DE102012006315B4 - An LED lighting device for an AC power supply and method of operating the LED lighting device - Google Patents

Abstract

LED lighting device (1) for an AC voltage supply (2), with a plurality of LEDS which form a complete chain (9), the LEDs being distributed in LED sub-groups (11a, b, c, d), in the LED lighting device (1) there is a supply voltage with alternating amplitude, at least two LED sub-groups (11a, b, c, d) being connected in parallel to one another in a lower circuit state (I, II) of the entire chain (9) and wherein the entire chain (9) in the lower circuit state (I, II) has a first forward voltage, with a circuit device (10) which is designed to serially connect the at least two LED sub-groups (11a, b, c, d) in a higher circuit state (II, III) to interconnect, the entire chain (9) in the higher switching state (II, III) having a second forward voltage which is greater than the first forward voltage, characterized by a short-circuit device (8) for bridging d he entire chain (8), one or the circuit device (10) being designed to activate the short-circuit device (8) at the beginning and at the end of a half-wave (12) of the supply voltage, the circuit device (10) being designed to activate the short-circuit device (8 ) to be activated during an activation period (K) when the supply voltage is less than the smallest forward voltage of the various circuit states (I, II, III), and by a current sink device (7) which is connected in series with the entire chain (9), wherein the current sink device (7) is designed as a controllable or regulatable current sink, the current sink device (7) being driven with a sinusoidal signal synchronous with a mains voltage or a filtered mains voltage of the AC voltage supply (2) or with the supply voltage, the current sink device (7) is designed to output a chain stream for the entire chain (9), so that the assembly uppe comprising the current sink device (7), the short-circuit device (8) and the entire chain (9) receives a chain current sinusoidal to the synchronous sinusoidal signal, and so that the temporal course of the supply current with the temporal course of the supply voltage or the temporal course of the mains voltage or filtered mains voltage of the AC voltage supply (2) is synchronized.

Description

The invention relates to an LED lighting device for an AC power supply, comprising a plurality of LEDS, which form an overall chain, wherein the LEDS are distributed in LED subgroups, wherein the supply voltage with alternating amplitude is applied to the LED lighting device, wherein in a lower circuit state of the overall chain at least two LED subgroups are connected in parallel with one another and wherein the overall chain has a first forward voltage in the lower circuit state. The invention also relates to a method for operating the LED lighting device.

LED lights are increasingly used for the illumination of rooms and the like, since they can implement a high optical yield at the same time low energy consumption. If one compares LED luminaires with classic incandescent luminaires, it is obvious that the operation of the luminaires is considerably easier with a conventional luminaire with an AC power supply than with LED luminaires. While classic incandescent lamps can be easily supplied with AC voltage, paying attention only to the height of the AC voltage, LED lights can only be operated in a very limited voltage range. In the case of an LED light, on the one hand, a minimum voltage must be exceeded in order to make the LED light shine. Secondly, if the voltage applied is too high, too much current will flow through the LED light, causing it to fail after a short time without active cooling.

The working window with respect to the voltage level for supplying the LED lamp is thus comparatively narrow. In particular, it is not possible to connect an LED lamp directly to an AC power supply, since operation of the LED lamp is not possible due to the greatly changing voltage values.

The publication DE 20 2011 105 404 U1 includes various options for supplying power to LEDs, it being also noted that light emitting diodes can be powered by an AC voltage source, between the LEDs with any series resistors a bridge rectifier is arranged so that the LEDs are supplied with pulsating current.

The publication DE 10 2010 040 266 A1 discloses an LED lamp having a plurality of LED sub-strings, wherein the sub-strings are short-circuited or activated in response to an electrical configuration. The pamphlets DE 10 2007 040 152 A1 and DE 10 2007 041 131 A1 concern similar lights. The publication US 7781979 B2 discloses a method and apparatus for operating serially connected LEDs. In the 4 For example, an embodiment for operating the device in an automotive application having a battery with a supply voltage of 12 volts is disclosed.

The publication EP 2 288 234 A1 , which forms the closest prior art, relates to an LED driver device which supplies at least two LED sub-strings with an operating voltage. The LED driver device makes it possible to switch the at least two LED sub-strings in parallel or in series by changing the electrical configuration. The publication US 2011 // 0248640 A1 forms a similar state of the art.

It is an object of the present invention to propose an LED lighting device adapted for an AC power supply. This object is achieved by an LED lighting device having the features of claim 1 and by a method having the features of claim 7. Preferred or advantageous embodiments of the invention will become apparent from the dependent claims, the following description and the accompanying drawings.

In the context of the invention, an LED lighting device is disclosed, which is designed for an AC power supply. The AC power supply can be, for example, a public power grid with an effective mains voltage of 230 volts and a grid frequency of 50 hertz. Particularly preferably, the AC voltage supply has an effective voltage of 115 volts and a mains frequency between 400 hertz and 800 hertz, such an ac voltage supply being provided, for example, in an aircraft.

The LED lighting device has a plurality of LEDs (light-emitting diode / light emitting diode), which form an overall chain. The multiple LEDs can z. B. be designed as white LEDs, red LEDs, green LEDs or blue LEDs or as a mixture thereof. In a preferred embodiment, all LEDs are designed as white LEDs. The overall chain describes an electrical connection of the plurality of LEDs, wherein the entire chain is powered by a common, in particular two-pole connection with energy. Within the overall chain, the plurality of LEDs may be arranged electrically parallel or serially to one another or in a hybrid form.

The LEDs are organized or distributed in LED subgroups, with at least one LED in each LED subgroup. In the smallest Embodiment of the invention thus exactly one LED is arranged in each LED subgroup, in a preferred embodiment of the invention, a plurality of LEDs is arranged in each LED subgroup. Within the LED subgroup, the LEDs can be arranged electrically parallel or serially or in a mixed form with each other. Each LED subgroup also has its own, in particular two-pole, connection to the power supply.

Due to the AC voltage supply is a supply voltage with varying amplitude. In one possible embodiment of the invention, the LED lighting device comprises an optional line filter, a rectifier and a PFC module, which together generate the supply voltage of alternating amplitude from the AC voltage supply. In a special embodiment, the supply voltage is designed as a rectified AC voltage, in particular rectified sinusoidal AC voltage.

In a lower circuit state of the overall chain, at least two LED subgroups are electrically connected in parallel with one another, so that the overall chain has a first forward voltage in the first circuit state. A parallel connection of two LED subgroups is present, in particular, when the poles of the same name of the LED subgroups are connected to one another.

In the context of the invention, it is proposed that the LED lighting device comprises a circuit device which is configured to connect the at least two LED subgroups in a higher circuit state serially to each other, wherein the overall chain in the higher circuit state has a second forward voltage which is greater than the first forward voltage is. Under the forward voltage - also called forward voltage - is understood in particular the threshold voltage, which must be present, so that the LEDs in the LED subgroup to light up.

In the case of the serial connection of the at least two LED subgroups, the LED subgroups are connected one after the other or one after the other. This type of circuit is also referred to as a series circuit.

It is a consideration of the invention that, depending on the interconnection of multiple LED subgroups in an overall chain, the overall chain may have different forward voltages. For example, if you switch two LED subgroups with only one LED at a forward voltage of 3.4 volts as a whole chain in parallel, the first forward voltage is 3.4 volts. If the said two LED subgroups are switched serially (or in series), then the second forward voltage is 6.8 volts and is thus greater than the first forward voltage. The circuit device according to the invention thus achieves that the overall chain can be adapted by changing the circuit state in the forward voltage.

The circuit device consequently makes it possible for the forward voltage to be flexibly adaptable to the changing amplitude of the supply voltage. In this way, it can be achieved that the plurality of LEDs are operated with respect to the voltage level in an acceptable working window, without letting the losses due to series resistors become too large.

In a preferred embodiment of the invention, the circuit device is configured to change the circuit states such that the circuit state is activated, which has the highest forward voltage, wherein the forward voltage is less than or equal to the current supply voltage. It is thus always selected the circuit state, which makes the best use of the supply voltage. This mode of operation prevents overheating of the LEDs due to excessive voltages and at the same time operates the LEDs in an energy-efficient range.

In a preferred embodiment of the invention it is provided that the curve of the supply voltage is formed by a repeating shaft portion. Is the supply voltage z. B. formed as a rectified, sinusoidal AC voltage, the shaft portion is formed in each case as a sinusoidal half-wave. The different circuit states are taken regularly during the shaft sections. Thus, a rising edge is changed from the lower circuit state to the higher circuit state on a regular basis and changed from the higher circuit state to the lower circuit state at a falling edge of the shaft section. This embodiment emphasizes that the adaptation of the circuit states is implemented highly dynamically, namely during the repeating wave section. In particular, it is not a static change in the circuit state, which extends over several shaft sections. In this way, the overall chain during a shaft section is preferably adjusted on average by at least one, preferably at least two and in particular at least four changes in the circuit state to the instantaneous value of the supply voltage.

In a preferred embodiment of the invention, the circuit device is designed to interconnect the overall chain in at least three different circuit states, wherein the total chain in each case has a different forward voltage in the at least three circuit states. The transition from one to a next circuit state is each time converted by a transition from a lower circuit state to a higher circuit state (or in the opposite direction). The terms lower circuit state and higher circuit state thus refer to a relative change of the circuit states, the at least three circuit states, however, relate to absolute circuit states.

In a preferred embodiment of the invention, the total chain has exactly four LED subgroups, wherein in a first circuit state all four LED subgroups are connected in parallel, in a second circuit state two pairs each with parallel LED subgroups are arranged serially to one another and in which third circuit state, all four LED subgroups are connected in series with each other. Particularly preferably, the four LED subgroups are constructed identically and / or have the same forward voltage. In this preferred embodiment, the forward voltage is doubled at each transition.

In a similar embodiment, the overall chain can have exactly eight LED subgroups, which can assume four different circuit states. In this embodiment, the eight LED subgroups in a zeroth circuit state are all arranged in parallel with each other, in a first circuit state, two groups of four LED subgroups each are serially arranged with the four LED subgroups in the group being arranged in parallel. The transition to the second and third circuit state is carried out as described in the embodiment with exactly four LED subgroups.

The circuit device is preferably designed such that on a rising edge in a shaft section, first and if present, the zeroth circuit state, then the first, the second and the third circuit state is assumed. In the case of a falling edge of the same shaft section, first the third circuit state, then the second, the first and, if present, the zeroth circuit state are assumed. This embodiment again emphasizes the idea that the different circuit states are taken regularly during a shaft section, in particular during a half-wave, in order to dynamically adjust the forward voltage of the overall chain to the amplitude of the supply voltage.

According to the invention, the LED lighting device has a current sink device which is connected in series (or in series) with the overall chain. The supply voltage and a supply current are applied to the current sink device. The current sink device is designed to correct a chain current for the entire chain, so that the time profile of the supply current is synchronized with the time profile of the supply voltage or the time profile of a mains voltage of the AC voltage supply.

This development of the invention is based on the consideration that would flow through the change in the circuit states and the changing amplitude of the supply voltage without further measures a very uneven current through the entire chain. The current through the total chain is also referred to here as chain current. Due to the uneven chain current, a similarly uneven mains current would be drawn from the AC power supply on the one hand, and on the other hand, a very uneven brightness would be output at the several LEDs. In order to reduce these effects, the current sink device ensures that the chain current is always selected so that the supply current is optionally synchronized with the time profile of the supply voltage or the time profile of the mains voltage of the AC voltage supply. The mentioned time profiles can be introduced in the current sink device as a reference variable. The current sink device has z. B. a controllable internal resistance whose height is calculated by the quotient of the differential voltage between the supply voltage or mains voltage and the current forward voltage of the entire chain divided by the desired supply current. In particular, the current sink device is controlled or regulated such that a power factor of the LED lighting device remains high.

According to the invention, the LED lighting device comprises a short-circuit device, in particular a bypass device, for bridging the entire chain, one or the circuit device being designed to activate the short-circuit device at the beginning and at the end of a shaft section of the supply voltage. In particular, it is provided that the circuit device is designed to activate the short-circuit device when the supply voltage is smaller than the smallest forward voltage of the different circuit states. This training ensures that at the beginning and at the end each shaft section the entire chain is bridged, as long as the supply voltage is not sufficient to bring the LEDs in the overall chain to light up. Optionally, it may be provided that the supply current available on the basis of the activated short-circuit device is destroyed by the current sink device, or is converted into heat, in order to keep the power factor of the LED lighting device high.

A further subject relates to a method having the features of claim 7.

Further features, advantages and effects of the invention will become apparent from the following description of a preferred embodiment of the invention and the accompanying figures. Showing:

1 a schematic block diagram of an LED lighting device as an embodiment of the invention;

2a , b, c a schematic representation of an overall chain of LEDs in the 1 in different switching states;

3 a graph illustrating the operation of the LED lighting device in the 1 ;

4 a detail of the LED lighting device in the 1 ;

5 a graph illustrating a possibility of an improved switching operation of the LED lighting device in the 1 ,

The 1 shows a schematic block diagram of an LED lighting device 1 which is suitable for operation with an AC power supply 2 is trained. The LED lighting device 1 serves, for example, to illuminate the interior of an aircraft in the passenger area. The LED lighting device 1 is to the AC power supply 2 from which it relates a mains voltage and a mains current. After an entrance 3 in the LED lighting device 1 Optionally follows a line filter 4 , which is formed, interference, which in the AC power supply 2 could be fed back to filter. In particular, it is a low-pass filter, which is formed for example by an interconnection of capacitors and inductors.

The mains filter 4 is a rectifier 5 downstream, which is designed to convert the applied mains voltage or filtered mains voltage in a rectified supply voltage. The rectifier 5 is designed for example as a bridge rectifier. The rectified supply voltage and the rectified supply current is sent to a PFC module 6 which comprises a harmonic filter or a power factor correction filter and a smoothing device, such as a capacitor. In the power correction filter, at least one switching element is arranged, so that the power factor correction filter as a clocked system or the combination of rectifier 5 and PFC module 6 is designed as a switching power supply.

The PFC module 6 provides a supply voltage and a supply current following a current sink device 7 - also called electronic load - to be handed over. The current sink device 7 is designed, regulated or controlled electricity and thus to destroy power by converting it into heat.

Starting from the current sink device 7 be a chain tension and a chain stream via a short-circuit device 8th to an LED overall chain 9 passed with a plurality of LEDs.

The LED lighting device 1 also includes a circuit device 10 , which - as shown here - may be formed in one piece or multi-part and which for controlling the LED overall chain 9 and the short-circuit device 8th is trained. As an input signal, the circuit device receives 10 the chain tension, which also corresponds to the supply voltage. Alternatively, the circuit device receives 10 the supply voltage as the input signal. The circuit device 10 can z. B. be designed as a programmable microcontroller.

The LED overall chain 9 is via the circuit device 10 switchable to different circuit states, as related to the 2a , b and c will be explained.

The 2a shows the LED overall chain 9 in a first schematic representation. The LED overall chain 9 includes an input E and an output A (or a first and a second pole), via which the LED overall chain 9 to the in the 1 shown power supply is connected.

The LED overall chain 9 includes four in this example LED subgroups 11a , b, c, d, where each LED subgroup 11a , b, c, d has at least one LED. In particular, each LED subgroup has 11a , b, c, d are the same forward voltage (also called forward voltage). The LEDs in the LED subgroups 11a , b, c, d can - as symbolically in the 2a shown - in each of the LED subgroups 11a , b, c, d be connected in series (or in series) to each other. In modified embodiments, the LEDs in the LED subgroups 11a , b, c, d are also connected in parallel, in series or in parallel and mixed in series with one another.

The four LED subgroups 11a However, b, c, d are in the in the 2a shown first circuit state I of the LED overall chain 9 arranged electrically parallel to each other, so that the forward voltage of the LED overall chain 9 the forward voltage corresponds to one of the LED subgroups.

In the 2 B a second circuit state II is shown, wherein the LED subgroups 11a , b, c, d in the overall LED chain 9 now partly electrically connected in series (in series). For example, it is provided that in the first group, the LED subgroups 11a , B are arranged parallel to each other and in the second group, the LED subgroups 11c , D are also arranged parallel to each other, but the two groups are arranged serially to each other. In the circuit state II, the forward voltage corresponds to the total LED chain 9 now twice the forward voltage of one of the LED subgroups 11a , b, c, d.

In the 2c a third circuit state III is shown, where now all four LED subgroups 11a , b, c, d to each other are arranged electrically in series (in series). The forward voltage of the LED overall chain 9 now corresponds to four times the forward voltage of one of the LED subgroups 11a , b, c, d.

At each transition from one circuit state to a next circuit state, there is a transition from a lower circuit state to a higher circuit state in which at least one pair of LED subgroups previously connected in parallel 11a , b, c, d have been connected in series. Thus, in the transition from the circuit state I to II, the previously arranged parallel LED subgroups 11a and 11c as well as the previously arranged parallel LED subgroups 11b . 11d connected in series with each other. During the transition from circuit state II to circuit state III, the LED subgroups connected in circuit state II become parallel to one another 11a , b or parallel to each other LED subgroups 11c , d in each case connected in series with each other.

The circuit device 10 is formed, the LED overall chain 9 to switch to the different circuit states I, II, III. A corresponding control circuit for this type of switching can be realized, for example, with the aid of diodes and transistors.

The 3 shows a half-wave in a schematic graph 12 the chain tension, which also corresponds to the supply voltage. In the graph, the time t is plotted on the x-axis and the amplitude in any units on the y-axis. The circuit device 10 receives as input signal the chain tension or a proportional signal. At the beginning of the half-wave 12 becomes the total LED chain 9 switched on the circuit state I, so that the LED overall chain 9 has a first, low forward voltage. As a result, even with the comparatively low chain tension, the LEDs of the LED overall chain can 9 be lit up. If the chain tension continues to increase, this in particular exceeds the second forward voltage of the LED overall chain 9 in the circuit state II, the circuit device switches 10 the LED overall chain 9 in the second circuit state II order. Once the chain tension the third forward voltage of the third circuit state III of the LED overall chain 9 has exceeded is by the circuit device 10 the circuit state III is set. On the descending flank of the half wave 12 the process repeats in reverse order. By switching the LED overall chain 9 in the manner described, it is possible to use the forward voltage of the LED overall chain 9 much better to the current chain tension of the half-wave 12 adapt and thus the efficiency and the light duration of the LED overall chain 9 to improve.

The 4 shows a schematic representation of a section of the LED lighting device 1 , namely the current sink device 7 , the short-circuit device 8th as well as the LED overall chain 9 , The current sink device 7 is designed as a controllable or controllable current sink, which is driven in this embodiment with a synchronous to the mains voltage or to the filtered mains voltage or to the supply voltage sinusoidal signal, so that the modules comprising the current sink device 7 , the short-circuit device 8th and the LED overall chain 9 pick up a sinusoidal chain current to the synchronous sinusoidal signal.

The short-circuit device 8th serves - as shown schematically in the 5 is shown - at the beginning and at the end of the half wave 12 during an activation period K, the total LED chain 9 during which the chain tension is lower than the lowest forward voltage of the circuit states I, II, III. During these periods, the current sink device 7 let a chain current flow, so that the power factor requirements of the LED lighting device 1 continue to be fulfilled.

LIST OF REFERENCE NUMBERS

1

LED lighting device

2

AC power supply

3

entrance

4

Line filter

5

rectifier

6

PFC module

7

Current sink means

8th

Short-circuit device

9

LED total chain

10

circuit means

11a, b, c, d

LED subgroups

12

half-wave

Claims (7)

LED lighting device ( 1 ) for an AC power supply ( 2 ), with multiple LEDS, representing an overall chain ( 9 ), where the LEDS are divided into LED subgroups ( 11a , b, c, d) are distributed, wherein in the LED lighting device ( 1 ) is a supply voltage of varying amplitude, wherein in a lower circuit state (I, II) of the total chain ( 9 ) at least two LED subgroups ( 11a , b, c, d) are connected in parallel with each other and wherein the total chain ( 9 ) in the lower circuit state (I, II) has a first forward voltage, with a circuit device ( 10 ), which is formed, the at least two LED subgroups ( 11a , b, c, d) in a higher circuit state (II, III) to connect in series with each other, wherein the total chain ( 9 ) in the higher circuit state (II, III) has a second forward voltage that is greater than the first forward voltage, characterized by a short-circuit device ( 8th ) for bridging the entire chain ( 8th ), one or the circuit device ( 10 ), the short-circuit device ( 8th ) at the beginning and at the end of a half wave ( 12 ) of the supply voltage, wherein the circuit device ( 10 ), the short-circuit device ( 8th ) during an activation period (K) when the supply voltage is less than the lowest forward voltage of the various circuit states (I, II, III), and by a current sink device ( 7 ), which are in series with the total chain ( 9 ), wherein the current sink device ( 7 ) is designed as a controllable or controllable current sink, wherein the current sink device ( 7 ) with one to a mains voltage or to a filtered mains voltage of the AC power supply ( 2 ) or to the supply voltage synchronous sinusoidal signal is driven, wherein the current sink device ( 7 ) is formed, a chain flow for the entire chain ( 9 ), so that the assembly comprising the current sink device ( 7 ), the short-circuit device ( 8th ) and the total chain ( 9 ) receives a sinusoidal chain current to the synchronous sinusoidal signal, and so that the time profile of the supply current with the time course of the supply voltage or the time course of the mains voltage or the filtered mains voltage of the AC power supply ( 2 ) is synchronized. LED lighting device ( 1 ) according to claim 1, characterized in that the circuit device ( 10 ) is adapted to change the circuit states (I, II, III) so that the circuit state (I, II, III) is activated with the highest forward voltage, wherein the forward voltage is less than or equal to the supply voltage. LED lighting device ( 1 ) according to one of the preceding claims, characterized in that the curve of the supply voltage through a repeating wave section ( 12 ), wherein the different circuit states (I, II, III) during the shaft section ( 12 ) are taken. LED lighting device ( 1 ) according to one of the preceding claims, characterized in that the circuit device ( 10 ), the overall chain ( 9 ) in at least three different circuit states (I, II, III), the total chain ( 9 ) in the at least three circuit states (I, II, III) each have a different forward voltage, and wherein at each transition from one circuit state (I, II) to the next (II, III) a transition from a lower circuit state (I, II ) is converted into a higher circuit state (II, III). LED lighting device ( 1 ) according to one of the preceding claims, characterized in that the total chain ( 9 ) exactly four LED subgroups ( 11a , b, c, d), wherein in a first circuit state (I) all four LED subgroups ( 11a , b, c, d) are connected in parallel, in a second circuit state (II) in each case two pairs with parallel LED subgroups ( 11a , b; 11b , c) are arranged serially to each other and in the third circuit state (III) all four LED subgroups ( 11a , b, c, d) are connected in series with one another. LED lighting device ( 1 ) according to claim 5, characterized in that the circuit device ( 10 ) is formed at a shaft portion ( 12 ) of the supply voltage at a rising edge of the shaft section ( 12 ) First, the first circuit state (I), then the connect the second circuit state (II) and then the third circuit state (III) and at a falling edge of the shaft portion (II) 12 ) first to connect the third circuit state (III), then the second circuit state (II) and then the first circuit state (I). Method for operating the LED lighting device ( 1 ) according to one of claims 1 to 6, performed by the circuit device ( 10 ).

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