Title of Invention	"PARAMETERIZABLE DIGITAL PFC (POWER FACTOR CORRELATION)"
Abstract	A dimmable electronic ballast for at least one gas discharge lamp, particularly a fluorescent lamp, comprises a power factor correction (PFC), which is supplied with an input voltage, is controlled by a DC link voltage controller, and which serves to create a controlled DC link voltage, and comprises an inverter, which is supplied with the DC link voltage and which supplies the lamp. Dimming values for presetting a set lamp output are fed to the ballast. The DC link voltage controller has different properties at different applied dimming values.

Title of Invention

"PARAMETERIZABLE DIGITAL PFC (POWER FACTOR CORRELATION)"

Abstract

A dimmable electronic ballast for at least one gas discharge lamp, particularly a fluorescent lamp, comprises a power factor correction (PFC), which is supplied with an input voltage, is controlled by a DC link voltage controller, and which serves to create a controlled DC link voltage, and comprises an inverter, which is supplied with the DC link voltage and which supplies the lamp. Dimming values for presetting a set lamp output are fed to the ballast. The DC link voltage controller has different properties at different applied dimming values.

Full Text	Pararaeterizable digital PFC The present invention relates to operating devices for illumination means, in particular to an electronic ballast for at least one gas discharge lamp, in particular a fluorescent lamp. A high frequency filter connected to a voltage supply normally forms the input of electronic ballasts known in the state of the art, which high frequency filter is connected to a rectifier circuit. The supply voltage rectified by the rectifier circuit is delivered to a smoothing circuit for producing an intermediate circuit voltage (bus voltage) . An inverter fed with the intermediate circuit voltage finally produces a high-frequency a.c. voltage which is applied to the load circuit with the gas discharge lamp arranged therein. Among other things, operating with the high-frequency a.c. voltage has the consequence of an increase of the light yield of the lamp. Beyond this, by means of a change of the working frequency the possibility is provided of operating the lamp in different brightness steps (dimming values). The invention relates in particular to electronic ballasts having a smoothing circuit (Power Factor Correction, PFC) which provides the intermediate circuit voltage (bus voltage) delivered to the inverter. Normally the intermediate circuit voltage is thereby regulated to a predetermined desired value, which is effected by a regulation circuit arranged within the smoothing circuit. This compares the instant value of the intermediate circuit voltage, as actual value, with an internally predetermined desired value and correspondingly controls the energy take-up of the ballast and with that the value of the intermediate circuit voltage. A control of the energy take-up is normally effected with the aid of a controllable switching element. The switching processes of this switching element of the smoothing circuit can however lead to harmonics, which "back radiate" into the connected voltage supply. This means that voltage and current at the input of the ballast run apart from one another with regard to their phase, and a distortion occurs which leads to the production of harmonics which can be perceived by the connected mains. Since, however, the harmonics can have a disturbing effect in the mains, standards normally require that during a normal operation of the gas discharge lamp the harmonics produced by an electronic ballast only "back radiate" into the mains below a certain level. The smoothing circuit should therefore be so constituted that a running apart of the voltage and the current with regard to their phase is as far as possible avoided. An electronic ballast of the kind concerned is known from EP 1189490 Al. With this known electronic ballast the intermediate circuit voltage regulator has in different operating phases (preheating, ignition, normal operation) of the lamp different dynamic regulation characteristics. Through this it is to be ensured that the smoothing circuit, in the different operating phases of the lamp, has in each case optimal characteristics for the corresponding operating phase. The starting point of EP 1189490 Al is accordingly an electronic ballast that is operated with a constant supply voltage and with a constant power. There is thus involved a non-dimmable electronic ballast. The present invention has now set itself the object of increasing the flexibility of the smoothing circuit (PFC) such that it is suitable in particular with regard to the requirements made of a dimmable electronic ballast. This object is achieved in accordance with the invention by means of the features in the independent claims. The dependent claims further develop the central concept of the invention in particularly advantageous manner. In accordance with a first aspect of the present invention there is thus provided an electronic ballast for at least one gas discharge lamp, in particular a fluorescent lamp. The ballast is provided with an input voltage and has a smoothing circuit controlled by an intermediate circuit voltage regulator for producing a regulated DC intermediate circuit voltage, and an inverter stored with the DC intermediate circuit voltage. At least one lamp may be connected to the inverter. Unlike EP 1 189 490 Al, it is provided that external commands, such as dimming values, can be delivered to the ballast. The intermediate circuit regulator has characteristics which depend on the applied commands. Unlike EP I 189 490 Al, thus the characteristics of the intermediate circuit regulator are changed if necessary also within the same operating state (preheating, ignition, normal operation) in particular then if an external dimming value specification changes. The external commands are to this extent to be distinguished from the "internal" operating states, which according to EP 1 189 490 Al bring about different characteristics of the smoothing circuit. To the intermediate circuit regulator there may be allocated a controller, to which the external commands can be delivered and which transmits to the intermediate circuit regulator desired values with regard to the dynamic characteristics or other characteristics of the intermediate circuit regulation dependent on currently applied commands. Examples of these desired values are values regarding the intermediate circuit voltage, the time constants of the intermediate circuit regulator, as well as the permissible harmonics (THD), for example. A bidirectional communication can be effected between the controller and the intermediate circuit regulator, with which the intermediate circuit regulator transmits operating parameters of the smoothing circuit to the controller. These operating parameters may be for example the type and/or the level of the applied input voltage and/or of the intermediate circuit voltage. The controller may be software controlled. The controller may be connected to a memory, in which a comparison table (LUT - Look Up Table) is stored, which allocates corresponding desired values to defined external commands, for example dimming values, for the smoothing circuit. Alternatively the controller may determine the desired values for the intermediate circuit regulation depending on the external commands also via implemented functions. In addition or as an alternative to the dependence upon the commands delivered externally, the characteristics of the intermediate circuit regulator may also be adjustable depending on the kind and/or the level of the input voltage of the electronic ballast. In accordance with a further aspect of the present invention there is provided an electronic ballast (EVG) with which the intermediate circuit regulator receives desired values for the operation of the smoothing circuit from a software controlled controller. The adding of the software controlled controller thus makes possible a far more flexible configuration of the electronic ballast in comparison with the state of the art, which brings advantages in particular in the case of dimmable ballasts but also brings about advantages in the case of non-dimmable ballasts. Finally, the invention also relates to an electronic ballast for at least one gas discharge lamp, in particular fluorescent lamp, having a smoothing circuit (PFC), provided with an input voltage and controlled by an intermediate circuit voltage regulator, for the generation of a regulated DC intermediate circuit voltage, and an inverter fed with the DC intermediate circuit voltage, to the output of which a load circuit is connected in which at least one lamp can be placed, wherein - the intermediate circuit voltage regulator directly or indirectly detects the output power of the load circuit and the intermediate circuit voltage regulator has characteristics which depend on the output power of the load circuit. Further, the invention relates to luminaires having such ballasts, to methods for the operation of an electronic ballast, as well as a computer software programme product for supporting such methods. The invention finally also relates expressly to a microcontroller, as it can find employment with such methods or ballasts. Further features, advantages and characteristics of the present invention will now be explained in more detail with reference to the sole Figure of the accompanying drawings and with reference to a detailed embodiment: Fig. 1 thereby shows a schematic representation of an electronic ballast for a fluorescent lamp having a digital intermediate circuit voltage regulator. In the case of the schematic representation of the electronic ballast in accordance with the invention shown in Fig. 1, the representation of the rectifier circuit, which is normally formed by means of a lull bridge rectifier, is omitted. The rectified mains voltage is supplied to the smoothing circuit which is formed in the illustrated example by a step-up switching regulator, which is comprised of an inductance LI, a diode Dl, a storage capacitor Cl and a switching element in form of a field effect transistor SI controlled by the intermediate circuit voltage regulator 1. The intermediate circuit voltage Vz provided by the smoothing circuit is delivered to a load circuit 2 containing the inverter 7 as well as the load circuit 8 with the gas discharge lamp arranged therein, which lamp may be a fluorescent lamp. The operation of a step-up switching regulator is already known in principle and therefore shall be summarized in the following merely briefly. If the field effect transistor SI is conducting, the current in the inductance LI rises linearly. If the field effect transistor SI is blocked, however, the current discharges itself into the storage capacitor Cl so that there arises thereat an intermediate circuit voltage VE consisting of a d.c. voltage with ripple ("Modulation"). By means of a purposive control of the field effect transistor SI the energy take-up of the step-up converter and thus also the intermediate circuit voltage Vz at the storage capacitor Cl can be influenced. Thereby there arises the possibility of varying the energy take-up by a change of the switch-on period or the pulse duty ratio TON of the switch SI. In the following the intermediate circuit voltage regulator 1, which is constituted in the illustrated example as a digital regulator, will be explained in more detail. Via the input line 9, at first the instant value of the intermediate circuit voltage Vz is detected. As an alternative to this direct detection the intermediate circuit voltage Vz could however also be detected indirectly, for example via the input voltage. For the digital further processing this analog value of the intermediate circuit voltage V2 is converted to a digital value u(k) by an analog to digital converter 2. The conversion is effected in each clock cycle of the intermediate circuit voltage regulator 1, whereby the timing is predetermined by a central timing generator in form of a fixed frequency oscillator 3. The timing signals of the timing generator 3 are delivered, apart from to the analog to digital converter 4, also to a calculation unit 5, which forms the core of the digital intermediate circuit voltage regulator 1, as well as to a control block 6 for the control of the field effect transistor SI. The calculation unit 5 serves to calculate a control value y(k) in each clock cycle, which is transmitted to the control block 6. This converts the control value y(k) into a signal for operating the field effect transistor SI and thereby controls the switch-on time thereof. The switching through of the field effect transistor SI is thereby effected at a time point at which as far as possible no current flows through the diode Dl, since through this the switching losses are reduced. For this there serves a detection winding L2 which is coupled inductively with the inductance LI of the step-up switching regulator. If the field effect transistor Si blocks, then the current via the inductance LI falls continuously until it reaches the zero point at a certain time. This time is detected by the control block L6 with the aid of the detection winding L2 and the field effect transistor SI is again switched through with avoidance of switching losses. The control value y{k) thereby determines how long the field effect transistor SI is switched conducting. Through the time period the power take-up of the ballast and with that the height of the intermediate circuit voltage Vz provided is determined. There is however also the possibility, instead of the switch-on time of the switch SI, of changing the pulse duty ratio thereof in dependence upon the current control value y(k). The calculation of the control value y(k) is effected not only with regard to the instant actual value u(k) of the intermediate circuit voltage Vz but also with regard to the actual values as well as the control values in the previous clock cycles. Due to the digital characteristics the control value y(k) is calculated in accordance with a certain function, in the ideal case in accordance with an infinite series. This infinite series consists of series members; these, however, are broken off in the present example after the third member in order to keep the effort involved in calculating the control value within an acceptable region. This means that the current control value y(k) is calculated for example with reference to the following equation: y(k)=aly(k-1)+a2y(k-2)+blu(k)+b2 u(k-1)+b3 *u (k-2) Thereby, y(k-l) and y(k-2) designate the values of the control value in the previous and the pre-previous clock cycle, and u(k-l) and u(k-2) designate the actual values in the previous and pre-previous clock cycle. These individual values are weighted with the parameters al, a2 and bl to b3. As can be understood from the equation given above, the parameters taken into account for the weighting of the individual series members determine the dynamic behaviour of the intermediate circuit voltage regulator 1. Correspondingly, the intermediate circuit voltage regulator 1 can be adapted to different requirements by using different parameter sets for the control block 6 in the calculation of the control value y(k). For this purpose in accordance with the invention there is associated with the calculation unit 5 of the intermediate circuit regulator 1 an integrated controller 10 which communicates bidirectionally (see reference sign 11) with the calculation unit 5 of the intermediate time regulator 1. The controller 10 is connected to a memory 12. Via a digital interface 13 the controller 10 can receive digital commands, such as for example dimming value specifications, but also send for example status signals or error messages to a connected digital bus, for example with the DALI™ standard. The intermediate circuit regulator 1, the controller 10 with the interface 13 as well as the memory 12 can be constituted as an ASIC, for example. The software controlled controller 10 thus receives digital commands delivered externally via the interface 13. Furthermore the calculation unit 5 of the intermediate circuit regulator 1 can report back to the controller status information or operating parameters. Typical examples of this reporting back of the calculation unit 5 of the intermediate circuit regulator to the controller 10 are the type and/or the level of applied input voltage and the instant value of the intermediate circuit voltage Vz. Dependent upon this incoming information (external commands or return reports from the intermediate circuit regulator, output power of the load circuit having at least one lamp) the controller 10 can now transmit desired values for the operation to the calculation unit 5 of the intermediate circuit regulator 1. These desired values may concern for example the following parameters: Bus voltage desired value dependent upon input voltage, - Dynamic characteristics of the intermediate circuit regulator: The regulator coefficients must be changed in the case of small dimming values for adaptation to dynamics and stability requirements of the regulation. - For the improvement in the harmonic behaviour (THD) the TON values for the switch can be predetermined and optimized starting from the table. The modulation of the TON values of the switch is to be reduced with smaller input voltages. In accordance with the invention the intermediate circuit regulator I is thus adjusted via software depending upon externally delivered commands, such as for example dimming values or also depending upon return reports from intermediate circuit regulator. Further, the intermediate circuit regulator can be set for the output power of the load circuit containing the lamp. In this case the external specified value is thus for example a signal from a regulator for the power of the output circuit. This setting is particularly important with dimmable electronic ballasts, with which due to the changeable lamp power it can come in comparison with non-dimmable electronic ballasts to "static" load variations. It must therefore be possible that characteristics of the smoothing circuit can be changed also within an operating phase of the lamp, in particular during the operation of the lamp in the ignited condition. The maximum amplitude and the nature of the voltage supply (AC, DC) can in accordance with the invention be measured either directly (for example over the voltage divider and an AD converter). They can alternatively be detected indirectly via the following mathematical function: Vin = Vz x Toff / Ton +T0ff Toff is thereby the switch-off time period of the switch SI and correspondingly Ton the switch-on time period of this switch. The assignment of the specifications for the intermediate circuit regulation by the controller 10 can be carried out as illustrated in the Figure via a comparison table (Look-Up-Table), which is stored in the memory 12 and associates incoming commands via the digital interface, or return reports from the intermediate circuit regulation, with corresponding specifications for the intermediate circuit regulation. The controller 10 can, alternatively or in addition, also determine these specifications via implemented functions. As examples of the different specifications for the intermediate circuit regulation depending upon the kind and/or the input voltage the following scenarios can be mentioned: - By means of the detection of the maximum value of the applied a.c. voltage a particular geographical region can be determined upon (for example Europe or the USA) on. Via this indirect detection of the geographical field of application, in turn permissible THD limit values can be determined upon. The specifications for the intermediate circuit regulation can then correspondingly be effected such that the standards applying in the appropriate geographical region are observed. - The bus voltage desired value specification can be set depending on the height of the detected a.c. voltage, whereby there applies in principle the rule that the bus voltage is specified higher, the higher is the maximum amplitude of the applied a.c. voltage. - An operation of the intermediate circuit regulation can be predetermined, upon the application of an AC supply voltage, in which the switch-on time period Ton of the switch SI is constant. In contrast to this it can be provided upon the application of a d.c. voltage that the switch-on time period Ton of the switch SI is changed periodically ("Sweep Mode"). We claim 1. Electronic ballast for at least one gas discharge lamp, in particular fluorescent lamp, having a smoothing circuit (PFC) provided with an input voltage and controlled by an intermediate circuit voltage regulator for producing a regulated DC intermediate circuit voltage, and an inverter fed with the DC intermediate circuit voltage, to the output of which a load circuit is connected in which at least one lamp can be placed, wherein external commands are deliverable to the ballast, and - the intermediate circuit regulator has characteristics which depend upon the applied commands. 2. Ballast according to claim 1, characterised in that, it is a dimmable ballast to which external dimming values are deliverable. 3. Ballast according to claim 1 or 2, wherein a controller is associated with the intermediate circuit regulator, to which controller the external commands are deliverable and which transmits to the intermediate circuit regulator desired values regarding the dynamic characteristics dependent on the currently applied commands. 4. Ballast according to claim 2, wherein the controller transmits to the intermediate circuit regulator desired values regarding at least one of the intermediate circuit voltage, time constants of the intermediate circuit regulator and permissible harmonics (THD). 5. Ballast according to any of claims 2 or 3, wherein the intermediate circuit regulator transmits to the controller operating parameters of the smoothing circuit (PFC). 6. Ballast according to claim 4, in which the intermediate circuit regulator transmits to the controller information concerning the kind of the applied input voltage, the level of the applied input voltage and/or the intermediate circuit voltage. 7. Ballast according to any of claims 2 to 4, wherein the controller is software controlled. 8. Ballast according to any of claims 2 to 6, in which the controller is connected to a memory in which a comparison table is stored, which assigns desired values for the smoothing circuit to defined external commands. 9. Ballast in accordance with any preceding claim, in which the intermediate circuit regulator is constituted as a logic circuit. 10. Ballast in accordance with any preceding claim, in which the characteristics of the intermediate circuit regulator are adjustable in dependence upon the input voltage. 11. Ballast in accordance with any preceding claim, in which the external commands are information concerning the output power of the load circuit. 12. Electronic ballast for at least one gas discharge lamp, in particular fluorescent lamp, having a smoothing circuit (PFC) provided with an input voltage and controlled by an intermediate circuit voltage regulator for producing a regulated- DC intermediate circuit voltage, and an inverter fed with the DC intermediate circuit voltage, to the output of which a load circuit is connected in which at least one lamp can be placed, wherein - the intermediate circuit voltage regulator directly or indirectly detects the output power of the load circuit, and the intermediate circuit voltage regulator has characteristics which depend upon the output power of the load circuit. 13. Electronic ballast for at least one gas discharge lamp, in particular fluorescent lamp, having a smoothing circuit (PFC) provided with an input voltage and controlled by an intermediate circuit voltage regulator for producing a regulated DC intermediate circuit voltage, and an inverter fed with the DC intermediate circuit voltage, to the output of which a load circuit containing the lamp is connected, wherein - the intermediate circuit regulator is constituted as a logic circuit, and - a software controlled controller delivers desired values to the intermediate circuit regulator for the operation of the smoothing circuit. 14. Ballast according to claim 13, in which the controller transmits to the intermediate circuit regulator desired values dependent upon dimming values delivered to the controller. 15. Ballast according to claim 13 or 14, in which the controller transmits to intermediate circuit regulator desired values dependent upon the type and/or the level of the input voltage. 16. Ballast according to claim 15, in which the controller increases the desired value for the intermediate circuit voltage at higher input voltages. 17. Ballast according to any of claims 12 to 16, in which the intermediate circuit regulator transmits to the controller at least one operating value of the smoothing circuit. 18. Luminaire, having at least one gas discharge lamp and a ballast in accordance with any preceding claim. 19. Method for the operation of a dimmable electronic ballast for at least one gas discharge lamp, in particular fluorescent lamp, having a smoothing circuit (PFC) provided with an input voltage and controlled by an intermediate circuit voltage regulator for producing a regulated DC intermediate circuit voltage, and an inverter fed with the DC intermediate circuit voltage, which supplies the lamp, wherein - there are delivered to the ballast dimming values for the specification of a desired lamp power, and the intermediate circuit regulator has different characteristics with different applied dimming values. 20. Method for the operation of an electronic ballast for at least one gas discharge lamp, in particular fluorescent lamp, having a smoothing circuit (PFC) provided with an input voltage and controlled by an intermediate circuit voltage regulator for producing a regulated DC intermediate circuit voltage, and an inverter fed with the DC intermediate circuit voltage, which supplies the lamp, wherein - the intermediate circuit regulator is constituted as a logic circuit, and - a software controlled controller delivers to the intermediate circuit regulator desired values for the operation of the smoothing circuit. 21. Method for the operation of a dimmable electronic ballast for at least one gas discharge lamp, in particular fluorescent lamp, having a smoothing circuit (PFC) provided with an input voltage and controlled by an intermediate circuit voltage regulator for producing a regulated DC intermediate circuit voltage, and an inverter fed with the DC intermediate circuit voltage, which supplies the lamp, wherein the intermediate circuit regulator directly or indirectly detects the output power of at least one lamp, and characteristics of the intermediate circuit regulators are adjusted depending upon the output power. 22. Computer software programme product, that a method according to any of claims 19 to 21 when it runs on a computing device. 23. Microcontroller, characterised in that, it is constituted to support a method according to any of claims 19 to 21.

Full Text

Pararaeterizable digital PFC
The present invention relates to operating devices for illumination means, in particular to an electronic ballast for at least one gas discharge lamp, in particular a fluorescent lamp.
A high frequency filter connected to a voltage supply normally forms the input of electronic ballasts known in the state of the art, which high frequency filter is connected to a rectifier circuit. The supply voltage rectified by the rectifier circuit is delivered to a smoothing circuit for producing an intermediate circuit voltage (bus voltage) . An inverter fed with the intermediate circuit voltage finally produces a high-frequency a.c. voltage which is applied to the load circuit with the gas discharge lamp arranged therein. Among other things, operating with the high-frequency a.c. voltage has the consequence of an increase of the light yield of the lamp. Beyond this, by means of a change of the working frequency the possibility is provided of operating the lamp in different brightness steps (dimming values).
The invention relates in particular to electronic ballasts having a smoothing circuit (Power Factor Correction, PFC) which provides the intermediate circuit voltage (bus voltage) delivered to the inverter. Normally the intermediate circuit voltage is thereby regulated to a predetermined desired value, which is effected by a regulation circuit arranged within the smoothing circuit. This compares the instant value of the intermediate circuit voltage, as actual
value, with an internally predetermined desired value and correspondingly controls the energy take-up of the ballast and with that the value of the intermediate circuit voltage. A control of the energy take-up is normally effected with the aid of a controllable switching element.
The switching processes of this switching element of the smoothing circuit can however lead to harmonics, which "back radiate" into the connected voltage supply. This means that voltage and current at the input of the ballast run apart from one another with regard to their phase, and a distortion occurs which leads to the production of harmonics which can be perceived by the connected mains. Since, however, the harmonics can have a disturbing effect in the mains, standards normally require that during a normal operation of the gas discharge lamp the harmonics produced by an electronic ballast only "back radiate" into the mains below a certain level. The smoothing circuit should therefore be so constituted that a running apart of the voltage and the current with regard to their phase is as far as possible avoided.
An electronic ballast of the kind concerned is known from EP 1189490 Al. With this known electronic ballast the intermediate circuit voltage regulator has in different operating phases (preheating, ignition, normal operation) of the lamp different dynamic regulation characteristics. Through this it is to be ensured that the smoothing circuit, in the different operating phases of the lamp, has in each case optimal characteristics for the corresponding operating phase.
The starting point of EP 1189490 Al is accordingly an electronic ballast that is operated with a constant supply voltage and with a constant power. There is thus involved a non-dimmable electronic ballast.
The present invention has now set itself the object of increasing the flexibility of the smoothing circuit (PFC) such that it is suitable in particular with regard to the requirements made of a dimmable electronic ballast.
This object is achieved in accordance with the invention by means of the features in the independent claims. The dependent claims further develop the central concept of the invention in particularly advantageous manner.
In accordance with a first aspect of the present invention there is thus provided an electronic ballast for at least one gas discharge lamp, in particular a fluorescent lamp. The ballast is provided with an input voltage and has a smoothing circuit controlled by an intermediate circuit voltage regulator for producing a regulated DC intermediate circuit voltage, and an inverter stored with the DC intermediate circuit voltage. At least one lamp may be connected to the inverter. Unlike EP 1 189 490 Al, it is provided that external commands, such as dimming values, can be delivered to the ballast. The intermediate circuit regulator has characteristics which depend on the applied commands. Unlike EP I 189 490 Al, thus the characteristics of the intermediate circuit regulator
are changed if necessary also within the same operating state (preheating, ignition, normal operation) in particular then if an external dimming value specification changes.
The external commands are to this extent to be distinguished from the "internal" operating states, which according to EP 1 189 490 Al bring about different characteristics of the smoothing circuit.
To the intermediate circuit regulator there may be allocated a controller, to which the external commands can be delivered and which transmits to the intermediate circuit regulator desired values with regard to the dynamic characteristics or other characteristics of the intermediate circuit regulation dependent on currently applied commands.
Examples of these desired values are values regarding the intermediate circuit voltage, the time constants of the intermediate circuit regulator, as well as the permissible harmonics (THD), for example.
A bidirectional communication can be effected between the controller and the intermediate circuit regulator, with which the intermediate circuit regulator transmits operating parameters of the smoothing circuit to the controller. These operating parameters may be for example the type and/or the level of the applied input voltage and/or of the intermediate circuit voltage.
The controller may be software controlled.
The controller may be connected to a memory, in which a comparison table (LUT - Look Up Table) is stored, which allocates corresponding desired values to defined external commands, for example dimming values, for the smoothing circuit. Alternatively the controller may determine the desired values for the intermediate circuit regulation depending on the external commands also via implemented functions.
In addition or as an alternative to the dependence upon the commands delivered externally, the characteristics of the intermediate circuit regulator may also be adjustable depending on the kind and/or the level of the input voltage of the electronic ballast.
In accordance with a further aspect of the present invention there is provided an electronic ballast (EVG) with which the intermediate circuit regulator receives desired values for the operation of the smoothing circuit from a software controlled controller. The adding of the software controlled controller thus makes possible a far more flexible configuration of the electronic ballast in comparison with the state of the art, which brings advantages in particular in the case of dimmable ballasts but also brings about advantages in the case of non-dimmable ballasts.
Finally, the invention also relates to an electronic ballast for at least one gas discharge lamp, in particular fluorescent lamp, having a smoothing circuit (PFC), provided with an input voltage and controlled by an intermediate circuit voltage regulator, for the generation of a regulated DC intermediate circuit
voltage, and an inverter fed with the DC intermediate
circuit voltage, to the output of which a load circuit
is connected in which at least one lamp can be placed,
wherein
- the intermediate circuit voltage regulator directly
or indirectly detects the output power of the load
circuit and
the intermediate circuit voltage regulator has characteristics which depend on the output power of the load circuit.
Further, the invention relates to luminaires having such ballasts, to methods for the operation of an electronic ballast, as well as a computer software programme product for supporting such methods.
The invention finally also relates expressly to a microcontroller, as it can find employment with such methods or ballasts.
Further features, advantages and characteristics of the present invention will now be explained in more detail with reference to the sole Figure of the accompanying drawings and with reference to a detailed embodiment:
Fig. 1 thereby shows a schematic representation of an electronic ballast for a fluorescent lamp having a digital intermediate circuit voltage regulator.
In the case of the schematic representation of the electronic ballast in accordance with the invention shown in Fig. 1, the representation of the rectifier circuit, which is normally formed by means of a lull
bridge rectifier, is omitted. The rectified mains voltage is supplied to the smoothing circuit which is formed in the illustrated example by a step-up switching regulator, which is comprised of an inductance LI, a diode Dl, a storage capacitor Cl and a switching element in form of a field effect transistor SI controlled by the intermediate circuit voltage regulator 1. The intermediate circuit voltage Vz provided by the smoothing circuit is delivered to a load circuit 2 containing the inverter 7 as well as the load circuit 8 with the gas discharge lamp arranged therein, which lamp may be a fluorescent lamp.
The operation of a step-up switching regulator is already known in principle and therefore shall be summarized in the following merely briefly. If the field effect transistor SI is conducting, the current in the inductance LI rises linearly. If the field effect transistor SI is blocked, however, the current discharges itself into the storage capacitor Cl so that there arises thereat an intermediate circuit voltage VE consisting of a d.c. voltage with ripple ("Modulation"). By means of a purposive control of the field effect transistor SI the energy take-up of the step-up converter and thus also the intermediate circuit voltage Vz at the storage capacitor Cl can be influenced. Thereby there arises the possibility of varying the energy take-up by a change of the switch-on period or the pulse duty ratio TON of the switch SI.
In the following the intermediate circuit voltage regulator 1, which is constituted in the illustrated example as a digital regulator, will be explained in
more detail. Via the input line 9, at first the instant value of the intermediate circuit voltage Vz is detected. As an alternative to this direct detection the intermediate circuit voltage Vz could however also be detected indirectly, for example via the input voltage. For the digital further processing this analog value of the intermediate circuit voltage V2 is converted to a digital value u(k) by an analog to digital converter 2. The conversion is effected in each clock cycle of the intermediate circuit voltage regulator 1, whereby the timing is predetermined by a central timing generator in form of a fixed frequency oscillator 3. The timing signals of the timing generator 3 are delivered, apart from to the analog to digital converter 4, also to a calculation unit 5, which forms the core of the digital intermediate circuit voltage regulator 1, as well as to a control block 6 for the control of the field effect transistor SI.
The calculation unit 5 serves to calculate a control value y(k) in each clock cycle, which is transmitted to the control block 6. This converts the control value y(k) into a signal for operating the field effect transistor SI and thereby controls the switch-on time thereof. The switching through of the field effect transistor SI is thereby effected at a time point at which as far as possible no current flows through the diode Dl, since through this the switching losses are reduced. For this there serves a detection winding L2 which is coupled inductively with the inductance LI of the step-up switching regulator. If the field effect transistor Si blocks, then the current via the
inductance LI falls continuously until it reaches the zero point at a certain time. This time is detected by the control block L6 with the aid of the detection winding L2 and the field effect transistor SI is again switched through with avoidance of switching losses. The control value y{k) thereby determines how long the field effect transistor SI is switched conducting. Through the time period the power take-up of the ballast and with that the height of the intermediate circuit voltage Vz provided is determined. There is however also the possibility, instead of the switch-on time of the switch SI, of changing the pulse duty ratio thereof in dependence upon the current control value y(k).
The calculation of the control value y(k) is effected not only with regard to the instant actual value u(k) of the intermediate circuit voltage Vz but also with regard to the actual values as well as the control values in the previous clock cycles. Due to the digital characteristics the control value y(k) is calculated in accordance with a certain function, in the ideal case in accordance with an infinite series. This infinite series consists of series members; these, however, are broken off in the present example after the third member in order to keep the effort involved in calculating the control value within an acceptable region. This means that the current control value y(k) is calculated for example with reference to the following equation:
y(k)=al*y(k-1)+a2*y(k-2)+bl*u(k)+b2 *u(k-1)+b3 *u (k-2)
Thereby, y(k-l) and y(k-2) designate the values of the control value in the previous and the pre-previous clock cycle, and u(k-l) and u(k-2) designate the actual values in the previous and pre-previous clock cycle. These individual values are weighted with the parameters al, a2 and bl to b3.
As can be understood from the equation given above, the parameters taken into account for the weighting of the individual series members determine the dynamic behaviour of the intermediate circuit voltage regulator 1. Correspondingly, the intermediate circuit voltage regulator 1 can be adapted to different requirements by using different parameter sets for the control block 6 in the calculation of the control value y(k).
For this purpose in accordance with the invention there is associated with the calculation unit 5 of the intermediate circuit regulator 1 an integrated controller 10 which communicates bidirectionally (see reference sign 11) with the calculation unit 5 of the intermediate time regulator 1.
The controller 10 is connected to a memory 12. Via a digital interface 13 the controller 10 can receive digital commands, such as for example dimming value specifications, but also send for example status signals or error messages to a connected digital bus, for example with the DALI™ standard.
The intermediate circuit regulator 1, the controller 10 with the interface 13 as well as the memory 12 can be constituted as an ASIC, for example.
The software controlled controller 10 thus receives digital commands delivered externally via the interface 13. Furthermore the calculation unit 5 of the intermediate circuit regulator 1 can report back to the controller status information or operating parameters. Typical examples of this reporting back of the calculation unit 5 of the intermediate circuit regulator to the controller 10 are the type and/or the level of applied input voltage and the instant value of the intermediate circuit voltage Vz.
Dependent upon this incoming information (external commands or return reports from the intermediate circuit regulator, output power of the load circuit having at least one lamp) the controller 10 can now transmit desired values for the operation to the calculation unit 5 of the intermediate circuit regulator 1. These desired values may concern for example the following parameters:
Bus voltage desired value dependent upon input voltage,
- Dynamic characteristics of the intermediate circuit
regulator:
The regulator coefficients must be changed in the case
of small dimming values for adaptation to dynamics and
stability requirements of the regulation.
- For the improvement in the harmonic behaviour (THD) the TON values for the switch can be predetermined and optimized starting from the table. The modulation of the TON values of the switch is to be reduced with smaller input voltages.
In accordance with the invention the intermediate circuit regulator I is thus adjusted via software depending upon externally delivered commands, such as for example dimming values or also depending upon return reports from intermediate circuit regulator.
Further, the intermediate circuit regulator can be set for the output power of the load circuit containing the lamp. In this case the external specified value is thus for example a signal from a regulator for the power of the output circuit.
This setting is particularly important with dimmable electronic ballasts, with which due to the changeable lamp power it can come in comparison with non-dimmable electronic ballasts to "static" load variations. It must therefore be possible that characteristics of the smoothing circuit can be changed also within an operating phase of the lamp, in particular during the operation of the lamp in the ignited condition.
The maximum amplitude and the nature of the voltage supply (AC, DC) can in accordance with the invention be measured either directly (for example over the voltage divider and an AD converter). They can alternatively be detected indirectly via the following mathematical function:
Vin = Vz x Toff / Ton +T0ff
Toff is thereby the switch-off time period of the switch SI and correspondingly Ton the switch-on time period of this switch.
The assignment of the specifications for the intermediate circuit regulation by the controller 10 can be carried out as illustrated in the Figure via a comparison table (Look-Up-Table), which is stored in the memory 12 and associates incoming commands via the digital interface, or return reports from the intermediate circuit regulation, with corresponding specifications for the intermediate circuit regulation. The controller 10 can, alternatively or in addition, also determine these specifications via implemented functions.
As examples of the different specifications for the intermediate circuit regulation depending upon the kind and/or the input voltage the following scenarios can be mentioned:
- By means of the detection of the maximum value of the applied a.c. voltage a particular geographical region can be determined upon (for example Europe or the USA) on. Via this indirect detection of the geographical field of application, in turn permissible THD limit values can be determined upon. The specifications for the intermediate circuit regulation can then correspondingly be effected such that the standards

applying in the appropriate geographical region are observed.
- The bus voltage desired value specification can be
set depending on the height of the detected a.c.
voltage, whereby there applies in principle the rule
that the bus voltage is specified higher, the higher is
the maximum amplitude of the applied a.c. voltage.
- An operation of the intermediate circuit regulation
can be predetermined, upon the application of an AC
supply voltage, in which the switch-on time period Ton
of the switch SI is constant. In contrast to this it
can be provided upon the application of a d.c. voltage
that the switch-on time period Ton of the switch SI is
changed periodically ("Sweep Mode").

We claim
1. Electronic ballast for at least one gas discharge
lamp, in particular fluorescent lamp, having a
smoothing circuit (PFC) provided with an input voltage
and controlled by an intermediate circuit voltage
regulator for producing a regulated DC intermediate
circuit voltage, and an inverter fed with the DC
intermediate circuit voltage, to the output of which a
load circuit is connected in which at least one lamp
can be placed, wherein
external commands are deliverable to the ballast, and
- the intermediate circuit regulator has characteristics which depend upon the applied commands.
2. Ballast according to claim 1,
characterised in that,
it is a dimmable ballast to which external dimming values are deliverable.
3. Ballast according to claim 1 or 2,
wherein a controller is associated with the intermediate circuit regulator, to which controller the external commands are deliverable and which transmits to the intermediate circuit regulator desired values regarding the dynamic characteristics dependent on the currently applied commands.
4. Ballast according to claim 2,
wherein the controller transmits to the intermediate circuit regulator desired values regarding at least one of the intermediate circuit voltage, time constants of
the intermediate circuit regulator and permissible harmonics (THD).
5. Ballast according to any of claims 2 or 3,
wherein the intermediate circuit regulator transmits to the controller operating parameters of the smoothing circuit (PFC).
6. Ballast according to claim 4,
in which the intermediate circuit regulator transmits to the controller information concerning the kind of the applied input voltage, the level of the applied input voltage and/or the intermediate circuit voltage.
7. Ballast according to any of claims 2 to 4,
wherein
the controller is software controlled.
8. Ballast according to any of claims 2 to 6,
in which the controller is connected to a memory in which a comparison table is stored, which assigns desired values for the smoothing circuit to defined external commands.
9. Ballast in accordance with any preceding claim,
in which the intermediate circuit regulator is constituted as a logic circuit.
10. Ballast in accordance with any preceding claim,
in which the characteristics of the intermediate circuit regulator are adjustable in dependence upon the input voltage.
11. Ballast in accordance with any preceding claim,
in which the external commands are information concerning the output power of the load circuit.
12. Electronic ballast for at least one gas discharge
lamp, in particular fluorescent lamp, having a
smoothing circuit (PFC) provided with an input voltage
and controlled by an intermediate circuit voltage
regulator for producing a regulated- DC intermediate
circuit voltage, and an inverter fed with the DC
intermediate circuit voltage, to the output of which a
load circuit is connected in which at least one lamp
can be placed, wherein
- the intermediate circuit voltage regulator directly
or indirectly detects the output power of the load
circuit, and
the intermediate circuit voltage regulator has characteristics which depend upon the output power of the load circuit.
13. Electronic ballast for at least one gas discharge
lamp, in particular fluorescent lamp, having a
smoothing circuit (PFC) provided with an input voltage
and controlled by an intermediate circuit voltage
regulator for producing a regulated DC intermediate
circuit voltage, and an inverter fed with the DC
intermediate circuit voltage, to the output of which a
load circuit containing the lamp is connected, wherein
- the intermediate circuit regulator is constituted as
a logic circuit, and
- a software controlled controller delivers desired
values to the intermediate circuit regulator for the
operation of the smoothing circuit.
14. Ballast according to claim 13,
in which the controller transmits to the intermediate circuit regulator desired values dependent upon dimming values delivered to the controller.
15. Ballast according to claim 13 or 14,
in which the controller transmits to intermediate circuit regulator desired values dependent upon the type and/or the level of the input voltage.
16. Ballast according to claim 15,
in which the controller increases the desired value for the intermediate circuit voltage at higher input voltages.
17. Ballast according to any of claims 12 to 16,
in which the intermediate circuit regulator transmits to the controller at least one operating value of the smoothing circuit.
18. Luminaire, having at least one gas discharge lamp
and a ballast in accordance with any preceding claim.
19. Method for the operation of a dimmable electronic
ballast for at least one gas discharge lamp, in
particular fluorescent lamp, having a smoothing circuit
(PFC) provided with an input voltage and controlled by
an intermediate circuit voltage regulator for producing
a regulated DC intermediate circuit voltage, and an
inverter fed with the DC intermediate circuit voltage,
which supplies the lamp, wherein
- there are delivered to the ballast dimming values for
the specification of a desired lamp power, and
the intermediate circuit regulator has different characteristics with different applied dimming values.
20. Method for the operation of an electronic ballast
for at least one gas discharge lamp, in particular
fluorescent lamp, having a smoothing circuit (PFC)
provided with an input voltage and controlled by an
intermediate circuit voltage regulator for producing a
regulated DC intermediate circuit voltage, and an
inverter fed with the DC intermediate circuit voltage,
which supplies the lamp, wherein
- the intermediate circuit regulator is constituted as
a logic circuit, and
- a software controlled controller delivers to the
intermediate circuit regulator desired values for the
operation of the smoothing circuit.
21. Method for the operation of a dimmable electronic
ballast for at least one gas discharge lamp, in
particular fluorescent lamp, having a smoothing circuit
(PFC) provided with an input voltage and controlled by
an intermediate circuit voltage regulator for producing
a regulated DC intermediate circuit voltage, and an
inverter fed with the DC intermediate circuit voltage,
which supplies the lamp, wherein
the intermediate circuit regulator directly or indirectly detects the output power of at least one lamp, and
characteristics of the intermediate circuit regulators are adjusted depending upon the output power.
22. Computer software programme product,
that a method according to any of claims 19 to 21 when it runs on a computing device.
23. Microcontroller,
characterised in that,
it is constituted to support a method according to any of claims 19 to 21.

Documents:

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Patent Number

269301

Indian Patent Application Number

8151/DELNP/2007

PG Journal Number

42/2015

Publication Date

16-Oct-2015

Grant Date

14-Oct-2015

Date of Filing

22-Oct-2007

Name of Patentee

TRIDONICATCO GMBH & CO.KG

Applicant Address

FARBERGASSE 15, A-6851 DORNBIRN,AUSTRIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	MARENT, GUNTER	HASELWEG 1/4, A-6780 BARTHOLMABERG, AUSTRIA.

PCT International Classification Number

H05B 41/28

PCT International Application Number

PCT/EP2006/002791

PCT International Filing date

2006-03-27

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10 2005 018 775.7	2005-04-22	Germany