Patent Description:
A driver is often used to provide power to one or more light sources of a lighting device. For example, a light emitting diode (LED) driver may provide power to one or more LED light sources of one or more lighting fixtures. In general, an LED driver may receive AC (alternating-current) power (e.g., mains electricity) and generate DC (direct-current) power that is provided to one or more light sources. It is generally desirable for drivers to have a good power factor and low harmonic distortion for efficient operation. However, a driver of an outdoor or another type of light fixture may be damaged by a power surge that renders the driver unable to provide adequate power to the light fixture. Such damage can render the light fixture unable to provide light. In some cases, a surge protection unit may be placed ahead of or integrated in a driver of a light fixture. However, in general, many surge protection modules protect against a first power surge exposure but are prone to failure due to subsequent power surge(s). In cases where light fixtures are installed in public arenas (e.g., a stadium) as well as other cases, a total light outage can be highly inconvenient. Thus, a solution that enables a light fixture to continue to provide light after a driver of the light fixture is damaged may be desirable.

<CIT> discloses an approach for controlling a direct current gain of a resonant converter to increase power efficiency within a circuit. A phase shift module is configured to the resonant converter for generating a first control signal to control a primary driver of the resonant converter and a secondary control signal to control a secondary driver of the resonant converter. The first control signal and the second control signal has a phase shift for controlling a DC gain of the resonant converter. <CIT> discloses a redundant lighting driver system having a primary LED driver and a backup LED driver.

The present disclosure relates generally to lighting solutions, and more particularly to redundant lighting driver systems. In an example embodiment, a redundant lighting driver system includes a primary driver and a backup driver. The primary driver and the backup driver are electrically coupled to receive an alternating current (AC) power from a power source. The primary driver or the backup driver power a light source at a time. The primary driver is configured to provide a primary power to the light source, and the backup driver is configured to provide a backup power to the light source when the primary power is unavailable. The backup driver is designed to withstand a larger power surge than the primary driver.

In another example embodiment, a lighting system includes a primary driver and a backup driver, where the primary driver and the backup driver are electrically coupled to receive an alternating current (AC) power from a power source. The lighting system further includes a light source, where the primary driver or the backup driver power the light source at a time. The primary driver is configured to provide a primary power to the light source, and the backup driver is configured to provide a backup power to the light source when the primary power is unavailable. The backup driver is designed to withstand a larger power surge than the primary driver.

These and other aspects, objects, features, and embodiments will be apparent from the following description and the appended claims.

The drawings illustrate only example embodiments and are therefore not to be considered limiting in scope. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Additionally, certain dimensions or placements may be exaggerated to help visually convey such principles. In the drawings, the same reference numerals used in different drawings may designate like or corresponding but not necessarily identical elements.

In the following paragraphs, example embodiments will be described in further detail with reference to the figures. In the description, well known components, methods, and/or processing techniques are omitted or briefly described. Furthermore, reference to various feature(s) of the embodiments is not to suggest that all embodiments must include the referenced feature(s).

<FIG> illustrates a lighting system <NUM> including a redundant lighting driver system <NUM> according to an example embodiment. For example, the lighting system <NUM> may be an outdoor light fixture <NUM> that provides an illumination light to an area (e.g., a stadium, a parking lot, etc.) where a light outage is highly inconvenient. As another example, the lighting system <NUM> may be an indoor light fixture <NUM> that provides an illumination light to an area such as, for example, an indoor sport arena. In some example embodiments, the lighting system <NUM> includes the redundant lighting driver system <NUM> and a light source <NUM>. For example, the light source <NUM> may be a light emitting diode (LED) light source that includes multiple LEDs having a forward voltage VF across the LEDs. For example, if the light source <NUM> has five LEDs that are in a series configuration, the forward voltage VF may be the total forward voltage across all of the five LEDs. A current IDC provided to the light source <NUM> by the redundant lighting driver system <NUM> must be adequate for the light source <NUM> to emit a light.

In some example embodiments, the redundant lighting driver system <NUM> receives AC power from an AC source <NUM> such as a utility or mains power source. For example, the AC power source <NUM> may provide an AC voltage VIN to the redundant lighting driver system <NUM>. An input voltage VI that includes the AC voltage VIN may be provided to the redundant lighting driver system <NUM>. For example, the input voltage VI may include a transient voltage surge that may be introduced in the power line connecting the AC power source <NUM> and the redundant lighting driver system <NUM>. In general, the transient voltage surge is characterized by a very large voltage spike that lasts for a very short time. For example, a transient voltage surge may have a duration between <NUM> to <NUM> and may reach a peak voltage of <NUM> kV (kilovolts) or higher. In general, a transient voltage surge may result from a heavy electrical load switching or from a lightning strike. When no other voltage is introduced in the line connection between the AC power source <NUM> and the redundant lighting driver system <NUM>, the input voltage VI is essentially the same as the AC voltage VIN.

In some example embodiments, the redundant lighting driver system <NUM> includes a primary driver <NUM> and a backup driver <NUM>. The primary driver <NUM> and the backup driver <NUM> are both electrically coupled to the AC power source <NUM>. The input voltage VI that is provided to the redundant lighting driver system <NUM> is provided to both the primary driver <NUM> and the backup driver <NUM>. The primary driver <NUM> is designed to provide a primary power to the light source <NUM> from the input power VI, and the backup power <NUM> is designed to provide a backup power to the light source <NUM> from the input power VI. The redundant lighting driver system <NUM> is designed such that the backup power is less than the primary power.

To illustrate, the primary driver <NUM> is designed to provide a primary current IDC1 to the light source <NUM>, and the backup driver <NUM> is designed to provide a backup current IDC2 to the light source <NUM>. For example, the primary driver <NUM> may be a constant current driver designed to provide particular amounts of the current IDC1 based on respective levels of the input voltage Vi, which is the same as the AC voltage VIN in the absence of an input power surge/transient voltage surge. The redundant lighting driver system <NUM> is designed such that either the primary driver <NUM> or the backup driver <NUM> provides the current IDC to the light source <NUM> at a time. That is, the primary driver <NUM> and the backup driver <NUM> do not provide a power to the light source <NUM> at the same time, except possibly during transition times when switching between the drivers <NUM>, <NUM>.

In some example embodiments, the redundant lighting driver system <NUM> may include power diodes <NUM>, <NUM>. The anode of the power diode <NUM> is coupled to the output of the primary driver <NUM>, and the anode of the power diode <NUM> is coupled to the output of the backup driver <NUM>. The cathodes of the power diodes <NUM>, <NUM> are electrically connected to each other, for example, at a node <NUM>, where the current IDC1 or the current IDC2 is provided to the light source <NUM> through the node <NUM> at one time. To illustrate, the current IDC provided to the light source <NUM> corresponds to the current IDC1 provided by the primary driver <NUM> when the primary driver <NUM> powers the light source <NUM>. The current IDC corresponds to the current IDC2 provided by the backup driver <NUM> when the backup driver <NUM> powers the light source <NUM>.

In some example embodiments, the redundant lighting driver system <NUM> is designed such that the primary driver <NUM>, instead of the backup driver <NUM>, powers the light source <NUM> when the primary driver <NUM> is functioning properly. That is, at a particular AC voltage VIN provided to the redundant lighting driver system <NUM>, the current IDC1 from the primary driver <NUM> is greater than the current IDC2, which results in the power diode <NUM> being forward biased and the power diode <NUM> being reverse biased, where the current IDC through the light source <NUM> is the current IDC1. When the primary driver <NUM> fails to provide the current IDC1 or malfunctions such that the current IDC1 is less than the current IDC2, the power diode <NUM> is forward biased and the power diode <NUM> is reverse biased, where the current IDC through the light source <NUM> is the current IDC2.

In some example embodiments, the primary driver <NUM> may provide power factor correction, which can increase energy efficiency and reduce electricity costs. The primary driver <NUM> may also perform current regulation to provide a regulated current to the light source <NUM>. To illustrate, the current IDC1 may be a regulated current that does not meaningfully change due to changes to load resulting from the light source <NUM>. The primary driver <NUM> may also include other components such as a rectifier, an output transformer, etc. as can be readily understood by those of ordinary skill in the art with the benefit of the scope of this disclosure. Different ways of implementing power factor correction, current regulation, and other common functions of the primary driver <NUM> are well known to those of ordinary skill in the art. To illustrate, the primary driver <NUM> may be an off-the-shelf constant current driver. In some example embodiments, the primary driver <NUM> may include a surge protection unit to protect against input power surge that may appear in the input voltage VI provided to the redundant lighting driver system <NUM>. Alternatively, the primary driver <NUM> may not include a surge protection unit. In yet some other alternative embodiments, an external surge protection unit may be positioned to provide surge protection to the primary driver <NUM> as can be readily understood by those of ordinary skill in the art with the benefit of the scope of this disclosure.

In some example embodiments, the backup driver <NUM> may be designed to include robust surge protection against input power surges. For example, the backup driver <NUM> includes a surge protection unit to protect against power surges that may appear in the input voltage VI provided to the redundant lighting driver system <NUM>. To illustrate, even when the primary driver <NUM> includes a power surge protection unit, the backup driver <NUM> provides more power surge protection than the primary driver <NUM>. For example, the backup driver <NUM> may provide protection against higher surge energy and more power surges than the primary driver <NUM> or a surge protection unit coupled to the primary driver <NUM>.

In some example embodiments, because the main purpose of the backup driver <NUM> is to provide backup power to the light source <NUM> until a defective primary driver (e.g., the primary driver <NUM> that has failed) is repaired or replaced, the backup power provided by the backup driver <NUM> may be relatively lower quality than the primary power provided by the primary driver <NUM>. For example, the backup driver <NUM> may not perform power factor correction and/or output current regulation. Excluding such functions from the backup driver <NUM> may result in the backup driver <NUM> being robust and having a lower production cost.

Because the backup driver <NUM> has higher power surge protection than the primary driver <NUM>, the backup driver <NUM> is designed to provide power to the light source <NUM> when the primary driver <NUM> fails due to an input power surge although the primary driver <NUM> and the backup driver <NUM> are exposed to the same input power surge. By providing power to the light source <NUM> using the backup driver <NUM>, the redundant lighting driver system <NUM> enables the lighting system <NUM> to continue to provide a light when the primary driver <NUM> fails or is disabled. The lighting system <NUM> may to continue to provide a light after the failure of the primary driver <NUM> while the primary driver <NUM> is being repaired or replaced.

In some example embodiments, the redundant lighting driver system <NUM> may provide power to one or more other light sources in addition to the light source <NUM>. In some alternative embodiments, one or more components other than the diodes <NUM>, <NUM> that enable automatically switching between the primary driver <NUM> and the backup driver <NUM> to provide power to the light source <NUM> may be used without departing from the scope of this disclosure. In some alternative embodiments, the lighting system <NUM> may include components other than what is shown in <FIG> without departing from the scope of this disclosure. In some alternative embodiments, the redundant lighting driver system <NUM> may include components other than what is shown in <FIG> without departing from the scope of this disclosure. In some alternative embodiments, the components of the lighting system <NUM> may be connected in a different configuration than what is shown without departing from the scope of this disclosure.

<FIG> illustrates the lighting system <NUM> of <FIG> showing some details of the redundant lighting driver system <NUM> according to an example embodiment. Referring to <FIG> and <FIG>, in some example embodiments, the backup driver <NUM> may include an inductor unit <NUM>, a rectifier <NUM>, and a capacitor <NUM>. The inductor unit <NUM> is electrically coupled to the power source <NUM> to receive the AC voltage VIN from the power source <NUM>. As indicated above, the input voltage VI may be essentially the same as the AC voltage VIN when no other voltage is introduced in the line connection between the AC power source <NUM> and the redundant lighting driver system <NUM>.

In some example embodiments, the inductor unit <NUM> is also coupled to the rectifier <NUM>. For example, the rectifier <NUM> may be a bridge rectifier as shown in <FIG> or may be another type of rectifier without departing from the scope of this disclosure. The reverse voltage rating of the rectifier <NUM> may be, for example, <NUM> volts. The rectifier <NUM> may rectify the voltage VO from the inductor unit <NUM> as can be readily understood by those of ordinary skill in the art with the benefit of the scope of this disclosure. The rectifier <NUM> may also be coupled to the capacitor <NUM>. For example, the capacitor <NUM> may be a direct current (DC) capacitor with a voltage rating of <NUM>% of the forward voltage of the LED(s) of the light source <NUM>. The current IDC2 is provided by the backup driver <NUM> through a node <NUM> connecting the rectifier <NUM> and the capacitor <NUM> as shown in <FIG>. To illustrate, the node <NUM> is coupled to the anode of the diode <NUM> such that the current IDC2 is provided to the light source <NUM> through the diode <NUM>.

In some example embodiments, the inductor unit <NUM> is designed to have an inductance L that limits the current IDC2 from the backup driver <NUM> to be lower than the current IDC1 from the primary driver <NUM> such that, when the current IDC1 is available, the diode <NUM> is reverse biased and the diode <NUM> is forward biased. When the current IDC1 is unavailable, for example, because the primary driver <NUM> is damaged by a transient surge in the input voltage VI, the diode <NUM> becomes forward biased and the diode <NUM> becomes reverse biased such that the current IDC2 is provided to the light source <NUM>.

To illustrate, the voltage VO between the inductor unit <NUM> and the rectifier <NUM> is related to the LED forward voltage of the light source <NUM> (i.e., the forward voltage of LED(s) of the light source <NUM>). The rms current Irms through the inductor unit <NUM> is related to the current IDC2, which is the same as the current IDC through the light source <NUM> when the diode <NUM> is forward biased and the diode <NUM> is reverse biased. Equation <NUM> below illustrates the relationship: <MAT>.

Equation <NUM> below shows the relationship between the rms current Irms through the inductor unit <NUM> and the inductance L of the inductor unit <NUM>: <MAT>.

For the purpose of Equation <NUM>, VIN - VO represents the voltage VL across the inductor unit <NUM>, and the AC voltage VIN may be replaced by the input voltage VI in the absence of a voltage spike/power surge. As can be seen from Equations <NUM> and <NUM>, the current IDC through the light source <NUM>, which is the same as the current IDC2 when the backup driver <NUM> is powering the light source <NUM>, is a function of the AC voltage VIN. For example, the AC voltage VIN may vary between <NUM> volts to <NUM> volts. The inductor unit <NUM> may be designed or selected to have an inductance L that results in the current IDC2 being less than the current IDC1 provided by the primary driver <NUM> when the primary driver <NUM> is functioning properly.

In some example embodiments, the value of the inductance L may be selected/determined with respect to Equations <NUM> and <NUM> based on the AC voltage VIN at the maximum level (e.g., <NUM> volts). An inductive component that has an inductance value determined based on Equations <NUM> and <NUM> with the AC voltage VIN set to the maximum level (e.g., <NUM> volts) may be selected as the inductor unit <NUM>. Although a value of the inductance L selected/determined based on the maximum level of the AC voltage VIN may result in a reduced amount of the current IDC2 and a dimmer light when levels of the input voltage VIN are below the maximum level, the reduced amount of the current IDC2 can still enable the light source <NUM> to emit an adequate level of light. By automatically providing power to the light source <NUM> after an exposure to a power surge that has disabled the primary driver <NUM>, the backup driver <NUM> enables the lighting system <NUM> to continue to provide a light.

In some alternative embodiments, the backup driver <NUM> may include components other than what is shown in <FIG> without departing from the scope of this disclosure. In some alternative embodiments, the components of the backup driver <NUM> may be connected in a different configuration than what is shown without departing from the scope of this disclosure. In some alternative embodiments, the backup driver <NUM> may be implemented as multiple components without departing from the scope of this disclosure.

<FIG> illustrates a graph of the input voltage VI at the input of the backup driver <NUM> of the redundant lighting driver system <NUM> of <FIG> according to an example embodiment. Referring to <FIG>, in some example embodiments, the input voltage VI at the input of the redundant lighting driver system <NUM>, and thus at the input of the backup driver <NUM>, may include a transient voltage surge <NUM> that is imposed on the AC voltage VIN from the AC power source <NUM>. For example, the transient voltage surge <NUM> may be a result of a lightning strike that hit the line connection between a municipality power source and the lighting system <NUM>. The input voltage VI at the inductor unit <NUM> (e.g., the inductor unit <NUM> with inductance L of <NUM> mH at <NUM> Hz of the AC voltage VIN) may reach, for example, approximately <NUM>,<NUM> volts and may have a duration of, for example, approximately <NUM> milliseconds (ms). After the duration of the transient voltage surge <NUM>, the input voltage VI returns to the level of the AC voltage VIN in a range of approximately <NUM> volts to <NUM> volts rms, and the inductor voltage across the inductor unit <NUM> correspondingly decreases. In <FIG>, although the input voltage VI appears to be zero due to the relatively large voltage spike, the amplitude of the input voltage VI is in a range of approximately <NUM> volts to <NUM> volts.

In some alternative embodiments, the peak amplitude of the voltage spike may be more or less than what is shown without departing from the scope of this disclosure. In some alternative embodiments, the duration of the voltage spike may be more or less than what is shown without departing from the scope of this disclosure. In some alternative embodiments, the AC voltage VIN may be in a range that is more than <NUM> volts or less than <NUM> volts without departing from the scope of this disclosure.

<FIG> illustrates a graph of a DC voltage VDC that is the increase in the output voltage VDC2 of the backup driver <NUM> resulting from the transient voltage surge shown in <FIG> according to an example embodiment. In <FIG>, the graph illustrates the DC voltage VDC when no load is attached to the backup driver <NUM> (i.e., the open-circuit voltage). Referring to <FIG>, in some example embodiments, because the inductor unit <NUM> slows down the energy from the transient voltage surge <NUM> shown in <FIG> from instantaneously reaching the output voltage VDC2, the increase in the output voltage VDC2 of the backup driver <NUM>, i.e., the DC voltage VDC shown in <FIG>, is significantly lower than the amplitude of the transient voltage surge <NUM>. For example, as shown in <FIG>, the DC voltage VDC, even with no load attached to the backup driver <NUM>, is about <NUM> volts, which is an acceptable voltage increase in the output voltage VDC2 of the backup driver <NUM> with respect to damage to components, despite the relatively large transient voltage surge <NUM>. When a load (e.g., the light source <NUM>) is attached to the backup driver <NUM> as shown in <FIG>, the output voltage VDC2 of the backup driver <NUM> will be clamped by the load (e.g., the diode <NUM> and the light source <NUM>), and thus limiting the DC voltage VDC. By slowing the increase in the output voltage VDC2 of the backup driver <NUM>, the inductor unit <NUM> can prevent the transient voltage surge <NUM> from damaging the light source <NUM> as well as other components of the lighting system <NUM>.

In <FIG>, voltage values and time values are illustrative examples and may have other values (i.e., higher values or lower values) without departing from the scope of this disclosure. In <FIG>, the forward voltage VF may settle at a normal operating voltage level at a faster or slower rate than what may be suggested by the graph without departing from the scope of this disclosure.

<FIG> illustrates an inductor <NUM> that corresponds to the inductor unit <NUM> of <FIG> according to an example embodiment. For example, the inductance of the inductor <NUM> is the same as the inductance L of the inductor unit <NUM>. In some example embodiments, the inductor unit <NUM> includes the inductor <NUM> as well as other components. Referring to <FIG> and <FIG>, in some example embodiments, the inductor <NUM> may include a coil <NUM> that is wound around a magnetic core <NUM>. The turns of the coil <NUM> may be separated by a turn-to-turn insulator T, and different layers of the coil <NUM> may be separated by a layer-to-layer insulator. Turn-to-turn insulation and layer-to-layer insulation reduces risk of electrical discharge within the coil <NUM> that would otherwise lead to failure. Opposite ends of the coil <NUM> serve as input and output connections of the inductor <NUM>. For example, the input voltage VI may be provided to the first end Line In, and the voltage Vo, shown in <FIG>, may be available at the other end, Line Out, of the coil <NUM> and provided to the rectifier <NUM> shown in <FIG>. The inductance of the inductor <NUM> may depend on a number of parameters including the number of turns of the coil <NUM>, dimensions of the coil <NUM>, etc. as readily understood by those of ordinary skill in the art with the benefit of the scope of this disclosure. For example, the inductor <NUM> may be designed to withstand a transient voltage surge of <NUM> kV or higher.

In some alternative embodiments, the inductor <NUM> may have a different structure than what is shown in <FIG> without departing from the scope of this disclosure. In some alternative embodiments, the inductor <NUM> may include other elements without departing from the scope of this disclosure.

<FIG> illustrates a transformer <NUM> that corresponds to the inductor unit <NUM> of <FIG> according to an example embodiment. For example, the inductance of the transformer <NUM> is the same as the inductance L of the inductor unit <NUM>. In some example embodiments, the inductor unit <NUM> includes the transformer <NUM> as well as other components. Referring to <FIG> and <FIG>, in some example embodiments, the transformer <NUM> may include a primary coil <NUM> and a secondary coil <NUM> that are wound around respective sections of a magnetic core <NUM>. The primary coil <NUM> and the secondary coil <NUM> are separated from each other by an air gap that may be partially occupied by an air gap spacer or magnetic shunt <NUM>. The resulting leakage inductance serves as the inductance of the transformer <NUM>. The leakage inductance may depend on a number of factors such as the spacing between the primary coil <NUM> and the secondary coil <NUM>, the air gap spacer or magnetic shunt <NUM>, etc. as can be readily understood by those of ordinary skill in the art with the benefit of the scope of this disclosure. The input voltage VI may be provided to the input connection Line In of the primary coil <NUM> of the transformer <NUM>, and the voltage Vo, shown in <FIG>, may be available at the output connection Line Out of the secondary coil <NUM> of the transformer <NUM> and provided to the rectifier <NUM> shown in <FIG>.

In some example embodiments, the transformer <NUM> may be a step-up or a step-down transformer based on the windings of the primary coil <NUM> and the secondary coil <NUM> as can be readily understood by those of ordinary skill in the art with the benefit of the scope of this disclosure. In some example embodiments, the transformer <NUM> may include taps (not shown) for selecting between different input and output voltage relationships as can be readily understood by those of ordinary skill in the art with the benefit of the scope of this disclosure.

In some alternative embodiments, the transformer <NUM> may have a different structure than what is shown in <FIG> without departing from the scope of this disclosure. In some alternative embodiments, the transformer <NUM> may include other elements without departing from the scope of this disclosure.

Claim 1:
A redundant lighting driver system (<NUM>), comprising:
a primary driver (<NUM>);
a backup driver (<NUM>), wherein the backup driver includes an inductor unit (<NUM>) that limits time varying current,
characterized in that the inductor unit (<NUM>) is sized such that both the backup driver withstands a transient surge voltage having a duration less than <NUM> and an output voltage provided by the backup driver is less than an output voltage provided by the primary driver when powering a light source (<NUM>);
wherein the primary driver and the backup driver are each configured to receive an alternating current (AC) power from a power source (<NUM>), wherein the inductor unit (<NUM>) receives the AC power for the backup driver; and
wherein the primary driver is configured to provide a primary power to the light source, and wherein the backup driver is configured to provide a backup power to the light source when the primary driver is disabled due to a power surge, wherein the backup power is less than the primary power.