CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Patent Application

No. 61/635,556 titled "Emergency Battery Converter" and filed April 19, 2012, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

[0002] The present disclosure relates generally to an emergency battery Direct

Current/Direct Current (DC/DC) converter used in place of traditional battery Direct Current/Alternating Current (DC/AC) converters for emergency egress luminaires including emergency LED egress luminaires, and more particularly to systems, methods, and devices for an emergency battery DC/DC converter.

BACKGROUND

[0003] In case of a power fault event in a power delivery system, such as a power outage, emergency lighting is often used to provide a basic level of lighting needed in an egress area. Traditionally, emergency lighting, such as emergency LED luminaires, are generally either connected to an emergency battery pack with LED emergency driver or to an emergency battery pack with 50/60 Hertz alternating current (AC) inverter. AC inverters are gaining popularity due to the complexity and variety of LED configurations, which makes it very challenging to provide a single universal LED emergency driver solution. Most commercial LED drivers utilize a diode bridge circuit to rectify the AC line voltage to DC bus voltage when there is either active regulation or passive filtering. If a high DC voltage that is equivalent to a rectified AC line potential is electrically connected to the line and neutral input leads of the typical commercial LED driver; the LED driver generally does not know the difference. Thus, the driver will operate as intended. However, inverting battery power to a 50/60 Hertz AC line voltage generally requires relatively bulky equipment due to the necessary components, such as a laminated steel transformer. Such systems also have relatively higher material cost and may be relatively inefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0005] Figure 1 is a system view of an example operating environment for a low cost emergency battery DC/DC converter according to one example embodiment;

[0006] Figure 2 is a diagram of an emergency battery DC/DC converter according to one example embodiment;

[0007] Figure 3 is a diagram of a commercial lighting driver according to one example embodiment;

[0008] Figure 4 is a diagram of an emergency luminaire according to one example embodiment; and

[0009] Figure 5 is a process flow diagram of an example method of emergency lighting.

[0010] The drawings illustrate only example embodiments of the disclosure and are therefore not to be considered limiting of its scope, as the disclosure may admit to other equally effective embodiments. The elements and features shown in the drawings are not necessarily drawn to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Additionally, certain dimensions or positionings may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0011] In the following paragraphs, the present disclosure will be described in further detail by way of example with reference to the attached drawings. In the description, well known components, methods, and/or processing techniques are omitted or briefly described so as not to obscure the disclosure. Furthermore, reference to various feature(s) of the example embodiments is not to suggest that all embodiments must include the referenced feature(s).

[0012] Turning now to the drawings, certain example embodiments are described in detail. Figure 1 presents a view of an example system 10 for a low cost emergency battery DC/DC converter according to one example embodiment. The example system 10 includes an emergency battery pack 100, a commercial lighting driver 1 10, and an emergency luminaire 120. In certain example embodiments, emergency lighting includes, but is not limited to, ceiling, wall, or floor mounted egress lighting, exit signs, directional signs, spot lighting and the like. Generally, the system 10 may be used to provide lighting for an egress path for a building in case of a power failure. It is noted, however, that the system 10 may also be used in environments other than for lighting an egress path.

[0013] The emergency battery pack 100 is electrically coupled to at least one line voltage of a power delivery system. In an example embodiment, and as illustrated in Figure 1, the emergency battery pack 100 is electrically coupled to an unswitched line (U) of the power delivery system, a neutral line (N) of the power delivery system, and a switched line (S) of the power delivery system. The line voltage provided by the power delivery system may be a standard 120VAC line voltage, for example. Other input line voltages, configurations, or connections between the power delivery system and the emergency battery pack 100 are within the scope and spirit of this disclosure as understood by those having ordinary skill in the art, without limitation. The example emergency battery pack 100 stores power from the switched or unswitched line voltages of the power delivery system in a storage device such as a battery, capacitor, or supercapacitor, for example, without limitation. The power is stored for use by the emergency luminaire 120 in case of a failure of the power delivery system. In certain example embodiments, in order to ensure a predictable outcome, the emergency battery pack 100 is electrically decoupled from the power delivery system when a failure does occur and the storage device is providing power to the emergency luminaire 120. The emergency battery pack 100 includes an efficient converter that converts an output voltage of the storage device of the emergency battery pack 100 into a stepped-up output voltage, as described in further detail below with reference to Figure 2. In an example embodiment, the output voltage of the storage device of the emergency battery pack 100 is a non-varying or DC output voltage. Similarly, the stepped-up output voltage of the emergency battery pack 100 is also a non-varying or DC output voltage, but stepped-up to a higher potential voltage than the potential voltage output by the storage device.

[0014] As compared to a conventional emergency battery which provides an output voltage that mimics the 120VAC line voltage provided by the power delivery system in case of power delivery system failure, the emergency battery pack 100 provides a non-varying high potential DC output voltage, designated by the L(+) and N(-) outputs in Figure 1. In one example embodiment, the voltage or potential of the stepped-up output voltage of the emergency battery pack 100 may correspond to a rectified voltage potential of the standard 120VAC line voltage, or approximately 150VDC. In other embodiments, the potential of the stepped-up output voltage of the emergency battery pack 100 may be greater or less than 150VDC. As described in further detail below, however, as compared to a conventional emergency battery which provides an AC output voltage, the emergency battery pack 100 is designed to be relatively smaller, cheaper, and simpler, because it converts the DC output voltage of the storage device (i.e., battery) of the emergency battery pack 100 to a stepped-up DC output voltage rather than to an AC output voltage.

[0015] The example commercial lighting driver 1 10 is electrically coupled to the emergency battery pack 100 and receives the stepped-up output voltage generated by the emergency battery pack 100. In certain example embodiments, the commercial lighting driver 1 10 includes rectifiers, filters, regulators, and other associated circuitry that regulates the stepped-up output voltage to a regulated voltage suitable for powering the emergency luminaire 120, as described in further detail below with reference to Figure 3. It is noted that the commercial lighting driver 110 and the circuitry of the commercial lighting driver 1 10 may be designed and listed for a standard 120VAC line input voltage provided by conventional emergency batteries or power delivery systems.

[0016] Figure 2 is a diagram of the emergency battery DC/DC converter 100 according to one example embodiment. Referring now to Figures 1 and 2, an example emergency battery DC/DC converter 100 includes charging circuitry 202, control circuitry 204, a storage device 206, and a step-up converter 208. The charging circuitry 202 includes circuitry that rectifies, filters, and regulates power from the line input voltage of the power delivery system to power that charges the storage device 206. The charging of the storage device 206 may be, at least in part, under the supervision and control of the control circuitry 204. For example, the control circuitry 204 may monitor the amount of charge stored in the storage device 206 and start or stop any charging of the storage device 206 depending upon the amount of charge stored. As noted above, the storage device 206 may include a battery. In certain example embodiments, the storage device 206 may include a lead-acid, nickel cadmium (NiCd), nickel metal hydride (NiMH), lithium ion (Li-ion), or lithium ion polymer (Li-ion polymer) battery, for example, without limitation. In other example embodiments, the storage device 206 may include a fast-charge capacitor or supercapacitor. Once charged by the charging circuitry 202, the storage device 206 maintains sufficient charge to provide power to the emergency luminaire 120 via the commercial lighting driver 1 10 in case of failure of the power delivery system. In one example embodiment, the failure of the power delivery system may be detected by the control circuitry 204 by a drop in line voltage provided by the power delivery system. In this case, the control circuitry 204 may control the storage device 206 and the step-up converter 208 to provide a stepped-up output voltage for powering the emergency luminaire 120. [0017] The example step-up converter 208 includes circuitry to step-up the output voltage of the storage device 206 to a higher voltage. As noted above, in one example embodiment, the output voltage of the storage device 206 is a non-varying DC output voltage, and the step-up converter 208 increases the output voltage of the storage device 206 to a stepped-up DC output voltage. In certain example embodiments, the step-up converter 208 may include a boost or buck converter, but other configurations are within the scope and spirit of this disclosure. As such, the step-up converter 208 may include one or more inductors, electronically-controlled switches, diodes, and associated filtering circuitry such as capacitive, inductive, and resistive networks and combinations thereof. The step-up converter 208 may provide a stepped-up output voltage at a predetermined potential depending upon its design and based on the control of the control circuitry 204. In one example embodiment, the stepped-up output voltage is a 150VDC output voltage.

[0018] It is noted that, in case of failure of the power system, conventional emergency battery packs output a time-alternating or AC output voltage. To achieve this, conventional emergency battery packs generally include circuitry that converts the DC output voltage of a battery to an AC output voltage. Commonly, this DC/AC conversion circuitry requires at least one large and heavy transformer including a ferrite core. In contrast to conventional emergency battery packs, the step-up converter 208 is relatively simpler, smaller, and less costly. As described in further detail below with reference to Figure 3, the commercial lighting driver 110 is able to operate suitably with the stepped-up voltage output by the step- up converter 208, even if the commercial lighting driver 110 is listed for a standard AC line input voltage.

[0019] In certain example embodiments, the emergency battery pack 100 also includes an A/C inverter 210 that converts the stepped-up DC output voltage provided by the step-up converter 208 to an AC output voltage. In an example case, the A/C inverter 210 may be embodied as an "H" bridge including several electronically controlled switches that flip the polarity of the stepped-DC up output voltage from the step-up converter 208 over the L and N AC output voltage terminals, thus generating a time-alternating AC output voltage. The A/C inverter 210 may also include filtering circuitry such as capacitive, inductive, and resistive networks and combinations thereof, to round or soften the edges of the AC output voltage caused by hard switches of the "H" bridge. The A/C inverter 210 may be provided as a connection to commercial lighting drivers that require an AC input voltage or to meet electrical code requirements of state and municipal authorities.

[0020] Figure 3 is a diagram of the commercial lighting driver 110 according to one example embodiment. Now referring to Figure 3, the example commercial lighting driver 1 10 includes a rectifier 302, a converter/filter 304, and a regulator 306. As noted above, the commercial lighting driver 110 may be designed for the input of a standard 120VAC line voltage. Generally, the commercial lighting driver 1 10 is configured to convert its input voltage to a voltage suitable for powering the emergency luminaire 120, which may be an LED emergency luminaire designed for a 12 or 24VDC input voltage in an example embodiment. In other embodiments, the commercial lighting driver 1 10 may convert its input voltage to a voltage suitable for powering emergency luminaires other than LED luminaires, such as fluorescent, compact fluorescent, neon, or incandescent luminaires, for example, without limitation. In certain embodiments, these other luminaires may include elements such as ballasts, for example, which are powered by the commercial lighting driver 1 10.

[0021] As the commercial lighting driver 1 10 converts an input AC line voltage to an output DC voltage, the rectifier 302 is provided to rectify the input AC line voltage to a rectified DC voltage. Among embodiments, the rectifier 302 may comprise any type of rectifier such as full or half wave rectifiers. The rectified voltage from the rectifier 302 is provided to the converter/filter 304. In certain embodiments, the converter/filter 304 includes an active DC/DC converter that converts an input DC voltage to an output DC voltage. That is, in certain embodiments, the converter/filter 304 converts a first input DC voltage to a second output DC voltage, where the first input DC voltage is greater in potential than the second output DC voltage. In other embodiments, the converter/filter 304 includes a passive filter that filters the rectified output of the rectifier 302. In embodiments where the converter/filter 304 includes an active DC/DC converter, the DC/DC converter may include a switching converter such as a buck or boost converter. In other embodiments where the converter/filter 304 includes a passive filter, the filter may include filtering circuitry such as capacitive, inductive, and resistive networks and combinations thereof. The regulator 306 further regulates the output of the converter/filter 304 to an output DC voltage suitable for powering the emergency luminaire 120.

[0022] The commercial lighting driver 1 10, which is representative of many types of commercial lighting drivers, although designed for a standard AC line voltage input, may operate based on the input of a DC voltage without any failure or degradation of operation. This is especially the case if the potential of the input DC voltage corresponds to the rectified potential of the standard AC line voltage. Thus, the example emergency battery pack 100 provides a DC voltage to the commercial lighting driver in place of an AC voltage. In this manner, the emergency battery pack 100 is lighter, smaller, and cheaper to manufacture as discussed above, because it provides a DC voltage rather than an AC voltage to the commercial lighting driver 110.

[0023] Figure 4 is a diagram of the emergency luminaire 120 according to one example embodiment. Now referring to Figure 4, the emergency luminaire 120 includes a converter 402, a driver 404, and a light source 406. The converter 402 converts the DC input voltage from the commercial lighting driver 1 10 into a DC voltage suitable for driving the light source 406. For example, the converter 402 may convert an input DC voltage at 12 or 24 VDC to an output voltage of lower potential. In this context, the converter 402 may include a switching converter such as a buck or boost converter or a passive converter such as a linear regulator. The driver 404 drives the light source 406 by providing sufficient power to the light source 406 to illuminate it. In general, the driver 404 regulates the power to the light source 406 by supplying a constant amount of power to the light source 406 as its electrical properties change with temperature, for example. In other words, the driver 404 provides the correct amount of power to the light source 406 so that it does not become too hot or unstable. In certain embodiments, the driver 404 is configured to control the power provided to the light source 406 according to pulse width modulation, slew rate, and/or on-off timings. In various embodiments, the light source 406 includes an LED light source or another light source such as fluorescent, compact fluorescent, neon, or incandescent light sources, for example, without limitation.

[0024] Figure 5 is a process flow diagram of an example method of emergency lighting. Referring to Figure 5, a method 500 of emergency lighting is described in detail. The method 500 is described with reference to the emergency battery pack 100, commercial lighting driver 110, and emergency luminaire 120 described above, but may be performed by equivalent elements as understood by those having skill in the art. At step 510, the storage device 206 stores power from a power delivery system. At step 520, the step-up converter 208 converts a Direct Current (DC) output voltage of the storage device 208 to a stepped-up DC output voltage. Proceeding to step 530, the commercial lighting driver 1 10 regulates the stepped-up DC output voltage to a regulated voltage suitable for powering an emergency luminaire, such as the emergency luminaire 120. After step 530, the emergency luminaire 120 illuminates an egress area based on the regulated output voltage at step 540.

[0025] Although example embodiments of the present disclosure have been described herein in detail, the descriptions are by way of example. The features of the example embodiments described herein are representative and, in alternative embodiments, certain features, elements, and/or steps may be added or omitted. Additionally, modifications to aspects of the embodiments described herein may be made by those skilled in the art without departing from the spirit and scope of the present disclosure defined in the following claims, the scope of which are to be accorded the broadest interpretation so as to encompass modifications and equivalent structures.