EP2368407B1 - Processor and device for operating groups of leds using pwm - Google Patents

Description

The invention relates to a device and method for operating lamps.

Technical area

Such devices are used in lighting systems to achieve a colored or flat lighting of rooms, paths or escape routes. Usually, the bulbs are driven by operating devices and activated as needed. For such illumination, organic or inorganic light emitting diodes (LED) are used as the light source.

State of the art

For lighting, instead of gas discharge lamps and incandescent lamps, light-emitting diodes are also increasingly being used as the light source. The efficiency and luminous efficacy of light-emitting diodes is being increased more and more so that they are already being used in various general lighting applications. However, light emitting diodes are point sources of light and emit highly concentrated light.

However, today's LED lighting systems often have the disadvantage that the color output or brightness may change due to aging or replacement of individual LEDs or LED modules. In addition, the secondary optics has an impact on the thermal management, as the heat radiation is hindered. It may also be due to from aging and heat to a change in the phosphor of the LED.

From the EP 1016062 it is known to drive LEDs with several parallel PWM signals. In this case, all PWM signals have an identical uniform frequency among each other as well as in terms of time. Furthermore, it is provided that the PWM control takes place simultaneously, ie the switch-on edges of all PWM signals are simultaneous.

The same concept of PWM signals for LEDs with uniform frequency and simultaneous switch-on edges is also known from the US 5420482 (See, for example, there the figure 13).

In these known approaches, there is the problem that the PWM switching with a uniform frequency and / or with simultaneous switch-on flanks on the one hand causes problems with regard to electromagnetic interference ("EMC compatibility"). Additionally or alternatively, a voltage supply upstream of the PWM module, for example a preferably clocked PFC, is also heavily loaded by the simultaneous switching.

The publication WO 2008/025153 A1 describes a lighting system having three LED channels for driving red, green and blue LEDs, respectively. First PWM signals for these three LED channels are converted to respective analogue signals. Each analog signal is compared with a reference waveform to produce a corresponding second PWM signal for driving the respective LEDs. The phases of the three reference waveforms are distributed over a period of time, in particular, they are each spaced by a third of the PWM period.

Presentation of the invention

Background of the invention is as for WO 2008/025153 the reduction of load jumps and disturbances and thus the improvement of the EMC behavior of the LED driver. When all stages are switched on simultaneously, high load changes and switching edges occur. These must be through the PFC (Load change) or the filter circuit (switching edges) are compensated.

• die Einschaltflanke wenigstens eines PWM-Signals von der wenigstens eines weiteren PWM-Signals zumindest zeitweise abweicht und somit nicht simultan ist, und
• fakultativ die Frequenz eines oder mehrerer PWM-Signale zumindest zeitweise zeitlich nicht konstant ist, und/oder
• fakultativ die Frequenz wenigstens eines PWM-Signals wenigstens zeitweise von der wenigstens eines weiteren PWM-Signals abweicht.

According to the central idea of the invention, this is achieved in that

• the switch-on edge of at least one PWM signal deviates at least temporarily from the at least one further PWM signal and is therefore not simultaneous, and
• optionally, the frequency of one or more PWM signals is not constant at least temporarily, and / or
• optionally, the frequency of at least one PWM signal deviates at least temporarily from the at least one further PWM signal.

The object is solved by the features of the independent claims, wherein the features of the dependent claims further develop the central idea of the invention particularly advantageous.

The solution according to the invention furthermore relates to a device for operating at least two light sources, electric energy being supplied to at least two light source arrangements, each consisting of one or more light sources, by a common electrical supply unit, wherein a first light source arrangement and at least one second light source arrangement provide electrical Energy is supplied in the form of PWM packets, wherein the timing of the PWM packets is tuned between the different illuminant arrangements.

In this way it is possible to achieve a very consistent and uniform illumination of a surface by a light emitting diode with light emitting diodes, wherein the Load on the serving units is kept as low as possible.

Description of the preferred embodiments

Fig. 1

zeigt eine erfindungsgemäße Vorrichtung zum Betreiben von LED,

Fig. 2

zeigt eine weitere erfindungsgemäße Vorrichtung zum Betreiben von LED, und

Fig. 3 und 4

zeigen erfindungsgemäße Abfolgen der PWM-Pakete.

The invention will be explained in more detail with reference to the accompanying drawings. Show it:

Fig. 1

shows an inventive device for operating LED,

Fig. 2

shows a further device according to the invention for operating LED, and

3 and 4

show sequences according to the invention of the PWM packets.

The invention will be explained with reference to an embodiment of an apparatus for operating LEDs. This device comprises a driver module, and an LED module controlled by the driver module with at least one LED 5, with a memory for storing information about the LED module, wherein the memory is stored either in the driver module or in the LED Module can be contained and the information in the memory can be changed.

The memory may be included in a driver module 1. The driver module 1 has connections 2 and 3 to which an LED or a plurality of LEDs 5 can be connected via the wiring 4. The LEDs 5 may be located on a common LED module.

The individual LEDs 5 can be controlled via different output stages, drivers or converters.

The information in the memory can be changed based on a calibration measurement. The information in the memory can be changed by a correction factor. The information in the memory may be modified by a correction factor that has become due to a calibration measurement. The correction factor can be changed by a user, for example via a specification via an interface 7. The interface can use both a wired and a wireless transmission. The correction factor may depend on the aging or the operating time of the LED module. The correction factor may be dependent on the temperature of the LED module.

To perform the calibration, a sensor 6 can be used, which is introduced into the lighting system for the calibration measurement. The correction factor may be dependent on a color measurement. The color measurement can be done by means of an RGB color measurement, for example a CCD sensor. In this case, the sensor 6 would be an RGB color sensor. The determination of the correction factor can be repeated at regular intervals. The memory can be read out by the driver module via a digital interface.

The memory can be located on the LED module and can be read by the user when the module is replaced. The memory may be located on the LED module and prior to replacement of the module by the driver module due to user signaling be read out. The memory may be placed in a calibrator.

The signaling for reading the memory on the LED module can be done by the user by a switching sequence on the supply voltage, a digital control command or by other signaling.

After replacing the LED module, the information read out can be stored in the memory of the new LED module.

The driver module can forward the information stored in memory via a digital interface to other driver modules.

For calibration one or more LED modules can be switched off. For calibration, only one LED module can be switched on at a time.

The color measurement can be performed with a color sensor (eg CCD sensor).

The color sensor may be placed so that it can receive a portion of the light emitted by the LED modules.

The color sensor may be placed so that it is shielded from ambient light and can receive only light emitted by the LED modules. This foreclosure can be done by a cover that is specially designed for the calibration measurement. On this cover 11, the sensor 6 may be located. The sensor 6 can also be on the reflector 10 of the LED Luminaire be placed. The sensor 6 may be placed to directly or indirectly receive the light of the LED 5 of the LED module.

During calibration, the color location and the intensity of the LED 5 can be stored.

During calibration, the individual LED modules can be switched on and calibrated one after the other.

The calibration can be used to determine the colors of the connected LED modules. The individual colors or color locations as well as the intensities of the respectively driven LEDs 5 are determined. From the combination of the individual calibration measurements, which are carried out in succession, the assignment of the colors and the mixture of the individual LEDs 5 required for the output of a desired color by the LED illumination can be determined.

It can be constructed according to the invention, a light with LED. The driver module may include a switching regulator, such as an AC-DC converter, a DC-DC converter, a current sink, or a power source. The driver module may include a PFC (Active Power Factor Correction Circuit), or a PFC (Active Power Factor Correction Circuit) may precede the driver module. The driver module can have a potential separation.

The operation of the LEDs may be such that the LED module is driven by at least one LED from a driver module, and a memory for storing information about the LED module is present, wherein Information can be stored or modified in memory. The information in the memory can be changed based on a calibration measurement.

The driver module can be formed by a switching regulator or by a current sink or a current source. If a switching regulator is used as the driver module, then it can internally operate at a higher frequency than the frequency with which the LED or the LED module is controlled. The internal frequency with which the switch of the switching regulator is controlled, can be in the range of 10 kHz to several MHz, while this internal frequency is superimposed on a low frequency corresponding to the frequency of the at least one PWM packet.

The information in the memory can be changed by a correction factor.

Thus, a method for operating at least two light sources is made possible, wherein electric energy is provided to at least two illuminant arrangements, each consisting of one or more bulbs, by a common electrical supply unit, wherein a first illuminant arrangement and at least one second illuminant arrangement contains electrical energy Form of PWM packets is supplied, wherein the timing of the PWM packets is tuned between the different illuminant arrangements.

Examples of the control of three lamp assemblies are in the 3 and 4 represented, wherein the lamp assemblies electrical energy can be supplied in the form of PWM packets.

The at least two illuminant arrangements can be controlled such that the time center of a PWM packet of the first illuminant arrangement coincides with the temporal midpoint of a PWM packet of at least one second illuminant arrangement or follows one another closely in time. In Fig. 4 is an example of a control with an offset of the time centers of the individual PWM signals shown.

The timing of the PWM packets can be coordinated over the entire dimming range of the lamps.

The at least two illuminant arrangements can be controlled such that, alternatively or additionally, the time centers of the PWM packets of the illuminant arrangements are shifted in time with respect to one another with an offset value, so that the flanks of the PWM packets to the illuminant arrangements do not occur at the same time.

At least temporarily, the switch-on edge of at least one of a plurality of parallel PWM signals (ie, the signals containing the PWM packets) may be shifted in time to at least one further PWM signal, so that the problem of simultaneous PWM control no longer exists. This offset (offset value) can be internally or externally variable or fixed. In particular, for example, the offset could correspond to the entire turn-off phase of a PWM signal, ie, with the pulse duty ratio unchanged, the corresponding LED within a PWM period becomes first switched off and then turned on. A PWM signal can therefore be inverted, ie at the start of each cycle, triggered by an interrupt signal, for example, the switch-off phase and only then the switch-on phase of the LED can be controlled.

Alternatively, the offset could also be chosen such that the turn-on edges for the PWM signals are generated uniformly distributed over the PWM period. A third alternative is to randomly select offset. In Fig. 3 an example of a drive with an offset of the individual PWM signals is shown.

The offset may already be present during the generation of the PWM signals, or else be inserted deliberately in the case of simultaneously generated PWM signals on the path between the PWM generation and the LEDs.

The PWM signals can be generated starting from one or even from several clocks.

The offset value can be selected depending on the dimming level of the lamps.

Optionally, the frequency of at least one PWM signal may also change at least temporarily, so that a combined PWM / FM (frequency modulation) is present. It would be conceivable, for example, to set the frequency as a function of the duty cycle of the PWM signal.

In addition, the frequency of at least one PWM signal at least temporarily from the distinguish at least one other PWM signal. In turn, one or more clocks may be present. For example. For example, one frequency may be a multiple of another frequency. At least one frequency can be shifted after generation of uniform PWM switching frequencies, for example by a capacitor.

• Für jeden PWM-Kanal oder wenigstens einen abweichenden PWM-Kanal kann unabhängig der notwendige PWM-Stellwert gerechnet wird und das Resultat in ein Hardwareregister geschrieben wird.

A purely for example described and by no means limiting implementation may, for example, be as follows:

• For each PWM channel or at least one deviating PWM channel, the required PWM control value can be calculated independently and the result written to a hardware register.

The hardware then adopts the new value at the next zero crossing of the period. Through the center PWM method (triangle as in Fig. 4 shown) comes at different PWM position, none of the flanks directly at the same time to change up to four channels. The only exception here is with the same dimming position all flanks on each other, but could be integrated as an improvement after the calculation so that is played with the PWM resolution, ie that deliberately shifts the channels by 1 bit PWM to achieve a blurring (see example of Fig. 3 ).

da der Step dann alle 10ms ist, sollte es noch nicht als Flackern wahrgenommen werden, zudem wählen wir die Auflösung jeweils recht hoch, sodass ein Bit Versatz nicht viel ausmachen dürfte.This shift can then be changed, for example, per period additionally, so that the mean value over time is again stable. $$\left(\mathrm{T}\mathrm{0}=\mathrm{1022}.\mathrm{1024}.\mathrm{1021}.\mathrm{1025}\to \mathrm{T}\mathrm{0}+\mathrm{1}=\mathrm{1024}.\mathrm{1022}.\mathrm{1025}.\mathrm{1021}\to \mathrm{T}\mathrm{0}+\mathrm{2}=\mathrm{1022}.\mathrm{1024}.\mathrm{1021}.\mathrm{1025}\right)$$

since the step is then every 10ms, it should not be perceived as a flicker yet, we also choose the resolution quite high, so that a bit offset should not make much.

The luminous means of the first and / or at least the second luminous means arrangement can be inorganic or organic light-emitting diodes.

The lighting means of the first and / or at least the second lighting arrangement can emit a different light spectrum.

Thus, an operating device can be made possible in the above-mentioned method can be performed.

Thus, an illumination system can be made possible which has at least two light sources in which a method or operating device mentioned above is used.

In Fig. 2 schematically a circuit for the controlled operation of light-emitting diodes (LED) is shown, which represents an example of a driver module. In the example shown, two light-emitting diodes are connected in series, however, it is just an advantage of the present invention that the operating circuit adapts very flexibly to the type and number of light-emitting diodes (LED) also connected in series.

The operating circuit is supplied with an input DC voltage Vin, which of course can also be a rectified AC voltage.

A series circuit between a semiconductor power switch S1 (for example, a MOSFET) and a freewheeling diode D1 energizes in the switched-on state of the switch S1 an inductance L1 by means of the current flowing through the switch. In the switched-off state of the switch S1, the energy stored in the coil L1 discharges in the form of a current i through a capacitor C1 and the light-emitting diode path LED.

There is provided a control and / or regulating circuit SR, which specifies the timing of the switch S1, for example in the form of hochfreugenten modulated signals as a manipulated variable of the control of the LED power. The control and / or regulating circuit SR can, for example, apply a hysteretic current regulation.

By means of a measuring resistor RS, the control and / or regulating circuit SR detects the current through the switch S1 (in the switched-on state of the switch S1).

Via a voltage divider R1, R2, the control and / or regulating unit SR can detect the potential on the lower-potential side of the LED path.

Another voltage divider R3, R4 allows the detection of the supply voltage.

The driver module is formed in this example by a buck converter, but can also be formed for example by a boost converter, buck-boost converter or other switching regulator or by a current sink or a power source. The switch S1 is driven internally by the control and / or regulating circuit SR at a higher frequency than the frequency, as with which the LED or the LED module are controlled. The internal frequency with which the switch S1 of the switching regulator is controlled may be in the range of 10 kHz to several MHz, while this internal frequency is superimposed on a low frequency which corresponds to the frequency of the at least one PWM packet. Thus, the LED module may be driven with a low frequency PWM packet, which PWM packet may ripple due to the high frequency operation of the switch S1 of the driver module during turn-on time. The ripple that may result due to the high frequency operation of the switch S1 of the driver module may be reduced by the capacitor C1.

The low frequency of the at least one PWM packet that is superimposed may be dictated by an external controller such as a microcontroller or other central control unit. By controlling the driver module with such low-frequency PWM packets, the driver module can be temporarily deactivated and thus a brightness control can be achieved by the PWM packets and color mixing using different light spectra of the lamps.

For example, for RGB color mixing, the three colors of the RGB LED module can each be driven by one driver module, the three driver modules being controlled via three PWM channels.

Claims (12)

1. Device for operating at least two illuminant arrangements, each consisting of one or more illuminants, preferably LEDs, wherein the device makes electrical energy available to the at least two illuminant arrangements,
   and wherein electrical energy in the form of PWM packets is fed to a first illuminant arrangement and at least one second illuminant arrangement,
   characterized
   in that the switch-on edge of at least one PWM packet of a first illuminant arrangement deviates at least occasionally from the switch-on edge of at least one further PWM packet of a second illuminant arrangement, wherein the at least two illuminant arrangements are driven such that the temporal midpoint of a PWM packet of the first illuminant arrangement corresponds to or temporally closely follows the temporal midpoint of a PWM packet of at least one second illuminant arrangement.
2. Device according to Claim 1, characterized in that the temporal sequence of the PWM packets is co-ordinated over the entire dimming range of the illuminants.
3. Device according to either of the preceding claims, characterized in that the at least two illuminant arrangements are driven such that in addition the temporal midpoints of the PWM packets of the illuminant arrangements are temporally shifted relative to one another with an offset value, in order that the edges of the PWM packets to the illuminant arrangements are not effected simultaneously,
   wherein the offset value is chosen depending on the dimming level of the illuminants.
4. Device according to any of the preceding claims, characterized in that the illuminants of the first and/or at least the second illuminant arrangement(s) are inorganic or organic light-emitting diodes.
5. Device according to any of the preceding claims, characterized in that the illuminants of the first and/or at least the second illuminant arrangement(s) emit a different light spectrum.
6. Device according to any of the preceding claims, wherein the temporal deviation of the switch-on edge is internally or externally variable or is fixedly predefined.
7. Device according to any of the preceding claims, wherein the temporal deviation is already present when the PWM signals are generated, and/or is inserted in a targeted manner on the path between the PWM generation and the LEDs.
8. Device according to any of the preceding claims, characterized
   in that the frequency of at least one PWM packet deviates at least occasionally from the frequency of at least one further PWM packet of a second illuminant arrangement,
   wherein the frequency of one PWM packet is the multiple of a further frequency.
9. Device according to Claim 8,
   wherein at least one frequency is shifted after the generation of uniform PWM switching frequencies e.g. by a capacitor.
10. Operating unit, comprising a device according to any of the preceding claims.
11. Lighting system comprising at least two illuminants and two functionally interconnected devices according to any of Claims 1 to 9.
12. Method for reducing the loading of a voltage supply and/or for improving the EMC compatibility when driving LEDs with PWM signals,
    wherein the switch-on edge of at least one PWM signal deviates temporally from the at least one further PWM signal at least occasionally and is therefore not simultaneous,
    wherein the at least two illuminant arrangements are driven such that the temporal midpoint of a PWM packet of the first illuminant arrangement corresponds to or temporally closely follows the temporal midpoint of a PWM packet of at least one second illuminant arrangement.

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