DE102008016754A1 - Low-voltage supply in control gear for bulbs - Google Patents

Abstract

A low-voltage supply circuit for an operating device for lighting means, in particular a ballast for gas discharge lamps, in which one or more gas discharge lamps are switchable as the load of a half-bridge circuit or full-bridge circuit, comprises:
a starting resistor supplied with mains voltage and / or a charging circuit supplied from the half or full bridge circuit, which charges / charges an energy storage element whose charging voltage represents the low-voltage supply,
- Wherein the starting resistor and / or the charging circuit can be separated by means of a switch when the charging voltage of the energy storage element has risen to a switch-off, and
- The starting resistor is switched on again by means of the switch when the charging voltage of the energy storage element has dropped to a switch-on, wherein the switch-on threshold is selected lower than the switch-off.

Description

The The present invention relates to the field of so-called Low-voltage supply, especially for control gear for illuminants, such as electronic ballasts for gas discharge lamps as well as drivers for LED modules.

The Low-voltage supply is a circuit arrangement by means of in the operating device, a DC power supply in one Voltage range can be generated as it is for the supply voltage of (active) electronic components (integrated circuits, Microcontrollers, ASICs, etc.) is typical.

typically, These DC supply voltages are in a range of below 15 volts DC. Basically it is from the state of the art in Range of control gear known for bulbs, that for a start phase of the operating device immediately after switching on the mains voltage supply, a first start-up low-voltage supply is available. Typically this is low voltage power supply for the starting phase a so-called start-up resistance, ie an ohmic resistor supplied with mains voltage. The voltage arising at this starting resistor can be rectified and, for example, charge a capacitor whose charging voltage then in an initial phase, the necessary supply voltage for provides a control circuit of the operating device.

In a second phase, so if the control circuit by means of the starting resistance has started up, the control circuit controls the operation of the operating device. For this phase, ie with active control circuit, is usually then the low-voltage supply starting from clocked circuit groups of the operating device won. These clocked circuit groups For example, it may be a full bridge circuit or a half-bridge circuit for supplying gas discharge lamps with RF voltage, an active PFC circuit in the form of a boost converter, a clocked heating circuit for filaments of gas discharge lamps etc. At these clocked component groups, for example, by a capacitive coupling to the normal operation of the control unit necessary low-voltage supply can be obtained.

One Disadvantage of this known two-stage construction of the low-voltage power supply It is natural that the starting resistance even at operational Control circuit in normal operation continues to be supplied with mains voltage is and thus at this starting resistance a power loss in Normal operation of the control gear drops.

An example for minimizing the standby power (representing a power dissipation) in a lighting device is from the EP 1 374 366 B1 also called in this case for the first phase, the low-voltage supply by an ohmic resistance (see 2 of the EP 1 374 366 B1 ) is won. In the EP 1 374 366 B1 is then a Zener diode D5 and a capacitor C12 as a low-voltage power supply for the integrated circuits, said capacitor / diode connection is branched off from the midpoint of a half-bridge circuit.

The Invention has now taken on the task, the low-voltage supply for integrated circuits in operating devices for energy-efficient lighting.

These Task is solved by the characteristics of the independent Claims. Make the dependent claims the central idea of the invention in particularly advantageous Continue.

• – die Versorgungsschaltung einen mit Netzspannung versorgten Anlaufwiderstand und/oder eine ausgehend von der Halb- oder Vollbrückenschaltung versorgte Ladeschaltung aufweist, die ein Energiespeicherelement auflädt/aufladen, dessen Ladespannung die Niedervoltversorgung darstellt,
• – der Anlaufwiderstand und/oder die Ladeschaltung mittels eines Schalters abtrennbar ist, wenn die Ladespannung des Energiespeicherelements auf eine Abschaltschwelle angestiegen ist, und
• – bei der der Anlaufwiderstand wieder mittels des Schalters zuschaltbar ist, wenn die Ladespannung des Energiespeicherelements auf eine Einschaltschwelle abgesunken ist, wobei die Einschaltschwelle niedriger gewählt ist als die Abschaltschwelle.

According to a first aspect of the invention, there is provided a low-voltage supply circuit for an operating device for lighting devices, in particular a ballast for gas discharge lamps, in which one or more gas discharge lamps can be switched as the load of a half-bridge circuit or full-bridge circuit, wherein:

• The supply circuit has a starting resistor supplied with mains voltage and / or a charging circuit supplied from the half or full bridge circuit, which charges / charges an energy storage element whose charging voltage represents the low-voltage supply,
• - The starting resistor and / or the charging circuit is disconnected by means of a switch when the charging voltage of the energy storage element has risen to a switch-off, and
• - In which the starting resistor is switched on again by means of the switch when the charging voltage of the energy storage element has dropped to a switch-on, wherein the switch-on threshold is selected lower than the switch-off.

• – die Versorgungsschaltung einen Anlaufwiderstand aufweist, der mit Netzspannung versorgbar ist und ein Energiespeicherelement auflädt, dessen Ladespannung die Niedervoltversorgung darstellt,
• – der Anlaufwiderstand mittels eines Schalters abtrennbar ist, wenn die Ladespannung des Energiespeicherelements auf eine Abschaltschwelle angestiegen ist.

According to a further aspect of the invention there is provided a low-voltage supply circuit for a control device for lighting means, in particular a ballast for gas discharge lamps, in which one or more gas discharge lamps are switchable as a load of a half-bridge circuit or full bridge circuit, wherein

• The supply circuit has a starting resistor which can be supplied with mains voltage and charges an energy storage element whose charging voltage represents the low-voltage supply,
• - The starting resistor is disconnected by means of a switch when the charging voltage of the energy storage element has risen to a switch-off.

Of the Starting resistor can be switched on again by means of the switch, when the charging voltage of the energy storage element to a switch-on has fallen, with the switch-on threshold selected lower is considered the shutdown threshold.

Of the Switch can be a transistor.

The Charging voltage of the energy storage element may be a comparator Hysteresis be supplied, the switch starting is actuated by the output signal of the comparator.

through the output of the comparator can selectively be a load or Power source be switchable, by means of which in turn selectively a current is deductible from the control input of the switch.

The Circuit can be designed as an integrated circuit.

One Another aspect of the invention relates to a control gear for lighting, in particular a ballast for gas discharge lamps, in which one or more gas discharge lamps as Load of a half bridge circuit or full bridge circuit switchable, comprising a circuit as stated above.

• – ein Anlaufwiderstand mit Netzspannung versorgt wird und ein Energiespeicherelement auflädt, dessen Ladespannung als Niedervoltversorgung des Betriebsgeräts dient, und
• – der Anlaufwiderstand mittels eines Schalters abgetrennt wird, wenn die Ladespannung des Energiespeicherelements auf eine Abschaltschwelle angestiegen ist.

The invention also relates to a method for providing a low-voltage supply circuit in an operating device for lighting means, in particular a ballast for gas discharge lamps, in which one or more gas discharge lamps are switchable as a load of a half-bridge circuit or full bridge circuit, wherein:

• - A starting resistor is supplied with mains voltage and an energy storage element charges, the charging voltage serves as a low-voltage supply of the operating device, and
• - The starting resistor is disconnected by means of a switch when the charging voltage of the energy storage element has risen to a switch-off.

• – die Versorgungsschaltung mit der Halb- oder Vollbrücke gekoppelt ist und eine Gleichrichterschaltung aufweist, dessen Ausgang ein Energiespeicherelement auflädt, dessen Ladespannung die Niedervoltversorgung darstellt, und
• – die Versorgungsschaltung mittels eines Schalters abtrennbar ist, wenn die Ladespannung des Energiespeicherelements auf eine Abschaltschwelle angestiegen ist.

Yet another aspect of the invention relates to a low-voltage supply circuit for an operating device for lighting, in particular a ballast for gas discharge lamps, in which one or more gas discharge lamps are switchable as a load of a half-bridge circuit or full bridge circuit, wherein

• - The supply circuit is coupled to the half or full bridge and having a rectifier circuit whose output charges an energy storage element whose charging voltage is the low-voltage supply, and
• - The supply circuit is disconnected by means of a switch when the charging voltage of the energy storage element has risen to a switch-off.

Preferably are the switching operations of the switch with the switching operations the half or full bridge circuit synchronized.

One Aspect of the invention, together with the shutdown of the low-voltage supply circuit, but in particular also be used independently can, is that the supply circuit is connected to the or full bridge inductively, preferably transformatively can be coupled and a two-way rectifier bridge (D) whose output charges the energy storage element.

• – die Versorgungsschaltung mit der Halb- oder Vollbrückenschaltung gekoppelt ist und eine Gleichrichterschaltung aufweist, dessen Ausgang ein Energiespeicherelement auflädt, dessen Ladespannung die Niedervoltversorgung darstellt, und
• – die Versorgungsschaltung mittels eines Schalters abgetrennt wird, wenn die Ladespannung des Energiespeicherelements auf eine Abschaltschwelle angestiegen ist.

Finally, the invention also proposes a method for generating a low-voltage supply circuit for a control device for lighting means, in particular a ballast for gas discharge lamps, in which one or more gas discharge lamps are switchable as a load of a half-bridge or full-bridge circuit, wherein

• - The supply circuit is coupled to the half or full bridge circuit and having a rectifier circuit whose output charges an energy storage element whose charging voltage is the low-voltage supply, and
• - The supply circuit is disconnected by means of a switch when the charging voltage of the energy storage element has risen to a switch-off.

Further Features, advantages and features of the invention will now will be explained with reference to the figures of the accompanying drawings.

1 shows a low-voltage supply circuit according to the invention in a control device for lighting means,

2 shows waveforms in the circuit of 1 .

3 shows an inventive inductively (transformer) coupled low-voltage supply circuit in an operating device for lighting means with a full bridge circuit, and

4 shows an inventive inductively (transformer) coupled low-voltage supply circuit in a control gear for lighting medium with a half-bridge circuit.

In 1 a low-voltage power supply according to the invention is shown. A starting resistor R1 is supplied via a terminal N with mains voltage. In series with this starting resistor R1, a switch such as a transistor T1 is connected. In turn, in series with the switch T1, a capacitor C1 is connected, wherein the charging circuit of the capacitor C1 represents the low-voltage supply. Thus, in the illustrated example, the low-voltage voltage at a tap V _{CC of} the in 1 shown circuit and are supplied, for example, an integrated circuit (IC, ASIC, microcontroller, etc.).

Parallel to the starting resistor R1 is a second resistor R2 connected.

The low-voltage _VCC , that is, the charging voltage of the capacitor C1, is supplied to a first comparator K1. The comparator K1 is supplied as a reference voltage on the one hand, a voltage U1 and on the other hand, a voltage U2, wherein the voltage U1 is greater than the voltage U2. In summary, the comparator K1 is therefore a comparator with hysteresis (often referred to as a Schmitt trigger). The output signal of the comparator K1 is fed to a switch S1, which can selectively switch a load or current source L1.

When the charging voltage of the capacitor C1, ie the low-voltage V _{CC has reached} the turn-on threshold U _{2 of} the comparator K1, the output of the comparator K1 switches the switch S1 and thus the load or current source L1. As a result, the current is drawn off via the ohmic resistor R2 from the control input of the switch T1, which results in that the switch T1 is opened and thus the starting resistor R1 is disconnected.

When separated start-up resistor R1 (with open switch T1), the charging voltage of the capacitor C1, ie the low-voltage supply V _CC slowly decrease again, if by means of this low-voltage V _CC a consumer such as an integrated circuit is powered. Now, when the low-voltage V _CC has dropped to the lower switch-on threshold U _{2 of} the comparator K1, the output of the comparator K1 switches off again via the switch S1, the load or the current source L1, which in turn leads to a switch on the switch T1, as when switched off Load or current source L1, the current through the resistor R2 again actuates the control input of the switch T1. Thus, there is a recharging of the capacitor C1. Overall, therefore, by means of the hysteresis comparator K1 a two-point control of the low-voltage V _CC can be achieved, so that the low-voltage V _CC zigzag or sawtooth between the upper Abschaltschwelle U1 and the lower turn-on U2 of the two reference values of the comparator K1 runs. Already by this temporary shutdown of the starting resistor R1, the low-voltage supply is improved energetically.

The switch-off start-up resistor R1 thus provides in particular (but not exclusively) for the start phase, immediately after switching on the mains voltage supply N in this start-up phase, the low-voltage supply V _CC ready. However, the switch-off starting resistor R1 can alternatively or additionally to the start phase in operating phases in which no (or insufficient) clocked power supply within the operating device such as a tap on a clocked half-bridge is provided to provide the low-voltage supply V _CC .

By means of this start-up low-voltage supply, an integrated circuit, which is supplied with the voltage V _CC , can be started. In an operating device for lighting means, this integrated circuit will then drive for example in a known manner a full-bridge circuit or a half-bridge circuit, as the load of which a lighting means such as a low-pressure or high-pressure gas discharge lamp is connected. Alternatively or additionally, the control unit can drive an active PFC circuit which is supplied with the rectified mains voltage and which generates a high intermediate circuit voltage, by means of which in turn the full bridge or half bridge circuit is supplied.

Farther alternatively or additionally, the control unit can Clocked heating circuit for heating filaments of the lamps generate, as is the case in particular for low-pressure gas discharge lamps typical.

The fullbridge point of the circuit in 1 So is connected to a clocked component group (full bridge circuit, half-bridge circuit, active PFC circuit, clocked heating circuit for filaments, etc.). By means of the low-voltage supply VCC of the start-up phase obtained via the starting resistor R1, the integrated circuit supplied with it will therefore clock the said component groups, so that at the point 'fullbridge' the 1 a voltage is applied. By means of a diode circuit D, this is rectified with a capacitor C2, this voltage and thus can then charge the capacitor C1.

In this second phase with operational integrated circuit so the supply via the Starting resistor R1 is no longer necessary, so that according to the invention it is ensured that the starting resistor R1 is switched off in this phase with an operational integrated circuit (control unit). This is done by the fact that the charging voltage generated in this phase for the capacitor C1 is selected to be higher than the turn-on threshold U2 of the comparator K1.

More specifically, the low-voltage V _{CC is} supplied to a second comparator K2, which is also designed as a hysteresis comparator (Schmitt trigger) and receives a switch-off threshold U3 and a switch-on threshold U4. In this case, it is ensured that the reference values U3, U4 of the second comparator K2 are higher than the reference values U1, U2 of the comparator K1 for the startup phase of the low-voltage supply.

By means of the output signal of the second comparator K2, if necessary, a further switch S2 can be actuated via a driver DRV, via which the charging can be interrupted selectively starting from the point 'full bridge' of the capacitor C1. Again, a two-step control of the charging voltage of the capacitor C1 and thus the low-voltage supply V _{CC is} achieved via the comparator K2 with two reference values. When the charging voltage of the capacitor C1 has dropped to a switch-on threshold U4, the switch S2 is closed so that the capacitor C1 is charged starting from the point 'fullbridge' and the rectifier circuit C2, D. If, in contrast, the charging voltage of the capacitor C1, that is, the low-voltage supply V _{CC has reached} the upper switch-off threshold, the switch S2 is opened and the charging of the capacitor C1 is prevented.

The self-adjusting signal curves will now be referred to 2 be explained. In a phase T1, the low-voltage supply voltage V _{CC will} increase substantially linearly by charging the capacitor C1 by means of the starting resistor R1. Now, when the charging voltage of the capacitor C1 has reached the turn-off threshold U1, the switch T1 is opened and thus the charging resistor R1 and the mains voltage supply N disconnected, so that in a phase T2, the low-voltage supply voltage V _{CC will} again decrease. This process is repeated so that the already mentioned zigzag (sawtooth) profile of the voltage V _CC between the two reference values U1, U2 of the comparator K1 will be established. The signal SW startup shows the voltage at the control input of the switch T1.

In the scenario of 2 It is assumed that at a point in time T3, the low-voltage supply obtained via the starting resistor R1 has been of sufficient duration to put the integrated circuit into operation, which makes it possible to generate a voltage at the point 'fullbridge'. At this point in time T3, the voltage drops at the point 'fullbridge' as in 2 shown at a non-zero value. Thus, after the time T3, the charging voltage at the capacitor C1 will rise to the value, that is, the switch-off threshold for the switch S2. At the time T4, this switch-off threshold U3 is reached, so that the switch S2 is closed and the power supply is disconnected. Again, the low-voltage supply voltage V _{CC will} decrease until the switch-on threshold for the low-voltage supply circuit is reached, and the switch S2 is opened again. Overall, this results in a zigzag-like (sawtooth) profile of the voltage VCC between the two reference values U3, U4 of the second comparator K2.

there is inventively ensured that the disconnection of the low-voltage supply via the switch S2 is synchronized with the timing of the half-bridge circuit, Full bridge circuit, PFC circuit or the clocked Heating circuit to minimize circuit losses.

It should be noted that the tap for the full bridge point of the circuit in FIG 1 either by capacitive coupling with the full bridge, half-bridge circuit, etc., or else galvanically isolated, for example via an inductive tap.

The diode D1 in 1 is provided to keep the base of the voltage, so the voltage at the control input of the switch T1 to a minimum value greater than zero volts, on the other hand, the potential at the control input of the switch T1 by removing the base current via the switched load or current source L1 inadmissible could possibly lead to an inadmissible reverse operation or possibly damage to the switch, if this is designed as a transistor.

Compared to the state of the art EP 1 374 366 B1 is there existing Zener diode D5 now no longer available, which has several advantages. On the one hand, the inventive circuit according to 1 better suited for the high dynamics, ie the different load between the operation of full bridges or half-bridge circuit with low frequency (for example when igniting a HID lamp) compared to the HF operation. This high dynamics represents a high load on a Zener diode. Furthermore, a Zener diode also has electrical losses.

All in all Thus, according to the invention results in a more accurate defined low-voltage power supply, and this at lower Power losses or temperature development.

These electrical losses are created by synchronizing the low-voltage power supply, d. H. the switch S2 with the half-bridge / full-bridge drive further reduced. The switching of the switch S2 thus always takes place if, for example, by capacitive decoupling at the point 'fullbridge' just no energy input in the direction of the capacitor C1 takes place. With a midpoint decoupling of the point 'fullbridge' Thus, the switch S2 is only turned on when no flank, but a temporally constant control of a high-frequency clocked Switch of the half-bridge or full bridge circuit is present.

According to the Invention is provided that the switching on of the switch S2 (although this is actually due to the output of the comparator K2 would be given) possibly temporally something after the range of one Edge of the high-frequency control of the switch of the half-bridge or full bridge circuit is delayed. The same Of course, the same applies to switching off the switch S2, which may be due to a time delay in the range of Constant control (and not a control edge of the high-frequency clocked switch of the full bridge or half-bridge circuit is laid).

Because the switch-off / switch-on thresholds for the switch S2 are set higher than the switch-off / switch-on threshold for the switch T1 of the starting resistor R1, the low-voltage supply is automatically restarted via the starting resistor R1 when the voltage supply V _{CC is} again limited in the direction of the lower voltage corridor the reference values U1, U2 decrease.

In 3 a low-voltage power supply according to the invention is shown with an inductive tap on a full bridge circuit. The inductive decoupling takes place in this case at the output choke via a transformer decoupling. The capacitor Cx corresponds to the capacitor C2 in the 1 , Unlike the example in 1 the recharging of the capacitor Cx is due to the following two-way rectifier bridge D in both directions, so that in comparison to 1 a higher charge can be transferred from the capacitor Cx. Instead of the rectifier bridge D in 3 but can also be a simple diode path D as in the 1 be used to charge the capacitor C1. The transformer decoupling offers the advantage that on the transmission ratio of primary to secondary winding, the height of the tapped voltage and thus the decoupling of the charge can be influenced. The control of the switch S2 can also in this example in the same manner as in the 1 shown variant.

But it can also be done instead of the inductive decoupling capacitive decoupling. The _start-up resistor R _start can not be switched off in this example, but it can also be used in the same way as in 1 a switchable via a switch resistor can be used.

In the full bridge shown are in operation of the lamp For example, in each case the two bridge diagonals alternately clocked to each other or it is only one diagonal each activated by a switch of the diagonal clocked high-frequency and the other switch remains permanently on.

In 4 a low-voltage power supply according to the invention with an inductive tap on a half-bridge circuit is shown. The tap is done as in the example of 3 via a secondary winding on the output choke. The control of the switch S2 can also in this example in the same way as in the in 1 shown variant.

But it can also be done instead of the inductive decoupling capacitive decoupling. The _start-up resistor R _start can not be switched off in this example, but it can also be used in the same way as in 1 a switchable via a switch resistor can be used.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1374366 B1 [0006, 0006, 0006, 0044]

Claims (21)

Low-voltage supply circuit for a control gear for lighting, in particular a ballast for gas discharge lamps, at the one or more gas discharge lamps as a load of a half-bridge circuit or full bridge circuit are switchable, wherein: - the Supply circuit a starting voltage supplied with mains voltage and / or one from the half or full bridge circuit powered charging circuit having an energy storage element charging / charging, the charging voltage of the low-voltage supply represents, - The starting resistor and / or the charging circuit means a switch is disconnected when the charging voltage of the energy storage element has risen to a switch-off, and - at the starting resistance can be switched on again by means of the switch is when the charging voltage of the energy storage element to a Switch-on threshold has dropped, with the switch-on threshold lower is selected as the switch-off threshold. Low-voltage supply circuit for a Operating device for lamps, in particular a Ballast for gas discharge lamps, in which one or more gas discharge lamps as a load of a half-bridge circuit or full bridge circuit are switchable, wherein: - the Supply circuit has a starting resistance, the mains voltage can be supplied and charges an energy storage element, whose charging voltage represents the low-voltage supply, - of the Starting resistance is disconnected by means of a switch, if the Charging voltage of the energy storage element to a switch-off has risen. A circuit according to claim 2, wherein the starting resistance again switchable by means of the switch, when the charging voltage of the energy storage element dropped to a switch-on is, with the turn-on threshold is set lower as the shutdown threshold. A circuit according to claim 2 or 3, wherein the switch a transistor is. Circuit according to one of the preceding claims, wherein the charging voltage of the energy storage element is a comparator supplied with hysteresis, the switch starting is actuated by the output signal of the comparator. A circuit according to claim 5, wherein by means of the output signal the comparator is selectively switchable to a load or current source, by means of which, in turn, selectively draw a current from the control input of the Switch is removable. Circuit according to one of the preceding claims, which is designed as an integrated circuit. Operating device for light bulbs, in particular a ballast for gas discharge lamps, wherein one or more gas discharge lamps as a load of a half-bridge circuit or full bridge circuit are switchable, comprising a Circuit according to one of the preceding claims. Method for providing a low-voltage supply circuit in a control gear for lighting, in particular a ballast for gas discharge lamps, at the one or more gas discharge lamps as a load of a half-bridge circuit or full bridge circuit are switchable, wherein: - one Starting resistor is supplied with mains voltage and an energy storage element recharges its charging voltage as a low voltage supply of the Operating equipment is used, and - the starting resistance is disconnected by means of a switch when the charging voltage of the Energy storage element has risen to a switch-off. The method of claim 9, wherein the starting resistance is switched on again by means of the switch when the charging voltage of the energy storage element dropped to a switch-on is, with the turn-on threshold is set lower as the shutdown threshold. Method according to one of claims 9 or 10, wherein the charging voltage of the energy storage element is a comparator is supplied with hysteresis and the switch starting is operated by the output signal of the comparator. The method of claim 11, wherein by means of The output signal of the comparator selectively a load or current source is switched by means of which in turn selectively a stream of the Control input of the switch is deducted. Low-voltage supply circuit for an operating device for lamps, in particular a ballast for gas discharge lamps, in which one or more gas discharge lamps as a load of a half-bridge circuit or full bridge circuit are switchable, wherein: - the supply circuit is coupled to the half or full bridge and has a rectifier circuit whose output charges an energy storage element whose charging voltage is the low-voltage supply, and - the supply circuit is disconnectable by means of a switch when the charging voltage of the energy storage element is set to a switch-off threshold rose. The circuit of claim 13, wherein the supply circuit again switchable by means of the switch, when the charging voltage of the energy storage element dropped to a switch-on is, with the turn-on threshold is set lower as the shutdown threshold. A circuit according to claim 13 or 14, wherein the Switch is a transistor. Circuit according to one of Claims 13 to 15, at the switching operations of the switch with the switching operations the half or full bridge circuit are synchronized. Circuit according to one of Claims 13 to 16, where the supply circuit with the half or full bridge is transformer coupled and a two-way rectifier bridge (D) whose output charges the energy storage element. Low-voltage supply circuit for a Operating device for lamps, in particular a Ballast for gas discharge lamps, in which one or more gas discharge lamps as a load of a half-bridge circuit or full bridge circuit are switchable, wherein: - the Supply circuit coupled to the half or full bridge is and has a rectifier circuit whose output a Energy storage element charges, the charging voltage of the Low-voltage supply represents, and - the supply circuit with the half or full bridge inductive, in particular transforming coupled and has a two-way rectifier bridge (D), the output of which charges the energy storage element. Method for generating a low-voltage supply circuit for a control gear for bulbs, in particular a ballast for gas discharge lamps, wherein one or more gas discharge lamps as a load of a half-bridge circuit or full bridge circuit are switchable, wherein: - the Supply circuit coupled to the half or full bridge is and has a rectifier circuit whose output a Energy storage element charges, the charging voltage of the Low-voltage supply represents, and - the supply circuit is disconnected by means of a switch when the charging voltage of the Energy storage element has risen to a switch-off. The method of claim 18, wherein the switching operations the switch with the switching operations of the half or full bridge circuit are synchronized. The method of claim 18 or 19, wherein the Supply circuit with the half or full bridge transformer is coupled and a two-way rectifier bridge (D) whose output charges the energy storage element.