WO2013067564A1 - Procédé de fonctionnement d'au moins une del par vibrations - Google Patents

Procédé de fonctionnement d'au moins une del par vibrations Download PDF

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Publication number
WO2013067564A1
WO2013067564A1 PCT/AT2012/000289 AT2012000289W WO2013067564A1 WO 2013067564 A1 WO2013067564 A1 WO 2013067564A1 AT 2012000289 W AT2012000289 W AT 2012000289W WO 2013067564 A1 WO2013067564 A1 WO 2013067564A1
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WO
WIPO (PCT)
Prior art keywords
switch
led
current
low
time
Prior art date
Application number
PCT/AT2012/000289
Other languages
German (de)
English (en)
Inventor
Ueli Keller
Thomas Kueng
Original Assignee
Tridonic Gmbh & Co. Kg
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tridonic Gmbh & Co. Kg filed Critical Tridonic Gmbh & Co. Kg
Priority to DE112012004722.2T priority Critical patent/DE112012004722A5/de
Priority to EP12810034.4A priority patent/EP2777364B1/fr
Publication of WO2013067564A1 publication Critical patent/WO2013067564A1/fr

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/375—Switched mode power supply [SMPS] using buck topology

Definitions

  • the invention relates to an operating circuit with light emitting diodes according to the preamble of claim 1, a method for operating light emitting diodes according to the preamble of claim 8 and a method for operating light emitting diodes according to the preamble of claim 9.
  • LEDs have become an attractive alternative to conventional light sources such as incandescent or gas discharge lamps.
  • LED light-emitting diode
  • This term is intended below to include both light emitting diodes of inorganic materials as well as light emitting diodes of organic materials. It is known that the light emission of LEDs correlates with the current flow through the LEDs. For brightness control, LEDs are therefore always operated in a mode in which the current flow through the LED is controlled.
  • switching regulator such as buck converter
  • Step-Down or Buck Converter Such a switching regulator is known for example from DE 10 2006 034 371 A1.
  • a control unit controls a high-frequency clocked switch (for example, a power transistor).
  • a high-frequency clocked switch for example, a power transistor.
  • the switch When the switch is turned on, current flows through the LED assembly and a coil, which is charged by it.
  • the cached energy of the coil discharges in the off state of the switch via the LEDs (freewheeling phase).
  • the current through the LED arrangement shows a zigzag time course: when the switch is on, the LED current shows a rising edge, with the switch off, there is a falling edge.
  • the time average of the LED current represents the RMS current through the LED arrangement and is a measure of the brightness of the LEDs.
  • the average effective current can be controlled.
  • Switch typically in the range above 10 kHz, as low as possible.
  • a large fluctuation range of the current has a disadvantageous effect, especially with LEDs, since with change in the
  • the brightness of the LEDs can now be controlled by the time duration or the repetition frequency of the low-frequency PWM packets; For example, the LEDs can be dimmed by adjusting the width of the low-frequency PWM packets or the time interval between the low-frequency PWM packets.
  • the low-frequency PWM packets represent a form of low-frequency pulse packets, and the Changing the brightness is possible over various applicable changes in pulse modulations (pulse duration, pulse width, pulse rate, etc.).
  • a practical requirement of the operating device is that it can be used as flexibly and versatile as possible, for example, regardless of how many LEDs are actually connected as a load and should be operated.
  • the load may also change during operation if, for example, an LED fails.
  • a buck converter for the operation of at least one LED (or a plurality of LEDs connected in series), which has a switch S1 is shown as the basic circuit.
  • the operating circuit is supplied with a DC voltage or a rectified AC voltage U0.
  • the known circuits often require complex measuring circuits in order to achieve a current that is as constant as possible in order to measure the current through the LED during the switch-off phase; for example, this can be done by measuring the voltage across the LED, from which the current is deduced. But a differential voltage measurement at high potential is necessary.
  • the amplitude of the ripples should be as low as possible. This can be done by a suitable choice of the switch-on time tO and
  • Off time t1 done. For example, these times may be selected so that switch S1 is turned on when the power is on falls below a certain minimum reference value and the switch is turned off when the sitrom exceeds a maximum reference value.
  • the switch-on and switch-off time can also be set, for example, as a function of a detected mean value.
  • the operating circuit is supplied with a DC voltage or rectified AC voltage for at least one LED.
  • a supply voltage for at least one LED is provided by means of a coil and a switch clocked by a control / regulating unit, wherein when the switch in the coil, an energy is stored, which discharges when the switch is switched off via a diode and at least one LED.
  • control / regulating unit selects the duty cycle of the switch so that the current flow through the
  • At least one LED is as close as possible to the nominal value and preferably has the smallest possible ripple.
  • the operating circuit drives at least one LED, which is supplied with a DC voltage or rectified AC voltage, and which provides a supply voltage for at least one LED by means of a coil and a switch clocked by a control unit, wherein at switched on switch in the coil an energy is stored, which discharges when switched off switch via at least one LED.
  • a control unit controls the switch so that the LED current is controlled to a predetermined value, and for adjusting the brightness of the LED, low-frequency variable width PWM packets are respectively generated (by the control unit).
  • the switch-on time of the switch (S1) is changed to the next higher or lower adjustable switch-on time after several pulses of an adjustable switch-on time and the remaining pulses are output with this changed switch-on time, so that the number of pulses set with the two On times take a certain ratio and results in an average value of the current through the LED, which corresponds to the default by a target value.
  • the LED current is regulated to a predetermined value and the
  • Adjusting the brightness of the LED generates low-frequency PWM packets of adjustable width.
  • the on-time of the switch results from the average value of the current through the LED during a low-frequency PWM packet.
  • the switch-on time of the switch is increased by a duty value in addition to that from the
  • Control loop resulting value of the switch-on increased.
  • a method of operating at least one LED having a DC voltage or rectified AC voltage in which a supply voltage for at least one LED is provided by a clocked switch, wherein the switch is energized in a coil an energy is stored, which discharges when the switch is off via at least one LED, and a control / regulating unit the switch such controls that the LED current is regulated to a predetermined value and to set the brightness of the LED each low-frequency PWM packets of adjustable width are generated, wherein the switch-on of the switch from a
  • Control loop yields the current through the LED during one
  • Control loop resulting value of the switch-on time is increased.
  • the LED current can be measured in each case over a certain number of pulses of the high-frequency control and falls below a certain width for the
  • the duration of the measurement for determining the LED current can be reduced, and preferably the duration of the measurement does not exceed the width of the low-frequency PWM packet.
  • the invention also relates to a method for operating at least one LED, which is supplied with a DC voltage or rectified AC voltage, wherein the clocked by a switch
  • a control unit controls the switch such that the LED current (iLED) to a predetermined Value is regulated and to set the brightness of the LED respectively low-frequency variable width PWM packets are generated, the turn-on ratio of the switch results from a control loop for the current through the LED and the frequency of the switch is constant, and at the beginning of a low-frequency PWM -weles the turn-on time of the switch is increased by an impact value in addition to the value of the turn-on time resulting from the control loop.
  • the operating circuit comprises a sensor unit which generates a sensor signal and monitors the current through the LED.
  • control unit uses a signal of the sensor unit or a combination with the signal of an optional further sensor unit for determining the switch-on ratio of the switch.
  • the sensor unit is formed by two mutually coupled energy storage elements, for example by a transformer or a Hall sensor.
  • the operating circuit has a
  • Capacitor which is arranged parallel to the at least one LED, and which maintains the current through the LED during the phase of demagnetization of the coil, so that the current is smoothed by the LEDs.
  • FIG. 1 a shows a circuit arrangement according to the known prior art
  • FIG. 1b shows a diagram with the time profile of the LED current in the circuit arrangement of FIG. 1a (prior art).
  • FIG. 2 a shows a first example of an operating circuit (buck) according to the invention for LEDs.
  • Figure 3a and Figure 3b show specific embodiments of the invention.
  • FIG. 4 shows a further embodiment of the invention
  • FIG. 5 shows a further embodiment of the invention (Buck Boost).
  • FIG. 6 shows a further embodiment of the invention for the LED
  • FIG. 7 shows a graphic representation of a possible signal curve according to the invention
  • FIG. 8 shows a further embodiment of the invention
  • FIG. 9 shows a further embodiment of the invention
  • Figure 10 is a graphical representation of a possible Signalverlauf according to the invention
  • Figure 11 is a graphic representation of a possible signal waveform according to 'the invention.
  • Figure 12 is a graphical representation of the setting of the color locus according to the prior art
  • Figure 13 is an illustration of the adjustment of the color locus according to the invention.
  • Figure 1 a and Figure 1 b show the prior art.
  • the circuit arrangement shown in Figure 2a is used to operate at least one (or more in series or parallel) LED.
  • at least one LED or more in series or parallel LEDs
  • two LEDs are connected in series, it can of course be only one or more LEDs.
  • the LED or the serially connected LEDs are hereafter
  • the LED or also called LED track.
  • An advantage of the present invention is that the operating circuit adapts very flexibly to the type and number of serially connected LEDs.
  • the circuit is supplied with a DC voltage U0, which of course can also be a rectified AC voltage.
  • the LEDs are connected in series with a coil L1 and a switch S1.
  • the switch S1 the switch
  • circuit arrangement a diode D1 (the diode D1 and the coil L1 are connected in parallel with the LEDs) and optionally a capacitor C1 connected in parallel to the LEDs on.
  • a diode D1 the diode D1 and the coil L1 are connected in parallel with the LEDs
  • a capacitor C1 connected in parallel to the LEDs on.
  • Capacitor C1 charged. During the turn-off phase of the switch S1 (freewheeling phase), the capacitor C1 discharges and contributes to the flow of current through the LED track. With suitable dimensioning of the optional capacitor C1, this can lead to a smoothing of the current through the LEDs.
  • the coil L1 may also be part of a power transmitting transformer.
  • switch S1 a field effect transistor is preferably used.
  • the switch S1 is switched to high frequency, typically in one
  • the current can be measured by the LED and thus at a predetermined value or in a predetermined
  • control and / or regulating unit SR (hereinafter also referred to as control / regulating unit SR) is provided which specifies the timing of the switch S1 to control the LED power or the LED current iLED.
  • the control unit SR uses for
  • the sensor unit SE1 designated.
  • the sensor unit SE1 allows a
  • the sensor unit SE1 Measurement during the switch-on phase of the switch S1 and is therefore referred to as the sensor unit SE1.
  • the sensor unit SE2 is arranged within the current branch, which is traversed by the current during the freewheeling phase, preferably in series with the LED or alternatively also in series with the coil L1 (designated as SE2 '). With the aid of the sensor unit SE2, the current through the LED can be determined directly or indirectly.
  • the sensor unit SE2 can also be a current mirror, a Hall sensor or a transformer or it can also be a voltage measurement on the LED.
  • switch S1 is closed and current begins to flow through the LED and coil L1.
  • the current i_L shows an increase according to an exponential function, wherein in the range of interest here a quasi-linear increase of the current iLED and i_L takes place.
  • iLED differs from i_L in that part of the i_L is used to charge the i_L
  • Condenser C1 contributes.
  • the opening of the switch S1 at time t_1 has the consequence that the energy stored in the magnetic field of the coil L1 is discharged via the diode D1 and the LEDs or the capacitor C1.
  • the current i_L continues to flow in the same direction, but decreases continuously and can even reach a negative value.
  • a negative current (i.e., reverse current flow) can be achieved when coil L1 demagnetizes. This is present as long as the charge carriers, which were previously enriched in the conducting-poled diode D1, are eliminated from the barrier layer of the diode D1.
  • the current iLED decreases only weakly and is maintained because the capacitor C1 has a smoothing effect. At time t_2, so if the
  • a reclosing time t_3 for the switch S1 can be given if the current i_L falls below a predetermined minimum value.
  • a switch-on time t_3 for the switch S1 can also be given when the current i_L reaches the zero crossing, or at least the vicinity of the zero crossing. At this time, the coil L1 is not or
  • the switch S1 can be turned on at this time with very low losses, since hardly any current flows through the coil L1. Since according to the invention, the switch S1 preferably with a fixed
  • the duty cycle due to the control loop is to be selected so that the current through the LED by the desired nominal value of the LED current oscillates.
  • the switch S1 can be controlled by the control / regulating unit SR such that it is regulated by the LED to a predetermined nominal value of the current iLED.
  • the sensor unit SE1 is arranged in series with the switch S1 and detects the current flow through the switch S1. This serves to monitor the flow of current through the switch S1. If the current flow through the switch S1 exceeds a certain maximum reference value, the switch S1 is turned off.
  • the further sensor unit SE1 can be, for example, a measuring resistor (shunt), as shown later as measuring resistor RS in the examples of FIGS. 3 to 5.
  • Measuring resistor (shunt) RS are tapped and compared for example by means of a comparator with a reference value. If the voltage drop at the measuring resistor (shunt) RS exceeds a certain value, the switch S1 is switched off. The monitoring by means of
  • Sensor unit SE1 can be used additionally or alternatively to the sensor unit SE2 for determining the switch-on ratio of the switch S1. It can also be used as protection of the switch S1 against overcurrents in the event of a fault (in such a case, the switch S1 can be opened immediately). As already mentioned, the sensor unit SE2 can serve to detect an advantageous switch-on ratio for switch S1.
  • the current i_L through the LED by means of
  • the current iLED through the LED or alternatively the current i_L through the coil L1 can also be detected, for example, by means of a Hall sensor.
  • the sensor unit SE2 is a series of the LED-connected transformer with a primary winding T1) and a secondary winding T2.
  • a measuring element RM is arranged in series with the secondary winding T2, so that a secondary circuit is formed, wherein in the
  • Secondary winding T2 a defined current is fed and at least one measurement takes place on the secondary side.
  • the monitoring of the temporal voltage curve on the secondary side T2 allows a statement about the advantageous turn-on ratio of the switch S1. Since this measurement of a DC current is made possible, no hysteretic control must be used, but it can also be applied to a control loop, in which only a measured value of the LED current iLED is evaluated as the actual size.
  • the control unit SR can control the switch S1 such that the LED current iLED is regulated to a predetermined value.
  • the control unit SR uses the information from the sensor unit SE1 and / or the sensor unit SE2 to determine the
  • the control for adjusting the current through the LED by the control unit / control unit SR thus takes place in the form of a PWM control.
  • the regulation of the (time-averaged) LED power by the control unit / control unit SR for adjusting the brightness LED is preferably carried out in the form of low-frequency pulse packets (PWM packets).
  • the frequency of the low-frequency PWM packets is typically of the order of 100-1000 Hz.
  • the control unit SR controls the switch S1 so that the current (iLED) is controlled by the LED to a predetermined value and to set the brightness of the LED respectively low-frequency PWM packets of adjustable width are generated,
  • the turn-on time of the switch S1 results from the average value of the current through the LED during a low-frequency PWM packet, and at the beginning of a next low-frequency PWM packet, the turn-on time of the switch S1 becomes a duty value in addition to the value resulting from the control loop Turn-on time increased.
  • the value of the current (iLED) through the LED can be determined by means of a measurement of the current flowing through the switched-on switch S1.
  • the value of the current (iLED) through the LED with can also help one
  • Measurement of the voltage drop across the LED can be determined.
  • the turn-on time can be increased by the turn-on value until the nominal amplitude of the low-frequency PWM packet has been almost or completely reached.
  • a predetermined number of one or more high-frequency pulses with an impact value can be increased, in which case the number of applied pulses may depend on the brightness value and / or the distance to the nominal value.
  • the increase of the switch-on time by an impact value can, for example, also take place only at low brightness values.
  • the impact value can be added when reaching the
  • the impact value may additionally or alternatively also to others
  • Times within a low-frequency PWM packet can be added or subtracted, for example, it can be at the end of a
  • the control unit SR can be formed by a microcontroller which has only a limited resolution for generating PWM signals (for example for the output of high-frequency pulses).
  • Control unit SR controls the switch S1 so that the LED current (iLED) is controlled to a predetermined value and for adjustment the brightness of the LED each low-frequency PWM packets of adjustable width can be generated.
  • the turn-on time of the switch S1 results from a control loop which is intended to maintain the current through the LED at a nominal value during a low-frequency PWM packet, and at the beginning of a next low-frequency PWM packet the turn-on time of the switch S1 is increased by an additional value increases from the control loop resulting value of the switch-on time.
  • a method is also provided for operating at least one LED, to which a DC voltage or rectified AC voltage is supplied, in which the switch S1 provides a supply voltage for at least one LED, whereby when the switch S1 is energized in a coil L1, an energy is stored, which is at
  • a control unit SR the switch S1 controls such that the LED current (iLED) is controlled to a predetermined value and for adjusting the brightness of the LED each low-frequency PWM packets of adjustable width are generated , wherein the turn-on ratio of the switch S1 results from a control loop for the current through the LED and the frequency of the switch S1 is constant, and at the beginning of a low-frequency PWM packet, the turn-on time of the switch S1 by an additional value in addition to that from the control loop resulting value of the switch-on time is increased.
  • Figs. 3 (3a and 3b).
  • an operating circuit for at least one LED is shown, to which a DC voltage or rectified AC voltage is supplied, and which provides a supply voltage for at least one LED by means of a coil L1 and a clocked by a control / regulating unit SR switch S1.
  • a control / regulating unit SR switch S1 When the switch S1 is in the coil L1, an energy buffered, which turns off when switch S1 at least one LED discharges.
  • the operation circuit can be controlled so that the control unit SR determines the duty ratio of the switch S1 depending on the measurement of the current iLED by the LED.
  • the control / regulation unit SR can determine the current through the LED by means of a series-connected to the LED transformer with a primary winding T1 and a secondary winding T2. It can the
  • Control / SR unit feed a rising current in the secondary winding T2 of the transformer. This is preferably done by a current source loff arranged in the control / regulation unit SR.
  • the control unit SR can monitor the voltage across the secondary winding T2 of the transformer via an analog-to-digital converter ADC. Thus, the current is measured by the LED iLED by means of a sensor unit SE2 using a transformer.
  • the defined current which is fed into the secondary winding T2 by the current source loff, may be a triangular current.
  • the defined current which is fed into the secondary winding-T2 by the current source loff, can also be a triangular current with a fixed DC component DC offset.
  • the defined current which is fed into the secondary winding T2 by the current source loff can also be, for example, a DC reference current having a fixed amplitude, to which an AC voltage component having a defined value
  • the defined current may have a different stability, this may in particular be the case when saturation in the secondary winding T2 is reached.
  • different signal forms may be advantageous for the defined current, and the method for evaluating the measurement on the secondary side may be adapted to the type of current source loff used.
  • a current measurement is made possible by the very accurate monitoring of a current can be determined, wherein the current can also be a direct current. In this case, this current measurement can be carried out such that a potential separation between the current path to be measured and the measuring evaluation circuit (T2 and SR) is given.
  • the current to be measured (which, as already mentioned, may also be a direct current) has an amplitude which exceeds that
  • Saturation current of the transformer is located, preferably the current to be measured is significantly higher than the saturation current of the transformer to ensure a reliable measurement.
  • the transformer is operated in saturation when the current to be measured with a corresponding amplitude flows through the transformer (i.e., through the primary winding T1).
  • fed current corresponds to the primary side monitored stream.
  • the secondary winding T2 goes into Saturation, which can be recognized by a secondary-side monitoring (for example via the measurement at the resistor RM).
  • a detectable increase in the voltage drop across the resistor RM would occur across the resistor RM as soon as the secondary winding T2 saturates.
  • the primary winding T1 forms a first energy storage element, wherein a current flows through the LED and through the primary winding T1 as a first energy storage element, wherein the primary winding T1 as the first
  • Energy storage element is coupled. If the primary winding T1 as the first energy storage element due to the current through the LED has reached its maximum energy storage capacity (ie in saturation), and in secondary winding 12 as the second energy storage element, a defined current is fed with preferably increasing amplitude, so the time be recognized, to which the first
  • Energy storage element again achieved an energy storage capability, ie the primary winding T1 leaves the state of saturation.
  • a control unit SR can monitor the voltage across the secondary winding T2 via an analog-to-digital converter ADC, for example at the measuring point C3 on the resistor RM. Instead of an analog-to-digital converter ADC, however, the measurement can also take place, for example, by means of a comparator. Once the monitored voltage a the
  • Comparator fed reference voltage can so
  • the transformer is no longer in saturation due to the LED current on the primary side.
  • the difference between the two embodiments according to FIG. 3 a and FIG. 3 b is that in the example according to FIG. 3 a the control unit SR has only one terminal C2 for the supply of the defined one Current in the secondary winding T2 and the monitoring of
  • control unit SR is designed such that it can both supply a current via the same connection (by means of the integrated current source loff as well as simultaneously
  • Voltage at the terminal C2 can monitor (by means of an analog-to-digital converter ADC), so as to perform the measurement on the secondary winding T2.
  • control unit SR is designed such that it can flow through a first terminal C2 in the
  • Secondary winding T2 can feed (by means of the integrated current source loff) and by means of the terminal C3, the voltage across the resistor RM can monitor (by means of an analog-to-digital converter ADC), so as to perform the measurement on the secondary winding T2.
  • Measured values are recorded within a given time interval and evaluated together.
  • the voltage across the resistor RM can be detected at the time when it is determined that the transformer is no longer due to the LED current on the primary side is in saturation or is again in saturation.
  • the maximum peak value of the voltage across the resistor RM which is reached when the current fed into the secondary winding T2 reaches its maximum value, can also be detected.
  • the monitoring at the terminal C2 can also be done by means of a comparator.
  • a comparator may be preferably provided for evaluation, which constantly toggles (ie in particular the reference switches) to both To be able to use flanks of the defined current for monitoring. For example, different references for the rising and falling edge may be provided.
  • the signal can also be monitored and evaluated over time.
  • the time duration can be monitored until it is determined that the transformer is no longer in saturation due to the LED current on the primary side.
  • the reference of the comparator can for example also be specified by a digital-analog converter.
  • the control unit SR can perform the measurement of the current such that the defined current is fed to the secondary winding T2 by the current source loff only during the switch-off phase of the switch S1.
  • the control unit SR can measure the current iLED through the LED (by means of the voltage across secondary winding 12) during the
  • the current can be measured by the LED by means of a sensor unit SE2 by means of a transformer.
  • the sensor unit SE2 can also be a Hall sensor, in particular be formed by mutually coupled elements of a Hall sensor.
  • FIGS 4 and 5 show specific embodiments of the invention.
  • FIG. 4 shows a modification of the circuit in FIG. 3 in that, in addition, a second switch S2 is arranged parallel to the LEDs and the capacitor C1.
  • the switch S2 is selectively / independently controllable and may for example be a transistor. If the switch S2 is closed, the discharge process of the capacitor C1 is accelerated. Due to the accelerated discharge of the capacitor C1 is achieved that the
  • the switch S2 may be activated and driven at a low dimming level where the low frequency PWM packets are very short and it is important that the current through the LED rapidly approaches zero at the end of a low frequency PWM packet.
  • a low dimming level can be achieved by suitable control of the switch S2.
  • Another function of this switch S2 is that it bridges the LEDs when switched on. This is necessary, for example, when the LEDs are to be switched off, ie, to emit no light, but the supply voltage U0 is still present. Without the bridging by the switch S2, a (smaller) current across the LEDs and the
  • Resistors R1 and R2 flow and the LEDs (slightly) light up.
  • Embodiments of the invention can be applied.
  • inventive method can of course be applied to other circuit topologies, such as for a so-called buck-boost converter, a half-bridge converter or a so-called forward converter (Durchflußwandler).
  • FIG. 5 shows a modification of the circuit of Figure 2a in that the arrangement of the inductor L1, the diode D1 and the orientation of the LED track is modified.
  • the circuit shown represents a so-called.
  • Buck-boost converter also referred to as inverter circuit, is.
  • a transformer with a primary winding T1 and a secondary winding T2 is arranged in series with the LED.
  • a measuring element RM is arranged in series with the secondary winding T2, so that a secondary circuit is formed, wherein in the secondary winding T2, a defined current is fed and at least one measurement takes place on the secondary side for monitoring the LED current iLED.
  • Fig. 6 shows a section of an operating circuit for at least one LED analogous to the circuits of the previous examples.
  • Such an operating circuit typically drives at least one LED to which a DC voltage or rectified AC voltage is applied, and which provides a supply voltage for at least one LED by means of a coil L1 and a switch S1 clocked by a control unit SR, with switch S1 in the Coil L1 is cached an energy that discharges when switched off switch S1 via at least one LED, wherein in series with the LED on
  • Transformer having a primary winding T1 and a secondary winding T2 is arranged, and a measuring element RM is arranged in series with the secondary winding T2, so that a secondary circuit is formed, wherein in the
  • Secondary winding T2 a defined current is fed and at least one measurement takes place on the secondary side.
  • the defined current IM is fed to the secondary winding T2 through a current source loff, which is connected to the secondary winding T2.
  • the measuring element may be a resistor RM (eg a current measuring shunt). By means of the measurement, the current iLED on the secondary side can be determined by the " LED.
  • the defined current IM which is fed to the secondary winding T2 as the coupled winding, may be a triangular current.
  • the time can be detected when the injected triangular current exceeds the current iLED through the LED.
  • This time can be detected by a voltage monitoring or measurement on the secondary winding T2 as a coupled winding.
  • Delta current reaches a value that the transformer stops due to the LED current iLED on the primary side is in saturation.
  • This time can be detected by a voltage monitoring or measurement on the secondary winding T2 as a coupled winding. Based on the detected time can be closed on the amount of current iLED through the LED.
  • the winding ratio of the transformer can be taken into account when determining the current.
  • the winding ratio of the transformer is one to one (1: 1).
  • the transformer may form the sensor unit SE2.
  • the sensor unit SE2 can also be a Hall sensor, in particular the sensor unit SE2 can be formed by elements of a Hall sensor which are coupled to one another.
  • a capacitor C1 may be disposed in parallel with the at least one LED, and maintains the current iLED through the LED during the phase of demagnetization of the coil L1, so that the current iLED is smoothed by the LEDs.
  • a switch S2 may be arranged in parallel to the capacitor C1 and the LEDs and be independently controllable. The switch S2 can be closed to accelerate the discharging operation of the capacitor C1.
  • a control unit SR can monitor the voltage across the secondary winding T2 via an analog-to-digital converter ADC.
  • the mutually coupled energy storage elements thus form the sensor unit SE2 and can be formed by magnetically coupled windings of a transformer T1, T2.
  • the switching regulator circuit forms an operating circuit for at least one LED.
  • FIG. 7 shows an exemplary measurement sequence for an LED illumination with three independent LEDs.
  • the LEDs are each fed by an operating circuit.
  • the LED current (iLED) is set to one for all three channels
  • Fig. 7 shows in the upper part the current through the first LED (fed by a first operating circuit) and below the current through the switch S1 of the first operating circuit. Below this is shown an exemplary sequence of low-frequency PWM packets for three LEDs each driven by an operating circuit and also the sequence of the measurements is indicated by the hatched blocks.
  • the current through the LED is preferably measured during the half of the switch-on time of the switch S1.
  • Switching ratio and the frequency can be determined due to this measurement of the average current through the LED.
  • the switch-on time of the switch (S1) results from the averaged value of the current through the LED during a low-frequency PWM packet and the subsequent low-frequency PWM packets are sent with the
  • Switching ratio driven as determined by the measurement during the previous low-frequency PWM packet.
  • the value of the required switch-on ratio can also be used for several reasons
  • low-frequency PWM packets are maintained, for example, if not measured at each low-frequency PWM packet. This may for example be the case when the same input of a
  • Control unit SR is used for measuring the currents at several LEDs. In the example of Fig. 7, the three are sequentially
  • the first LED (LF PWM Channel 1) then the second LED (Channel 2), then the third LED (LF PWM Channel 3) and then the first LED is monitored during a low-frequency PWM packet.
  • the LED current is measured and evaluated for a certain time at the end of a low-frequency PWM packet. In this case, at least the period of N high-frequency pulses (for example, 16) for measuring the current can be used for each packet.
  • the switch-on time of the switch (S1) is now increased by an impact value which is added in addition to the value of the switch-on time resulting from the control loop.
  • FIGS. 9 and 8 shows the control according to the invention of the switch S1 by the control unit SR, as shown for example in FIGS.
  • the control unit SR controls the first switch S1 with a dimming signal, wherein the dimming signal is generated by a combination of a low-frequency signal and a high-frequency signal.
  • the low-frequency signal may be at a first output (PWM_LF) and the high-frequency signal at a second output (PWM_HF)
  • Control unit SR are output.
  • the first output (PWM_LF) and the second output (PWM_HF) can be linked via a coupling element.
  • the coupling element can be formed by an ohmic resistor (resistor).
  • the second output (PWM_HF) can be designed as an open collector output within the control unit SR.
  • the low-frequency signal is a pulsed, in particular PWM signal, in particular in the range of about 100 Hz.
  • the high-frequency signal is a pulsed, in particular PWM signal,
  • the dimming signal via which the brightness of the LED is adjusted, is thus formed from pulse packets, preferably as a resulting PWM signal, the pulse packets being interrupted by longer pauses.
  • the dimming signal via the control of the switch S1 is the
  • the dimming signal can be dependent on a brightness preset from outside, for example by a user.
  • This brightness specification can be supplied by the
  • low-frequency signal can be influenced.
  • the low-frequency signal may be dependent on the desired dimming level of the LED.
  • the low-frequency signal may also be from another integrated control circuit, such as a microcontroller, as central controller is arranged to be specified (HL) and looped through only by the control unit SR.
  • the low-frequency signal can also be specified by a further microcontroller, which is arranged as a central controller, and does not necessarily have to be output or looped through by the control unit SR.
  • the high-frequency signal may be dependent on the current and / or the voltage through the LED.
  • the high-frequency signal is dependent on a control loop, wherein depending on at least one predetermined setpoint value for a current and / or a voltage within the operating circuit and the comparison with an actual value at least the first switch S1 is clocked by a high-frequency control.
  • the control loop wherein depending on at least one predetermined setpoint value for a current and / or a voltage within the operating circuit and the comparison with an actual value at least the first switch S1 is clocked by a high-frequency control.
  • the switch S1 is switched on and off depending on the set duty cycle. Regardless of the current brightness of the LED, this control loop does not necessarily have to be taken into account.
  • the turn-on time of the high-frequency signal is temporarily increased by an impact value, for example, as long as the nominal value of the LED current is not reached or after the onset of a high level of the low-frequency signal.
  • the invention provides the advantage that the control loop for the regulation of the current through the LED can be decoupled from the specification of the brightness and still a control of the switch via a single drive signal is possible (the link from the high-frequency signal of the control loop with the low-frequency signal for the brightness is externally linked to the control unit SR).
  • the control unit SR can be formed by a microcontroller, FPGA, PAL or even an application-specific integrated circuit.
  • the control according to the invention is not based on the topology or
  • this invention can be applied to a buck converter, boost converter, buck-boost converter, isolated flyback converter, cuttlefish converter, or other topologies and circuitry.
  • the invention relates generally to operating circuits for at least one LED, which are supplied by means of a switching regulator via a clocked first switch S1, wherein the frequency and / or the duty cycle of the clocked switch S1, the current is influenced by the LED, and the frequency and / or the duty cycle of the clocked switch S1 is predetermined by a control unit SR by means of a dimming signal as a drive signal, wherein the dimming signal is generated by a combination of a low-frequency signal and a high-frequency signal.
  • the low-frequency signal (LF) and the high-frequency signal (HF) are preferably linked via a coupling element.
  • the control unit SR can output both the low-frequency signal at a first output (PWM_LF) and the high-frequency signal at a second output (PWM_HF).
  • control units SR of the individual operating circuits can be controlled by a common microcontroller. It would also be possible, the function of the central control of the individual
  • the microcontroller can be controlled via an interface (wireless or wired). In this case, control signals for adjusting the brightness or color or status information can be transmitted via the interface.
  • a method for driving at least one LED is made possible, wherein the control unit SR the switch S1 with a dimming signal drives, and wherein the dimming signal is generated by an external combination of a low-frequency signal and a high-frequency signal.
  • FIG. 0c shows an advantageous implementation of the method according to the invention. This method is used to control an electrical
  • a high-frequency PWM signal is used with adjustable in discrete steps duty cycle.
  • Switching regulator is used with at least one active clocked switch such as a buck converter, and the power supplied to the LED or the current is set by the setting of the duty cycle of the active clocked switch. To achieve the predetermined current or power value, the duty cycle is dependent on exceeding or falling below the predetermined current or power value
  • predetermined current or power value is a repeated change between the two steps of the discretely variable Einschaltrise, which occur due to the control loop, wherein the repeated change takes place according to a predetermined pattern.
  • the duty cycle is set such that the instantaneous average does not match the value of the desired average reached.
  • This situation can occur with limited resolution of the possible switch-on time both in an open loop operation and in a closed loop control mode.
  • An increase in the switch-on time may, with a limited resolution of the possible switch-on time, result in an increase of the switch-on time by one step exceeding the desired value for the LED current ILED (shown in FIG. 10b).
  • the limited resolution of the possible turn-on time it may not be possible to achieve the desired average value for the LED current.
  • FIG. 10c A solution according to the invention for the problem described with reference to FIGS. 10a and 10b is shown by way of example in FIG. 10c.
  • the first switch S1 is preferably regulated in such a way that, based on the setting of the switch-on ratio at a fixed frequency, the switch S1 is activated such that an average value of the LED current ILED which corresponds to the predetermined desired value is established.
  • the high-frequency control (by means of a high-frequency signal) of the switch S1 can thus be dependent on the current and / or the voltage through the LED.
  • the high-frequency control of the switch S1 is dependent on a control loop, wherein depending on at least one predetermined setpoint value for a current and / or a voltage within the operating circuit and the comparison with an actual value at least the first switch S1 is clocked by a high-frequency control.
  • the operating circuit can also be in a continuous
  • the switch S1 is switched on and off depending on the comparison of a setpoint with an actual value of the average LED current. If it is now determined that despite the control loop, the desired target value can not be achieved, but only an average in the vicinity of the setpoint, then a repeated change between the two
  • the repeated change takes place according to a predeterminable pattern.
  • the predefinable pattern can be selected, for example, by the distance between the desired value and the current actual value. It can, for example, at least temporarily operation only with a
  • Mean value are determined to the predetermined setpoints and depending on the pattern for the change of the duty cycle are adjusted.
  • a higher number of the higher switch-on time (or switch-on ratio) can be selected if it is determined that the operating average above the desired setpoint value is located closer to the setpoint value than the resulting average value during operation below the desired value during operation above the desired setpoint value
  • the change can be changed, that is, it can be the number of successive steps with the same switch-on can be changed.
  • the resulting average of the on-time is
  • the control unit SR can know the ratio of the switch-on time and the resulting LED current or in an initialization phase and, for example, in a value table or by means of a function to determine the dependence of the LED current on the switch-on time or the duty cycle is stored.
  • the corresponding value for the switch-on time or the switch-on ratio can then also be selected based on the LED current to be set by means of the known dependence of the LED current on the switch-on time or the switch-on ratio. If it is now determined that the desired value can not be achieved by an adjustable value of the switch-on time, preferably the necessary number of available next higher and lower values for the switch-on time can be determined and the triggering ng of the switch S1 can be determined with a
  • a change by one LSB of the PWM register of the control unit SR may cause a 32mA change in the LED current.
  • the PWM value X can give an LED current of 380 mA.
  • the next higher PWM value X + 1 can thus produce an LED current of 412 mA.
  • the average current is 392 mA.
  • the default for the current through the LED can be done for example by a specification for the color to be set of the LED module to be operated. Even if the LED lighting system is formed by a plurality of differently colored LEDs (for example, three LED channels as described in the examples) and is used for color mixing, for the
  • Control unit SR can be set if the LED is to be operated accordingly.
  • the determination of the combination to be set from the switch-on times to be set for a low-frequency PWM packet or at least one pulse sequence can also be based on a measurement of the LED current during a preceding low-frequency PWM packet, as this possibility has been explained with reference to FIG.
  • a preferred variant of the method for adjusting the high-frequency signal control of an electrical load preferably a light source, such as, for example, LED or OLED will be explained according to FIG.
  • a pulse signal is used with adjustable in discrete steps on time.
  • the current ILED is controlled by an LED via the setting of a
  • the current ILED desired operating parameters (the current ILED) to achieve.
  • the on time for the pulse signal is increased by a discrete step, the set current ILED is higher than the desired value of the current ILED ( Figure 10b).
  • the pulse signal will go through a combination of two pulse sequences with different switch-on time is formed, wherein these are selected such that the first pulse sequence has a switch-on time which is closest to the specification for reaching the desired operating parameter, and the second pulse sequence in its
  • the detected current would be averaged (integrated) and then compared with a setpoint.
  • ASIC integrated circuit
  • microprocessor microprocessor or hybrid thereof, which is used to carry out such
  • Method is formed. It can be a control gear for bulbs, in particular LEDS or OLEDs are constructed, comprising a
  • a lighting module comprising lighting means, in particular LEDs or OLEDs, as well as an operating device according to the invention.
  • a lighting system comprising at least one lighting module according to the invention, which is connected via a signal line to a central unit, which is designed for the transmission of dimming specifications, in particular according to the DALI standard, be established.
  • the invention can also be applied to a PWM operation, where the adjustment of the brightness by means of low-frequency pulse packets (typically with a frequency in the range of 100- 000 Hz) are controlled with a mean time constant current amplitude, these pulse packets each by a high-frequency control the operating device,
  • a clocked switch S1 in particular a clocked switch S1,. be formed.
  • a low-frequency and a high-frequency control are superimposed.
  • the current within a pulse packet has a high-frequency ripple.
  • the invention can now be used to adjust the amplitude during the high phase of a low frequency PWM packet.
  • a signal which has a duty cycle of 10% for the low-frequency PWM packet.
  • the high-frequency signal for setting the LED current during a low-frequency PWM packet is here also from a
  • the setting of the desired average on-time can be done via a combination be possible from a sequence of pulses with two different on-times only up to a certain number of pulses. If too few pulses are available within a low-frequency PWM packet, it is no longer possible to exactly reach the desired current through the LED since a corresponding combination of on-times is not adjustable. However, it can fall below a certain minimum width of the low-frequency PWM packet in an operating mode
  • Monitoring window for measuring the LED current to be reduced. For example, instead of 16 pulses, only 8 pulses can be measured (with reference to FIG. 7)
  • Fig. 11b An example of such an operating mode is shown in Fig. 11b.
  • this mode individual pulses of the on-time to be selected can be omitted since the possible counting of the pulses is limited.
  • such an operation can take place that within a low-frequency PWM packet a pulse of the higher switch-on time is omitted and in the subsequent low-frequency PWM packet a pulse of the lower switch-on time is omitted.
  • the self-adjusting LED current can be averaged out again.
  • Charging value for the switch-on can be set or the tuning of the pulse train can be done with pulses with different on-time.
  • the basis is the well-known generation of a PWM pulse sequence shown in FIG. 12 for setting the color location on the basis of the light emitted by a light source by changing the pulse width of the pulses of the pulse sequence and thus of their duty cycle.
  • a PWM pulse sequence shown in FIG. 12 for setting the color location on the basis of the light emitted by a light source by changing the pulse width of the pulses of the pulse sequence and thus of their duty cycle.
  • a central digital control signals generated (or otherwise generates control signals) from which by means of a microprocessor provided on the receiving side, a pulse train for control
  • pulse width modulated pulses which ultimately serve to adjust the brightness of the light emitted by the light source.
  • the change in the duty cycle of the PWM pulses is carried out according to the resolution of the microprocessor in discrete steps.
  • the resolution for example between 10 and 14 bits, may be less than the resolution of the dimming preset value, if this is digital or analog (quasi infinitely fine resolution).
  • FIG. 12 shows, by way of example, the setting of the duty cycle of FIG
  • Lamp groups here for the colors red, green and blue. In this way, any color can be set in RGB space.
  • the pulse width is set accordingly for each of the lighting groups.
  • FIG. 13 shows a detail of a pulse train according to the invention with a pulse repetition frequency of, for example, 100 Hz (1 / T). ,
  • Dimming control of an electrical load preferably one
  • Illuminant such as. LED or OLED
  • the illuminant has at least two independently controllable groups of bulbs that differ in their color reproduction or in their color spectrum. To achieve a dimming default value for a
  • the lamp is controlled with PWM signals with discrete steps adjustable duty cycle.
  • PWM signals with discrete steps adjustable duty cycle.
  • at least one successive low-frequency PWM packets can be combined for at least one group of lamps, and thus instead of the sequence of low-frequency PWM packets, only one combined low-frequency PWM packet is generated, to which then one or more subsequent low-frequency PWM packets are omitted ,
  • the switch-on time of the switch (S1) may be changed to the next higher or lower adjustable switch-on time after several pulses of adjustable switch-on time and the remaining pulses output with this changed switch-on time, as described with reference to FIGS. 10 and 11 ,
  • the individual groups of lamps can each of one
  • Driver circuit can be controlled, preferably a common control circuit can influence the control of the individual groups of lamps or regulate.
  • a combined low-frequency PWM packet is preferably generated when the pulse width of a low-frequency PWM packet is less than a predetermined minimum portion of the possible pulse width of a low-frequency PWM packet, for example half the maximum possible pulse width of a low-frequency PWM packet.
  • the combined low-frequency PWM packets can be output offset from one another, so that at the same time a omitted low-frequency PWM packet for a lighting group
  • Illuminant group is generated.
  • the position of the combined low-frequency PWM packets may be changed periodically or randomly within the group.
  • the dimming default value can be digital.
  • the pulse repetition frequency can be chosen to be high enough to allow the generation of the combined low-frequency PWM packets
  • the frequency of the PWM pulses can also be selected higher than 200 Hz. In this way, the existing hardware for controlling
  • Lamps are optimally utilized for a color mixture and existing limitations can thus be overcome.
  • the variation of the pulse width does not always have to be in the direction of larger values, but can also be done in the other direction.

Landscapes

  • Circuit Arrangement For Electric Light Sources In General (AREA)

Abstract

L'invention concerne un circuit de commande destiné à au moins une DEL et dans lequel un commutateur (S1) de découpage assure l'alimentation en tension de ladite au moins une DEL. Lorsque le commutateur (S1) est sous tension, une énergie est stockée temporairement dans une bobine (L1) et, lorsque le commutateur (S1) est hors tension, cette énergie est déchargée par l'intermédiaire d'au moins une DEL; et une unité de commande/réglage (SR) commande le commutateur (S1) de telle façon que le courant DEL (iDEL) est réglé à une valeur prédéfinie, et des paquets PWM (modulation d'impulsions en durée) respectivement basse fréquence de largeur réglable sont générés pour le réglage de la luminosité de la DEL. L'invention est caractérisée en ce que, pendant un paquet PWM basse fréquence, la durée de fonctionnement du commutateur (S1) après plusieurs impulsions d'une durée de fonctionnement réglable est modifiée passant à la durée de fonctionnement immédiatement supérieure ou inférieure, et les impulsions restantes sont émises avec cette durée de fonctionnement modifiée, de manière à obtenir un rapport déterminé entre le nombre d'impulsions et les deux durée de fonctionnement réglées, si bien que la DEL est traversée par un courant d'une valeur moyenne qui corresponde à la consigne donnée par une valeur théorique et, en cas de dépassement par le bas d'une valeur de luminosité déterminée et donc d'une largeur déterminée du paquet PWM basse fréquence, différentes impulsions de la durée de fonctionnement réglée sont omises, et ainsi le rapport entre le nombre d'impulsions et les deux durées de fonctionnement réglées s'écarte comparé au fonctionnement pour un courant DEL identique pendant un paquet PWM basse fréquence d'une plus grande largeur.
PCT/AT2012/000289 2011-11-11 2012-11-12 Procédé de fonctionnement d'au moins une del par vibrations WO2013067564A1 (fr)

Priority Applications (2)

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DE112012004722.2T DE112012004722A5 (de) 2011-11-11 2012-11-12 Verfahren zum Betreiben von wenigstens einer LED mittels Dithering
EP12810034.4A EP2777364B1 (fr) 2011-11-11 2012-11-12 Procédé de fonctionnement d'au moins une del par vibrations

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Application Number Priority Date Filing Date Title
AT6192011 2011-11-11
ATGM619/2011 2011-11-11

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9681505B2 (en) 2013-06-06 2017-06-13 Osram Gmbh Circuit arrangement and method for operating and dimming at least one LED
AT16340U1 (de) * 2015-04-22 2019-07-15 Tridonic Gmbh & Co Kg Getakteter Wandler für dimmbare Leuchtmittel mit dynamisch einstellbarem Filter

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DE102006034371A1 (de) 2006-04-21 2007-10-25 Tridonicatco Schweiz Ag Betriebsschaltung für Leuchtdioden
WO2010128845A2 (fr) * 2009-05-04 2010-11-11 Eldolab Holding B.V. Unité de commande pour un ensemble del et un système d'éclairage
US7928712B1 (en) * 2007-06-01 2011-04-19 Rf Micro Devices, Inc. Low noise fast dithering switching power supply
WO2011126374A2 (fr) * 2010-04-09 2011-10-13 Eldolab Holding B.V. Système d'attaque permettant d'attaquer une pluralité de diodes électroluminescentes
WO2011140660A1 (fr) * 2010-05-14 2011-11-17 Lumastream Canada Ulc Procédé et système de commande d'éclairage à semi-conducteurs par tramage

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102006034371A1 (de) 2006-04-21 2007-10-25 Tridonicatco Schweiz Ag Betriebsschaltung für Leuchtdioden
US7928712B1 (en) * 2007-06-01 2011-04-19 Rf Micro Devices, Inc. Low noise fast dithering switching power supply
WO2010128845A2 (fr) * 2009-05-04 2010-11-11 Eldolab Holding B.V. Unité de commande pour un ensemble del et un système d'éclairage
WO2011126374A2 (fr) * 2010-04-09 2011-10-13 Eldolab Holding B.V. Système d'attaque permettant d'attaquer une pluralité de diodes électroluminescentes
WO2011140660A1 (fr) * 2010-05-14 2011-11-17 Lumastream Canada Ulc Procédé et système de commande d'éclairage à semi-conducteurs par tramage

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9681505B2 (en) 2013-06-06 2017-06-13 Osram Gmbh Circuit arrangement and method for operating and dimming at least one LED
AT514354B1 (de) * 2013-06-06 2018-02-15 Osram Gmbh Schaltungsanordnung und Verfahren zum Betreiben und Dimmen mindestens einer LED
AT16340U1 (de) * 2015-04-22 2019-07-15 Tridonic Gmbh & Co Kg Getakteter Wandler für dimmbare Leuchtmittel mit dynamisch einstellbarem Filter

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EP2777364B1 (fr) 2016-03-16
EP2777364A1 (fr) 2014-09-17

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