EP0965251B1 - Method and device for controlling the operation of gas discharge lamps - Google Patents

Abstract

Method and device for controlling the operational performance of at least one gas discharge lamp (10). The control is effected with the aid of a controller (1) the proportional component of which is set in dependence upon an externally applied desired value (SOLL) of an operational parameter of the gas discharge lamp (10), whereby for low brightness desired values the proportional component of the controller (1) is set high, and for great brightness desired values of the gas discharge lamp (10) is set low. In this way it is possible to reliably fire the gas discharge lamp (10) even at low brightness values, without the appearance of a light flash, and at the same time to avoid instabilities in the case of high brightness values of the gas discharge lamp (10).

Description

The present invention relates to a method for regulating the operating behavior of Gas discharge lamps according to the preamble of claim 1 and a device for operating gas discharge lamps, in particular an electronic ballast, according to the preamble of claim 3.

Fig. 4 shows a known device according to the preamble of claim 3 Operation of gas discharge lamps. This is referred to as an electronic ballast The device initially comprises a rectifier arrangement 4, the one Converts AC line voltage into a rectified DC link voltage an inverter 5 is supplied. The inverter 5 usually has two switches connected in series between a positive supply voltage and ground, which are controlled alternately. The connection point between the two alternately driven switches, usually through MOS field effect transistors are connected to a load circuit which is essentially one Series resonance circuit with a coil 6 and a capacitor 7 and at least one Gas discharge lamp 10 includes. The gas discharge lamp 10 is a Coupling capacitor 8 connected to the series resonant circuit.

By alternately switching the two switches of the inverter 5 on and off the rectified intermediate circuit voltage supplied by the rectifier 4 in a high-frequency, clocked AC voltage is converted by the inverter 5 is delivered to the series resonance circuit. The gas discharge lamp 10 is ignited, by the frequency of the AC voltage supplied by the inverter 5 in the Proximity of the resonance frequency of the series resonance circuit with the coil 6 and that Capacitor 7 is shifted. In this case, the capacitor 7 applied voltage to a voltage surge, which leads to the ignition of the Gas discharge lamp 10 leads. To increase the life of the gas discharge lamp 4, a heating transformer 9A-C is also present in FIG Primary winding 9A connected to the series resonant circuit and essentially in parallel is connected to the gas discharge lamp 10 and its secondary windings 9B and 9C each connected in parallel to one of the two lamp filaments of the gas discharge lamp 10 are. The heating transformer 9A-C serves to preheat the lamp filaments Gas discharge lamp 10, wherein the heating voltage has a frequency that is clear is below or above the resonance frequency. In this way it is avoided that the gas discharge lamp 10 ignites with cold lamp filaments, thereby increasing the service life the gas discharge lamp 10 can be extended. As an alternative to the heating transformer 9A-C, a heating capacitor can also be connected in parallel with the gas discharge lamp 10 his. The use of a heating transformer with on the lamp filaments However, gas discharge lamp 10 connected secondary windings 9B and 9C have the advantage that the lamp filaments even after the gas discharge lamp 10 has been ignited energy can still be supplied.

The series resonance circuit with the coil 6 and the capacitor 7 and the Gas discharge lamp 10 are part of a controlled system 2, which in turn is part is a control loop, the behavior of which is determined by a controller 1. In particular 4 serves to regulate the brightness of the Gas discharge lamp 10 as a function of an externally specified dimming setpoint SHOULD, which is in a comparator 3 designed as an adder with an actual dimming value is compared, the resulting difference signal DIFF to controller 1 is supplied, which, depending on the control difference DIFF, a control signal STELL for generates a certain controlled variable of the controlled system 2. In particular, it can Control signal, the frequency and / or the pulse duty factor of the inverter 5 supplied clocked AC voltage concern. In the one shown in Fig. 4 electronic ballast is used to determine the actual brightness value Gas discharge lamp 10, a resistor 12 is provided in series with the lower Lamp filament of the gas discharge lamp 10 is switched. The on resistor 12 falling voltage is a direct measure of the over the gas discharge path Gas discharge lamp 10 flowing lamp current, which in turn directly with the Dimming degree or: the brightness of the gas discharge lamp 10 is related. As a result can the actual value of the degree of dimming of the gas discharge lamp 10 by determining the on the Resistor 12 falling voltage can be detected.

The basic structure of the ballast shown in FIG. 4 is, for example already known from DE 40 18 127 A1. It suggests the actual value of a Operating size of the electronic ballast to record the difference between to form the detected actual value and a predetermined target value and this difference value to a controller, which is a control value depending on the difference value for example for the AC voltage of the series resonance circuit Generated in this way, the lamp brightness of the over the Series resonance circuit controlled gas discharge lamp.

Because of the series resonance circuit with the coil 6 and the capacitor 7 present in the controlled system 2 shown in FIG. 4, the controlled system 2 essentially has a PT ₂ behavior, ie the controlled system 2 acts as a second-order delay element. It is known that controlled systems with delayed P behavior require a PI controller in order to ensure that the controlled system settles as quickly as possible and to counteract control loop instabilities that can arise due to the increasing tendency of the controlled system to oscillate. In this case, a PID controller is advantageously used, ie a controller which has both proportionally amplifying and integrating and differentiating properties. However, since such a PID controller has a very complex structure, a PI controller is generally used as controller 1 for the controlled system 2 shown in FIG. 4 for the sake of simplicity.

When the gas discharge lamp 10 is ignited, it increases with the aid of the actual value signal ACT detected lamp current suddenly, causing a flash of light in the gas discharge lamp 10 is generated, but should be avoided. It is therefore recommended that at a low brightness of the gas discharge lamp 10, i.e. with a high degree of dimming Regulator 1 is selected, the proportional portion of which is so high that ignition of the Gas discharge lamp 10 carried out even at low brightness values without flashing light can be. Such a high proportion, i.e. Gain of controller 1, would, however, with large lamp currents and with large lamp power, i.e. at low dimming, to instabilities of the control loop shown in FIG. 4 within the Run controlled system 2.

DE 43 31 952 A1 already describes a method for regulating the operating behavior of Gas discharge lamps are known, with one parameter being used Controller device is set depending on a predetermined setpoint. In particular, according to this document, one consisting of two blocks Controller device used, the one block the actual controller and the first block downstream second block forms a limiter that the output signal of the controller is limited to a maximum value. With the help of a detection circuit Actual value of the lamp power of the gas discharge lamp is detected and fed to the controller which also receives a predetermined setpoint and depends on the difference between the actual value and the setpoint a manipulated value for the duty cycle of a switching regulator electronic ballast generated. This manipulated variable is fed to the limiter, which limits the manipulated value with respect to an adjustable maximum value, the Maximum value of the limiter is set depending on the specified setpoint. In particular, when the setpoint is low, the maximum value of the limiter decreased. The use of a controller with a proportional component and thus However, related and previously explained problems do not arise from this document known.

EP-A1-0 605 052 describes a control method or an electronic ballast according to the preamble of claims 1 and 3, respectively. A control circuit compares that occurring in the load circuit of the electronic ballast Lamp current with a specifiable setpoint and generated depending on the difference a control signal for the between the actual value of the lamp current and the setpoint Frequency of the inverter. The control circuit has to avoid The control behavior of a PI controller.

DE-A1-44 12 510 describes a lighting control circuit with a Feedback loop with a switchable only during the start-up phase Response speed. The response speed depends on the Lamp spinning with the luminous efficiency of the corresponding gas discharge lamp is correlated, switched.

EP-A1-774 885 was published on 25/10/1996 with a Priority filed on 07/11/1995, and has been published on 21/05/1997. This document therefore belongs to the state of the art according to Article 54 (3) EPC.

EP-A1-774 885 discloses a regulator device with a regulation range (i.e. with a proportional component) that have a high Value when the lighting reading is low is at a lower value if the Illumination measured value is high, is switched.

In contrast to the present invention happens thus the switchover in EP-A1-774 885 depending on the measured light value.

The present invention has for its object a method and a Device for regulating the operating behavior of gas discharge lamps under To use a regulator with a proportional component, the regulation can be better adapted to the needs.

In particular, the gas discharge lamps should also have a high degree of dimming, i.e. low lamp brightness, can be reliably ignited without lower Degrees of dimming, i.e. larger lamp powers, instabilities occur.

The above object is achieved with respect to the method by a method Claim 1 and in terms of the device by an electronic ballast Claim 3 solved.

The subclaims each describe advantageous embodiments of the present Invention.

The above object is achieved in that the control loop Predefined setpoint, for example the dimming setpoint, is fed directly to the controller to adjust the properties of the controller depending on the setpoint. In particular, depending on the setpoint, the proportional component, i.e. the Gain factor of the controller set and adjusted. So is for a start from Gas discharge lamps with low brightness values, i.e. high degrees of dimming, high Proportional share, i.e. a high gain factor is necessary in order to To be able to ignite a gas discharge lamp without flashing light. With increasing brightness the Gas discharge lamp, i.e. with decreasing dimming level, the proportional part of the Controller reduced and in extreme cases even set to zero, in which case the Controller works as a pure I controller. By reducing the proportional part of the controller with increasing lamp brightness, instabilities in the control loop itself become large lamp powers or lamp currents avoided.

In general, according to the invention, in critical dimming areas in which a small Proportional share, i.e. a low gain factor, for instability of the control loop could lead to a proportional increase in the controller's proportion.

In general, according to the invention, the aim is, therefore, for each individual load case In addition to a specified dimming setpoint, a change from Operating state parameters of the control loop can be detected and specified select and set the ideal proportional component.

In addition to setting certain operating parameters of the controller, especially the Proportional part of the controller, it is dependent on the setpoint of the control loop also conceivable the corresponding operating parameters of the controller depending on certain Actual values of selected operating status parameters, e.g. the lamp current or the Lamp voltage, adjust. In addition to the proportional part of the controller, it is also possible according to the invention, other controller parameters, such as the integrating Proportion etc. to be adjusted depending on the specified setpoint.

The inventive method and electronic ballast takes place in particular wherever lighting with low brightness, i.e. high Degrees of dimming is desired, such as in movie theaters or the like, because According to the invention, ignition of gas discharge lamps even at a low level Degree of brightness without flash of light is reliably possible.

Fig. 1

zeigt ein erstes Ausführungsbeispiel des erfindungsgemäßen elektronischen Vorschaltgerätes,

Fig. 2a

und 2b zeigen Kurvenverläufe zur Einstellung des Proportionalanteils des Reglers abhängig von der Lampenhelligkeit,

Fig. 2c

und 2d zeigen Verläufe des Lampenwiderstandes bzw. des Lampenstromes abhängig von der Lampenhelligkeit,

Fig. 3

zeigt ein zweites Ausführungsbeispiel des erfindungsgemäßen elektronischen Vorschaltgerätes, und

Fig. 4

zeigt ein bekanntes elektronisches Vorschaltgerät mit einem PI-Regler zum Regeln des Betriebsverhaltens einer in einer Regelstrecke vorhandenen Gasentladungslampe.

The invention is described below with reference to the drawing using preferred exemplary embodiments.

Fig. 1

shows a first embodiment of the electronic ballast according to the invention,

Fig. 2a

and 2b show curves for setting the proportional portion of the controller depending on the lamp brightness,

Fig. 2c

and 2d show curves of the lamp resistance or the lamp current depending on the lamp brightness,

Fig. 3

shows a second embodiment of the electronic ballast according to the invention, and

Fig. 4

shows a known electronic ballast with a PI controller for controlling the operating behavior of a gas discharge lamp present in a controlled system.

Fig. 1 shows a first embodiment of the electronic according to the invention Ballast for operating gas discharge lamps.

The electronic ballast shown in FIG. 1 has - as already with reference to FIG. 4 explained - a control loop on a controller 1, a controlled system 2 and one Comparator 3 includes. The components corresponding to those shown in FIG. 4 Components are provided with identical reference numerals, with a repeated one Description of these components is omitted.

The embodiment of the electronic ballast according to the invention shown in FIG. 1 differs from the known electronic ballast shown in FIG. 4 mainly in the design of the regulator 1. Like the regulator shown in FIG. 4, the regulator 1 used in the electronic ballast according to the invention is also designed as a PI controller, which thus has a proportionally amplifying and integrating behavior. The PI controller 1 can advantageously be supplemented by a differentiating element, so that the PI controller becomes a PID controller which, although more complex, is more suitable for regulating the behavior of the controlled system which has a PT ₂ behavior is.

The invention is explained below using the dimming of the gas discharge lamp. However, it is quite conceivable to deviate from the regulation of the lamp brightness Basic idea of the invention, namely the adjustment of the operating parameters of the Controller depending on an externally specified setpoint, also on the control of apply other control variables.

The externally specified dimming setpoint can be from an external dimmer or for example, also from a light sensor that detects a specific one from the lamp 10 monitored illuminated workplace.

According to the invention, it is now proposed in particular that the proportional portion of the in Fig. 1 shown PI controller 1 depending on the externally specified dimming setpoint SHOULD be set. For this purpose, the PI controller 1 has an adjusting device 16 on, which could optionally be arranged outside of the PI controller 1. This The setting device 16 is supplied with the externally predetermined dimming setpoint SOLL. The Adjustment device 16 sets depending on the dimming setpoint TARGET Proportional proportion of the PI element 14 of the PI controller 1. The dimming setpoint SHOULD be compared in a comparator 3 with the actual dimming value ACTUAL, the result of which resulting difference value DIFF in addition to the P-element 14 and an I-element 13 of the PI controller 1 is supplied. The P control element 14 and the I control element 13 each generate depending a corresponding manipulated value from the difference value supplied, the thus generated control values are added on the output side by an adder 15 and as Control signal STELL of PI controller 1 are output.

The detection of the actual value of the lamp brightness 10, i.e. the degree of dimming in particular - as already explained with reference to FIG. 4 - by determining the on a Resistor 12 dropping voltage, which is in series with the lower lamp filament Gas discharge lamp 10 is connected to ground. The on this resistor 12 falling voltage is a measure of the over the gas discharge path of the Gas discharge lamp 10 flowing lamp current with increasing lamp brightness increases. Thus, by monitoring the voltage drop across resistor 12 the lamp brightness of the gas discharge lamp 10 or its degree of dimming can be detected. The setting of the P component within the PI controller 1 using the setting device 16 takes place depending on the predetermined dimming setpoint SHOULD as in Fig. 2a or 2b shown.

In order to reliably ignite the gas discharge lamp 10 even at low brightness values, i.e. at high dimming levels, without generating a flash of light in the To be able to ensure gas discharge lamp 10, the invention must Large proportion within the PI controller for such low brightness values to get voted. However, this high proportion or gain factor would even with large brightness values, i.e. low degrees of dimming are maintained, it could be due to the high flow in the controlled system 2 in this case Lamp current or the high lamp power to instabilities in the control loop. For this reason, with increasing lamp current, i.e. with increasing Lamp brightness, the proportional portion, i.e. the gain factor of the PI controller 1 reduced, the proportional component even being set to zero in the extreme case, so that in this case the PI controller 1 acts as a pure I controller. As shown in Fig. 2a, the Setting the proportional component of PI controller 1 depending on the specified one Dimming setpoint SHOULD be linear. However, it is also conceivable; the setting of the Proportional proportion depending on the lamp brightness or the dimming setpoint SHOULD in To make stages, as shown in Fig. 2b. In each of these cases, the Adjustment device 16 depends on the dimming setpoint SHOULD applied to it Proportional portion of the proportional control element 14 according to that in FIGS. 2a and 2b shown characteristic.

In this way it is possible, according to the invention, for every load case, i.e. for each Dimming value, select the ideal proportional portion or gain factor and adjust.

2c shows curves of the lamp resistance R _{L of} the lamp current I _L corresponding to the characteristics of FIGS. 2a and 2b, depending on the lamp brightness of the gas discharge lamp 10 or the predetermined dimming setpoint SHOULD. 2c and 2d in particular show that with increasing lamp brightness, the lamp current rises over the gas discharge path of the gas discharge lamp 10 and, accordingly, the resistance of the gas discharge lamp also drops with the desired lamp brightness.

Fig. 3 shows a second embodiment of the electronic according to the invention Ballast.

In the exemplary embodiment shown in FIG. 3, the PI controller 1 is divided into two control units 17 and 18. The first control unit 18 is controlled purely by software and is in particular in the form of a programmable or programmed microprocessor. The second control unit 17 is constructed purely in terms of hardware by combining known standard circuits and is in particular in the form of an application-specific integrated circuit (ASIC). The two control units 17 and 18 are connected to one another by a bidirectional transmission line 19. The first control unit 18 receives exclusively externally specified control information, such as, in particular, the externally specifiable dimming setpoint SHOULD. The second control unit 17, on the other hand, only receives internal operating state parameters, such as the lamp current i _L , which is also a measure of the degree of dimming or the lamp brightness of the gas discharge lamp 10. 3, the second control unit 17 receives the instantaneous value of the heating current i _H , which flows through the primary winding 9A of the heating transformer. For this purpose, a resistor 11 is connected between the primary winding 9A of the heating transformer and ground, so that the voltage drop across this resistor 11 is a measure of the heating current i _H flowing through the primary winding 9A. The second control unit 17 can be supplied with further internal operating state parameters, such as the actual values of the lamp voltage or the DC voltage supplied by the rectifier 4.

The operation of the split PI controller 1 shown in Fig. 3 is as follows. The second control unit 17 receives and stores the actual values of those applied to it Operating state parameters. The first control unit 18 then reads from the corresponding memory of the second control unit 17 the corresponding actual values of the previously mentioned internal operating state parameters and determined depending on the actual values of the internal values transmitted via the connecting line 19 Operating state parameters and the external applied to the first control unit 18 Control information, in particular corresponding to the dimming setpoint SHOULD Manipulated variable information. The first control unit 18 thus realizes the actual function of the PI controller 1. In particular, the functions of the in the first control unit 18 Setting device 16 of the P-link 14, the I-link 13 and the adder 15 implemented. In the first control unit 18 it is therefore dependent on it The dimming setpoint SHOULD be the P component within the PI controller function set. After generation of the manipulated variable information by the first control unit 18 The first control unit 18 transmits this control value information via the bidirectional Connection line 19 to the second control unit 17, which in turn due to this Control value information generates the actual control signal and the change in corresponding control variable, for example the frequency or the duty cycle of the from the inverter 5 supplied AC voltage.

The division of the PI controller 1 shown in FIG. 3 into a purely software-controlled one Control unit 18 and a purely hardware-based control unit 17 make it possible for on the one hand due to the software implementation of the first control unit 18 sufficient flexibility to adapt to possible circuit changes is guaranteed and, on the other hand, with the help of the second hardware Control unit 17 a sufficiently high speed due to their hardware Construction is ensured. The first control unit 18 is thus for the slow ones Control processes and the second control unit 17 responsible for the fast control processes. If the PI controller 1 as a whole were constructed purely in terms of hardware, it would not be sufficient Flexibility for changes in circuitry. On the other hand, that would be Processing speed of the PI controller 1 with a purely software-based one Design for fast regulation or control processes not fast enough. 3 solution shown thus provides the best possible compromise between a sufficient Flexibility on the one hand and a sufficiently high processing speed on the other hand.

Claims (12)

1. Method for controlling the operational performance of at least one gas discharge lamp (10), wherein a manipulated-variable value (STELL) for at least one specific controlled variable is generated with the aid of a controller (1), as a function of a differential value (DIFF) between a predetermined desired value (SOLL) and an actual value (IST) of a specific operating parameter (i_L) of the at least one gas discharge lamp (10), for the purpose of controlling the brightness of the at least one gas discharge lamp (10), and wherein the controller (1) has a proportional component (14) or amplification factor, characterised in that the desired value (SOLL) is fed directly to the controller (1), and in that the value of the proportional component (14) or the amplification factor of the controller (1) is set as a function of the desired value (SOLL) in such a way that the proportional component or amplification factor of the controller (1) is reduced for desired values (SOLL) which correspond to comparatively high brightness values and is increased for desired values (SOLL) which correspond to comparatively low brightness values.
2. Method according to claim 1, characterised in that the setting of the proportional component or the amplification factor of the controller (1) as a function of the desired value (SOLL) is effected in a linear manner or in steps.
3. Electronic ballast for operating at least one gas discharge lamp (10), having a controller device (1) which, as a function of a differential value (DIFF) between a predeterminable desired value (SOLL) and an actual value (IST) of an operating parameter (i_L) of the at least one gas discharge lamp (10), generates a manipulated-variable value (STELL) for at least one specific controlled variable for the purpose of controlling the brightness of the at least one gas discharge, lamp (10), in which case the controller device (1) has a proportional component (14) or amplification factor, and having a controlled system (2) which has a series-resonant circuit (6, 7) and also connected thereto the at least one gas discharge lamp (10), characterised in that the desired value (SOLL) is fed directly to the controller device (1), and in that the electronic ballast has setting means (16) for setting the proportional component (14) or the amplification factor of the controller device (1) as a function of the desired value (SOLL) in such a way that the proportional component or amplification factor of the controller (1) is reduced for desired values (SOLL) which correspond to comparatively high brightness values and is increased for desired values (SOLL) which correspond to comparatively low brightness values.
4. Electronic ballast according to claim 3, characterised in that the controller device (1) includes the setting means (16).
5. Electronic ballast according to claim 3 or 4, characterised by an actual-value acquisition device (12) which acquires the actual value (IST) of the brightness of the at least one gas discharge lamp (10) by determining the lamp current (i_L) or a variable corresponding to the lamp current (i_L).
6. Electronic ballast according to one of claims 3 to 5, characterised in that the setting means (16) set the proportional component or amplification factor of the controller device (1) as a function of the predeterminable desired value (SOLL) in a linear manner.
7. Electronic ballast according to one of claims 3 to 5, characterised in that the setting means (16) set the proportional component or amplification factor of the controller device (1) as a function of the predeterminable desired value (SOLL) in steps.
8. Electronic ballast according to one of claims 3 to 7, characterised in that the controller device (1) has the control response of a PI or PID controller.
9. Electronic ballast according to one of claims 3 to 8, characterised in that the controller device (1) corresponds to a combination of a first control unit (18) controlled purely in terms of software and a second control unit (17) connected thereto and constructed purely in terms of hardware, wherein external control information (SOLL) is fed to the first control unit (18) and internal operating-status information (i_L, i_H) is fed to the second control unit (17).
10. Electronic ballast according to claim 9, characterised in that the desired value (SOLL) is fed to the first control unit (18) and the actual value (IST) is fed to the second control unit (17), in that the first control unit (18) includes the setting means, (16), in that the first control unit (18) is connected to the second control unit (17) by way of a bidirectional connecting line (19), and in that the first control unit (18) determines the manipulated-variable value information, which corresponds to the manipulated-variable value (STELL), as a function of the external control information fed to it with the desired value (SOLL) and the internal operating-status information (i_L, i_H) received from the second control unit (17) by way of the connecting line (19) with the actual value (IST), and transmits this information to the second control unit (17) which, as a function of this manipulated-variable value information, generates a manipulated-variable value signal (STELL) for the controlled variable.
11. Electronic ballast according to claim 9 or 10, characterised in that the first control unit (18) is a programmable microprocessor and the second control unit (17) is an application-specific integrated circuit (ASIC).
12. Electronic ballast according to one of claims 3 to 11, characterised in that the controlled variable relates to the frequency and/or the pulse duty factor of an alternating operating voltage applied to the series-resonant circuit (6, 7).

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