WO2010081613A1

WO2010081613A1 - Processor and device for operating groups of leds using pwm

Info

Publication number: WO2010081613A1
Application number: PCT/EP2009/067631
Authority: WO
Inventors: Michael Zimmermann; Dominique Combet
Original assignee: Tridonicatco Schweiz Ag
Priority date: 2008-12-23
Filing date: 2009-12-21
Publication date: 2010-07-22
Also published as: EP2368407B1; DE102009005819A1; EP2368407A1; DE112009003815A5

Abstract

Method for operating at least two lighting means, wherein electrical energy is provided to at least two lighting means arrangements by a common electrical supply unit, each of said arrangements comprising one or more lighting means, wherein one first lighting means arrangement and at least one second lighting means arrangement are fed with electrical energy in the form of PWM packets, wherein the temporal sequence of PWM packets between the various lighting means arrangements is established.

Description

METHOD AND DEVICE FOR OPERATING GROUPS OF LEDS BY PWM

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

Technical area

Such devices are used in lighting systems to provide colored or flat lighting

Spaces, paths or escape routes to reach. Usually, the bulbs of

Operating devices activated and activated if necessary. For such illumination, organic or inorganic light emitting diodes (LED) are used as the light source.

State of the art

For lighting are used instead of gas discharge lamps and incandescent lamps more often than light-emitting diodes

Light source used. 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 due to aging or by replacing individual LEDs or LED modules, the color output or the brightness can change. In addition, the secondary optics have an influence on the thermal management, since 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 EP 1016062 it is known to drive LEDs with a plurality of parallel PWM signals. All PWM

Signals to each other as well as temporally considered by itself an identical uniform frequency.

Furthermore, it is provided that the PWM control takes place simultaneously, i. the switch-on edges of all PWM signals are simultaneous.

The same concept of the PWM signals for LEDs with uniform frequency and simultaneous switch-on edges is also known from US Pat. No. 5,420,482 (see, for example, FIG. 13 there).

In these known approaches, there is the problem that the PWM switching with uniform frequency and / or with simultaneous switch-on flanks on the one hand causes problems with electromagnetic interference ("EMC compatibility") a preferably clocked PFC, heavily loaded by the simultaneous switching.

Presentation of the invention

Background of the invention is the reduction of load transients 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.

According to the central idea of the invention, this is achieved by:

- The switch-on edge of at least one PWM signal from the at least one further PWM signal deviates at least temporarily and is therefore not simultaneous, and / or

- The frequency of one or more PWM signals is at least temporarily not constant in time, and / or

- The frequency of at least one PWM signal at least temporarily deviates from the at least one further PWM signal.

The object is achieved 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 inventive solution further relates to a device for operating at least two light sources, wherein by a common electrical supply unit electrical energy to at least two lamp assemblies, each consisting of one or more lamps, is provided, wherein a first lamp arrangement and at least one second lamp arrangement 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 gleichmaßige illumination of a flat 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

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

1 shows an inventive device for operating LED,

Fig. 2 shows a further device according to the invention for operating LED, and

Figures 3 and 4 show sequences of the PWM packets according to the invention.

The invention will be described below with reference to an exemplary embodiment of a device for operating

LEDs explained. This device has a driver module, and an LED module controlled by the driver module with at least one LED 5, with a memory for

Storage of information about the LED module, wherein the memory may be contained either in the driver module or in the LED module and the information in the memory can be changed.

The memory may be included in a driver module 1. The driver module 1 has terminals 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 depend on the temperature of the LED module.

To perform the calibration, a sensor 6 can be used, which is introduced into the illumination system for the calibration measurement. The correction factor may depend 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 Kalibriergerat.

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 can be placed so that it is shielded from ambient light and can only receive 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 can 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 1OkHz 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 for the control of three illuminant arrangements are shown in FIGS. 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 light-emitting device coincides with the time center of a PWM packet at least one second light-emitting device successively in time. FIG. 4 shows an example of a control with an offset of the time centers of the individual PWM signals.

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 so that, alternatively or additionally, the time centers of the PWM packets of the illuminant arrangements are shifted in time relative 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 keying 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. FIG. 3 shows an example of a control with an offset of the individual PWM signals.

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 depend on the dimming level of the

Illuminants are selected.

It may also be the frequency of at least one PWM

At least temporarily temporally changing the signal, 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.

Alternatively or additionally, 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.

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. By the center PWM method (triangle as shown in Fig. 4) comes at different PWM position none of the edges directly at the same time to change up to four channels. The only exception here is that all flanks coincide with the same dimming position, but this could be integrated as an improvement after the calculation, which is played with the PWM resolution, i. that one consciously shifts the channels by 1 bit each PWM to achieve a blurring.

This shift can then be made e.g. per period additionally change, so that the mean value over time is again stable.

(TO = 1022.1024.1021.1025 -> TO + 1 = 1024, 1022, 1025.1021 -> TO + 2 = 1022.1024.1021.1025) 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 was not allowed to 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 enabled in which 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.

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

The operating circuit is supplied with an input DC voltage Vm, which of course can also be a rectified AC voltage. A series circuit between a semiconductor power switch Sl (for example, a MOSFET) and a freewheeling diode Dl energizes in the on state of the switch Sl an inductance Ll by means of the current flowing through the switch. In the switched-off state of the switch Sl, the energy stored in the coil L1 is discharged 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 Sl, for example in the form of hochfreuqenten 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 Sl (in the switched state of the switch Sl).

Via a voltage divider Rl, 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 Sl is driven internally by the control and / or regulating circuit SR with 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 the turn-on time. The ripple, which may result from the high-frequency operation of the switch S1 of the driver module, can 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 controlled by one driver module, the three driver modules being controlled via three PWM channels.

Claims

Claims :

1. A device for operating at least two light sources, preferably LEDs, being provided by a common electrical supply unit electrical energy to the at least two lamp assemblies, each consisting of one or more bulbs, wherein a first lamp arrangement and at least one second lamp arrangement electrical Energy in the form of PWM packets is supplied, characterized in that between the different illuminant arrangements, the timing of the PWM packets is tuned.

2. Device according to claim 1, characterized in that the at least two illuminant arrangements are 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.

3. Device according to one of the preceding claims, characterized in that the tuning of the time sequence of the PWM packets over the entire dimming range of the lamps takes place.

4. Device according to one of the preceding claims, characterized in that the at least two lamp assemblies are driven so that in addition the time centers of the PWM packets of the lamp assemblies are shifted in time with an offset value against each other, so that the edges of the PWM packets to the Lamp arrangements do not take place at the same time.

5. Apparatus according to claim 4, characterized in that the offset value is selected depending on the dimming level of the lighting means.

6. Device according to one of the preceding claims, characterized in that the lighting means of the first and / or at least the second illuminant arrangement are inorganic or organic light-emitting diodes.

7. Device according to one of the preceding claims, characterized in that the lighting means of the first and / or at least the second lighting means emit a different light spectrum.

8. An apparatus for operating at least two lamp assemblies, each consisting of one or more lamps, preferably LEDs, wherein the device provides electrical energy to the at least two lamp assemblies available, and wherein a first lamp arrangement and at least one second lamp arrangement electrical power is supplied in the form of PWM packets, characterized in that the switch-on edge of at least one PWM packet of a first luminous means arrangement deviates at least temporarily from the switch-on edge of at least one further PWM packet of a second illuminant arrangement.

9. Apparatus according to claim 8, wherein the time deviation of the switch-on edge is internally or externally variable or fixed.

10. Apparatus according to claim 8 or 9, wherein the time deviation already exists in the generation of the PWM signals, and / or is inserted selectively on the route between the PWM generation and the LEDs.

11. Apparatus for operating at least two light sources, preferably LEDs, wherein the apparatus provides electrical energy to the at least two illuminant arrangements, each consisting of one or more bulbs, wherein a first light assembly and at least one second light assembly electrical energy in the form of PWM packets is supplied, in particular according to one of claims 8 to 10, characterized in that the frequency of at least one PWM packet varies at least temporarily.

12. Apparatus for operating at least two

Lamp assemblies, each consisting of one or more light sources, preferably LEDs, the device provides electrical energy to the at least two lamp assemblies available, and wherein a first lamp assembly and at least a second lamp assembly is supplied electrical energy in the form of PWM packets, in particular according to one of claims 8 to 11, characterized in that the frequency of at least one PWM packet deviates at least temporarily from the frequency of at least one further PWM packet of a second illuminant arrangement.

13. The apparatus of claim 12, wherein the frequency of a PWM packet is the multiple of another frequency.

14. The apparatus of claim 12, wherein the differing frequency is not a multiple of the other PWM frequency (s).

15. The apparatus of claim 11 or 12, wherein at least one frequency after generation of uniform PWM switching frequencies, for example, is displaced by a capacitor.

16. An apparatus for operating at least two lamp assemblies, each consisting of one or more lamps, preferably LEDs, wherein the device provides electrical energy to the at least two illuminant arrangements, and wherein electrical energy is supplied to a first illuminant arrangement and at least one second illuminant arrangement in the form of PWM packets, characterized in that

- The frequency of one or more PWM signals is at least temporarily temporally not constant, and / or - the frequency of at least one PWM signal at least temporarily deviates from the at least one further PWM signal.

17. Operating device, comprising a device according to one of the preceding claims.

18. Lighting system comprising at least two lighting means and two functionally interconnected device according to one of claims 1 to 16.

19. A method for reducing the load on a power supply and / or for improving the EMC compatibility when driving LEDs with PWM signals, comprising one or more of the following options:

- 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 at least temporarily is not simultaneous, and / or

- The frequency of one or more PWM signals at least temporarily is not constant in time, and / or

- The frequency of at least one PWM signal deviates at least temporarily from the at least one further PWM signal.