FI128227B - Method and arrangement for flexible dimming control of lighting drivers - Google Patents

Abstract

A driver device (501, 1201) for light sources (503) comprises an operating voltage input (502), a lighting power output (504), a power converter (505) between said operating voltage input (502) and said lighting power output (504), and a control input (506), separate from said operating voltage input (502). A controller part (612, 613) is coupled to said control input (506) and to said power converter (505), and configured to control, on the basis of received control signals, an amount of said electric power. Said control input (506) is configured to receive phase-cut AC half-waves at an electric power distribution network voltage as said control signals. Said controller part (612, 613) is configured to detect a timing of said received phase-cut AC half-waves and to control said amount of electric power provided by said power converter (505) on the basis of said detected timing.

Description

METHOD AND ARRANGEMENT FOR FLEXIBLE DIMMING CONTROL OF

LIGHTING DRIVERS

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FIELD OF THE INVENTION

The invention concerns the technical field of controllable driver devices for light sources. In particular the invention concerns the controlling of characteristics of light, such as intensity, colour, 10 and/or colour temperature, in a flexible and easily adaptable manner.

BACKGROUND OF THE INVENTION

Fig. 1 illustrates a known arrangement for 15 controlling a driver device for light sources. In this example the driver device 101 is a LED driver, which comprises an operating voltage input 102 configured to receive an operating voltage, such as the 230 volts of AC used in European and many other electric power dis20 tribution networks. The light sources, which here are

LEDs 103, are connected to a lighting power output 104 of the driver device 101. The driver device comprises a power converter 105 between the operating voltage input 102 and the lighting power output 104. The power 25 converter may comprise components like filters, rectifiers, and one or more converter stages, and it is configured to provide the desired electric power to the light sources in controllable amounts.

In addition to the operating voltage input 30 102 the driver device 101 comprises a control input

106, which is configured to receive control signals. A controller part 107 within the driver device 101 is coupled to the control input 106 on one hand and to the power converter 105 on the other hand. The con35 troller part 107 is configured to control, on the basis of received control signals, the amount of elec

20185551 prh 19 -06- 2018 trie power that the power converter 105 provides to the light sources. Operating power for the controller part 107 comes from the operating voltage input 102 through the power converter 105.

The upper part of fig. 1 illustrates how the control signals to the control input 106 come from an external controller, which in the case of fig. 1 is a DALI controller 108. DALI is an acronym for Digital Addressable Lighting Interface, which is an example of 10 a standardized lighting control bus 109. A DALI power supply 110 provides the lighting control bus 109 with operating power. The control signals take the form of digitally formatted control words. For example in the DALI system the DALI power supply 110 provides a de15 fault DC voltage of 22 volts maximum between the two wires of the DALI bus. Each device that makes transmissions on the DALI bus is capable of controllably shorting the bus. Manchester coding is used, so that transitions between a low bus voltage (less than 4.5 20 volts) and a high bus voltage (9.5 volts or more) are taken to mean the digital values 0 or 1 as defined in the DALI standard.

Fig. 2 illustrates another example of a controllable driving device 201 for light sources. The 25 operating voltage input 102, the lighting power output 104, and the power converter 105 may be similar to the correspondingly numbered parts in fig. 1. The control input 206 and the controller part 206 are configured to be selectively coupled to the voltage of the elec30 trie power distribution network. The coupling goes through a switch 210, which is typically a push button that is normally open but closes when the user presses it. This way in fig. 2 the control signals are of analogue nature and consist of periods during which the 35 network AC voltage appears at the control input 206.

The controller part 206 is configured to detect these periods and to act accordingly, for example so that

20185551 prh 19 -06- 2018 short presses (less than a first predefined limit) of the switch 210 cause the lights to be switched on or off, and keeping the switch 210 pressed for longer than a second predefined limit leads to dimming or 5 brightening the light.

Some known prior art devices combine these approaches, which is illustrated in fig. 3. The driver device 301 is equipped with a control input 306 that is capable of withstanding the network AC voltage 10 (which is typically at least an order of magnitude higher than the voltages encountered on digital control buses) in case switched control was used, but the controller part 307 is also capable of interpreting digital command words. Thus the wires 311 coupled to 15 the control input 306 may come from the electric power distribution network through a switch 210 or from a lighting control bus 109. An example of a driver device of this kind is found in the patent publication DE 197 57 295 B4.

Attempts have also been made to use phasecutting thyristor or triac dimmers to control driver devices of light sources, like in fig. 4. Phase-cut dimmers 410 were originally used to dim incandescent bulbs, which was straightforward because cutting a 25 portion out of each half-wave of the network AC voltage simply reduces the mean AC power. An incandescent bulb converts AC power directly into light (and heat), so phase-cut dimming was all that was needed. An example of a driver device of this kind is found in the 30 patent publication number EP 1 502 483 Bl.

All prior art approaches to dimming have their advantages but also their drawbacks. Using a separate lighting control bus like in fig. 1 requires installing additional wires for the control bus sig35 nais. Many users are not used to switched control like in fig. 2 and consider is inaccurate and unreliable. Phase-cut dimming like in fig. 4 involves for example the disadvantage that on very low dimming levels also very little operating power is available for the controlling part 407, because this operating power comes

	from the operating voltage input 102	at which only a
5	very small	portion of	each half-wave	is available	on
	low dimming	levels .
	SUMMARY
	An	obj ective	of the present	invention is	to
10	provide a	method and	an arrangement	with which	the
	dimming of	light sources that necessitate a driver	de-

20185551 prh 19 -06- 2018 vice can be made in a flexible, yet straightforward way. Another objective of the invention is that the same driver device could be used for different kinds 15 of dimming approaches. Yet another objective of the invention is that the manufacturing costs of a driver device would not come prohibitively high despite its flexibility regarding dimming.

The objectives of the invention are achieved 20 by allowing a phase-cut dimmer to be coupled between an electric power distribution network and the separate control input of a driver device, while maintaining a coupling without the dimmer from the electric power distribution network to the operating voltage 25 input of the driver device.

A driver device according to the invention is characterized by the features recited in the independent claim directed to a driver device.

A method according to the invention is char30 acterized by the features recited in the independent claim directed to a method.

Advantageous embodiments of the invention are considered in the depending claims.

The exemplary embodiments of the invention 35 presented in this patent application are not to be interpreted to pose limitations to the applicability of the appended claims. The verb to comprise is used in this patent application as an open limitation that does not exclude the existence of also features that are not explicitly recited. The features recited in depending claims are mutually freely combinable unless 5 otherwise explicitly stated.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of 10 operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:

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	Figure	1	illustrates	a	prior	art	driver	de-
	vice,	Figure	2	illustrates	a	prior	art	driver	de-
25	vice,	Figure	3	illustrates	a	prior	art	driver	de-
	vice,	Figure	4	illustrates	a	prior	art	driver	de-
	vice,
30		Figure	5	illustrates	an	arrangement according
	to an	embodiment	r
		Figure	6	illustrates	a	driver	device accord-

ing to an embodiment,

Figure 7 illustrates a timing of phase-cut AC half-waves,

Figure 8 illustrates a sequence of receiving and not receiving AC half-waves,

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Figure 9 illustrates an arrangement according to an embodiment,

Figure 10 illustrates an interface circuit and a processor,

Figure 11 illustrates an example of an interface circuit, and

Figure 12 illustrates an arrangement according to an embodiment.

DETAILED DESCRIPTION

Fig. 5 illustrates an arrangement in which a driver device 501 for light sources comprises an operating voltage input 502 and a control input 506 separate from the operating voltage input 502. The control 15 input 506 is configured to receive control signals of predefined kind, which means that electrically the control input 506 is designed to withstand the voltages and currents that are known to occur in said control signals of predefined kind. As shown in fig. 5, 20 there are multiple possibilities for control signals:

digital control signals conveyed through a digital control bus 109; switched control signals coming from a control switch 210, or phase-cut AC half-waves coming from for example a thyristor or triac dimmer 410.

Of these the last-mentioned alternative is explained in the following first in more detail.

As shown in fig. 6, the operating voltage input 502 of the driver device 501 is configured to receive an operating voltage. Here the widely used acro30 nyms L, N, and PE designate the live, neutral, and protective earth lines respectively of an electric power distribution network. The operating voltage may be for example 230 volts AC or any other voltage that is used in the electric power distribution network.

The driver device 501 comprises a lighting power output 504 configured to provide electric power for light sources 503. In this example the light

20185551 prh 19 -06- 2018 sources 503 are LEDs, so the driver device 501 may be called a LED driver. In an alternative embodiment the light sources could comprise for example one or more fluorescent tubes, in which case the driver device 501 5 could be called an electronic ballast.

The driver device 501 comprises a power converter 505 between the operating voltage input 502 and the lighting power output 504 . The power converter 505 may comprise for example filters, rectifiers, and one 10 or more converter stages. In a LED driver or an electronic ballast a power converter of this kind may comprise for example an EMC filter, a rectifier, a PEC (power factor correction) converter stage, a bus voltage converter stage, and an output converter stage. It 15 is possible to use fewer converter stages, particularly if galvanic isolation is not needed between the input and output sides of the driver device. It is also possible to use even more converter stages.

The power converter 505 is configured to pro20 vide the output electric power of the driver device 501 in controllable amounts. To this end it may be equipped for example for pulse width modulation control, in which output current of a certain nominal value is provided in pulses with a controllable duty 25 cycle. Alternatively it may be equipped for analog output current control, in which the output current is continuous but its absolute value can be varied between zero and a maximum value. Yet another possibility, applicable particularly in electronic ballasts, 30 is that an output stage of the power converter 505 has a controllable output frequency, so that at or close to a particular resonance frequency the driver device delivers a relatively high power to the light source(s), and at frequencies farther away from said 35 resonance frequency the driver device delivers a relatively low power to the light source(s).

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The control input 506 of the driver device

501, which is separate from the operating voltage input 502, is coupled to a controller part. In this example the controller part comprises a controller 612 and an interface circuit 613 between the control input 506 and said controller 612. The controller part is configured to control, on the basis of received control signals, an amount of the electric power that the power converter 505 provides to the light source(s).

Control connections are illustrated with black arrows in fig. 6, and power flows are illustrated with white arrows. As an example, the interface circuit 613 is shown to receive its operating power either from the power converter 505 or through the control input 506, or partly from both.

Compared to the prior art arrangement of fig.

4, there is the important difference that the control input 506 is separate from the operating voltage input

502, so the phase-cut AC half-waves may be received at the control input 506 independently of what is received at the operating voltage input 502. In the advantageous embodiment shown in fig. 5 the AC halfwaves may go as such, without any phase-cutting, into the operating voltage input 502. Basically the operat25 ing voltage that is received at the operating voltage input 502 could be even some completely other voltage than the AC from which those phase-cut AC half-waves were produced that are received at the control input 506.

The controller part is configured to detect a timing of the received phase-cut AC half-waves and to control the amount of electric power provided by the power converter 505 on the basis of the detected timing. There are two aspects of detecting the timing of the received phase-cut AC half-waves. These are described in the following with reference to figs. 7 and .

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Fig. 7 illustrates an example of phase-cut AC half-waves. Without any phase-cutting the AC halfwaves would follow each other continuously at alternating polarities, essentially constituting a sine 5 wave. Phase-cutting means that a portion is cut away from each half-wave. In fig. 7 phase-cutting of the trailing edge type is performed, which means that the cut portion is at the end of each half-wave. The alternative would be phase-cutting of the leading edge 10 type, in which the cut portion is at the beginning of each half-wave. Whether the phase-cutting is of leading edge or trailing edge type has no significance to the present considerations.

The duration of a complete half-wave is shown 15 as 701 in fig. 7. Reference designator 702 shows the duration of the uncut portion of the half-wave, while reference designator 703 shows the duration of the cut portion. When phase-cutting was originally used to dim incandescent lights, the brightness of the emitted 20 light was determined by the power that is represented by the uncut portion 702 in relation to the full power represented by a full half-wave. Thus, when the controller 612 determines the electric power that the power converter 505 should provide for the light 25 sources 503, this same relation can be used. Knowing the form of the sine wave, the power can be calculated from the duration of the uncut portion 702 in relation to the duration of a full half-wave. The power is essentially equal to the area between the voltage graph 30 and the horizontal axis.

The use of a relative duration of the uncut portion 702 involves the advantage that the freguency of the AC half-waves, i.e. the absolute duration 701 of one half-wave, does not affect the result. Whether 35 the relative duration 702 over 703 or the relative duration 702 over (702+703) is used is just a design choice, which can be accommodated in the programming

20185551 prh 19 -06- 2018 of the controller 612; the former relation will range essentially between zero and infinity, while the latter relation will range essentially between zero and 100% .

According to the first aspect, a controller part is configured to detect a timing like that of fig. 7 of received phase-cut AC half-waves and to control accordingly the amount of electric power provided by the power converter. This aspect may be character10 ized so that the controller part is configured to detect an extent of phase-cutting done on the received phase-cut AC half-waves and to control said amount of electric power provided by the power converter on the basis of the detected extent of phase-cutting.

Fig. 8 illustrates another aspect of the timing of received phase-cut AC half-waves. Here the controller part is configured to detect sequences of receiving and not receiving phase-cut AC half-waves. For the duration 801 no phase-cut AC half-waves are re20 ceived at all, while for the duration 802 they are received as usual.

Sequences like this can be used for example to convey commands to the controller 612. For example, the controller 612 may be configured to select among 25 various controlling modes in response to receiving a particular sequence. Controlling modes may comprise at least a dimming mode and a colour changing mode. A dimming mode is a mode in which the controller part is configured to control an overall amount of electric 30 power provided by the power converter on the basis of the detected timing of the phase-cut AC half-waves. The overall amount of electric power corresponds straightforwardly with the overall intensity of light emitted by the light sources, hence the name dimming 35 mode. A colour changing mode is a mode in which the controller part is configured to control relative amounts of electric power directed to at least two

20185551 prh 19 -06- 2018 separate outputs of the driver device on the basis of said detected timing. If light sources of different colour (or colour temperature) are coupled to such two separate outputs, changes in the relative amounts of 5 electric power result in changes of the overall colour (or colour temperature) of the emitted light.

Not all driver devices are capable of changing the colour of light sources, for example because they only have a single output so that only light 10 sources of one kind can be coupled thereto. There may also be cases in which the colour of light sources does not need to be changed, even if it was basically possible. In these and possible other cases the controller 612 may be configured to select among other 15 alternative ways of operating in response to receiving a particular sequence. As an example, if the controller 612 notices that the received phase-cut AC halfwaves disappear, i.e. there occurs what is seen as the beginning of the duration 801 in fig. 8, it may set 20 the electric power provided by the power converter 505 to zero or to some other minimum value, or to full or some other maximum value. The way in which the controller 612 reacts to any change in the received phase-cut AC half-waves can be defined during a step 25 of configuring the driver device 501 for use.

Fig. 9 illustrates an example of an arrangement with which the timing aspects of both figs. 7 and 8 can be realized. In addition to the dimmer 410, there is also a switch 901 on the current path between 30 the source of the AC half-waves and the control input 506 of the driver device 501. In this example the switch 901 is between the phase-cutting dimmer 410 and the control input 506, but the same effect could be realized also by placing the switch 901 between the AC 35 voltage delivery line and the dimmer 410.

Many conventional, phase-cutting thyristor or triac dimmers include a switch suitable for use as the

20185551 prh 19 -06- 2018 switch 901. For example many turn-knob dimmers include an additional push-knob functionality, so that turning the knob changes the phase-cutting angle and pressing the same knob activates the switch. This switch can be 5 used as the switch 901. Also a switch from the dimmer

410 can be used. Fig. 9 illustrates also a switch 902 in the AC voltage delivery line that goes to the operating voltage input 502 of the driver device 501. Such a switch can be used as an on/off switch. If a switch 10 901 is not needed on the current path that goes to the control input 506, and if the turn-knob/push-knob dimmer can be wired accordingly, an embodiment can be provided in which the push-knob switch is an on/off switch in the AC voltage delivery line as switch 902 15 in fig. 9, and the turn-knob dimmer operates otherwise as dimmer 410 in fig. 9.

Figs. 10 and 11 show an example of how an interface circuit 613 can be used between a control input 506 and a controller 612. The controller 612 is 20 designated a processor in fig. 10, but it can be any suitable programmable controlling entity such as a microcontroller or microprocessor equipped with proper memory and other auxiliary circuits. The interface circuit 613 comprises at least a reception branch 25 1001, and it may comprise a transmission branch 1002 if the control input is to act also as a control output in case the driver device will be coupled to a bidirectional lighting control bus.

The interface circuit 613 (and in particular 30 its reception branch 1001) may have several tasks, one of which may be to implement galvanic isolation and other safety aspects. The interface circuit 613 may also be provided for converting information encoded into the timing of received phase-cut AC half-waves 35 into input signals suitable to a processor that acts as the controller 612 in the block diagram representation of fig. 6. These input signals may be for example

20185551 prh 19 -06- 2018 just logical ones or zeroes. In other words, the interface circuit 613 may comprise a comparator or a large-gain amplifier that acts essentially as a onebit A/D converter. It is configured to provide as in5 put signals to said processor a first logical value when a voltage between a received phase-cut AC halfwave and a neutral value is larger than a predetermined threshold, and a second logical value when said voltage between said received phase-cut AC half-wave 10 and said neutral value is smaller than said predetermined threshold.

In such a case it remains the responsibility of the processor to detect the relative time durations. The processor may be configured to detect a 15 relative duration of receiving said first logical value as an input signal in comparison to a duration of receiving said second logical value as an input signal, and to control said amount of electric power provided by said power converter in proportion to said 20 relative duration.

As an alternative, the interface circuit 613 may comprise an analog to digital converter that is configured to provide, as input signals to the processor 612, sampled digital representations of the re25 ceived phase-cut AC half-waves in more bits than one.

In such a case the processor may be configured to detect from said digital representations a relative duration of uncut portions of said phase-cut AC halfwaves in comparison to a duration of cut portions of 30 said phase-cut AC half-waves. The processor may be configured to control said amount of electric power provided by said power converter in proportion to said relative duration.

Fig. 11 illustrates a principle of an inter35 face circuit that can be used according to any of the approaches explained above, if the component values are selected appropriately. The two nodes 1101 on the

20185551 prh 19 -06- 2018 left constitute the control input, the upper part of the circuit constitutes the reception branch 1001, and the lower part of the circuit constitutes the transmission branch 1002. The optoisolators 1102 and 1103 5 implement galvanic isolation. The zener diode 1104 sets a predetermined threshold, above which the voltage at the control input must be before it is taken to differ from zero. If the resistance of the ballast resistor 1105 is relatively small, the LED in optoisola10 tor 1102 will shine at full brightness whenever the voltage at the control input is above the threshold, and essentially just two logical values can appear at the input signal RX to the processor. If the resistance of the ballast resistor 1105 is relatively 15 large, the value at the input signal RX to the processor will depend on the voltage at the control input, so it can be taken through an additional A/D converter (not shown) to produce sampled digital representations of received phase-cut AC half-waves in more bits than 2 0 one.

Fig. 12 illustrates an arrangement in which a driver device 1201 comprises an operating voltage input 502 and a control input 506, of which the latter is separate from the operating voltage input 502 and 25 configured to receive phase-cut AC half-waves at an electric power distribution network voltage as control signals. Such phase-cut AC half-waves come from a dimmer 410 through a switch 901 that is normally closed but opens when the user presses a button, or pushes 30 for example the knob in the dimmer 410 the turning of which changes the phase-cutting angle. The driver device 1201 comprises two parallel lighting power outputs, one for LEDs 1202 of a first colour or colour temperature, and another for LEDs 1203 of second col35 our or colour temperature. A controller part (not separaterly shown in fig. 12) in the driver device 1201 is configured to select among at least a dimming mode

20185551 prh 19 -06- 2018 and a colour changing mode as a response to a detected sequence of receiving and not receiving phase-cut AC half-waves at the control input 506. The user may compose such sequences by pressing the button or knob 5 that opens the switch 901. At its simplest each press of the button or knob is interpreted as a command to change from the current mode (dimming or colour changing) to the other. The duration of time when no phasecut AC half-waves are received must be longer than one 10 cut-out portion of a half-wave in order to be interpreted properly in the controller part, but this is typically not a problem because a human user will most probably press a button or knob long enough anyway, taken the relatively short duration of a half-wave in 15 the AC voltage.

Referring back to fig. 5, it is advantageous to manufacture the driver device 501 (or the driver device 1201 of fig. 12) so that it can correctly obey the control commands independent of which external 20 controller (DALI controller 108, control switch 210, or phase-cutting dimmer 410) is actually transmitting the control commands to the control input 506. Automatic recognition is possible, so that the controller part (not separately shown in fig. 5) of the driver 25 device 501 is configured to examine features of signals received at the control input 506, and to detect, on the basis of said examining, which protocol among a number of predetermined protocols the received signals adhere to. The examining and detecting of this kind 30 can be done for example by comparing voltage profiles of the received signals to a database of voltage profiles of the control signals belonging to known protocols .

It is also possible to make the driver device 35 501 (or 1201) externally configurable, so that a configurator device and/or configurator software are used to tell it which communications protocol it should use in interpreting received control commands. Configuring a driver device of lighting sources is a known technology as such, and does not need to be explained here in more detail. One advantageous feature that may be 5 used is reconfigurability. It may require that even if a driver device has been configured to receive and appropriately interpret phase-cut AC voltage half-waves (or control switch commands, originating from the switch 210 of fig. 5) as control commands, it will 10 simultaneously maintain readiness of correctly recognizing a start reconfiguring command at the control input, even if such a command would take some other form than just some phase-cut AC voltage half-waves.

It is obvious to a person skilled in the art 15 that with the advancement of technology, the basic idea of the invention may be implemented in various ways. For example, it is not necessary to follow the legacy principle, according to which a decreasing relative duration of the uncut portion of the half-wave 20 should always mean a command to dim down the lights.

For example, an opposite control strategy could be adopted in which the more power is provided at the output of the driver device the shorter is the relative duration of the uncut portion. The invention and 25 its embodiments are thus not limited to the examples described above, instead they may vary within the scope of the claims.

Claims (14)

1. Driver device (501, 1201) for light sources (503), comprising:

- an operating voltage input (502) configured to re-

5 ceive an operating voltage,

- a lighting power output (504) configured to provide electric power for said light sources (503),

- a power converter (505) between said operating voltage input (502) and said lighting power output (504),

10 configured to provide said electric power in controllable amounts,

- a control input (506), separate from said operating voltage input (502), configured to receive control signals, and

15 - a controller part (612, 613) coupled to said control input (506) and to said power converter (505), and configured to control, on the basis of received control signals, an amount of said electric power provided by said power converter (505);

20 characterized in that

- said control input (506) is configured to receive phase-cut AC half-waves at an electric power distribution network voltage as said control signals, and

- said controller part (612, 613) is configured to de-

25 teet a timing of said received phase-cut AC half-waves and to control said amount of electric power provided by said power converter (505) on the basis of said detected timing, wherein said controller part comprises:

- a processor (612) and

30 - an interface circuit (613) between said control input (506) and said processor (612) for converting information encoded into said timing of said received phase-cut AC half-waves into input signals to said processor ( 612) .

35

2. A driver device (501, 1201) according to claim 1, wherein said interface circuit (613) compris18

20185551 prh 06 -06- 2019 es a comparator or a large-gain amplifier configured to provide as input signals to said processor (612) a first logical value when a voltage between a received phase-cut AC half-wave and a neutral value is larger 5 than a predetermined threshold, and a second logical value when said voltage between said received phasecut AC half-wave and said neutral value is smaller than said predetermined threshold.

3. A driver device (501, 1201) according to

10 claim 2, wherein said processor (612) is configured to :

- detect a relative duration (702) of receiving said first logical value as an input signal in comparison to a duration (703) of receiving said second logical

15 value as an input signal, and

- control said amount of electric power provided by said power converter (505) in proportion to said relative duration (702) .

4. A driver device (501, 1201) according to

20 claim 3, wherein said interface circuit (613) comprises an analog to digital converter configured to provide, as input signals to said processor (612), sampled digital representations of said received phasecut AC half-waves in more bits than one.

25 5. A driver device (501, 1201) according to claim 4, wherein said processor (612) is configured to :

- detect from said digital representations a relative duration (702) of uncut portions of said phase-cut AC

30 half-waves in comparison to a duration (703) of cut portions of said phase-cut AC half-waves, and

- control said amount of electric power provided by said power converter (505) in proportion to said relative duration (702) .

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6. A driver device (501, 1201) according to any of the preceding claims, wherein said controller part (612, 613) is configured to detect a sequence of receiving (802) and not receiving (801) phase-cut AC

5 half-waves at said control input (506) and to select a control mode of controlling said amount of electric power provided by said power converter (505) on the basis of said detected sequence.

7. A driver device (501, 1201) according to

10 claim 6, wherein said controller part (612, 613) is configured to select among at least a dimming mode and a colour changing mode as a response to a detected sequence of receiving (802) and not receiving (801) phase-cut AC half-waves at said control input (506),

15 wherein said dimming mode is a mode in which said controller part (612, 613) is configured to control an overall amount of electric power provided by said power converter (505) on the basis of said detected timing, and wherein said colour changing mode is a mode

20 in which said controller part (612, 613) is configured to control relative amounts of electric power directed to at least two separate outputs of the driver device on the basis of said detected timing.

8. A driver device according to any of the

25 preceding claims, wherein said controller part (612, 613) is configured to:

- examine features of signals received at said control input (50 6),

- detect, on the basis of said examining, which proto-

30 col among a number of predetermined protocols the received signals adhere to,

- interpret said signals as commands of the detected protocol, and

- respond to said received signals by executing said

35 commands.

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9. A method for driving light sources, comprising :

- generating electric power for said light sources from a received operating voltage,

5 - receivingphase-cut AC half-waves at electric power distribution network voltage, and

- detecting a timing of said received phase-cut AC half-waves, characterized in that the method comprises

10 - receiving said phase-cut AC half-waves as control signals separately from said operating voltage,

- converting information encoded into said timing of said received phase-cut AC half-waves into input signals to a processor, and

15 - using said processor to control an amount of said provided electric power on the basis of said detected timing.

10. A method according to claim 9, wherein:

- said detecting of said timing of said received

20 phase-cut AC half-waves comprises detecting a relative duration (702) of an absolute value of the AC voltage being larger than a predetermined threshold in relation to said absolute value of the AC voltage being smaller (703) than said predetermined threshold,

25 - said controlling of said amount of said provided electric power comprises making said provided electric power proportional to said relative duration (702) .

11. A method according to any of claims 9 or

10, comprising:

30 - detecting a sequence of receiving (802) and not receiving (801) said phase-cut AC half-waves, and

- selecting a control mode of controlling said amount of provided electric power on the basis of said detected sequence.

12. A method according to claim 11, wherein said selecting of a control mode comprises selecting among at least a dimming mode and a colour changing mode, wherein said dimming mode is a mode in which an

5 overall amount of said provided electric power is controlled on the basis of said detected timing, and wherein said colour changing mode is a mode in which relative amounts of electric power directed to at least two separate outputs is controlled on the basis

10 of said detected timing.

13. A method according to any of claims 9 to

12, comprising:

- examining features of received signals,

- detecting, on the basis of said examining, which

15 protocol among a number of predetermined protocols the received signals adhere to,

- interpreting said signals as commands of the detected protocol, and

- responding to said received signals by executing

20 said commands.