EP2138015B1 - Circuit configuration for generating an auxiliary voltage and for operating at least one discharge lamp - Google Patents

Abstract

A circuit arrangement for operating at least one discharge lamp may include: a first and a second input terminal for connecting a supply voltage; an inverter, which includes at least one first switch and one second switch, which are coupled in series between the first and the second input terminal and between which a bridge center point is defined; a drive circuit for at least the first switch and the second switch with an input for receiving a control signal; an apparatus for generating an auxiliary voltage. The apparatus may include: a first capacitor; a terminal for the provision of the auxiliary voltage, which terminal is coupled to a reference potential via the first capacitor; a two-state controller with a first input to which the control signal in inverted form is coupled, a second input, which is coupled to the terminal for the provision of the auxiliary voltage, and an output; a switch—with a control electrode, a working electrode and a reference electrode, the control electrode being coupled to the output of the two-state controller, the working electrode being coupled to the terminal for the provision of the auxiliary voltage; and a nonreactive resistor; wherein the apparatus for generating the auxiliary voltage furthermore includes a transformer with a primary winding and a secondary winding, the transformer being coupled to the first and the second input terminal, the terminal for the provision of the auxiliary voltage and the switch-in such a way that a current through the switch results in a current through the primary winding, in a current through the secondary winding and therefore in charging of the first capacitor.

Description

Technical area

The present invention relates to a circuit arrangement for operating at least one discharge lamp having a first and a second input terminal for connecting a supply voltage, an inverter comprising at least a first and a second switch, which are coupled in series between the first and the second input terminal and between them a bridge center is defined, a drive circuit for at least the first and the second switch with an input for receiving a control signal and a device for generating an auxiliary voltage. In this case, the auxiliary voltage comprises a first capacitor, a terminal for providing the auxiliary voltage, which is coupled via the first capacitor to a reference potential, a two-position controller having a first input to which the control signal is coupled in an inverted form, a second input which is connected to the Coupled to provide the auxiliary voltage, and an output, a switch having a control, a working and a reference electrode, wherein the control electrode is coupled to the output of the two-position controller, wherein the working electrode is coupled to the terminal for providing the auxiliary voltage, and an ohmic resistance.

State of the art

From the DE 10 2005 041 076 A1 an electronic control gear is known, the auxiliary power supply in standby has a different internal resistance as in normal operation, to reduce the power loss during normal operation.

From the EP 1 231 821 A1 is an electronic control gear is known, which has a buck converter as auxiliary power supply.

From the EP 0 439 240 A2 An electronic operating device with an auxiliary voltage supply is known, which can either be fed via a transistor from the supply network or via an auxiliary winding of an existing boost converter choke.

A generic, known from the prior art circuit arrangement is to illustrate the problem underlying the invention in Fig. 1 shown. It shows a section of an electronic ballast, which is usually connected via a filter circuit, a rectifier circuit, a PFC (Power Factor Correction) circuit with an AC mains. It is powered by the so-called intermediate circuit voltage U _ZW , which is stabilized by means of a capacitor C _UZW . The intermediate circuit _voltage U _{ZW in the} present case feeds a half-bridge circuit comprising a first switch S1 and a second switch S2, and is usually of the order of 320 V. The half-bridge center HM is coupled via a lamp inductor L to a discharge lamp La, which is a firing capacitor C ₁ is connected in parallel, and which is coupled via a coupling capacitor C _K to a reference potential. It has a controller 10, which can be digitally controlled via an interface 12, for example according to the DALI standard. In standby mode, ie with the inverter switched off, the controller 10 requires a power supply of about 2 mA, in normal operation, ie when the inverter is in operation, a power supply of about 30 mA. An "on" signal at the interface 12 causes a half-bridge driver circuit 14 to start operating and to drive the switches S1 and S2 in accordance with a default.

The interface evaluation made by the controller 10 must also be in the "off" state of the output circuit 16, the inverter with the switches S1 and S2, the lamp inductor L and the lamp La including wiring, be ready for use at any time, for example, to receive a new "on" command and evaluate. For this it is necessary to supply the controller 10 always in the "off" state with a voltage. Thus, to always keep the interface 12 in standby, standby losses occur, which are generally undesirable.

The known solution derives the standby current required for the controller 10 via an ohmic resistor R _F and a two-point controller SSD controlled via a switch Q _ISS directly from the intermediate _{circuit voltage} U _ZW . In this case, the two-point controller SSD, the control signal, which serves to turn on the half-bridge driver 14, supplied in an inverted form, so that the two-position controller starts its operation when the half-bridge driver 14 is turned off. As a result, the controller 10 is no longer supplied with voltage via its operating supply circuit 18, the operating supply circuit comprising, by way of example, a capacitor C2 and two diodes D1 and D2, but via an auxiliary voltage V _CC provided to a capacitor C _VCC . An input 20 of the two-point controller SSD is used to measure the voltage V _CC . In the Fig. 1 drawn current source ISS can be realized by an integrated circuit, in a very simplified form, however, also by an ohmic resistance. According to Fig. 1 the standby supply on the capacitor C _{VCC is} only active when the output circuit is switched off via the interface 12. The two-point controller SSD keeps the auxiliary voltage Vcc over the switched with the switch Q _ISS power source ISS constant, by depending on the power consumption and height of the intermediate circuit voltage U _ZW varies the duty cycle. The standby power loss in this solution is about 0.5 to 1 W. The required two-level current source is already integrated in some commercial half-bridge drivers in an advantageous manner.

A disadvantage of this known solution is still undesirably high power loss in standby mode.

Another disadvantage of this known solution is that an additional auxiliary voltage generation for normal "on" operation is necessary. In the present case, this is realized by the operating supply circuit 18, which is based on the principle of deriving this voltage capacitively from the output circuit 16 at a suitable location.

Another circuit arrangement, not shown, solves the problem of an additional auxiliary voltage supply for the normal "on" operation in that the circuit arrangement comprises a step-down converter which generates a regulated auxiliary voltage. It allows auxiliary voltage generation not only in standby mode but also in normal "on" operation, whereby standby power losses of 0.3 to 0.8 W can be achieved. The disadvantage is that such a circuit arrangement is relatively expensive and requires a large number of components.

Presentation of the invention

The object of the present invention is therefore to develop a generic circuit arrangement such that they basically allow a lower standby power loss with cost-effective implementation.

This object is achieved by a circuit arrangement having the features of patent claim 1.

The present invention is based on the finding that the standby power loss can be significantly reduced by using a transformer. In this case, the transformer is used as a flux converter, wherein the primary winding is coupled to the switch Q _ISS , that a current through the primary winding leads to a change in the transmission ratio of the transformer current through the secondary winding, the secondary winding coupled to the capacitor C _VCC is that a current through the secondary winding leads to a charging of the capacitor C _VCC . Through the use of a transformer, the current drawn from the intermediate _{circuit voltage} U _ZW drops by the factor of the transmission ratio compared with the in Fig. 1 shown circuit without transformer. Thus, the power taken from the mains also decreases by the factor of the transformation ratio of the transformer. At a typical transmission ratio of 10, a standby power loss of approximately 0.05 to 0.10 W can be achieved.

In a preferred embodiment, the primary winding and the ohmic resistor are connected in series, and this series circuit is coupled between the reference electrode of the switch and the first input terminal. In this case, the device for generating the auxiliary voltage further comprises a first diode which is connected in parallel to the series circuit of the primary winding and the ohmic resistor and is arranged so that it allows a free-running of the current through the primary winding, and a second diode which is connected to the secondary winding in Series is connected, wherein the series circuit of secondary winding and second diode is coupled between the reference potential and the terminal for providing the auxiliary voltage. Thus, the standby power loss can be significantly reduced by two additional diodes and a transformer alone. The first and the second diode are preferably designed as fast recovery diodes.

Preferably, a current source is coupled between the working electrode of the switch and the terminal for providing the auxiliary voltage. This is preferably realized particularly cost-effective by an ohmic resistance.

A further category of embodiments solves the second problem mentioned above in connection with the prior art: namely, it offers the advantage that it not only enables a reduction of the standby power loss, but also a continuous auxiliary voltage generation, ie an auxiliary voltage for the supply of the controller also in normal operation of the output circuit. This eliminates the operating supply circuit discussed in connection with the prior art. These embodiments characterized in that the means for generating an auxiliary voltage further comprises a second capacitor having a first and a second terminal, wherein the capacitor is coupled to the bridge center and the primary winding such that a capacitive displacement current can flow through the primary winding. Since the bridge center continuously changes its potential in normal operation between ground and the intermediate circuit voltage, a current flow through the second capacitor can be generated and used to generate a current flow through the primary winding. Thus, this embodiment can also be used to generate a current through the secondary winding during normal operation and to charge the capacitor C _VCC and thus to supply an auxiliary voltage to the controller.

Preferably, the first terminal of the second capacitor is coupled to the bridge center and the second terminal of the second capacitor to the reference electrode of the switch. Since the switch is coupled to the primary winding such that a current through the switch generates a current through the primary winding, this ensures that a displacement current of the second capacitor leads to a current through the primary winding.

In a further embodiment, the auxiliary voltage generating device further comprises a third diode, the primary winding being coupled to the first input terminal via the third diode, the third diode being arranged to allow current to flow from the first input terminal to the primary winding the connection point between the primary winding and the third diode is coupled to the second terminal of the second capacitor.

Preferably, the device for generating an auxiliary voltage further comprises a third capacitor, which is connected in parallel to the ohmic resistance. This allows the time constant at which the second capacitor is charged and discharged and thus set the duration of a current flow through the primary winding and therefore also through the secondary winding.

Finally, it is preferred if a zener diode is connected in parallel with the first capacitor. This protects the provided auxiliary voltage against overvoltage.

Further advantageous embodiments will become apparent from the dependent claims.

Short description of the drawing (s)

Fig. 1

in schematischer Darstellung eine aus dem Stand der Technik bekannte Schaltungsanordnung zum Betreiben mindestens einer Entladungslampe;

Fig.

2 in schematischer Darstellung ein erstes Ausführungsbeispiel einer erfindungsgemäßen Schaltungsanordnung zum Betreiben mindestens einer Entladungslampe;

Fig. 3

in schematischer Darstellung ein zweites Ausführungsbeispiel einer erfindungsgemäßen Schaltungsanordnung zum Betreiben mindestens einer Entladungslampe; und

Fig. 4

in schematischer Darstellung ein drittes Ausführungsbeispiel einer erfindungsgemäßen Schaltungsanordnung zum Betreiben mindestens einer Entladungslampe.

In the following, three embodiments of a circuit arrangement according to the invention will now be described in more detail with reference to the accompanying drawings. Show it:

Fig. 1

a schematic representation of a known from the prior art circuit arrangement for operating at least one discharge lamp;

FIG.

2 shows a schematic illustration of a first exemplary embodiment of a circuit arrangement according to the invention for operating at least one discharge lamp;

Fig. 3

a schematic representation of a second embodiment of a circuit arrangement according to the invention for operating at least one discharge lamp; and

Fig. 4

a schematic representation of a third embodiment of a circuit arrangement according to the invention for operating at least one discharge lamp.

Preferred embodiment of the invention

The referring to Fig. 1 introduced reference numerals are for in the FIGS. 2 to 4 illustrated embodiments for the same and similar components continue to be used. In this respect, the following will essentially refer to the differences from the circuit arrangement of Fig. 1 received.

In the Fig. 2 illustrated embodiment of a circuit arrangement according to the invention further comprises the Fig. 1 known operating supply circuit 18 for the controller 10. To reduce the standby losses when the half-bridge driver 14 is switched off, however, it comprises a transformer TR whose primary winding PW is arranged in series with the ohmic resistor R _F. If the switch Q _ISS becomes conductive due to appropriate control by the two-point controller SSD, a current flows from the intermediate _{circuit voltage} U _ZW through the primary winding PW and the ohmic resistance R _F via the switch Q _ISS and the current source ISS to charge the capacitor Cvcc. In the non-conductive state of the switch Q _ISS , the primary winding PW can over the resistor R _F and a diode D _F free run. The secondary winding SW feeds the capacitor C _VCC via a diode D _CC , at which the auxiliary voltage V _{CC is} provided. The freewheeling diode D _F provides with the resistor R _F for the demagnetization of the transformer TR.

As soon as the output circuit 16 is stopped by a corresponding signal at the interface 12 and thus at the half-bridge driver 14, the standby mode is active and the two-point controller SSD is activated. If the two-point controller SSD determines that the auxiliary voltage V _{CC has} fallen below the lower threshold of the two-position controller SSD by sensing its input 20, the current source ISS is switched on via the switch Q _ISS . Thus, a current flows through the primary winding PW and thus, transformed with the transmission ratio, and current from the secondary winding SW via the diode D _CC in the capacitor Cvcc. As a result, the voltage V _CC at the capacitor C _{VCC increases} . As soon as the voltage V _{CC reaches} the upper threshold of the two-point controller SSD, the current source _{ISS is} switched off via Q _ISS . The primary energy stored in the transformer is discharged via the resistor R _F and the freewheeling diode D _F.

The embodiments of circuit arrangements according to the invention according to Fig. 3 and according to Fig. 4 do not require a separate operating supply circuit for the controller 10, that is, the controller 10 is also in normal operation, when the output circuit 16 is in operation, over the transformer TR powered. For this purpose, a capacitor C _S between the half-bridge center HM on the one hand and the diode D _F and the primary winding PW of the transformer TR on the other hand is coupled. The resistor R _F is a capacitor C _{S / F connected in} parallel. Via the interface 12, the output circuit 16 is activated and simultaneously deactivated the two-point controller SSD. This is the standby auxiliary voltage generation, see the comments on this Fig. 2 , shut down. The switch Q _ISS separates the current source ISS from the auxiliary voltage V _CC . The inverter comprising the switches S1 and S2 alternately switches the potential at the half-bridge center HM at a predetermined frequency between U _ZW and ground.

Step 1: The voltage at the half-bridge center HM of the output circuit 16 decreases from the intermediate _circuit voltage U _ZW to ground:

Here, the capacitor C _S via the primary winding PW, the parallel circuit of the ohmic resistor R _F and the capacitor C _{S / F} and charged via the switch S2 to the intermediate _{circuit voltage} U _ZW . This is done with a time constant which results from the ohmic resistance R _F , the capacitor C _{S / F} and the transformed load at the terminal at which the auxiliary voltage V _{CC is} supplied to the controller 10. During this charging process, the secondary winding SW of the transformer TR charges the capacitor C _VCC via the diode D _CC .

With the dimensioning of the capacitor C _S , the transmission ratio ü of the transformer TR and the components C _{S / F} and R _F , the transmitted energy can be optimized and adjusted.

Small capacitance values for the capacitor C _S are already sufficient for generating an auxiliary voltage with sufficient power. In one embodiment, the capacitor C _S was 150 pF, the gear ratio ü of the transformer TR was 10, the ohmic resistance R _F was 5.6 kΩ, and the capacitor C _{S / F} was 6.8 nF. Thus, an auxiliary voltage of V _CC equal to 15 V could be generated, which was loadable at 30 mA.

In order to protect the auxiliary voltage V _CC from overvoltage, a Zener diode D _{Z can be} provided, as shown in dashed lines.

• Hierbei wird der Kondensator C_S über den ersten Schalter S1 und die Diode D_F entladen. Er steht damit für die nächste fallende Flanke wieder zur Einspeisung eines Ladestroms zur Verfügung.

Step 2: The voltage at the half-bridge center HM of the output circuit 16 rises from ground to the intermediate _circuit voltage U _ZW :

• In this case, the capacitor C _S is discharged via the first switch S1 and the diode D _F. It is thus available again for the supply of a charging current for the next falling edge.

Due to the use of a transformer TR, the capacitor C _S can be dimensioned very small, for example 100 to 150 pF.

In the Fig. 4 illustrated embodiment of a circuit arrangement according to the invention is a variant of the in Fig. 3 shown. Here, however, the capacitor C _{S is} charged via the diode D _S and the switch S2. An energy transfer takes place here during the unloading process of the Capacitor C _S instead, which takes place via the switch S1, the primary winding PW of the transformer TR, the parallel connection of the ohmic resistor R _F and the capacitor C _{S / F} and the diode D _F. The charging energy can be adjusted via the transmission ratio ü of the transformer TR and the time constant effective during the respective charging process.

The time constant is chosen in particular such that a full transhipment of the capacitor C _S for generating a maximum current-time area by the primary winding PW is made possible.

Claims (9)

1. Circuit arrangement for operating at least one discharge lamp (La) with:

   - a first and a second input terminal for connecting a supply voltage;

   - an inverter, which comprises at least one first switch (S1) and one second switch (S2), which are coupled in series between the first and the second input terminal and between which a bridge center point (HM) is defined;

   - a drive circuit for at least the first switch (S1) and the second switch (S2) with an input for receiving a control signal;

   - an apparatus for generating an auxiliary voltage (V_CC) comprising:

   - a first capacitor (C_VCC) ;

   - a terminal for the provision of the auxiliary voltage (V_CC), which terminal is coupled to a reference potential via the first capacitor (C_VCC);

   - a two-state controller (SSD) with a first input to which the control signal in inverted form is coupled, a second input, which is coupled to the terminal for the provision of the auxiliary voltage (V_CC), and an output;

   - a switch (Q_ISS) with a control electrode, a working electrode and a reference electrode, the control electrode being coupled to the output of the two-state controller (SSD), the working electrode being coupled to the terminal for the provision of the auxiliary voltage (V_CC); and

   - a nonreactive resistor (R_F);
   characterized in that the apparatus for generating the auxiliary voltage (V_CC) furthermore comprises a transformer (TR) with a primary winding (PW) and a secondary winding (SW), the transformer (TR) being coupled to the first and the second input terminal, the terminal for the provision of the auxiliary voltage (V_CC) and the switch (Q_ISS) in such a way that a current through the switch (Q_ISS) results in a current through the primary winding (PW), which, corresponding to the transformation ratio of the transformer, additionally results in a current through the secondary winding (SW) and therefore in charging of the first capacitor (C_VCC).
2. Circuit arrangement according to Claim 1, characterized in that the primary winding (PW) and the nonreactive resistor (R_F) are connected in series, and this series circuit is coupled between the reference electrode of the switch (Q_ISS) and the first input terminal; the apparatus for generating the auxiliary voltage (V_CC) furthermore comprising:

   - a first diode (D_F), which is connected in parallel with the series circuit comprising the primary winding (PW) and the nonreactive resistor (R_F) and is arranged such that it enables freewheeling of the current through the primary winding (PW);
   and

   - a second diode (D_CC), which is connected in series with the secondary winding (SW), the series circuit comprising the secondary winding (SW) and the second diode (D_CC) being coupled between the reference potential and the terminal for the provision of the auxiliary voltage (V_CC).
3. Circuit arrangement according to either of Claims 1 and 2, characterized in that a current source (ISS) is coupled between the working electrode of the switch (Q_ISS) and the terminal for the provision of the auxiliary voltage (V_CC).
4. Circuit arrangement according to Claim 3, characterized in that the current source (ISS) is realized by a nonreactive resistor.
5. Circuit arrangement according to one of the preceding claims, characterized in that the apparatus for generating an auxiliary voltage (V_CC) furthermore comprises a second capacitor (C_S) with a first and a second terminal, which is coupled to the bridge center point (HM) and the primary winding (PW) in such a way that a capacitive displacement current can flow through the primary winding (PW).
6. Circuit arrangement according to Claim 5, characterized in that the first terminal of the second capacitor (C_S) is coupled to the bridge center point (HM), and in that the second terminal of the second capacitor (C_S) is coupled to the reference electrode of the switch (Q_ISS).
7. Circuit arrangement according to Claim 5, characterized in that the apparatus for generating an auxiliary voltage (V_CC) furthermore comprises a third diode (D_S), the primary winding (PW) being coupled to the first input terminal via the third diode (D_S), the third diode (D_S) being arranged to allow a current flow from the first input terminal to the primary winding (PW), the node between the primary winding (PW) and the third diode (D_S) being coupled to the second terminal of the second capacitor (C_S).
8. Circuit arrangement according to one of Claims 5 to 7, characterized in that the apparatus for generating an auxiliary voltage (V_CC) furthermore comprises a third capacitor (C_S/F), which is connected in parallel with the nonreactive resistor (R_F).
9. Circuit arrangement according to one of the preceding claims, characterized in that a zener diode (D_Z) is connected in parallel with the first capacitor (C_VCC).

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