AU2006239628A1

AU2006239628A1 - Adjustable digital illuminating means output control

Info

Publication number: AU2006239628A1
Application number: AU2006239628A
Authority: AU
Inventors: Dirk Dworatzek; Markus Mayrhofer
Original assignee: Tridonicatco GmbH and Co KG
Current assignee: Tridonicatco GmbH and Co KG
Priority date: 2005-04-22
Filing date: 2006-03-27
Publication date: 2006-11-02
Anticipated expiration: 2026-03-27
Also published as: WO2006114176A1; CN101164388A; CN101164388B; EP1872631A1; DE102005018764A1; AU2006239628B2

Description

CERTIFICATION I, James Harry Sunderland, European Patent Attorney, of Jugerweg 20, D-85658 Egmating, Germany, hereby certify that I am well acquainted with the English and German Languages and that to the best of my knowledge and belief the following is a true translation made by me of the original text of the specification of International Application No. (PCT/EP2006/002792). J. Sunderland Dated: 22 September 2007 Adjustable digital illumination means power regulation The present invention relates generally to the digital regulation of the power of illumination means such as 5 can be applied by means of an electronic ballast (EVG) for gas discharge lamps, for example. In this context "digital regulation of the power of an illumination means" means that a control parameter is 10 generated in dependence upon a feedback parameter as an actual value as well as a desired value produced internally or externally, in accordance with an implemented regulation algorithm, which control parameter determines the power of the illumination 15 means with reference to a certain parameter. The feedback parameter may thereby for example be a parameter which represents the power of the illumination means, such as for example illumination 20 means voltage, illumination means current, or lighting power (measured, for example via photodiodes). Digital lamp regulations in the use of electronic ballasts (EVGs) for gas discharge lamps are known for 25 example from Fig. 1 of WO 02/43087 A2. There is known from EP 1 395 096 A2 a method for operating fluorescent lamps, as well as a ballast, with which the brightness of the fluorescent lamps is 30 adjusted to the desired value by variation of the switching frequency of an inverter switch. To prevent oscillations between different operating states in a critical dimming region, thereby the power take-up of 2 the fluorescent lamps is stabilized by an additional regulation loop. The present invention has given itself the object of 5 more flexibly configuring a digital illumination means power regulation. This object is achieved in accordance with the invention by the features of the independent claims. 10 The dependent claims further develop the central concept of the invention in particularly advantageous manner. In accordance with a first aspect of the invention 15 there is provided a method for the regulation of the power of an illumination means, in particular a gas discharge lamp. Thereby - a parameter representing the lamp power as well as at least one further parameter representing the state of 20 the illumination means are fed back, - the parameter representing the lamp power and/or the at least one further parameter are subjected to a threshold value discrimination, and - depending upon the result of the threshold value 25 discrimination there is effected regulation to the power parameter or to the further parameter as actual value. In case of regulation to the power parameter the 30 regulation may manifest other dynamic characteristics than for the case of regulation to the further parameter.

3 The at least one further parameter may represent the impedance of the illumination means. Regulation to the lamp impedance can be effected if 5 this exceeds a predetermined threshold value, and otherwise regulation is effected to the parameter representing the lamp power. A control value for the illumination means power can be 10 digitally determined on the basis of a desired value and the actual value. The invention also relates to a computer software programme product which supports a digital regulation 15 method in accordance with any preceding claim, when it runs on a computer device. The invention relates to a digital circuit which is configured for use as a digital controller in a method 20 in accordance with any preceding claim. The invention finally also concerns a digital regulation circuit for the power of an illumination means, having: 25 - an output for a control value indicating the power of the illumination means, - a first input for the feedback of a parameter representing the power of the illumination means, - at least one further input for a further parameter 30 representing a state of the illumination means, and - a discrimination and switching arrangement which is connected with the first or the second input and is configured for the purpose of subjecting the instant 4 value of the parameter applied at the input to a threshold value discrimination and, depending on the result of the discrimination, for switching the regulation system to regulation to the power parameter 5 or to regulation to the further parameter. Further features, advantages and characteristics of the present invention will now be described in more detail with reference to the Figures of the accompanying 10 drawings and with reference to an exemplary embodiment for the present invention. Fig. 1 thereby shows a schematic view of a digital illumination means power regulation in accordance with 15 the invention, Fig. 2 shows a more detailed view of Fig. 1 with regard to the algorithm implemented in the digital controller 1 and the coefficients stored in the system memory 6, 20 and Fig. 3 shows the different employed coefficients used for different applied dimming values. 25 In Fig. 1 there is schematically illustrated a digital circuit 1 for the regulation of the power of a connected illumination means. This digital circuit 1 is part of an operating device for the illumination means. The invention will be further explained referring to an 30 electronic ballast as an example of an operating device, and to a gas discharge lamp as an example of an illumination means. The invention can however also be 5 applied to other dimmable operating devices and illumination means. As control signal the digital circuit 1 produces 5 control signals for the two electronic switches (FETs) of an inverter 14, by means of which an applied supply d.c. voltage V2 (intermediate circuit voltage) can be converted into an a.c. voltage with an adjustable frequency, which is tapped off at the middle point of 10 the inverter 14. At this middle point of the inverter 14 there are provided in a known manner an RC circuit with an inductance 13 and a capacitance 18, to which a coupling capacitor 16 is connected in parallel with the lamp 17. It is symbolically illustrated in Fig. 1 that 15 the lamp 17 can be represented electrically as a resistor with a variable impedance. Different parameters of the lamp 17 can be fed back to the digital regulation circuit 1. As examples there are 20 shown a signal Sm, which represents the lamp impedance directly or indirectly. Spo 0 designates a signal representing the lamp power. The lamp power can for example be represented by the lamp voltage, the lamp current, or else by the lighting power (for example 25 detected by photodetectors) . The feedback signals SIMP, Spos delivered to the digital regulation circuit 1 thus represent actual values of the lamp operation and are digitized by AD converters 19, 20. The digitized actual value of the signal SpoW representing the lamp power is 30 compared with a first reference voltage Vref. This reference voltage represents an internal desired value. However, as illustrated in Figure 1 by a broken line, this desired value can however depend in particular on 6 a dimming value delivered externally. In any case the result of the comparison of actual value/desired value represents the regulation error e(k), which is delivered to a first digital controller 4. 5 In the regulator 4 there is implemented a regulation algorithm which depending on the delivered input signal produces a control signal 8 by means of which, with corresponding setting of an electronic switch 10 (FET, 10 etc.), an inverter driver 12 is controlled so that the output signal (control signal y(k)) of the regulator 4 indicates the working frequency of the inverter 14, and in turn the working frequency of the inverter 14 indicates the lamp power on the basis of the known 15 resonance curve of a gas discharge lamp 17. The control branch using an inverter 14, with which the control parameter is thus the frequency of the switches of the inverter 14, represents only an example. 20 However, for gas discharge lamps and in particular also for other illumination means (light-emitting diodes etc.) other control parameters are known, such as illumination means current etc., which can be used at any time in connection with the present invention. 25 The digital circuit 1 has a system controller 2 which processes a program stored as firmware. The system controller 2 is thereby connected to a system memory 6 and is clocked by a system timing generator (system 30 clock) 7. The system controller 2 is connected with an interface 3, to which dimming signals can be delivered from the 7 outside, for example from a bus line. The external dimming signals may thereby be analog and/or digital, in any case the interface 3 transmits digital values to the system controller 2 which represent the applied 5 dimming signals. The system controller 2 is for example firmware configured such that it adjusts the characteristics of the regulator 4 dependent upon the digital values 10 delivered by the interface 3, which thus represent the external dimming signals. In the system memory 6, for this purpose, characteristics of the regulator 4 can have certain 15 dimming values associated, so that upon application of a certain dimming value the system controller 2 can read out necessary characteristics from the computer memory 6 and can correspondingly adjust the regulator 4. 20 Thus, in summary, the regulator 4 has characteristics which on the system controller 2 can be adjusted in dependence upon dimming signals delivered externally. 25 As can be seen in Fig. 1, there can be provided a second regulator 5 for another feedback signal as actual value parameter, for example the lamp impedance SIMP. There are delivered to this regulator 5 values digitized by the AC converter 19, which thus represent 30 a signal which directly or indirectly represents the instant lamp impedance SIMP. Comparably to the regulator 4 also the regulator 5 produces a control signal 9 in accordance with the regulation algorithm currently 8 implemented therein, depending on a comparison of the actual impedance with a desired value for the impedance, which is represented in form of a voltage VREF2 5 Thus, different parameters, one of them representing the lamp power, can be fed back from the lamp to the regulation. For the power parameter or the further parameters there can in each case be made available a 10 desired value (see Vrefl, Vref2) , which desired value is then compared with the respective actual value so that the difference signal then can be delivered to the regulator. 15 The electronic switch 10 is controlled by means of a switch controller 11 and it thus selected whether the control signal 8 from the first digital controller 4 or the control signal 9 from the second regulator 5 should be put to use as actual input signal for the inverter 20 driver 12. The switch controller 11 may thereby adjust the electronic switch 10 depending on the instant value of the digitized signal SIMP representing the lamp 25 impedance. For this purpose the switch controller 11 is equipped with a threshold value discrimination function with regard to the applied signal. It can, for example, be provided that the switch 30 controller 11 only then controls the switch 10 for the use of the second regulator 5, when the currently applied signal SIMP representing the lamp impedance is above a predetermined threshold value. Thus, if signal 9 SIMP representing (in digital form) the lamp impedance directly or indirectly is above a predetermined threshold value, a regulation is effected with use of the lamp impedance SIMp as feedback parameter, whilst 5 otherwise, i.e. if the lamp impedance lies below a predetermined limit value, regulation takes place to the signal Spow, representing the lamp power, as feedback parameter and actual value. 10 Further, it can be provided that the characteristics of the second regulator 5 are adjustable by the system controller 2 depending on applied dimming values in comparable manner to the first regulator 4. 15 It is schematically illustrated in Fig. 2 that 6 coefficients for the regulation algorithm are stored in the system memory. The regulator 4 and if applicable also the regulator 5 generate an output signal y(k) dependent upon an input signal e(k) and if applicable 20 also the value of the input signal not only to the immediately present timing step K but also previous timing steps k-1, k-1, . . . Thus the control signal y(k) can be calculated using a 25 linear combination consisting of so-called regulation coefficients all, a2l,... of the regulation difference e(k) present for the current timing step K as well as a series of regulation differences for previous timing steps e(k-1), e(k-2), . 30 The linear combination can mathematically be represented for example as follows: 10 y(k) = a 1 - e(k) + a 2 e(k-1) + .. an e(k-n-1) + b. y(k) + b 2 y(k-1) + ... b,,- y(k-m-1) Where a and b are regulator coefficients. k is the current timing step (clock) m is the maximum number of values lying in the past 10 which are taken into account. The dynamic behaviour of the so-called regulation path, i.e. the illumination means together with the output circuit of the upstream electronics (for example 15 ballast) normally determines the choice of suitable regulation coefficients. These are thus so chosen that the closed regulation loop reacts rapidly but also stably to changes at the input or to perturbing variables. 20 In accordance with the present invention the characteristics of the digital implementation of the regulation algorithm are adjusted in dependence upon the currently set dimming value, which as explained 25 already above can be effected for example by the system controller 1, with use of the coefficients from the system memory 6. The characteristics of the regulator can alternatively 30 or in addition also be adjusted in dependence upon the current operating state of the illumination means which are in operation. In the case of use of an ignited gas discharge lamp these different operating states may for example be: 35 - shortly after ignition, - burned in, i.e. stabilized operation 11 - etc. An advantage of the digital implementation of the regulation loop consists in that these regulation 5 coefficients all, a21 etc. can be relatively easily changed by control signals of the system controller 1. With a comparable analog system a switchover between different hardware elements would be necessary for this purpose, which is complex and cost-intensive and 10 moreover affects the precision of the system. In accordance with a further aspect of the present invention the regulation characteristics can be changed in the case of certain boundary conditions, for example 15 at the operation of the illumination means at low temperatures and relatively slight dimming values, such that the kind of the chosen feedback parameter as actual value is changed. For example it can be provided that no longer the signal Spo 0 representing the lamp 20 power but a different measurement parameter, such as for example the impedance of the lamp SIMP, is used as feedback parameter, to ensure a stable operation of the lamp. In addition or as an alternative to this changeover concerning the feedback parameter, at the 25 same time the values and the number of regulation coefficients can also be changed. For this, as mentioned, the switchover to a second regulator 5 is advantageous if applicable. 30 The digital regulation circuit 1 can be implemented in hardware, software, as programmable logic, or an arbitrary combination thereof.

Claims

1. Method for the regulation of the power of an illumination means, in particular a gas discharge lamp, 5 in which - a parameter representing the lamp power and at least one further parameter representing the state of the illumination means are fed back, - the parameter representing the lamp power and/or the 10 at least one further parameter are subjected to a threshold value discrimination, and - depending on the result of the threshold value discrimination regulation is effected to the power parameter or to the further parameter as actual value. 15

2. Method according to claim 1, in which, in case of the regulation to the power parameter, the regulation has other dynamic characteristics than in the case of regulation to the 20 further parameter.

3. Method according to claim 1 or 2, in which the at least one further parameter represents the impedance of the illumination means. 25

4. Method in accordance with any preceding claim, in which regulation is effected to the lamp impedance when this exceeds a predetermined threshold value, and otherwise regulation is effected to the parameter 30 representing the lamp power.

5. Method in accordance with any preceding claim, 13 in which a control value for the illumination means power is determined digitally on the basis of a desired value and the actual value. 5

6. Method for digital power regulation of an illumination means, in which the characteristics of the power regulation in the operation of the illumination means are changed in dependence upon a detected state of the lamp. 10

7. Computer software programme product, which supports a digital regulation method in accordance with any preceding claim when it runs on a computer device. 15

8. Digital circuit which is configured for use as a digital controller in a method in accordance with any preceding claim. 20

9. Digital regulation circuit for the power of an illumination means, having: - an output for a control value indicating the power of the illumination means, - a first input for the feedback of a parameter 25 representing the power of the illumination means, - at least one further input for a further parameter representing a state of the illumination means, and - a discrimination and switching arrangement which is connected with the first or the second input and is 30 configured for subjecting the current value of the parameter applied at the input to a threshold value discrimination and, depending on the result of the discrimination, for switching the regulation system to 14 regulation to the power parameter or to regulation to the further parameter.

10. Circuit according to claim 9, 5 in which the at least one further parameter represents the impedance of the illumination means.

11. Circuit according to claim 9 or 10, which is configured to regulate to the lamp impedance, 10 if this exceeds a predetermined threshold value, and otherwise regulation to the parameter representing the lamp power is effected.

12. Circuit in accordance with any preceding claim, 15 which is implemented digitally.

13. Digital regulation circuit for the power of an illumination means, wherein the characteristics of the regulation circuit 20 are adjustable depending on the state of the illumination means in operation.