Configurable LED driver/dimmer for solid state lighting applications

Notice: More than one reissue application has been filed for the reissue of U.S. Pat. No. 10,187,946. The reissue applications are U.S. application Ser. No. 17/153,989 (a parent reissue application), and Ser. No. 18/396,107 (the present application, which is a continuation reissue of U.S. application Ser. No. 17/153,989).

This applicationis a continuation reissue of U.S. patent application Ser. No. 17/153,989, filed Jan. 21, 2021, which is itself an application for reissue of U.S. patent application Ser. No. 15/688,055, filed Aug. 28, 2017, now U.S. Pat. No. 10,187,946, whichisitselfa continuation of U.S. patent application Ser. No. 15/070,502, filed Mar. 15, 2016, now U.S. Pat. No. 9,775,207, which is itself a continuation of U.S. patent application Ser. No. 14/590,045, filed Jan. 6, 2015, now U.S. Pat. No. 9,320,093 which is itself a continuation of U.S. patent application Ser. No. 13/466,509, now U.S. Pat. No. 8,957,601, filed May 8, 2012, which is itself a continuation-in-part of U.S. patent application Ser. No. 13/059,336, now U.S. Pat. No. 8,525,446, filed Feb. 16, 2011, which is a national stage filing under 35 U.S.C. 371 of International Patent Application PCT/CA2009/001295, filed on Sep. 17, 2009, which claims the benefit of U.S. Provisional Patent Application No. 61/097,963, filed Sep. 18, 2008, all of which are incorporated herein by reference.

With the rapid increase in light emitting diode (LED) efficacies for high powered LEDs, the latest technologies have exceeded incandescent and halogen sources and are now starting to compete with fluorescent, mercury vapour, metal halide and sodium lighting. In addition to better energy usage, LEDs also have considerable advantages over traditional light sources such as long life, better durability and improved color generating abilities. The advancement of LED technology by various manufacturers has produced high power LEDs with various recommended drive currents such as 350 mA, 500 mA, 700 mA, 1000 mA, and 1400 mA or higher.

In recent years, controllable power sources for Solid State Lighting (SSL) applications have entered the market with integrated features. In addition, digital controllers within power sources have enabled the development of configurable options to provide a wider flexibility of solutions for Solid State Lighting applications. The ability to dim the light output of LEDs is also important to reduce energy consumption.

However, lighting companies are faced with considerable challenges in adopting SSL technology due to their unfamiliarity and lack of expertise in the driving and dimming requirements for LEDs.

Therefore, there is provided a novel LED Driver/dimmer for solid state lighting applications.

With the wide variety of communication interface options and LED drive currents available for numerous architectural and entertainment Solid State Lighting applications, the configurable LED Driver/dimmer of the current disclosure includes at least one of the following advantages: configurable output current options that maximize the available power in the “front end” PFC and isolated power conversion converter stage; multiple drive current options for the multiple LED drive current options for various LEDs; elimination of a cooling fan which can present issues with audible noise and flexibility in where the power source is located, relatively low standby power consumption during “black out” lighting conditions, where “black out” refers to no load operation on the output of the dimmer/driver; multiple communication interface options; the ability to map output current sources/channels to different DMX512A addresses and the ability to configure multiple groups of output current sources/channels such that each group is controlled by one 0-10 Vdc analog signal.

Some embodiments of the present disclosure are directed to a highly efficient enclosed, configurable power source, controllable by various external communication interfaces and a method for driving and dimming LEDs or OLEDs in lighting fixtures such as used for architectural or entertainment lighting applications. Such applications can include, but are not limited to, theater, convention centers, cruise ships, architectural building features, amusement parks, museums, and hospitality lighting in restaurants and bars.

In one aspect of the present disclosure, there is provided a configurable light emitting diode (LED) driver/dimmer for controlling a set of light fixture loads comprising: a power circuit; a primary digital controller for controlling the power circuit; a set of output current drivers, each of the set of output current drivers connected to one of the set of light fixture loads for controlling the associated light fixture load; a secondary digital controller for controlling the set of output current drivers; wherein the secondary controller transmits LED control information to control outputs of the set of output current drivers; and wherein the secondary digital controller provides digital feedback control information to the primary digital controller.

In another aspect of the present disclosure, there is provided a configurable power source that provides a plurality of output channels, such as 6, 8, 9, or 12, to color change or dim OLED or LED loads. In color changing applications, the number of available channels is a multiple of three or four to accommodate either red/green/blue LED loads or red/green/blue/amber or white LED loads. The number of output channels and available output power is increased or maximized based on the LED current requirements. The output channels are programmable by means of in circuit serial programming (ICSP) ports and calibrated by a secondary digital controller to the required output current and other parameters such as dimming frequency range.

In another embodiment, the dimming of multiple monochromatic color or white LED loads (output channels) utilizing a single 0-10 Vdc analog control signal, or the control of groups of LED loads (output channels) with an associated 0-10 Vdc analog control signal for each group is contemplated.

In another aspect of the present disclosure, the output channels are digitally controlled current sources configurable for various peak currents to power and control a variety of LEDs. The LED average current is encoded within the three variables of on-time, off-time, and period whereby no three variables are held constant. Depending on the output drive currents of the LED loads, the number of available output channels is maximized based on the maximum output power available from the power factor and isolated DC/DC converter stages.

In another aspect of the present disclosure, the configurable power source is housed in a rectangular enclosure with a monolithic aluminum extrusion and a U shaped aluminum chassis and metal end plates. Various electrical components are thermally coupled to the heatsink to increase or maximize heat transfer to the outside surface of the enclosure.

In another aspect of the present disclosure, the power source includes a digital controller to decrease power consumption of a relay coil as part of an inrush current limit circuit to reduce power consumption and improve efficiency.

In another aspect of the present disclosure, the power source utilizes an independent efficient auxiliary power source and one or more digital controllers to provide power to the communication interface. A digital controller disables various electrical circuits during black out lighting conditions to reduce no load power consumption and improve efficiency.

In general, the present disclosure is directed at a method and apparatus for providing a configurable LED Driver/dimmer. In the current description, the Driver/dimmer will be referred to as a dimmer, however, it will be understood that the configurable apparatus can function as either a driver, a dimmer or both. In the preferred embodiment, the dimmer is used for Solid State Lighting (SSL) applications.

Turning to, a perspective view of an LED dimmer is shown. The LED dimmerincludes a body portion, or housing, which includes a monolithic aluminum heatsinkand a U-shaped chassis. Cross-sectional views of the dimmerare provided in.

The dimmerfurther includes a front platewhich includes a plurality of portsalong with a set of conductor cables. The front plateis fastened to the body portionvia a set of fasteners, such as screws. In this embodiment, as conductor cables are used to provide output power to LED/OLED loads, the space requirement for the front plateis reduced with respect to other known connection means such as terminal blocks.

Turning to, a pair of cross-sectional views of the LED dimmer are provided.is a schematic view of one embodiment of an internal layout of the dimmer. The cross-sectional views forare taken along lines A-A and B-B ofrespectively.

As shown, the heatsinkincludes a receptacle portionfor receiving the ends of the chassis. In order to increase, or optimize, the heat dissipation capability of the configurable dimmerat full output power, the extruded aluminum heatsinkincludes finsto increase the surface area for heat dissipation. The heatsinkalso has a mounting platformfor receiving power components, or semiconductors, such as a bridge rectifier, MOSFETs, and/or diodes to efficiently transfer heat to the outside surface of the heatsink. These components will be discussed in more detail below with respect to. A power factor inductor and main isolation transformer pairare thermally coupled to the chassisby a thermally conductive, electrically isolated materialto further improve heat dissipation of these components. A circuit boardis also mounted to the heatsink.

Turning to, a block diagram of another embodiment of the LED dimmer is shown. The LED dimmerincludes an inrush current limit, or inrush current limit circuit, which receives power from an AC power source or supply, located external to the dimmer. The inrush circuitis connected to a Power Factor Correction (PFC) Boostwhich, in turn, is connected to a DC/DC Converter, or power conversion stage. The converteris connected to an Output Voltage buswhich is connected to a power limiter. The inrush circuit, the PFC boost, the DC/DC converter, the Output Voltage busand the power limitcan be seen as a power circuit. Although only one power limitis shown, it will be understood that there could be multiple power limits. The power limiteris connected to a set of output current drivers, whereby each of the output current drivershas an associated in-circuit serial programming (ICSP) port. The output of the output current driversis connected to individual Organic Light-Emitting Diodes (OLED)/Light-Emitting Diodes (LED) loads, further referred to as LED loads.

Along with the above-identified components and circuitry, the dimmerfurther includes a primary digital controllerwhich is connected to an auxiliary power sourceand an ICSP Port. The primary digital controlleris further connected, via an isolated communication busto a secondary digital controller, which receives power from the auxiliary power source. An ICSP portis also connected to the secondary digital controller.

The auxiliary power sourceis also used to power an interface componentwhich includes an optional address selectorand a communication interface. The communication interfacereceives inputs from an external transmitterand communicates via an isolated serial communication buswith the secondary digital controller. A set of isolation barriersandare located within the dimmer, each barrier separating various components of the dimmerfrom each other.

As will be understood, not all of the components or connections of the LED dimmerrequired for operation are shown as they will be understood by one skilled in the art. For instance, the dimmercan also include an EMI filter and a bridge rectifier. With respect to connections, it will be understood that the primary digital controllercan also be connected to the PFC boost, the inrush current limitand the DC/DC converterwhile the secondary digital controllercan be connected to the output voltage bus, the power limitand the output current drivers.

In operation, the PFC Boostand DC/DC Converterare controlled by the primary side digital controllerwhile the secondary digital controllermonitors the output voltage busand provides digital feedback control information via isolated communication busto regulate the output voltage bus. Secondary digital controlleralso translates dimming and/or color mixing information from the external transmitterinto LED control information for the output current drivers. The primaryand secondarydigital controllers and output current drivershave an associated programming port for further configuring the LED dimmer.

Turning to, a prior art inrush current limit is shown. In order to limit inrush current limit during initial start up of the power source, one approach is to utilize a negative temperature coefficient thermistor (NTC) in parallel with a relay contact. During initial turn on of the power source, the NTC thermistor limits the inrush current. When the PFC boost stage bulk capacitor is charged, and before the PFC stage is enabled by the primary controller, the primary controller closes the relay contact to bypass the NTC thermistor. This is accomplished by applying a DC voltage via a switch across the coil in the relay.

A limitation of this approach is the power consumption of the relay coil when a continuous DC voltage is applied. This power consumption becomes significant in terms of Energy Star requirements during no load or standby operation such as when a “black out” or minimum light intensity state is received by the communication interface.

Turning to, an embodiment of an improved inrush current limitis shown. An EMI filteris connected between the power supply and the current limitand is connected directly to the PFC boostand via the current limit. The current limitincludes a thermistor, a relay or relay contactand a switch. The relay contactis connected in parallel with the thermistor. A typical relay coil requires greater energy to close the contacts than is required with the currently described limiterto maintain the contacts in a closed position since less holding force is required. After the relay contacts have been closed by applying a voltage of 12 Vdc, modulation of the relay coil voltage can be initiated by the primary controllerto effectively reduce the average voltage across the coil to approximately 5 volts versus a DC voltage of 12V, reducing power consumption. It should be noted that the pulse duty cycle and frequency can also be changed to improve or optimize performance.

In one embodiment, the primary controllerpulses the DC voltage across the relay coil via the switchto reduce power consumption.

In one embodiment, for the PFC boost, as shown in, the PFC Boostutilizes a boost topology with an input AC voltage mains range of 103 Vac to 300 Vac from the AC supply. Energy stored in an inductor within the PFC boostis transferred and stored in the bulk capacitor on a cycle by cycle switching basis at a loosely regulated 430V DC over the input range. The energy is controlled in a manner that forces AC input current to be sinusoidal and in phase with the AC line voltage. By drawing current in phase with the input mains voltage, the amount of harmonic currents of the fundamental AC mains frequency being introduced into the power line is reduced.

For the DC/DC convertorand the output voltage bus, the preferred embodiment for the DC/DC converteris derived from the isolated buck converter topology and comprises a galvanically isolated full bridge converter employing a primary side phase modulation technique with a secondary side current doubler rectifier circuit.

The full bridge converter parasitic circuit elements in conjunction with primary magnetization current and reflected inductor ripple current cause resonant edge switching transitions on the MOSFET switch thus forcing zero voltage across the MOSFET switching device before turn on. The result is higher efficiency due to the elimination of Coss (drain to source MOSFET Capacitance) switching losses, reduction of gate charge across the Miller capacitance and minimized power loss during switching transitions when voltage and current are changing simultaneously.

Since the output of the DC/DC converter is a tightly regulated DC bus, the set of power limit circuitsare coupled to either one or more current driversto limit the power output of each of the output current drivers.The power limit circuitseach include a current sensor that is monitored by the secondary controller. In the event of a single component failure within the output current driver module, the power limit circuitslimit the energy to the loads in accordance with the UL standardClass. Supplementary protection to the power limit circuits can also include one or more fuses.

For the primary digital controller, the controllerprovides digital feedback control for the PFC Boostand DC/DC Converter. The digital feedback method for the PFC Boostutilizes average current mode control with duty cycle feed forward for the inner current loop and voltage mode control for the outer control loop. The DC/DC Converterutilizes voltage mode control for the digital control loop.

The primary digital controlleralso controls the inrush current limit circuit, provides primary current limit protection, and over voltage protection for the output of the PFC Boost. The primary digital controlleralso disables the PFC Boostand the DC/DC Converterduring black out or no load conditions to reduce power dissipation.

With respect to the output current drivers, configuring the required number of outputs and required output current is accomplished by populating the appropriate sections of a single printed circuit board with the appropriate electrical components and programming the output current driver via the in-circuit serial programming (ICSP) ports.

Turning to, which is an embodiment of an output current driver, the output current drivercomprises a load controller, a current source, and current sense. Although only one current driveris shown, it will be understood that multiple are present as reflected in.

The output current driver may utilize either the dimming/color mixing techniques for LEDs described in detail in US Patent Publication No. 2007/0103086, or the techniques described in detail in International Publication WO2011/140660 which is hereby incorporated by reference.

The secondary controllerreceives dimming or color mixing information in the form of a serial data stream from the external transmittervia the communication interfaceand then translates the data stream into LED control information. The LED control information is transmitted to the load controllerin the form of instructions to generate a digital signaland an analog signal.

The load controllerfurther comprises a signal generatorwhich transmits the digital signaland the analog signalto the current source. The digital control signaland the analog signalare preferably generated via a digital control algorithm and 1 Bit algorithm, respectively.

The current sourcepreferably includes ancillary circuitry for operation and comprises a buck topology power stage with hysteretic control. The current senseprovides a digital feedback loop for each current source. In the preferred embodiment, the current sourceis a buck circuit topology however other embodiments can include topologies such as boost, buck-boost, or single ended primary inductor converter (SEPIC).

Outputof the current driverprovides a current pulse via current sourceto the LED Loadwhereby on times, off times, and period are not held constant.

Each output current driver, has an associated in-circuit serial programming (ICSP) port. The ICSP portprovides access to the load controllersuch that firmware updates are possible to permit the configuration of the output current drivers. The ICSP port(s)for the output current driver(s)can be located on the printed circuit board assembly of the apparatus or they can be located on the outside of the enclosure.

The configuration options include, but are not limited to, such parameters as the adjustment of the frequency range of the dimming current pulse for the range of light intensity output or the set point adjustment of the peak on time output current.

For example, it might be necessary to increase the frequency range of the dimming current pulse in video recording applications where the dimming current pulse frequency can be programmed for a 2000 Hz to 2500 Hz range. This would negate a visible beat frequency effect that would other wise be noticeable on recorded video. There can be other applications where the adjustment of the dimming current frequency range is required to reduce EMI effects.

The default peak output current set point is programmed via the ICSP portwhich provides flexibility in the number of possible LEDs types that can be driven and is typically dependent on the recommended operating current specified by the manufacturer such as 350 mA, 700 mA, etc. The set point current is preferably programmed to within 4% of the manufacturer's specification. The peak output current set point can then be precisely calibrated to within typically 1% via the secondary controllerduring factory calibration.

An alternate embodiment of an output current driveris shown in. In this embodiment, the output current drivercomprises a load controllerincluding a signal generator. A current sourceand a current senseare located within an apparatus, such as a light fixture. The light fixturealso includes the LED load. After receiving the LED control information from the secondary controller, the signal generatorprovides a data signal to the light fixtureto operate the LED loadvia the current sourceand the current sense. This is also schematically shown in.

is a schematic diagram of an alternate embodiment of a configurable LED dimmer. As shown, individual current sourcesand current sensesare mounted in the light fixture containing the LED load, and power and data signals are provided to each output current sourceby the multi conductor cable. In this embodiment, the current sourcesare configured to regulate to a predetermined peak current. The load controllertransmits the data signal containing the output current information encoded within the three variables of on time, off time, and period whereby no three variables are held constant.

Turning to, a known application of internal auxiliary power requirements in a multistage power source is shown and illustrates how auxiliary power is provided to the various blocks of a multistage power source. P, P. . . Prepresents the various power and voltage transfer requirements for each functional block. For simplicity, the various voltage regulator and filter circuits required for each of the power outputs have been omitted.

In operation, the bridge rectifier converts the AC mains voltage Pto a rectified voltage P. A portion of power Pfrom the output of the bridge rectifier Pis supplied to the start up circuit. The start up circuit is comprised of a power transistor or MOSFET and is intended to provide power Pto the PFC analog controller for only a short duration of a few seconds. Power Pto the PFC analog controller will allow the PFC Boost stage to begin switching, providing power Pto the DC/DC controller, and power Pto the DC/DC converter power stage. Since the start up circuit dissipates an excessive amount of power, it is turned off by the voltage component of Psupplied by the PFC boost stage. The Ppower is permitted to ‘flow through’ the start up circuit to continue to supply power Pto the PFC analog controller.