Description :

The invention is in the field of emergency lighting devices and power supply of emergency lighting devices. In particular, the invention relates to an emergency converter and a method capable of detecting the type of an energy storage device connected to the emergency converter.

In emergency light systems, converter devices (converters, ballasts, driver devices) are used for providing a supply voltage to an emergency light for a predetermined time in case mains supply fails. The voltage supply is maintained in case of a mains supply failure for a rated service time using energy stored in an energy storage device such as a rechargeable battery. The rated service time defines a battery discharge duration during which time the emergency converter is required to drive the emergency light with a predetermined drive current. The maximum possible discharge duration depends on the emergency light and the capacity of the rechargeable battery.

Different energy storage devices are used depending on the application and local applicable regulations, wherein the energy storage devices may differ with regard to the capacity, presence of protection circuits and/ or sensors, employed battery chemistry and/ or nominal voltage. Some of these technical specifications have an impact on operations controlled by the emergency converter, such as failure handling, charging and discharging.

Emergency converters may be designed for exclusive use with a given type of energy storage device. However, this increases the number of variants for a manufacturer, and restricts a user of an emergency lighting system to a specific type of energy storage device. Alternatively, the emergency converter can be configured to connect to and reliably operate with energy storage devices of various types.

EP 3 563 640 At discloses a method, in which the type of an energy storage device connected to an emergency converter is automatically detected and energy storage management parameters are set according to the detected type, wherein the emergency converter determines whether the energy storage device comprises a temperature sensor, whether the resistance value of the temperature sensor is greater than a threshold and sets first, second or third charging parameters based on the absence of the temperature sensor and the resistance value. However, the number of types is limited and the resistance value depends on the temperature of the energy storage device. Further, the type of temperature sensor depends on the type of the energy storage device.

It is an object of the present invention to provide an apparatus and a method, which reduce the above problems. In particular, an object of the present invention is to provide an emergency converter, an energy storage device and a method that allow to use different types of energy storage devices with low efforts and costs.

This object is achieved by an emergency converter, an energy storage device and a method according to the enclosed independent claims. Advantageous features of the present invention are defined in the corresponding dependent claims.

According to the present invention, an emergency converter comprises an energy storage interface configured to connect an energy storage device to the emergency converter and a control circuit configured to determine the type of energy storage device connected by the energy storage interface. The energy storage interface is configured to connect to energy storage devices of at least two different types to which different parameters for controlling the emergency converter are assigned, wherein the energy storage interface comprises a sensor connector to connect to a sensor circuit of the energy storage device comprising a temperature sensor for generating a temperature signal indicating a temperature of the storage devices and at least a resistor for generating a type signal indicating the type of the storage devices. The type signal is generated in a first period and the temperature signal is generated in a second period following the first period. The control circuit is configured to detect, in the first period, the type signal received by the sensor connector, to determine the type of energy storage device connected by the energy storage interface based on the detected type signal and to set at least one parameter assigned to the determined type.

Since the type signal and the temperature signal are generated/ detected at different times, the number of connectors/ pins of the energy storage interface can be reduced and the type of the energy storage device can be determined very precisely and reliably even if a plurality of different resistors are assigned to a plurality of types.

The sensor circuit can be powered/ controlled by the emergency converter, wherein a current source of the emergency converter outputs a current to the sensor connector and the control circuit determines the type of the energy storage device by measuring the voltage at the sensor connector and by assigning one of the at least two different types to a voltage value measured at a predetermined time after the current is output to the sensor connector or to at least one predetermined characteristic of a voltage waveform measured in a predetermined time interval after the current is output to the sensor connector.

The emergency converter can be configured to merely detect the type signal and to not use/ detect the temperature signal. Alternatively, the control circuit is configured to detect, in the second period, the temperature signal received by the sensor connector, to control charging and/ or discharging of the energy storage device based on the detect temperature signal and/ or to generate a warning signal when a temperature indicated by the temperature signal exceeds an upper threshold value and/ or to generate the warning signal when the temperature lies below the lower threshold value.

The sensor circuit can generate an offset of the temperature signal that depends on the different resistors assigned to the different types. As the type is determined in the first period, the offset/ error can be corrected in the second period, wherein the control circuit determines and corrects the error of the temperature signal based on the determine type and a table assigning an error or a correction value/ function to each of at least two different types.

The types of energy storage devices may differ with regard to the charging capacity, presence of protection circuits, the battery chemistry and/ or nominal voltage and the at least one parameter can include at least one of charging parameters, discharging parameters and failure parameters.

The emergency converter can comprise a LED driver that is configured to supply a current to a LED lighting device and that is powered by the energy storage device in an emergency lighting mode or a test mode.

According to the present invention, an energy storage device comprises connectors configured to connect the energy storage device to an energy storage interface of an emergency converter and a sensor circuit having a temperature sensor configured to generate a temperature signal indicating a temperature of the storage devices and at least a resistor for generating a type signal indicating the type of the storage devices, wherein the circuit is connected to the connectors and is configured to generate the type signal in a first period and the temperature signal in a second period following the first period.

The sensor circuit can comprise a switch configured to switch-off the temperature sensor during the first period. In addition, the resistor and the temperature sensor can be connected in series between two of the connectors, wherein the temperature sensor is bypassed/ short-circuited by the switch during the first period.

The signal to switch-off the temperature sensor can be generated by the sensor circuit when a current/ voltage is supplied to the two connectors, wherein the sensor circuit comprises a capacitor, a voltage divider connected in series between the two connectors, and the switch is controlled by a signal generated by the voltage divider. In this way, the time (first period) at which the temperature sensor is bypassed depends on the capacitor and the voltage divider. Alternatively, the switch can be controlled by a separate controlling means, such as microcontroller or application specific integrated circuit (ASIC).

The energy storage device can comprise a Lithium-ion battery, wherein the temperature sensor is configured to generate the temperature signal indicating a temperature of the Lithium-ion battery. The temperature sensor can comprise a thermistor, in particular, NTC or PTC resistor.

According to a preferred embodiment, the Lithium-ion battery is connected or connectable (by the controlling means) in parallel to first and second connectors for charging/ discharging the battery, wherein the sensor circuit is connected in parallel to a third connector of the connectors and one of the first connector and the second connector. Thus only one additional connecter is necessary for transmitting the temperature signal and type signal.

According to the present invention, a method for determining a type of an energy storage device connected to an emergency converter comprises the steps of detecting a signal generated by the energy storage device and determining the type of energy storage device based on the detected signal, wherein at least two different types of energy storage devices, to which different parameters for controlling the emergency converter are assigned, can be connected to the emergency converter. The signal is generated by a sensor circuit of the energy storage device comprising a temperature sensor for generating a temperature signal indicating a temperature of the storage device and at least a resistor for generating a type signal indicating the type of the storage devices. The type signal is generated in a first period and the temperature signal is generated in a second period following the first period, wherein in the detecting step, the type signal is detected in the first period and in the determining step, the type of energy storage device is determined based on the type signal. In the detecting step, a current can be supplied by the emergency converter to the sensor circuit of the energy storage device, wherein in the determining step, the type of the energy storage device is determined by measuring voltage at the sensor circuit and by assigning one of the at least two different types to a voltage value measured at a predetermined time after the current is supplied to the sensor circuit or to at least one predetermined characteristic of a voltage waveform measured in a predetermined time interval after the current is supplied to the sensor circuit.

The resistor and the temperature sensor can be connected in series, wherein in the detecting step, the temperature sensor is bypassed by a switch connected in parallel to the temperature sensor.

Embodiments of the invention are discussed in detail with reference to the enclosed figures, in which

Fig. 1 shows a simplified block diagram of parts of an emergency light system with an energy storage device and an emergency converter according to an embodiment,

Fig. 2 shows the sensor circuit of the energy storage device and the current generating circuit of the emergency converter shown in Fig. 1,

Fig. 3 shows a diagram of signals indicating different types of energy storage devices,

Fig. 4 shows a table for determining the type of energy storage device connected to the emergency converter shown in Fig. 1, and

Fig. 5 shows a flowchart for a method for determining the type of energy storage device connected to the emergency converter according to an embodiment.

In the figures, all voltages are based on a common reference potential (GND) and same reference numbers denote same or equivalent structures. The explanation of structures with same reference numbers in different figures is avoided where deemed possible for sake of conciseness.

Fig. 1 shows an emergency lighting system with an energy storage device 1, an emergency converter 2 detachably connected to the energy storage device 1 and a FED lighting device 3 detachably connected to the emergency converter 2 according to an embodiment. The parts shown in Fig. 1 can be housed in an emergency light.

The emergency converter 2 comprises a charger/ discharger circuitry 4, a control circuit 5 for controlling the charger/ discharger circuitry 4, a memory 6 storing charging, discharging and failure parameters and information (table) for determining the type of the energy storage device 1, an energy storage interface 7, a light device interface 8 and a LED driver 9 for generating a LED drive current, which is output via light device interface 8 to the LED lighting device 3. The LED lighting device 3 fed with the LED light current emits light from one or more LEDs.

The emergency converter 2 is fed from mains supply (not shown) in case of normal operations when mains supply is available. In case of a mains failure, malfunction or functional test, the emergency converter 2 is provided with electric energy from the energy storage device 1 via the charger/ discharger circuitry 4. For the invention the structure of the charger/ discharger circuitry 4, the LED driver 9, the light device interface 8 and the LED lighting device 3 are not essential for understanding the invention and may be of any known structure used in conjunction with emergency converters 2 for emergency lighting applications. The charger/ discharger circuitry 4 must only be capable to adapt its settings or to operate based on an input signal of the control circuit 5.

Emergency lighting and standard lighting may for example share components. For example, the same LED lighting device 3 or the same LED driver 9 may be used for a conventional lighting mode as well as for the emergency lighting mode (maintained lighting mode).

The energy storage interface 7 and the energy storage device 1 are connected by two power supply lines and a sensor line, wherein the energy storage interface 7 comprises two electrical connectors 7.2, 7.3 for connecting the power supply lines, shown in Fig. 1 as a first positive connecting line (+) and a second negative connecting line (-), and an electrical connector 7.1 for connecting the sensor line.

The energy storage device 1 comprises an interface 10 for connecting the power supply lines and the sensor line, a Lithium-ion battery 11 formed of a plurality of cells, an integrated circuit (IC) 12, a protecting/ switching circuit 13 controlled by the integrated circuit (IC) 12 and a sensor circuit 14 for detecting the temperature of the Lithium-ion battery 11. The protecting/ switching circuit 13 and the integrated circuit (IC) 12 are optional, wherein the integrated circuit (IC) 12 is configured to detect short-circuit, over-charge and/ or over-discharge and to control the protecting/ switching circuit 13 to disconnect/protect the Lithium-ion battery 11 when short- circuit, over-charge and/ or over-discharge is detected.

The power supply lines connect an electrical connector 3.2 of the interface 10 to the electrical connector 7.2 and an electrical connector 3.3 of the interface 10 to the electrical connector 7.3 and the sensor line connects an electrical connector 3.1 of the interface 10 to the electrical connector 7.1. The electrical connectors 3.1., 3.2 and 3.3 of the interface 10 and/ or the electrical connectors 7.1, 7.2 and 7.3 of the energy storage interface 7 can be screw or spring terminals, to which the sensor line and the power supply lines are connectable. Alternatively, the lines may be soldered to the interface 10 and/ or the energy storage interface 7.

The emergency converter 2 can be operated with different energy storage devices 1, which differ in their charging capacity. The capacity of the energy storage device 1 connected to the energy storage interface 7 is determined based on a type signal generated by the sensor circuit 14. The emergency converter 2 comprises a current generating circuit 15 to supply a current to the sensor circuit 14 based on which the sensor circuit 14 generates the type signal.

Fig. 2 shows the sensor circuit 14 and the current generating circuit 15 connected by the negative connecting line (GND) and the sensor line. The current generating circuit 15 generates a current ii by a non-ideal current source formed of a voltage source (supply voltage UDD) in series with a resistor Ri, supplies the current ii to the sensor circuit 14 via the electrical connector 7.1 and outputs a signal (voltage UT) that is generated by the sensor circuit 14 and received via the electrical connectors 7.1 to the control circuit 5. The control circuit 5 controls the generation of the current ii, wherein the current generating circuit 15 comprises a switch Mi in series with the resistor Ri, which is controlled by a signal Us generated by the control circuit 5.

The sensor circuit 14 comprises a resistor RBC and a resistor RNTC connected in series to the electrical connectors 3.1 and 3.2, a switch Qi connected in parallel to the resistor RNTC and a circuit that is formed by a capacitor Ci, a resistor R3 _, a resistor R4 and an optional capacitor C2. The circuit is configured to turn the switch Qi on and off at predetermined times after the current ii is supplied to the sensor circuit 14. The switch Qi is a transistor, wherein the capacitor Ci and the resistor R3 are connected in series to the electrical connector 3.1 and the base of the transistor, the capacitor C2 and the resistor R4 are connected in parallel to the base of the transistor and the electrical connector 3.2, the collector is connected to a circuit point (U _QI ) between the resistor RBC and the resistor RNTC and the emitter is connected to the electrical connector 3.2. The resistor R _NTC is a temperature sensor positioned in the energy storage device 1 to detect the temperature of the Lithium-ion battery 11 (not shown in Fig. 2), wherein the resistance value of the resistor R _NTC decreases with increasing temperature. The resistor R _BC is selected to indicate the type of the energy storage device 1, wherein the resistance value of the resistor R _BC is assigned to the battery capacity of the Lithium-ion battery 11. At the time the switch Qi is off, the type signal generated by resistor R _BC is superimposed on the temperature signal generated by the resistor R _NTC SO that voltage U _T depends on the temperature and the type of the energy storage device 1. In order to generate and detect the type signal only, the switch Qi bypasses the resistor R _NTC at a limited period and the control circuit 5 detects the type signal in this period after the switch Ml has been turned on.

The control circuit 5 turns on the switch Ml at each time the energy storage device 1 is connected to the emergency converter 2, and/ or the emergency converter 2 is connected to the mains supply. When the switch Ml is turned on, current L flows through the circuit formed by the capacitor Ci, the resistor R3 _, the resistor R4 and the optional capacitor C2. This produces a voltage across the resistor R ₄ , which drives the base-emitter junction of the switch Qi (transistor) so that the switch Qi turns on. As the current 13 through the capacitor Ci decays exponentially, the switch Ml is turned off. The capacitor Ci, the resistor R3 and the resistor R4 are dimensioned so that the switch Qi turns on, for example, at least 150ms. The capacitor C2 causes an optional switch-on delay.

The voltage U _T produced at the connector 3.1 (temperature sense pin of the energy storage device 1) is a function of the resistors Ri and R _BC and the time constant governed by the circuit formed by the capacitors Ci and C2 and the resistors R ₃ and R ₄ .

Fig. 3 shows in a diagram the waveforms of voltage U _T for different values of the resistor R _BC and the values of voltage U _QI across the switch Qi to judge the time for which the switch Qi remains on. In Fig. 3, one of five different values 7.5K, 10 K, 15K, 22K and 39K is selected for the resistor R _BC to indicated one of the five different values of battery capacities 1 x 1.5Ahr, 2 x 1.5Ahr, 3 x 1.5Ahr, 4 x 1.5 Ahr and 5 x 1.5Ahr. Alternatively or in addition, the presence of protection circuits (the integrated circuit 12 and the protecting/ switching circuit 13) and/ or type of temperature sensor (NTC or PTC), employed battery chemistry and/ or nominal voltage can be indicated by the different values of the resistor R _BC - AS shown in Fig. 3, the voltage U _T produced at the connector 3.1 rises exponentially, the control circuit 5 takes a sample of the voltage U _T (dashed line) 100ms after the switch Mi was turned on by the control circuit 5, assigns the sample to one of the resistor values based on a table shown in Fig. 4. In the table shown in Fig. 4, voltage level window with +/ -48mV margin around the nominal value is defined for each value of the resistor R _BC and the control circuit 5 assigns a sample of, for example, 1,3 V to the nominal value of 1,34 IV and the resistor value of 7,5K and sets the charging, discharging and/ or failure parameters assigned to the nominal value of 1,341V or the resistor value of 7,5K. Since, the nominal values and the resistor values are not relevant for the parameters to be set by the control circuit 5, the table can directly assign the respective parameters to each voltage level window. The table can be stored in the memory 6.

As time progresses (first period), a steady state is reached when the value of current L reaches zero and switch Qi turns off. Steady state is reached approximately at 1,5 seconds after switch Mi was turned on. At this stage switch Qi is off, the voltage UT at the connector 3.1 is a function of resistors Ri, RBC and RNTC and the control circuit 5 can determine the temperature of the Lithium-ion battery 11 based of the detected voltage UT (temperature signal) as a continuous battery temperature monitor.

When the resistor RBC is determined based on the table shown in Fig. 4, influence of the resistor RBC on the temperature signal can be determined and eliminated. Alternatively, the resistor RBC can be bypassed by another switch Qi after the value of the resistor RBC or the nominal voltage is determined, or a compensation resistor Rc can be added in series to the resistor RNTC, wherein the compensation resistor Rc and the resistor RNTC are bypassed by the switch Qi and the value of the compensation resistor Rc is designed so that the sums of the compensation resistor Rc and the resistor RBC always result in a constant value independent on the value of the resistor RBC assigned to the respective type, e.g.: R = 39K - RBC or R = R _B C_m _X - RBC-

The control circuit 5 and/ or the integrated circuit 12 can be a microcontroller or application specific integrated circuit (ASIC). The energy storage device 1 can be a Li-ion cell type energy storage device or a NiMH cell type energy storage device. The memory 6 can store two or more sets of energy storage management parameters, each associated with at least one type of energy storage device 1 and the control circuit 5 can control the charger/ discharger circuitry 4 to read, from the memory 6, the set assigned to the determined type of energy storage device 1 or controls the charger/ discharger circuitry 4 based on the set of parameters.

The energy storage management parameters may include charging parameters such as a load current, a load voltage, different voltage or current levels. The energy storage management parameters may include selecting a suitable battery management algorithm, for example constant current algorithm, permanent or intermittent charge algorithm or permanent or intermittent charge and constant current followed by a constant voltage particularly suitable Li-ion cell chemistry.

The energy storage management parameter may include selecting a suitable charging methodology, for example charge termination or charge reduction based upon a timed algorithm such as NiCd. In case of NiMH, charging reduction based on a negative dV / dt may be set as energy storage parameter with respect to the charge methodology. In Li-ion type cells chemistry, voltage charging termination may be set as charging methodology.

The energy storage management parameters may include selecting a suitable discharge current, for example a higher discharge current for the mostly in parallel connected Li-ion cells instead of the NiCd or NiMH cells usually arranged in series.

The energy storage management parameters may include failure parameters and thresholds in dependence of the respective type of energy storage device 1 and its cell chemistry. The energy storage management parameters may include in this respect at least one of a gassing voltage level threshold, an open circuit battery threshold and a minimum battery voltage level for a fully charged energy storage device 1.

The energy storage management parameters may include end of charge limit, in particular a low voltage battery cut off limit (LVBCO) in dependence of the respective type of energy storage device 1.

The energy storage management parameters may enable an energy storage device communication function for communicating with the LED converter 9, in particular in case of a Li-ion type energy storage device 1 which may include an integrated circuit for implementing some battery pack intelligence functions.

The energy storage management parameters may include a pre-recorded parameter set applicable to the specific energy storage device 1 with its determined cell chemistry.

Fig. 5 shows a very simplistic flowchart showing the single steps performed by the method described in detail above. In step St, the current generating circuit 15 generates the current L and supplies the current L to the sensor circuit 14 via the electrical connectors 7.1. In step S2, the type signal (voltage U _T ) is generated by the sensor circuit 14 and output to the control circui5 via the electrical connectors 7.1.

The control circuit 5 detects the type signal at a predetermined time after the current ii is supplied to the sensor circuit 14 in step S3 and determines the type of energy storage device 1 based on the type signal in step S4. The method of Fig. 5 is run every time an energy storage device 1 is connected to the emergency converter 2 and/ or the emergency converter 2 is connected/ switched to mains supply.