Drive Device for Illuminating Device, Illumination Device, Lighting System and Method for Controlling the Lighting System

Abstract

The present invention relates to a drive device for an illuminating load, an illumination device, a lighting system and a method for controlling the lighting system, wherein the drive device is connected between the illuminating load and a power adapter device for power supply, wherein the drive device comprises a control unit, wherein the control unit is configured to adjust the impedance of the drive device according to an electric output signal measured from the illuminating load so as to accordingly adjust the output voltage of the power adapter device and thereby to adjust the electric output signal for the illuminating load.

Claims

1. A drive device for an illumination device, connected between an illuminating load and a power adapter device for a power supply, wherein the drive device comprises a control unit, characterized in that the control unit is configured to adjust the impedance of the drive device according to the electric output signal measured from the illuminating load so as to adjust accordingly the output voltage of the power adapter device and thereby to adjust the electric output signal for the illuminating load.

2. The drive device according to claim 1, characterized in that the drive device further comprises a switch-mode DC/DC converter including a switch unit, wherein the control unit adjusts the impedance of the drive device by means of adjusting the conduction time of said switch unit.

3. The drive device according to claim 2, characterized in that said switch-mode DC/DC converter of the drive device acts as a shunt regulator which is connected in parallel to the illuminating load.

4. The drive device according to claim 3, characterized in that the control unit increases the conduction time of the switch unit so as to reduce the electric output signal for the illuminating load, and the control unit decreases the conduction time of the switch unit so as to increase the electric output signal for the illuminating load.

5. The drive device according to claim 1, characterized in that the drive device is operated in critical conduction mode.

6. The drive device of claim 2, characterized in that the switch-mode DC/DC converter including the switch unit is configured as boost circuit.

7. The drive device according to claim 5, characterized in that the switch-mode DC/DC converter including the switch unit is configured as boost circuit.

8. An illumination device, further comprising a LED illuminating load, characterized in that the illumination device comprises the drive device as claimed in claim 1.

9. A lighting system further comprising a power adapter device between power supply and said illumination device, characterized in that the lighting system comprises an illumination device claimed in claim 8, and characterized in that the power adapter device is configured as ECG electronic ballast, wherein the ECG electronic ballast follows the impedance of the drive device by varying its output voltage in response to the conduction time of the switch unit.

10. The lighting system according to claim 9, characterized in that the control unit is configured such that the power adapter device increases the output voltage when the electric output signal measured from the illuminating load is lower than a predetermined value, and the control unit is configured such that the power adapter device decreases the output voltage when the electric output signal measured from the illuminating load is higher than the predetermined value.

11. The lighting system according to claim 10, comprising an ECG acting as power adapter device which outputs high frequency alternating currents and voltages having constant RMS values, and which provides a first output current corresponding to a first output voltage and a second output current corresponding to a second output voltage smaller the first output voltage, characterized by that the relation between said second and said first output currents is smaller than the relation between said first and said second output voltages.

12. The lighting system according to claim 10, characterized in that the ECG electronic ballast outputs a high frequency alternating current electric signal having a constant RMS current value.

13. The lighting system according to claim 9, characterized in that the switching frequency of the drive device does not match with the switching frequency of the ECG acting as power adapter device.

14. The lighting system according to claim 12, characterized in that the switching frequency of the drive device does not match with the switching frequency of the ECG acting as power adapter device.

15. The lighting system according to claim 13, characterized in that the relation between the switching frequency of the drive device and the switching frequency of the ECG acting as power adapter device comprises the relation between two twin- or triple-digits prime factors.

16. The lighting system according to claim 13, characterized in that the relation between the switching frequency of the drive device and the switching frequency of the ECG acting as power adapter device comprises an irrational number.

17. The lighting system according to claim 13, characterized in that the switching frequency of the drive device is sweeping over time more than plus-minus 5% of its mean value.

18. The lighting system according to claim 13, characterized in that the switching frequency of the ECG acting as power adapter device is sweeping over time more than plus-minus 5% of its mean value.

19. A method for controlling the lighting system according to claim 9, characterized in that a) a control unit of the drive device detects an electric output signal from the illuminating load; b) the control unit adjusts conduction time of a switch unit of the drive device according to the electric output signal detected; c) the control unit adjusts an output voltage of the power adapter device for the power supply responsive to a variation of the conduction time of the switch unit; and d) the output voltage of the power adapter device is adjusted to coincide the predetermined range of the electric output signal measured from the illuminating load.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawing constitutes a part of the present description and is used to provide further understanding of the present invention. Such accompanying drawing illustrates the embodiment of the present invention and is used to describe the principles of the present invention together with the description. In the accompanying drawing the same components are represented by the same reference numbers. As shown in the drawing:

[0033] FIG. 1 shows a block diagram of structure of an illuminating device according to the present invention;

[0034] FIG. 2 shows a diagram of output signals of the drive device and ECG electronic ballast.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] As shown in FIG. 1, an illuminating device 100 according to the present invention is configured to comprise an ECG electronic ballast connected and adapted to a power supply, a rectifier structure 2 located downstream of the ECG electronic ballast as a power adapter device 1, a drive device 3 according to the present invention connected downstream of the rectifier structure 2, and a light source supplied by the drive device 3 in a controlled manner. In the present invention, the power supply for the ECG electronic ballast preferably can be an alternating current mains just as shown in the figure. Besides, in the present invention, the ECG electronic ballast is preferably configured to output a constant current electric signal, and the light source according to the present invention is preferably configured as an LED light source.

[0036] The drive device 3 according to the present invention is preferably configured to comprise a control unit 32 and a power stage 31 connected to this control unit 32. The power stage 31 may comprise any of the at least six possible switch-mode DC/DC converter topology circuit structures (e. g. Buck, Boost, Buckboost, Flyback, ‘Cuk, SEPIC, Zeta, Forward), preferably a boost circuit, and a switch unit, in which unit an electric switch component, e.g. MOSFET, is advantageously included, such that in the present example adjustment of the duty cycle for conduction time of the switch unit just means adjustment of the conduction time of the MOSFET. The control unit 32 can advantageously sense an LED load current of the illuminating device 100 as a feedback signal and correspondingly control and adjust the switch unit according to this feedback signal. In the present invention, the control unit 32 can be advantageously configured as, e.g., a microcontroller MCU, while any other dedicated controller can also be alternatively used here. The control unit 32 can advantageously form a positive feedback control loop 5 between an illuminating load 4 and the switch unit. This means that, in contrary to any PFC or standard DC/DC converting functionality incorporating all well known negative feedback control loops, here the control unit of the inventive drive device increases the conduction time of the switch unit so as to reduce the electric output signal for the illuminating load, and the control unit decreases the conduction time of the switch unit so as to enlarge the electric output signal for the illuminating load.

[0037] The control unit 32 adjusts the duty cycle of switching the power stage 31 according to the feedback signal obtained from output of the illuminating load, that is, adjusts a duty cycle so as to control an input impedance of the drive device 3. The power stage according to the present invention is preferably configured with a single stage topology structure, and a work frequency of the power stage is changed by changing its duty cycle, so as to further change the input impedance of the drive circuit. More general, the switching frequency of the power stage 31 is changed by varying the on-time of its switching element, e. g. MOSFET, or the off-time, or both. By that, the control method results in a PWM pulse width modulation.

[0038] In the present invention, the PWM control can be activated especially advantageously using zero-crossing detection (ZCD), and is subsequently closed according to the set activation time. The result of this is the critical-conduction mode called “CRM”. This operation mode of the drive device can alternatively be named boundary conduction mode (“BCM”) or transient conduction mode (“TCM”) and is characterized by that the off-time of the switch unit inside the power stage 31 isn't actively controlled, but simply ends at the time event of said ZCD, thus depends on the starting conditions, the energy states, and the values of the power stage's components only.

[0039] Preferably, the duty cycle of the power stage can be controlled in a way of PWM pulse width modulation. For better understanding of this control process, an example is listed in the following for illustration: in one time interval, the conduction time is fixed and unchanged for each positive feedback control cycle, while when it arrives at the next feedback control cycle, the control unit 32 will calculate a new conduction time according to the positive feedback control cycle, wherein the conduction time can be preferably set and changed with, for instance, software combined with the positive feedback control loop 5 until the illuminating device 100 has a stable LED output current.

[0040] A preferable control process of a lighting system comprising an illumination device having the drive device 3 in the present invention can be especially summarized in exemplification as including the content of the following steps, herein the power stage of the drive device 3 preferably is operated in a critical-conduction mode CRM, the control unit 32 carries out the zero-crossing detection, obtains a fixed conduction time for the switch unit within the power stage, senses an output current of the illuminating load, and adjusts the conduction time, i.e., PWM of the switch unit, using the positive feedback control loop 5. The action of the positive feedback control loop 5 can be understood in that the duty cycle for conduction time is reduced if the LED output current is not enough to reach a predetermined value, and the duty cycle for conduction time is increased if the LED output current exceeds the predetermined value. [0041] 1. The drive device 3 will ask for a rated power output, for example 150V/120 mA in the present example; [0042] 2. The control unit 32 senses an LED output current, and if the LED current is less than 120 mA, the control unit 32 will reduce the duty cycle for conduction time, and then it will increase the impedance of the drive device 3, thereby the constant current of the ECG electronic ballast will have a higher voltage output, accordingly the power stage 31 likewise will have more energy available such that the output power of the drive device will be increased; [0043] 3. The LED output current will be increased when the output power of the drive device is increased; [0044] 4. It returns to step 1 until the LED has an enough current (120 mA); and [0045] 5. If the LED output current is matched and stable, the output power of the drive device will be stabilized at a certain value, and the duty cycle for conduction time will stay at a stable value.

[0046] In addition, as it can be seen from FIG. 2 where it shows a diagram of output signals of the drive device and ECG electronic ballast, a person skilled in the art may derive that, as it is preferably proposed in the present invention, the switching frequency of the inventive drive device does not match with the switching frequency of the ECG serves as the power adapter device.

[0047] The above is merely preferred embodiments of the present invention but not to limit the present invention. For the person skilled in the art, the present invention may have various alterations and changes. Any alterations, equivalent substitutions, improvements, within the spirit and principle of the present invention, should be covered in the protection scope of the present invention.

LIST OF REFERENCE SIGNS

[0048] 1 power adapter device [0049] 2 rectifier structure [0050] 3 drive device [0051] 31 power stage or switch-mode DC/DC converter circuit comprising a switch unit [0052] 32 control unit [0053] 4 illuminating load [0054] 5 positive feedback control loop [0055] 100 illumination device