EP1872627B1 - Parameterizable digital pfc (power factor correlation) - Google Patents

Description

The present invention relates to control gear for lamps, in particular to an electronic ballast for at least one gas discharge lamp, in particular a fluorescent lamp.

The input from the prior art known electronic ballasts usually forms a connected to a power supply high-frequency filter, which is connected to a rectifier circuit. The supply voltage directed by the rectifier circuit is supplied to a smoothing circuit for generating an intermediate circuit voltage (bus voltage). An inverter fed with the intermediate circuit voltage finally generates a high-frequency alternating voltage, which is applied to the load circuit with the gas discharge lamp arranged therein. The operation with the high-frequency AC voltage, among other things, an increase in the luminous efficiency of the lamp result. By changing the operating frequency is also given the opportunity to operate the lamp in different levels of brightness (dimming).

The invention relates in particular to electronic ballasts with a smoothing circuit (English: Power Factor Correction, PFC), which the the Inverter supplied DC link voltage (bus voltage) provides. Usually, the intermediate circuit voltage is regulated to a predetermined desired value, which is effected by a control circuit arranged within the smoothing circuit. This compares the current value of the intermediate circuit voltage as an actual value with an internally specified value and accordingly controls the energy consumption of the ballast and thus the value of the intermediate circuit voltage. A control of the energy consumption is usually carried out with the aid of a controllable switching element.

However, the switching operations of this switching element of the smoothing circuit can lead to harmonics, which "back" in the connected power supply. This means that the voltage and current at the input of the ballast diverge in phase and distortion occurs, which leads to the generation of harmonics, which can be perceived by the connected network. However, since the harmonics in the network can have a disruptive effect, standards usually require that during normal operation of the gas discharge lamp the harmonics generated by an electronic ballast only "re-radiate" into the network below a certain level. The smoothing circuit should therefore be designed so that a divergence of the voltage and the current in terms of their phase is avoided as possible.

From the EP 1189490 A1 is a generic electronic ballast known. In this known electronic ballast, the intermediate circuit voltage controller in different operating phases (preheat, ignition, normal operation) of Lamp different dynamic control characteristics. This is to ensure that the smoothing circuit in the various phases of operation of the lamp in each case for the corresponding operating phase has optimal properties.

Starting point of the EP 1189490 A1 is therefore an electronic ballast that is operated with a constant supply voltage and constant power. So there is a non-dimmable electronic ballast.

The present invention has now set itself the task of extending the flexibility of the smoothing circuit (PFC) such that it is particularly fair in terms of requirements for a dimmable electronic ballast.

This object is achieved by the features in the independent claims. The dependent claims further form the central idea of the invention in a particularly advantageous manner.

According to a first aspect of the present invention, therefore, an electronic ballast is provided for at least one gas discharge lamp, in particular a fluorescent lamp. The ballast is supplied with an input voltage and has a smoothing circuit controlled by an intermediate circuit voltage regulator for generating a regulated DC link voltage and an inverter stored with the DC link voltage. At least one lamp can be connected to the inverter. Unlike the EP 1 189 490 A1 is provided that the ballast external commands such as dimming, can be supplied. The DC link controller has properties that depend on the applied commands. Unlike the EP 1 189 490 A1 If necessary, the properties of the DC link controller are also changed within the same operating state (preheating, ignition, normal operation), in particular if an external dimming value specification changes.

The external commands are to be distinguished from the "internal" operating states, according to the EP 1 189 490 A1 different properties of the smoothing circuit cause.

For this purpose, a controller can be assigned to the DC link controller, to which the external commands can be supplied and which transmits to the DC link controller dependent setpoints with respect to the dynamic characteristics or other properties of the DC link regulation.

Examples of these setpoints are, for example, values with regard to the DC link voltage, the time constants of the DC link controller and the permissible harmonics (THD).

A bidirectional communication can take place between the controller and the DC link controller in which the DC link controller transmits to the controller operating parameters of the smoothing circuit. These operating parameters can be, for example, the type and / or the level of the applied input voltage and / or the intermediate circuit voltage.

The controller can be software controlled.

The controller can be connected to a memory in which a look-up table (LUT) is stored, which assigns corresponding setpoints for the smoothing circuit to defined external commands, for example dimming values. Alternatively, the controller can also determine the setpoint values for the DC link control, depending on the external commands, via implemented functions.

In addition or as an alternative to the dependence on the externally supplied commands, the characteristics of the DC link regulator may also be adjustable depending on the type and / or the level of the input voltage of the electronic ballast.

According to a further aspect of the present invention, an electronic ballast (EVG) is provided, in which the DC link controller receives set values for the operation of the smoothing circuit from a software-controlled controller. The addition of the software-controlled controller thus allows a much more flexible design of the electronic ballast in comparison to the prior art, which brings advantages in particular in dimmable but also in non-dimmable ballasts.

Finally, the invention also relates to an electronic ballast according to claim 1.

The invention further relates to lights with such ballasts, to methods for operating an electronic ballast and a computer software program product to support such methods.

Finally, the invention also expressly relates to a microcontroller, as it can be used in such methods or ballasts.

• Die Fig. 1 zeigt dabei eine schematische Darstellung eines elektronischen Vorschaltgerätes für eine Leuchtstofflampe mit einem digitalen Zwischenkreisspannungs-Regler.

Further features, advantages and features of the present invention will now be explained in more detail with reference to the single figure of the attached drawings and to a detailed embodiment in which:

• The Fig. 1 shows a schematic representation of an electronic ballast for a fluorescent lamp with a digital DC link voltage controller.

At the in Fig. 1 shown schematic representation of the electronic ballast according to the invention has been on the representation of the rectifier circuit, which is usually formed by a full-bridge rectifier omitted. The rectified mains voltage is supplied to the smoothing circuit, which is formed in the illustrated example by a step-up converter, which consists of an inductor L1, a diode D1, a storage capacitor C1 and a controlled by the DC link voltage regulator 1 switching elements in the form of a field effect transistor S1. The intermediate circuit voltage V _z provided by the smoothing circuit is supplied to a load circuit 2 containing the inverter 7 and the load circuit 8 with the gas discharge lamp LA arranged therein, which can be a fluorescent lamp.

The operation of a boost converter is already known in principle and will therefore be summarized in the following only briefly. If the field effect transistor S1 is conductive, the current in the inductance L1 increases linearly. On the other hand blocks the field effect transistor S1, the current discharges into the storage capacitor C1, so that existing intermediate-circuit voltage V _z is generated at this one of a DC voltage with ripple ( "Modulation"). By selectively driving the field effect transistor S1, the energy consumption of the boost converter and thus also the voltage applied to the storage capacitor C1 intermediate circuit voltage V _z can be influenced. In this case, it is possible to vary the energy consumption by changing the switch-on time or the duty cycle T _{ON of} the switch S1.

In the following, the intermediate circuit voltage controller 1, which is designed as a digital controller in the example shown, will now be explained in more detail. The current value of the intermediate circuit voltage V _z is first detected via the input line 9. As an alternative to this direct detection, however, the intermediate circuit voltage V _{z could} also be detected indirectly, for example via the input voltage. For digital further processing, this analog value of the intermediate circuit voltage V _{z is converted} by an analog-to-digital converter 2 into a digital value u (k). The conversion takes place in each clock cycle of the intermediate circuit voltage regulator 1, wherein the clock is predetermined by a central clock in the form of a fixed-frequency oscillator 3. In addition to the analog-to-digital converter 4, the clock signals of the clock generator 3 are also supplied to a computing unit 5, which forms the core of the digital intermediate circuit voltage regulator 1, and to a control block 6 for driving the field-effect transistor S1.

The arithmetic 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 S1 and thus controls its turn-on time. The switching through of the field effect transistor S1 takes place at a time at which as no current flows through the diode D1, as a result, the switching losses are reduced. For this purpose, a detection winding L2, which is inductively coupled to the inductance L1 of the boost converter. If the field effect transistor S1 blocks, then the current across the inductance L1 drops continuously until it reaches zero at a certain point in time. This Time is detected by means of the detection winding L2 of the control block L6 and the field effect transistor S1, while avoiding switching losses again switched through. The control value y (k) specifies how long the field effect transistor S1 is turned on. By the duration of the power consumption of the ballast and thus the amount of the provided intermediate circuit voltage V _{z is} determined. However, it is also possible to change its duty cycle as a function of the current control value y (k) instead of the switch-on time of the switch S1.

The calculation of the control value y (k) takes place not only on the basis of the current actual value u (k) of the intermediate circuit voltage V _z , but also on the basis of the actual values and the control values in the previous clock cycles. Due to the digital properties, the control value y (k) is calculated according to a specific function, ideally after an infinite series. This infinite series consists of series members, which however in the present example are aborted after the third term in order to keep the effort for calculating the control value within an acceptable range. This means that the current control value y (k) is calculated, for example, using the following equation: $$\mathrm{y}\left(\mathrm{k}\right)\mathrm{=}\mathrm{a}\mathrm{1}\mathrm{*}\mathrm{y}\left(\mathrm{k}\mathrm{-}\mathrm{1}\right)+\mathrm{a}\mathrm{2}\mathrm{*}\mathrm{y}\left(\mathrm{k}\mathrm{-}\mathrm{2}\right)\mathrm{+}\mathrm{b}\mathrm{1}\mathrm{*}\mathrm{u}\left(\mathrm{k}\right)\mathrm{*}\mathrm{u}\left(\mathrm{k}\mathrm{-}\mathrm{1}\right)\mathrm{+}\mathrm{b}\mathrm{3}\mathrm{*}\mathrm{u}\left(\mathrm{k}\mathrm{-}\mathrm{2}\right)$$

Where y (k-1) and y (k-2) denote the values of the control value in the previous and previous clock cycles, respectively, while the values u (k-1) and u (k-2) represent the actual values in the previous and previous clock cycles, respectively ., designate a preceeding clock cycle. These individual values are weighted with the parameters al, a2 and b1 to b3, respectively.

As can be seen from the above equation, the parameters used to weight the individual row members determine the dynamic behavior of the DC link voltage regulator 1. Accordingly, by using different parameter sets for the control block 6 in calculating the control value y (k), the DC link voltage regulator 1 adapted to different requirements.

According to the invention, the arithmetic unit 5 of the DC link regulator 1 is assigned an integrated controller 10, which communicates bidirectionally with the arithmetic unit 5 of the intermediate-time regulator 1 (see reference numeral 11).

The controller 10 is connected to a memory 12. Via a digital interface 13, the controller 10 can receive digital commands, such as dimming value specifications, but also, for example, send status messages or error messages to a connected digital bus, for example with the DALI standard.

The DC link controller 1, the controller 10 with the interface 13 and the memory 12 may be embodied for example as an ASIC.

The software-controlled controller 10 thus receives externally supplied digital commands via the interface 13. Furthermore, the arithmetic unit 5 of the DC link regulator 1 can report back status information or operating parameters to it. Typical examples of this feedback from the arithmetic unit 5 of the DC link regulator to the controller 10 are the type and / or level of the applied input voltage and the current value of the intermediate circuit voltage V _z .

• Busspannungs-Sollwert abhängig von der Eingangsspannung,
• Dynamische Eigenschaften des Zwischenkreis-Reglers:
  • Die Reglerkoeffizienten müssen bei kleinen Dimmwerten zur Anpassung an Dynamik- und Stabilitätsanforderungen der Regelung verändert werden.
• Zur Verbesserung des Oberschwingungsverhaltens (THD) können die T_ON-Werte für den Schalter ausgehend von der Tabelle vorgegeben und optimiert werden. Die Modulation der T_ON-Werte des Schalters ist bei kleineren Eingangsspannungen zu verringern.

Depending on these incoming information (external commands, or feedback from the DC link regulator, output power of the at least one lamp having load circuit) can now the controller 10 of the arithmetic unit 5 of the DC link controller 1 transmit setpoints for the operation. These setpoints can, for example, affect the following parameters:

• Bus voltage setpoint dependent on the input voltage,
• Dynamic properties of the DC link controller:
  • The controller coefficients must be changed for small dimming values to match the dynamic and stability requirements of the control.
• To improve the harmonic response (THD), the T _ON values for the switch can be specified and optimized based on the table. The modulation of the T _ON values of the switch should be reduced for smaller input voltages.

Thus, according to the invention, the DC link controller 1 is set via software depending on externally supplied commands, such as dimming values or feedback from DC link controllers.

Furthermore, the DC link regulator can be set to the output power of the load circuit containing the lamp. The external default value is in this case, for example, a signal from a controller for the power of the output circuit.

This setting is particularly important for dimmable electronic ballasts, which may experience "static" load changes due to variable lamp power compared to non-dimmable electronic ballasts. Thus, it must be possible for properties of the smoothing circuit to be changed even in an operating phase, in particular during operation of the lamp in the ignited state.

The maximum amplitude as well as the nature of the power supply (AC, DC) can be measured according to the invention either directly (for example via the voltage divider and an AD converter). Alternatively, they can be detected indirectly using the following mathematical function: $${\mathrm{V}}_{\mathrm{in}}\mathrm{=}{\mathrm{V}}_{\mathrm{z}}\mathrm{x}{\mathrm{T}}_{\mathrm{off}}\mathrm{/}{\mathrm{T}}_{\mathrm{on}}\mathrm{+}{\mathrm{T}}_{\mathrm{off}}$$

T _off is the switch-off duration of the switch S1 and corresponding to T _on the switch-on of this switch.

The assignment of the specifications for the DC link control by the controller 10, as shown in the figure, via a look-up table, which is stored in the memory 12 and the incoming commands via the digital interface are ready or Feedback from the DC link control the corresponding specifications for the DC link control assigns. Alternatively or additionally, however, the controller 10 may also determine these specifications via implemented functions.

• Durch die Erfassung des Maximalwertes der anliegenden Wechselspannung kann auf einen bestimmten geographischen Bereich beschlossen werden (Beispielsweise Europa oder USA). Über diese indirekte Erfassung des geographischen Anwendungsbereichs kann wiederum auf zulässige THD-Grenzwerte geschlossen werden. Dementsprechend können dann die Vorgaben für die Zwischenkreis-Regelung derart erfolgen, dass die in dem entsprechenden geographischen Bereich herrschenden Normen eingehalten werden.
• Die Busspannungs-Sollwertvorgabe kann abhängig von der Höhe der erfassten Wechselspannung eingestellt werden, wobei grundsätzlich die Regel gilt, dass die Busspannung desto höher vorgegeben wird, je höher die maximale Amplitude der anliegenden Wechselspannung ist.
• Beim Anliegen einer AC-Versorgungsspannung kann ein Betrieb der Zwischenkreis-Regelung vorgegeben werden, bei denen die Einschaltzeitdauer T_on des Schalters S1 konstant ist. Im Gegensatz dazu kann beim Anliegen einer DC-Spannung vorgesehen sein, dass die Einschaltzeitdauer T_on des Schalters S1 periodisch verändert wird ("Sweep Mode").

The following scenarios should be mentioned as examples of the different requirements for the DC link control depending on the type and / or the input voltage:

• By recording the maximum value of the applied AC voltage can be decided on a specific geographical area (for example, Europe or USA). In turn, this indirect coverage of the geographic scope can be used to determine acceptable THD limits. Accordingly, then the specifications for the DC link control can be made such that the prevailing in the corresponding geographical area standards are met.
• The bus voltage setpoint specification can be set as a function of the magnitude of the detected alternating voltage, with the general rule that the bus voltage is set higher the higher the maximum amplitude of the applied alternating voltage.
• When applying an AC supply voltage, an operation of the DC link control can be specified, in which the ON time T _on the switch S1 is constant. In contrast, when applying a DC voltage may be provided that the On period T _on the switch S1 is changed periodically ("Sweep Mode").

Claims (22)

1. Electronic ballast for at least one gas discharge lamp, in particular a fluorescent lamp, with a smoothing circuit (PFC), to which an input voltage is supplied and which is controlled by an intermediate circuit voltage regulator (1), for generating a regulated DC intermediate circuit voltage (V_z) and an inverter (7), to which the DC intermediate circuit voltage is fed and to the output of which a load circuit (2) is connected, with it being possible for at least one lamp (LA) to be inserted into said circuit and for external commands to be supplied to the ballast, characterized in that

   - the intermediate circuit regulator has regulation properties which are dependent on the commands present.
2. Ballast according to Claim 1, characterized in that it is a dimmable ballast, to which external dimming values can be supplied.
3. Ballast according to Claim 1 or 2, wherein a controller is associated with the intermediate circuit regulator, with it being possible for the external commands to be supplied to said controller, and which controller transmits setpoint values with respect to the dynamic properties which are dependent on the commands present at that time to the intermediate circuit regulator.
4. Ballast according to Claim 2, wherein the controller (10) transmits setpoint values with respect to at least one of intermediate circuit voltage, time constant of the intermediate circuit regulator and permissible harmonics (THD) to the intermediate circuit regulator (1).
5. Ballast according to either of Claims 2 and 3, wherein the intermediate circuit regulator (1) transmits operational parameters of the smoothing circuit (PFC) to the controller (10).
6. Ballast according to Claim 4, in which the intermediate circuit regulator (1) transmits information with respect to the nature of input voltage present, the level of the input voltage present and/or the intermediate circuit voltage (V_z) to the controller (10).
7. Ballast according to Claims 2 to 4, wherein the controller (10) is software-controlled.
8. Ballast according to one of Claims 2 to 6, in which the controller (10) is connected to a memory (12), in which a look-up table is stored, which assigns setpoint values for the smoothing circuit to defined external commands.
9. Ballast according to one of the preceding claims, in which the intermediate circuit regulator (1) is in the form of a logic circuit.
10. Ballast according to one of the preceding claims, in which properties of the intermediate circuit regulator (1) are adjustable depending on the input voltage.
11. Ballast according to one of the preceding claims, in which the external commands are information with respect to the output power of the load circuit.
12. Ballast according to Claim 1, wherein

    - the intermediate circuit voltage regulator (1) detects the output power of the load circuit (2) directly or indirectly, and

    - the intermediate circuit voltage regulator (1) has properties which are dependent on the output power of the load circuit (2).
13. Ballast according to Claim 1, wherein

    - the intermediate circuit regulator (1) is in the form of a logic circuit, and

    - a software-controlled controller (10) supplies setpoint values for the operation of the smoothing circuit (PFC) to the intermediate circuit regulator.
14. Ballast according to Claim 13, in which the controller (10) transmits setpoint values depending on dimming values supplied to the controller to the intermediate circuit regulator (1).
15. Ballast according to Claim 13 or 14, in which the controller (10) transmits setpoint values depending on the nature and/or the level of the input voltage to the intermediate circuit regulator (1).
16. Ballast according to Claim 15, in which the controller (10) increases the setpoint value for the intermediate circuit voltage at higher input voltages.
17. Ballast according to one of Claims 12 to 16, in which the intermediate circuit regulator (1) transmits at least one operational value for the smoothing circuit (PFC) to the controller (10).
18. Luminaire, having at least one gas discharge lamp and a ballast according to one of the preceding claims.
19. Method for operating a dimmable electronic ballast for at least one gas discharge lamp, in particular florescent lamp, with a smoothing circuit (PFC), to which an input voltage is supplied and which is controlled by an intermediate circuit voltage regulator (1), for generating a regulated DC intermediate circuit voltage (V_z) and an inverter (7) to which the DC intermediate circuit voltage (1) is fed and which supplies the lamp (LA), wherein external commands are supplied to the ballast, characterized in that
    the intermediate circuit regulator (1) has regulation properties which are dependent on the commands present.
20. Method according to Claim 19, wherein

    - the intermediate circuit regulator (1) is in the form of a logic circuit, and

    - a software-controlled controller (10) supplies setpoint values for the operation of the smoothing circuit to the intermediate circuit regulator (1).
21. Method according to Claim 19, wherein

    - the intermediate circuit regulator (1) detects the output power of the at least one lamp (LA) directly or indirectly, and

    - properties of the intermediate circuit regulator (1) are adjusted depending on the output power.
22. Computer software program product, which executes a method according to one Claims 19 to 21 when it is run on a computation device.

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