Control system and method for dimming luminous output

Abstract

A control system and a method for dimming a light output are provided. The control system is configured to provide dimming control of the light output of one or more light emitting devices (124), comprising: a switch mode regulator (91) configured to provide an output power signal to the one or more light emitting devices (124) and to change the output power signal; one or more feedback sensors (304) configured to measure characteristic parameters of the output power signal, the characteristic parameters including at least one of the following: current, voltage, and power; and a controller configured to: when the characteristic parameter of the output power signal is above a threshold value (210), change the output power signal in a closed-loop control loop based on feedback from the one or more feedback sensors (304); and when the characteristic parameter of the output power signal is below the threshold value (210), change the output power signal in an open-loop control loop.

Description

Background Art

[0001] The present invention relates to a lighting control system for providing dimming control of a light output, and a method of dimming a light output. Technical Field

[0002] In particular, but not exclusively, the present invention relates to a method and control system for dimming or otherwise regulating the brightness of or powering a solid-state light source (SSL), such as a light-emitting diode (LED), an organic light-emitting diode (OLED), a solid-state diode laser (SSDL), and other solid-state light source loads based on organic or inorganic light-emitting mechanisms. The present invention also relates to improvements in the method and system to provide a unit for data transmission using such a light source.

[0003] The use of SSLs (e.g., LEDs, OLEDs, SSDLs) in lighting systems is well known because they offer significant advantages over traditional light sources, such as higher efficacy, increased reliability and lifetime due to their solid-state nature, and many other advantages known to those skilled in the art of LEDs, OLEDs, and SSDLs.

[0004] LED, OLED and SSDL based light emitting diodes are used in a variety of configurations for general and specialized lighting applications including, but not limited to, automotive lighting, task lighting, accent lighting, emergency lighting, hospitality lighting, restaurant lighting, hospital lighting, office lighting, retail store lighting, car lighting, street lighting, comfort lighting, effect lighting, marine lighting, display case lighting, TV and cinema and projection lighting, entertainment lighting, animal and food production lighting, medical lighting, outdoor lighting, backlighting for displays, irradiation of microorganisms in fluids using UV, curing and coagulation in industrial processes, corridor lighting, security lighting, etc.

[0005] LEDs, OLEDs, and SSDLs are current-controlled devices, where the intensity of light emitted from the device is related to the amount of current flowing through the device. Therefore, it is highly advantageous to carefully and reliably control the amount of current flowing through the LED, OLED, or SSDL device to achieve the desired lighting effect from the lighting system and maximize the device's lifespan by ensuring that maximum current, voltage, or power specifications are not exceeded. Furthermore, it is well known that LEDs, OLEDs, and SSDLs can be switched or modulated quickly enough to enable their use as data transmitters in conjunction with their primary purpose of illumination.

[0006] LED, OLED, and SSDL power supply systems have been developed based on various circuit design topologies that provide the ability to vary the actual or time-averaged forward current through the light emitting device load within an acceptable range to provide dimming capability.

[0007] However, due to the increasing efficiency of solid-state light emitters, even a small amount of current flowing through the device generates a large number of excitation photons. This produces an undesirable lighting appearance with large steps between dimming levels (low dimming resolution) at low intensities and a significant minimum emission at the lowest dimming level.

[0008] Lighting systems based on LEDs, OLEDs, and / or SSDLs have been designed that can produce a variety of colors and intensities by using multiple light-emitting devices with discrete wavelengths / colors. Systems that include red, green, blue, amber, and white light emitters can produce nearly infinite color variations by varying the intensity, current, or power of each color emitter, either individually or in combination. The use of multiple discrete wavelengths in a lighting system can increase the data transmission rate from the light-emitting devices by increasing the system bandwidth using different photon energies that are multiplexed simultaneously.

[0009] Many advanced lighting systems require dimming capabilities, typically using an external control system to provide dimming level information to the lighting system. Most dimming methods employed use constant current reduction (CCR) (also known as DC dimming) or time-averaged pulse modulation methods such as pulse width modulation (PWM), pulse amplitude modulation (PAM), pulse frequency modulation (PFM), and many other methods.

[0010] Current dimming methods cannot easily achieve high-precision dimming over a wide current range in an efficient manner. Dimming systems often involve steep steps in intensity or color when the system is dimmed on and off, especially at low light levels.

[0011] EP2477459 discloses a hybrid power control system for providing dynamic power control to a lighting system, wherein a power source can provide either an AC or DC voltage range. One or more switch-mode power supplies include one or more linear and switch-mode regulator circuits that are combined to dynamically control the current, voltage, and power delivered to the lighting system. The switch-mode regulators operate when the output current is within a first range and are inoperative when the output current is within a second range lower than the first range. Summary of the Invention

[0012] According to a first aspect of the present invention, a control system is provided, which is configured to provide dimming control of the light output of one or more light-emitting devices, and the control system includes: a switch-mode regulator, which is configured to provide an output power signal to the one or more light-emitting devices and change the output power signal; one or more feedback sensors, which are configured to measure characteristic parameters of the output power signal, the characteristic parameters including at least one of the following: current, voltage and power; and a controller, which is configured to: when the characteristic parameter of the output power signal is higher than a threshold, change the output power signal in a closed-loop control loop based on feedback from the one or more feedback sensors; and when the characteristic parameter of the output power signal is lower than the threshold, change the output power signal in an open-loop control loop.

[0013] The output power signal may be a pulse signal having multiple pulses.

[0014] When the characteristic parameter of the output power signal is lower than the threshold, the output power signal may alternate between one or more periods of being in an on state and one or more periods of being in an off state. The one or more periods of being in the on state may include at least one pulse of the pulse signal. The one or more periods of being in the off state may have a duration corresponding to the at least one pulse of the pulse signal.

[0015] Changing the output power signal in an open-loop control loop may include changing the ratio of the total time in the off-state to the total time in the on-state to change the total number of pulses in a fixed duration that includes one or more periods in the on-state and one or more periods in the off-state.

[0016] The duration of the one or more periods in the on-state may vary such that the output signal follows an irregular pattern between periods in the on-state and periods in the off-state.

[0017] When the characteristic parameter of the output power signal is below the threshold, the output power signal may change between a plurality of discrete levels, each level having a corresponding pattern of one or more periods in the on-state and one or more periods in the off-state.

[0018] The system may comprise a memory arranged to store a look-up table to store corresponding patterns for respective discrete levels of the output power signal.

[0019] The switch-mode regulator may operate in a continuous conduction mode during the one or more cycles in the on-state.

[0020] When the characteristic parameter of the output power signal is lower than the threshold, the duration of each pulse of the pulse signal may be constant.

[0021] The switch-mode regulator may include a switching device operated at a switching frequency.

[0022] When the characteristic parameter of the output power signal is higher than the threshold, the output power signal may be changed in a closed control loop, including changing the switching frequency of the switch mode regulator to change the pulse period.

[0023] When the switching frequency is above a minimum stable switching frequency, the switch-mode regulator may operate in a continuous conduction mode.

[0024] The threshold value of the characteristic parameter of the output power signal may be determined such that when the switching frequency is higher than the minimum stable switching frequency, the controller changes the output power signal in the closed control loop.

[0025] The switching device may be controlled by a pulse output from the controller.

[0026] The controller may be further configured to modulate the voltage or current of the output to provide data transmission via the light emitting output when the characteristic parameter of the output power signal is above the threshold.

[0027] The controller may be further configured to, upon determining that the output power signal is to increase from below the threshold to above the threshold: measure the characteristic parameter of the output power signal; compare the measured value with an expected value at the threshold, the expected value being based on control data for controlling the system in an open-loop control loop; and, when determining that the measured value is different from the expected value, control the switch-mode regulator to increase the output power signal from the measured value and modify the control data based on the measured value.

[0028] The feedback sensor may include a current sensing resistor disposed in series with an output channel to the one or more light emitting devices.

[0029] The current sense resistor may be floating relative to a ground of the output channel.

[0030] According to a second aspect of the present invention, a method for dimming a luminous output is provided, the method comprising: providing an output power signal for powering one or more light-emitting devices; measuring characteristic parameters of the output power signal, the characteristic parameters comprising at least one of the following: current, voltage, and power; when the characteristic parameters of the output power signal are higher than a threshold, changing the output power signal in a closed-loop control loop based on feedback from the one or more feedback sensors; and when the characteristic parameters of the output power signal are lower than a threshold, changing the output power signal in an open-loop control loop.

[0031] The output power signal may be a pulse signal, and each pulse of the pulse signal may have multiple pulses.

[0032] When the characteristic parameter of the output power signal is lower than the threshold, the output power signal may alternate between one or more periods of being in an on state and one or more periods of being in an off state. The one or more periods of being in the on state may include at least one pulse of the pulse signal. The one or more periods of being in the off state may have a duration corresponding to the at least one pulse of the pulse signal.

[0033] The output power signal may be provided by a switch mode regulator.

[0034] The method may include operating the switch-mode regulator in continuous conduction mode during the one or more periods in the on-state when the characteristic parameter of the output power signal is below the threshold and when varying the output power in the closed-loop control loop.

[0035] The switch-mode regulator may include a switching device capable of operating in a continuous conduction mode when the switching frequency is above a minimum stable switching frequency. The threshold value of the characteristic parameter of the output power signal may be determined such that the output power signal is changed in a closed control loop when the switching frequency is above the minimum stable switching frequency.

[0036] According to a third aspect of the present invention, there is provided a computer program which, when read by a computer, causes the method according to the first aspect to be executed.

[0037] According to another aspect of the present invention, a digitally controlled power supply capable of controlling power to a solid-state lighting system is provided, the digitally controlled power supply comprising one or more of the following: a power supply capable of converting an input power source into an output power source appropriately configured for a digitally controlled switch-mode controller; one or more digital switch-mode controllers capable of independently modulating power to the solid-state lighting modules over a wide dynamic range. The one or more digital switch-mode controllers may comprise one or more of the following: a microprocessor comprising one or more high-resolution PWM outputs with a resolution of less than 1 ns and one or more high-resolution analog or digital conversion units; one or more feedback devices or sensors; a multi-stage power, voltage, or current modulation controller comprising: at least one closed-loop stage using a PID controller capable of operating at one or more user-required set points, wherein the PID controller operates the switch-mode controller in both continuous conduction mode and discontinuous conduction mode for precise power control and / or provides precise current and / or voltage regulation to enable Li-Fi communication through the solid-state lighting modules; and at least one open-loop stage providing precise power modulation to extend the low-power dimming resolution of the digital switch-mode controller.

[0038] A solid-state lighting module may include one or more solid-state light-emitting devices for lighting and / or wireless communication, wherein each light-emitting device is capable of emitting coherent light and / or incoherent light. The coherent light source may be a laser, etc., and communication may be achieved by modulating the output.

[0039] A single or multiple light-emitting packages may include one or more light-emitting elements capable of radiating a single color or multiple colors including white, and optionally having a modulation bandwidth greater than a few kilohertz at -3dB. The light emitted by the light-emitting element may also include infrared or ultraviolet light, as well as other non-visible wavelengths.

[0040] The power supply may include control and filtering units to allow the input power source to act as a unit that sends or receives information over a network for controlling and reporting the status of the solid state lighting system.

[0041] The microprocessor may include one or more high-resolution PWM outputs with a time resolution of less than 1 ns, and / or one or more high-resolution analog or digital conversion units for converting feedback sensors, and / or units for securely transmitting control and status information over one or more networks.

[0042] The system may also include one or more of the following: acoustic, sound or vibration sensors; chemical sensors; electrical, current, potential, magnetic or wireless sensors; flow or flow rate sensors; ionizing radiation or subatomic particle sensors; navigation sensors; human-centric user-operated controllers; position, angle, displacement, distance, velocity and acceleration sensors; light, imaging and photon sensors; pressure sensors; force, density and level sensors; thermal, heat and temperature sensors; proximity and presence sensors; security sensors, such as fingerprint, iris, facial sensors; frequency sensors; other types of sensors; light sensors that detect light intensity; light sensors that detect color or visible light spectrum; camera sensors; temperature sensors; smoke sensors; gas detection sensors; force sensors.

[0043] The fundamental switching frequency of the system may be between 20 KHz and 1 GHz, or between 20 KHz and 1 MHz.

[0044] The power control system may include: at least one AC-DC switch mode power supply; one or more output driver modules including a high modulation bandwidth voltage-controlled current source or voltage clamp to modulate current or power suitable for data transmission through the connected light-emitting device; a unit for ensuring that the high modulation bandwidth data output is rejected or attenuated by the switch mode power supply to ensure that a stable current or power output is maintained; and a unit for providing internal and external control commands from a high bandwidth data control network to a controller or to the high bandwidth data control network.

[0045] The power conversion module can operate stably over a wide range of light emitting device currents, especially when the current is <1% of the maximum output module current.

[0046] The power control system may be configured to dynamically and independently configure the duty cycle and fundamental switching frequency of one or more switch-mode regulators.

[0047] The power control system may be configured to provide a linear or non-linear current or a continuous or discontinuous power curve to the light emitting device over quantized time intervals.

[0048] The voltage clamp or linear regulator device can inject a high-bandwidth current or voltage signal into the output module of the power converter to provide wireless photonic data transmission rates between 1 kbps and 100 Gbps through the connected light-emitting device.

[0049] The output driver module is capable of delivering currents as low as 1 nanoampere to one or more light-emitting devices in a controlled manner.

[0050] The optical output characteristics may be controlled by one or more of: an optical wireless signal sent or received from a remote transceiver; an RF or infrared readout wireless signal sent or received from a remote transceiver; a signal received via Ethernet.

[0051] The light emitting device may include at least one high power (>0.1 W) solid state light source.

[0052] The lighting system may include at least one high-bandwidth photosensor.

[0053] The output modules may deliver power to one or more light emitting devices using pulsed, non-pulsed, or simulated current profiles, alone or in combination.

[0054] The current profile through the light emitting device is selected from direct current, alternating current, pulse width modulation, pulse amplitude modulation, pulse frequency modulation, pulse density modulation, delta-sigma modulation, random signal density modulation (SSDM), and amplitude modulation.

[0055] A current source or current sink can be attached in parallel with the output. The current source or current sink can be controlled independently of the main output module.

[0056] Embodiments of the present invention include a unit for a power conversion module that includes control of the power factor and power quality of a lighting system. The power factor of the switch-mode power supply unit used in one embodiment of the lighting system can be ≥±0.70 or ≥±0.98, minimizing the amount of return current when power is delivered to the device load.

[0057] When used with an AC signal input to DC signal output topology, a power factor correction (PFC) circuit may be optionally employed in the present invention to precisely and transiently control the input current to match the input voltage waveform. The PFC circuit may include active and / or passive power factor correction to ensure that the lighting system has a power factor correction greater than 0.7.

[0058] The quality of power delivered to a lighting system can impact the overall lifetime characteristics of the system. For example, significant voltage spikes from the power supply's transmission lines can lead to partial or catastrophic failure of the light source (in the case of direct AC LEDs) or the power control system (in the case of DC LED systems). Therefore, in one embodiment of the present invention, a power line conditioner topology is utilized to improve the quality of power delivered to the lighting system.

[0059] Another embodiment of the present invention utilizes a light emitting device comprising at least one high-power (>0.1 watt) (O)LED or SSDL emitter package, which may include one or more light emitting elements. The (O)LED and / or SSDL emitter package may be of a type capable of being powered using either DC or AC voltage, depending on user or system requirements. The (O)LED and / or SSDL emitter packages may be arranged into an ordered or pseudo-ordered array of emitters to optimize the light exiting the lighting system.

[0060] Another embodiment of the present invention utilizes a light emitting device comprising at least one coherent and / or incoherent light source.

[0061] The controller may utilize a microprocessor, a programmable system on chip (PSoC), an FPGA (field programmable gate array), an ASIC (application-specific integrated circuit), or any other alternative integrated circuit device capable of computing information or data to calculate control parameters for the light-emitting device. Furthermore, the controller may optionally utilize and implement a feedback and feedforward control system to rapidly react to information provided by feedback from various condition sensors to modulate the characteristics of the light-emitting device. Such feedback sensors may include, but are not limited to, optical, color, light intensity, temperature, timer, occupancy, current, voltage, power, gas, magnetic, vibration, humidity, acceleration, velocity, frequency, and biological units that monitor or detect environmental conditions.

[0062] The lighting system may include a light emitting device including a single or multiple light emitting packages including one or more light emitting elements capable of radiating photons in a narrow wavelength band, or photons in a wide wavelength including white, or multiple photons within the visible or invisible electromagnetic spectrum.

[0063] The light emitting device may include one or more (O)LEDs and / or SSDL strings. In at least one embodiment, the light emitting device includes at least two (O)LEDs and / or SSDL strings, including an (O)LED and / or SSDL string emitting a first wavelength spectrum in the visible range and an (O)LED and / or SSDL string emitting a second wavelength spectrum in the non-visible range.

[0064] According to another aspect of the present invention, a power source is provided, wherein the power source can be any one or a combination of high or low voltage AC or DC energy sources. Depending on the electrical and electronic configuration of the controller system, the AC power source can range from a few volts of AC input to several thousand volts of alternating current, while the DC voltage input can range from a few volts of direct current to several thousand volts of DC.

[0065] The power source may be powered by a power supply or transformer, which is optionally attached directly or remotely to the lighting system. The power source may be an AC-DC power supply, a DC-DC power supply, an AC-AC power supply, or any other suitable power source.

[0066] According to yet another aspect of the present invention, a single-stage switch mode power supply is provided wherein the topology provides safety, component value and temperature variation compensation methods including one or more of the following features: current limiting, foldback, thermal shutdown, safe area protection, over current, short circuit or output power protection.

[0067] According to another aspect of the present invention, a controller is provided that converts an 8-bit user intensity control demand into a high-resolution, visually step-free control output. Variations of the high-resolution controller can allow solid-state light sources to simulate significantly slower output response rates similar to conventional light sources, reducing the appearance of steps when intensity changes are observed. This aspect of the invention can allow the output response to be varied over a defined time period.

[0068] The controller can optionally use an advanced microprocessor or integrated circuit device to measure the output driver module current, voltage and power consumption and control sensor values ​​in continuous conduction or discontinuous conduction mode. Using a microprocessor to control or regulate the output driver module enables complex control algorithms to be implemented in real time.

[0069] According to another aspect of the present invention, a unit for a switch-mode regulator is provided, wherein the control circuit further comprises: an integrated circuit, a microprocessor or any other similar semiconductor unit for generating analog and / or pulse switching control signals; a unit for receiving light-emitting device characteristics such as light intensity, power spectral density, and light-emitting device temperature; a unit for receiving sensor information; and a unit for transmitting and receiving information via a control network, a sensor network, a user interface and / or a communication system, which includes a light-emitting device for lighting and a high-bandwidth photosensor.

[0070] In this aspect of the invention, the time-averaged current through the light emitting device may be modulated by modulating a high frequency signal on the current through the light emitting device using an analog dimming phase or a pulse dimming phase.

[0071] In this aspect of the invention, a simple voltage divider or emitter follower topology connected to the regulator output module can be used to measure the switching regulator output voltage and, therefore, the forward voltage across the light emitting device connected to the power control system. The emitter follower can be designed using a simple transistor, such as the BC846C, with input and output bias resistors to appropriately set the gain of the emitter follower device, which can then be used to provide a voltage feedback value to the controller system.

[0072] According to another aspect of the present invention, the time-averaged current flowing through the light emitting device can be applied to a constant current or constant voltage type dimming control circuit topology.

[0073] According to another aspect of the invention, a unit for a controller is provided wherein light output characteristics of a lighting system can be controlled by one or more of: an optical wireless signal received from a remote transceiver, and an RF wireless signal received from a remote transceiver.

[0074] According to another aspect of the present invention, a unit for a controller is provided that is capable of measuring the output voltage of attached light emitting devices, wherein an output driver module delivers a controlled current to one or more light emitting devices so that damage to the light emitting devices can be limited.

[0075] According to another aspect of the present invention, a unit for a controller system is provided, wherein an output module can deliver power to one or more light-emitting devices using a pulsed, non-pulsed, or simulated current profile, either alone or in combination, wherein the current profile (or power) through the light-emitting device can be direct current, alternating current, pulse width modulation, pulse amplitude modulation, pulse frequency modulation, pulse density modulation, delta-sigma modulation, random signal density modulation (SSDM), amplitude modulation, or any other current control technique known to those skilled in the art.

[0076] Using various aspects of the present invention, current, and therefore power, can be provided to one or more additional light emitting devices having a greatly expanded dynamic dimming range, enabling the use of the same driver output stage to power a wide range of different light emitting devices including single die emitter packages, single array packages including multi-die emitters, or multiple packages.

[0077] Various aspects of the present invention enable the utilization of a specific dimming method (stage) at optimal efficiency based on power requirements, thereby maximizing efficiency across the entire dimming current (or power) range. Currently available switching regulators offer high efficiency (80%-99%) at maximum output power. However, as output power decreases to zero, switch-mode regulators are unable to accurately and repeatedly deliver output current to the light-emitting devices because the energy storage components within the switching devices become discontinuous. This results in unstable current or power flowing through the light-emitting devices, which can cause undesirable visual flickering of the light and unacceptably high minimum dimming illumination levels. By combining two or more dimming methods on an output module using a multi-stage-based dimming scheme, various aspects of the present invention enable the stability of the switching regulator to be continuously maintained even at very low output currents and / or powers.

[0078] The significant advantage of this multi-stage dimming technology is that at higher intensities, there is no pulsing because the solid-state lighting source operates in DC or analog mode. When lighting systems are typically above 70% of their maximum intensity, users work in environments, so multi-stage dimming provides a healthy non-pulsing method.

[0079] Depending on the configuration of the lighting system, currently available light emitting devices can range in power from a few hundred milliwatts to several hundred or several kilowatts. Each light emitting device within a lighting system requires a different forward voltage and forward current to operate correctly, and the present invention enables the output driver module to be easily configured using a microprocessor (or similar device), making it more suitable for driving a wider range of lighting systems.

[0080] Combining the unique characteristics of a switching regulator with an output driver module that includes a controller such as a microprocessor or similar device that enables the use of two or more dimming methods on one or more dimming stages enables very wide dynamic dimming (or power) ratios to be achieved, and by combining the 16-bit dimming resolution 2 16 Or 65535 dimming steps, can have 1 to 4294967296 (2 32 , using a 32-bit range). Although for many lighting applications 2 8 The dynamic range of 8 bits or 256 is good, but there is an increasing demand for small absolute current (power) steps for the first few control protocol intensity bits. Increased dimming (or power) resolution enables lighting systems to provide exponential dimming curves that are pleasing to the human eye and simulate the dimming effect seen by traditional light sources (such as incandescent or halogen bulbs), which have much slower response times compared to solid-state light sources. The present invention converts the 8-bit control protocol dimming requirements into higher bit resolution current / power outputs using appropriate time correlation methods and algorithms, enabling linear or nonlinear dimming of light emitting devices to very low lighting levels.

[0081] There are growing health concerns regarding the use of some artificial lighting solutions, particularly those that exhibit significant pulse characteristics such as high pulse modulation depth and low pulse frequency. Consumers are increasingly demanding that their artificial lighting solutions be human-centric by minimizing the amount of light source flicker. The present invention seeks to reduce the effects of light source flicker by limiting the pulse dimming method to low light source currents, which are typically only employed during the transition phase between the lighting system being switched on or off. Furthermore, the present invention utilizes output switching modules that provide high switching frequencies, for example, greater than 30,000 Hz, and utilizes a suitably high pulse frequency during the pulse dimming phase utilizing the pulse current / power method to ensure that light intensity flicker is minimized.

[0082] Another advantage of the present invention is that it provides a low-cost and simple unit that incorporates a high-frequency modulation scheme onto the output module of a controller, enabling information in the form of data to be optically transmitted through the light-emitting device at high speeds. The present invention can be easily implemented in single-stage and multi-stage, isolated or non-isolated switching topologies with minimal increase in component count or cost.

[0083] It will be appreciated that any feature discussed above in relation to a particular aspect of the invention may also be applicable to any other aspect of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0085] Figure 1 A schematic diagram illustrating a lighting system including a control system according to an embodiment of the present invention is illustrated;

[0086] Figure 2 schematically illustrates a dimming curve of a lighting system as the output changes from an off state to a fully on state and back to an off state;

[0087] Figure 3 An example of a pulse signal for providing a low dimming range is illustrated; and

[0088] Figure 4 Illustrated for Figure 1 A first example of a circuit of an output driver module of a system including a control system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0089] Figure 1 A lighting system 1 according to an embodiment of the present invention is schematically shown. Figure 1 The lighting system 1 is a high efficiency, low cost system with an ultra-wide dimming ratio, capable of having a load current dimming ratio of at least 15,000:1 using DC or constant current reduction.

[0090] The lighting system 1 includes a power source 10 connected by a power cable 21 to a connection module 20, which in turn is connected to an overvoltage protection module 30 and an input noise filtering module 40. The input noise filtering module 40 filters the power from the power source 10 before it is rectified and current limited by a rectification / limiting module 50. The rectification / limiting module 50 is connected to a power factor correction module 60 and then to an isolation and power module 70, which provides the necessary power to enable a dynamic control system 80 to manage the operation of the lighting system 1. The dynamic control system 80 is connected to one or more output driver modules 90. Figure 1In the example of FIG, a single output driver module 90 is shown. Each output driver module 90 is connected to an output noise filter 100, which ensures that a constant current with minimal noise is provided to an output connector 110. The output connector 110 provides power from the system 1 to the light emitting device fixture 120 via a cable 111.

[0091] The modules preceding the power module 70 form the high voltage input side of the circuit, while the subsequent modules form the output side.

[0092] All of the modules 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120 described above include components that are connected to each other via one or more dedicated printed circuit board (PCB) conductive traces or cables 11. Each of the modules 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120 will be explained in more detail below.

[0093] The power source 10 of the lighting system 1 can be a high-voltage (>100V) or low-voltage (<100V) AC power source. In one example, the power source can be bus power. The power source 10 is connected to a first terminal block 22 of the connection module 20 via an appropriately rated power cable 21. The first terminal block 22 can be panel-mounted or PCB-mounted. The first terminal block 22 can be a multi-pole type to enable multiple drivers to be easily connected together.

[0094] Depending on the configuration of the lighting system 1, other cables can be connected to the first terminal block 22 or the second terminal block 23 within the connection module 20. These cables can provide various sensor inputs or outputs and a communication bus 24 for transmitting commands between the lighting system 1 and the main controller 2. The communication bus 24 can be based on various hardware or protocol systems, such as I2C, SPI, UART, RS232, RS485, DMXCAN, USB, IEE1394, DMX, RDM, KNX, DALI, 802.11b / n, Bluetooth, Zigbee, Ethernet, which are readily available in digital communication systems.

[0095] The overvoltage protection module 30 may include one or more fuses 31 located in one or both of the power phase inputs to improve safety. The fuses 31 are included to prevent a short circuit to ground on the corresponding phase, or a short circuit between phases.

[0096] The overvoltage protection module 30 may also optionally include overvoltage protection at the input, consisting of transient protection. Transient spikes from the power source module 10 are known to damage sensitive components. In one example, the transient voltage suppression is a transient voltage suppressor 32, which effectively protects the rest of the lighting system 1 from transient voltage spikes.

[0097] The input noise filtering module 40 has two main functions. First, it prevents inherently generated noise from the switching regulator within the switched-mode power supply of the lighting system 1 from returning to the power source 10, particularly if the power source 10 is connected to the mains network, in accordance with international standards. The second function of the input filtering module 40 is to prevent noise from the power source 10 from entering the lighting system 1, particularly if the power source 10 is connected to the mains network.

[0098] In at least some embodiments, an input filtering module may include submodules 40a, 40b at the input and output of the rectifier / limiter module 50. For example, an input filter in the form of capacitors, resistors, and inductors may be provided to attenuate noise at the input of the rectifier module 50.

[0099] (O) LEDs are typically driven by direct current. The input side of the rectifier / limiter module 50 converts the AC power source 10 into rectified DC power. For example, a bridge rectifier or other suitable unit can be used to convert AC power to DC.

[0100] In some embodiments, the rectifier / limiter module 50 provides a soft start feature by limiting the inrush current during the startup phase. Limiting the current drawn by the lighting system 1 during the startup phase is useful for rating cables, fuses, and other components to safe values.

[0101] The power factor of a circuit is the ratio of the real power absorbed by the load (in this case, the light fixture 120) to the apparent power flowing in the circuit. Real power is the instantaneous product of voltage and current, while apparent power is the product of average current and voltage.

[0102] The power factor correction (PFC) module 60 may include a controller that provides a power factor close to unity and provides over-temperature, over-current, and over-power protection on the primary side of the switch mode power supply. For example, the controller may be a standard switch mode power supply integrated circuit controller.

[0103] The PFC module 60 reduces the inductive and capacitive loads on the power source module 10. The PFC module 60 also provides a boost in the output voltage, which enables driving multiple light-emitting devices. In one embodiment, the PFC module 60 is driven by the startup current of the output module from the rectifier / limiter module 50, and during normal operation, the PFC module 60 is driven by the operating current (the operating current drive takes over when the PFC module 60 circuit has started).

[0104] The isolation and power module 70 is connected to the output of the PFC module 60 and includes capacitors large enough to absorb and smooth the ripple current flowing from the PFC module 60 while providing a DC voltage to the dynamic control system 80 and the output driver module 90 .

[0105] One embodiment of the isolation and power module 70 will provide one or more regulated voltages to the control system 80 to optimize the efficiency of the switch mode power supply. Another embodiment may also provide a transformer. In either case, the isolation and power module 70 provides galvanic isolation of the output from the high voltage input.

[0106] The control module 80 is powered by the voltage source output of the isolation and power supply module 70. One embodiment of the control system module 80 includes a microprocessor 81 that executes a software control algorithm, a unit for communicating with the network master controller 2 via the bus 24, one or more user interfaces 82, and one or more sensor interfaces 83. In one example, the microprocessor can be an STM32F334 microprocessor from ST Microelectronics, although any similar integrated circuit can be used.

[0107] The user interface enables a user to determine the output control functions of the lighting system 1. One embodiment of the user interface 82 would include a menu keypad and an LCD display. Another embodiment could be a web-based user interface on a portable or stationary computing device.

[0108] Furthermore, a network communication interface 3 coupled to the main controller 2 enables data and external controller commands to be transferred between the outside world and the lighting system 1. Any suitable network connection may be used, including but not limited to the Internet, LAN, WiFi, 4G, 5G, LoRa, Bluetooth, etc.

[0109] The control module 80 can also provide modulation of the output intensity to provide data transmission. The photosensitive device can also allow data to be received. The transmission and reception of data will be discussed in more detail below.

[0110] The output driver module 90 includes a switch mode power supply (SMPS). The switch mode power supply, also known as a switching regulator 91, is configured to control the current provided by the output driver module 90. A sensor 92 is also provided. The sensor 92 is configured to detect various parameters of the output, which will be discussed in more detail below. A microcontroller 93 is also provided for controlling the operation of the switching regulator 91. In one example, the output driver stage 90 can be in the form of a buck converter topology (formed by an LC tank) to convert the pulsed output from the SMPS microprocessor into a continuous output signal for the light fixture 120.

[0111] The output driver module 90 is controlled by the control system 80, which in turn is under the control of the main controller 2 to ensure constant current and deliver a voltage that depends on the number of light emitting devices used in the light emitting device fixture 120. An embodiment of the digital control module 80 incorporates the output driver module 90 into the control module 80 to reduce cost and size while improving efficiency.

[0112] The output noise filter module 100 includes inductive and capacitive loads that remove ripple and noise spikes from the output of the output driver module 90 and prevent or limit switching noise from leaking to the output of the SMPS. Since the light-emitting device holder 120 requires a stable voltage so as not to be overloaded by high ripple voltage, the output noise filter 100 ensures that noise emissions conducted and radiated on, from, or to the output cable 111 connected to the light-emitting device holder 120 are attenuated.

[0113] The output noise filtering module 100 includes a filter implemented using a capacitor connected to the anode terminal of a light emitting diode and an inline inductor. The implementation of the filter will be readily understood by those skilled in the art.

[0114] The output cable and connection module 110 includes a terminal block 112 for an output cable 111. The output cable 111 provides power to the light emitting device fixture 120 and to one or more cables 113 for transmitting signals from sensors 125, 126, 127.

[0115] In one embodiment, the light emitting device fixture 120 includes: a wire or connector block 121 for receiving power from the output cable 111 of the lighting system; a heat sink 123 that is thermally connected to a metal core PCB including the light emitting device 124 or the (O)LED array substrate; a temperature sensor 125 for measuring the temperature of the light emitting device 124; a light intensity sensor 126 for measuring the intensity of ambient light and the output of the light emitting device 124; and a color sensor 127 for measuring the color of the light emitting device 124.

[0116] As mentioned above, Figure 1 The output side of the circuit shown is galvanically isolated from the input side, which is a high voltage. This isolation is achieved using a power transformer and an optoisolator.

[0117] Power is provided in the form of one or more input voltages, in a non-isolated or isolated manner, to one or more portions of the lighting system 1. For example, the controller 2 may require isolated power to ensure that the lighting system 1 is isolated from any communication cables plugged into the system 1 that may have excessive voltage applied due to improper wiring or that could be struck by lightning if wired outdoors.

[0118] The control module 80 is powered directly from the output of the isolation and power module 70 via a linear regulator, which in this case is defined as an LM29150. When the output voltage of the power stage is significantly greater than the output voltage of the microprocessor power supply, a DC / DC switching regulator can be used instead of the linear regulator to improve the power supply efficiency of the microprocessor 81.

[0119] Other power requirements within the lighting system 1 may require different operating voltages, for example a microcontroller unit (MCU) typically requires 3V and the driver output module 90 may require up to 65V.

[0120] In one example, the high voltage SMPS controller 93 is an ST Micro L6562D PFC and PWM power controller, however, any similar type of single or multi-stage control topology may be used in this embodiment.

[0121] Power is controlled to the isolation transformer using a switching MOSFET, which is in turn controlled by the gate driver pin of the main network controller 2. The transformer forms part of the isolated flyback SMPS design in the isolation and power module 70. Feedback is provided from the isolated secondary side of the driver module 90 to control the SMPS power using an opto-isolator; however, alternative single-stage or multi-stage control methods that do not require opto-isolators can be used. For example, the LinkSwitch-PH series from Power Intergrations Inc., USA, provides a highly integrated monolithic switching device that can implement a single-stage topology without the use of opto-isolators and secondary-side feedback components.

[0122] Figure 2 A graph is provided depicting an illustrative dimming curve 200 often used in solid-state lighting applications, where a solid-state lamp fixture is required to gradually turn on to a maximum allowed intensity (or output current) and then gradually dim to an off state. Figure 1 The system discussed herein provides a time-averaged output current from a single driver module 90 , but it will be appreciated that the time-averaged current is proportional to the intensity of the light output from the LED 124 .

[0123] like Figure 2 As illustrated, four different dimming stages 202, 204, 206, 208 may be used to implement dimming curve 1 in a seamless manner while maximizing the use of analog dimming at higher light intensities to promote healthy (non-pulsing) lighting.

[0124] The first dimming phase 202 begins at TO. In the first dimming phase 202, the output current increases from an initial "off" level I0 to a threshold intensity level I1 210 at time T1. This is referred to as burst dimming phase 1.

[0125] In the second dimming phase 204, from time T1 to time T2, the output increases from I1 to a maximum level I2 212. The second phase 204 is referred to as analog dimming phase 2.

[0126] In the third dimming stage 206, from time T2 to time T3, the output decreases from I2 to I1. The third stage 206 is referred to as analog dimming stage 3.

[0127] In the fourth dimming stage 208, from time T3 to time T4, the output decreases from I1 to I0. This is referred to as burst dimming stage 2.

[0128] from Figure 2 As can be seen from the above discussion, the dimming stages 202, 204, 206, 208 are pulse dimming 202, 208 or analog dimming 204, 206. Figure 2 , when the output is above the threshold level 210, dimming is analog, and when the output is below the threshold 210, dimming is pulsed. Therefore, the output over the entire range of I0 to I2 can be considered to consist of two different dimming stages, namely pulse dimming and analog dimming. When the desired output intensity is below the threshold 210, pulse dimming is used, and when the desired output intensity is above the threshold, analog dimming is used.

[0129] It is important to note that the output current is shown as time-averaged so that the actual output current (and thus lamp fixture intensity) is comparable regardless of the phase and the type of dimming used in each phase.

[0130] During the analog dimming phase, the current from the driver module 90 is a constant current between I1 and I2, which depends on the desired output intensity. By using DC dimming to provide the change in output intensity during the analog dimming phase, the output module 90 always operates in continuous conduction mode.

[0131] During the analog dimming phase, sensor 92 detects the current at the output. Microcontroller 91 uses the sensed current in a PID feedback control loop to modify the current output from SMPS 91 to the desired level. Therefore, the analog dimming phase can be considered a closed-loop control phase.

[0132] Sensors can also detect voltage and other variables of power and light output to provide further control over the analog dimming stage.

[0133] During the analog dimming phase, the SMPS 91 in the buck converter in the output driver stage 90 operates in continuous conduction mode, where the current through the converter's inductor never reaches zero. The analog dimming phase reduces light output by reducing various parameters of the pulse signal from the SMPS, including its switching frequency. At sufficiently low dimming levels, the buck converter will transition to discontinuous operation, which is inherently unstable. However, when this transition to discontinuous operation occurs, the system 1 switches to the burst dimming phase.

[0134] During the burst dimming phase, the SMPS output switches between periods of continuous operation (i.e., periods in the on-state) and periods in the off-state. The on-state periods consist of one or more pulses, while the off-state periods have no output at all. The SMPS switching frequency is controlled so that during the on-state, the buck converter operates in continuous mode.

[0135] The burst dimming stage is an open loop control stage because it does not utilize feedback from the current sensor. Instead, the microcontroller 91 controls the output driver module 90 and the SMPS to provide the desired average current level based on known factors of the output power signal.

[0136] Figure 3 The example for providing the first intensity level I in the burst dimming stage is shown. x FIG2 shows an example of a first pulse signal 302. It includes multiple periods 306 a to 306 d when the SMPS 91 is in the on state, separated by periods in the off state. Each on-state period 306 includes multiple pulses, causing the buck converter to operate in continuous conduction mode. The duration of the off state corresponds to at least one pulse.

[0137] Figure 3 Also illustrated are three examples of signals 304a-304c that may provide a second intensity level 1 x / 2 , the second intensity level is half of the first intensity level.

[0138] In the first example 304a, the duration of each on-cycle is halved. In the second example 304b, the duration of the on-cycle is the same as in the first example 302, but two on-cycles are omitted. In the third example 304c, the pulse intensity in each on-cycle is halved. In each case, the time-averaged current over a fixed period is equal to the first intensity level 1. x half of the average current.

[0139] from Figure 3As can be seen, assuming the pulse frequency in each of signals 302, 304a to 304c is constant, halving the number of pulses halves the intensity. Thus, in one embodiment, microcontroller 91 can simply control the number of pulses emitted by the output driver module to control the output to various dimming levels, such as through a counter-based digital control system. No feedback from a current sensor is required.

[0140] exist Figure 3 In the signal shown, the pattern of on-periods is regular (ie, periods of fixed duration separated by off-periods of fixed duration). It will be appreciated that in other examples, the output may be a random pattern of on and off periods that may repeat periodically.

[0141] Furthermore, in other embodiments, various one or more parameters of the pulses may be varied, as long as continuous conduction operation is maintained during the on-period. For example, the switching frequency, pulse duration, and amplitude of each pulse may be varied.

[0142] In at least some embodiments, the microcontroller 91 can access a lookup table to determine the desired output signal for a particular desired current. The microcontroller 91 can determine the desired output level and retrieve the characteristics of the output signal required to achieve that level from the corresponding row of the lookup table. The lookup table can be stored in a memory of the microcontroller 93, the main controller 2, or can be accessed via the interface 3 or the bus 24.

[0143] The dimming resolution of the lighting system 1, as described above, is the incremental increase (or decrease) in output intensity between adjacent dimming levels. In other words, the dimming resolution is the smallest change in intensity level that the system 1 can provide. Low resolution corresponds to large steps in output between levels, while high resolution corresponds to small steps.

[0144] In a typical dimming system, the dimming resolution may be constant across the entire output intensity range. However, in the above-described system 1, the dimming resolution may vary between two dimming stages.

[0145] For example, during the analog dimming phase, the dimming resolution may be a first resolution, while during the burst dimming phase, the dimming resolution may be a second resolution. The second resolution may be lower than the first resolution, allowing dimming to change in smaller increments during the analog dimming phase. In other examples, the dimming resolution may be the same during both phases. In another example, the burst dimming phase may have a higher resolution than the analog dimming phase.

[0146] It should be understood that while the analog dimming phase may appear to have a continuously varying current, there is still a minimum resolution defined by the incremental changes possible in the hardware implementing the dimming.

[0147] During the pulse dimming stage, the resolution is limited by a number of factors, including the minimum stable change in the pulse output characteristics and the number of available rows in the lookup table.

[0148] In the output range of the burst dimming phase I0 to I1, the output current is divided into multiple evenly spaced levels defined by the resolution. The dimming can be N bits, where the range is divided into 2 N Step length.

[0149] The first limiting factor in dimming resolution during the burst dimming phase is the size of the lookup table. Each step of dimming requires a separate row in the lookup table.

[0150] Another limiting factor for resolution in the pulse dimming stage is the pulse characteristics of the output pulse signal. For example, for the pulses in the signal, there may be a minimum T that can be repeated regularly in a stable manner so that all pulses are provided to the output without being lost. on and / or minimum amplitude. The basic switching frequency of the pulse signal (f switch ) can also limit the resolution.

[0151] In one example, where dimming in the pulse dimming phase is achieved by varying the number of pulses per second, the number of pulses provided at the output level may be given by:

[0152]

[0153] in:

[0154] P is the number of pulses per second (split over one or more on-cycles) that determines the output.

[0155] n is the output intensity level, and

[0156] R is the number of different dimming steps within the pulse dimming range.

[0157] For any given single-stage switching regulator topology, there is a defined minimum output stability level within which continuous conduction mode can be maintained. This level is determined by the various component tolerances and minimum feedback errors associated with the switching regulator topology. Using only the analog dimming stage, if the desired output current drops below the minimum stability level, the switching regulator becomes unstable and the output current will fluctuate unpredictably, resulting in flicker visible to the human eye, which is highly undesirable. The threshold 210 used to switch between the burst dimming stage and the analog dimming stage is therefore determined based on the lower limit within which continuous conduction mode can be maintained. For example, the threshold can be selected to be just above this limit. Threshold 210 is selected so that the noise on the current or voltage sensor is at the minimum acceptable level that can accurately provide feedback for the closed-loop analog dimming stage. Therefore, when the sensor can no longer provide reliable feedback, burst dimming takes over.

[0158] In at least some embodiments, automatic correction can be applied when the output intensity increases from a level below threshold 210 to a level above threshold 210. When the output is at or just below threshold 210, but dimming has not yet switched to analog dimming control, feedback from the sensor is measured. When a command to increase the output is received, the measured current across the output is compared to threshold 210. Correction is then applied so that the analog dimming stage increases the output based on the measured current rather than the expected threshold. The new threshold is also stored for future use instead of the previous threshold.

[0159] In other words, autocorrection starts measuring feedback before control switches to the closed control loop. The measured feedback is then used in the first iteration of the closed control loop.

[0160] During the analog dimming phase, the output can be modulated to transmit data in the light. The data to be transmitted is received and encoded in the modulation of the output voltage. This can be sensed by a corresponding detector and decoded accordingly. The lighting system 1 may also include a detector (not shown) to enable the reception as well as transmission of data.

[0161] The current for output modulation can be provided by an independent current source or current sink, which can be controlled independently of the main output driver module 90. The switching regulator provides most of the power, while the current source or current sink provides the modulation. The current source or current sink can be connected in parallel to the output and can provide 0% to 5% of the output power.

[0162] The high-frequency output signal enables the LED load connected to the output driver module to change intensity in proportion to the change in the magnitude of the load current / power. This optical change can be easily picked up by a receiver connected to or integrated with a networked device to transmit information.

[0163] Figure 4 An example of a circuit 300a for an output driver module 90 of the lighting system described above is illustrated. In the example shown, the output driver module 90 is in the form of a buck converter topology.

[0164] LED fixture 120 is connected across outputs 302a and 302b. Sensor 304 is provided as a current sense resistor and measures the current flowing through LED fixture 120. Sensor 304 is provided on the high side of the system to allow multiple output driver modules to be connected to the same system and still independently measure the current through each LED fixture. A short-circuit sense resistor 306 is also provided in circuit 300, and when a specific voltage is reached across the sense resistor, circuit 300 automatically shuts down microprocessor signal GATE_2. Current sense monitor 310 provides current feedback to the microprocessor for controlling switching MOSFET 308. The ratio of the fixed value of short-circuit sense resistor 306 to resistor R210 allows hardware tripping to occur when the trip current through LED fixture 120 occurs in nanoseconds, reducing any potential damage to LED fixture 120 due to overcurrent.

[0165] The output driver module circuit 300 includes a switching MOSFET 308. The MOSFET controls the power and, therefore, the voltage and / or current on the output channels 302a, 302b. MOSFET 308 is, in turn, controlled by a microcontroller. During the pulse dimming phase, the microcontroller (not shown) controls the operation of MOSFET 308 via signal GATE_2 to open and close the path through MOSFET 308, thereby providing a pulsed output at the output channels 302a, 302b.

[0166] In the above example, the output range of the system 1 is provided by two different dimming stages, namely a burst dimming stage and an analog dimming stage. It should be understood that this is only an example. In addition to burst dimming and analog dimming, any number of additional dimming stages can be provided.

[0167] Figure 1 The illustrated system is given as an example only. It should be understood that the various functions discussed can be omitted or provided in any suitable manner without separate modules. The separate modules disclosed are for illustrative purposes only.

[0168] It should be understood that Figure 2 The curves are also provided as examples only, to illustrate certain embodiments of the present invention. A system's actual dimming curve may include various points where the output remains constant over time. The output never needs to increase to maximum, and can be switched on and off at any level, rather than starting at minimum and increasing and decreasing.

[0169] In the above examples, one or more electrical parameters of the system (e.g., current, voltage, or power) are measured to control the dimming cycle. It will be appreciated that other parameters may be detected and used in dimming control. For example, the system may also include sensors for detecting one or more of the following: ambient lighting level (in lux), a color sensor for detecting the color output from the LED fixture 120, and occupancy (e.g., a passive infrared detector or a microwave detector).

[0170] By detecting the ambient lighting level, the dimming output can be controlled so that the correct lighting is achieved (e.g., in high ambient lighting levels, the light output from the LEDs 124 can be reduced; in low ambient lighting levels, the light output from the LEDs 124 can be increased). By detecting color, the output from different LED fixtures can be varied to achieve a desired lighting effect. By detecting occupancy, the dimming can be controlled so that the lighting fixtures 124 are powered only when needed. For example, if occupancy is not detected within a threshold time (e.g., 30 seconds), the light output can be reduced.

[0171] As with dimming, these functions are now built directly into the LED driver rather than using an external controller, providing lower cost and localized / distributed control.

[0172] In a variation of the present invention, a time-averaged output current may be obtained for a constant-voltage-based output switch module.

Claims

1. A control system configured to provide dimming control of the light output of one or more light emitting devices, the control system comprising: a switch-mode regulator configured to provide an output power signal to the one or more light-emitting devices and to vary the output power signal; One or more feedback sensors configured to measure characteristic parameters of the output power signal, the characteristic parameters comprising at least one of the following: current, voltage, and power; as well as Controller, which is set up to: When the characteristic parameter of the output power signal is above a threshold, changing the output power signal in a closed-loop control loop based on feedback from the one or more feedback sensors; as well as When the characteristic parameter of the output power signal is lower than the threshold, changing the output power signal in an open-loop control loop, Wherein, when the characteristic parameter of the output power signal is lower than the threshold value, the output power signal is a pulse signal having multiple pulses and alternates between one or more periods in an on state and one or more periods in an off state, at least some of the one or more periods in the on state include multiple pulses of the pulse signal, and at least some of the one or more periods in the off state have a duration corresponding to the multiple pulses of the pulse signal.

2. The control system according to claim 1, wherein: At least some of the one or more periods in the on-state include a plurality of pulses of the pulse signal, and at least some of the plurality of periods in the off-state have a duration corresponding to the plurality of pulses of the pulse signal.

3. The control system according to claim 1 or 2, wherein: Changing the output power signal in an open-loop control loop includes changing a ratio of a total time in the off-state to a total time in the on-state to change a total number of pulses in a fixed duration that includes one or more periods in the on-state and one or more periods in the off-state.

4. The control system according to claim 1 or 2, wherein: The duration of the one or more periods in the on-state varies such that the output power signal follows an irregular pattern between periods in the on-state and periods in the off-state.

5. The control system according to claim 4, wherein: When the characteristic parameter of the output power signal is below the threshold, the output power signal is capable of changing between a plurality of discrete levels, each level having a corresponding pattern of one or more periods in the on-state and one or more periods in the off-state.

6. The control system according to claim 5, wherein: The system includes a memory configured to store a lookup table to store corresponding patterns for respective discrete levels of the output power signal.

7. The control system according to claim 1, wherein: The switch-mode regulator operates in a continuous conduction mode during the one or more cycles in the on-state.

8. The control system according to claim 1, wherein: When the characteristic parameter of the output power signal is lower than the threshold, the duration of each pulse of the pulse signal is constant.

9. The control system according to claim 1, wherein: The switch-mode regulator includes a switching device operated at a switching frequency.

10. The control system according to claim 9, wherein: When the characteristic parameter of the output power signal is above the threshold, changing the output power signal in a closed control loop includes changing a switching frequency of the switch-mode regulator to change the number of pulses per second.

11. The control system according to claim 9 or 10, wherein: The switch-mode regulator is capable of operating in a continuous conduction mode when the switching frequency is above a minimum stable switching frequency.

12. The control system according to claim 11, wherein: The threshold value of the characteristic parameter of the output power signal is determined so that the controller changes the output power signal in the closed-loop control loop when the switching frequency is higher than the minimum stable switching frequency.

13. The control system according to claim 9, wherein: The switching device is controlled by a pulse output from the controller.

14. The control system according to claim 1, wherein: The controller is further configured to modulate the voltage or current of the output power signal to provide data transmission via a light emitting output when the characteristic parameter of the output power signal is above the threshold.

15. The control system according to claim 1, wherein: The controller is further configured to, upon determining that the output power signal is to increase from below the threshold to above the threshold: measuring the characteristic parameter of the output power signal; comparing a measured value to an expected value at the threshold, the expected value being based on control data used to control the system in an open control loop; as well as When it is determined that the measured value is different from the expected value, the switch mode regulator is controlled to increase the output power signal from the measured value, and the control data is modified based on the measured value.

16. The control system according to claim 1, wherein: The feedback sensor includes a current sensing resistor disposed in series with an output channel to the one or more light emitting devices.

17. The control system according to claim 16, wherein: The current sense resistor is floating with respect to a ground of the output channel.

18. A method for dimming a light output, the method comprising the following steps: providing an output power signal for powering one or more light emitting devices; measuring characteristic parameters of the output power signal, wherein the characteristic parameters include at least one of the following: current, voltage, and power; When a characteristic parameter of the output power signal is above a threshold, changing the output power signal in a closed-loop control loop based on feedback from the one or more feedback sensors; as well as When the characteristic parameter of the output power signal is lower than a threshold value, the output power signal is changed in an open-loop control loop, wherein, when the characteristic parameter of the output power signal is lower than the threshold value, the output power signal is a pulse signal having multiple pulses and alternates between one or more periods in an on state and one or more periods in an off state, at least some of the one or more periods in the on state include multiple pulses of the pulse signal, and at least some of the one or more periods in the off state have a duration corresponding to the multiple pulses of the pulse signal.

19. The method according to claim 18, wherein At least some of the one or more periods in the on-state include a plurality of pulses of the pulse signal, and at least some of the plurality of periods in the off-state have a duration corresponding to the plurality of pulses of the pulse signal.

20. The method according to claim 19, wherein The output power signal is provided by a switch mode regulator.

21. The method according to any one of claims 18 to 20, wherein Changing the output power signal in an open-loop control loop includes changing a ratio of a total time in the off-state to a total time in the on-state to change a total number of pulses in a fixed duration that includes one or more periods in the on-state and one or more periods in the off-state.

22. The method according to any one of claims 18 to 20, wherein: The duration of the one or more periods in the on-state varies such that the output power signal follows an irregular pattern between periods in the on-state and periods in the off-state.

23. The method according to claim 22, wherein When the characteristic parameter of the output power signal is below the threshold, the output power signal is capable of changing between a plurality of discrete levels, each level having a corresponding pattern of one or more periods in the on-state and one or more periods in the off-state.

24. The method according to claim 23, comprising: The corresponding pattern for each discrete level of the output power signal is obtained from a lookup table.

25. The method according to claim 20, wherein The method comprises: The switch-mode regulator is operated in a continuous conduction mode during the one or more cycles in the on-state.

26. The method according to claim 18, wherein When the characteristic parameter of the output power signal is lower than the threshold, the duration of each pulse of the pulse signal is constant.

27. The method of claim 20, wherein: The switch-mode regulator includes a switching device operable at a switching frequency.

28. The method according to claim 27, wherein When the characteristic parameter of the output power signal is above the threshold, changing the output power signal in a closed control loop includes changing a switching frequency of the switch-mode regulator to change the number of pulses per second.

29. The method according to claim 27 or 28, wherein The switch-mode regulator is capable of operating in a continuous conduction mode when the switching frequency is above a minimum stable switching frequency.

30. The method according to claim 29, wherein The threshold value of the characteristic parameter of the output power signal is determined such that the output power signal is changed in a closed control loop when the switching frequency is higher than the minimum stable switching frequency.

31. The method of claim 27, wherein: The switching device is controlled by a pulse output from a controller.

32. The method of claim 18, comprising: When the characteristic parameter of the output power signal is higher than the threshold, the output voltage or current is modulated to transmit data through the lighting output.

33. The method of claim 20, wherein upon determining that the output power signal is to increase from below the threshold to above the threshold: measuring the characteristic parameter of the output power signal; comparing the measured value with an expected value at the threshold, the expected value being based on control data for controlling the output power signal in an open-loop control loop; as well as When it is determined that the measured value is different from the expected value, the switch mode regulator is controlled to increase the output power signal from the measured value, and the control data is modified based on the measured value.

34. The method of claim 18, wherein The feedback sensor includes a current sensing resistor disposed in series with an output channel to the one or more light emitting devices.

35. The method according to claim 34, wherein The current sense resistor is floating with respect to a ground of the output channel.

36. A computer-readable storage medium having stored thereon a computer program, which, when executed on a processor, causes the processor to perform the method according to any one of claims 18 to 35.

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