AT16163U1 - Lamp control gear - Google Patents

Abstract

The invention relates to an operating device for the dimmable operation of lighting means (1), in particular one or more LED (s), comprising a control circuit having a converter circuit with an energy storage element (4) and at least one switch (2), starting from the control circuit is controlled. In this case, the control circuit is designed to operate by driving the switch (2), the converter circuit optionally at least in critical mode or in the mode with lückendem current operation. In the latching mode, the reclosing time is set in discrete increments in the range of a rising zero crossing of the current through the storage element. In the case of an incremental change in the reconnection time, the control circuit is designed to regulate a parameter influencing the luminous flux by directly or indirectly changing the on-time of the switch (2).

Description

description

LAMP OPERATING DEVICE The present invention relates to a lamp operating device which is designed in particular for the dimmable operation of lamps, such as LEDs. Of course, LEDs also include organic LEDs (OLEDs).

The invention particularly affects the dimmable control gear for lamps that use a clocked converter. A control circuit controls a switch of the clocked converter in such a way that an energy storage element (for example an inductor) is charged when the switch is switched on (conductive), which energy storage element is switched on again when the switch is switched off (non-conductive state of the switch) Illuminant path discharges or charges a capacitor, which in turn feeds the LED path. This ultimately leads to an increasing and decreasing current profile through the lamp path. Since this is typically carried out at a high frequency, the human eye only perceives the temporal average of the illuminant light output thereby generated.

If a relatively high average light output is desired, the drop in current is of course limited, and the switch is switched to conductive again before the current has dropped to zero. However, if, for example, the light output is to be reduced for a dimming, the reclosure threshold (or the corresponding reclosure time) is reduced accordingly (or the reclosure time is extended) until finally the condition is reached that the current actually drops to zero before the Switch is switched conductive again.

[0004] This operating mode is typically referred to as “critical mode” or “borderline mode”.

If, starting from this critical mode (switching on the switch as soon as the current has reached the zero point) is to be further reduced, a dead time must of course be introduced between the drop in the current to zero and the switching on of the switch, which results in the current again caused to rise. This operating mode is called discontinuous mode.

It is, however, advantageous not to perform the reclosing in the gapsing current mode at any point in time, but only if the current that oscillates after the first zero crossing (due to resonance effects) carries out an increasing zero crossing through the inductance. Only when the switch is switched on again in these time ranges with positive zero crossing of the current can a zero-voltage switching of the switch be achieved.

[0007] The time ranges of the positive zero crossings can be recorded by measurement or can be calculated in advance on the basis of the known resonance frequency.

Thus, there arises the problem that in intermittent operation or during the transition from critical mode to intermittent operation, the lamp output can no longer be changed continuously by continuously changing the reclosing time, but only in increments ("valley switching"), which can lead to jumps in the light output, which can also be perceived optically as flickering during a dimming ramp.

The invention now addresses this problem and provides a technique that reduces the problem of jumps in the light output when dimming in the intermittent mode or in the transition from critical mode to intermittent mode.

As a further aspect, the design should be such that an ASIC is not absolutely required as a control device, but that a microcontroller can also trigger the corresponding activation of the switch.

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[0011] This object is achieved by the features of the independent claims. The dependent claims further develop the central idea of the invention in an advantageous manner.

A first aspect of the invention relates to an operating device for the dimmable operation of lamps, in particular one or more LEDs. It points to a control circuit which has a clocked converter circuit with an energy storage element and at least one switch which is clocked starting from the control circuit. The control circuit is designed to operate the converter circuit either at least in the critical mode or in the mode with an intermittent current by driving the switch. In intermittent operation, the control circuit sets the switch-on time of the switch in discrete increments into one of the time ranges after the first zero crossing, in which the current makes an increasing zero crossing when the energy storage element (4) is discharged. The control circuit is designed to regulate a feedback variable influencing the lamp output by an direct or indirect change in the switch-on time of the switch in the event of an incremental change in the switch-on time.

The control circuit can be designed to incrementally increase the switch-on time in the case of an incremental extension of the reclosure time and to carry out a control with the control variable "switch-on time" and, [0015] - incrementally reduce the switch-on time when the switch-on time is incremental to shorten and then carry out a control with the control variable "switch-on time".

The control circuit can be designed to carry out an incremental extension of the reclosing time if the control with the control variable “on time” results in predetermined minimum or maximum values of the on time or a variable influencing this.

The control circuit can be designed to specify the change in the switch-on time of the switch indirectly by specifying a switch-off threshold for the current through the switch or directly by specifying the switch-on time.

The control circuit can be designed to suddenly increase the value for the switch-on period of the switch in a transition from the critical mode to the mode with intermittent current operation.

[0019] The converter circuit can be, for example, a boost, buck or flyback converter.

Another aspect of the invention relates to a method for dimmable operation of lamps, in particular one or more LED (s), using a control circuit which has a converter circuit with an energy storage element and at least one switch which is based on the Control circuit is driven, wherein the converter circuit is operated in the mode with intermittent current. In intermittent operation, the reclosing time is in discrete increments in the range of an increasing zero crossing of the current through the storage element.

To set a dimming value - a predefined switch-off threshold for the current through the switch or a switch-on duration of the switch is set for the dimming value to be set, [0025] - an increasing zero crossing is set as the actual switch-on time, which is the closest to the theoretical switch-on time comes, which results from the switch-off threshold or the switch-on time and the dimming value to be set, and

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Patentamt - the switch-off threshold or the switch-on period depending on the deviation of the actual switch-on time from the theoretical switch-on time, changed.

The predefined switch-off threshold for the current through the switch or a switch-on time of the switch can depend not only on the dimming value to be set, but also on at least one further parameter, such as, for example, the voltage across the lamps.

The invention also relates to a control circuit, for example. ASIC or microcontroller, which is designed for such a method.

Further features, properties and advantages of the invention will now be explained with reference to exemplary embodiments and the accompanying figures of the drawings.

Figure 1 shows a schematic view of a known buck converter for operating an LED path. Figure 2 shows the current and voltage profiles in such a converter of FIG. 1st Fig. 3 shows the use of the so-called Valley Switch in a selected dimming range Figure 4 Fig. 5 shows a block diagram of the embodiment of the invention shows waveforms in the implementation of the invention

In Fig. 1, a known buck converter for operating a lamp 6 is shown schematically.

It is assumed that a DC bus voltage 1, also referred to as V _bus , when a semiconductor switch 2 turns on, an inductor 4 is charged, which discharges when the switch 2 is switched off via a capacitor 5.

Starting from the capacitor 5, an operating voltage V _LED is thus provided for a lamp 6. When the switch 2 is switched on, the voltage V _{LED increases} , while it drops when the switch 2 is switched off. This results in a varying course of the current I _LED through the lamp path 6, the human eye only perceiving the temporal mean value with appropriate high-frequency activation of the switch 2.

The switch 2 is controlled by a control circuit, not shown in FIG. 1, via a signal input 3. The control circuit can be an ASIC or preferably a microcontroller.

Corresponding signal, voltage and current profiles can be seen in FIG. 2.

The signal HS is the level at the control input 3 of the switch 2. During a period T _on , this switch is switched on, while it is not switched _on during the periods t _off and t _dead .

In the period T _off , the diode 7 in Fig. 1 is switched on.

Finally, the lowest curve profile in FIG. 2 is the current profile through the inductance

4. During the switch-on time T _{on of} the switch 2, this current increases, while it drops during the switch-off time t _off until it makes a first (falling) zero crossing. Due to resonance effects, an oscillation course then occurs as in the time period t _dead . According to the invention, this current gap is always switched on again at a time range in which the current through the inductance 4 makes an increasing zero crossing.

The switch-on period T _on can be output by a control circuit either as time-controlled. The switch-on time Ton can, however, also be the result of a hysteresis control, in which the switch 2 is not turned on as soon as the rising one

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Switch _{current has} reached a predetermined upper switch-off value l _peak .

As already mentioned at the beginning, a restart only in discrete increments leads to the positive zero crossing ranges of the current that jumps in the light output can occur in intermittent operation or at the transition from critical mode to intermittent operation mode, since none continuous change of the reclosing time should take place.

If, for example, the illuminant output is to be reduced in the intermittent operation, a higher time for the switch to be switched on again must be jumped. According to the invention, the impending leap in power is now compensated for by maintaining a t _{on time} control with a fixed switch-off time. Ie, if an increment of the positive zero crossings of the LED current I _L ed that deviates from the current state is selected, the control circuit at the same time estimates how the t _on time has to be extended in order to maintain a continuous power reduction (as said, either by a real one time specification or by increasing the switch-off threshold in the case of a hysteresis control), and a t _on-time control is then carried out around this estimated working time.

In contrast to the prior art, the dead time tdead is not recorded in the intermittent operation, but rather is designed adaptively and a t _on- time regulation is maintained.

In terms of control technology, this also has the advantage that a T _On time control is maintained throughout, that is to say both in the intermittent operation and in the critical mode or in the continuous operating mode.

Conversely, if, for example, to carry out a dimming the light output is to be increased again, the dead time tdead is first reduced by a jump in the zero-crossing increments, and at the same time the T _on time is also suddenly reduced to an estimated operating point in order to increase the light output Avoid by continuing the t _{on time} control at this estimated working point.

It is important to emphasize again that the switch-on time t _{on of} the switch 2 can be assigned either directly from a t _on-time control, but also indirectly, namely in particular by specifying a switch-off threshold l _peak for the switch current.

A jump in the dead time increment, that is to say the selected positive zero crossing during the time tdead, can also be triggered when the t _{on time} control or the switch-off threshold control is at an upper or lower predetermined limit value for the tin _on time or the switch-off threshold l _peak .

If, for example, a new average time value for the LED current is to be controlled when a new dimming value is specified, the sequence is as follows:

- After specifying a change, in particular a jump for the setpoint for the mean LED current, the control unit first calculates how long the idle time T _Dea d would have to be in the intermittent operation in order to obtain the mean time current for a given switch-off threshold l To achieve _peak . This calculated dead time t _Dea d will normally not fall on a zero crossing of the current with positive gradients, so that on the one hand the closest zero crossing with positive gradients is selected, but at the same time the difference between the calculated dead time and that determined by the closest zero crossing , On the basis of this known difference, the operating point of the switch-off threshold l _peak or the t _{on time} control can then be set accordingly, after which the t _{on time} control is continued at this operating point.

In order to prevent unnecessary jumping between different zero crossings (“valleys”), which may possibly be visible as a jump in the lamp power, the previous value of the zero crossing is always taken into account when a new average current is specified, in order to jump between two UN4 / 11

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Patent Office [0055] [0056] [0058] [0059] [0060] [0061] [0062] [0063] [0064] to prevent different zero crossings with positive gradients by a kind of hysteresis control.

When a new average value for the current is specified _, a new switch-off threshold lpe _a k is first defined by calculation or by comparison using a table, etc., and then the dead time in intermittent operation is then calculated.

The conversion of an average current value to be set to a switch-off threshold leak can be multidimensional, in such a way that the switch-off threshold lp _e ak (or the direct T _On time specification) is made taking into account further parameters (beyond the average current value to be set). These additional parameters can be, for example:

o The LED voltage, as this affects how sensitively the average value of the current reacts to the change in the switch-off threshold l _Peak .

Another aspect of the invention is that the definition of the switch-off threshold, depending on the dimming value to be achieved (expressed by the average current), determines the frequency of the switch-on processes. In the event of a jump in dimming (that is, a jump in the average value of the current I _LE d), the switch-off threshold is preferably set such that the frequency of the switch-on processes occurs as constant as possible, that is to say the dead time t _De ad is kept constant as far as possible.

In the meantime, it is possible that different specifications are set for the switching frequency to be set for different dimming ranges, so that in different dimming ranges (i.e. different ranges of the current I _L ed) the frequency of the occurrence of the switching operations of the switch 2 to be kept constant can be specified differently ,

In FIG. 3 it can be seen that the “valley switching” according to the invention, that is to say the incremental jumping between different increments at positive zero crossings of the current through the energy storage element (inductance 4), preferably only in an upper dimming range, then at 100% nominal power of the LED path is performed.

With a dimming down of, for example, below 10% dimming level, the dead time in intermittent operation becomes so great that the ringing of the current through the inductor 4 is no longer present or no longer plays a role. This results in a transition zone in which the switch-on time of the switch can be continuously adjusted below the dimming range for the valley switching.

This continuous increase in dead time in intermittent operation, however, comes up against limits when the dimming level is further reduced, for example below 1% nominal power, since a very long dead time can possibly lead to optically visible effects. A maximum dead time T _{deadmax is therefore} provided. If this is achieved, the dead time is recorded and a further reduction in the light output can then, for example, only be achieved by other effects, such as, for example, reduction.

4 shows a schematic block diagram for carrying out the invention.

A block A denotes a calculation block for calculating the nominal dead time T _deadnom and the nominal switch-off _threshold l _peak nom

For this calculation, the specified setpoint l _nO m for the LED current, the DC supply voltage for the converter V _bus and the lamp voltage V _{LED are} taken into account.

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From these input values, block A in FIG. 4 _uses a function or a comparison _{table to calculate} the nominal values for the dead time Td _eadn om and the switch-off _threshold l _peak nom (or the switch-on time period T _onn om). [0066] Block B then serves to implement the dead time control based on these calculated nominal values.

In a first block "select nearest neighbor" that "valley" (ie the positive zero crossing) is selected that comes closest to the nominal dead time T _deadnom .

In this block B, the temporal position of the “valleys” is stored in advance, which is designated “valley array” in FIG. 4.

The "valley" that the T _deadnom comes closest is taken as the "valley" to be set and the dead time is set accordingly with the value "due T _dead ".

Note: All calculations in block A are outside the actual control loop and are therefore not time-critical. They can therefore be easily managed by a microcontroller.

In addition, block A also calculates the temporal average value I _AV g. In block B, the actual current control “current regulator” is provided, which contains the setpoint value l _nom and the currently measured actual value for the LED current l _MEAS is fed.

Furthermore, a dead time compensation unit is provided “T _deadcom pensator”, which receives the selected valley from the “select nearest neighbor” block as well as the mean time value of the current through the LED path I _AV g as input information.

In order now to prevent the deviation and thus a jump in the lamp power, which arises due to the deviation of the _valley from the calculated _{nominal dead time} T _deadnom , the output variable of the current control “current regulator” is used by the dead time compensator “T _deadC0 mpensator” Shift of the working point changed, so that this results in a new switch-off threshold for the switch current "new l _peak ".

These sequences are to be shown again using the signal curves from FIG. 5.

In this case, the scenario is assumed that a current is received in the setpoint specification I _nom for the time average of the current at a point in time T1. After such a setpoint jump has been received, a calculation phase follows which is required to carry out the calculation which is shown in FIG. 4.

As can be seen in FIG. 5, the calculation of the nominal dead time T _deadnom necessary for the setting of the new setpoint value 1 _{nom takes place} . In fact, however, the closest valley “nearest neighbor” is set at the nominal dead time T _deadnom .

This deviation of the nominal dead time T _deadnom from the temporal position of the next _valley results in a compensation value E _PK comp, which is used by the block “T _{dead com} pensa _to r” in FIG. 4 directly to change the operating point of the current control becomes. This abrupt adjustment of the working point actually prevents the jumps in the light output, since on the other hand the current controller would also correct this control error (deviation of the actual dead time from the nominal dead time), but the duration of the adjustment could lead to optically visible effects.

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Claims (11)

Expectations 1. operating device for dimmable operation of lamps (1), in particular one or more LEDs (s), comprising a control circuit which has a clocked converter circuit with an energy storage element (4) and at least one switch (2) which is clocked starting from the control circuit, the control circuit is designed to operate the converter circuit by actuating the switch either at least in the critical mode or in the mode with an intermittent current, - The control circuit in intermittent operation sets the switch-on time of the switch (2) in discrete increments in one of the time ranges after the first zero crossing, in which the current through the energy storage element (4) makes an increasing zero crossing, characterized in that the control circuit for this is designed, in the event of an incremental change in the reclosing time, to regulate a feedback variable influencing the lamp output by directly or indirectly changing the on-time of the switch (2). 2. Operating device according to claim 1, wherein the control circuit is designed to - In the case of an incremental extension of the switch-on time, incrementally extend the switch-on time and carry out regulation with the control variable "switch-on time" and, - In the case of an incremental reduction in the restart time, incrementally shorten the switch-on time and then carry out a control with the control variable "switch-on time". 3. Operating device according to one of the preceding claims, in which the control circuit is designed to carry out an incremental extension of the reclosing time when the control with the control variable “on time” results in predetermined minimum or maximum values of the on time or a variable influencing this. 4. Operating device according to one of the preceding claims, wherein the control device is designed to specify the change in the switch-on time of the switch (2) indirectly by specifying a switch-off threshold for the current through the switch (2) or directly by specifying the switch-on time. 5. Operating device according to one of the preceding claims, in which the control circuit is designed to suddenly increase the value for the switch-on time of the switch in a transition from the critical mode to the mode with intermittent current operation. 6. Operating device according to one of the preceding claims, wherein the converter circuit is a boost, buck or flyback converter. 7. Method for dimmable operation of lamps, in particular one or more LED (s), using a control circuit which has a converter circuit with an energy storage element and at least one switch which is controlled on the basis of the control circuit, the converter circuit in the mode with a gap Current is operated, in the intermittent operation the reclosing time lies in discrete increments in the range of a rising zero crossing of the current through the storage element, characterized in that 7/11 AT 16 163 U1 2019-03-15 Austrian Patent office that for setting a dimming value - a switch-off threshold for the current through the switch or a switch-on period of the switch is predefined for the dimming value to be set, an increasing zero crossing is set as the actual reclosing time, which comes closest to the theoretical reclosing time which results from the shutdown threshold or the on time and the dimming value to be set, and - The switch-off threshold or the switch-on time is changed depending on the deviation of the actual switch-on time from the theoretical switch-on time. 8. The method according to claim 7, wherein the predefined switch-off threshold for the current through the switch or a switch-on period of the switch depends not only on the dimming value to be set, but on at least one further parameter, such as, for example, the voltage across the lamps. 9. Control circuit, for example ASIC or preferably microcontroller, which is designed for a method according to one of the claims. With 3 sheets of drawings 8/11 AT 16 163 U1 2019-03-15 Austrian Patent Office 1/3 lAVG ^ peak ^ tton + toffyCton + W’tclead) __, / g. <29.11 AT 16 163 U1 2019-03-15 Austrian Patent Office 10/11 AT 16 163 U1 2019-03-15 Austrian Patent Office 3/3 i 11/11