Methods and Apparatus for Operating Groups of High-Power Leds

• US 20080191642A1
• Filed: 04/07/2006
• Published: 08/14/2008
• Est. Priority Date: 04/08/2005
• Status: Active Grant

• Current Assignee: eldoLAB Holding B.V. (Acuity Brands, Inc.)
• Original Assignee: Wart HOG II Holding B.V.
• Inventors: Slot, Machiel, Cremer, Antonius Jacobus Maria
• Granted Patent: US 8,207,691 B2
• Time in Patent Office: Days
• US Class Current: 315/295
• CPC Class Codes: H05B 45/12 using optical feedback
• CPC Class Codes: H05B 45/18 using temperature feedback
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices
• CPC Class Codes: H05B 47/11 by determining the brightness or colour temperature of ambient light
• CPC Class Codes: H05B 47/16 by timing means
• CPC Class Codes: H05B 47/165 following a pre-assigned programmed sequence; Logic control [LC]
• CPC Class Codes: H05B 47/18 via data-bus transmission
• CPC Class Codes: H05B 47/19 via wireless transmission
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

The object of the invention is to implement an energy-efficient, compact and cost-effective solution for driving a number of high-power LED groups for lighting applications, by using a single switching power supply together with LEDs connected in series and/or in parallel and pulse width-controlled switches in parallel across the individually controllable LED groups. If the switch of an LED group is ON, the LED group will not light up. If the switch is in the OFF position, the full current of the power supply will pass through the corresponding LED group. Another aspect of the invention is the restriction within the drive protocol, according to which but a single switch is actuated at any one time within a particular time interval. This aspect guarantees a minimum time interval between each individual actuation event. Another aspect is the derating of the power supply in those phases where not a single LED group is ON. In the event of all the switches being closed (all LED groups OFF) the power supply can be derated (or turned off). A further aspect is the use of an elevated current setting of the power supply with the simultaneous restriction of the ON cycle by means of pulse width modulation. The power supply is set to the maximum instantaneous peak current of the LED, while maximum pulse width drive guarantees a maximum of the average LED current, cycle time being left over as a result, thus enabling more LEDs to be driven at a given supply voltage.

Claims

1. Method of driving, by means of single power supply, a number of high-power light-emitting diodes (LEDs), said number of LEDs being divided into two or more groups, each group being separately energizable, said method comprising:

a) energizing or de-energizing of a supply current from the power supply into a first one of the groups;

b) waiting during a predetermined wait time period; and

c) repeating step a) and b) for a second one of the groups.

2. Method according to claim 1, wherein the wait time period corresponds to a rise time or fall time of the power supply in the event of a single group being energized.

3. Method according to claim 1, wherein the de-energization of an energized group takes place in accordance with a desired average current in the energized group.

4. Method according to claim 1, further comprising the steps of:

d) determining prior to step a), of a sequential order by classifying the groups on the basis of a rising or falling desired average current; and

wherein step c) comprises;

c1) performing steps a) and b) in the energization sequential order for each of the groups to be energized.

5. Method according to claim 4, wherein, prior to d), among the groups a subset comprising groups is excluded from step d) and step c1);

and

c2) wherein it is determined, after energization according to c1), whether a remaining time up to a next de-energization of one of the groups energized at c1) is at least two wait time periods longer than a desired pulse duration of a group from the subset;

c3) if this is the case, the energizing of the relevant group from the subset and de-energization thereof after the desired pulse duration has elapsed; and

c4) the repeating of step c2) and c3) as long as not all the groups from the subset have been ON during the desired pulse duration.

6. Method according to claim 5, wherein the subset comprises the groups whose desired pulse duration is shorter than a total number of groups multiplied by the wait time period.

7. Method according to claim 5 wherein, in the event of one or more groups from the subset remaining after all the groups energized at c1) have been de-energized, the remaining groups are turned ON in accordance with step a) and b) for the desired pulse duration.

8. Method according to claim 1, wherein a magnitude of the supply current of the power supply is greater than a maximum peak current of a combination of the LEDs in the group.

9. Method according to claim 1, wherein a point of time of energizing and/or deenergizing of the groups is further determined by means of one or more modulation techniques among pulse width modulation (PWM), frequency modulation (FM), pulse code modulation (PCM) and time division modulation (TDM).

10. Method according to claim 1, further comprising:

a2) de-energizing of a group energized previously by means of step a) simultaneously with energizing by means of step a) of a subsequent one of the groups.

11. Method according to claim 10, further comprising

e) dividing of a cycle for energizing and de-energizing the groups into a number of equal portions, the number being equal to the number of groups;

a3) energizing of a first one of the groups at the start of one of the portions of the cycle; and

wherein step a2) comprises;

a4) energizing of a second one of the groups at the start of another portion of the cycle, the first group being de-energized simultaneously with energization of the second group.

12. Method according to claim 11, further comprising the steps of

determining a desired ON time in each cycle by means of one or more of the modulation techniques from the group;

turning ON, in accordance with steps a3) and a4), one or more of the groups during one or more portions of the cycle.

13. Method according to claim 12, further comprising the steps of:

turning one or more of the groups ON and OFF by means of steps a) and b) during one of the parts of the cycle, wherein each of the groups is assigned a different part of the cycle.

14. Method according to claim 1, further comprising the maintaining, during a proportionately longer period, one of the groups in an energized state over a period during which there is a low incidence of the group in question being energized for a proportionately shorter time.

15. Method according to claim 1, wherein the power supply comprises a switching power supply.

16. Method according to claim 15, wherein control of the switching power supply is synchronized with actuation of the groups.

17. Method according to claim 1, further comprising the transmission of a desired ON time, intensity or actuation time by means of a digital communications interface.

18. Method according to claim 17, wherein the intensity transmitted via the interface comprises logarithmic coding.

19. Method according to claim 1, further comprising the steps of:

measuring a light intensity by means of a photosensor; and

providing a feedback by using the measured light intensity to adjust the magnitude of the supply current of the power supply or to adjust an actuation time of a group.

20. Method according to claim 1, further comprising the step of actuating one or more of the groups as a function of a modulating signal.

21. Method according claim 1, wherein each group is connected to an actuation element for energizing the connected group of LEDs and each actuation element is connected to a control unit, and wherein the method further comprises:

controlling, according to any one of the preceding claims, at least one actuation element for energizing or de-energizing the group of LEDs connected to said actuation element.

22. Method according to claim 21, wherein the control unit is provided with a time control element, and control of an actuation element comprises actuation of but a single actuation element within the predetermined wait time period.

23. Method according to claim 22, wherein the said wait time period corresponds to a rise time or fall time of the power supply in the event of an LED group being actuated.

24. Method according to claim 1, further comprising the derating or switching off of the power supply to provide no supply current if each group of LEDs is de-energized.

25. Method according to claim 1, wherein an LED is fed a current which corresponds to the maximum peak current for the LED during a first period, said first period having a maximum duration such that the average current over a predetermined second period, which comprises said first period, does not exceed a maximum average current for the LED.

26. Supply unit for a number of high-power LEDs, said number of LEDs being divided into two or more groups, the supply unit comprising:

a power supply for feeding the LEDs,

a control input for receiving a desired intensity or actuation time for each group,

for each group an actuation element which is connected to the group for the purpose of energizing the group in question;

a control unit for driving the groups by means of the method according to claim 1.

27. Supply unit according to claim 26, wherein the control input comprises a digital communications interface.

28. Supply unit according to claim 26, wherein the power supply comprises a switching power supply.

29. Lighting unit comprising a number of high-power LEDs and the supply unit according to claim 26.

30. Lighting system comprising

at least two lighting units according to claim 29,

a central drive unit for driving the lighting units;

and

a preferably digital communications interface which is linked to the central drive unit and each of the lighting units for driving the lighting units from the central drive unit.

31. Lighting unit comprising one or more LEDs, a supply unit for feeding the LEDs and a network interface, wherein the network interface is provided with a first network connection for communicating with an upstream lighting unit in the network and a second network connection for communicating with a downstream lighting unit in the network.

32. Method of operating, using one or more power supplies, a number of high-power light-emitting diodes (LEDs), said number of LEDs being distributed over two or more groups, each group being separately energizable, wherein the time at which the groups are energized and/or de-energized is determined by means of one or more modulation techniques among pulse width modulation (PWM), frequency modulation (FM), pulse code modulation (PCM), and time division modulation (TDM).

33. Method of operating, using one or more power supplies, a number of high-power light-emitting diodes (LEDs), said number of LEDs being distributed over two or more groups, each group being separately energizable, wherein a previously energized group being deenergized simultaneously with a subsequent one of the groups being energized.

34. Method of operating, using one or more power supplies, a number of high-power light-emitting diodes (LEDs), said number of LEDs being distributed over two or more groups, each group being separately energizable, wherein a time jitter is applied at the instant when one or more of the groups is energized or de-energized.

35. Lighting system comprising a plurality of lighting units which are each provided with one or more LEDs and a central processing unit for driving the LEDs, wherein the central processing units are each provided with a memory for storing instructions for energizing and de-energizing the LEDs of the lighting unit in question, and wherein the lighting system comprises a communications network for transmitting, during operation, synchronization messages to one or more of the processing units, for the purpose of temporal matching of an energization and de-energization scenario of the LEDs of the lighting units.

36. Lighting system comprising one or more lighting units, wherein driving of the lighting units, for example via a network, takes place by means of instructions for presenting an operational status of a switch and/or an operational status of a display segment or display point.

37. Lighting system comprising one or more lighting units, wherein driving of the lighting units, for example via a network, takes place by means of instructions in a parametric script.