Electronic ballast for operating at least a first cascade of LEDs

Abstract

Electronic ballast (10) for operating at least a first cascade of LEDs (D101), comprising: - an input with a first (E1) and a second input terminal (E2) for coupling to an AC supply voltage (V e ); - a rectifier (D002) coupled to the first (E1) and second input terminals (E2), the rectifier (D002) having an output with a first and a second output terminal; - a first unit (EH1) comprising the first cascade of LEDs (D101), the first unit (EH1) being coupled to the first output terminal of the rectifier (D002); - a series circuit comprising a series regulator (Q100) and a shunt resistor (R100), said series circuit being coupled in series between the first unit (EH1) and the second output terminal of the rectifier (D002); - a setpoint value specification device (16) for the series regulator (Q100) with an output which is coupled to the series regulator (Q100), wherein the setpoint value specification device (16) is designed to provide a first partial setpoint value at its output which is correlated with the voltage (V(n003)) between the output terminals of the rectifier (D002); characterized in that the setpoint value specification device (16) is further designed to provide a second partial setpoint value superimposed on the first partial setpoint value to the series regulator (Q100), wherein the second partial setpoint value is inversely correlated with the peak value of a current (I d (Q100)) by the longitudinal regulator (Q100).

Description

Technical FieldThe present invention relates to an electronic ballast for operating at least one first cascade of LEDs, comprising an input having a first and a second input terminal for coupling to an AC supply voltage, a rectifier coupled to the first and the second input terminal, the rectifier having an output having a first and a second output terminal, a first unit comprising the first cascade of LEDs, the first unit being coupled to the first output terminal of the rectifier, a series circuit comprising a series regulator and a shunt resistor, this series circuit being coupled in series between the first unit and the second output terminal of the rectifier, and a setpoint specification device for the series regulator having an output coupled to the series regulator, wherein the set point setter is configured to provide a first partial set point at its output correlated with the voltage between the output terminals of the rectifier. The term "cascade of LEDs" preferably means a plurality of LEDs, but such a "cascade" can also comprise only a single LED.Prior ArtIn LED driver concepts which control the LED current and thus the mains current linearly and in which, on account of their power consumption, it is necessary to ensure a largely sinusoidal current consumption from the mains, a setpoint value for the current regulator has hitherto been derived by means of a resistor divider connected to the rectified alternating supply voltage. Since this input voltage is sinusoidal, the desired value is also sinusoidal and, given a suitable control concept, the actual value of the mains current is also sinusoidal.However, this arrangement gives rise to the problem that fluctuations in the mains voltage result in fluctuations in the current, which on the one hand significantly increases the losses in the linear current regulator in the event of overvoltage and on the other hand leads to an excessively low LED current in the event of undervoltage.Previous solutions intervene in the formation of the setpoint value for the LED current by defining, for example, a maximum value that this setpoint value never exceeds. However, in the event of overvoltage, this leads to the mains current consumption no longer being sinusoidal.WO 2012 / 081878 A2 describes an electronic ballast which ensures constant brightness of an LED cascade connected to the electronic ballast independently of fluctuations in the AC voltage input. This is achieved by using a controller which calculates a sinusoidal target current value based on the alternating voltage and supplies only this target value to the LED cascade, thereby reducing power consumption and extending the life of the LEDs.Another known possibility is to generate a set point value using a multiplier. The multiplier multiplies a sinusoidal voltage obtained by means of the aforementioned voltage divider by a value which is constant at least within a few mains half-cycles and provides at its output a sinusoidal voltage with an amplitude which is variable with respect to the mains voltage. A disadvantage here is the relatively high circuitry complexity for the multiplier.SUMMARY OF THE INVENTIONThe object of the present invention is therefore to further develop an electronic ballast mentioned at the beginning in such a way that, on the one hand, the usual limit values with respect to the mains current harmonics are complied with and, on the other hand, a substantial independence of the power consumption from the effective value of the mains voltage is ensured in the most cost-effective manner possible.This object is achieved by an electronic ballast having the features of patent claim 1.The present invention is based on the idea of providing a second partial setpoint value, superimposed on the first partial setpoint value, to the longitudinal regulator in such a way that the maximum value of the grid current assumes a predefinable value independently of fluctuations in the effective input voltage. For this purpose, it is provided according to the invention that the second partial setpoint value is inversely correlated with the peak value of the current through the series regulator.By suitably setting the ratio of sinusoidal current component-represented by the first partial setpoint value-and direct current which is substantially constant over time within a predeterminable period-represented by the second partial setpoint value-for generating setpoint values, the curve shape of the mains current can be adapted in such a way that, on the one hand, the usual limit values with respect to mains current harmonics are complied with and, on the other hand, a substantial independence of the power consumption from the effective value of the voltage is ensured.The setpoint value specification device preferably comprises a first voltage divider having a first and a second ohmic resistor, which is coupled between the first and the second output terminal of the rectifier, wherein the first partial setpoint value is correlated with the voltage dropping at the second resistor as a result of the current through the first resistor. In this way, with little effort, the first partial setpoint value can be provided in such a way that it is correlated with the voltage between the output terminals of the rectifier.Preferably, a capacitor is connected in parallel with the second ohmic resistor of the first voltage divider, which is coupled between the tap of the first voltage divider and the second output terminal of the rectifier. This serves to intercept high-frequency spikes of the input voltage.According to a preferred embodiment, the setpoint value specification device comprises a partial device for providing the second partial setpoint value, wherein the partial device is coupled on the input side to the shunt resistor and on the output side to the tap of the first voltage divider, wherein the partial device is designed to apply a current inversely correlated with the peak value of the current through the series regulator to the second ohmic resistor of the first voltage divider. Accordingly, a current representing the first partial current value and flowing through the first ohmic resistor of the first voltage divider and the current representing the second partial setpoint value and provided by the partial device are superimposed in the second ohmic resistor of the first voltage divider.The setpoint value presetting device preferably comprises a first operational amplifier, the negative input of which is coupled to the shunt resistor, in particular via an ohmic resistor, and the positive input of which is coupled to the tap of the first voltage divider. In this way, a control signal for the longitudinal controller is provided particularly easily.In this case, the first operational amplifier can be connected in such a way that it acts as a P regulator, as a PI regulator or as an I regulator.It has been found to be advantageous if the dividing device further comprises a second operational amplifier, the positive input of which is coupled to the tap of a second voltage divider coupled to a supply DC voltage, the negative input of which is coupled to the shunt resistor and the output of which is coupled to the tap of the first voltage divider. By means of the second voltage divider, a setpoint value for the peak value of the LED current can be provided. By coupling the output of the second operational amplifier, in particular via an ohmic resistor, to the tap of the first voltage divider, the current generated by the dividing device is superimposed on the second resistor of the first voltage divider-in addition to the current flowing via the first resistor of the first voltage divider.In this context, it is preferred if the sub-device further comprises a diode and a capacitor, wherein the diode is coupled in series between the shunt resistor and the minus input of the second operational amplifier and wherein the capacitor is coupled between the minus input of the second operational amplifier and a reference potential. In this way, the peak value of the LED current in each grid half wave is detected and stored in the capacitor.In this case, the LED current is detected using the shunt resistor which is used in any case for the current regulation and is converted into a voltage. This voltage is then stored in said capacitor. In order that the voltage stored in the capacitor follows the time-varying peak value of the voltage drop at the shunt resistor in an increasing and decreasing manner, it is preferred if an ohmic resistor is connected in parallel with the capacitor.It has proven to be particularly advantageous if the diode is designed as a double diode, wherein the node between the two diodes is coupled to a supply DC voltage. Preferably, a further ohmic resistor is arranged between the junction point of the two diodes and the DC supply voltage. This procedure compensates for the temperature dependence of the diode. Preferably, the resistor arranged between the coupling point of the two diodes and the DC supply voltage is larger than the shunt resistor by several orders of magnitude, so that the current flowing through the further ohmic resistor substantially does not influence the voltage at the shunt resistor and thus the actual value of the current.The averaging time can be adjusted by dimensioning the capacitor and the ohmic resistor connected in parallel with the capacitor, so that fluctuations of the alternating supply voltage over a longer period of time can be taken into account, but short-term fluctuations are masked out.The averaging time is preferably set such that the offset of the current setpoint added as a result of the second partial setpoint value is substantially constant over two to three periods of the alternating supply voltage. For this purpose, the second operational amplifier is preferably connected in such a way that it acts as an I regulator.The second voltage divider preferably comprises a first and a second ohmic resistor, wherein a capacitor is connected in parallel with the second ohmic resistor, which is arranged between the tap of the second voltage divider and a reference potential. This serves to suppress interference voltages. As a result of this circuit arrangement, the I regulator formed by the second operational amplifier can apply a current to the second ohmic resistor of the first voltage divider, which current, in addition to the current through the first ohmic resistor, generates a voltage drop at the second ohmic resistor, which voltage drop is in turn used as a setpoint value for the linear regulator.For a particularly good control characteristic, it is preferred to dimension the second ohmic resistance of the first voltage divider such that without further current injection by the second operational amplifier, an LED current that tends to be too low would flow. The second ohmic resistance of the first voltage divider is preferably tuned in such a way that at rated voltage, approximately a setpoint value which is too low by 15% and provided to the linear regulator would result. This ensures that the second operational amplifier is always in engagement.Without the measures according to the invention, if the linear regulator were regulated only using the first voltage divider known from the prior art, it would convert each overvoltage into thermal energy. At 10% more overvoltage, 10% more current would thus also be generated. Since the power is proportional to the product of voltage and current, this would result in 1.1×1.1=1.21 and thus 21% more power loss in the electronic ballast in the procedure according to the prior art.According to an advantageous development, an auxiliary device is coupled to the second ohmic resistor of the first voltage divider, which auxiliary device is designed to set the edge slope and / or the time of the onset of the voltage dropping across the second ohmic resistor. In this way, the operating behavior can be further improved or the grid current curve shape can be optimized. By means of the auxiliary device, the part of the setpoint value corresponding to the second partial current value can be reduced or set to zero as a function of the voltage provided by the first voltage divider. The second partial current value can add a constant proportion in relation to the period duration of the supply network over a predeterminable period of time, which also results in improved use of the LEDs. However, this substantially constant offset would form a setpoint value even in the time range in which no mains current can flow, which can lead to the current regulator becoming saturated. The auxiliary device can set the slope of the setpoint increase (rising edge of the AC supply voltage) or of the setpoint decrease (falling edge of the AC supply voltage) and the position of the edges with respect to the phase position of the input voltage.The auxiliary device preferably comprises an electronic switch having a control electrode, a working electrode and a reference electrode, wherein the control electrode is coupled to the tap of a third voltage divider having a first and a second ohmic resistor connected in parallel with the first voltage divider. The third voltage divider is dimensioned for this purpose such that the electronic switch of the auxiliary device then reduces the setpoint value to zero if the input voltage is less than the forward voltage of the LEDs of the first cascade and therefore no mains current can flow.In this case, a Zener diode and / or a capacitor can be connected in parallel with the second ohmic resistor of the third voltage divider, which is coupled between the tap of the third voltage divider and a reference potential. By a suitable choice of the capacitance of this capacitor, which is connected in parallel with the second ohmic resistance of the third voltage divider, the edge slope of the voltage over the second ohmic resistance of the first voltage divider, which corresponds to the setpoint value for the current regulator, can be adjusted during the onset of the mains current. The zener diode serves merely to limit the voltage between the control electrode and the reference electrode of the electronic switch of the auxiliary device.The electronic ballast can furthermore comprise at least one second unit, preferably a plurality of second units, having a second cascade of LEDs, which is coupled between the first unit and the series circuit comprising the longitudinal regulator and the shunt resistor, wherein an electronic switch is connected in parallel with the respective second cascade of LEDs. Optionally, an electronic switch can also be connected in parallel with the first cascade of LEDs. In this way, depending on the instantaneous amplitude of the voltage provided at the output of the rectifier, different cascades of LEDs or different combinations of cascades of LEDs may be active in order to make optimum use of the input voltage.Preferably, a buffer capacitor is connected in parallel with the respective cascade of LEDs in order to reduce ripple at twice the frequency of the alternating supply voltage. In other words, the LEDs of the respective cascade can accordingly be supplied from the respective buffer capacitors in the phases in which the input voltage is not sufficient for their operation.In this context, at least one unit, preferably each unit, comprises a diode which is coupled in series to the parallel connection of respective LED cascade and respective buffer capacitor. This prevents the buffer capacitor assigned to a respective LED cascade from being discharged by the electronic switch connected in parallel.Finally, it is preferred if the first and / or the third voltage divider is coupled to the coupling point of the first unit and the second unit on the one hand and to the second output terminal of the rectifier on the other hand. This variant is useful if the first unit does not have a switch, so that it is not designed to be capable of bridging. If the first voltage divider is now connected as mentioned, it is achieved that a setpoint value greater than zero is formed only if the input voltage is greater than the forward voltage of the non-bridged part of the LEDs.Further advantageous embodiments are evident from the dependent claims.Brief Description of the Drawing(s)Exemplary embodiments of the present invention will now be described in more detail below with reference to the appended drawings. The following are shown: FIG. 1 shows a schematic illustration of an exemplary embodiment of an electronic ballast according to the invention; FIGS. 2 to 4 show the time profile of different variables of the electronic ballast shown in FIG. 1 during operation with input voltages which differ in their amplitude.Preferred Embodiment of the InventionFIG. 1 shows a schematic illustration of an exemplary embodiment of an electronic ballast 10 according to the invention. the ballast 10 according to the invention has an input with a first E 1 and a second input terminal E 2, between which an AC supply voltage V e is present, which can be 230 V, 50 Hz, for example. This is applied to a rectifier D 002, which in the present case has four diodes. The voltage provided at the rectifier output is denoted by V(n003). An optional capacitor C001 serves to eliminate high-frequency spikes on the alternating supply voltage V e.A first unit EH 1 comprises a cascade of LEDs, i.e. preferably the series connection of a plurality of LEDs, wherein the "cascade" can also comprise only one LED. In the present case, only the LED with the designation D 101 is shown by way of example. An optional buffer capacitor C101 is connected in parallel with the cascade. A diode D001 is coupled in series between the first output terminal and the parallel circuit comprising buffer capacitor C101 and the first cascade of LEDs, an electronic switch SW1 being connected in parallel with this series circuit in turn.A second unit EH 2 likewise comprises a cascade of LEDs, wherein only the LED D 117 is shown here by way of example. In turn, an optional buffer capacitor C111 is connected in parallel with this cascade. The second unit further comprises a diode D012 coupled between the unit EH1 and the parallel circuit of LED cascade and buffer capacitor C111. A switch SW 2 is coupled in parallel with the series circuit comprising diode D 012 and a parallel circuit comprising LED cascade D 117 and buffer capacitor C 111.The invention described in more detail below can also be realized with only one unit EH1, wherein the switch SW1 can then also be omitted. Capacitor C101 is optional as mentioned. Preferably, however, a plurality of second units EH 2 are arranged in series with the first unit EH 1, wherein, if the respective buffer capacitor C 111 is omitted, the respective diode D 012 can also be omitted. By means of the switches SW 1, SW 2, it is possible to control, depending on the input voltage V e which LED cascade(s) are in operation.Connected in series with the units EH 1, EH 2 is the series circuit of a series regulator Q 100 and a shunt resistor R 100.The current flowing into the longitudinal regulator Q 100 is denoted by I d( Q 100). This current always corresponds to the grid current, i.e. the current which is drawn from the supply grid connected at the input. Without using buffer capacitors, this current corresponds to the LED current. The voltage dropped across the shunt resistor R 100 is denoted by V(n 024). This voltage V(n024) includes the temperature dependence and the dispersion with respect to the forward voltage of the LEDs through which the LED current I d(100) flows in each case.A set point setting device for generating a set point for the longitudinal regulator Q100 is designated 16.In order to generate a first component, which is sinusoidal in e, at a corresponding input voltage V, of a setpoint value applied to the control electrode of the series regulator Q 100, a voltage divider is provided which is coupled between the output terminals of the rectifier D 002 and comprises the ohmic resistors R 011 and R 012. The voltage dropping across ohmic resistor R012 is applied to the positive input of an operational amplifier IC1-B, the negative input of which is coupled to shunt resistor R100 via ohmic resistor R041. The voltage at the output of the operational amplifier IC1-B is denoted by V(n016). The voltage dropping across the ohmic resistor R 012 is denoted by V(n 020). An optional capacitor C 040connected in parallel with the ohmic resistor R 012 is used to intercept high-frequency spikes of the voltage V(n 080) at the tap of the first voltage divider. In the feedback of the operational amplifier IC1-B, the series circuit of an ohmic resistor R043 and a capacitor C041 is coupled to form it as a PI regulator.To generate a second partial setpoint value, a partial device 12 is provided, which provides a voltage V(n009) at its output and applies a second current component through the second ohmic resistor R012 via an ohmic resistor R025. To generate this current portion, the peak value of current I d( Q100) is sensed by the series regulator Q100 by the shunt resistor R100 and stored in the capacitor C020. In the present case, peak value detection is carried out by means of a double diode D 020, wherein the coupling point of the two diodes is coupled to a DC supply voltage via an ohmic resistor R 020. By this arrangement, the temperature dependency of the diode (n) can be compensated for compared with the use of only one diode.The voltage dropping at the coupling point of the two diodes is denoted by V(n017), while the voltage dropping across the capacitor C020 is denoted by V(n012). In order that the voltage stored in the capacitor C020 follows the time-varying peak value of the voltage drop across the shunt resistor R100 in an increasing and decreasing manner, a resistor R021 is connected in parallel with the capacitor C020.The peak value of the LED current I d( Q100) stored in this way is applied via a resistor R022 to the negative input of a further operational amplifier IC1-A, to the positive input of which a setpoint value for the peak value of the LED current I d( Q100) is applied by means of a further voltage divider which comprises the ohmic resistors R023 and R024. For suppressing interference voltages, a capacitor C 021 can be connected in parallel with the resistor R 024.The output of the operational amplifier IC1-A, which forms an I regulator due to the negative feedback capacitor C022, is connected to the resistor R012 via the ohmic resistor R025, as already mentioned. As a result of this interconnection, the I regulator formed by the operational amplifier IC1-A can apply a current to the resistor R012, which current, in addition to the current through the resistor R011, generates a voltage drop across the resistor R012, which voltage drop is in turn used as a setpoint value for the actual linear regulator Q100.For a good control characteristic, R012 is dimensioned such that without further current injection through the operational amplifier IC1-A, an LED current I d( Q100), which tends to be too low, would flow, for example by 10 to 20%, preferably 15%. This ensures that the operational amplifier IC1-A is always engaged.However, since the partial setpoint provided by the operational amplifier IC1-A would form a setpoint even in the time range in which no mains current can flow, because the instantaneous input voltage is smaller than the smallest forward voltage of an LED cascade, this could lead to a saturation state of the linear regulator Q 100. That is, if the mains voltage V e subsequently increases again and in the process increases again above the smallest forward voltage of an LED cascade, the current regulator requires a settling time in which the mains current is greater than the desired value corresponding to the setpoint value. This overshoot of the mains current has a negative effect on the behaviour of the overall arrangement with respect to the mains current harmonics and the radio interference.However, such overshoots of the mains current, i.e. of the current drawn by the mains, can be prevented by an auxiliary device 14, in that the setpoint value dropping across the resistor R 012 can be reduced or set to zero as a function of the voltage provided by a voltage divider. In particular, this allows the slope of the setpoint value increase with a rising edge of the supply voltage V e or of the setpoint value decrease with a falling edge of the supply voltage V e and the position of the edges with respect to the phase position of the input voltage V e to be adjusted.For this purpose, a voltage divider is provided, which comprises the ohmic resistors R 013 and R 014. The tap of this voltage divider is coupled to the control electrode of a transistor Q011. The resistors R013, R014 of this voltage divider are dimensioned such that the transistor Q011 reduces the setpoint value to zero when the input voltage V e is less than the smallest forward voltage of an LED cascade, so that no mains current can flow.By suitably selecting the capacitance of a capacitor C010 connected in parallel with the resistor R014, the slope of the voltage across the resistor R012 corresponding to the set point for the linear regulator Q100 can be adjusted during the onset of line current. A zener diode D010 connected in parallel with the capacitor C010 serves to limit the base-emitter voltage of the switch Q011. The current flowing into the emitter of the transistor Q011 is denoted by I e( Q011).FIGS. 2 to 4 show, for different values of the input voltage V e the time profile of different variables of the electronic ballast schematically illustrated in FIG. 1. Thus, the respective illustration a) shows the time profile of the voltages V(n024), V(n017) and V(n012). The respective representation b) shows the time profile of the voltage V(n003), the respective representation c) the profile of the current I d( Q100), and the respective representation d) the profile of the voltages V(n009), V(n020), V(n016) and of the current I e( Q011).As can be seen from the respective curve profile in the respective illustration b), the peak value of the voltage V(n003) at the rectifier output in the illustration of FIG. 2 is 280 V, in the illustration of FIG. 3 is 320 V and in the illustration of FIG. 4 is 360 V. It can be clearly seen from the respective illustration c) that the current component superimposed as a result of the second partial setpoint value becomes greater the smaller the peak value of the input voltage. Thus, in the present case, it is achieved that, independently of the value of the input voltage V e the peak value of the current I d( Q100) through the series regulator Q100 is always approximately 270 mA. Accordingly, the peak values of the voltages V(n024), V(n017), and V(n012) shown in the respective illustration a) are substantially identical.However, as can be seen from the respective representation d), the smaller the peak values of the input voltage V e the greater the additional partial setpoint value provided by the operational amplifier IC1-A, which can be seen from the curve of the voltage V(n009). V(n020) shows in principle the sum of the two partial setpoint values. However, it must be taken into account that in the phases in which the rectified input voltage V(n003) falls below an amplitude of 90 V (the forward voltage of the first cascade of LEDs was assumed here to be 90 V by way of example), the transistor Q011 is switched to the conductive state by appropriate dimensioning, as can be seen from the corresponding profile of the current I e( Q011). As a result, in the mentioned phases of the voltage V(n003), the voltage V(n020) is short-circuited down to the voltage at the emitter-base junction of the transistor Q011, which is reflected in a corresponding curve of the voltage V(n016) provided at the output of the operational amplifier IC1-B.The peak value of the voltage V(n016) is substantially identical in the different representations of FIGS. 2 to 4.

Claims

Electronic ballast (10) for operating at least a first cascade of LEDs (D101) comprising: - an input having a first (E1) and a second input terminal (E2) for coupling to an AC supply voltage (V e); - a rectifier (D002) coupled to the first (E1) and the second input terminal (E2), the rectifier (D002) having an output having a first and a second output terminal; - a first unit (EH1) comprising the first cascade of LEDs (D101), the first unit (EH1) being coupled to the first output terminal of the rectifier (D002); a series circuit comprising a series regulator (Q100) and a shunt resistor (R100), said series circuit being coupled in series between the first unit (EH1) and the second output terminal of the rectifier (D002); a set point setter (16) for the series regulator (Q100) having an output coupled to the series regulator (Q100), the set point setter (16) being configured to provide a first sub-set point at its output correlated with the voltage (V(n003)) between the output terminals of the rectifier (D002); characterized in that the set point setter (16) is further configured to provide a second sub-set point superimposed on the first sub-set point to the series regulator (Q100), the second sub-set point being inversely correlated with the peak value of a current (I d( Q100)) through the series regulator (Q100).Electronic ballast (10) according to Claim 1, characterized in that the setpoint value specification device (16) comprises a first voltage divider having a first (R011) and a second ohmic resistor (R012) which is coupled between the first and the second output terminal of the rectifier (D002), wherein the first partial setpoint value is correlated with the voltage dropping at the second resistor (R012) as a result of a current through the first resistor (R011).Electronic ballast (10) according to Claim 2, characterized in that a capacitor (C040) is connected in parallel with the second ohmic resistor (R012) of the first voltage divider, which is coupled between the tap of the first voltage divider and the second output terminal of the rectifier (D002).Electronic ballast (10) according to either of the preceding Claims 2 and 3, characterized in that the setpoint value specification device (16) comprises a partial device (12) for providing the second partial setpoint value, wherein the partial device (12) is coupled on the input side to the shunt resistor (R100) and on the output side to the tap of the first voltage divider (R011, R012), wherein the partial device (12) is designed to introduce a current which is inversely correlated with the peak value of the current (I d( Q100)) by the longitudinal regulator (Q100) into the second ohmic resistor (R012) of the first voltage divider (R011, R012).Electronic ballast (10) according to one of the preceding claims 2 to 4, characterized in that the setpoint value specification device (16) comprises a first operational amplifier (IC1-B), the negative input of which is coupled to the shunt resistor (R100), in particular via an ohmic resistor (R041), and the positive input of which is coupled to the tap of the first voltage divider (R011, R012).Electronic ballast (10) according to Claim 5, characterized in that the first operational amplifier (IC1-B) is connected in such a way that it acts as a P regulator, as a PI regulator or as an I regulator.Electronic ballast (10) according to one of the preceding claims 4 to 6, characterized in that the sub-device (12) comprises a second operational amplifier (IC1-A), the positive input of which is coupled to the tap of a second voltage divider (R023, R024) coupled to a supply direct voltage (V CC) the negative input of which is coupled to the shunt resistor (R100) and the output of which is coupled, in particular via an ohmic resistor (R025), to the tap of the first voltage divider (R011, R012).Electronic ballast (10) according to Claim 7, characterized in that the sub-device (12) further comprises a diode (D020) and a capacitor (C020), wherein the diode (D020) is coupled in series between the shunt resistor (R100) and the minus input of the second operational amplifier (IC1-A), and wherein the capacitor (C020) is coupled between the minus input of the second operational amplifier (IC1-A) and a reference potential.Electronic ballast (10) according to Claim 8, characterized in that the diode (D020) is designed as a double diode, the node point between the two diodes being coupled to a supply DC voltage (V CC).Electronic ballast (10) according to either of Claims 8 and 9, characterized in that an ohmic resistor (R021) is connected in parallel with the capacitor (C020).Electronic ballast (10) according to one of Claims 7 to 10, characterized in that the second operational amplifier (EC1-A) is connected in such a way that it acts as an I regulator.Electronic ballast (10) according to one of Claims 7 to 11, characterized in that the second voltage divider comprises a first (R023) and a second ohmic resistor (R024), wherein a capacitor (C021) is connected in parallel with the second ohmic resistor (R024), which is arranged between the tap of the second voltage divider and the reference potential.Electronic ballast (10) according to either of Claims 2 and 3, characterized in that an auxiliary device (14) is coupled to the second ohmic resistor (R012) of the first voltage divider, said auxiliary device being designed to set a slope slope and / or a time of the onset of the voltage dropping across the second ohmic resistor (R012).Electronic ballast (10) according to claim 13, characterised in that the auxiliary device (14) comprises an electronic switch (Q011) having a control electrode, a working electrode and a reference electrode, wherein the control electrode is coupled to the tap of a third voltage divider having a first (R013) and a second ohmic resistor (R014) which is connected in parallel with the first voltage divider (R011, R012).Electronic ballast (10) according to Claim 14, characterized in that a Zener diode (D010) and / or a capacitor (C010) is connected in parallel with the second ohmic resistor (R014) of the third voltage divider (R013, R014), which is coupled between the tap of the third voltage divider and the reference potential.Electronic ballast (10) according to one of the preceding claims, characterized in that the electronic ballast (10) furthermore comprises at least one second unit (EH2), preferably a multiplicity of second units (EH2), having a second cascade of LEDs (D117) which is coupled between the first unit (EH1) and the series circuit comprising the series regulator (Q100) and the shunt resistor (R100), wherein an electronic switch (SW2) is connected in parallel with the respective second cascade of LEDs (D117), wherein in particular an electronic switch (SW1) is also connected in parallel with the first cascade of LEDs (D101).Electronic ballast (10) according to one of the preceding claims, characterized in that a buffer capacitor (C101; C111) is connected in parallel with the respective cascade (D101; D117) of LEDs.Electronic ballast (10) according to claim 17, characterized in that at least one unit (EH1; EH2), preferably each unit, comprises a diode (D001; D012) serially coupled to the parallel connection of respective LED cascade (D101; D117) and respective buffer capacitor (C101; C111).Electronic ballast (10) according to one of Claims 16 to 18, characterized in that the first (R011, R012) and / or the third voltage divider (R013, R014) is coupled on the one hand to the coupling point of the first unit (EH1) and the second unit (EH2) and on the other hand to the second output terminal of the rectifier (D002).

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