DE102019215594A1 - Circuit arrangement and method for controlling semiconductor light sources - Google Patents

Abstract

The invention relates to a circuit arrangement and a method for controlling semiconductor light sources. The circuit arrangement has an energy store, which is charged in series with the semiconductor light sources in one part of the network half-wave and is discharged parallel to the semiconductor light sources in another part of the network half-wave. A switch is used to switch from serial to parallel connection of the energy storage system.

Description

Technical area

The invention concerns circuits for controlling semiconductor light sources by means of an alternating voltage, the alternating voltage being applied directly to the semiconductor light sources without interposing a voltage converter.

background

The invention is based on a circuit arrangement for controlling semiconductor light sources according to the preamble of the main claim. Circuit arrangements are known which can operate a plurality of LEDs connected in series without an energy storage device directly on an AC mains voltage.

1 shows such a circuit arrangement in which an LED cluster of serially connected light-emitting diodes is operated directly on a rectified AC voltage. For this purpose, a current control is connected in series with the LED string. Switches that can short-circuit these sub-strings are arranged parallel to the partial strings. In the example in 1 is the LED string in three strands N1 , N2 and N3 divided. A short-circuit switch, which can short-circuit this sub-line in a controlled manner, is arranged over two of the three sub-strings. As a result, the forward voltage of the LED string can be adapted to the instantaneous voltage of the mains input voltage. This means that, depending on the current mains voltage, a different number of serially connected light-emitting diodes is active and contributes to the generation of light.

2 shows a similar known circuit arrangement with switches arranged overlapping in parallel. With this arrangement, just as many sub-strings can be controlled as with the serial arrangement of short-circuit switches. However, only one of the switches has to be controlled, which can, depending on the circuit topology, bring advantages in the control.

The disadvantage of both variants, however, is a gap in the current through the semiconductor light sources, since when the mains voltage crosses zero, the forward voltage of the smallest sub-string is above the input voltage, and thus no current flows. Another disadvantage is that the total number of series-connected semiconductor light sources must be adapted to the mains input voltage. With a mains input voltage of e.g. 230V, a large number of individual semiconductor light sources are necessary, which is undesirable in many applications today.

task

It is the object of the invention to provide a circuit arrangement for controlling semiconductor light sources which no longer has the aforementioned disadvantages.

Presentation of the invention

The object is achieved according to the invention with a circuit arrangement for controlling semiconductor light sources, having a mains input for inputting a mains voltage, and a rectifier for rectifying the mains voltage and outputting a rectified mains voltage; a semiconductor light source chain, which is a series circuit of at least two LED strings, an energy store, the first connection of which is coupled to a first connection of the semiconductor light source chain via a first decoupling diode, and is coupled to a second connection of the semiconductor light source chain via a second decoupling diode, and the second Port is coupled to the rectifier; a first switch, the first connection of which is coupled to the second connection of the energy store, and the second connection of which is coupled to the connection point between the first decoupling diode and the first connection of the semiconductor light source chain, the circuit arrangement being set up to connect the energy store in series with the first switch open to charge with the first decoupling diode and the semiconductor light source chain and to discharge the energy store with the first switch closed via the second decoupling diode into the semiconductor light source chain. The inventive method of charging the energy storage device in series with the semiconductor light sources and discharging parallel to the semiconductor light sources kills two birds with one stone: On the one hand, the minimum number of semiconductor light sources required can be halved, since half of the mains input voltage in the charging cycle on the Storage capacitor is present and the semiconductor light source chain only needs to be designed for half the mains voltage. On the other hand, the charge on the storage capacitor in discharge the semiconductor light source chain, so that there is a continuous flow of current through the semiconductor light source chain and thus a continuous light output over the entire network half-wave. The high light modulation that is feared in these circuits can be significantly reduced.

In a first embodiment, the first switch is switched as a function of the instantaneous value of the rectified mains voltage. In this way, the current and thus the light modulation of the semiconductor light source chain can advantageously be kept at a low value.

In a further preferred embodiment, the semiconductor light source chain forms at least two segments. With two or more segments, the forward voltage can advantageously be better adapted to the current line voltage.

In a particularly preferred embodiment, part of the rectified mains voltage is applied to the storage capacitor during the charging phase in which the storage capacitor is connected in series with the semiconductor light source chain.

In a further embodiment, a multipole network is coupled to the semiconductor light source chain and to the rectified mains voltage. This multipole network can advantageously take over various functions of the circuit arrangement.

Particularly preferably, the rectified mains voltage is routed via a decoupling diode in at least one segment. The decoupling diode advantageously ensures that the storage capacitor is connected in parallel to the semiconductor light source chain when the switch is closed, and is connected in series with the semiconductor light source chain when the switch is open.

In another embodiment, further switches are provided in the multipole network that apply part of the rectified line voltage corresponding to the instantaneous value of the line voltage to a connection point between two segments or to a connection point of an LED string and a current limiter. The forward voltage of the semiconductor light source chain can thus be adapted to the instantaneous network voltage and the current through the semiconductor light sources can flow very evenly over a network half-wave.

A first connection of the further switches is particularly preferably connected to a connection point between two LED strings or to a connection point of an LED strand and the first decoupling diode, and a second connection of the further switches is connected to a common reference potential. As a result, the control of the switches can advantageously be carried out in a particularly simple manner depending on the current line voltage.

In a preferred embodiment, a further storage capacitor is connected in parallel with at least one segment. This further even out the current flow and thus the light output and advantageously ensures a high quality of light.

The further switches are particularly preferably designed to be current-controlled. This is a particularly simple way of achieving a current flow that is as uniform as possible.

In another preferred embodiment, the first switch is controlled in such a way that it has a current-limiting effect on the current through itself or that a current-limiting device for limiting the current through the first switch is provided in series with the first switch. Overloading of the components and uneven light output due to excessive current modulation can thus advantageously be avoided.

The invention also relates to a method for controlling semiconductor light sources with a circuit arrangement as described above, characterized by the following steps: series connection of the storage capacitor with the LED string by opening the first switch, charging of the storage capacitor by means of the rectified mains voltage input, parallel connection of the storage capacitor with the LED String by closing the first switch, discharging the storage capacitor into the semiconductor light sources. This method ensures good utilization of the storage capacity of the storage capacitor and thus enables a uniform flow of current and thus a uniform emission of light.

Further advantageous developments and refinements of the circuit arrangement according to the invention for controlling semiconductor light sources emerge from further dependent claims and from the following description.

Figure list

• 1 eine bekannte Schaltungsanordnung mit einem LED-Strang von in Serie geschalteten Leuchtdioden, wobei Teilstücke des LED-Stranges von gesteuerten Schaltern überbrückt werden können, und die Schalter seriell angeordnet sind.
• 2 eine bekannte Schaltungsanordnung mit einem LED-Strang von in Serie geschalteten Leuchtdioden, wobei Teilstücke des LED-Stranges von gesteuerten Schaltern überbrückt werden können, und die Schalter parallel angeordnet sind.
• 3a eine erfindungsgemäße Schaltungsanordnung in einer ersten Ausführungsform mit einem LED-Strang von in Serie geschalteten Leuchtdioden, wobei Teilstücke des LED-Stranges über gesteuerte Schalter und über Entkoppelungsdioden mit der gleichgerichteten Netzspannung verbunden werden können, und die Schalter seriell angeordnet sind, und parallel zum LED-Strang ein Speicherkondensator angeordnet ist.
• 3b eine Wahrheitstabelle zur Schaltungsanordnung gemäß der ersten Ausführungsform. (1 =Schalter geschlossen, 0=Schalter offen)
• 3c eine Spannung UG über der Zeit mit den in der Wahrheitstabelle eingetragenen Zeitpunkten t₁..t₆.
• 4a die Schaltungsanordnung in einer zweiten Ausführungsform mit einem LED-Strang von in Serie geschalteten Leuchtdioden, wobei Teilstücke des LED-Stranges über gesteuerte Schalter und über Entkoppelungsdioden mit der gleichgerichteten Netzspannung verbunden werden können, und die Schalter auf ein gemeinsames Potential bezogen sind, und parallel zum LED-Strang ein Speicherkondensator angeordnet ist.
• 4b eine Wahrheitstabelle zur Schaltungsanordnung gemäß der zweiten Ausführungsform.
• 5a die Schaltungsanordnung in einer dritten Ausführungsform mit einem LED-Strang von in Serie geschalteten Leuchtdioden, wobei Teilstücke des LED-Stranges über gesteuerte Schalter und über Entkoppelungsdioden mit der gleichgerichteten Netzspannung verbunden werden können, und die Schalter seriell angeordnet sind, und parallel zum LED-Strang ein Speicherkondensator angeordnet ist.
• 5b eine Wahrheitstabelle zur Schaltungsanordnung gemäß der dritten Ausführungsform.
• 6a eine die erfindungsgemäße Schaltungsanordnung in einer vierten Ausführungsform mit einem LED-Strang von in Serie geschalteten Leuchtdioden, wobei Teilstücke des LED-Stranges über gesteuerte Schalter und über Entkoppelungs-dioden mit der gleichgerichteten Netzspannung verbunden werden können, und die Schalter auf ein gemeinsames Potential bezogen sind, und parallel zum LED-Strang ein Speicherkondensator angeordnet ist.
• 6b eine Wahrheitstabelle zur Schaltungsanordnung gemäß der vierten Ausführungsform.
• 7a eine die erfindungsgemäße Schaltungsanordnung in einer fünften Ausführungsform mit einem LED-Strang von in Serie geschalteten Leuchtdioden, wobei Teilstücke des LED-Stranges über gesteuerte Schalter und über Entkoppelungsdioden mit der gleichgerichteten Netzspannung verbunden werden können, und die Schalter seriell angeordnet sind, und parallel zum LED-Strang ein Speicherkondensator angeordnet ist, und parallel zu einem Teil der in Serie geschalteten Leuchtdioden eine gesteuerte Stromquelle angeordnet ist.
• 7b eine Wahrheitstabelle zur Schaltungsanordnung gemäß der fünften Ausführungsform.
• 8 die Schaltungsanordnung der zweiten Ausführungsform, wobei die gesteuerten Schalter durch eine reale Anordnung aus Bipolartransistoren ersetzt sind,
• 9 die Schaltungsanordnung in einer sechsten Ausführungsform, die ähnlich der dritten Ausführungsform ist, wobei der Speicherkondensator jedoch nicht fest parallel zum LED-Strang geschaltet ist, sondern in Serie zum LED-Strang geladen wird und parallel zum LED-Strang entladen wird
• 10 die Schaltungsanordnung in einer siebten Ausführungsform, die ähnlich der sechsten Ausführungsform ist, wobei die optionalen Entkoppeldioden weggelassen wurden,
• 11 die Schaltungsanordnung in einer achten Ausführungsform, die ähnlich der sechsten Ausführungsform ist, wobei die Entkoppeldioden in Serie zum LED-Strang geschaltet sind,
• 12 die Ausgestaltung der Schaltungsanordnung in einer achten Ausführungsform als analoge Schaltung mit einem LED-Strang von in Serie geschalteten Leuchtdioden und einem Speicherkondensator, bei der der Speicherkondensator in Serie zum LED-Strang geladen wird und parallel zum LED-Strang entladen wird, wobei die gesteuerten Schalter durch eine reale Anordnung aus Bipolartransistoren ersetzt sind.

Further advantages, features and details of the invention emerge from the following description of exemplary embodiments and from the drawings, in which identical or functionally identical elements are provided with identical reference symbols. Show:

• 1 a known circuit arrangement with an LED string of light-emitting diodes connected in series, parts of the LED string being able to be bridged by controlled switches, and the switches being arranged in series.
• 2 a known circuit arrangement with an LED string of light-emitting diodes connected in series, parts of the LED string being able to be bridged by controlled switches, and the switches being arranged in parallel.
• 3a a circuit arrangement according to the invention in a first embodiment with an LED string of light-emitting diodes connected in series, with sections of the LED string being able to be connected to the rectified mains voltage via controlled switches and decoupling diodes, and the switches are arranged in series, and parallel to the LED Strand a storage capacitor is arranged.
• 3b a truth table for the circuit arrangement according to the first embodiment. (1 = switch closed, 0 = switch open)
• 3c a voltage UG over time with the times t ₁ ... _{t 6} entered in the truth table.
• 4a the circuit arrangement in a second embodiment with an LED string of light-emitting diodes connected in series, parts of the LED string can be connected to the rectified mains voltage via controlled switches and decoupling diodes, and the switches are related to a common potential, and parallel to the LED string a storage capacitor is arranged.
• 4b a truth table for the circuit arrangement according to the second embodiment.
• 5a the circuit arrangement in a third embodiment with an LED string of light-emitting diodes connected in series, parts of the LED string being able to be connected to the rectified mains voltage via controlled switches and decoupling diodes, and the switches are arranged in series and parallel to the LED string a storage capacitor is arranged.
• 5b a truth table for the circuit arrangement according to the third embodiment.
• 6a a circuit arrangement according to the invention in a fourth embodiment with an LED string of light-emitting diodes connected in series, parts of the LED string being able to be connected to the rectified mains voltage via controlled switches and decoupling diodes, and the switches are related to a common potential , and a storage capacitor is arranged parallel to the LED string.
• 6b a truth table for the circuit arrangement according to the fourth embodiment.
• 7a a circuit arrangement according to the invention in a fifth embodiment with an LED string of series-connected light-emitting diodes, parts of the LED string can be connected to the rectified mains voltage via controlled switches and decoupling diodes, and the switches are arranged in series and parallel to the LED -Strang a storage capacitor is arranged, and a controlled current source is arranged parallel to part of the series-connected light-emitting diodes.
• 7b a truth table for the circuit arrangement according to the fifth embodiment.
• 8th the circuit arrangement of the second embodiment, the controlled switches being replaced by a real arrangement of bipolar transistors,
• 9 the circuit arrangement in a sixth embodiment, which is similar to the third embodiment, but the storage capacitor is not permanently connected in parallel to the LED string, but is charged in series with the LED string and is discharged parallel to the LED string
• 10 the circuit arrangement in a seventh embodiment, which is similar to the sixth embodiment, wherein the optional decoupling diodes have been omitted,
• 11 the circuit arrangement in an eighth embodiment, which is similar to the sixth embodiment, wherein the decoupling diodes are connected in series with the LED cluster,
• 12th the configuration of the circuit arrangement in an eighth embodiment as an analog circuit with an LED string of light-emitting diodes connected in series and a storage capacitor, in which the storage capacitor is charged in series with the LED string and is discharged parallel to the LED string, with the controlled switch are replaced by a real arrangement of bipolar transistors.

Preferred embodiment of the invention

An LED string comprises several segments N ₁ , N ₂ , N ₃ connected in series with each other. If necessary, further components can be arranged between the LED segments. Every LED segment N ₁ to N ₃ may have a plurality of LEDs connected in series with one another. The LED segments N ₁ , N ₂ , N ₃ are also referred to below as segments N ₁ , N ₂ , N ₃ designated.

A line voltage Uin refers to an alternating voltage such as that provided by an electrical supply network. The mains voltage can be converted into rectified mains voltage half-waves via a rectifier U _G (also referred to as “half-waves” or “rectified mains voltage”). The rectifier 10 can be designed as a one-way or a two-way rectifier.

Combinational possibilities of the forward voltages corresponding to the LED segments are used to control the series-connected LED segments. According to the number of LEDs connected in series in a segment, a forward voltage results as the sum of the forward voltages of all LEDs. Different numbers of LEDs connected in series can result in different forward voltages for different LED segments.

It should be noted here that different LEDs of the same or different types (e.g. different LED modules and / or LEDs with different colors) can be connected in series. It is also possible for individual LEDs to include a parallel connection of at least one semiconductor luminous element.

wobei Ui(l) eine Gesamtspannung der nicht überbrückten LEDs für den Schaltzustand t_i bei einem Strom I ist.In parallel to at least one LED segment N ₁ ..N _n , in particular parallel to several LED segments, electronic switches can be provided which short-circuit the supply path from the rectifier via individual or several LED segments, but the current path for the decoupling diodes Do not change the storage capacitor. By activating the electronic switches, it can be achieved that the voltage of the LED segments U _LED (t) effective for the supply path from the mains rectifier follows (or is tracked) the rectified mains voltage U _G (t) (i.e. the half-waves mentioned above) ): $${\text{U}}_{\text{LED}}\left(\text{t}\right)={\text{U}}_{\text{LED}}\left({\text{t}}_{\text{I.}},\text{I.}\right)-{\text{U}}_{\text{i}}\left(\text{l}\right),$$

where Ui (l) is a total voltage of the non-bridged LEDs for the switching state t _i at a current I.

Here, the LED segments can be designed differently, ie they can have forward voltages that are at least partially different from one another. In particular, at least two of the LED segments can have different numbers and / or types of LEDs. In other words, not all LED segments have to be equipped with the same number of LEDs of the same type with the same interconnection. 3a shows a circuit arrangement according to the invention in a first embodiment with an LED cluster of light-emitting diodes connected in series. The LED strand is in segments N ₁ , N ₂ and N ₃ split, with segments N ₁ , N ₂ , N ₃ of the LED string of controlled switches via decoupling diodes D ₁ and D ₂ can be supplied. The LED string is over the first decoupling diode D ₁ and through a current control circuit 3 to the rectified mains voltage U _G connected. The rectified line voltage U _G is connected to the anode of the decoupling diode D1 and to the connection of the current control circuit which is not connected to the LED cluster. The cathode of the last LED in the segment N ₃ is with the current control circuit 3 connected, while the anode of the first light-emitting diode of the segment N ₁ with the cathode of the decoupling diode D ₁ connected is. The decoupling diode D ₁ is therefore arranged lying on top. A first switch S ₁ has its first connection to the anode of the decoupling diode D ₁ connected, its second terminal is connected to the anode of the second decoupling diode D ₂ . The cathode of the decoupling diode D ₂ is at the connection point between the segment N ₁ and segment N ₂ connected.

A second switch S ₂ is between the anode of the decoupling diode D ₂ and the connection point between the segment N ₂ and segment N ₃ switched. Between the second switch S ₂ and the connection point between the segment N ₂ and segment N ₃ a third decoupling diode D ₃ can also be inserted. A third switch S ₃ has one connection connected to the second switch S ₂ , while the other connection is connected to the connection point between the third segment N ₃ and the current regulating circuit 3 connected is.

A storage capacitor C ₁ is connected to both ends of the LED string.

The following table shows examples of possible combinations with an arrangement with three LED segments N ₁ , N ₂ , N ₃ , in which
t _i the switching state,
S _m with m = 1 to 3 the switch,
0 an open switch,
1 a closed switch,
U _N1 (l) to U _N3 (l) denote a forward voltage of the LEDs not bridged on the mains side at the current I for the LED segment 1 to 3. I. S ₁ S ₂ S ₃ U _i (l) t ₁ 1 1 1 t ₂ 1 1 0 U _N3 (l) t ₃ 1 0 0 U _N2 (l) + U _N3 (l) t ₄ 0 0 0 U _N1 (l) + U _N2 (l) + U _N3 (l) t ₅ 1 0 0 U _N2 (l) + U _N3 (l) t ₆ 1 1 0 U _N3 (l) t ₁ 1 1 1

The residual tension
UG (t) - ULED (t)
falls on the current regulator 3 from. With a plurality of LED segments with different (many) LEDs connected in series, a plurality of different total forward voltages can be implemented for the partial LED strings connected to the network, so that this total voltage comes very close to the current network voltage. The residual voltage U _G (t) _{-U LED} (t) is therefore small compared to the rectified mains voltage U _G (t).

Because of this low residual voltage, the current regulator can be designed, for example, as a linear regulator that is simple and inexpensive to implement. The current regulator can also be designed so that the current (almost) ideally follows the mains voltage, so that a power factor (mains power factor) of the circuit is close to 1.0 and no (noteworthy) harmonics occur.

In extreme cases, the current regulator can even be omitted, e.g. if the dynamics of the LED characteristic curve with a limited current modulation is sufficient to fill the gaps between the switching stages.

In the following, the function of the circuit arrangement is based on 3a to 3c explained. 3b shows a switching table analogous to the table above for the three switches S ₁ , S ₂ and S ₃ at different times of the half-wave of the rectified mains voltage U _G . The 3c shows the rectified line voltage U _G over time. The times t ₁ to t _{6 of} the switching table are in the 3c registered.

At time t ₁ , the line voltage is in the zero crossing and the rectified line voltage is accordingly zero. It is assumed below that the storage capacitor C ₁ is empty. All three switches S ₁ to S ₃ are closed and no current flows from the rectifier. A current then begins from the rectifier via switches S ₁ to S ₃ and the current control circuit 3 to flow.

At time t ₂ , switches S ₁ and S _{2 are} closed while switch S _{3 is} open. As a result, the current driven by the rectified instantaneous mains voltage flows through the segment _{via the closed switches S 1} and S ₂ and the decoupling diode D ₃ N ₃ . The current control circuit 3 regulates this current to a value that is optimal _{for operation at time t 2.} This current can, for example, be proportional to the current mains voltage in order to achieve a power factor close to 1.0. A charging current can be passed through the storage capacitor via the decoupling diode D1 C ₁ to the current control circuit 3 flow and the storage capacitor C ₁ charge. At time t ₃ , switch S _{1 is} closed and switches S ₂ and S _{3 are} open. The current from the rectifier now flows through the switch S ₁ , the decoupling _{diode D 2} and the two segments N ₂ and N ₃ to the current control circuit 3 which in turn regulates to an optimal current strength. A charging current can be applied via the decoupling diode D ₁ through the storage capacitor C ₁ to the current control circuit 3 flow and the storage capacitor C ₁ charge.

At time t ₄ , the mains voltage has reached its peak value and all switches S ₁ to S ₃ are open. The current from the rectifier flows through the decoupling diode D ₁ through all segments N ₁ to N ₃ and through the storage capacitor connected in parallel C ₁ which is charged by it. At time t ₅ , the line voltage has dropped again and switch S ₁ is closed again. The mains current flows from the rectifier 10 via the switch S ₁ through the decoupling diode D ₂ and through the segments N ₂ and N ₃ to the current control circuit 3 . Another partial current flows from the charged storage capacitor C ₁ through the segments N ₁ to N ₃ . This partial current does not flow via the current regulating circuit, so that the current is solely via the voltage on the storage capacitor C ₁ and results in the forward voltage of all serially connected LEDs of the LED string.

At time t ₆ , the line voltage has dropped further and switches S ₁ and S ₂ are closed. The switch S ₃ is still open. The mains current flows from the rectifier 10 via the switches S ₁ and S ₂ through the decoupling diode D ₃ and through the segment N ₃ to the current control circuit 3 . Another partial current flows from the charged storage capacitor C ₁ through the segments N ₁ to N ₃ . This partial current does not flow via the current regulating circuit, so that the current is solely via the voltage on the storage capacitor C ₁ and results in the forward voltage of all serially connected LEDs of the LED string.

At the next point in time t ₁ , the mains voltage is again in the next zero crossing, and no current flows into the segments from the rectifier N ₁ , N ₂ or N ₃ . However, a current can still flow from the storage capacitor C ₁ into the segments N ₁ , N ₂ or N ₃ flow, provided that the forward voltage of the segments is even lower than the voltage on the storage capacitor. Because the forward voltage drops as the current through the LEDs decreases, a current through the LEDs and thus a light output of the LED chain can be maintained for a long time when the mains voltage crosses zero. This is also aided by the fact that the forward voltage of the LEDs is caused by the total current of the mains current and the discharge current through the capacitor C ₁ is determined and therefore the discharge current through the capacitor near the mains zero crossing C ₁ can increase again, as the forward voltage of the LEDs also decreases due to the falling mains current.

At the following times t ₂ and t ₃ , in addition to the above-described current from the rectifier, a current from the storage capacitor can continue C ₁ flow into the segments. Due to the topology, the current from the storage capacitor always flows through all segments N ₁ , N ₂ and N ₃ .

The decoupling diodes D ₁ , D ₂ and D ₃ prevent the current from flowing out of the storage capacitor C ₁ through the switch S ₁ , S ₂ or S _{3 can} flow, and the switches the storage capacitor C ₁ can partially or fully short-circuit. The decoupling diode D ₁ is absolutely necessary, the decoupling diodes D ₂ and D ₃ are optional.

The 4a and b show a second embodiment of the circuit arrangement. The second embodiment is similar to the first embodiment. Therefore, only the differences from the first embodiment will be explained.

In the second embodiment, the switches S ₁ to S _{3 are} all related to a common potential. The second connections of each switch are to the connection point between the cathode of the decoupling diode D ₁ and the current regulating circuit 3 connected. The first connections of each switch are in each case via the decoupling diodes D ₂ and D ₃ with a connection point between the segments N ₁ , N ₂ and N ₃ or between the connection point of the segment N ₃ and coupled to the rectifier. The first connection of the switch S1 is to the anode of the first LED of the segment N ₃ connected. The first connection of the switch S ₂ is connected to the cathode of the decoupling diode D ₃ , its anode again with the connection point between segment N ₂ and N ₃ connected is. The first connection of the switch S ₃ is connected to the cathode of the decoupling diode D ₂ , the anode of which in turn is connected to the connection point between the segment N ₁ and N ₂ connected is. The cathode of the decoupling diode D1 is with the second connections of the switch S1 to S3 connected, the anode of the decoupling diode D1 is connected to the cathode of the last LED in the LED segment N1 connected. The current control circuit 3 is connected to the cathode of the decoupling diode D1. The diodes D1 to D3 and the switches S1 to S3 are to the network V _N1 summarized.

4b FIG. 13 shows the shift table of the second embodiment in FIG 4a . The times t ₁ to t ₆ as a function of the instantaneous voltage UG (t) correspond to those of 3c .

At time t ₁ , all switches S ₁ to S _{3 are} closed. The switch S ₁ short-circuits the entire LED string, the switches S ₂ and S ₃ are actually not necessary at this point in time and could also be open.

At time t ₂ , switches S ₂ and S _{3 are} closed and switch S _{1 is} open. A current flows from the rectifier 10 through the LED segment N ₃ via the switch S ₂ to the current control circuit 3 . Part of the current flows through the storage capacitor C ₁ and the decoupling diode D ₁ to the current control circuit 3 and charges the storage capacitor C ₁ on. The switch S ₃ has no effect at this point in time and could also be open.

At time t ₃ , the two switches S ₁ and S _{2 are} open, switch S ₃ is closed. The current flows from the rectifier 10 via the LED segments N ₃ and N ₂ , the decoupling _{diode D 2} and the switch S ₃ for the current control circuit 3 . Part of the current flows through the storage capacitor C ₁ and the decoupling diode D ₁ to the current control circuit 3 and charges the storage capacitor C ₁ further on.

At time t ₄ , the sinusoidal half-wave of the mains voltage is at its apex, and all switches S ₁ to S _{3 are} open. The current flows from the rectifier 10 via the LED string from the LED segments N ₃ to N ₁ to the current control circuit 3 . Part of the current flows through the storage capacitor C ₁ and the decoupling diode D ₁ to the current control circuit 3 and charges the storage capacitor C ₁ to the peak tension of U _G on.

At time t ₅ , switch S ₃ is closed again, and a current flows from the rectifier 10 via the LED segments N ₃ and N ₂ , the decoupling _{diode D 2} and the switch S ₃ for the current control circuit 3 . A partial current flows from the charged storage capacitor C ₁ through the LED segments N ₃ to N ₁ back to the condenser.

At time t ₆ , switches S ₂ and S _{3 are} closed, switch S ₁ is open. The switch S ₃ is ineffective and could also be open. A current flows from the rectifier 10 via the LED string N ₃ , the decoupling _{diode D 3} and the switch S ₂ for the current control circuit 3 . A partial current flows from the charged storage capacitor C ₁ through the LED segments N ₃ to N ₁ back to the condenser.

At the next point in time t ₁ , all switches are closed. Since the switch S ₁ bridges the two switches S ₂ and S ₃ , their state is irrelevant. They could also be open. At time t ₁ , the mains voltage is in its zero crossing, the voltage U _G is therefore also 0V. Therefore no current can come from the rectifier 10 flow. However, a current flows from the storage capacitor that is still charged C ₁ through the LED string, i.e. the segments N ₃ to N ₁ . The storage capacitor thus maintains a current through the LEDs even when the mains voltage crosses zero. This means that the modulation that is otherwise always present is significantly weakened due to the frequency of the mains voltage.

The circuit arrangement of the 5a does not differ significantly from the circuit arrangement of the 3a . It is therefore only on the differences to the circuit arrangement of the 3a received.

In the circuit arrangement of the 5a are the anodes of the decoupling diodes D ₁ to D _{3 are} connected to the corresponding connection points between the LED segments, and the cathodes of the decoupling diodes D ₁ to D ₃ are connected to the connection points between the switches connected in series. This will provide the supply for the LED segment N ₃ now short-circuited by switch S ₁ , the supply for the segment N ₂ shorted by switch S ₂ , and the supply for the LED segment N ₁ short-circuited by switch S _3. The decoupling diode D ₁ is absolutely necessary so that the LED String storage capacitor connected in parallel C ₁ cannot be short-circuited _{by switches S 1} to S _3. The mains current through the LED string always flows through the decoupling diode D ₁ .

5b FIG. 13 shows the switching table of the third embodiment of the circuit arrangement according to FIG 5a . The times t ₁ to t ₆ as a function of the instantaneous voltage U _G (t) correspond to those of 3c .

Here, too, the mains input voltage _{is at time t 1 of the zero crossing} Uin , in which also the rectified mains voltage U _G equals zero, all switches are closed.

At time t ₄ , at which the peak value of the mains input voltage Uin or the rectified mains voltage U _G occurs, all switches are open. The mode of operation otherwise corresponds to the function of the circuit arrangement according to FIG 3a .

The circuit arrangement of the 6a does not differ significantly from the circuit arrangement of the 4a . It is therefore only on the differences to the circuit arrangement of the 4a received.

In the circuit arrangement of the 6a are the switches S ₁ to S ₃ as in the circuit arrangement of the 4a all related to a common potential. The second connections of each switch are to the connection point between the anode of the decoupling diode D ₁ and the rectifier 10 connected. The first connections of each switch are in each case via the decoupling diodes D ₂ and D ₃ with a connection point between the segments N ₁ , N ₂ and N ₃ or between the connection point of the segment N ₃ and the current regulating circuit 3 coupled. The first connection of switch S ₁ is to the cathode of the last LED of the segment N ₃ connected. The first connection of the switch S ₂ is connected to the anode of the decoupling diode D ₃ , the cathode of which in turn is connected to the connection point between the segment N ₂ and N ₃ connected is. The first connection of the switch S ₃ is connected to the anode of the decoupling diode D ₂ , the cathode of which in turn is connected to the connection point between the segment N ₁ and N ₂ connected is. The cathode of the decoupling diode D ₁ is with the connection point between the anode of the first diode of the LED segment N ₁ and the storage capacitor C ₁ connected. The anode of the decoupling diode D ₁ is with the rectifier 10 connected. The decoupling diode D ₁ is absolutely necessary so that the storage capacitor connected in parallel to the LED string C ₁ cannot be short-circuited _{by switches S 1} to S _3.

6b FIG. 13 shows the switching table of the fourth embodiment of the circuit arrangement according to FIG 6a . The times t ₁ to t ₆ as a function of the instantaneous voltage U _G (t) correspond to those of 3c .

Here, too, the mains input voltage _{is at time t 1 of the zero crossing} Uin , in which also the rectified mains voltage U _G equals zero, all switches are closed.

At time t ₄ , at which the peak value of the mains input voltage Uin or the rectified mains voltage U _G occurs, all switches are open. The mode of operation otherwise corresponds to the function of the circuit arrangement according to FIG 3a .

The 7a and b show a fifth embodiment of the circuit arrangement according to the invention. The fifth embodiment is similar to the first embodiment. Therefore, only the differences from the first embodiment will be explained.

The fifth embodiment corresponds to the first embodiment, with only two switches S1 and S2 . That means that in the zero crossing the LED segment N3 is always active and is not short-circuited.

The fifth embodiment differs from the first embodiment in that some of the LEDs of the LED segment N1 can be partially short-circuited. The short circuit is not necessarily to be viewed as a low-resistance shunt, but can also only carry part of the current through the LED string. The shunt is made in the fifth embodiment by an arrangement Z realized with a transistor. The collector of a bipolar transistor T1 is connected to the connection point between the cathode of the decoupling diode D1 and the anode of the top diode of the LED segment N1 connected. The emitter of the bipolar transistor T1 is via an emitter resistor R3 with a connection point of two LEDs of the LED segment N1 connected. The LEDs between the collector of T1 and the emitter resistor R3 can therefore be partially bridged. A voltage divider consisting of the Resistors R1 and R2 is between the collector of the bipolar transistor T1 and the connection point between the current regulating circuit 3 and the rectifier 10 switched. The base of the bipolar transistor T1 is connected to this voltage divider.

The circuit can now be dimensioned so that a current flows through the LED string for a very long time, even if the voltage of the storage capacitor C1 is discharged lower than the actual forward voltage of the LED string. If this occurs, the transistor T1 has a lower resistance and the voltage U _CE across the transistor drops. As a result, the forward voltage of the entire LED string also drops, and the LED string can continue to be operated.

7b FIG. 11 shows the switching table of the circuit arrangement according to FIG 7a . The times t ₁ to t ₆ as a function of the instantaneous voltage U _G (t) correspond to those of 3c .

8th shows a possible simple analog implementation of the switches including the control. The circuit arrangement itself corresponds to the circuit arrangement of the second embodiment of FIG 4a . The switches S ₁ to S ₃ correspond to the transistors T ₁ to T ₃ . The resistors R ₁ to R ₃ are shunt resistors which are connected as emitter resistors and which _{switch on the transistors T 1} to T ₃ one after the other due to the current flow through the LED cluster. The following condition is essential for the circuit to work:
R ₃ <R ₂ <R ₁ ;

The shunts R ₁ , R ₂ , R ₃ are thus chosen such that the transistors T ₁ , T ₂ , T ₃ each switch on and off at a specific current through the LED string. The transistors are thus arranged as current-controlled switches. The circuit is arranged in such a way that the transistors are switched on at low currents and switch off when a certain current threshold is reached. Due to the small resistance of the shunt R ₃ , the transistor T _{3 is} only switched off at relatively high currents. If the voltage drops after it has passed its peak value, transistor T _{3 is} thus the first to be switched on again at time t _5. The circuit is based on the knowledge that with a high driving voltage UG, the resulting current through the LED cluster is also higher. By switching on the transistor T ₃ , the LED string is shortened, and the forward voltage of the still active LED string drops as a result. If the input voltage continues to fall U _G the switching threshold of transistor T _{2 is} reached at time t ₆ , and this switches on. As a result, the forward voltage of the LED string continues to decrease, and the current through the remaining active LED string increases again for a short time. With decreasing voltage UG, but this also decreases again and falls at time t _1, the switching threshold for the transistor T. ₁ The driving voltage for the LED string is then so low that it can no longer drive any current through the chain. In reverse order, the transistors are switched off again, therefore, at the time t ₂ of the transistor T _1, the time t ₃ of the transistor T ₂ and the time t _4, the transistor _T3.

The current-regulated switches S11 to S13 can be supplied by a tap in the bottom LED cluster. 8th is to be understood here only as a principle circuit diagram. As soon as the transistor T3 is switched on, the supply must be maintained, for example by means of a buffer capacitor.

9 shows the circuit arrangement in a sixth embodiment, which is similar to the third embodiment, but the storage capacitor is not permanently connected in parallel to the LED string, but is charged in series with the LED string and is discharged parallel to the LED string. In principle, this procedure has the advantage that the circuit arrangement manages with fewer LEDs connected in series, because the capacitor is arranged in the charging path and can be charged to half the network voltage in the course of a network half-cycle. This advantage should not be underestimated, as LED technology has made such progress that many LEDs are no longer required in modern light sources, as a single LED now has a significantly higher light output than it did a few years ago. This embodiment is therefore particularly suitable especially for lamps and LED modules with smaller light packages. The circuit that switches the storage capacitor from parallel operation to serial operation consists of a diode D8, a diode D9 and a switch S1A. In serial operation, switch S1A is switched off and storage capacitor C1 is connected in series with the LED cluster. As the network half-cycle increases, the storage capacitor C1 charges up increasingly in accordance with the current in the LED cluster. As the network half-wave falls, the point in time at which the voltage from the network is no longer sufficient and is lower than the forward voltage of the LED string, so that a current could no longer be maintained through it. Before this point in time, the switch S1A is switched on. This results in a current path from the connection of the storage capacitor C1, which is connected to the switch S1A, via the switch S1A to the cathode of the diode D9 through the LED cluster via the diode D8 to the connection of the storage capacitor C1, the connected to the anode of diode D9. The diode D9 is used for decoupling so that the switch S1A can no longer short-circuit the storage capacitor C1. With this measure, a current can be maintained through the LED string during the voltage zero crossing of the mains voltage, and thus a low light modulation over the mains half-wave can be achieved. Furthermore, the switches S2 and S3 as already described, follow the voltage on the storage capacitor C1 and one of the segments N1 or N2 be bridged in order to still be able to use smaller voltages with a more heavily discharged capacitor.

10 shows the circuit arrangement in a seventh embodiment, which is similar to the sixth embodiment, wherein the optional decoupling diodes D1, D2, D3 have been omitted. This represents a simplified embodiment which has the disadvantage that the storage capacitor C1 would now be completely discharged if all switches are switched on at the same time, since the storage capacitor is then short-circuited. However, this is not the case with simpler variants if only certain combinations of the switches are switched on at the same time.

11 shows the circuit arrangement in an eighth embodiment, which is similar to the sixth embodiment, wherein the decoupling diodes are connected in series with the LED cluster. Due to the serial connection to form the LED string, additional storage capacitors C _N1 and C _N2 can be used, which can further improve the light modulation over the network half-wave. The storage capacitors C _N1 and C _N2 are parallel to the respective segment N1 respectively N2 switched. The associated switches S2 for the segment N2 and S3 for the segment N1 are parallel to the series connection of the LED string N2 and the decoupling diode D2 or the LED string N1 and the decoupling diode D1 switched. With these measures, the switches S2 and S3 the storage capacitors C _N1 and C _N2 do not discharge. The control of the circuit via a half-wave of the mains input voltage Uin is as described above for the sixth embodiment. When the mains voltage is sufficient, switch S1A is open and storage capacitor C1 is therefore in series with the segments N1 and N2 switched. If the mains voltage is lower than the forward voltage of the switched-on LED string N1 or N2 , then switch S1A is closed and storage capacitor C1 is parallel to the segments N1 and N2 switched. The current flows from the storage capacitor C1 via the switch S1A to the cathode of the decoupling diode D9, then through the LED strings N1 and N2 (or the switches S2 , S3 if switched on) through the decoupling diode D1 and the decoupling diode D8 back to the storage capacitor C1. An alternative embodiment can provide that the current path from the LED string N1 flows directly to the decoupling diode D8 (dashed line), since the decoupling diode D1 is not required for this.

12th shows the circuit arrangement in a ninth embodiment with an LED cluster N ₁ + N ₂ of light-emitting diodes connected in series and a storage capacitor C ₁ , in which the storage capacitor is charged in series with the LED string and discharged in parallel with the LED string. The charging current path in the ninth embodiment goes from the rectifier 10 away via the storage capacitor C1 and the LED strings N2 and N1 to the current control circuit 3 and back to the rectifier 10 . As soon as the instantaneous value of the mains voltage falls below a certain value, the transistor T1 becomes conductive. This opens up a discharge current path from the storage capacitor C1 via the transistor T1 to the LED strings N2 and N1 and from there via the resistor R12 and the decoupling diode D8 back to the storage capacitor C ₁ . The transistors T6 and T8 become dependent on the voltage applied to the LED strings, similar to that in FIG 3a controlled as described. The switches close depending on the total voltage across the LED strings N1 and N2 and ensure the most continuous flow of electricity possible. The excess voltage drops on the linear regulator 3 which keeps the current in a favorable range.

List of reference symbols

1

Circuit arrangement

3

Current control circuit, current control circuit

5

Light emitting diodes

10

Rectifier

11, 12

Power input

13th

positive rectifier output

14th

negative rectifier output

N1..N3

LED strands

Uin

Mains voltage

Basement

rectified mains voltage

C1

Storage capacitor

D1

Decoupling diode

D8

Decoupling diode

VN1

Multipole network

S1, S2, S3

counter

Z

arrangement

Uin

Mains voltage

Basement

rectified mains voltage

P12, P23

Nodes

Claims (11)

Circuit arrangement for controlling semiconductor light sources (5), comprising: - a mains input (11, 12) for inputting a mains voltage (U _in ), and - a rectifier (10) for rectifying the mains voltage (Uin) and outputting a rectified mains voltage (U _G ); - a semiconductor light source chain, which is a series connection of at least two LED strings (N ₁ , N ₂ ), - an energy store (C ₁ ), the first connection of which is coupled to a first connection of the semiconductor light source chain via a first decoupling _{diode (D 9),} and is coupled to a second connection of the semiconductor light source chain via a second decoupling _{diode (D 8} ), and the second connection of which is coupled to the rectifier (10); - A first switch (S _1A , T _i ), the first connection of which is coupled to the second connection of the energy store (C ₁ ), and the second connection of which is coupled to the connection point between the first decoupling _{diode (D 9} ) and the first connection of the semiconductor light source chain ( N ₁ , N ₂ , N ₃ ), the circuit arrangement being set up _{to charge the energy store (C 1} ) with the first switch (S _1A , T ₁ ) open in series with the first decoupling _{diode (D 9} ) and the semiconductor light source chain and with the first switch (S _1A , T ₁ ) closed, to discharge the energy store into the semiconductor light source chain via the decoupling _{diode (D 8).} Circuit arrangement for controlling semiconductor light sources (5) according to Claim 1 , characterized in that the first switch (S _1A , T ₁ ) is switched as a function of the instantaneous value of the rectified mains voltage (U _G ). Circuit arrangement for controlling semiconductor light sources (5) according to Claim 1 or 2 , characterized in that the semiconductor light source chain forms at least two segments (N ₁ , N ₂ ). Circuit arrangement for controlling semiconductor light sources (5) according to Claim 2 , characterized in that part of the rectified mains voltage (U _G ) is applied to the storage capacitor (C ₁ ). Circuit arrangement for controlling semiconductor light sources (5) according to Claim 1 , characterized in that a multi-pole network (V _N1 ) is coupled to the semiconductor light source chain and to the rectified mains voltage (U _G). Circuit arrangement for controlling semiconductor light sources (5) according to Claim 5 , characterized in that further switches (T ₆ , T ₈ , S ₂ , S ₃ ) are provided in the multi-pole network (V _N1 ), which connect part of the rectified mains voltage (U _G ) to a connection point according to the instantaneous value of the mains voltage (Uin) Apply between two segments or at a connection point of an LED string and a current limiter 3. Circuit arrangement for controlling semiconductor light sources (5) according to Claim 5 , characterized in that a first connection of the further switches (T ₆ , T ₈ , S ₂ , S ₃ ) each with a connection point between two LED strings (N ₁ , N ₂ ) or with a connection point of an LED String and the first decoupling diode (D ₉ ) is connected, and a second connection of the further switch is connected to a common reference potential. Circuit arrangement for controlling semiconductor light sources (5) according to one of the Claims 6 to 7th , characterized in that a further storage capacitor (C ₂ , C ₃ ) is connected in parallel to at least one segment. Circuit arrangement for controlling semiconductor light sources according to one of the preceding Claims 6 to 8th , characterized in that the further switches (T ₆ , T ₈ ) are current-controlled. Circuit arrangement for controlling semiconductor light sources according to one of the preceding claims, characterized in that the first switch (S _1A , T ₁ ) is controlled in such a way that it has a current-limiting effect on the current through itself or that in series with the first switch ( S _1A , T ₁ ) a current limiting device is provided for limiting the current through the first switch. Method for controlling semiconductor light sources (5) with a circuit arrangement according to FIG Claim 1 , characterized by the following steps: - serial connection of the storage capacitor (C ₁ ) with the LED cluster by opening the first switch (S _1A , T ₁ ), - charging of the storage capacitor (C ₁ ) by means of the input rectified mains voltage (U _G ), - Parallel connection of the storage capacitor (C ₁ ) with the LED string by closing the first switch (S _1A , T ₁ ), - Discharge of the storage capacitor (C ₁ ) into the semiconductor light sources (5)

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