WO2010035291A1

WO2010035291A1 - System and method for lighting control of led illuminating apparatuses

Info

Publication number: WO2010035291A1
Application number: PCT/IT2008/000608
Authority: WO
Inventors: Leonardo Cantalupi
Original assignee: CANTALUPI LIGHTING Srl
Current assignee: CANTALUPI LIGHTING Srl
Priority date: 2008-09-24
Filing date: 2008-09-24
Publication date: 2010-04-01
Anticipated expiration: 2011-03-24

Abstract

The present invention relates to an electronic system suitable for power-supplying and lighting control of monochromatic LED illuminating apparatuses with Low-voltage DC driver, particularly indicated in lighting for civil and nautical use for control of up to a high number (>30) of illuminating apparatuses, and power- supplying and controlling the illuminating apparatuses with dedicated drivers by means of the sole two power supply wires.

Description

SYSTEM AND METHOD FOR LIGHTING CONTROL OF LED ILLUMINATING

APPARATUSES DESCRIPTION

The present invention relates to an electronic system suitable for power- supplying-and lighting control of monochromatic LED illuminating apparatuses with Low-voltage DC driver, particularly indicated in lighting for civil and nautical use for control of up to a high number (>30) of illuminating apparatuses.

To date, various methods exist for power supplying and lighting control of LED illuminating apparatuses. One of the most common modes provides one or more power LEDs, connected thereamong in series or in parallel, to be housed inside the illuminating apparatus; then a driver/dimmer provides (current) power supply and lighting control. This system provides to power supply the various illuminating apparatuses in series. This system leads to management problems; in fact, in case of breaking of an apparatus of the series the others turn off as well and, moreover, due to the low-voltage power supplying the quantity of apparatuses manageable by each individual driver/dimmer is low (1 - 2 apparatuses) with great complication of the electric circuit in case a considerable quantity of apparatuses has to be managed.

According to a further known mode, beside the power LEDs inside the apparatus it is also housed a driver that can be controlled by means of one or two additional wires with PWM system or digital control. This system can control a high number

(>10) of apparatuses by means of a dedicated remote dimmer. In case a mere turning on and off of the apparatuses is desirable, a connecting (in parallel) of the two power-supply wires of the driver suffices; yet, in case it is also desirable to control lighting, to each individual apparatus there should be connected one or more wires, in some cases also shielded, uniting them to the remote dimmer. This system provides the use of two conductors for what concerns the power-supplying of the drivers, and one or more conductors for light control; this complicates things in case of an existing installation (replacement of a halogen light installation with a LED light one) and in case of choices on a new installation. Moreover, this system complicates the wiring of the installation.

There are also other systems, though still under development, providing the use of receivers inside of the drivers contained in the apparatuses; these receivers can decode logic signals transmitted on the power supply line (conveyed wave systems) by specific power supplies/dimmers or can receive and decode signals radio- transmitted from a remote controller. These systems can control a high number (>30) of apparatuses with the connection of the mere power supply wires, are compatible with existing installations, and the lamps, if desired, can be only switched on/off by interrupting the power supply (not by using the dimmering option). However, these systems often have an addressing of the apparatuses (coding) or provide specific settings such as to be installed only by specifically qualified staff, drivers are complex and costly and, moreover, conveyed-wave and radio systems are not yet tested for this type of use, and are not free from inconveniences.

As it is known, in order to emit light LEDs need to be traversed by a preset electric current at a certain voltage. On the market there are devices (drivers) that, when correctly power-supplied, provide the current required for LED ignition. Some of these devices possess an input to which there can be applied a PWM signal providing to change, according to the Duty Cycle applied, the current supplied to the

LED, thereby varying the lighting thereof. However, these drivers in order to operate need at least three wires, two for the power-supplying and at least one for the PWM signal; this constitutes a marked limitation, especially so when it is desirable to replace the illuminating apparatuses in already laid classic installations, providing only the two power supply wires.

Therefore, object of the present invention is to solve the above-mentioned problems, by proposing a system for lighting control of LED illuminating apparatuses as defined in independent claim 1. Further object of the present invention is to provide a method for lighting control of LED illuminating apparatuses as defined in independent claim 21.

Preferred features of the present invention are set forth in the corresponding dependent claims.

The present invention entails several evident advantages. In particular, the system according to the present invention provides a PWM- operating dimmer/power supply, power-supplying and controlling the illuminating apparatuses with dedicated drivers by means of the sole two power supply wires.

The system according to the present invention can control a high number (>30) of illuminating apparatuses. This leads to a remarkable simplification of the installation, by utilizing a PWM power system long-tested to date in several environments, demonstrating low sensitivity to disturbances.

According to market needs, and according to the new power LED modules that will be marketed, there could be manufactured dimmers/power supplies with different powers and drivers adjusting to the features of the new LEDs.

Therefore, with a system according to the present invention, it is possible to manufacture a connection circuit similar to that of a classic halogen lamp system (respecting polarities at connecting) with the apparatuses connected in parallel, with only the two power supply wires, that can be directly powered (OFF/ON) or connectible (even subsequently) to the dimmer/power supply, with the option of adding or removing illuminating apparatuses at will (respecting, when used, the maximum capacity of the dimmer/power supply).

Further advantages, as well as the features and the operation modes of the present invention will be made apparent from the following detailed description of an embodiment thereof, given by way of example and not for limitative purposes, making reference to the figures of the annexed drawings, wherein: Figures 1 to 4 are sketches of known control systems;

Figure 5 is a block diagram of a control system according to the present invention; and

Figure 6 is a diagram in greater detail of the system of figure 5. To describe the present invention, hereinafter reference will be made to the above-indicated figures.

Referring initially to Figures 1 to 4, these refer to some control systems currently in use and show the above-disclosed limitations thereof.

In particular, Figure 1 refers to a known system, in which power LEDs are connected thereamong in series and power-supplied via an individual driver/dimmer. Figures 2 and 3 refer to known systems in which lighting control occurs via dedicated control lines, different from the power-supplying line.

Figure 4 refers to a known system, in which lighting is adjusted by means of ancillary signal receiving/transmitting devices, which may operate by radio and/or conveyed-wave technology. The present invention is based on a control method described hereinafter.

First of all, a low-voltage DC power supply voltage is provided. From this power supply voltage it is generated a PWM-type control signal CS having a duty cycle settable between a minimum value P_MIN > 0% and a maximum value P_MAX < 100%. Then, it is generated a power supply signal for a LED illuminating apparatus such that its brightness/lighting may range between zero and a maximum value L_MAX depending on the duty cycle of the control signal CS.

Preferably, the duty cycle of the control signal CS may range from 10% to 95%. Such a control signal CS is then software-processed and utilized to generate a PWM output signal PWM_OUT whose duty cycle ranges between 0% and 100%, correspondingly to the duty cycle of the control signal CS.

Lastly, it is generated a constant-current power supply signal PWR_LED for power-supplying the LEDs, in which the current value is a function of the duty cycle of the PWM output signal PWMJDUT.

The next Figures 5 and 6 refer instead to a control system according to the present invention. Of course, the system 1 of the present invention comprises a low-voltage DC power supply module (e.g. 10-30 V, DC). Said module will not be described in detail, as considered of course within reach of a technician of average skill in the art.

The system 1 further comprises an adjustment module 2 for the power supply voltage, i.e. a so-called dimmer. The adjustment module 2, according to the present invention, is manufactured in

PWM technology and outputs a control signal CS having a fixed frequency f and therefore a period T=1/f, and a duty cycle settable between a minimum value P_MIN > 0% T and a maximum value P_MAX < 100% T.

Preferably, the minimum value is selected at 10% T and the maximum value at 95% T. The reason for such a selection will be better explained hereinafter.

The dimmer 2 comprises a first microprocessor unit 3 equipped with output devices, apt to execute a software for generating a PWM adjustment signal RS having a given duty cycle value corresponding to defined parameters.

The adjustment signal RS, is input to an output stage 4 of the dimmer 2, which in turn outputs the control signal CS.

The output stage 4 comprises a device 5 for stabilizing the output signal CS that, preferably is of push-pull configuration type, allowing to keep the PWM-generated waveforms without big distortions even with line distances of the order of 50 meters with the power supply signal stable under both voltage levels. The dimmer 2 could advantageously provide interface means 6 for setting such parameters and therefore defining the duty cycle of the adjustment signal RS. Such interface means may be input devices, e.g. a keyboard or a remote control and a display, to allow a manual adjustment of the duty cycle by a user.

Furthermore, the interface means 6 can also comprise one or more input channels for the connection of sensors (twilight, presence or other) for an automatic adjustment of the duty cycle on the basis of data detected by the sensors themselves.

The system according to the present invention further comprises one or more drive modules 11 , again manufactured with PWM technology. Each of said modules receives as input exclusively the control signal CS and is apt to drive a corresponding LED illuminating apparatus 100 in a manner such that its lighting may range from zero to a maximum value L_MAX, depending on the duty cycle of the control signal CS.

Each drive module 11 comprises an input stage 12 having a first rectifier module 13 and a leveling module 14. The input stage 12 is powered by the control signal CS and apt to output a voltage signal V_PWR, substantially continuous and always having an amplitude > 0. According to the preferred embodiment, the rectifier module 13 is a diode, preferably a Schottky diode, whereas the leveling module 14 is of capacitive type.

The input diode 13, set in series to the power supply positive, allows energy to flow in only one direction, and therefore to preserve it in the capacitor 14 during a low transition of the input signal. The capacity of the capacitor 14 should be sized in a manner such as to ensure correct operation of the drive module 11 throughout the variation of the duty cycle being input. A Schottky diode was selected to attain the best possible energy flow, thanks to the low opening voltage.

Therefore, clearly by having available a PWM input with a duty cycle between 10% and 95%, the input stage 12 is always capable of delivering a voltage signal

V_PWR which is sufficient to power supply the entire drive module 11 , even with a

10% duty cycle and, on the other hand, of preventing the signal trace from being lost

(PWM ON/OFF switching) when the duty cycle is set at maximum (95%). Such a trace in fact is required, as it will be made evident hereinafter, for a correct operation of the system.

Therefore, the voltage signal V_PWR is utilized to power supply the drive module 11 and in particular also a second microprocessor unit 15 which receives as input the control signal CS to be acquired in a digital format.

However, preferably, prior to inputting the control signal CS to the second CPU, said signal is manipulated via a translator stage 16. This stage receives as input the control signal CS, to adjust its level prior to inputting it to said second microprocessor unit 15. According to the preferred embodiment, the translator stage

16 comprises a voltage divider 17, preferably of resistive type, adjusting the amplitude of the control signal CS input to a subsequent filter 18 made with a Schmitt-trigger buffer.

A second filtering step is operated on the second microprocessor unit 15, which comprises means 20, preferably software, for filtering the acquired input signal.

The CPU 15, by means of a "Capture"-type input, meters frequency and duty of the input signal, at every transition of the same. A software filtering reconstructs the signal also in case of presence of spikes, due to coupling disturbances on the power supply line. Moreover, read parameters are averaged and derived in a manner such as to stabilize the input signal, so that it be correctly interpreted by the CPU side. The second microprocessor unit 15 further comprises software means 21 for processing the acquired input signal, apt to generate a PWM output signal PWM-OUT whose duty cycle ranges between 0% and 100% correspondingly to the duty cycle of the control signal CS, calculate, as described, on the acquired signal. Therefore, to a 10% duty cycle of the control signal there will correspond a duty cycle of the PWM output signal PWM-OUT equal to 0%, whereas to a 95% duty cycle of the control signal there will correspond a duty cycle of the PWM output signal PWM-OUT equal to 100%.

To the duty cycle value of the PWM output signal PWM-OUT there corresponds, as it will be explained hereinafter, a lighting (brightness) value of the LED (spot) illuminating apparatus.

Therefore, the PWM output signal is generated allowing for the setting of the minimum lighting of the spot, as a consequence of an input duty cycle equal to 10%. This translation of the signal allows to always keep the drive module with a power supply level such as to have it operate normally for all lighting levels. Hence, with a 10 % duty metered at the input the spot sets the minimum lighting and with a duty equal to 95% the spot sets the maximum lighting.

Lastly, each drive module 11 comprises a constant-current generator 30, which receives as input the PWM output signal PWM_OUT and outputs a constant-current power supply signal PWR-LED for power-supplying the LED illuminating apparatus

100. The value of the generated current, and therefore the lighting (brightness) of the LED/LEDs, is a function of the duty cycle of the PWM output signal PWM-OUT.

Moreover, the system according to the present invention may advantageously provide also a temperature control, carried out through a sensor placed in each illuminating apparatus, allowing to monitor the operating junction of the LEDs and optionally, in case of overheating, decrease the power supply current so as to safeguard the device life.

The present invention has been hereto described with reference to a preferred embodiment thereof. It is understood that other embodiments might exist, all falling within the concept of the same invention, and all comprised within the protective scope of the claims hereinafter.

Claims

1. A system (1) for lighting control of LED illuminating apparatuses (100), comprising:

- a low-voltage DC power supply module; - an adjustment module (2) for power supply voltage, in PWM technology, which outputs a control signal (CS) having a duty cycle settable between a minimum value (P_MIN) > 0% and a maximum value (P_MAX) < 100%, and

- one or more drive modules (11), in PWM technology, apt to receive as input exclusively said control signal (CS), and apt to generate power supply signal (PWR_LED) for a corresponding LED illuminating apparatus, in a manner such that its lighting may range between zero and a maximum value (L_MAX) depending on the duty cycle of said control signal (CS).

2. The control system according to claim 1, wherein said minimum value

(P_MIN) is equal to about 10% and said maximum value (P_MAX) is equal to about 95%.

3. The control system according to claim 2, wherein said adjustment module (2) comprises a first microprocessor unit (3) equipped with output devices, apt to execute a software for generating a PWM adjustment signal (RS) having a given duty cycle value, corresponding to defined parameters.

4. The control system according to claim 3, wherein said adjustment module (2) further comprises interface means (6) for setting said parameters.

5. The control system according to claim 4, wherein said interface means (6) comprises input devices for allowing a manual adjustment of the duty cycle by a user.

6. The control system according to claim 4 or 5, wherein said interface means (6) comprises input channels for the connection of sensors for an automatic adjustment of the duty cycle on the basis of data detected by the sensors.

7. The control system according to claims 3 to 6, wherein said adjustment module (2) comprises one output stage (4), power-supplied by said PWM adjustment signal (RS), and which outputs said control signal (CS).

8. The control system according to claim 7, wherein said output stage (4) comprises a device (5) for stabilizing the output signal.

9. The control system according to claim 8, wherein said stabilizing device (5) is of push-pull configuration type.

10. The control system according to one of the preceding claims, wherein each drive module (11) comprises an input stage (12) having a first rectifier module (13) and a leveling module (14), said input stage (12) being power- supplied by said control signal (CS) and apt to output a voltage signal (V_PWR), substantially continuous and always greater than 0.

11. The control system according to claim 10, wherein said rectifier module (13) is a diode.

12. The control system according to claim 11, wherein said diode (13) is a Schottky diode.

13. The control system according to one of the claims 10 to 12, wherein said leveling module (14) is of capacitive type.

14. The control system according to one of the claims 10 to 13, wherein each drive module (11) comprises a second microprocessor unit (15) power- supplied by said voltage signal (V_PWR) and apt to receive as input said control signal (CS) to be acquired in a digital format.

15. The control system according to claim 14, wherein each drive module (11) comprises a translator stage (16), apt to receive as input said control signal (CS), to adjust its level prior to inputting it to said second microprocessor unit

0-

16. The control system according to claim 15, wherein said translator stage (16) comprises a voltage divider (17) adjusting the amplitude of the control signal

(CS) input to a subsequent filter (18).

17. The control system according to claim 16, wherein said voltage divider (17) is of resistive type and the filter (16) comprises a Schmitt trigger.

18. The control system according to one of the claims 14 to 17, wherein said second microprocessor unit (15) comprises software means (20) for filtering the acquired input signal.

19. The control system according to one of the claims 14 to 18, wherein said second microprocessor unit (15) comprises means (21) for processing the acquired input signal, apt to generate a PWM output signal (PWM-OUT) whose duty cycle ranges between 0% and 100% correspondingly to the duty cycle of the control signal (CS), calculated on the acquired signal.

20. The control system according to claim 19, wherein each drive module (11) comprises a constant-current generator (30), apt to receive as input said PWM output signal (PWM_OUT) and output a constant-current power supply signal (PWRJLED) for power-supplying said LED illuminating apparatus

(100), the value of said current being a function of the duty cycle of the PWM output signal (PWM-OUT).

21. A method for lighting control of LED illuminating apparatuses comprising the steps of: providing a low-voltage DC power supply voltage;

- generating, from said power supply voltage, a PWM-type control signal (CS) having a duty cycle settable between a minimum value (P_MIN) >

0% and a maximum value (P_MAX) < 100%, and

- generating a power supply signal (PWR-LED) for a LED illuminating apparatus (100) in a manner such that its lighting may range between zero and a maximum value (L_MAX) depending on the duty cycle of said control signal (CS).

22. The control method according to claim 21, wherein the duty cycle of the control signal (CS) ma range between 10% and 95%.

23. The control method according to claim 22, comprising a step of generating a PWM adjustment signal (RS) having a given duty cycle value, corresponding to defined parameters.

24. The control method according to claim 23, wherein said parameters are manually set by a user.

25. The control method according to claim 23 or 24, wherein said parameters are automatically set on the basis of data detected by sensors.

26. The control method according to one of the claims 21 to 25, further comprising a step of generating a PWM output signal (PWMjDUT) whose duty cycle ranges between 0% and 100% correspondingly to the duty cycle of the control signal (CS).

27. The control method according to claim 26, further comprising a step of generating a constant-current power supply signal (PWR_LED) for power- supplying said LED illuminating apparatus, the value of said current being a function of the duty cycle of the PWM output signal (PWM_OUT).