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    • 专利摘要:
    An operating circuit for at least one light-emitting diode (2) comprises a coil (11), a controllable switching means (13) and a control device (14). The control device (14) is set up to repeatedly switch on the controllable switching means (13) for providing a pulse packet (21, 22) to the at least one light emitting diode (2) during a pulse duration (27) in order to buffer energy in the coil (11) , and turn off to discharge in the coil (11) cached energy via a diode (12) and the at least one light-emitting diode (2). The control device (14) is set up such that a switching frequency (45), with which the controllable switching means (13) is switched on or off, depends on a dimming level at least in one dimming level range (9).
    公开号:AT15798U1
    申请号:TGM9016/2014U
    申请日:2014-04-25
    公开日:2018-07-15
    发明作者:Netzer Harald；Marte Patrick
    申请人:Tridonic Gmbh & Co Kg；
    IPC主号:
    专利说明:

    description
    OPERATING CIRCUIT AND METHOD FOR OPERATING AT LEAST ONE
    LIGHT-EMITTING DIODE DEPENDING ON A DIMMING LEVEL The invention relates to an operating circuit for a lamp. The invention relates in particular to operating circuits for supplying a light-emitting diode (LED) or a plurality of LEDs as a function of a dimming level.
    With the increasing spread of light sources such as LEDs and LED modules, operating circuits for such light sources continue to gain importance. The operating circuit mainly serves to provide a desired energy supply for the illuminant. Additional functions can be provided in the operating circuit, for example to enable the illuminant to be dimmed. The light radiation from LEDs depends on a current flow through the LEDs. For brightness control or brightness control, LEDs are therefore typically operated in a mode in which the current flow through the LED is controlled or regulated by an operating circuit.
    To control an arrangement of one or more LEDs, switching regulators, in particular buck converters, can be used, which are also referred to in the art as step-down converters, buck converters or “step-down” converters. In such an operating circuit, a control device controls a high-frequency, controllable switch. The controllable switch can be, for example, a power transistor. When the switch is switched on, current flows through the LED arrangement and a coil, which is thereby charged with energy. The temporarily stored energy of the coil is discharged via the LEDs when the switch is switched off.
    In order to reduce shifts in the light spectrum at different dimming levels, pulsed operation can be used for LEDs for brightness control or brightness controls. Pulse packets of electricity are supplied to the LEDs by the operating circuit. The LEDs can be dimmed to smaller dimming levels by increasing the time interval between the pulse packets, i.e. reducing the frequency with which pulse packets are generated.
    The output current provided by the operating circuit to the LEDs can have a constant current over time during the pulse duration, the current ripples are superimposed. Such current ripple are caused by the clocked switching of the controllable switching means.
    Even with a predetermined dimming level, situations can occur in which the number of switching cycles of the controllable switching means varies from one pulse packet to the next pulse packet. Another switching cycle of the controllable switching means can be triggered automatically, for example, by the output current of the operating circuit reaching a current threshold value. Depending on whether this current threshold value is shortly before or shortly after the end of the specified pulse duration of the pulse packet, the number of switching cycles per pulse packet can vary. The energy provided to the LEDs for a pulse packet can vary accordingly. This can cause the light to flicker undesirably. Such flickering can be perceived by the human eye and is often perceived as disturbing.
    The invention has for its object to provide devices and methods that reduce the problems described. In particular, the task is to specify devices and methods which reduce light flickering without significantly increasing switching losses at high dimming levels.
    According to the invention, an operating circuit for a lamp and a method are specified with the features specified in the independent claims. The dependent claims define embodiments of the invention.
    / 21
    AT15 798U1 2018-07-15 Austrian
    Patent Office According to embodiments of the invention, at least in a dimming level range,
    e.g. for dimming levels that are smaller than a threshold value, a switching frequency of a controllable switching means of an operating circuit is dynamically adapted to the respective dimming level.
    The current ribs are dynamically adjusted to the respective dimming level.
    An operating circuit for at least one light emitting diode (LED) according to one embodiment comprises a coil, a controllable switching means and a control device. The control device is set up to repeatedly switch on the controllable switching means in order to provide a pulse packet to the at least one LED during a pulse duration in order to temporarily store energy in the coil, and to switch off energy stored in the coil via a diode and via the at least one LED discharged. The control device is set up in such a way that a switching frequency with which the controllable switching means is switched on during the pulse duration or with which the controllable switching means is switched off during the pulse duration depends on a dimming level at least in a dimming level range.
    The control device can be set up to switch the controllable switching means so that the switching frequency in the dimming level range is a monotonically decreasing function of the dimming level.
    The control device can be set up to switch the controllable switching means so that the switching frequency for dimming levels that are less than a threshold value is a strictly monotonically decreasing function of the dimming level.
    The control device can be set up to switch the controllable switching means so that the switching frequency for dimming levels that are smaller than the threshold value is a linearly decreasing function of the dimming level. For dimming levels that are greater than the threshold value, the switching frequency can be a constant function of the dimming level.
    The control device can be set up to switch the controllable switching means such that an amplitude of current ripples occurring in the pulse packet in the dimming level range depends on the dimming level.
    The control device can be set up to switch the controllable switching means so that the amplitude of the current ripple in the dimming level range is a strictly monotonically increasing function of the dimming level.
    The control device can be set up to switch the controllable switching means so that the amplitude of the current ripple in the dimming level range is a linearly increasing function of the dimming level.
    The control device can be set up to switch the controllable switching means so that a maximum current and a minimum current of current ripple in the dimming level range depend on the dimming level.
    The control device can be set up to switch the controllable switching means so that a maximum current of the current ripple is a linearly increasing function of the dimming level.
    The control device can be set up to switch the controllable switching means so that a minimum current of the current ripple is a linearly decreasing function of the dimming level.
    The control device can be set up to switch the controllable switching means so that an average value of a current intensity of the current ripple is independent of the dimming level.
    The control device can achieve a switching frequency and / or amplitude of the current ripple depending on the dimming level in various ways. The control device can compare the output current which is provided to the at least one LED with a switching threshold value and the controllable switching means as a function of the switching threshold value 2/21
    AT15 798U1 2018-07-15 Austrian
    Switch patent office on or off. The control device can determine a period of time until the subsequent switch-off or switch-on depending on the dimming level. The
    The switching threshold value and / or the time duration can be determined, for example, based on a map, calculated by the control device or predefined externally.
    The control device can be configured to switch on the controllable switching means during the pulse duration when a current through the at least one light-emitting diode reaches a first switching threshold value, and to switch it off again after a first period of time, the first switching threshold value and the first period of time of the dimming level depend.
    The control device can be set up to switch off the controllable switching means during the pulse duration when a current through the at least one light-emitting diode reaches a second switching threshold value, and to switch it on again after a second period of time, the second switching threshold value and the second period of time of the dimming level depend.
    The control device can be set up in such a way that in different pulse packets the control device switches the controllable switching means with at least two different switching cycle numbers. Such different switching cycle numbers can also be deliberately caused for different pulse packets with a fixed dimming level, for example in order to implement corrections to the output current averaged over several pulse packets. This enables a fine adjustment of the output current, averaged over several pulse packets, to a target value.
    The control device can be set up such that a switching cycle number of a pulse packet that is generated for a dimming level and a further switching cycle number of another pulse packet that is generated for the same dimming level differ by 1.
    [0026] The control device can be an integrated semiconductor circuit. The control device can be designed as a processor, a microprocessor, a controller, a microcontroller or an application-specific special circuit (ASIC, “Application Specific Integrated Circuit”).
    The control device can comprise an input for receiving the dimming level or a variable influencing the dimming level.
    The operating circuit may include an input for receiving a DC voltage or a rectified AC voltage.
    The operating circuit can comprise a capacitor which is connected in parallel to the at least one LED.
    [0030] The at least one LED can comprise one or more inorganic and / or organic LED (s).
    According to a further exemplary embodiment, a system is provided which comprises the operating circuit and the at least one LED which is connected to the operating circuit.
    According to a further exemplary embodiment, a method for operating at least one LED by means of an operating circuit is specified. The operating circuit comprises a coil and a controllable switching means. The at least one LED is supplied with energy depending on a dimming level. To generate one of the at least one LED supplied pulse packet, the controllable switching means is repeatedly switched on in order to temporarily store energy in the coil and switched off in order to discharge temporarily stored energy in the coil via a diode and via the at least one LED. A switching frequency with which the controllable switching means is switched on during the pulse duration or with which the controllable switching means is switched off during the pulse duration depends on the dimming level at least in a dimming level range.
    3.21
    AT15 798U1 2018-07-15 Austrian Patent Office [0033] For dimming levels in the dimming level range, the switching frequency can be a monotonically decreasing function of the dimming level.
    At least for dimming levels that are smaller than a threshold value, the switching frequency can be a strictly monotonically decreasing function of the dimming level.
    [0035] The switching frequency can be a linearly decreasing function of the dimming level for dimming levels that are smaller than the threshold value. For dimming levels that are greater than the threshold value, the switching frequency can be a constant function of the dimming level.
    [0036] An amplitude of current ripples occurring in the pulse packet can depend on the dimming level in the dimming level range.
    The amplitude of the current ripple in the dimming level range can be a strictly monotonically increasing function of the dimming level.
    [0038] The amplitude of the current ripple in the dimming level range can be a linearly increasing function of the dimming level.
    [0039] A maximum current and a minimum current of current ripple in the dimming level range may depend on the dimming level.
    The maximum current strength of the current ripple can be a linearly increasing function of the dimming level.
    The minimum current strength of the current ripple can be a linearly decreasing function of the dimming level.
    The controllable switching means can be switched so that an average value of a current intensity of the current ripple is independent of the dimming level.
    The output current that is provided to the at least one LED can be compared to a switching threshold value, and the controllable switching means can be switched on or off depending on the switching threshold value comparison. The time until the subsequent switch-off or switch-on can be determined depending on the dimming level. The switching threshold value and / or the period of time can be determined, for example, based on a map, calculated by a control device or predefined externally.
    The controllable switching means can be switched on during the pulse duration when a current through the at least one light-emitting diode reaches a first switching threshold value, and can be switched off again after a first period of time, the first switching threshold value and the first period of time depending on the dimming level.
    The controllable switching means can be switched off during the pulse duration if a current through the at least one light-emitting diode reaches a second switching threshold value, and can be switched on again after a second time period, the second switching threshold value and the second time period depending on the dimming level.
    [0046] Different pulse packets can have at least two different switching cycle numbers. Such different switching cycle numbers can be set in a targeted manner for different pulse packets with a fixed dimming level, in order, for example, to set the output current averaged over several pulse packets to a specific target value. A fine adjustment of the output current averaged over several pulse packets can thus be achieved.
    A number of switching cycles of a pulse packet that is generated for one dimming level and a further number of switching cycles of another pulse packet that is generated for the same dimming level can differ by 1.
    The operating circuit can be supplied with a DC voltage or a rectified AC voltage as the supply voltage.
    The method can automa4 / 21 with the operating circuit according to an embodiment
    AT15 798U1 2018-07-15 Austrian
    Patent office table run.
    According to further embodiments of the invention, an operating circuit for at least one light emitting diode is specified, comprising a coil, a controllable switching means and a control device. The control device is set up to repeatedly switch on the controllable switching means during a pulse duration to provide a pulse packet to the at least one light-emitting diode, to temporarily store energy in the coil, and to switch it off to store energy temporarily stored in the coil via a diode and via the at least one light-emitting diode discharged, the control device being set up to switch off the controllable switching means during the pulse duration when a current through the at least one light-emitting diode reaches a second switching threshold value, the second switching threshold value depending on a dimming level.
    The control device can be set up to switch on the controllable switching means during the pulse duration when a current through the at least one light-emitting diode reaches a first switching threshold value, the first switching threshold value depending on the dimming level.
    Method according to the various embodiments and the effects achieved thereby correspond to the configurations of the operating circuit according to embodiments.
    In devices and methods according to exemplary embodiments, a switching frequency with which the controllable switching means is switched on and / or switched off can be selected as a function of the dimming level. In particular, switching frequencies can be selected for a dimming level range with small dimming levels that are greater than the switching frequency used for larger dimming levels. The higher switching frequency and / or smaller ripple amplitude with small dimming levels can reduce relative fluctuations between the average current strength of pulse packets, even if the pulse packets correspond to a different number of switching cycles. With larger dimming levels, a lower switching frequency can be selected, since due to the overall larger number of switching cycles per pulse packet, relative fluctuations around, for example, one switching cycle would not lead to a clearly perceptible flicker. The lower switching frequency at larger dimming levels keeps switching losses low which are caused by the finite switching time of the controllable switching means.
    The invention is explained below with reference to the figures based on preferred embodiments. In the figures, identical reference symbols designate identical elements.
    Figure 1 [0056] Figure 2 [0057] Figure 3 [0058] Figure 4 [0059] Figure 5 [0060] Figure 6 [0061] Figure 7 shows an operating circuit for light emitting diodes.
    shows pulse packets of an output current of the operating circuit.
    shows an enlarged view of a section of a pulse packet at a first dimming level.
    shows an enlarged view of a portion of a pulse packet at a second dimming level, which is smaller than the first dimming level, to illustrate the mode of operation of devices and methods according to exemplary embodiments.
    shows a control signal for driving a controllable switch.
    shows a dependence of a switching frequency on the dimming level in devices and methods according to an embodiment.
    shows a change in a duty cycle with which pulse packets are generated, depending on the dimming level.
    5.21
    AT15 798U1 2018-07-15 Austrian Patent Office [0062] FIG. 8 [0063] FIG. 9 [0064] FIG. 10 [0065] FIG. 11 [0066] FIG. 12 [0067] FIG. 13 and FIG. 14 shows a dependence of maxima and minima on Current ripple from dimming level in devices and methods according to an embodiment.
    shows a dependence of an amplitude of current ripple on dimming level in devices and methods according to an embodiment.
    is a flowchart of a method according to an embodiment.
    shows an operating circuit for light emitting diodes according to an embodiment.
    shows an operating circuit for light emitting diodes according to an embodiment.
    show sections of pulse packets to explain the operation of exemplary embodiments.
    FIG. 1 shows an illustration of a system which comprises an operating circuit 1 for a lamp 2. The illuminant 2 can comprise a light emitting diode (LED) or a plurality of LEDs. The LEDs can be inorganic or organic LEDs. The multiple LEDs can be connected in series or in parallel. The plurality of LEDs can also be connected in more complex arrangements, for example in several series connections connected in parallel with one another. While three LEDs are shown by way of example, the illuminant can also have only one LED, two LEDs or more than three LEDs.
    The operating circuit 1 is used to operate the at least one LED 2. The operating circuit 1 is supplied with a supply voltage Vbus, which can be a DC voltage or a rectified AC voltage. The output of the operating circuit, which is connected to the at least one LED, is connected to a coil 11 and a controllable switching means 13. If the at least one LED 2 is connected to the operating circuit 1, the controllable switching means 13, the coil 11 and the at least one LED 2 are connected in series. A diode 12 is connected in parallel to the at least one LED 2 and the coil 11. A capacitor 15 can be connected between the output connections, so that the capacitor 15 is connected in parallel with the at least one LED 2. The capacitor 15 is an optional element of the circuit shown and is not required for the basic function, so that the capacitor 15 can be omitted in further exemplary embodiments.
    In the switched-on state of the controllable switching means 13, current flows through the LED (s) 2 and through the coil 11, which is thereby magnetized. When the controllable switching means 13 is switched off, the energy stored in the magnetic field of the coil is discharged in the form of a current via the diode 12 and the LED (s) 2. In parallel, the capacitor 15 can be charged at the start of switching on the controllable switching means 13. During the switch-off phase of the controllable switching means 13 (free-running phase), the capacitor 15 can discharge and contribute to the current flow through the LED (s) 2. With suitable dimensioning of the capacitor 15, this can lead to a smoothing of the current through the LED (s) 2.
    The controllable switching means 13 can be a circuit breaker. The controllable switching means 13 can be a field effect transistor or a bipolar transistor. The controllable switching means 13 can be a transistor with an insulated gate electrode.
    The operating circuit 1 has a control device 14 for clocked switching of the controllable switching means 13. As will be described in detail with reference to FIGS. 2 to 14, the operating circuit 1 can in each case provide an output current in the form of pulse packets in a pulsed operation. The generation of pulse packets need not necessarily take place over the entire operating range of the operating circuit 1. For example, pulse packets can be generated for smaller dimming levels by the average current
    6.21
    AT15 798U1 2018-07-15 Austrian
    Patent office and thus adjust the brightness perceived by the eye. For this purpose, pulse modulation such as pulse width modulation (PWM) can be used, for example, in which a pulse duration of pulse packets and / or a time interval of the pulse packets are set depending on a dimming level.
    As is common in this field of technology, a larger dimming level corresponds to a higher brightness, and a smaller dimming level corresponds to a smaller brightness. The maximum brightness can correspond to a dimming level of 100%.
    [0074] To generate the pulse packet, the control device 14 can repeatedly switch the controllable switching means 13 on and off during a pulse duration. This clocked switching during a pulse packet, in which several switching cycles lie within the pulse duration, should not be confused with the generation of successive pulse packets, which takes place at a lower frequency. As will be described in detail with reference to Figures 2 to 14, the control device 14 controls at least in a dimming level range, e.g. for low dimming levels that are smaller than a threshold value, the controllable switching means 13 such that a switching frequency and / or a ripple current of the pulse packet depends on the dimming level. For example, the switching frequency can increase below the dimming level threshold for decreasing dimming levels. An amplitude of the ripple current can decrease below the dimming level threshold for decreasing dimming levels.
    The control device 14 can be designed as a processor, a microprocessor, a controller, a microcontroller or an application-specific special circuit (ASIC, “Application Specific Integrated Circuit”). The control device 14 can receive a dimming level via an interface, for example from a controller. Alternatively or additionally, the control device 14 can be set up to determine the dimming level as a function of at least one sensor signal. For example, for a brightness control, an actual brightness can be detected with a sensor and a dimming level can be determined depending on a comparison of the actual brightness and the target brightness. As an alternative or in addition, the control device 14 can be set up to determine a dimming level as a function of an actuation of an actuating element, for example a button, rotary knob or switch.
    Figure 2 shows pulse packets 21, 22 of the current, which are provided by the operating circuit 1 at least in one operating mode as an output current and flow through the LED (s) 2. In order to generate the pulse packets 21, 22, the control device 14 controls the controllable switching means 13. The controllable switching means 13 is switched on and off several times in each case in a time window, the duration of which determines a pulse duration 27 of the corresponding pulse packet 21, 22.
    The switching frequency with which the cyclically repeated switch-on processes or the cyclically repeated switch-off processes in the pulses 21, 22 follow one another depends on the dimming level if the dimming level is less than a threshold value.
    Successive pulse packets 21, 22 are separated by a time interval 28 in which the controllable switching means 13 is not switched in a clocked manner. The rising edge of successive pulse packets 21, 22 is separated from one another by a period 29, which defines the slower cyclical repetition of the generation of a pulse packet 21, 22. The ratio of pulse duration 27 to period duration 29 determines the average output current and thus the brightness actually perceived.
    The period 29 is longer than the duration of a switching cycle for the clocked switching of the controllable switching means 13 during the generation of a pulse packet. The period 29 can be much longer than the duration of a switching cycle for the clocked switching of the controllable switching means 13 during the generation of a pulse packet.
    A pulsed operation as shown in FIG. 2 does not have to take place over the entire operating range of the operating circuit 1. For example, a pulsed operation in which pulse packets are generated can only take place for smaller dimming levels. For larger dimmle7 / 21
    AT15 798U1 2018-07-15 Austrian
    Other dimming methods can be used at the Patent Office.
    As schematically shown in FIG. 2, the pulse packets 21, 22 have a ripple current. As will be described in detail with reference to FIGS. 3 to 14, the current ripples in exemplary embodiments of the invention can be changed dynamically depending on a dimming level if the corresponding dimming level is, for example, less than a threshold value or lies in another predefined dimming level range.
    FIG. 3 shows an enlarged illustration of a section of a pulse packet 30 that the operating circuit 1 generates at a first dimming level. FIG. 4 shows an enlarged illustration of a section of a pulse packet 35 that the operating circuit 1 generates at a second dimming level that is smaller than the first dimming level. The output current of the operating circuit 1 is shown, which flows through the LED (s).
    As shown in Figure 3, the controllable switching means 13 can be switched on when the current intensity reaches a first switching threshold value 31 of the current intensity. The controllable switching means 13 can remain switched on for a period of time t on . When the current intensity reaches a second switching threshold value 32, the controllable switching means 13 can be switched off. The controllable switching means 13 can remain switched off for a period of time t off . After a duration T of a switching cycle, the switching processes can be repeated again. This can continue, for example, until the pulse duration 27 of the pulse packet has expired when the first switching threshold value 31 is reached.
    FIG. 4 shows a section of a pulse packet if the dimming level is smaller than for the dimming level of FIG. 3. The scaling of the coordinate axes is chosen the same in Figure 3 and Figure 4. The output current of the operating circuit is shown, which flows through the LED (s).
    In the pulse packet shown in FIG. 4, the controllable switching means 13 can be switched on in each case when the current intensity reaches a further first switching threshold value 36 of the current intensity. This further first switching threshold value 36 is greater than the first switching threshold value 31 in the control for the dimming level of FIG. 3. The controllable switching means 13 can remain switched on for a further time period 38 that is less than the time period t on in the control for the dimming level in FIG 3 is. When the current intensity reaches a further second switching threshold value 37, the controllable switching means 13 can be switched off. This further second switching threshold value 37 is smaller than the second switching threshold value 32 for the dimming level of FIG. 3. The controllable switching means 13 can remain switched off for a further time period 39 which is less than the time period t off in the control for the dimming level of FIG. 3.
    A mean value 33 of the output current, which is formed by averaging over a switching cycle, is equal to the mean value 33 for the output current shown in FIG. 4 for a smaller dimming level in the output current shown in FIG. 3 for a larger dimming level. An amplitude 40 of the current ripple decreases as the dimming level decreases and increases as the dimming level increases.
    As shown in FIG. 3 and FIG. 4, in the case of operating circuits and methods according to exemplary embodiments, the pulse packets can be generated in such a way that a maximum current intensity 32, 37 of the current ripple becomes smaller when the dimming level decreases. In other words, for the dimming level range, e.g. for dimming levels less than a threshold, the maximum current 32, 37 of the current ripple is a monotonically increasing function of the dimming level. The pulse packets can be generated in such a way that a minimum current intensity 31, 36 of the current ripple increases as the dimming level decreases. In other words, for the dimming level range, e.g. for dimming levels smaller than the threshold, the minimum current intensity 31, 36 of the current ripple a monotonically decreasing function of the dimming level.
    The maximum current 32, 37 and / or the minimum current 31, 36 can define switching threshold values at which the control device 14 switches the controllable switching means 13 on or off. If the dimming level is within a certain dimming level 8/21
    AT15 798U1 2018-07-15 Austrian patent office is rich, these switching threshold values can be changed depending on the dimming level so that the amplitude 40 of the current ripple becomes smaller as the dimming level decreases. If the
    Dimming level lies in a certain dimming level range, these switching threshold values can be changed depending on the dimming level in such a way that the average value 33 remains constant as a function of the dimming level.
    The slope of the current edges, which are shown schematically in FIG. 3 and FIG. 4, depend on the specific configuration of the circuit components of the operating circuit 1. A change in the current ripple is accompanied by a change in the switching frequency. The switching frequency with which the controllable switching means 13 is switched on during a pulse packet or with which the controllable switching means 13 is switched off during a pulse packet corresponds to the inverse of the duration T of the switching cycle. If the dimming level is in a certain dimming level range, the switching frequency can increase with decreasing dimming level and decrease with increasing dimming level. The switching frequency can be a decreasing function of the dimming level for dimming levels in the dimming level range.
    FIG. 5 shows a control signal for activating the controllable switching means 13. The pulse packet shown in FIG. 4 is realized with the control signal shown. A control signal with a logic value “1” in FIG. 5 corresponds to an activated controllable switching means 13. In FIG. 5, a control signal with a logic value “0” corresponds to an deactivated controllable switching means 13.
    The controllable switching means 13 is switched on at a first switch-on instant 41. At the first switch-on instant 41, the output current has reached the first switching threshold 36. The controllable switching means 13 is switched off at a first switch-off time 42. At the first switch-off instant 42, the output current has reached the second switching threshold 37. At the second switch-on time 43, the controllable switching means 13 is switched on again. A time interval between the rising edges of the control signal at successive switch-on times 41, 43 and / or a time interval between the falling edges of the control signal at successive switch-off times corresponds to the inverse of the switching frequency.
    The control device 14 can have various configurations in order to implement the change in current ripple and switching frequencies described with reference to FIG. 3 to FIG. 5 as a function of a dimming level and to generate the corresponding control signal for actuating the controllable switching means 13.
    In one configuration, the control device 14 can be set up to recognize when the output current reaches the first switching threshold value 36 and when the output current reaches the second switching threshold value 37. Correspondingly, the control device 14 can switch on the controllable switching means at the switch-on times 41, 43 if the reaching of the first switching threshold value 36 is recognized, and switch it off at the switch-off time 42 if the reaching of the second switching threshold value 37 is recognized. The first switching threshold value and the second switching threshold value can be determined by the control device 14 depending on the dimming level. The control device can determine the first switching threshold value and the second switching threshold value based on a map, for example, arithmetically, e.g. by evaluating functions such as those shown schematically in FIG. 8, or by performing arithmetic processing of map-based variables.
    In a further embodiment, the control device 14 can be set up to recognize when the output current reaches the first switching threshold value 36. The control device 14 can also be set up to determine the first time period 38 for which the controllable switching means is to remain switched on at the corresponding dimming level. Accordingly, the control device 14 can switch on the controllable switching means at the switch-on times 41, 43 if the reaching of the first switching threshold value 36 is recognized. The control device 14 can switch the switch-off time 42 dependent on the switch-on 9/21
    AT15 798U1 2018-07-15 Austrian
    Patent Office
    Determine time 41 and the first time period 38 and switch off controllable switching means 13 at switch-off time 42. The first switching threshold value and the first time period can be determined by the control device 14 depending on the dimming level. The control device can determine the first switching threshold value and the first period of time, for example on the basis of a map, arithmetically determine, e.g. by evaluating functions such as those shown schematically in FIG. 6 and FIG. 8, or by performing arithmetic processing of map-based variables. For example, the first time period can be determined as a known percentage of the inverse of the switching frequency shown in FIG. 6. The first time period can be calculated, for example, by multiplying the inverse of the switching frequency shown in FIG. 6 by a known factor.
    In a further embodiment, the control device 14 can be set up to recognize when the output current reaches the second switching threshold value 37. The control device 14 can also be set up to determine the second time period 39 for which the controllable switching means is to remain switched off at the corresponding dimming level. Correspondingly, the control device 14 can switch off the controllable switching means at the switch-off instant 42 if the reaching of the second switching threshold value 37 is recognized. The control device 14 can determine the switch-on time 43 as a function of the switch-off time 42 and the second time period 39 and switch on the controllable switching means 13 at the switch-on time 43. The second switching threshold value and the second time period can be determined by the control device 14 depending on the dimming level. The control device can determine the second switching threshold value and the second time period, for example on the basis of a map, arithmetically determine, e.g. by evaluating functions such as those shown schematically in FIG. 6 and FIG. 8, or by performing arithmetic processing of map-based variables. For example, the second time period can be determined as a known percentage of the inverse of the switching frequency shown in FIG. 6. The second time period can be calculated, for example, by multiplying the inverse of the switching frequency shown in FIG. 6 by a known factor.
    Figure 6 shows an example of the course of a switching frequency 45 of the controllable switching means depending on the dimming level. A dimming level range 9 comprises low dimming levels, for example dimming levels, which are smaller than a threshold value 8, which is denoted by SW. For dimming levels in dimming level range 9, the switching frequency is a monotonically decreasing function 47 of the dimming level.
    For dimming levels outside dimming level range 9, i.e. for dimming levels that are greater than the threshold value SW, the switching frequency can be a constant function 46, for example. As a result, high switching losses can be avoided in the operating range in which larger currents flow. Other configurations are possible in which the switching frequency also depends on the dimming level for larger dimming levels.
    As shown schematically in FIG. 6, the switching frequency for dimming levels in the dimming level range 9 can be a linearly decreasing function of the dimming level. Other functional dependencies can be used where the switching frequency becomes smaller as the dimming level increases.
    While the switching frequency in FIG. 6 is also shown schematically for dimming levels that are greater than the threshold value SW, another dimming method can also be used outside the dimming level range 9. For example, amplitude dimming can be used.
    The switching frequency with which the controllable switching means is switched during a pulse packet must not be confused with the frequency with which successive pulse packets are generated. The corresponding sizes can in particular also have different functional dependencies on the dimming level. If with T P the pulse duration of a pulse packet, which is shown in FIG. 2 as pulse duration 27, with T NP the time period 28 shown in FIG. 2 as time period 28 between the falling edge of a pulse packet and the rising edge of the subsequent pulse packet and accordingly with T P + T NP the one in figure
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    Patent period referred to as period 29 period, 1 / (T P + T NP ) is the frequency with which pulse packets are generated. As shown schematically in FIG. 7, the product 49 of the pulse duration T P and the frequency with which pulse packets are generated is a monotonically increasing function of the dimming level, even if the dimming level is less than the threshold value SW. This product 49 determines the effective current output, averaged over several pulse packets, and thus the effective brightness.
    Figure 8 illustrates the functional dependency of the maximum current strength 51 of current ripple and the minimum current strength 52 of current ripple in the pulse packets.
    For dimming levels in the dimming level range 9, the maximum current intensity 51 of current ripple is a monotonically increasing function of the dimming level. The maximum current strength 51 of the current ripple can be a linearly increasing function of the dimming level.
    For dimming levels in the dimming level range 9, the minimum current 52 of current ripple is a monotonically decreasing function of the dimming level. The minimum current intensity 52 of the current ripple can be a linearly decreasing function of the dimming level. A slope of the straight line, which indicates the minimum current intensity 52 of the current ripple as a function of the dimming level, can be equal to the negative of the slope of the straight line, which indicates the maximum current intensity 51 of the current ripple as a function of the dimming level.
    [00104] Other functional dependencies of the maximum current 51 and / or the minimum current 52 can be used.
    The maximum current 51 and / or the minimum current 52 of the current ripple as a function of the dimming level, as shown in FIG. 8, can be used to define switching threshold values. This has already been described with reference to FIGS. 3 to 5.
    A dependency of the maximum current 51 and / or the minimum current 52 on the dimming level, as is shown schematically in Figure 8, has the effect that the average current over a switching cycle even when adjusting the switching threshold values, switching frequency and / or amplitude the Stromrippei remains unchanged. This simplifies the control and / or regulating procedures for determining the pulse duration T P or the frequency 1 / (T P + T NP ) with which successive pulse packets are generated.
    Figure 9 illustrates the functional dependence of an amplitude 53 on current ripple in the pulse packets. For dimming levels in the dimming level range 9, the maximum current intensity 51 of current ripple is a monotonically increasing function of the dimming level. For dimming levels that are greater than the threshold value 8, the amplitude of the current ripple can be kept constant. This avoids high switching losses in the operating range in which larger currents flow.
    FIG. 10 is a flowchart of a method 60 according to an exemplary embodiment. The method can be carried out automatically by the operating circuit 1, wherein the control device 14 can carry out the corresponding processing steps.
    At step 61, a dimming level is determined. The dimming level can be received, for example, via an interface of the operating circuit 1, determined depending on a sensor signal or determined depending on an actuation of an input element.
    In step 62 it is checked whether the dimming level is less than a threshold value. If the dimming level is not less than the threshold value, pulse packets can be generated in step 63, for example, the switching frequency of the controllable switching means and the amplitude of the current ripple being independent of the dimming level. Other dimming techniques can also be used.
    [00111] If the dimming level is less than the threshold value, the method continues at step 64. In this case, a switching frequency and / or at least one switching threshold value and / or at least one time period for which the controllable switching means can be switched on or off
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    3 to 5 described.
    At step 65, pulse packets with a switching frequency and / or with current ripple are generated, which depend on the dimming level.
    If the dimming level changes, steps 61-65 can be repeated. If, for example, the dimming level is further reduced starting from a value that is smaller than the threshold value SW, the switching frequency for the controllable switching means 13 can be increased and / or an amplitude of the current ripple can be reduced.
    A dynamic adaptation of the current ripple and / or the switching frequency of pulse packets as a function of a dimming level can be achieved by adapting switching threshold values. The output current can be detected in different ways, as illustrated in FIGS. 11 and 12.
    Figure 11 and Figure 12 show embodiments of operating circuits according to embodiments in which a variable dependent on the output current is detected. This can be compared with at least one switching threshold value, which depends on the dimming level, as was explained with reference to FIGS. 3 to 9. In the operating circuit of FIG. 11, the voltage V LED falling across the LED (s) can be determined via ohmic voltage dividers 16, 17. The difference in the voltages at the voltage dividers 16, 17 results in the voltage V LED dropping via the LED (s) .With knowledge of the characteristic of the LED, the voltage V LE d dropping over the LED (s) can be used to determine the LED 2 flowing current can be closed. Depending on the output voltage of the operating circuit 1 determined in this way, a comparison can be made with corresponding switching threshold values.
    In the operating circuit of Figure 12, the current flowing through the coil or the voltage drop across the coil can be determined via an inductor 18, which is inductively coupled to the coil 11. Depending on the coil current determined in this way or the coil voltage of the operating circuit 1, the current through the LED 2 can thus be inferred and a comparison can be made with corresponding switching threshold values.
    By means of the detection of the voltage drop across the coil 11, the voltage drop across the LED (s) V LED can be concluded. When the controllable switching means 13 is opened and the coil 11 continues to drive the current through the LED during the demagnetization phase, the LED (s) dropping voltage V LED corresponds approximately to the voltage dropping across the coil 11, the difference between the two voltages being the flow voltage of the Is diode 12, this amount can either be taken into account in the detection or can also be neglected in a simple variant. The flow voltage of the diode 12 can be 0.7 V, for example. Knowing the characteristic curve of the LED, the voltage V LED falling across the LED (s) can be used to infer the current flowing through the LED 2.
    As an alternative to monitoring the voltage V LED falling across the LED (s) to determine the first switching threshold value 31, 36 for switching on the controllable switching means 13, a direct measurement of the current through the LED 2 can also be carried out.
    As shown schematically in Figure 11 and Figure 12, the control device 14 may include an input 19 for receiving a signal DL, which indicates the dimming level.
    The dynamic adjustment of the current ripple and / or the switching frequency of pulse packets as a function of a dimming level can be used to reduce a noticeable flickering even if, with a constant dimming level, different pulse packets have a different number of switching cycles of the controllable switching means. For example, a pulse packet can have a number np of switching cycles, and the subsequent pulse packet can have a number np ± 1 of switching cycles. The next pulse packet can again have np switching cycles, for example. Such a “Umschal12 / 21
    AT15 798U1 2018-07-15 Austrian
    Patent offices ten “of the number of switching cycles can occur, for example, if the time at which the
    Output current reaches the lower switching threshold, approximately coincides with the end of the pulse duration. Such a switching of the number of switching cycles can also be introduced consciously and in a controlled manner in order to be able to set the current averaged over several pulse packets more precisely.
    Figure 13 shows one end of a pulse packet. At a point 70, the current intensity reaches the first switching threshold. If the pulse duration of the corresponding pulse packet ends at a time 71 shortly before the current intensity at 70 reaches the first switching threshold value, the controllable switching means is not switched on again. The Stromrippei 73 is the last Stromrippei. The current strength can drop to end the pulse packet. If the pulse duration of the corresponding pulse packet ends at a time 72, shortly after the current intensity at 70 reaches the first switching threshold value, the controllable switching means is switched on again. Another switching cycle 75 follows, which leads to a current ripple 74. Only after the end of the further switching cycle 75 is the controllable switching means not switched on again in order to end the pulse packet.
    The time integral over the current of the pulse packet defines the light energy output by the LED or LEDs. The corresponding time integral differs for the two cases with a different number of switching cycles np and np + 1 by area 76.
    In the case of smaller dimming levels, the time integral of the output current calculated over the pulse packet is smaller than in the case of larger dimming levels. The difference 76 of the time integrals is relatively more important for small dimming levels compared to the integral over the entire pulse package than for larger dimming levels. This can lead to an undesirable, perceptible flicker.
    Figure 14 illustrates the effect of devices and methods according to embodiments. The switching frequency is increased in comparison to FIG. 13 with small dimming levels. The amplitude of the voltage ripple is reduced. The scaling of the coordinate axes is chosen the same in FIG. 13 and FIG. 14.
    If the pulse duration of the corresponding pulse packet ends at a time 71, shortly before the current at 70 reaches the first switching threshold value, the controllable switching means is not switched on again. The Stromrippei 83 is the last Stromrippei. The current strength can drop to end the pulse packet. If the pulse duration of the corresponding pulse packet ends at a time 72, shortly after the current intensity at 70 reaches the first switching threshold value, the controllable switching means is switched on again. Another switching cycle 85 follows, which leads to a current ripple 84. Only after the end of the further switching cycle 85 does the controllable switching means not be switched on again in order to end the pulse packet. The difference of the time integrals differs for the two cases with a different number of switching cycles np and np + 1 by the area 86 which is smaller than the corresponding area 76 in FIG. 13. Flickering can be reduced.
    The increase in the switching frequency in the case of small dimming levels accordingly leads to a shorter duration of the switching cycle. This allows errors in brightness control or brightness control to be reduced even if there is no switching between different number of switching cycles at the same dimming level. For example, the maximum time difference between the end of a switching cycle and the end of the pulse duration is reduced.
    With larger dimming levels, the time integrals of the output current calculated via a pulse packet are overall greater. A lower switching frequency and a larger amplitude of the current ripple can be used without causing strong flickering. Switching losses can be kept lower by dynamically adjusting the switching frequency.
    [00128] While exemplary embodiments have been described with reference to the figures, modifications can be implemented in further exemplary embodiments. Methods and devices according to exemplary embodiments can be used in operating devices for illuminants, for example in an LED converter.
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    权利要求:
    Claims (10)
    [1]
    Expectations
    Operating circuit for at least one light-emitting diode (2), comprising a coil (11), a controllable switching means (13) and a control device (14) which is set up to provide a pulse packet (21, 22) to the at least one light-emitting diode (2) during a pulse duration (27) to repeatedly switch on the controllable switching means (13) in order to temporarily store energy in the coil (11), and to switch it off in order to temporarily store energy stored in the coil (11) via a diode (12) and via the at least one to discharge a light emitting diode (2), the control device (14) being set up in such a way that a switching frequency (45) with which the controllable switching means (13) is switched on during the pulse duration (27) or with which during the pulse duration (27) the controllable switching means (13) is switched off, at least in a dimming level range (9) depends on a dimming level.
    [2]
    2. Operating circuit according to claim 1, wherein the control device (14) is set up to switch the controllable switching means (13) so that the switching frequency (45) in the dimming level range (9) is a monotonically decreasing function (47) of the dimming level.
    [3]
    3. Operating circuit according to claim 1 or claim 2, wherein the control device (14) is set up to switch the controllable switching means (13) such that the switching frequency (45) at least for dimming levels which are less than a threshold value (8), is a strictly monotonically decreasing function (47) of the dimming level.
    [4]
    4. Operating circuit according to one of the preceding claims, wherein the control device (14) is set up to switch the controllable switching means (13) such that an amplitude (40) of current ripples (73, 74) occurring in the pulse packet (21, 22) , 83, 84) in the dimming level area (9) depends on the dimming level.
    [5]
    5. Operating circuit according to one of the preceding claims, wherein the control device (14) is set up to switch the controllable switching means (13) such that a maximum current intensity and a minimum current intensity of current ripple in the dimming level range (9) depend on the dimming level.
    [6]
    6. Operating circuit according to claim 4 or claim 5, wherein the control device (14) is set up to switch the controllable switching means (13) such that an average value (33) of a current intensity during a switching cycle is independent of the dimming level.
    [7]
    7. Operating circuit according to one of the preceding claims, wherein the control device (14) is set up to switch on the controllable switching means (13) during the pulse duration (27) when a current through the at least one light-emitting diode (2) has a first switching threshold value (31; 36) is reached and switched off again after a first time period (38), the first switching threshold value (31; 36) and the first time period (38) depending on the dimming level.
    [8]
    8. Operating circuit according to one of the preceding claims, wherein the control device (14) is set up to switch off the controllable switching means (13) during the pulse duration (27) when a current through the at least one light-emitting diode (2) has a second switching threshold value (32; 37) is reached and switched on again after a second time period (39), the second switching threshold value (32; 37) and the second time period (39) depending on the dimming level.
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    [9]
    9. Operating circuit according to one of the preceding claims, wherein the control device (14) is set up such that in time-sequentially generated pulse packets (21, 22) the control device (14) switches the controllable switching means (13) with at least two different switching cycle numbers.
    [10]
    10. Operating circuit according to claim 9, wherein the control device (14) is set up in such a way that a number of switching cycles of the pulse packet (21, 22) and a further number of switching cycles of a further pulse packet (21, 22) differ by 1.
    6 sheets of drawings
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    1.6
    FIG. 2
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    2/6 t
    FIG. 5
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    3.6
    T P
    FIG. 7
    FIG. 8th
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    4.6
    FIG. 9
    FIG. 10
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    同族专利:
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    法律状态:
    2020-12-15| MM01| Lapse because of not paying annual fees|Effective date: 20200430 |
    优先权:
    申请号 | 申请日 | 专利标题
    DE102013007280|2013-04-26|
    PCT/AT2014/000089|WO2014172731A1|2013-04-26|2014-04-25|Operating circuit and a method for operating at least one lighting diode depending on a dimmer level|
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