched mode power supply. In various embodiments, the switched mode power supply may be configured to supply different output voltages based on the divided feedback voltage.

Abstract: A lighting system includes one or more methods and systems to control the color spectrum of a lamp in response to both temperature and dim levels. In at least one embodiment, the lighting system includes a controller to control a correlated color temperature (CCT) and intensity of the lamp by independently adjusting currents to electronic light sources based on a dim level of the lighting system and temperature of the lighting system. The controller controls a first current to a first set of LEDs and a second current to a second set of LEDs. The control of the first current by the controller is jointly dependent on a dim level and temperature in the lighting system. In at least one embodiment, the control of the second current is dependent on the dim level or the dim level and temperature.

Abstract: An adaptive sliding-frequency triggering ignition method for electronic ballast of high pressure gas discharge lamp includes the steps of: measuring an accurate value of free oscillation frequency of the ballast load loop by using a single-chip before sliding-frequency triggering ignition, implementing safe and reliable sliding-frequency triggering ignition after calculating the initial frequency and ending frequency of sliding-frequency triggering ignition according to the accurate value. The method can safely and reliably finish sliding-frequency triggering ignition course, thus improving the parameters such as the quality, life of the high pressure gas discharge lamp electronic ballast.

Abstract: An integrated circuit contains a current sink that is used to control a channel of varying forward voltage, with a goal of maintaining a minimally sufficient voltage across the current sink. A target voltage for the current sink return is determined, and a switched inductor is used to maintain said voltage. Various target determination schemes are possible, and various enhancements improve startup time, efficiency, and effectiveness.

Abstract: The status of a device is controlled by detecting (403) the presence of a user; changing the status of a device to a first state (405) if the presence of a user is detected within a first, predetermined zone; changing the status of the device to the second state (407) if the presence of a user is detected outside a second, predetermined zone, the first, predetermined zone being smaller than and being wholly contained within the second, predetermined zone; and maintaining (407) the current state of the device if the presence of a user is detected outside of the first, predetermined zone and within the second predetermined zone.

Abstract: A light emitting diode module includes a circuit board, a light-emitting-diode (LED) unit, a light-adjusting unit and a conductive trace. The LED unit is directly mounted on the circuit board. The light-adjusting unit is directly mounted on the circuit board at a position distinct from a mounting portion of the LED unit on the circuit board, and is operable to adjust electric current flowing through the LED unit. The conductive trace is disposed on the circuit board for electrically connecting the LED unit to the light-adjusting unit.

Abstract: A multiple location load control system comprises a main device and remote devices, which do not require neutral connections, but allow for visual and audible feedback at the main device and the remote devices. The main device and the remote devices are adapted to be coupled in series electrical connection between an AC power source and an electrical load, and to be further coupled together via an accessory wiring. The remote devices can be wired on the line side and the load side of the load control system, such that the main device is wired “in the middle” of the load control system. The main device is operable to enable a charging path to allow the remote devices to charge power supplies through the accessory wiring during a first time period of a half-cycle of the AC power source. The main device and the remote devices are operable to communicate with each other via the accessory wiring during a second time period of the half-cycle.

Abstract: One aspect of the present invention includes a light-emitting diode (LED) power supply system. The system includes an LED regulator configured to monitor at least one LED voltage associated with a respective at least one activated LED string and to generate an LED regulation voltage based on the at least one LED voltage relative to an LED power voltage that provides power to the at least one activated LED string. The system also includes a power converter configured to generate the LED power voltage and to regulate the LED power voltage based on the LED regulation voltage.

Abstract: The lighting apparatus in accordance with the present invention includes a dimming control unit configured to control, in accordance with a dimming ratio, a light source including a plurality of light emitting elements designed to emit light in response to DC power. The dimming control unit is configured to, when the dimming ratio falls within a first dimming range, vary supply power to the light source in accordance with the dimming ratio. The dimming control unit is configured to, when the dimming ratio falls within a second dimming range different from the first dimming range, vary, in accordance with the dimming ratio, a lighting number defined as the number of the light emitting elements to be lit.

Abstract: The invention relates to an integrated digital control circuit for an operating device for lamps, comprising: an output for the pulsing of switches of a half-bridge circuit having an adjustable frequency, wherein a load circuit comprising the lighting devices may be connected to the half-bridge circuit, an input, to which a signal may be selectively supplied, said signal reflecting the current through the half-bridge or the current through the lamp. The input is internally branched into two analysis branches, the outputs of which are combined using a logic member, the output of which is connected in turn to a controller for adjusting the frequency of the half-bridge actuating signal.

Abstract: A light source module includes a LED array, a switch and a control part. The LED array includes a plurality of LED rows and a bridge light emitting part connecting the LED rows with each other. Each of the LED rows has a first direction light emitting part and a second direction light emitting part which are alternately disposed with each other. The switch adjusts an intensity of a current applied to the LED array. The control part determines an output status of the LED array and provides a control signal to the switch.

Abstract: A light source control device controlling a light source that emits light corresponding to supplied current and a color wheel having a plurality of color segments that converts the light emitted from the light source, the light source control device includes: a current generation circuit, which supplies current to the light source, based on a control signal for controlling an amount of the light of the light source; and a control circuit unit, which stores a plurality of modulation factors corresponding to the plurality of color segments and has a plurality of calculation units corresponding to the plurality of color segments, and which operates the calculation unit corresponding to the segment in synchronization with each segment to thus calculate control information of the control signal.

Abstract: An LED apparatus includes an LED component and a current-limiting device. The LED component includes at least one LED having a corresponding current-limiting resistance value. The current-limiting device includes a plurality of PTC devices connected in series. The plurality of PTC devices are capable of effectively sensing the temperature of the LED and are electrically coupled to the LED component. The resistance value of the current-limiting device increases with the increment of sensed temperature. The current-limiting device has a resistance close to or equal to the current-limiting resistance value at a temperature at which the LED operates normally. When the temperature of the LED gradually increases to an abnormal temperature, current allowable to be flowed through the current-limiting device gradually decreases to be lower than LED operating current.

Abstract: An LED driver for operating a light source, in particular an LED, includes an energy storage unit, a driver circuit supplied by the energy storage unit during emergency lighting operation, for operating the light source, and a control unit that activates the driver circuit in such a way that the light source is operated with a constant power or constant current irrespective of the state of charge of the energy storage unit, where the control unit, for the purpose of regulating the power, determines indirectly the level of the current supplied to the light source.