Patent Description:
Emergency lighting systems typically are designed to operate, upon mains failure, emergency lighting means off a central or decentral battery. Self-contained and centralized systems both usually rely on a single source for emergency operation. However, once the single source of energy for emergency operation is depleted, the emergency operation is ended as there is no alternative source available. There is no opportunity to extend emergency duration. Moreover, the lamp or emergency lighting means does not support alternative sources during emergency operation.

Document <CIT> discloses a lighting power supply system including a mains input converter operable to provide power, a controller operable to control at least one element of the lighting system, a controller bus and a controller interface operable to provide control signals from the bus to the lighting system. An auxiliary converter powers the lighting system from the bus and it may allow the controller to continue to be powered when the mains input is absent and an emergency battery is depleted.

Thus, it is an objective to provide an improved emergency driver for supplying emergency lighting means.

According to a first aspect of the invention, an emergency driver for supplying emergency lighting means is provided.

The emergency driver is configured to be powered, during operation of the emergency lighting means, selectively from: a local battery associated to the emergency driver or a DC network supplying DC power to DC terminals of the driver, wherein the emergency driver comprises a first circuitry configured to charge the local battery with DC power supplied to the DC terminals, and a second circuitry having the function to drive the emergency lighting means from the local battery and the function to drive the DC power supplied to the DC terminals. This has the advantage to smoothly transfer the lamp or emergency lighting means supply from its local battery to the DC network. In an embodiment, the emergency driver is furthermore configured to supply power from the local battery to the DC terminals in order to supply the DC bus.

In an embodiment, the emergency driver comprises a MOSFET bridge rectifier.

According to the invention the emergency driver comprises two controlled switches, wherein the switches are configured to connect or disconnect the driver from the DC network.

If the switches are turned on, then the local battery is charged and the emergency lighting means is supplied by the DC network.

In an embodiment, if the switches are turned off, then the local battery is configured to supply the emergency lighting means.

In an embodiment, the emergency lighting means comprises a LED module.

In an embodiment, the emergency driver further comprises a bidirectional DC-DC converter, wherein the DC-DC converter is configured to interface the local battery with the DC terminals.

In an embodiment, the DC-DC converter is a bidirectional switched isolated converter, such as e.g. flyback converter.

In an embodiment, the emergency driver comprises a further DC-DC converter, wherein the further DC-Dc converter is configured to drive the lighting means.

In an embodiment, the further DC-DC converter is a buck-boost converter.

In an embodiment, the emergency driver further comprises communication capabilities configured to demand power assistance from the DC network.

According to a second aspect, the invention relates to a method for supplying emergency lighting means, comprising: charging a local battery with DC power supplied to DC terminals, and driving the emergency lighting means from the local battery or the DC power supplied to the DC terminals.

Aspects of the present invention are described herein in the context of an emergency driver for supplying emergency lighting means.

Various aspects of an emergency driver for supplying emergency lighting means will be presented.

The term "LED luminaire" shall mean a luminaire with a light source comprising one or more LEDs. LEDs are well-known in the art, and therefore, will only briefly be discussed to provide a complete description of the invention.

Now referring to <FIG>, an embodiment of a system <NUM> comprising an emergency driver <NUM> for supplying emergency lighting means <NUM> is shown.

The emergency driver <NUM> is configured to be powered, during operation of the emergency lighting means <NUM>, selectively from:.

Moreover, the emergency driver <NUM> comprises:.

According to an embodiment, the emergency driver <NUM> is arranged such that during ongoing emergency operation (operation of the preferably LED based emergency lighting modules <NUM>) a smooth transition from the local battery <NUM> to the DC network <NUM> supply is achieved, especially when the local battery status reaches a predefined minimal voltage level of the local battery <NUM> and the emergency lighting means <NUM> are then driven off the central battery.

The emergency driver <NUM> can then demand, via a communication to a central bus manager, to have power assistance from the DC bus.

Therefore, the emergency driver <NUM> has the capability to be powered (during operation of the emergency lighting means <NUM>) from its associated local battery <NUM> but also from the DC network <NUM>. Optionally, it can further have communication capabilities to demand the power assistance from the DC network <NUM>.

As the battery <NUM> starts to run flat, the battery output voltage shall be raised until it matches the network voltage. The lamp or emergency lighting module or load <NUM> shall follow this increase in its input voltage. This implies that the load should have the ability to work with a variety of inputs voltages, including the maximum network voltage.

Once, both the battery output and load are adjusted, the connection shall be established to the network. The load is then supplied by the network, while the network also gets energy from the battery <NUM>. As the battery voltage drops close to low voltage battery cut off, LVBCO, the discharge current reduces in steps as the new battery current increases in steps.

This provides the advantage of transferring the lamp supply smoothly and to continue the emergency operation. Therefore, there is a smooth load transfer of the load from a self-contained battery <NUM> to the DC network system.

<FIG> and <FIG> show a further embodiment of an emergency driver <NUM> for supplying emergency lighting means <NUM>.

In semi-centralized emergency systems, SCEMS, a DC voltage can be maintained in maintained mode and in emergency mode. This voltage can be used to charge the batteries and supply the maintained loads. In emergency mode, this voltage can be used as primary source for loads with no local battery and loads with local batteries, but those same batteries may not meet the duration requirements.

In emergency mode, the DC Bus voltage is maintained by a group of batteries, from the bus manager (a device responsible to secure the maintained mode voltage and manage all the loads and sources connected to the DC Network) or from devices with self-contained batteries, capable of sharing the battery energy.

Self-contained devices will be supplied first by the local battery, before switching to the DC bus.

In <FIG>, a concept of a self-contained emergency driver comprising a local battery supply with remote supply capability is presented.

The driver is separated into four sections, as schematically shown in <FIG> and <FIG>:.

Therefore, advantageously, a secure smooth transition from local battery supply <NUM> to DC network supply, while in emergency mode, is achieved. If this transition is not smoothly secured, light flicker will be visible.

As the local battery <NUM> of the driver <NUM> depletes, the supply of the LED driver <NUM> shall be transferred from the battery <NUM> to the DC network <NUM>. This transfer can be preceded by a communication signal sent by the driver <NUM> to the bus manager informing about the additional load that is about to be transferred to the DC bus. The switches of section <NUM> should be off while the lamp driver 101d is being fully supplied by the local battery <NUM>. The lamp supply can be connected to the main rail of the driver <NUM>. This means that, if an additional switch is used to connect the battery directly to the LED driver <NUM> input to improve efficiency, it should be turned off before the transition to the DC network. Previous to that, the battery DC-DC converter should start discharging the battery, if it was not already guaranteeing supply to the main rail.

The battery DC-DC converter can increase the main railvoltage slow and gradually until it matches the instantaneous DC network voltage. The switches of section <NUM> are then turned on.

In this configuration, the local battery <NUM> of the driver <NUM> is providing energy to the DC network. The local battery <NUM> shall start reducing slow and gradually its discharge current until the battery <NUM> is completely depleted or reaches a pre-defined cut-off level. A synchronization signal might be used to synchronise the reduction of the discharge current with the emergency sources connected to the DC network <NUM>, to ensure the DC network maintains balanced.

Once the local battery <NUM> is completely depleted or reaches a pre-defined cut-off level, it shall stop discharging. The LED driver <NUM> can continue its operation being supplied from the DC network <NUM>.

<FIG> shows an embodiment of a method <NUM> for supplying emergency lighting means <NUM>.

The method <NUM> for supplying emergency lighting means, comprises the steps of:.

This method has the advantage that a secure smooth transition from local battery <NUM> supply to DC network supply, while in emergency, is provided.

All features of all embodiments described, shown and/or claimed herein can be combined with each other.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only and not limitation.

Claim 1:
An emergency driver (<NUM>) for supplying emergency lighting means (<NUM>), wherein the emergency driver (<NUM>) is configured to be powered, during operation of the emergency lighting means (<NUM>), selectively from:
- a local battery (<NUM>) associated to the emergency driver (<NUM>); or
- a DC network (<NUM>) supplying DC power to DC terminals of the driver (<NUM>);
wherein the emergency driver (<NUM>) comprises:
- a first circuitry (<NUM>) configured to charge the local battery (<NUM>) with DC power supplied to the DC terminals; and
- a second circuitry (<NUM>) configured to have the capability to drive the emergency lighting means (<NUM>) from the local battery (<NUM>) and to have the capability to drive the emergency lighting means (<NUM>) from the DC power supplied to the DC terminals, characterized by
- two controlled switches (101b), wherein the switches (101b) are configured to connect or disconnect the driver from the DC network (<NUM>), wherein, if the switches (101b) are turned on, then the local battery (<NUM>) is charged and the emergency lighting means (<NUM>) is supplied by the DC network (<NUM>).