DE102014221502A1 - Operating device for LEDs - Google Patents

Abstract

An operating device for lighting means (1), in particular a converter for at least one LED (1), comprises: - an actively clocked first converter stage (L51-c, L51-b, D52A, D52B) which supplies a storage capacitor (C54), and - A second converter stage (M60, D62, R72, R60, C61, 3), starting from which the lighting means (1) can be supplied; In this case, a discharge circuit (R73, M61) is provided in parallel with the capacitor (C54), which is activated at the same time as deactivating the timing of the first converter stage (L51-c, L51-b, D52A, D52B) in such a manner that after deactivation of the first converter stage Clocking of the first converter stage (L51-c, L51-b, D52A, D52B) a charge of the capacitor (C54) at least partially, preferably completely drained via the discharge circuit (R73, M61).

Description

The invention relates generally to control gear for lighting means such as. LEDs, including OLEDs are to be understood.

Modern energy-saving luminaires include, for example, light-emitting diodes (LEDs) as light sources. These already emit light at very low currents, since the I / U characteristic is essentially that of a normal diode. In an operating device for operating lamps usually capacitors and / or coils are installed. At least one operating device includes elements that have a (possibly parasitic) inductance or capacitance. During operation of a resource, energy is stored in all of these inductors and / or capacitances. When switching off or switching off the desired energization of the luminous means, the energy stored in the inductances / capacitances is slowly dissipated. At least partially, this energy thus causes a further flowing after the actual switching off current, which also flows through the light source and this brings about afterglow ("glow").

In the WO 2014/085837 A2 an operating device is presented to suppress the glow of bulbs. In this a radio interference suppression capacitor is connected between the primary side and the secondary side of a control gear. This is to suppress high-frequency interference during operation. This can be charged during operation as a parasitic effect. When switched off, the electrical charge of the capacitor causes a glow. To suppress this glow, the radio interference suppression capacitor is electrically disconnected from the operating device by means of a switch when the operating device is switched off. It will be in the WO 2014/085837 A2 but no means provided to suppress glare caused by capacitors and inductances of the control gear. Such capacitances and inductances can be, for example, electrical lines and / or storage and / or smoothing capacitors.

The object of the invention is also to suppress this effect. This object is achieved by a control gear according to independent claim 1. Advantageous developments are in the dependent subclaims.

According to the invention, the object is achieved by an operating device for lighting means, in particular a converter for at least one LED. This has an actively clocked first converter stage, which feeds a storage capacitor. A second converter stage supplies the bulbs. Parallel to the capacitor, a discharge circuit is provided, which is activated at the same time as deactivating the timing of the first converter stage such that after deactivation of the timing of the first converter stage, a charge of the capacitor at least partially, preferably completely drained via the discharge circuit.

Preferably, the first converter stage is formed galvanically isolated, for example. As an isolated series resonant converter (LLC).

Preferably, the second converter stage is a buck converter ("buck converter").

In an alternative advantageous embodiment, the second converter stage is an up-converter ("boost converter"). A boost converter is used in particular when it comes to a longer chain of bulbs in series. Even with an up-converter, advantageously the storage capacitor can be short-circuited directly, which is arranged between the first and the second converter stage. Thus, it is also ensured in the step-up converter that the second converter stage is no longer energized when the first converter stage is switched off due to the substantially simultaneous short-circuiting of the storage capacitor.

In a preferred embodiment, the discharge circuit consists of a series circuit of at least one ohmic resistor with a switch, which is preferably a transistor.

In a development, the switch is provided on the side of the ohmic resistor, which is preferably lower in potential magnitude, and is connected directly or indirectly thereto. As a result, the switch may possibly be controlled directly by a control circuit, for example an integrated circuit (IC). The other terminal of the switch is preferably led to ground potential.

Advantageously, the switch is driven by a control circuit via a driver circuit. In this way, the switch can also be arranged on a preferably higher magnitude potential.

In a further development, the two terminals of the discharge circuit are each at the same potential as the corresponding terminals of the capacitor.

In a particularly advantageous embodiment, the same control circuit controls the switching operation for switching on and off of the first converter stage and the switching operation for activating / deactivating the discharge circuit. This can be done directly or indirectly. This can the on / off switch simultaneously without appreciable delays, ie in real time happen. Thus, a visible to the human eye (Nach-) glow of the bulbs is prevented.

Additional functions, features and developments of the invention are illustrated in the embodiments, in the following drawings and explained in more detail. Like reference numerals designate units having the same or similar function.

In the 1 a circuit diagram of an anti-glow device for an operating device according to a first embodiment is shown.

In the 2 a circuit diagram of an anti-glow device for an operating device according to a second embodiment is shown.

In the 1 the secondary side of a first converter stage L51-c, L51-b, D52A, D52B, preferably a resonant converter (LLCs) is shown.

On the input side, the LLC is supplied, for example, on the basis of a rectified mains voltage. The first converter stage is preferably formed isolated. On the primary side, there may be a switch actively actuated by a control unit or 2 switches connected in series.

Preferably, the two outputs AL, AH of the first converter stage L51-c, L51-b, D52A, D52B are electrically connected by, for example, two, capacitors C52, C53. These are preferably connected in series. In particular, these serve to smooth the output voltage. The two outputs AL, AH feed a, preferably common, storage capacitor C54. This is thus connected to both low and high potential outputs AL, AH of the first converter stage L51-c, L51-b, D52A, D52B. Thus, this is parallel to the capacitors C52 and / or C53. Preferably, at least the output AL of the first converter stage L51-c, L51-b, D52A, D52B and / or the storage capacitor C54 is grounded. This is the output AL with the preferably lower potential. The other output AH is in the on state at the preferably higher magnitude potential.

In the further signal path, a light source is preferably indirectly provided by the first converter stage L51-c, L51-b, D52A, D52B via a capacitor C54 1 fed. This can be, for example, an LED, an LED chain, LASER, organic LED (OLED), a display and / or a light bulb. Also, according to the invention are series connections of the aforementioned lamps 1 possible. Here is the anode of the bulb 1 , Preferably the LED, at least indirectly connected to the output higher potential AH of the first converter stage L51-c, L51-b, D52A, D52B. The cathode of the bulb 1 is connected, for example, to a coil L60.

Am from the light source 1 opposite end of the coil L60 is a switch M60 a second converter stage or Bucks. This is preferably connected indirectly, particularly preferably via a resistor R61, to the output AL of the first converter stage L51-c, L51-b, D52A, D52B. This second output AL has the, preferably absolute, lower potential.

Between the coil L60 and the switch M60 go in an advantageous embodiment, two other branches. In the exemplary embodiment, these are at least indirectly connected to the anode of the luminous means 1 connected. Particularly advantageously, there is a diode D60 in one branch and a capacitance C60 in the other branch. Both branches end at the high potential AH.

So it is a self-contained circuit with the bulb 1 , the coil L60 and the diode D60 are preferably provided in the above order. Thus, the diode D60 blocks a DC current from the high potential terminal AH to the low potential terminal AL of the first converter stage L51-c, L51-b, D52A, D52B.

The output of the bulb 1 is preferably connected via at least one resistor R68 to the low-potential terminal AL. This allows the capacitor C54 via the light source 1 and discharge the at least one resistor R68. The output of the coil L60 is preferably connected to a further switch M60. This preferably consists essentially or exclusively of a transistor, in particular MOSFET, MESFET or bipolar transistor.

Preferably, a resistor R61 is in series with the switch M60. With this, among other things, the current can be limited, which flows through the switch M60. Also, the voltage drop across the resistor R61 can be measured. Advantageously, the switch M60 is arranged so that it can be driven with a preferably low magnitude voltage. This means that it is connected directly (not shown) to the low potential AL.

In the embodiment shown, the switch M60 can be arranged topologically, preferably directly, after the coil L60 in the circuit in the flow direction.

The operation of the device will now be described below. Between the outputs with the low or high potential AL, AH of the first converter stage L51-c, L51-b, D52A, D52B, a voltage difference is output or generated after switching on. This is smoothed by the capacitances C52 and C53. The capacitor C54 is then supplied to the voltage supply of the second converter stage M60, D62, R72, R60, C61, 3 charged.

Subsequently, the bulbs 1 with current flowing through. This partially flows in a first path via the two resistors R67, R68. These two resistors R67, R68 are connected in series and at least indirectly connected to the low potential output AL. The remaining part flows in a second path substantially via the coil L60, the opened switch M60 and the resistor R61.

In the process, the proportion of the current in the second path increases over time since the coil L60 limits the current in the second path to an ever-decreasing extent. If the current measured in the second path now exceeds a first threshold value, the switch M60 is closed. Alternatively, the current in the first path can also be determined and it can be determined whether it falls short of an alternative first threshold value. Also in this alternative measurement, the switch M60 is closed when falling below the alternative first threshold.

Thus no current flows in the second path. The current flow in the first path then increases abruptly. The coil L60 now discharges via the diode D50 and the bulbs 1 , Thus, the current sinking, which by the bulbs 1 and in the first path flows slowly, ie within fractions of milliseconds or in milliseconds. If the current measured in the first path now falls below a second threshold value, the switch M60 is opened again. Thus, the coil L60 recharges. The cycle can start anew. This process takes place at a frequency in the kHz range. The current flow through the LED 1 So is a sawtooth with a rising edge of a first slope and a falling edge of a second slope. By a suitable timing this process by the human eye as dimming of the bulbs 1 perceived since the human eye can not follow these high-frequency processes.

The measuring resistor R68 serves to measure the current amplifiers in the first path. The optional series resistor R 67 serves primarily to set the voltage that can be attacked via the measuring resistor R68.

As an alternative to the measurement of the second threshold value in the first path, the voltage across the lighting means 1 and / or the coil L60 are tapped.

If now the first converter stage L51-c, L51-b, D52A, D52B switched off, the storage capacitor C54 discharges slowly over the lamps 1 , In particular, if it is the bulbs 1 is about LEDs, it comes because of the still stored in the storage capacitor C54 electrical energy to glow the bulbs 1 , This glow can be visible to the human eye. Such a glow can also be generated by parasitic inductances, eg lines.

According to the prior art, this has hitherto been suppressed by connecting a switchable short circuit, in particular a short-circuitable transistor, parallel to the lighting means.

In this case, the switch M60 forms the output of the second converter stage M60, D62, R72, R60, C61, 3 , This is on the side of the LED track 1 arranged with low potential. In other words, this is at least substantially in series with the LED 1 connected. Thus, according to the prior art, a switch for selective short-circuiting must be switched to a, preferably at least absolute, relatively high potential.

According to the invention, a selective short-circuiting of an LED 1 not required. Instead or in addition, according to the invention, a resistor R73 is selectively connected in parallel with the capacitor C54 by means of a switch M61. It is both possible to arrange the switch M61 on the magnitude higher potential and the resistor R73 on the magnitude higher potential.

In the 1 It is shown that the resistor R73 is arranged at a higher potential than the switch M61. This ensures that the switch M61 can be controlled with a relatively low voltage, since the side facing away from the resistor M 61 side of the switch M61 is located on a magnitude low potential AL, preferably to ground.

Preferably, the switch M61 is thus directly connected by a control circuit, for example an integrated circuit IC, i. ASIC or microcontroller, controlled. In this case, the switch M61 can be actuated, at least indirectly, by the same control circuit IC as the first converter stage L51-c, L51-b, D52A, D52B.

An alternative embodiment is in 2 shown. The switch M61 is located in terms of absolute value, at a higher potential than the resistor R73. The switch M61 will be as in 1 illustrated embodiment also preferably driven by an IC. If the IC can generate a sufficiently strong drive signal, preferably drive voltage, the activation of the switch M61, preferably directly, is done by the control circuit IC. If the switch is a voltage-controlled transistor (MOSFET, MESFET or the like), can be necessary for the control of a particular magnitude, very high potential. Thus, a driver circuit Q60, Q61, R74, R75 can be connected between the IC and the switch M61. If the switch M61 is a current-controlled switch (eg bipolar transistor), a suitable driver circuit Q60, Q61, R74, R75 can also be connected between the control circuit IC and the switch M61.

Optionally, another capacitance C62 is parallel to the light source 1 connected. The two optional capacitors C60, C62 are used to suppress disturbing high-frequency signals. It can also be achieved with suitable dimensioning of the two optional capacitors C60, C62, that voltage spikes the bulbs 1 can not damage or are insensitive. However, the capacitances C60 and C62 should not be too large, otherwise they will cause the lamps to glow afterglow 1 is caused. This occurs in particular directly after switching off the power supply on the secondary side of the first converter stage L51-c, L51-b, D52A, D52B.

According to the invention, all the polarities and polarities in all described embodiments may be reversed. Such glow suppressants have the same operation as those just described and are expressly included in the described invention.

All described embodiments and feature are technically useful combined.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2014/085837 A2 [0003, 0003]

Claims (9)

Operating device for lamps ( 1 ), in particular converter for at least one LED ( 1 comprising an actively clocked first converter stage (L51-c, L51-b, D52A, D52B) which supplies a storage capacitor (C54) and a second converter stage (M60, D62, R72, R60, C61, 3 ), starting from the bulbs ( 1 ) are available; wherein a discharge circuit (R73, M61) is provided in parallel with the capacitor (C54), which is activated at the same time as deactivating the timing of the first converter stage (L51-c, L51-b, D52A, D52B) such that after deactivating the Clocking of the first converter stage (L51-c, L51-b, D52A, D52B) a charge of the capacitor (C54) at least partially, preferably completely drained via the discharge circuit (R73, M61).  Operating device according to Claim 1, in which the first converter stage (L51-c, L51-b, D52A, D52B) is an isolated converter, for example a series resonant converter LLC.  Operating device according to claim 1 or 2, wherein the first converter stage by means of one or more, in particular 2 series-connected and alternately clocked switches is clocked. Operating device according to one of the preceding claims, in which the second converter stage (M60, D62, R72, R60, C61, 3 ) is a buck down converter.  Operating device according to one of the preceding claims, in which the discharge circuit (R73, M61) has a series circuit of at least one ohmic resistance (R73) with a switch (M61), which is preferably a transistor.  Operating device according to Claim 5, in which the switch (M61) is provided on the potential-lower side of the ohmic resistor (R73) and is connected directly or indirectly thereto.  Operating device according to Claim 5 or 6, in which the switch is controlled by a control circuit (IC) via a driver circuit (Q60, Q61, R74, R75) or without the interposition of a driver circuit (Q60, Q61, R74, R75) starting from an output circuit. Pin of an integrated circuit (IC) is driven.  Operating device according to one of the preceding claims, in which the two terminals of the discharge circuit (M61, R73) each have the same potential as the corresponding terminals of the capacitor (C54).  Operating device according to one of the preceding claims, in which the same control circuit (IC) has the switch for clocking the first converter stage (L51-c, L51-b, D52A, D52B) and a switch (M61) for activating / deactivating the discharge circuit (M61, R73).

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