EP2189045B1 - Improved applicability of lamps with electronic ballast without a protective earth conductor - Google Patents

Abstract

The invention relates to improving the electromagnetic compatibility for lamps with integrated electronic ballast which are operated without a protective earth supply line, and involves capacitively coupling the electronic ballast housing to insulated conductive parts of the lamp by means of a capacitor (C3), possibly in conjunction with a further capacitor (C1) for fixing the touch voltage, and a radio frequency-absorbing damping element (F).

Description

Technical area

The present invention relates to lights with integrated electronic ballast (ECG).

State of the art

The term "luminaire" means a lighting device which is designed for the installation of a lamp or which is already a built-in lamp and which encloses beyond the lamp a housing, a frame or a reflector for the lamp and a connection terminal for the mains conductors. The term "lamp" in turn here means the light source, such as a discharge lamp or a halogen incandescent lamp or even an LED or an LED module.

In this case, the invention relates only to such lights that include an integrated electronic ballast with protective ground connection. If such luminaires are operated without the supply of a protective earth (PE conductor), they may have reduced electromagnetic compatibility (EMC) or increased contact voltages, or the ECG may malfunction.

From the Scriptures EP 1 100 292 A It is known to connect the metallic reflector of a luminaire by means of a Y-capacitor with a lamp supply line.

continues from the Scriptures WO 93/20677 A It is known to connect the protective earth connection of the electronic ballast via a respective capacitor to the two mains supply lines.

Finally, from the Scriptures EP 0 267 129 A1 known to connect the power supply lines via a plurality of capacitors with an inner reference ground.

Presentation of the invention

The object of the invention is to provide a luminaire which, even if it is operated without a protective earth lead, offers improved usability in terms of EMC or contact voltages.

The problem is solved by a luminaire with an integrated, a protective ground connection having electronic ballast and a light terminal AK without protective earth terminal of the lamp itself, characterized by a built-in the lamp terminal first capacitor C3, the at least one conductive insulated part of the lamp MP to the ground terminal PE the electronic ballast connects.

As a precaution, it is stated that the disclosure also refers to a method for operating such a luminaire and that the various features are also to be regarded as disclosed for the method category, without explicitly distinguishing between device and method categories below.

Preferred embodiments are specified in the dependent claims.

Namely, the inventors have recognized that parasitic capacitances of conductive, isolated from operating voltages and currents parts of the lamp, for example, conductive housing parts, metallic reflectors or mounting plates of the lamp housing, a coupling to operating current leading lines within the lamp. This coupling can reduce the EMC of the luminaire with respect to noise immunity and interference emission and also enable the generation of contact voltages of up to several hundred volts. Both lead to problems with compliance with the corresponding standards. In addition, the inventors have realized that it is in the ECG by coupling voltage spikes in the circuit electronics, in particular of integrated circuits, may malfunction during operation.

The idea on which the invention is based is to produce a connection which conducts high-frequency alternating currents between conductive insulated luminaire parts, in particular housing or mounting parts, and the protective ground connection of the ballast by means of a capacitor. High-frequency common-mode noise, which originates in the high-frequency generator of the electronic ballast, for example, shorts this capacitor. In this case, the galvanic separation of housing or mounting parts and live cables within the lamp is not canceled and are not affected by the optional use of a special type of capacitor double or reinforced insulation.

The potential difference of these parts and the protective earth is hereinafter referred to as touch voltage, regardless of whether the parts are actually touched during operation. The contact voltage can be fixed by means of one or more additional capacitors between the luminaire part and one or both power lines. For this purpose, the lighting part in question can be additionally connected to the phase conductor (L-conductor) or the neutral conductor (N-conductor), for example, by means of only one further capacitor. In another variant of this idea, L and N conductors are connected by two further capacitors connected in series, wherein the relevant luminous part is additionally connected to the common point of the capacitors.

The capacitors used preferably have a dielectric strength in the range of a few kilovolts and will not lose their insulating capability even in the case of a malfunction. These conditions are met, for example, by capacitors of the type 'Y' known from the prior art. Their capacity should be small enough to ensure a sufficiently small contact current during normal operation. The capacitance of the capacitors is in this case down through the values 10pF, 100pF and 500pF, the larger, the more preferred, and upwardly limited by the values 5nF, 10nF, 22nF, the smaller, the more preferred. Ideally, in many applications, the capacity is in the range of about 2nF.

The capacitor according to the invention or the capacitors according to the invention are used in luminaires, which are designed for operation without PE supply line. However, the terminal in which the capacitors are integrated can have not only two (for N and L conductors), but also three terminal contacts (for N, L and PE conductors). It is conceivable that the manufacturer, although the operation without PE supply line provides (and the lighting protection concept is designed accordingly), but for cost reasons, to simplify production, or installed to loop through the PE conductor to other consumers a terminal with three terminal contacts , wherein the PE contact inside lights then not further interconnected. In this case, there would be three terminal contacts, the PE contact does not form a protective contact of the lamp itself.

Furthermore, the inventors have recognized that in the circuit for fixing the contact voltage by the inductors the power lines resonantly excessive high-frequency alternating currents in a capacitive connection according to the invention between the luminaire part and the one or more power lines can occur.

A further embodiment of the Berührspannungsfixierungsschaltung therefore provides to suppress high-frequency radiation absorption high-frequency currents in a line between the one or more power conductors and the respective lighting part. For this purpose causes a damping element by material-specific high-frequency damping properties in the relevant frequency range high-frequency radiation losses and thus reduces the amplitude of alternating currents corresponding frequencies. In particular, materials with suitable magnetic properties that can be attenuated by magnetic HF losses come into consideration as attenuation element. Ferromagnetic ceramics, which are known as damping ferrites, in particular also iron oxide, are particularly suitable for this purpose.

The damping element should preferably not be integrated into current-carrying conductors themselves, but should be attached only in their vicinity. Preferably, the damping element surrounds the conductor by being a body with a passage opening. Particularly suitable are so-called pearls, ie small spheroidal bodies with a bore, rings or small tubes.

Experience also shows that when switching on powered by electronic ballasts lamps can lead to relatively high inrush currents, especially when the ballasts input side relative have large capacitors. Such capacitors are common in many ballast types, for example, as a DC link capacitor. The inrush current peaks lead to loads on the components affected by the current peaks and can also trigger fuses, in particular if several ballasts with such properties are operated together on a fuse. This means that the inrush current peaks which are meaningless for technical continuous operation can considerably reduce the number of ballasts that can be operated together on one fuse.

On the other hand, the production of ballasts and lights is under significant cost pressure, so that additional measures to limit the current, such as power factor correction circuits with inherent current limiting function, in many cases are practically out of the question.

As a further embodiment, the circuit according to the invention is therefore combined with an inrush current limiting circuit. The inrush current limiting circuit is defined in the most general sense that when it is switched on in the switch-on phase, it first generates a voltage drop in the line in which the inrush current would otherwise occur, and this voltage drop then disappears relatively quickly, for instance within a time of at most 500 ms or significantly decreases.

In a concrete embodiment of the inrush current limiting the voltage drop can be generated via an open additional switch in the line, which is closed only delayed, in the area small instantaneous values of the applied supply voltage and preferably at the voltage zero crossing. When supply of the ballast is started with small or even near zero supply voltage values, the inrush current is limited and, in particular, capacitors in the ballast can be charged without problems due to the small supply voltage values.

In another embodiment, the voltage drop in the inrush current limiting circuit is generated by a first high resistance in the line, in which otherwise the inrush current would occur. Also, this resistance should then disappear in a relatively short time, such as the highest 500 ms, or decrease by a factor of at least 50. The initial resistance to inrush current limiting depends on the wiring and may be in the range of 50 Ω to 1 kΩ, for example.

A favorable possibility for realizing the inrush current limitation exists, for example, in a thermistor or "NTC"("Negative Temperature Coefficient", ie resistance element with increasing temperature as the temperature increases). When switching on, the thermistor is initially still cold or room warm and thus relatively high impedance. The current can be limited to acceptable levels, but heats up the thermistor relatively quickly and thus transferred him to a much lower impedance state. In continuous operation, the low power loss in the thermistor suffices to maintain a sufficiently low resistance value therein. Here, if necessary, depends on the thermal ambient conditions, the type of thermistor and the load current to set a suitable temperature and resistance balance.

Another realization possibility of the inrush current limiting circuit is a relay with a resistor connected in parallel. The resistor initially, with the relay open, the initial current limit. The relay can either be closed by a separate timer circuit and then bypasses the resistor (or can be closed by the applied voltage and a time delay element) or can also be controlled directly by the applied voltage and then closes with a relay typical time delay. So you can depend on the technical data of the relay used, d. H. its design-related pull-in delay, add another timer or delay circuit or not.

An advantage over the variant described above is that the resistance value can be particularly low in continuous operation and the resistance value at the inrush current limit is freely adjustable. Furthermore, there are no thermal inertia as in thermistors, so that even fast off and restart operations are unproblematic.

An alternative to the described combination of relay and resistor consists in a timed switching transistor with a resistor connected in parallel. In contrast to the "classic" relay, the switching transistor is practically wear-free. The in principle more complex circuit structure does not necessarily have to result in a higher price.

Instead of the switching transistor, it is also possible to use a thyristor, TRIAC or IGBT, which is triggered or switched on time-controlled after switching on and thus becomes low-impedance.

The timing of the two variants described above can be realized via an RC element, but can also be made in an advantageous manner by a microcontroller already provided in many modern electronic ballasts or another electronic control of the ballast.

Finally, an inrush current limit can be effected via the controlled delayed switching on of a transistor. This controlled turn on may mean a timed slow turn on. "Slow" here means that the transistor reaches its full conductivity during the switch-on process over a period of a few 10 ms. For this purpose, the transistor, such as a MOSFET, is controlled according to time. The parallel resistor can therefore also be omitted if the switching transistor is sufficiently strong.

Preferably, however, an additional circuit is provided between a control terminal of the transistor and a further one of its terminals, which controls the control of the control terminal in response to the current to be limited by the transistor, thus in particular limits the potential at the control terminal. Such a circuit then limits the power in the switch-on, in which otherwise current peaks would occur through the transistor by not completely closing it. After completion of the actual turn-on, when no inrush peaks are to be feared more, the circuit may preferably turn on the transistor completely, but this is not absolutely necessary. For the rest, reference is made to the explanations of the exemplary embodiments.

Finally, it is advantageous if a thermal fuse is provided. This may be a simple fuse or other thermally triggered fuse. This can prevent the components according to the invention from causing a hazard in the case of a short circuit in the ballast.

In all variants of the invention, it is generally preferred, in addition to the capacitor / capacitors according to the invention optionally integrate the damping element / the damping elements or optionally the inrush current limiting circuit in the terminal. The term "integrated in" here means that the components should be contained or held in the terminal including its insulating support, so that they can be mounted together with and in the terminal by the luminaire manufacturer or ballast manufacturer and possibly even already be purchased.

The integration of the circuits according to the invention in the terminal has the advantage that the applicability of the lighting device in a particularly simple manner and without interfering with the actual circuit of the ballast, can be improved. The terminal provided with the circuits can be manufactured as a separate part and used in a otherwise unchanged technical environment. In particular, there is no need for the manufacturer to provide additional protective circuits in the electronic ballast and line filter. These measures always mean a high overhead.

Thus, the advantages of an unchanged series production of the ballasts or lights can be combined with a simple and pragmatic solution to improve the EMC or Berührspannungsfixierung the Berührspannung or for inrush current limit.

Particularly advantageous embodiments can be found in the dependent claims.

Short description of the drawing

• Fig. 1 zeigt ein schematisches Schaltdiagramm einer Leuchte mit zwei Y-Kondensatoren als erstes Ausführungsbeispiel.
• Fig. 2 zeigt ein schematisches Schaltdiagramm einer Leuchte mit drei Y-Kondensatoren als zweites Ausführungsbeispiel.
• Fig. 3 zeigt ein schematisches Schaltdiagramm einer Leuchte mit zwei Y-Kondensatoren und einem Dämpfungselement als drittes Ausführungsbeispiel.
• Fig. 4 zeigt ein schematisches Schaltdiagramm einer Leuchte nach Fig. 3 mit einem Heißleiter zur Einschaltstrombegrenzung als viertes Ausführungsbeispiel.
• Fig. 5 zeigt ein schematisches Schaltdiagramm einer Leuchte nach Fig. 3 mit einem Thyristor und Parallelwiderstand zur Einschaltstrombegrenzung als fünftes Ausführungsbeispiel.
• Fig. 6 zeigt ein schematisches Schaltdiagramm einer Leuchte nach Fig. 3 mit einem Schalttransistor und Parallelwiderstand zur Einschaltstrombegrenzung als sechstes Ausführungsbeispiel.
• Fig. 7 zeigt ein schematisches Schaltdiagramm einer Leuchte nach Fig. 3 mit einem Relais und Parallelwiderstand zur Einschaltstrombegrenzung als siebtes Ausführungsbeispiel.
• Fig. 8 zeigt ein schematisches Schaltdiagramm einer Leuchte nach Fig. 3 mit einem linear betriebenen MOSFET zur Einschaltstrombegrenzung als achtes Ausführungsbeispiel.
• Fig. 9 zeigt ein schematisches Schaltdiagramm einer Leuchte mit einem Mikrocontroller als Ansteuerungsquelle für einen Schalttransistor zur Einschaltstrombegrenzung als neuntes Ausführungsbeispiel.
• Fig.10 zeigt ein schematisches Schaltdiagramm einer Leuchte nach Fig. 3 mit getaktet betriebenem MOSFET und einer Glättungsschaltung zur Einschaltstrombegrenzung als zehntes Ausführungsbeispiel.
• Fig.11 zeigt ein schematisches Schaltdiagramm einer Leuchte nach Fig. 3 mit spannungsabhängig geschaltetem MOSFET zur Einschaltstrombegrenzung als elftes Ausführungsbeispiel.
• Fig.12 zeigt Strom- und Spannungszeitverlaufsgraphen bei einer Leuchte ohne erfindungsgemäße Einschaltstrombegrenzungsschaltung.
• Fig.13 zeigt Strom- und Spannungszeitverlaufsgraphen bei einer Leuchte mit erfindungsgemäßer Einschaltstrombegrenzungsschaltung

Incidentally, the invention is explained in more detail on the basis of exemplary embodiments, the disclosed individual features also being essential to the invention in other combinations, and the description having only an exemplary character, that is, not restricting the subject matter of the invention.

• Fig. 1 shows a schematic circuit diagram of a lamp with two Y-capacitors as a first embodiment.
• Fig. 2 shows a schematic circuit diagram of a lamp with three Y-capacitors as a second embodiment.
• Fig. 3 shows a schematic circuit diagram of a lamp with two Y-capacitors and a damping element as a third embodiment.
• Fig. 4 shows a schematic circuit diagram of a light after Fig. 3 with a thermistor for inrush current limiting as a fourth embodiment.
• Fig. 5 shows a schematic circuit diagram of a light after Fig. 3 with a thyristor and parallel resistor for inrush current limiting as a fifth embodiment.
• Fig. 6 shows a schematic circuit diagram of a light after Fig. 3 with a switching transistor and shunt resistor for inrush current limiting as the sixth embodiment.
• Fig. 7 shows a schematic circuit diagram of a light after Fig. 3 with a relay and parallel resistor for inrush current limiting as the seventh embodiment.
• Fig. 8 shows a schematic circuit diagram of a light after Fig. 3 with a linearly operated MOSFET for inrush current limiting eighth embodiment.
• Fig. 9 shows a schematic circuit diagram of a lamp with a microcontroller as a driving source for a switching transistor for inrush current limiting as a ninth embodiment.
• Figure 10 shows a schematic circuit diagram of a light after Fig. 3 with clocked MOSFET and a smoothing circuit for inrush current limiting as tenth embodiment.
• Figure 11 shows a schematic circuit diagram of a light after Fig. 3 with a voltage-dependent switched MOSFET for inrush current limiting as eleventh embodiment.
• Figure 12 shows current and voltage waveforms in a luminaire without inrush current limiting circuit according to the invention.
• Figure 13 shows current and voltage waveforms in a luminaire with inventive inrush current limiting circuit

Preferred embodiment of the invention

In FIG. 1 is shown in the context of a highly schematic block diagram, the interconnection of a circuit according to the invention in a lamp. On the left is a designated "network" power connection with phase conductor L and neutral N, which is led via a not more isolated supply line to a light terminal AK. The luminaire connection terminal AK is a uniform plastic housing - represented by the rectangle - with known built-in terminal contacts for the lines L and N, but without PE connection contacts. The capacitors C1 and C3 are Y capacitors having a capacity of 2.2nF and 1.5nF, respectively. The protective earth terminal PE of the electronic ballast is connected via the capacitor C3 to an insulated conductive luminaire part MP, such as a housing earth terminal contact, a metallic one Reflector or a mounting plate or plate connected. Both capacitors are mounted in the luminaire connection terminal. The line between the capacitor C3 and the mounting plate MP may for example consist of a wire bridge. The capacitor C1 connects the mounting plate MP and the phase conductor L. However, the capacitor C1 can also be readily inserted between the mounting plate MP and the neutral conductor N. Im in Fig. 1 In the case illustrated, the potential of the mounting plate MP is RF-technically fixed at the mains voltage potential. However, the capacitor C1 could also connect the protective earth terminal PE itself to the phase conductor L or the neutral conductor N. For dimensioning the capacitance of the capacitor C1, it should be noted that the capacitor C1 represents a high impedance on the one hand for possible contact currents generated, for example, by touching the mounting plate MP, and on the other hand for HF interference currents. This ensures that line currents supplied by the grid can not exceed tolerable or standard values and that HF interference currents are short-circuited. This condition is easy to fulfill because the grid potential on the time scale of the RF disturbances is quasi static.

FIG. 2 shows a modification of the circuit arrangement in FIG. 1 , Another in the terminal integrated Y-capacitor C2, whose capacity preferably corresponds approximately to that of the capacitors C1 or C3 and which preferably not more than 50% from that of the capacitor C2 and ideally is equal to that of the capacitor C2, connects the mounting plate MP with the neutral conductor N. If the capacitance of the capacitor C1 is equal to that of the capacitor C2, then the potential is the same the mounting plate MP fixed at half the mains voltage potential. However, a common point to the capacitors C1 and C2 could also be contacted between the capacitor C3 and the protective earth terminal PE itself. The capacitors C1 and C2 not only cause a Berührspannungsfixierung, but they also allow the neutralization of symmetrical interference voltages and act effectively as a line filter.

FIG. 3 indicates by analogy Fig. 1 According to the invention in the lamp terminal integrated Y-capacitors C1 and C3 and a damping element, in this case, a ferrite bead F. The capacitors and their arrangement correspond to those in Fig. 1 illustrated situation. The ferrite bead F is seated on a terminal-internal line piece, which connects the mounting plate MP with the capacitor C1. In the same way, however, it could also be mounted inside the terminal between the capacitor C1 and the phase conductor L. As in the text too Fig. 1 already mentioned, the capacitor C1 could as well connect the neutral conductor N to the mounting plate MP instead of the phase conductor L or one of the power conductors to the protective ground connection PE.

The attenuation element F attenuates by high-frequency radiation absorption resonant high-frequency alternating currents arising from parasitic inductances of the power conductor in conjunction with the capacitive coupling of conductive light parts to the mentioned light-internal current-carrying conductor. In a circuit arrangement according to Fig. 2 could a ferrite bead according to the invention on a terminal internal line piece between the common point of the capacitors C1 and C2 and the mounting plate MP on the one hand or the protective earth terminal PE on the other hand or, in each case, there could be a damping element between the common point of the capacitors C1 and C2 and the capacitor C1 on the one hand and the capacitor C2 on the other hand or between the capacitor C2 and the neutral conductor N and the capacitor C1 and the phase conductor L. In the latter case Thus, the circuit would have two damping elements.

Fig. 4-11 show embodiments with inrush current limiting circuits. To the capacitors C1 and C3 and the damping element F in the Fig. 4-11 is in each case to the description too Fig. 3 directed.

In FIG. 4 is a NTC NTC as inrush current limiting circuit connected in the phase line L. When switching on, the voltage applied to phase L is suddenly applied to the thermistor NTC and, via it, due to its residual conductivity, to the electronic ballast. At the ECG input there is a diode rectifier bridge, via which a DC link capacitor (not shown) is charged for the DC voltage supply of a converter of the ECG. The initially high-resistance thermistor NTC does not permit large charging currents, so that the charging process of the DC link capacitor in the ECG is somewhat delayed. Meanwhile, the appropriately sized NTC thermistor is heated sufficiently to pass into a low resistance state. This completes the charging process and, moreover, the ballast and lamp operation is as usual.

The residual resistance of the NTC thermistor does not play a significant role in this embodiment. After switching off, wait a sufficient amount of time until the thermistor NTC has cooled down before the protective function is available again. However, this disadvantage is tolerable in many cases, at least if a quick off and reconnect only affects a ballast or a small number of ballasts on a common fuse.

FIG. 5 shows a fifth embodiment and corresponds largely FIG. 4 , Here, the NTC thermistor is replaced by an in detail shown inrush current limiting circuit. This circuit has a built-up of four diodes D1-D4 rectifier bridge. Between the two nodes of the bridge, which do not coincide with the phase leads or leads, there is a resistor R and, in parallel thereto, a thyristor Thy polarized in the same sense as the diodes D1-D4. Instead, a TRIAC or IGBT could be chosen as well. The thyristor Thy is controlled by a symbolically represented by a timing diagram timing circuit, which can be realized by a simple RC element. In both polarity-different half phases of the phase L, the resistor is in the current path to the ECG shortly after switching on and before the ignition of the thyristor Thy. When the thyristor Thy is ignited, it short-circuits the resistor R as a result of its conductive state, thus ending the inrush current limitation. S denotes a likewise integrated thermal fuse.

Both embodiments relate to a lamp terminal AK. However, they can also be easily transferred to an ECG connection terminal. For this you have to use the terminal AK only as an integral part of the Introduce ECG. This ballast terminal could then be connected via a separate line to a light terminal or even already form the light terminal.

FIG. 6 shows a sixth embodiment, compared to the fifth embodiment of FIG. 5 is modified insofar as there is instead of the thyristor, a switching transistor, namely a power MOSFET M, use. The source, gate and drain contacts are labeled S, G and D, respectively. Otherwise, the explanatory notes to FIG. 5 ,

FIG. 7 shows a seventh embodiment, which is easiest compared to FIG. 4 let explain. The NTC thermistor here is replaced by a common ohmic resistance R, which incidentally, as in the second and third embodiments, typically 220 Ω. The resistor R can be bridged by a classic Rel relay designated Rel, which is connected in the manner shown with its control contacts between the phase conductor L and the neutral conductor N and thus controlled by the switch-on. The marked with an X part of the relay is intended to symbolically stand for a pull-in delay, which is realized either due to design or by a delay circuit, such as an RC element.

FIG. 8 shows schematically a circuit in which a controlled turning on of a MOSFET T1 is used for inrush current limiting. L and N again designate phase and neutral; S again denotes an integrated thermal fuse. The MOSFET T1 is with The help of four rectifier diodes D5 - D8 is connected in the phase supply line L so that it always flows through the supply current with the correct polarity. Incidentally, the phase lead L and the neutral conductor N to one in the FIGS. 4 to 7 not shown separately common rectifier bridge of four rectifier diodes connected in the input of the ECG. The DC link capacitor of the electronic ballast is designated CL and represents here the input capacitance of the electronic ballast responsible for the inrush current peaks. R1 (for example 10 kΩ) designates an ohmic resistor, which is only symbolic here for the load formed by the electronic ballast.

FIG. 8 further shows that the gate of MOSFET T1 is connected to the neutral via two resistors R4 (about 1 kΩ) and R6 and a diode D9. The example here with 100 kΩ rated resistor R6 is used for potential separation and forms together with a capacitor CR of z. B. 3.3 μF a smoothing member. A resistor R7, for example of 1 MΩ, is used to discharge the capacitor C2 in the off state.

The supply current of the phase conductor L through the MOSFET T1 is passed through a small resistor R3 of, for example, 1 Ω to produce a proportional voltage drop. This voltage drop is used to monitor the gate voltage of MOSFET T1, via a bipolar (npn) transistor T2, its collector at the gate, its base at source and its emitter via another resistor R5 (about 22 Ω) and the mentioned resistor R3 is at its base and thus at the source terminal of the MOSFET T1.

Finally, the gate voltage is limited via a zener diode ZD with a threshold voltage of about 18V.

After switching on the phase at L, the capacitor CR is slowly charged via the resistor R6 and generates an increasing drive voltage for the gate of the MOSFET T1. As soon as a supply current begins to flow through the MOSFET T1 in its turn-on, a voltage drops across the resistor R3 which reduces the gate voltage of the MOSFET T1 when the emitter base threshold voltage of the bipolar transistor T2 is reached.

Thus, the increased internal resistance of the MOSFET T1 during the switch-on process can be used to limit the inrush current caused by the charging of the capacitor CL. As soon as the capacitor CL is charged to a considerable extent, the supply currents for the electronic ballast drop so much that no voltage sufficient for closing the bipolar transistor T2 drops across the resistor R3. In continuous operation, therefore, the bipolar transistor T2 remains open and thereby the MOSFET T1 can be completely closed by the voltage applied to the capacitor CR, in order not to generate unnecessary losses.

Incidentally, the emitter base threshold voltage of the bipolar transistor T2 of the order of 0.7 V is so small that the resistor R3 can be dimensioned correspondingly small and therefore low-loss.

In alternative embodiments having a similar function, the bipolar transistor could also be replaced by a zener diode having a correspondingly lower threshold voltage which, when turned on as a result of a voltage drop across the resistor R3, limits the gate voltage on the MOSFET T1. However, the threshold voltages necessary here would be greater than the emitter base threshold voltage of the bipolar transistor T2 and would thus lead to a slightly larger dimensioning of the resistor R3, that is, to somewhat greater losses.

Conversely, the circuit shown in FIG. 8 could also be designed to be more sophisticated by replacing the bipolar transistor T2 used here in the schematic diagram with a sense amplifier circuit with operational amplifiers. This would avoid variations in temperature response and specimen scattering and could further reduce the 0.7V threshold.

FIG. 9 shows another embodiment in which a MOSFET M as in FIG FIG. 6 instead of being controlled by the simple timer circuit shown there via a function of a microcontroller, which is present anyway in electronic ballasts in many cases and could thus obtain a connection to the gate terminal of the MOSFET M with negligible overhead. For ballasts without current limiting function, this connection would then remain functionless, so that nothing stands in the way of the modular use of terminals according to the invention. This is especially true in the integration of the terminal in the ballast. Incidentally, the thyristor can also off FIG. 5 be controlled in a corresponding manner via the microcontroller.

FIG. 10 shows another embodiment in which a MOSFET as in FIGS. 6 and 9 is controlled via a pulse width modulated PWM signal, ie clocked in time. Thus, an intermittent supply current is generated, which is converted by a serial smoothing circuit of an inductance L, a rectifier diode and a resistor R to a quasi-continuous current. The time constant resulting from L and R must therefore be adapted to the clock frequencies of the PWM signal. The diode corresponds to the polarity of the rectifier bridge D1 - D4. This embodiment shows that a controlled turn-on in the embodiment of FIG. 8 can also be implemented in a control technology digital manner, wherein in the embodiment in FIG. 10 is not turned off on the existing in the environment in the vicinity of the threshold voltage internal resistance of the MOSFET.

FIG. 11 shows a final embodiment, the commonality with the embodiments of FIG. 6 and FIG. 7 having. In relation to the embodiment of FIG. 6 the switching on of the MOSFET M is not delayed according to a predetermined timing scheme but in response to the detection of the voltage between phase L and neutral N. It is switched at the next possible voltage zero crossing, so that the charging process of the input capacitance of the ECG in consequence of initially rising only in small values Voltage without surges at problematic height. Therefore, the parallel-connected resistor R can be omitted and plays out in comparison with the embodiment FIG. 8 , the internal resistance of the MOSFET M in the switch-on also not essential.

FIG. 12 and FIG. 13 show in comparison the effect of the inrush current limiting circuits according to the invention by means of measurements. The horizontal axis in both cases shows the time scale from 0 to 90 ms. The vertical axis, plotted on the left, shows a voltage scale from -350 V to +350 V, and plotted on the right, a current scale from -100 A to +100 A in FIG. 9 and from -2 A to +2 A in FIG. 13 ,

The time at the beginning of the graph corresponds to the actual switch-on time. In FIG. 12 is this switch-on time (about 5 ms) chosen so that just a peak value of the phase L is reached, namely with just under 350 V. The voltage at the phase L oscillates sinusoidal. A sawtooth-like graph in the upper area, denoted by U _z , shows the voltage at the already mentioned intermediate circuit capacitor in the ECG. This is practically at the top of the supply voltage from the beginning and decays synchronously therewith as a result of the load within the ECG, to be recharged with each new phase L peak. The corresponding very fast charging of the DC link capacitor at the time of switch-on is reflected in a FIG. 12 practically infinitesimally short current pulse I, which immediately transitions into a current curve that remains practically at 0 on the scale shown. The initial inrush current is thus on the order of 100 A (it is in FIGS. 12 and 13 shown reversed in the sign so that it is visible next to the voltage curve L).

In contrast, shows FIG. 13 a much slower charging of the DC link capacitor. Also in the inventive variant in FIG. 13 the switch-on process takes place practically at the peak value of phase L (approximately at 5 ms). The slightly smaller triangle below the initial phase L triangle represents the first charging current pulse I. However, this is related to the vertical current scaling changed here and remains in the amplitude at less than 1.5 A. Synchronous to the sinusoidal oscillations of the phase L then follow in terms of amplitude and temporal extent slightly decreasing sinusoidal charging current pulses with much smaller current amplitudes. Approximately at 60 ms, the time signal corresponding to the fifth and the sixth embodiment takes place FIG. 5 or 6 (or would the thermistor NTC off FIG. 4 sufficiently warm or the Relay Rel off FIG. 7 switched on). This is in FIG. 13 shown at the bottom by the rectangular rising curve. As a result, the charging current peaks become larger again in amplitude owing to the inrush current limiting resistor R which now disappears, but due to the increasing charging of the DC link capacitor, which is increasing independently of the switching process, is consistently shorter in time. They stabilize at an amplitude of well below 1 A, cf. the right half of the FIG. 13 , The voltage curve U _z therefore shows the sawtooth curve in the right half FIG. 12 , in the left half of the FIG. 13 however, a rise modulated with the same period and otherwise smeared over the already mentioned time of 60 ms. With the invention, the full DC link capacitor voltage is therefore delayed by a few 10 ms, however, the inrush current peaks can be reduced by almost a factor of 100 in this case.

Claims (22)

1. Lamp with integrated electronic ballast (EVG) having a protective earth connection and a lamp connection terminal (AK) without a protective earth connection of the lamp itself, characterised by a first capacitor integrated into the lamp connection terminal (C3) which connects at least one conducting insulated part of the lamp (MP) to the protective earth connection (PE) of the electronic ballast.
2. Lamp according to claim 1 with a second capacitor (C1), which connects one of the group comprising lamp part (MP) and protective earth connection (PE) with one of the group comprising phase conductor (L) and neutral conductor (N).
3. Lamp according to claim 2 with a third capacitor (C2) between the side of the second capacitor (C1) facing away from the network and that network supply line that is not connected to the second capacitor (C1).
4. Lamp according to one of the preceding claims, in which the capacitor/the capacitors (C1, C2, C3) have capacitance values between 10pF and 22nF.
5. Lamp according to claim 3 or 4, in which the second and the third capacitor (C1, C2) have the same capacitance.
6. Lamp according to one of the preceding claims, in which the lamp connection terminal (AK) does not have a connection terminal contact for a PE conductor.
7. Lamp according to one of the preceding claims, in which the conducting insulated part of the lamp (MP) is a fitting panel.
8. Lamp according to one of claims 2 to 7 with an attenuation element (F) consisting of high-frequency-absorbing material and designed, by absorbing high-frequency radiation, to attenuate high-frequency currents in a line of the lamp containing at least one of the group comprising second capacitor (C1) and third capacitor (C2).
9. Lamp according to claim 8, in which the attenuation element (F) features a high-frequency-absorbing ferrite.
10. Lamp according to claim 8 or 9, in which the attenuation element (F) is a closed body around a through-opening and the line in which the high-frequency currents are to be attenuated runs through the through-opening.
11. Lamp according to one of the preceding claims with an inrush current limiting circuit (NTC, D1-D4, R, Thy, M, Rel, L, T1, T2, R1-R7, ZD, CR) which is designed so that when the lamp is switched on, inrush currents that are too high are prevented by a voltage drop in the inrush current limiting circuit (NTC, D1-D4, R, Thy, M, Rel, L, T1, T2, R1-R7, ZD, CR) during the switch-on phase.
12. Lamp according to claim 11, in which the inrush current limiting circuit has a voltage monitoring circuit and a controllable switch and is designed only to close the controllable switch in a voltage zero crossing after the lamp has been switched on.
13. Lamp according to claim 11, in which the inrush current limiting circuit (NTC, D1-D4, R, Thy, M, Rel, L, T1, T2, R1-R7, ZD, CR) is designed so that, when the lamp is switched on, initially a high resistance (R, T1) is provided, which is subsequently reduced.
14. Lamp according to claim 13, in which the inrush current limiting circuit (NTC) has a negative temperature thermistor (NTC).
15. Lamp according to claim 13, in which the inrush current limiting circuit (R, Rel) has a relay (Rel) with a parallel-connected resistor (R).
16. Lamp according to claim 13, in which the inrush current limiting circuit (D1-D4, R, M) has a tine-controlled switching transistor (M) with a parallel-connected resistor (R).
17. Lamp according to claim 13, in which the inrush current limiting circuit (D1-D4, R, Thy) has a time-controlled thyristor (Thy), TRIAC or IGBT with a parallel-connected resistor (R).
18. Lamp according to claim 16 or 17, in which the time control is undertaken via a microcontroller integrated into the electronic ballast (EVG).
19. Lamp according to claim 13, in which the inrush current limiting circuit (L, D5-D9, T1, T2, R1-R7) has a transistor that switches on in a controlled manner (T1).
20. Lamp according to claim 19, in which a circuit (T2, R3-R7, ZD, CR) is connected between a control connection of the transistor and a further connection of the transistor which, in response to the current carried in the transistor (T1), limits the control connection potential.
21. Lamp according to one of claims 11-20, having a thermal cutout (S).
22. Lamp according to one of the preceding claims, in which at least one element of the group consisting of the second capacitor, the third capacitor, the attenuation element (F) and the inrush current limiting circuit (NTC, D1-D4, R, Thy, M, Rel, L, T1, T2, R1-R7, ZD, CR, S) is/are integrated into the lamp connection terminal (AK).

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