ES2357537T3 - POWER SUPPLY FOR A CONTROL UNIT OF AN EMERGENCY LIGHTING EQUIPMENT. - Google Patents

Abstract

Emergency lighting equipment (1) comprising: - a battery (4) - a charging circuit (3) powered by mains voltage for the battery (4) - an exciter circuit (5) connected to the battery ( 4) for a light source (LEDF) in the form of a regulator with a switch (S2) characterized in that the switch (S2) is controlled from an integrated digital control unit (2), also presenting a circuit for monitoring switches (20) independent of the control unit (2) that records the state in which the switch (S2) remains permanently closed due to a malfunction of the control unit (2).

Description

[0001] The present invention relates to circuits for the operation of light emitting diodes.

[0002] Although the present invention is described with reference to emergency lighting equipment with LED’s, it should be understood that the invention is generally related to LED’s service connections.

[0003] The emergency lighting equipment of the generic type therefore has, as a central element, a unit for the accumulation of energy, especially a battery or an accumulator, which is charged during normal or charging service through the general voltage supply network. For this process, a charging circuit is provided that is connected from the input side to the supply voltage of the network and that throughout the charging service permanently contributes energy to the energy accumulation unit that it accumulates. Only in case of emergence of an emergency state, which these devices detect as a rule automatically thanks to a network supply voltage control system, is it switched to an emergency lighting service in which it is activated and used the emergency light source for which it is used, if necessary, the energy provided by the energy accumulation unit. Since the accumulation capacity of the energy accumulation unit has, of course, its limits are preferably used light sources with a relatively low energy consumption. For this reason, emergency lighting equipment is preferably equipped with gas discharge lamps, especially fluorescent tubes. However, more and more light sources are also used in the form of semiconductors that emit light, in particular LEDs, since these light sources also have a high degree of efficiency and allow energy saving in their use.

[0004] From EP 1 202 428 A1, emergency lighting equipment is known which has the characteristics of the preamble of claim 1.

[0005] From US 2001/054877 A1 it is known in the field of electric or hybrid vehicles the possibility of mounting a switch in a charging circuit for a battery pack for an electric vehicle.

[0006] The present invention is based on the task of proposing a circuit with an improved power supply of a control unit of an emergency lighting equipment.

[0007] A first aspect relates to emergency lighting equipment comprising

- A battery,

- an exciter circuit for a light source in the form of a switching regulator with a switch that is controlled from an integrated digital control unit that has a switch monitoring circuit independent of the control unit or that records the status in which the switch remains permanently closed due to a malfunction of the control unit.

[0008] The circuit breaker monitoring circuit may disconnect the control unit or cause a reset process.

[0009] Before switching off or resetting, it is possible to archive the service data of the control unit in a memory.

[0010] The invention will now be explained in greater detail in view of the attached drawing. It looks on the:

Fig. 1 a schematic view of the wiring diagram of a first embodiment of the emergency light equipment according to the invention;

Fig. 2 a second exemplary embodiment of an emergency light equipment;

Fig. 3 a graph to determine the supply voltage of the network based on service parameters measured by the output side of the load circuit;

Fig. 4 another graph to check the secondary power of the load circuit considered for the direct determination of the power of the light source;

Fig. 5 an illustration of a battery circuit according to the invention; [0011] The emergency light equipment represented in simplified form in fig. 1 and generally identified with reference 1 is provided in the exemplary embodiment shown for the operation of an LED as an emergency light source. The emergency light equipment 1 is connected on the input side to a voltage supply network that provides a supply voltage of the network Uin, and has as an essential component a control unit 2, a charging circuit 3, a energy accumulation unit 4 in the form of a battery or accumulator as well as an exciter circuit 5.

Fig. 6

a circuit of LED exciters according to the invention;

Fig. 7

the exciter control as well as the resulting diode current and

Fig. 8

details of the power supply of a microcontroller.

[0012] The load circuit 3 consists of the first embodiment shown in a flyback converter provided, on the one hand, with a transformer T with a primary winding n1 and a secondary winding n2 as well as, on the other hand, with a switch controllable S1. As is known, by opening and closing the switch S1 alternatively the energy provided by the supply voltage of the network Uin can be transferred to the secondary side of the flyback converter 3 and used to charge the energy storage unit 4. The transfer of Power is produced in the open state of switch S1 for which a diode D1 is provided on the output side of flyback converter 3. Flyback circuits of this type are often used frequently in such emergency light equipment thanks to their simple structure and reliable operation.

[0013] The activation of the controllable switch S1 is carried out through the control unit 2 of the emergency light equipment, the drive being produced especially with galvanic separation through an optical coupler 6. In this process the control unit 2 activates switch S1 alternately, calculating the so-called duty cycle D1 for the connection of switch S1 as follows:

D1 = ton1 / (T-ton1)

Corresponding ton1 to the switch connection time while T defines the total time of a complete switch cycle of the switch S1.

[0014] It is also possible that in the case of the activation of S1 it is a "self oscillator" and that the optical coupler 6 influences the proper frequency of the "self oscillator" throughout the duty cycle.

[0015] During a charging service of the emergency light equipment 1, only the charging circuit 3 is usually active to permanently charge the battery 4. Only in the event that an emergency state occurs, especially characterized by difference Between the supply voltage of the network Uin and the previously determined theoretical values, an emergency light service is started in which the exciter circuit 5 is used to activate the LED. The exciter circuit 5 designed as a regulator has for this purpose another controllable switch S2, an inductivity L as well as a diode D2. Alternately activating the switch S2 by means of the control unit 2 provides the LED with a current through which it enters into operation. The pulse ratio with which the switch S2 is activated through the control unit 2 can be varied in order to regulate the intensity of the current provided to the LED and, consequently, the power at which the LED operates. In this way, it is possible to ensure in a very elegant way that the LED works and provides a constant brightness despite possible oscillations in the battery power.

[0016] A function of the emergency light equipment 1 therefore consists in detecting, by means of the evaluation of the supply voltage of the network Uin, if there is an emergency state to activate an emergency light service in its case. emergency. Until now, the value of the input voltage Uin for the load circuit 3 was directly determined, which in any case, for the reasons mentioned above, entailed its drawbacks.

[0017] In this case, the direct measurement of the supply voltage of the Uin network can be waived. Instead, it is considered to determine the voltage indirectly, provided that only the magnitudes of the service parameters of the emergency light equipment 1 are measured on the secondary side of the load circuit 3.

[0018] In the first embodiment according to Figure 1, the voltage Uf1b1 is measured on the secondary side of the converter with a blocking oscillator or a flyback converter 3 for which no galvanic separation is necessary since this magnitude has the same potential of reference than the control unit 2 that evaluates this measurement value. Once the secondary voltage Uf1b2 is known, it is possible, based on this value, to draw conclusions about the input voltage Uin. And, with the switch S1 of the flyback converter 3 activated, there is a relationship between the input voltage Uin and the secondary voltage Uf1b2 which depends in particular on the transformation ratio between the two coils n1 and n2 of the transformer T as well as the switch duty cycle D1. This relationship between the secondary voltage Uf1b2 simply to be measured and the input voltage Uin to be monitored has now been stored in the form of a table of values in the control unit 2, so that, after measuring the secondary voltage Uf1b2, it can determine easily the value of the input voltage Uin, without having to measure it directly. If the control unit 2 verifies that the determined input voltage Uin exceeds certain theoretical value limits, it understands that there is an emergency state, and this circumstance in turn causes the control unit 2 to activate the emergency service.

[0019] Accordingly, the described solution allows a very simple and at the same time effective control of the state of the general current supply. A special advantage of the embodiment shown in FIG. 1 is also that the intensity of the input voltage Uin can be determined regardless of whether the emergency light LED is connected or not. As a consequence of its blocking effect, the diode D1 causes precisely a separation between the secondary voltage Uf1b2 and the battery voltage Ubat, so that the activity of the exciter circuit 3 does not influence the process described above for determining the voltage of the Uin entry

[0020] A second somewhat more general embodiment of an emergency lighting equipment according to the invention is represented in Figure 2. In its structure it basically coincides with the emergency lighting equipment shown in Figure 1 although in this case The charging circuit 3 does not consist of a flyback converter, but generally a connection device that has a potential separation as well as a switch S1 controlled in turn by the control unit 2.

[0021] In this more generalized variant, there is not necessarily a known relationship between the input voltage Uin and the voltage on the output side of the load circuit 3. Despite this, it can also be determined in this case via Indirectly, the input voltage Uin is measured, however, with this reason different operating quantities.

[0022] It is, on the one hand, the voltage of the Ubat battery as well as, on the other hand, the current of the Ibat battery. Both quantities can be determined relatively easily, that is, without galvanic separation, because they also have the same reference power as the control unit 2 that evaluates these measurement quantities.

[0023] On the basis of these two measurement quantities Ubat and Ibat as well as the known duty cycle D1 of the switch S1 of the load circuit 3, the input voltage Uin can be determined since it is related to the three known quantities . This is shown in the graph in Figure 3 that represents different characteristic curves of the secondary power Pf1b2 of the load circuit 3 as a function of the duty cycle D1 for the switch S1. These characteristic curves are determined, for example, when manufacturing the emergency light equipment and are recorded in the form of a table in the control unit 2. It can be seen that these characteristic curves depend in particular on the input voltage Uin. Once the duty cycle D1 as well as the secondary power Pf1b2 of the load circuit 3 are known, conclusions can be drawn about the input voltage Uin, as in the example of Figure 1.

[0024] Therefore, in the example shown in Figure 3, the characteristic curve with which the known combination of duty cycle D1 and secondary power Pf1b2 of the load circuit 3 is determined, which, with the exciter circuit 5 deactivated corresponds to the product of the battery voltage Ubat and the battery current Ibat. In the case of the measured values represented, this value is found, for example, in the characteristic curve of an input voltage Uin of 220 volts, which corresponds to a normal state of the general supply of the network. However, if the determined value were in a corresponding characteristic curve, for example, at an input voltage Uin of 140 volts or 280 volts, the control unit 2 would interpret this in the sense of an error in the supply of the network and would therefore initiate a state of emergency.

[0025] This means that in the two exemplary embodiments shown it can be determined reliably and without the need for a direct measurement of the input voltage Uin if the supply of the network is good or not. However, a limitation in the example of Figure 2 is that the described determination of the input voltage Uin is only possible in the disconnected state of the exciter circuit 5.

[0026] In the example of Figure 1, however, there is no such limitation, as already mentioned above. In any case, the control unit 2 will in principle cause the activation of the exciter circuit 5 and the corresponding LED connection at the time of detecting a fault.

[0027] Once the exciter circuit 5 is activated, it can be activated with high frequency and in the manner described above the switch S2 so that the LED operates at the desired power. In order to ensure in this case a constant power of the LED, it would be necessary to know both the voltage of the LED Uled and the current of the LED Iled to allow its regulation.

[0028] With reference to figure 5, details of the connection of the battery 4 will be explained.

[0029] As seen in Figure 5, an element 12 that can have the function of a linear regulator or a switching regulator and / or a switch is connected parallel to the battery 4. For example, this element 12 may consist of a transistor. Parallel to the battery 4, a measuring resistor (Shunt) 16 is also connected, so that the voltage drop in the Shunt 16 is representative of the battery current.

[0030] The measurement signal taken in the Shunt 16 is provided to a current register unit 13 preferably structured as a discrete connection and that a comparator 14 can present. The comparator 14 is only an example of the way in which an offset can be applied to the measurement signal of Shunt 16. The offset application is used to be able to evaluate in a simplified way the signals of different polarities that reproduce the battery current, the offset being chosen so that the signal levels are they can shift in such a way that the two polarities of the signals now have the same polarity and different amplitudes. In this way, both the battery charging current and the battery discharge current, which, as is known, often have different polarities, can be measured with relative ease and with the help of control circuit 2. Therefore a control signal 15 of uniform polarity is preferably provided to the control circuit 2.

[0031] If the transistor 12 is configured as a linear regulator, a regulation of the discharge current of the battery and / or of the battery can be carried out by means of the current register unit 13 and the control of the linear regulator 12 the charge current of the battery, at a preset theoretical value. More simply, this regulation can also be carried out as a protection circuit, so that in case of a battery charging current or a battery discharge current that is too high, switch 12 is opened to protect the battery 4.

[0032] In the event of a very prolonged mains voltage failure, a total discharge of the battery 4 can occur. If the battery 4 is completely discharged it has a voltage of, for example, 1.3 volts which, for consequently, it is less than the allowable voltage of, for example, 1.5 volts. Although a normal mains voltage is now registered on the input side in the charging circuit 3 and that the charging circuit 3 functions correctly in the manner described above, the fully discharged battery 4 will cause the secondary side of the charging circuit descend to an unacceptably low value.

[0033] According to the invention, this complete discharge can be detected by recording the voltage of the battery 4. By registering a complete discharge of this type, the switch 12 is preferably actuated by pulses. Preferably, the switch 12 closes only for a relatively short period of time, and a battery charging process occurs within this short period of time. Then the switch 12 reopens for a prolonged period so that the battery 4 is it separates from the secondary side of the charging circuit 3 whereby the charging circuit 3 can again provide the normal voltage of for example 1.5 volts on the secondary side. Therefore, on the secondary side a normal voltage is recorded for a much longer period of time.

[0034] There is therefore a charge in the form of pulses of the battery completely discharged.

[0035] While the switch 12 remains open, the newly applied mains voltage correctly supplies the exciter circuit of LEDs and LEDs by means of the charging circuit. However, when the switch is closed for a few moments the battery is recharged. The pulse ratio for switch 12 can be chosen, for example, so that it only closes for 10% of the total time and remains open for the remaining 90% of the time, so that the battery can be recovered during this 90 % of the time

[0036] Detected the total discharge of the battery by recording the battery voltage can be automatically switched to the pulse operation of the switch 12. The battery voltage control preferably occurs through a discrete circuit and, therefore, regardless of the microcontroller 2 (see figures 1, 2) that, in case of too low battery voltage, it may not work perfectly.

[0037] For this reason, the current registration circuit 13 with the comparator 14 is preferably chosen as a discrete circuit independent of the microcontroller 2 and its normal operation.

[0038] Figure 6 shows other details of a circuit of LED drivers 5 according to the invention. All the characteristics of the battery circuit seen in Figure 5 can be logically combined with the circuit of Figure 6.

[0039] As described above, the basic principle of the exciter circuit 5 consists of a switching regulator in which, with the switch S2 closed, the winding L is magnetized with what, when the switch S2 is opened again, The magnetic energy is discharged through a current circuit that presents in series a Zener diode, at least one LED as well as an ohmic resistance

17.

[0040] As is known, it is relatively simple to measure the current flow through the diodes when the switch S2 is closed.

[0041] However, it is somewhat more complicated to measure the current flow through the LED’s when the S2 switch is open.

[0042] In accordance with the invention, for the current register the resistor 17 is connected in series with the LEDs, this resistor 17 representing an example of a means for the current recording.

[0043] A current register unit 18 may have, for example, a comparator 19.

[0044] A current recording signal, that is, a signal that reproduces the current passing through the LEDs, is provided to the control circuit 2. The control circuit 2 can configure the switching behavior of the switch S2 as a function of The current registration signal.

[0045] A capacitor 30 is connected in parallel with at least one LED. The capacitor 30 flattens the LED current by accumulating the energy and maintaining the fundamentally constant voltage across the LED. The capacitor 30 is sized for this purpose so that there is still the possibility of regulating the LED voltage.

[0046] Figure 7 schematically shows the control of switch S2, that is, in the case that this switch is configured as a FET transistor, the gate control of this transistor together with the current passing through the LED's . During the switch-on time of switch S2, the current through the LED’s increases. During the disconnection time, it is lowered again, driven by the magnetic energy of the winding L. As a consequence, a zig-zag curve of the current passing through the LEDs with a fixed DC value is produced. It is necessary that the current recording system can determine in particular the temporal average of this current in order to be able to choose, for example, the power of the LED's with a constant value or with an optional value (attenuation).

[0047] According to the invention it is envisioned that the control circuit 2, which establishes the switching behavior of the switch S2 and, therefore, knows how to determine the current value with respect to a first measurement point A as well as with with respect to a second measurement point B in order to calculate, from both, the weighted value. The time average of the LED current results from this weighted value of the current value at the moment of measurement A and the moment of measurement B.

[0048] The measurement point A is chosen so that it is at the end of the switch-off time S2 while the moment B is chosen so that it is at the end of the connection time.

[0049] For a measurement cycle, a measurement of several minimum and maximum values is preferably performed. In this way irregularities can be eliminated in relation to the moment of measurement. For this measuring principle, the measuring moments are synchronized with the sequences of switch S2. However, with this synchronization irregularities can occur that are justified, for example, with delays of the A / D transformers. These irregularities are avoided by registering several values.

[0050] Therefore, in this way the average time of the current can be determined by the LEDs, and the control unit 2 can regulate the connection frequency and / or the sequential relationship of the switch S2 as a function thereof. To dim the LEDs, the control unit 2 can superimpose, for example, the high frequency sequence of the switch S2, a lower frequency modulation, for example in the form of a PWM modulation. This supposes an alternative or additional possibility of attenuation, since, as said before, the attenuation can be carried out by modifying the high frequency sequence of the switch S2 itself.

[0051] According to the invention, the attenuation of the LEDs, that is, the regulation of the LED current to an eligible defined value, independently of other magnitudes. It is possible, for example, to attenuate depending on the discharge current of the registered battery (see the circuit in Figure 5) in order to extend the life of the battery.

[0052] The exciter circuit 5 can also dim the LEDs when the average value of the mains voltage supplying the load circuit 3 falls below a preset value. As another assistance measure to prolong the life of the battery, a pulse operation of the flyback converter in the charging circuit 3 can be caused so that the flyback converter feeds the exciter circuit 5 assisting the battery voltage that is going weakening

[0053] To detect a discharge of the battery voltage 4, the battery voltage can be recorded (see again Figure 5).

[0054] In addition to the LED current register, the voltage of the LEDs can be recorded.

[0055] A softstart function can be provided, with which the control circuit 2, when started up, initially passes a relatively low test current through the LEDs. With this test measurement, it is intended to determine electrical parameters to find out what are the LEDs connected to the exciter circuit 5. It is possible, for example, to determine the LED voltage that results with the specified test current. From it, conclusions can be drawn about the type (color) and the number of LEDs connected to regulate, in turn, depending on this value, the stationary service current adapted to the type of LED found.

[0056] It can always be provided that, when started, the control unit 2 increases the LED current by means of the corresponding control of the switch S2 of the exciter circuit 5, starting from a low value, to the stationary service value of LED current.

[0057] When the application of the test current indicates the fault or failure of one of the LED’s, the application of the test current can be repeated automatically at preset intervals until the regulatory operation of the LED is detected.

[0058] As mentioned, the current passing through the LED can be controlled either by superimposing a low frequency modulation up to the high frequency sequence of the switch S2 and / or by a variation (sequential relation, frequency) of the own high frequency sequence.

[0059] With reference to Figure 8, some of the aspects of the invention will now be explained in terms of the voltage supply Vs. and the correct operation of the control unit 2 which, as is known, is usually configured to integrated digital circuit mode, especially a software controlled circuit mode, such as a microcontroller.

[0060] When the microcontroller 2 does not function properly it can happen that the microcontroller 2 keeps the switch S2 of the LED driver circuit 5 permanently in the closed state (driver).

[0061] A discrete error recording circuit 20 is therefore provided that records said state. This discrete error recording circuit 20 may, for example, have a capacitor that integrates the gate control signal of the switch S2 and thus records the permanent connection state of the LED excitation switch S2. If the connection signal (logically high) is permanently recorded, the voltage in the capacitor of the error recording circuit 20 that could be discharged with a logically ‘low’ signal increases, for example through an ohmic resistor. The error recording circuit 20 is connected to the microcontroller 2, that is, in the case of a permanent connection signal in the LED driver circuit 5, a signal is generated in the error recording circuit 20 which leads to a pin of the microcontroller 2 intended for this purpose. In the case of registering this signal on the pin, it is planned to archive the current operating data of the microcontroller 2 in a memory 21. Then the microcontroller 2 starts again after a reset.

[0062] A comparable process can be started if a circuit for recording the battery voltage 4 detects that the supply voltage of the microcontroller 2 falls, for example, clearly below the theoretical value of 1.5 volts. Also in this case the microcontroller 2 archives the service data in the memory 21. Of course, the microcontroller 2 only restarts when a sufficient supply voltage is registered for the microcontroller 2.

[0063] According to another aspect of the invention, the supply voltage Vs for the microcontroller 2 is provided by means of an element of the connection network (DC / DC converter) 22. The DC / DC converter 22 can be configured in in the form of a so-called booster converter (Buck / Boost converter) so that in the case of a low battery voltage (for example in the case of a discharge) the elevation ratio is increased thus providing a sufficient supply voltage for the microcontroller 2.

[0064] According to another aspect of the invention the microcontroller 2 causes the disconnection of all

5 the elements that are not absolutely necessary for the supply of the microcontroller 2 when, after a prolonged failure of the mains supply voltage, the battery voltage also decreases. Microcontroller 2 adopts a standby state. In this standby state, the interface of the microcontroller 2, which especially monitors the incoming bus signals of the bus line 11 and, consequently, of an external control unit 10, continues to function.

10 microcontroller 2 can process even in this standby state the incoming digital signals (for example a DALI signal) or other comparable signals.

[0065] In addition, the operation amplifier 14 of the current regulation system 13 of the battery 4 can be deactivated when the voltage of the battery is very low.

DOCUMENTS MENTIONED IN THE MEMORY

This list of documents indicated by the applicant is included exclusively for the purposes of reader information and is not an integral part of the European patent document. It has been prepared with the utmost diligence; however, the European Patent Office is not responsible for possible errors or omissions.

Patent documents indicated in the report:

. EP 120 24 28 A1 [0004]. US 2001054877 A1 [0005]

Claims (6)

1.-Emergency lighting equipment (1) comprising: - a battery (4)

-

a charging circuit (3) powered by mains voltage for the battery (4)

-

an exciter circuit (5) connected to the battery (4) for a light source (LEDF) in the form of a regulator with a switch (S2)

characterized in that the switch (S2) is controlled from an integrated digital control unit (2), also presenting a circuit for monitoring switches (20) independent of the control unit (2) that records the state in which the switch (S2) remains permanently closed due to a malfunction of the control unit (2).

2.

Emergency lighting equipment according to claim 1,

in which the switch monitoring circuit disconnects the control unit or causes a reset process.

3.

Emergency lighting equipment according to claim 1,

in which, before disconnection or reset, the control unit (2) stores the service data in a memory (21).

Four.

Procedure for the operation of emergency lighting equipment (1) in which a charging circuit (3) for a battery (4) is powered by the mains voltage,

 characterized because - in an exciter circuit (5) connected to the battery (4) for a light source (LED) in the form of a regulator a switch (S2) is controlled starting from an integrated digital control unit (2) and because a switch monitoring circuit (20) independent of the control unit (2) Registers the state in which the switch (2) remains permanently closed due to a malfunction of the control unit (2). 5. Method according to claim 4, wherein the circuit breaker monitoring circuit (20) disconnects the control unit (2) or causes a reset process. Method according to claim 4, in which, before switching off or resetting the control unit (2), the control unit (2) stores the service data in a memory (21).