DE102018102643B4 - LED lamp to be mounted in a fluorescent lamp socket - Google Patents

Abstract

LED lamp for mounting in a fluorescent lamp holder with a ballast (60), the LED lamp comprising: - a plurality of light emitting diodes (11), - a detection circuit (64) arranged to generate a control signal indicative of whether the ballast ( 60) is a conventional ballast or an electronic ballast, and- a first control circuit (61, 65) adapted to couple between the ballast (60) of the lamp socket and the light emitting diodes (11) during a starting sequence of the ballast (60) in dependence on the control signal,- wherein the first control circuit (61, 65) stabilizes a voltage drop across the light-emitting diodes (11) during the starting sequence, and wherein an impedance between the ballast (60) of the lamp socket and the light-emitting diodes (11) is controlled by the first control circuit (61 , 65) is increased during the start-up sequence, the first control circuit (61, 65) having a first Tra activated during the start-up sequence nsistor (21, 25) and a second transistor (22, 26) deactivated during the starting sequence, and wherein the first transistor (21, 25) and the second transistor (22, 26) are connected such that the second transistor (22, 26) can turn off the first transistor (21,25) when the second transistor (22,26) is activated.

Description

Technical part

The present invention relates to an LED lamp for mounting in a fluorescent lamp socket.

background

Fluorescent lamps have been well known and widely used lighting devices for years as efficient alternatives to incandescent lamps. With the advent of LED lamps, even more efficient and long-lasting light sources are available. Furthermore, compared to fluorescent lamps, materials of LED lamps are safer because, for example, no mercury is required. Therefore, there is a need to replace existing fluorescent lamps with LED lamps, preferably without having to change the entire luminaire or lampholder.

Currently available fluorescent lampholders include either a conventional ballast (also called conventional control gear, CCG) or an electronic ballast (also called electronic control gear, ECG) for regulating and limiting the current supplied to the fluorescent lamp.

Conventional ballasts, also known as magnetic ballasts, limit the alternating current using an inductance with a frequency-dependent impedance. These ballasts operate a lamp at the mains supply operating frequency, which is typically 50 Hz or 60 Hz. Due to ohmic losses in the inductance, around 10% to 20% of the luminaire's power is lost as heat, so that a conventional ballast is not very efficient.

In contrast to conventional ballasts, electronic ballasts operate the lamp at high frequencies from a few kHz up to 50 kHz. The frequency of the electronic ballast is selected in such a way that a resonant frequency of the lighting means, in particular of the fluorescent gas, is reached, so that active control of the current through the fluorescent lamp is made possible. This allows to improve the efficiency of the electronic ballast compared to the conventional ballast.

In order to provide an LED lamp that is compatible with the lampholders described above, LED lamps include electronic drivers for adjusting the voltage and current provided by the ballast to the requirements of light emitting diodes. Otherwise electronic and/or optoelectronic components of the LED lamp could be damaged or destroyed by the ballast due to high voltages generated especially during the start-up sequence.

However, currently available LED lamps are only suitable for either a conventional ballast or an electronic ballast. Furthermore, the latter may also require some changes to the lamp socket, such as changing the electrical connections, so replacing fluorescent lamps with LED lamps becomes a complex and uneconomical task. Document US 2012 / 0 306 403 A1 describes a driver circuit for adapting a DC lamp for operation with an AC source, with an electromagnetic ballast or with an electronic ballast, the driver circuit having a first stage with a filter circuit, a second stage with a high-frequency Switching network and a third stage for providing a direct current includes. The document US 2014 / 0 125 253 A1 describes an LED ballast control device with a ballast connector configured to be plugged into the socket of a fluorescent tube or a gas fluorescent tube with a socket, and a dynamic-adaptive resistor network with multiple AC switches and resistive loads connected in parallel.

Summary of the Invention

In view of the above-described disadvantages of currently available LED lamps, it is an object of the invention to provide a versatile LED lamp which can be mounted in a fluorescent lamp socket with a conventional ballast and a fluorescent lamp socket with an electronic ballast without the electronic connections of the respective ballast to have to change significantly.

This object is solved with an LED lamp according to the main claim. Preferred configurations are specified in the dependent claims, the description and the drawings.

Accordingly, there is provided an LED lamp for mounting in a fluorescent lamp socket, the fluorescent lamp socket having a ballast. The LED lamp includes multiple light emitting diodes, a detection circuit, and a first control circuit. The detection circuit is designed to generate a control signal which indicates whether the ballast of the lamp socket is a conventional ballast or is an electronic ballast. Further, the first control circuit is adapted to couple between the lampholder ballast and the light emitting diodes during a ballast start-up sequence in response to the control signal, the first control circuit stabilizing a voltage drop across the light-emitting diodes during the start-up sequence.

The use of the detection circuit in combination with the first control circuit ensures that the LED lamp can be installed in a lamp socket with a conventional ballast as well as in a lamp socket with an electronic ballast. In order to allow use with an electronic ballast, a high voltage that might arise during a start-up sequence of the electronic ballast is equalized and stabilized by the first control circuit. Preferably, the voltage drop across the light-emitting diodes is reduced during the start-up sequence. An impedance between the lamp socket ballast and the light emitting diodes is increased by the first control circuit during the start-up sequence, the first control circuit comprising a first transistor activated during the start-up sequence and a second transistor deactivated during the start-up sequence. The first transistor and the second transistor are connected such that the second transistor can turn off the first transistor when the second transistor is activated.

Here and in the following, the "start-up sequence" of the electronic ballast is a short duration right after switching on the lamp installed in the lamp socket. If a fluorescent lamp is installed in the lamp socket, the ballast start-up sequence includes preheat and ignition. During preheating, a fluorescent lamp connected to the ballast acts as a high-impedance resistor, which leads to an increase in the voltage across the lamp. In the ignition mode, the electronic ballast generates a high voltage (over 600 V, up to about 1.1 kV) to ignite the fluorescent lamp. During ignition, current flows through the fluorescent gas, thereby switching the fluorescent gas into a low-impedance mode that allows the output voltage of the electronic ballast to drop. After the start sequence, the electronic ballast of the lamp socket switches to the so-called normal running mode. The LED lamp is preferably operated in run mode during all operation except for the duration during the start-up sequence.

The start-up sequence of the electronic ballast can lead to the destruction of electronic components in the LED lamp. In particular, the LED lamp comprises an electronic driver with a main control circuit for converting the voltage and/or current supplied by the lamp holder into the operating conditions of the light emitting diodes. For example, the driver ensures that the light-emitting diodes of the LED lamp are supplied with a constant output current. The main control circuitry of the driver may then comprise a switched mode power supply, for example with an AC/DC controller. If the driver starts slowly, especially in the case of a driver with a constant current output, then the preheat mode can be skipped by the electronic ballast and the ballast can enter the firing mode directly. This behavior is triggered by an internal controller of the lamp socket ballast. By skipping the preheat mode, high voltage is generated by the electronic ballast connected to the electronic driver, said voltage eventually destroying the driver or other electronic components of the LED lamp. On the other hand, if the ballast does not provide enough voltage for the driver to start, then the LEDs will flash in the preheating process of the ballast.

By adding the first control circuit to the driver of the LED lamp, for example, the above-mentioned problems can be overcome and the LED lamp can be installed in a conventional lamp holder with an electronic ballast. In combination with the detection circuitry, a versatile LED lamp is provided which can be used with an electronic ballast or a conventional ballast. Here, the first control circuit can be coupled between an input of the driver and a main control circuit of the driver if the ballast is an electronic ballast.

According to at least one configuration of the LED lamp, an impedance between the ballast of the lamp socket and the light-emitting diodes is increased by the first control circuit during the start-up sequence. In particular, the first control circuit can provide a known impedance that is added to the impedance of the driver if the ballast is an electronic ballast. This causes a change in voltage across the driver, which protects the driver.

According to a preferred embodiment of the LED lamp, the first control circuit is coupled between the ballast of the lamp socket and the light-emitting diodes only in the event that the Ballast is an electronic ballast. That is, if the ballast is a conventional ballast, then the first control circuit is not coupled between the ballast and the light emitting diodes. For example, the conventional ballast may be coupled directly to the main control circuitry of the driver of the LED lamp, thereby ensuring that losses that might arise due to the additional electronics of the first control circuitry are reduced and preferably avoided.

According to at least one aspect, the LED lamp includes a main control circuit. The main control circuit is designed to couple between the light emitting diodes and the ballast of the lamp socket after the start-up sequence and/or in the event that the ballast is a conventional ballast. The main control circuit preferably corresponds to the main control circuit mentioned above, which is part of the driver of the LED lamp. The LED lamp may include a switch, such as a transistor or a MOSFET, that allows switching between the first control circuit and the main control circuit. In the case of a conventional ballast and/or after the start-up sequence of the electronic ballast, the main control circuit can supplement or replace the first control circuit. The first control circuit is preferably replaced by the main control circuit. In other words, after the start-up sequence and/or in the case of a conventional ballast, the first control circuit can be decoupled from the ballast and the light-emitting diodes. The LED lamp then enters the normal run mode. For example, the first control circuit and/or the main control circuit may include electronic components configured to determine the end of the start-up sequence, such that the main control circuit can replace the first control circuit after the start-up sequence. Preferably, the main control circuit comprises or is a switched mode power supply.

According to at least one configuration of the LED lamp, the first control circuit accelerates a start of a main control circuit of the LED lamp. For example, if the main control circuit is a switched-mode power supply, an output of the first control circuit is coupled to a start-up circuit of the main control circuit to help establish a current with the main control circuit. This configuration is particularly advantageous when the electronic ballast skips a preheat mode when the LED lamp is coupled to the electronic ballast and enters the ignition mode directly. Skipping the preheat mode when an LED lamp is connected to the lamp socket ballast may be a characteristic of some electronic ballasts, especially constant current electronic ballasts. Starting a switching power supply is usually relatively slow compared to starting the electronic ballast. Therefore, high voltage is generated in the switching power supply of the main control circuit during start-up, and this voltage is added to the high ignition voltage. This high voltage can destroy the electronic components of the LED lamp. Speeding up the start-up of the main control circuit allows the constant current power supply to properly interact with the main control circuit, so that the electronic components of the main control circuit are protected from high voltages.

According to at least one configuration of the LED lamp, the first control circuit comprises a first transistor that is activated during the starting sequence and a second transistor that is deactivated during the starting sequence. Additionally or alternatively, the first transistor can be deactivated in the normal running mode and the second transistor can be activated in the normal running mode. In this context, "activated" means that the transistor is switched on, i.e. electrically conductive and/or switched on. Conversely, "deactivated" means that a transistor is switched off, i.e. blocks. For example, the first transistor is coupled to an output of the detection circuit that provides the control signal. The second transistor may be coupled to an output of the first control circuit that provides a signal when the start-up sequence is complete. In addition or as an alternative, the second transistor can be coupled to a feedback circuit of the light-emitting diodes, which circuit enables the voltage applied to the light-emitting diodes to be regulated.

According to at least one configuration of the LED lamp, the first control circuit is coupled to a flyback controller, which is coupled to an output of the first transistor. For example, the flyback controller may include a Schottky diode or a Zener diode. The flyback controller is preferably coupled to the second transistor. During the start-up sequence, the flyback controller can block current flow to the second transistor. After the start-up sequence, the voltage provided by the ballast can be reduced, thereby deactivating the first transistor and allowing the flyback controller to switch to a conducting mode and activate the second transistor.

According to at least one embodiment of the LED lamp, the first control circuit after the start sequence of the light-emitting diodes and the Ballast of the lamp holder disconnected, in particular completely disconnected. The decoupling takes place, for example, by means of a transistor, in particular by means of the second transistor mentioned above, in connection with the flyback controller and/or a start circuit. The starting circuit can correspond to a standard starting circuit for a switched-mode power supply.

According to at least one configuration of the LED lamp, the first control circuit is a constant current circuit. The constant current circuit preferably supplies a constant current to the light emitting diodes during the start-up sequence. The constant current circuit preferably has a fast turn-on behavior so that the high voltage provided by the lampholder ballast during the start-up sequence is balanced and preferably reduced.

According to at least one configuration of the LED lamp, the first control circuit is a suppression circuit, in particular with a low impedance. Due to the low impedance, the current supplied from the lamp socket ballast can flow directly to the light emitting diodes, and a start of a main control circuit of the LED lamp can be accelerated. Additionally, the first control circuit may provide a low impedance loop for an electronic ballast during the start-up sequence, thereby preventing the electronic ballast from generating a high voltage.

According to a preferred embodiment of the LED lamp, the detection circuit determines an operating frequency of the ballast of the lamp holder in order to provide the control signal. In the case of an electronic ballast, the operating frequency can be relatively high. A conventional ballast usually operates at the lower frequencies supplied by the mains power supply. Therefore, the type of ballast can be determined by determining the operating frequency. The operating frequency is preferably measured before a rectifier circuit of the LED lamp.

character list

• 1A zeigt eine Startsequenz eines elektronischen Vorschaltgeräts einer Lampenfassung für eine Ausgestaltung einer LED-Lampe gemäß der vorliegenden Erfindung.
• 1B zeigt eine beispielhafte Ausgestaltung einer alternativen Lampe.
• 2, 3, 4 und 5 zeigen Ausgestaltungen einer LED-Lampe gemäß der vorliegenden Erfindung.
• 6A und 6B zeigen eine beispielhafte Ausgestaltung einer alternativen LED-Lampe.
• 7A, 7B, 7C, 7D, 8A, 8B und 8C zeigen Messungen für Ausgestaltungen einer LED-Lampe gemäß der vorliegenden Erfindung.

Preferred configurations of the invention are explained below with reference to the drawings.

• 1A Figure 12 shows a lamp socket electronic ballast start-up sequence for an embodiment of an LED lamp according to the present invention.
• 1B shows an exemplary embodiment of an alternative lamp.
• 2 , 3 , 4 and 5 12 show embodiments of an LED lamp according to the present invention.
• 6A and 6B show an exemplary embodiment of an alternative LED lamp.
• 7A , 7B , 7C , 7D , 8A , 8B and 8C 12 show measurements for embodiments of an LED lamp according to the present invention.

Detailed Description of the Invention

Preferred embodiments of the invention are described below with reference to the drawings. Here identical, similar elements or those with an identical or similar effect have been given the same reference numbers in the figures. The figures and the relative sizes of the elements illustrated in the figures are not intended to be drawn to scale. Instead, individual elements may be exaggerated to facilitate better illustration and/or understanding.

Regarding 1A an exemplary embodiment of a starting sequence of an electronic ballast of a lamp holder for an LED lamp according to the present invention will be described in detail. A first exemplary voltage drop 14 for the case that a load is connected to the ballast and a second exemplary voltage drop 15 for the case of an unloaded ballast are given in volts. The no-load case 15 may correspond to the case after the fluorescent gas of the fluorescent lamp is ignited.

After switching on the lamp, the electronic ballast enters the preheating mode 100, in which the operating frequency ν is reduced and the first exemplary voltage drop 14 is thus increased. At a certain frequency, which may correspond to the resonant frequency of the fluorescent gas, ignition mode 101 is entered. At this point the fluorescent gas is illuminated, i.e. ignited. Due to the ignition, the fluorescent lamp is now essentially load-free. The voltage therefore drops to the second exemplary voltage drop 15 after ignition 102, with the operating frequency ν being retained. The operating frequency ν is then further reduced until the operating point of the running mode 103 is reached.

Regarding 1B 1, an exemplary embodiment of an alternative lamp without detection circuitry and/or a first control circuitry according to the present embodiment is detailed. The alternative lamp can a traditional fluorescent lamp 10 include. The illuminant 10 is connected to a ballast 60 via a number of electronic components which can be part of a driver for the lamp. The alternative lamp can thus be a traditional fluorescent lamp with a ballast 60. Two transistors 20 and two diodes 50 may be coupled between the ballast 60 and the illuminant 10 to thereby provide a rectifier circuit. For example, the rectifier circuit may convert AC power provided by ballast 60 to DC power. As another example, if the lamp is installed in the lamp socket in the wrong direction, resulting in incorrect polarity of the electrical connections, then the rectifier circuit will protect the lamp 10.

The transistors 20 can be in the form of FET or MOSFET transistors. Although the transistors 20 and the diodes 50 are shown with the same reference numbers, they can be configured differently. That is, the two transistors 20 and/or the two diodes 50 may have different characteristics depending on the particular application of the driver.

The lighting means 10 is also connected in parallel with a first capacitor 31 and in series with a second capacitor 32 and a first inductor 41 . The first capacitor 31 serves as a smoothing capacitor for the light-emitting diodes 11 of the lighting means 10. The first capacitor 31 can be an electrolytic capacitor, for example. These electronic components ensure the compatibility of the light-emitting diodes of the illuminant 10 with the ballast 60.

The alternative lamp ballast 60 of FIG 1B can be an electronic ballast, for example. Here the rectifier circuit, the first inductor 41 and the first capacitor 31 can be seen as part of the electronic ballast.

If the light source 10 in the alternative lamp were changed to light emitting diodes to provide an LED lamp, then the ballast 60 could destroy some of the light source 10 components. This is due to the fact that when the electronic ballast 60 is connected to the LED light source 10, it could skip the preheat mode and enter the ignition mode directly. By providing an LED lamp according to the present invention, the conventional fluorescent lamp 10 of the alternative lamp can be replaced with an LED light source 10 to provide an LED lamp as a retrofit for a fluorescent lamp without destroying the components of the LED lamp.

With reference to the 2 and 3 Embodiments of an LED lamp according to the present invention will be described in detail. In the configurations described, the LED lamp comprises a first control circuit, which is designed as a constant current circuit 61 (also called a constant sink current circuit).

The LED lamp has an illuminant 10 with light-emitting diodes 11, which is connected to a ballast 60 via a number of electronic components of a driver for the LED lamp. The ballast 60 can be a conventional ballast or an electronic ballast.

The ballast 60 is connected to the electronic circuitry of the driver through a plurality of resistors 70 connected in parallel. After the driver, a rectifier circuit with four diodes, i.e. a first diode 51, a second diode 52, a third diode 53 and a fourth diode 54, a smoothing capacitor 33 and a ground connection GND, ensures the correct polarity and frequency of the ballast 60 provided current and / or voltage.

The output of the rectifier circuit is applied to the constant current circuit 61 via a general connection 610 . The ballast 60 is also directly coupled to a detection circuit 64 . The detection circuit 64 provides a control signal depending on whether the ballast 60 is a conventional ballast or an electronic ballast. The output of the detection circuit 64 is transmitted to the constant current circuit 61 via a first connection 611 and a second connection 612 . A third connection 613 leads to a delay circuit 63 and a flyback controller 62 as further components of the driver. The output of the AC/DC controller 62 is then applied to the lamp 10 through a first transistor 21, such as an FET or a MOSFET, connected in series with a first resistor 71. In parallel with the components described above, the output of the ballast 60 can also be coupled to the lighting means 10 via a direct path.

The light source 10 is connected to an LC circuit with a first capacitor 31 and a second inductor 42 which, in combination with a further second inductor 42, forms a transformer. The transformer can convert a voltage supplied by the switched-mode power supply into an operating voltage for the light-emitting diodes 11 .

3 Fig. 12 shows the constant current circuit 61 and the AC/DC controller 62 in detail. Here a bus voltage U _B is applied to the electronic components on the rectifier circuit. The constant current circuit 61 and the flyback controller 62 include resistors, in particular a second resistor 72, a third resistor 73, a fourth resistor 74 and a fifth resistor 75. Further, the constant current circuit 61 and the flyback controller 62 include a fifth diode 55, the may be a Schottky or a Zener diode, and a second transistor 22. In particular, the flyback controller 62 may correspond to the fifth diode 55. Both the first transistor 21 and the second transistor 22 can be in the form of FETs or MOSFETs.

When the LED lamp is switched on, the detection circuit 64 determines what type of ballast 60 is connected to the LED lamp, for example by measuring the operating frequency ν. Then the control signal of the detection circuit 64 is provided to the constant current circuit 61 and the flyback controller 62 via the first connection 611 and the second connection 612 . In particular, the first transistor 21 is controlled by the detection circuit 64 . The first transistor 21 is activated only when the ballast 60 is an electronic ballast. In this case, the first transistor 21 operates in a constant current mode and the constant current switching circuit 61 is coupled between the ballast 60 and the light emitting diodes 11 .

The first transistor 21 is activated when the voltage at the input of the first transistor 21 reaches the threshold of the transistor. Then, a current flows through the first resistor 71. The gate voltage of the first transistor 21 is adjusted via the fifth diode 55, so that the first transistor 21 operates in a constant current mode. Further, it can allow the function of an AC/DC controller to be provided.

After the start-up sequence, the fifth diode 55 and/or the flyback controller 62 switch from the blocking mode to the conducting mode due to the voltage reduction in the circuit. This results in the activation, i.e. turning on, of the second transistor 22. The first transistor 21 and the second transistor 22 are connected in such a way that the second transistor 22 can turn off the first transistor 21 when the second transistor 22 is activated. Therefore, after the start-up sequence, the first transistor 21 is turned off and the first control circuit, i.e. the constant current circuit 61, is decoupled from the ballast 60 and the illuminant 10 with the light-emitting diodes 11.

If the ballast 60 is a conventional ballast, the first transistor 21 will not be activated, resulting in the constant current circuit 61 not being coupled to the ballast 60 and/or the light emitting diodes 11 .

The above-described configuration of the LED lamp according to the present invention allows not only reducing the starting voltage of an electronic ballast to prevent damage to the driver, but also easy control of the operating voltage, improved system efficiency, since the constant current switching circuit 61 does not have any additional losses in the Normal running mode generated after the start-up sequence, and a reduction in response time when the electronic ballast 60 is switched on or off quickly.

With reference to the 4 and 5 Embodiments of an LED lamp according to the present invention will be described in detail. In the configurations described, the LED lamp comprises a first control circuit, which is designed as a suppression circuit 65 .

As before, the driver of the LED lamp comprises a rectifier circuit with four diodes 51,52,53,54.

Furthermore, the detection circuit 64 is coupled to the ballast 60 and the suppression circuit 65 , with a first connection 651 and a second connection 652 leading to the suppression circuit 65 . The third connection 653 forms an output of the suppression circuit 65, which leads to the illuminant 10 with the light-emitting diodes 11, the first capacitor 31 and the second inductor 42, which in turn forms a transformer with a further second inductor 42. The circuitry of the light source 10 may also include a resistor 70 and a diode 50 to further adjust the current and/or voltage supplied to the light emitting diodes 11 .

A common connection 650 connects the suppression circuit 65 to the AC/DC controller 67 via the further second inductor 42, a transistor 20 and a resistor 70. The transistor 20 can have the function of a flyback circuit, in particular in combination with that provided by the Inductors 42 formed transformer. Furthermore, a feedback circuit 66 is connected to the AC/DC controller 67 and the circuit of the light source 10, so that the operating voltage of the light-emitting diodes 11 can be optimized.

5 shows the suppression circuit 65 according to FIG 4 detailed. Not all electronic components are here 4 shown in detail.

The suppression circuit 65 comprises a first resistor 71, a second resistor 72, a third resistor 73, a fourth resistor 74 and a fifth resistor 75. Further, the suppression circuit 65 comprises a first transistor 25 and a second transistor 26, a second capacitor 32 and a sixth diode 56. The sixth diode 56 can be a Zener diode or a Schottky diode, for example. The third resistor 73 is connected in parallel with the second capacitor 32 which in turn is connected in parallel with the sixth diode 56 . The output of this parallel circuit is then coupled to a seventh diode 57 which applies the output to third connector 653 . The latter output is then coupled to the starting circuit 621 via an eighth diode 58 and fifth resistor 75 . Coupling to ground GND is provided via fourth resistor 74 and second transistor 26 .

If the LED lamp is connected to an electronic ballast, then the second transistor 26 is switched off by the control signal provided by the detection circuit 64, ie deactivated. Therefore there is no connection to ground GND. A rising voltage provided by the electronic ballast during the starting sequence activates the first transistor 25. The output current of the electronic ballast thus flows to the light-emitting diodes 11, the first capacitor 31 and, if necessary, to the diode 50, which is connected in parallel with the light-emitting diodes 11 (see 4 ). The high voltage is then suppressed by the load on the electronic components.

The build-up current at the third connection 653 flows through the eighth diode 58 into the start-up circuit 621. This allows to prevent or at least reduce flashing of the light-emitting diodes 11 during the start-up sequence due to low voltage in the main circuit in the pre-heating process.

After the end of the start-up of the main circuit, the entire circuit switches to a low-impedance mode, which causes the input voltage to be lower than the operating voltage of the light-emitting diodes 11, resulting in the first transistor 25 being deactivated. The suppression circuit 65 therefore stops working and is decoupled from the ballast 60 and from the light-emitting diodes 11 .

If the ballast 60 is a conventional ballast, then the second transistor 26 is activated and the suppression circuit 65 is coupled to ground GND. The suppression circuit is therefore not coupled between the ballast 60 and the light emitting diodes 11 . As in 4 shown, the output of the ballast 60 is then transmitted via the other components, in particular the transformer, through the second inductors 42 directly to the light-emitting diodes 11 .

The in the 4 and 5 The configurations of the LED lamp shown offer improved compatibility of the LED lamp with an electronic ballast. In particular, the ignition voltage is reduced and high voltages generated by the electronic ballast are suppressed. Furthermore, the reliability of the driver circuit is improved due to the use of robust and reliable electronic components. In the run mode after the start-up sequence, or if the ballast 60 is a conventional ballast, the suppression circuit 65 does not consume power.

With reference to the 6A and 6B an exemplary embodiment of an alternative LED lamp is described in detail. The alternative LED lamp does not include a first control circuit 61, 65 according to the present invention. Instead, a first resistor 71 is connected in parallel with the starting capacitor of the ballast 60 . This first resistor can reduce the ignition voltage during the start-up sequence because it shifts the resonant frequency of the LC circuit of the lamp 10 to lower frequencies.

This can be omitted 6B See where simulated voltage drops (in arbitrary units au) versus operating frequency ν (in arbitrary units au) are plotted. Here are a first curve 81, a second curve 82, a third curve 83, a fourth curve 84, a fifth curve 85 and a sixth curve 86 for a value of the first resistor 71 of 200Ω, 400Ω, 600Ω, 800Ω , 1000Ω and 800kΩ shown.

An increase in the value of the first resistor 71 leads to a larger shift in the resonance frequency, so that the ignition voltage can be lowered. However, the first resistor 71 leads to high losses in the system and reduces the system efficiency.

With reference to the 7A , 7B , 7C , 7D , 8A , 8B and 8C configurations of an LED lamp according to the present invention will be explained in detail. Here are Measurements of ECG output voltages 91, LED driver output currents 92, current flow 93 through the constant current circuit 61, and LED driver input currents 94 are shown. The ECG output voltage 91 can correspond to the LED input voltage after the rectifier bridge circuit. the 7A , 7C and 8A show measurements for an LED lamp without a first control circuit 61, 65 according to the present invention, the 7B and 7D show measurements for an LED lamp with a first control circuit according to the embodiment of FIG 2 and 3 and the 8B and 8C show measurements for an LED lamp with a first control circuit 65 according to the embodiment of FIG 4 and 5 .

For the measurement of 7A , 7C and 8A was an electronic ballast (ECG) with an LED lamp without a first control circuit 61, 65 as in connection with the 2 until 5 explained connected. Here different types of electronic ballasts for the measurements of the 7A , 7C and 8A chosen (Osram QT-FIT 5/8 1X18-39 for 7A , Osram QT-FIT8 1X18 for 7C , Osram QT FIT 5/8 1X54-58 for 8A ). The electronic ballast was then switched on and off very quickly so that the preheating period was skipped by the electronic ballast and the ECG output voltage 91 was measured. The electronic ballast offers a high output voltage of up to 588 V ( 7A ), up to 606V ( 7C ) or up to 605 V ( 8A ).

For the measurements of 7B and 7D became a first control circuit configured as a constant (sink) current circuit 61 as with reference to FIG 2 and 3 explained, each with the electronic ballast of 7A and 7C tied together. The lower part of 7B and 7D each shows an enlargement of the measurement during the time of the start sequence t _z . The electronic ballast was again switched on and off rapidly and the preheating period was skipped. The current flow 93 through the first transistor 21 and thus the constant current switching circuit 61, the LED driver output current 92 and the ECG output voltage 91 were measured. The ECG output voltage 91 is set to a maximum of 210 V ( 7B ) or 284V ( 7D ) by the constant current circuit 61 is reduced. During the start sequence t _z the current flow through the constant current circuit 61 increases because the constant current circuit 61 is coupled between the electronic ballast and the light emitting diodes 11 of the LED lamp during the start sequence t _z . The LED driver output current 92 is relatively constant during the start-up sequence t _z . After the start-up sequence t _z , when the driver enters normal running mode, the LED driver output current 92 increases and reaches a stable value.

For measuring the 8B and 8C is a first control circuit, which as a suppression circuit 65 as in connection with the 4 and 5 is designed explained, during the start sequence t _z connected to the electronic ballast. In 8B only the start sequence is measured. In 8C the electronic ballast is quickly switched on and off. The lower part of 8C shows an enlargement of the measurement during the time of the start sequence t _z . Here the ECG output voltage 91, which corresponds to the LED driver input voltage after the rectifier bridge circuit, and the LED driver input current 94 flowing through the light emitting diodes 11 were measured. The maximum voltage is set to 114.7 V ( 8B ) or 135, 9 v ( 8C ) reduced.

The invention is not limited by the description based on the embodiments. Instead, the invention encompasses all new features and also any combination of features, including in particular any combination of features in the patent claims, even if this feature or this combination itself is not expressly stated in the patent claims or in the exemplary embodiments.

Reference List

10

bulbs

100

preheat mode

101

ignition mode

102

post-ignition mode

103

running mode

11

led

14

first exemplary voltage drop

15

second exemplary voltage drop

20

transistor

21:25

first transistor

22.26

second transistor

31:32

first and second capacitor

33

smoothing capacitor

41.42

first and second inductor

50

diode

51, 52, 53, 54, 55, 56, 57, 58

first, second, third, fourth, fifth, sixth, seventh, eighth diode

60

ballast

61

constant current circuit

610,650

general connection

611,651

first connection

612,652

second connection

613,653

third connection

62

flyback controller

621

starting circuit

63

delay circuit

64

detection circuit

65

suppression circuit

66

feedback circuit

67

AC/DC controller

71,72,73,74,75

first, second, third, fourth and fifth resistance

81,82,83,84,85,86

first, second, third, fourth, fifth and sixth curve

91

ECG output voltage

92

LED driver output current

93

Current flow through constant current circuit

94

LED driver input current

v

operating frequency

UB

bus voltage

GND

Dimensions

tZ

start sequence

Claims (9)

LED lamp for mounting in a fluorescent lamp socket with a ballast (60), the LED lamp comprising: - several light-emitting diodes (11), - a detection circuit (64) adapted to generate a control signal indicative of whether the ballast (60) is a conventional ballast or an electronic ballast, and - a first control circuit (61, 65) adapted to couple between the lamp socket ballast (60) and the light emitting diodes (11) during a start sequence of the ballast (60) in response to the control signal, - wherein the first control circuit (61, 65) stabilizes a voltage drop across the light emitting diodes (11) during the starting sequence, and wherein an impedance between the ballast (60) of the lamp socket and the light emitting diodes (11) is controlled by the first control circuit (61, 65) is increased during the starting sequence, wherein the first control circuit (61, 65) comprises a first transistor (21, 25) activated during the starting sequence and a second transistor (22, 26) deactivated during the starting sequence, and wherein the first transistor (21, 25) and the second transistor (22, 26) are connected such that the second transistor (22, 26) can turn off the first transistor (21, 25) when the second transistor (22, 26) is activated. led lamp after claim 1 wherein the first control circuit (61, 65) is coupled between the ballast (60) of the lamp socket and the light emitting diodes (11) only in the case where the ballast (60) is an electronic ballast. led lamp after claim 1 comprising a main control circuit adapted to be coupled between the light emitting diodes (11) and the ballast (60) of the lamp holder after the starting sequence and/or if the ballast (60) is a conventional ballast. The LED lamp according to the preceding claim, wherein the first control circuit (61, 65) speeds up a start of the main control circuit. LED lamp according to the previous claim, wherein the first control circuit (61, 65) is coupled to a flyback controller (62) which is coupled to an output of the first transistor (21, 25). led lamp after claim 1 wherein the first control circuit (61, 65) is decoupled from the light emitting diodes (11) and the ballast (60) of the lamp socket after the starting sequence. led lamp after claim 1 , wherein the first control circuit (61, 65) is a constant current circuit (61). led lamp after claim 1 , wherein the first control circuit (61, 65) is a suppression circuit (65). led lamp after claim 1 wherein the detection circuit (64) determines an operating frequency of the ballast (60) of the lamp socket to provide the control signal.

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