A converter for charging a battery for supplying emergency lighting means

Abstract

A converter 101 for operating emergency lighting means 16, with charging circuitry 19 for charging a battery 18, and control circuitry 23. The method comprises determining an ongoing lifetime or incre

Description

The invention relates to a converter for charging a battery for supplying emergency lighting means, in particular an LED. The invention further relates to a method for charging a battery for supplying emergency lighting means. BACKGROUND OF THE INVENTION Off-line LED drivers or standard LED drivers with AC supply are provided which supply a light generator, such as an LED, in normal mains operation. This means that a converter is preferably configured only for emergency lighting operation, i.e., in the event of a mains voltage / supply voltage (AC voltage) failure. In the latter case, the converter is used to supply the corresponding current paths for the current / voltage supply of the light generator in the emergency light mode with a voltage / current for the operation. In the case of a mains voltage supply, and in the presence of a parallel standard LED driver, the supply by means of the converter for emergency lighting means usually does not take place, however, by the emergency lighting device which comprises the converter. However, it is also possible that the converter for emergency lighting means is also designed to supply the light generator even when the mains voltage / supply voltage is present. The emergency lighting device can have an energy storage device, for example a battery or an accumulator, which is charged starting from the mains voltage via a charging circuitry with a potential separation element, in particular the converter. In prior art, hand held devices and electric vehicles that undergo frequent charge / discharge cycles do use specialized recharge regimes that hold lower battery voltages until predicted usage times. In emergency systems, however, it is not possible to predict a usage time. Existing lithium ion in emergency lighting utilize a static charging regime charging the battery to a maximum capacity / charge voltage, initially and after each duration test function or emergency event. Moreover, the lifetime of lithium ion batteries is limited by holding voltage, temperature and charge / discharge cycles. Temperature and charge / discharge cycles are basic requirements of the end solution but the constant high holding voltage potentially reduces the battery lifetime. Therefore, it is known that the lithium ion batteries loose capacity over the lifetime (operation and charging cycles). Thus, it is an objective of the invention to provide for an improved converter for charging a battery for supplying emergency lighting means. SUMMARY OF THE INVENTION The object of the present invention is achieved by the solution provided in the enclosed independent claims. Advantageous implementations of the present invention are further defined in the dependent claims. According to a first aspect, the invention relates to a converter for operating emergency lighting means, wherein the converter comprises a charging circuitry for charging a battery of the converter and a control circuitry. The control circuitry is configured to determine an ongoing lifetime or increasing number of charging cycles of the battery, control a charging operation of the charging circuit and a discharging of the battery to drive the emergency lighting means via electrical power supplied to output terminals of the converter, control the charging circuitry to charge the battery up to a predefined maximum battery voltage and, then, stop the charging current when a battery voltage sensed by the control circuity reaches the predefined maximum battery voltage, wherein control circuitry adapts the maximum charge voltage to increase with ongoing lifetime or increasing number of charging cycles of the battery. This provides the advantage that the battery lifetime is extended. Moreover, an end of a life flag is available allowing a planned maintenance before the failure of the system. Furthermore, fewer expensive maintenance cycles for the end user reduce expenses and disruption during a battery replacement. In an implementation form of the converter according to the first aspect, the converter is configured to charge the battery, at the beginning of a lifetime of the battery, up to 100% of a predefined charging voltage, and, towards the end of the lifetime of the battery, increase the charging voltage within a predetermined range beyond the 100% rating charging voltage, in particular the range is between 5% and 15% of the rating charging voltage, wherein the beginning and the end of the lifetime of the battery are defined as the time before and after a respective reference time value. In an implementation form of the converter according to the first aspect, the converter is configured to charge the battery, at the beginning of the lifetime of the battery, up to 3.6 V. In an implementation form of the converter according to the first aspect, the charging voltage of the battery towards the end of the lifetime of the battery is comprised between 3.6 V and 4.2 V. In an implementation form of the converter according to the first aspect, the converter is configured to start the charging voltage of the battery with a value below 100% of the predefined charging voltage, at the beginning of the lifetime of the battery, and, towards the end of the lifetime of the battery, increase the charging voltage of the battery to 100% or even above 100%. In an implementation form of the converter according to the first aspect, the converter is a flyback converter. In an implementation form of the converter according to the first aspect, the charging circuitry comprises connections for being supplied with an AC current from a mains. In an implementation form of the converter according to the first aspect, the battery is a lithium ion battery. In an implementation form of the converter according to the first aspect, the control circuitry is a microcontroller, e.g., an integrated circuit IC and / or an ASIC. According to a second aspect, the invention relates to a method for operating emergency lighting means, wherein the method comprises determining an ongoing lifetime or increasing number of charging cycles of a battery, controlling a charging operation of a charging circuit and a discharging of the battery to drive the emergency lighting means via electrical power supplied to output terminals of a converter, controlling the charging circuitry to charge the battery up to a predefined maximum battery voltage and, then, stopping the charging current when a battery voltage sensed by a control circuity reaches the predefined maximum battery voltage, wherein control circuitry adapts the maximum charge voltage to increase with ongoing lifetime or increasing number of charging cycles of the battery. In an implementation form of the method according to the second aspect, the method further comprises charging the battery, at the beginning of a lifetime of the battery, up to 100% of a predefined charging voltage, and, towards the end of the lifetime battery, increasing the charging voltage within a predetermined margin beyond the 100% rating charging voltage, in particular the margin is between 5% and 15% of the rating charging voltage., wherein the beginning and the end of the lifetime of the battery are defined as the time before and after a respective reference time value. In an implementation form of the method according to the second aspect, the method further comprises starting the charging voltage of the battery with a value below 100% of the predefined charging voltage, at the beginning of the lifetime of the battery, and, towards the end of the battery, increasing the charging voltage of the battery to 100% or even above 100%. The method of the second aspect achieves the same advantages as the converter of the first aspect, and may be extended by respective implementation forms as described above for the converter of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in the followings together with the figures. Fig. 1 shows a system comprising a converter for charging a battery for supplying emergency lighting means according to an embodiment of the invention; Fig. 2 shows a system comprising a converter for charging a battery for emergency lighting means according to an embodiment of the invention; Fig. 3 shows a battery invention; according to an embodiment of the Fig. 4 shows a battery invention; according to an embodiment of the Fig. 5 shows a battery invention; and according to an embodiment of the Fig. 6 schematically shows a method for charging a battery for emergency lighting means according to an embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Aspects of the present invention are described herein in the context of converter for charging at least one battery for an emergency lighting means. The present invention is described more fully hereinafter with reference to the accompanying drawings, in which various aspects of the present invention are shown. This invention however may be embodied in many different forms and should not be construed as limited to the various aspects of the present invention presented through this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. The various aspects of the present invention illustrated in the drawings may not be drawn to scale. Rather, the dimensions of the various features may be expanded or reduced for clarity. In addition, some of the drawings may be simplified for clarity. Thus, the drawings may not depict all of the components of a given apparatus. Various aspects of a converter for charging at least one battery for an emergency lighting means will be presented. However, as those skilled in the art will readily appreciate, these aspects may be extended to aspects of converters for charging at least one battery for an emergency lighting means without departing from the invention. 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. It is further understood that the aspect of the present invention might contain integrated circuits that are readily manufacturable using conventional semiconductor technologies, such as complementary metal-oxide semiconductor technology, short "CMOS". In addition, the aspects of the present invention may be implemented with other manufacturing processes for making optical as well as electrical devices. Reference will now be made in detail to implementations of the exemplary aspects as illustrated in the accompanying drawings. The same references signs will be used throughout the drawings and the following detailed descriptions to refer to the same or like parts. FIG. 1 shows a system 100 comprising a converter 101 for charging a battery 18 for supplying an emergency lighting means 16 according to an embodiment of the invention. The converter 101 comprises: a charging circuitry 19 for charging a battery 18 of the converter 101; and a control circuitry 23 configured to: o determine an ongoing lifetime or increasing number of charging cycles of the battery 18; o control a charging operation of the charging circuitry 23 and a discharging of the battery 18 to drive the emergency lighting means 16 via electrical power 13 supplied to output terminals of the converter 101; o control the charging circuitry 19 to charge the battery 18 up to a predefined maximum battery voltage and, then, o stop the charging current when a battery voltage sensed by the control circuity 23 reaches the predefined maximum battery voltage, wherein the control circuitry 23 adapts the maximum charge voltage to increase with ongoing lifetime or increasing number of charging cycles of the battery 18. This provides the advantage that the battery lifetime is extended. Moreover, an end of a life flag is available allowing a planned maintenance before the failure of the system. Furthermore, fewer expensive maintenance cycles for the end user reduce expenses and disruption during a battery replacement. Fig. 2 shows the system 100 comprising the converter 101 for charging the battery 18 for emergency lighting means 16 according to an embodiment of the invention. In this embodiment, the system 100 comprises an emergency lighting device 10, which is divided into three areas A, B, C, each of which is separated from one another by a safety extralow voltage (SELV) isolation barrier Ila, 11b. An LED driver 12 for mains operation is referred to in Fig. 2 as an "offline" LED driver 12 or as a standard LED driver 12 that can feed the LED when an AC supply 13 is present. From Fig. 2, it can be seen that a first current path from the mains supply source 13 via a mains switch 14, a first relay 15a, the LED driver 12 for mains operation and a second relay 15b, leads to the light generator 16, wherein the light generator 16 can comprise LEDs. This current path partly leads through the emergency lighting device 10 (illustrated in areas A and C in which the first and second relays 15a, 15b are arranged). In an embodiment, the first relay 15a and the second relay 15b are set up to switch the load or the illuminant or light generator 16 from the standard LED driver 12 for mains operation to an emergency LED driver 17 if the mains voltage fails, or if the mains voltage moves out of a predetermined range, or a predetermined threshold value is exceeded or undershot. In this embodiment, it is also shown that the battery 18 is charged by the mains voltage 13 via the charging circuitry 19 in normal operation. The battery 18, then, supplies the emergency LED driver 17 in emergency lighting mode, which, in turn, supplies the illuminant 16 with current via the second relay 15b. In Fig. 2, it is also shown that, in an embodiment, the battery 18 is separated from the illuminant 16 by a safety extra-low voltage insulation barrier 11b. However, in another embodiment, the battery may or may not be isolated from the output depending on the implementation. In an alternative embodiment, it is possible to dispense with a standard LED driver 12 for mains operation and the emergency LED driver 17 also takes over the operation and supply of the illuminant 16 when the mains voltage is present. In this case, the emergency lighting device 10 would be designed as a so-called combination device, which can operate the illuminant 16 when the mains voltage is present and also when the mains voltage fails. In this case, the relays 15a and 15b can be omitted. In an embodiment, the converter 101 is a flyback converter, i.e., a converter with a clocked circuit breaker, via which the battery 18 is supplied, when the mains voltage is applied, i.e., in normal operation. Fig. 2 also shows the control circuit 23 according to an embodiment, which, based on the voltage / current transmitted by the charging circuitry 19 of the converter 101, ascertains directly or indirectly whether an emergency lighting operation is present. The control circuit 23 can, therefore, indirectly or directly detect the mains voltage 13 (for example, by measuring the voltage on the secondary side of the converter 101) and, thus, also a failure of the mains voltage 13 or a deviation of the mains voltage 13 from a predetermined value a predetermined interval. The control circuit 23 can also control the power, the current and / or the voltage with which the illuminant 16 is supplied in the emergency light mode. The control circuit 23 can detect and regulate the current emitted by the battery 18, or the emitted voltage. Preferably, the control circuit 23 controls the current emitted by the battery 18, or the emitted voltage or power or also the power, the current and / or the voltage with which the illuminant 16 is supplied in the emergency light mode by means of the activation of an actively controlled switch in a second converter (not shown in the embodiment of Fig. 2). Further information from further modules of the emergency lighting device (for example, from a test switch for initiating a test mode, from an access for setting the emergency lighting duration and / or from a sleep mode interface are also possible) can be received, and processed by the control circuit 23. The access for setting the emergency lighting period can preferably be used to specify the duration of the emergency lighting period. For example, the emergency lighting device 10 can alternatively be set for an emergency lighting duration of one hour or three hours. This setting can depend on the connected battery 18 or on local specifications. A sleep mode can be signaled to the emergency lighting device 10 by means of a sleep mode interface. For example, it can be provided that the complete lighting is put into a sleep mode and, thus, the energy supply is switched off. The control circuit 23 can be implemented by a microcontroller, e.g., an integrated circuit IC and / or an ASIC. Fig. 3 shows a battery 18 according to an embodiment of the invention. In this embodiment, the battery 18 is initially charged for 24 hours. Then, the full discharge of the battery 18 takes place, noting the battery voltage / capacity at the rated duration time, and the time to discharge the battery completely. Then, the spare capacity is established, and the battery is recharged to the full capacity minus the spare capacity and only hold at that established battery voltage, as schematically shown in Fig. 3. As the battery 18 ages on subsequent duration test cycles, this voltage should be increased as the total battery capacity reduces, as schematically shown in Fig. 4. Typically, a maximum holding battery voltage occurs at 3.6 V, but the battery is charged beyond this voltage as far as 4.2 V (or as far as the battery safety circuit allows). When the charge regime has increased to a holding charge of 3.6 V, this is the end of the battery certificate lifetime, but the battery 18 still has useful capacity if the battery holding voltage is increased beyond 3.6 V. This end of life capacity can be used to get a full duration and flag for a maintenance. In an embodiment, it is also be possible to build in extra 5 battery capacity with the intention of reducing a maintenance cycle . Fig. 6 schematically shows a method 600 for charging a battery 18 for emergency lighting means 16 according to an embodiment 10 of the invention. The method 600 comprises the steps of: determining 601 an ongoing lifetime or increasing 15 number of charging cycles of a battery 18; controlling 602 a charging operation of a charging circuitry 19 and a discharging of the battery 18 to drive the emergency lighting means 16 via electrical 20 power 13 supplied to output terminals of a converter 101; controlling 603 the charging circuitry 19 to charge the battery 18 up to a predefined maximum battery voltage 25 and, then, stopping 604 the charging current when a battery voltage sensed by a control circuity 23 reaches the predefined maximum battery voltage, wherein the control 30 circuitry 23 adapts the maximum charge voltage to increase with ongoing lifetime or increasing number of charging cycles of the battery 18. 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. Numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit of scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the abovedescribed embodiments. Rather, the scope of the invention should be defined in accordance with the following claims and their equivalence. Although the invention has been illustrated and described with respect to one or more implementations, equivalent alternations and modifications will occur to those skilled in the art upon the reading of the understanding of the specification and the annexed drawings. In addition, while a particular feature of the invention may have been disclosed with respect to only of the several implementations, such features may be combined with one or more other features of the other implementations as may be desired and advantage for any given or particular application.

Claims

l.A converter (101) for operating emergency lighting means (16), wherein the converter (101) comprises:a charging circuitry (19) for charging a battery (18) of the converter (101);a control circuitry (23) configured to:o determine an ongoing lifetime or increasing number of charging cycles of the battery (18);o control a charging operation of the charging circuitry (23) and a discharging of the battery (18) to drive the emergency lighting means (16) via electrical power (13) supplied to output terminals of the converter (101);o control the charging circuitry (19) to charge the battery (18) up to a predefined maximum battery voltage and, then,o stop the charging current when a battery voltage sensed by the control circuity (23) reaches the predefined maximum battery voltage, wherein the control circuitry (23) adapts the maximum charge voltage to increase with ongoing lifetime or increasing number of charging cycles of the battery (18).

2. The converter (101) of claim 1, wherein the converter (101) is configured to:charge the battery (18), at the beginning of a lifetime of the battery (18), up to 100% of a predefined charging voltage, and,towards the end of the lifetime of the battery (18), increase the charging voltage within a predetermined range beyond the 100% rating charging voltage, in particular the range is between 5% and 15% of the rating charging voltage, wherein the beginning and the end of the lifetime of the battery (18) are defined as the time before and after a respective reference time value.

3. The converter (101) of claim 2, wherein the converter (101) is configured to charge the battery (18), at the beginning of the lifetime of the battery (18), up to 3.6 V.

4. The converter (101) of claim 2 or 3, wherein the charging voltage of the battery (18) towards the end of the lifetime of the battery (18) is comprised between 3.6 V and 4.2 V.

5. The converter (101) of any one of the preceding claims, wherein the converter (101) is configured to:start the charging voltage of the battery (18) with a value below 100% of the predefined charging voltage, at the beginning of the lifetime of the battery (18), and, towards the end of the lifetime of the battery (18) , increase the charging voltage of the battery (18) to 100% or even above 100%.

6. The converter (101) of any one of the preceding claims, wherein the converter (101) is a flyback converter.

7. The converter (101) of any one of the preceding claims, wherein the charging circuitry (19) comprises connections for being supplied with an AC current from a mains (13).

8. The converter (101) of any one of the preceding claims,wherein the battery (18) is a lithium ion battery.

9. The converter (101) of any one of the preceding claims, wherein the control circuitry (23) is a microcontroller, e.g., an integrated circuit IC and / or an ASIC.

10. A method (600) for operating emergency lighting means(16), wherein the method (600) comprises:determining (601) an ongoing lifetime or increasing number of charging cycles of a battery (18);controlling (602) a charging operation of a charging circuitry (19) and a discharging of the battery (18) to drive the emergency lighting means (16) via electrical power supplied to output terminals of a converter (101) ;controlling (603) a charging circuitry to charge the battery (18) up to a predefined maximum battery voltage and, then,stopping (604) the charging current when a battery voltage sensed by a control circuity (23) reaches the predefined maximum battery voltage, wherein the control circuitry (23) adapts the maximum charge voltage to increase with ongoing lifetime or increasing number of charging cycles of the battery (18).

11. The method (600) of claim 10, wherein the method (600) further comprises:charging the battery (18), at the beginning of a lifetime of the battery (18), up to 100% of a predefined charging voltage; and, towards the end of the lifetime battery (18), increasing the charging voltage within a predetermined margin beyond the 100% rating charging voltage, in particular the margin is between 5% and 15% of the rating charging voltage., wherein the beginning and the end of the lifetime of the battery (18) are defined as the time before and after a respective reference time value.

12. The method (600) of claim 10 or 11, wherein the method (600) further comprises:starting the charging voltage of the battery (18) with a value below 100% of the predefined charging voltage, at the beginning of the lifetime of the battery (18), and,towards the end of the file of the battery (18), increasing the charging voltage of the battery (18) to 100% or even above 100%.

Images