EP1385358A1 - Starter circuit for HID lamp - Google Patents

Abstract

The circuit has an ignition voltage generator connected to an alternating voltage generator or receiver (1) and with its output connected to the lamp (4) to provide an ignition voltage from the alternating voltage. The ignition voltage generator has at least one diode (3) connected in parallel with its output and a cascade circuit (D1-D5,C1-C5) of first or higher order in series with the diode as a voltage pump circuit. AN Independent claim is also included for the following: (a) a method of operating a discharge lamp.

Description

Technical field

The present invention relates to a circuit device for operating a discharge lamp with an AC generator or pickup device for providing an AC voltage and an ignition voltage generating device connected to the AC voltage generator or recording device is connected and to their Output the discharge lamp can be connected to generate an ignition voltage from the AC voltage. Furthermore, the present invention relates to a corresponding one Method for operating a discharge lamp.

State of the art

To operate a gas discharge lamp, a high voltage must first be applied to the lamp be applied to ignite the discharge process of the gas in the lamp. Subsequently a continuous operating voltage must be applied to the electrodes of the lamp. Therefor can either an electrical supply unit or circuit device can be used, which accomplish both the ignition process and the operating state can or two separate voltage sources, one for the ignition and the other is used for the operation. A voltage source that can be used for both states must be able to generate the high voltage for the ignition and then can work permanently with high efficiency during operation.

So far, superimposed ignitors have been used for the ignition of discharge lamps or resonance circuits used. For discharge lamps with a particularly high ignition voltage However, there are the following disadvantages:

In the case of a superimposed ignitor, the operating frequency for continuous operation is the Lamp limited by its inductance. This is especially true with high pressure lamps, due to the acoustic resonances that occur only in certain frequency windows can be operated, a major limitation. Beyond that Superimposed ignitors due to the necessary winding quality, switching elements (e.g. spark gaps) and capacitors are relatively expensive.

In the series resonance circuit, the ignition due to excessive voltage in discharge lamps requires with particularly high ignition voltage a very high quality and therefore accordingly high costs. The circuit complexity to the resonance frequency of such a resonance circuit hitting safely is significant. The limits also for series resonance circuits Inductance the operating frequency for continuous lamp operation. The use cheaper Control gear with a high frequency is therefore only possible to a very limited extent.

Presentation of the invention

The object of the present invention is therefore a circuit device and to propose a method that enables an inexpensive operation of a discharge lamp enable with high ignition voltage.

According to the invention, this object is achieved by a circuit device for operation a discharge lamp with an AC voltage generator or pickup device for providing an AC voltage and an ignition voltage generating device, which are connected to and connected to the AC generator or receiving device the output of which the discharge lamp can be connected to generate an ignition voltage from the AC voltage, the ignition voltage generating device at least one Includes diode connected in parallel to the output of the ignition voltage generating device is.

Furthermore, the above-mentioned object is achieved by a method for operating a Discharge lamp by providing an AC voltage and generating an ignition voltage from the AC voltage, the ignition voltage being generated by means of a diode, which is arranged parallel to the discharge lamp.

The parallel to the output of the ignition voltage generating device respectively the discharge lamp switched diode in connection with the output capacity of the AC voltage generator is used to increase the voltage amplitude according to the Effect of a pump circuit. With regard to a cascade pump circuit, that would correspond described a zero-order pump circuit.

The ignition voltage generating device therefore preferably comprises a cascade circuit first or higher order in series with the diode as a voltage pump circuit. With such cascade circuits, depending on the level of their order achieve high voltage increases, which is ultimately due to the quality of the components used or their own losses and the growing with increasing order Time constant is limited.

In the cascade connection there are two capacitors and two in particular per order Diodes provided in a known mutual connection. Thus can be proportionate cost effective components an effective voltage increase can be achieved.

It is favorable between the output of the ignition voltage generating device and the diode, d. H. in front of the discharge lamp, a choke coil is connected to limit the current. This allows a current to flow through the reduction in the resistance of the discharge lamp would occur after the ignition process.

A switch-off unit for switching off the pumping is preferably connected in series with the diode the voltage used after the ignition process. This shutdown unit can be inexpensive can be realized by a Zener diode or TVS diode (transient voltage suppressor). The nominal voltage of this Zener diode or TVS diode should be greater than the operating voltage the discharge lamp so as not to hinder the burning process or even to prevent.

In an advantageous embodiment of the circuit device, the ignition voltage generating device comprises a piezotransformer. With this a high voltage transmission ratio can be achieved can be achieved with a small size.

Alternatively, however, a conventional AC voltage source, e.g. Half-bridge, can be used with a coupling capacitor to generate the supply voltage.

The circuit topology according to the invention thus enables cost-effective operation of discharge lamps with a high ignition voltage, such as, for example, high-pressure discharge lamps for automotive headlights.

Brief description of the drawings

Figur 1

ein Prinzipschaltbild der erfindungsgemäßen Schaltungsvorrichtung;

Figur 2

ein Prinzipschaltbild einer anderen Ausführungsform der vorliegenden Erfindung;

Figur 3

ein Prinzipschaltbild einer weiteren Ausführungsform der vorliegenden Erfindung;

Figur 4

ein Schaltbild einer weiteren Ausführungsform der vorliegenden Erfindung;

Figur 5

ein Schaltbild einer noch weiteren Ausführungsform der vorliegenden Erfindung;

Figur 6

den Spannungsverlauf an den Elektroden einer Gasentladungslampe ohne (A) und mit einer Diode (B) vor der Zündung;

Figur 7

den Spannungsverlauf an den Elektroden einer Gasentladungslampe ohne (A) und mit einer Diode (B) während der Brennphase;

Figur 8

ein Schaltbild einer bevorzugten Ausführungsform der vorliegenden Erfindung;

Figur 9

den Spannungsverlauf an den Elektroden einer Gasentladungslampe, der sich durch eine Pumpschaltung nullter Ordnung gemäß Figur 4 vor der Zündung und nach der Zündung ergibt;

Figur 10

den Spannungsverlauf an den Elektroden einer Gasentladungslampe, der sich durch eine Pumpschaltung zweiter Ordnung gemäß Figur 8 vor der Zündung und nach der Zündung ergibt; und

Figur 11

den Spannungsverlauf an den Elektroden einer Gasentladungslampe, der sich durch eine Pumpschaltung dritter Ordnung vor der Zündung und nach der Zündung ergibt.

The present invention will now be explained in more detail with reference to the accompanying drawings, in which:

Figure 1

a schematic diagram of the circuit device according to the invention;

Figure 2

a schematic diagram of another embodiment of the present invention;

Figure 3

a schematic diagram of another embodiment of the present invention;

Figure 4

a circuit diagram of a further embodiment of the present invention;

Figure 5

a circuit diagram of yet another embodiment of the present invention;

Figure 6

the voltage curve at the electrodes of a gas discharge lamp without (A) and with a diode (B) before ignition;

Figure 7

the voltage curve at the electrodes of a gas discharge lamp without (A) and with a diode (B) during the burning phase;

Figure 8

a circuit diagram of a preferred embodiment of the present invention;

Figure 9

the voltage profile at the electrodes of a gas discharge lamp, which results from a zero-order pump circuit according to FIG. 4 before ignition and after ignition;

Figure 10

the voltage profile at the electrodes of a gas discharge lamp, which results from a second-order pump circuit according to FIG. 8 before ignition and after ignition; and

Figure 11

the voltage curve at the electrodes of a gas discharge lamp, which results from a third-order pump circuit before the ignition and after the ignition.

Preferred embodiment of the invention

The exemplary embodiments described below represent preferred embodiments of the present invention. According to a first embodiment of the present Invention, which is shown in Figure 1, is at the output of an AC power supply circuit 1 a transformer 2 connected. The output terminals of the transformer 2 are connected to the electrodes of a gas discharge lamp 4. Between the A diode 3 is connected to the electrodes of the gas discharge lamp.

The mode of operation of the circuit according to FIG. 1 can correspond to the voltage curve shown in FIG. 6 be removed. The AC voltage at the electrodes of the gas discharge lamp without the diode 3 has the sinusoidal voltage curve in the area A from FIG. 6. The diode 3 connected in parallel with the electrodes of the gas discharge lamp 3 causes that the AC voltage is raised / lowered to positive or negative values is, so that there is a doubling of the voltage amplitude. Depending on the type of discharge lamp, this double voltage amplitude is sufficient for ignition.

FIGS. 2 and 3 show alternative embodiments to that in FIG. 1. It the same switching elements or components 1 to 4 are used in each case. In addition, in the circuit of FIG. 2 there is a shutdown unit with the diode 3, respectively a threshold switch 5 connected. In the present case it is a Zener diode. Alternatively, a unidirectional TVS diode can also be used become. The Zener diode acts as a threshold switch 5 in the opposite direction switched to diode 3. With diode 5, the pump circuit is switched off after reached the breakdown of the lamp, the nominal voltage of the diode, i. H. the Zener tension, must be at least as large as the maximum operating voltage of the lamp. Through the series connection of the Zener diode as a switch-off element, the pump function of the Pump circuit of zero order, which consists only of the diode 3, switched. Pump circuits of a higher order are shown in connection with FIG. 8.

The circuit shown in FIG. 3 essentially has the same components, like that of Figure 2. The transformer 2 in the circuit of Figure 3 is around an electromagnetic transformer. The secondary-side coil becomes simultaneous used as a resonance coil for resonance operation. In series with the secondary coil is one Coupling capacitor 6 connected, which is charged by the pump circuit. With this The electrical supply circuit or the gas discharge lamp can be a resonance circuit operated very effectively. Before the lamp is ignited, the Circuit operated without load and the output voltage of the resonance transformer is on highest so that the lamp can be ignited. After ignition, when the lamp is in operation, its internal resistance decreases, which also reduces the output voltage of the resonance transformer is reduced due to the detuning, so that the gas discharge lamp with a lower voltage value specific to the lamp type can be operated with high efficiency. This voltage value must be lower than the value of the forward voltage of the diode 3. If this is not the case, the to the Lamp 4 applied voltage limited to the forward voltage of the diode 3.

FIG. 4 shows a concrete implementation of the embodiment shown in FIG. 2. The Transformer 2 is designed as a piezo transformer. The primary side is that of the AC voltage supply or the alternating voltage supplied to the generator 1 converted into mechanical vibrations by the piezoelectric element. This about mechanical vibrations transmitted to the piezoelectric element become secondary converted back into electrical signals. In the case of the mechanical resonance of the Piezo element there is a corresponding resonance increase of the secondary voltage. This voltage is further increased by the pump circuit with diodes 3 and 5, so that the ignition voltage of the lamp 4 is reached. When igniting and during operation The gas discharge lamp is very low-resistance, so that the current may be must be limited by a choke coil 7. The generator 1 for generating the primary side AC voltage can include a half bridge.

5 shows a further embodiment of the circuit according to the present invention shown. The AC voltage generated by the generator 1 is turned off a resonance coil 8 and a resonance capacitor 9 existing series resonance circuit created. The voltage at the resonance capacitor 9 is via a coupling capacitor 10 coupled to the lamp 4. In parallel to the lamp 4, this is already in connection with the pump circuit with the diodes 3 and 5 described in the previous figures Coupling capacitor 10 to avoid electrophoresis on the electrodes of the gas discharge lamp 4 should have a sufficiently high capacity for the so-called takeover, i.e. H the transition from glow discharge to arc discharge. If necessary, can A series resonance, possibly with low quality, is arranged in front of the coupling capacitor 10 to reach higher voltages.

In Figure 6 in area A is the signal waveform of the AC voltage at the output of the Transformer shown, which would be applied to the discharge lamp 4 if the diode 3rd would not exist. In area B of Figure 6, the waveform is shown, which is the discharge lamp 4 results from the diode 3. This doubles the Amplitude of the voltage at the electrodes of the discharge lamp 4. The diode 3 can thus can be considered as a zero-order pump circuit, as already mentioned.

FIG. 7 shows the course of the AC voltage after the discharge lamp has been ignited, i. H. during the burning phase. It can be clearly seen that the amplitude of the AC voltage is reduced compared to that of Figure 6. The reason for this is that the discharge lamp 4 has a significantly lower resistance after ignition, so that the Voltage on it is reduced in the burning phase. Furthermore, FIG. 7 shows that the pump circuit, i.e. H. the diode 3 has no effect during the burning phase, because the signal curve in area A, d. H. when diode 3 is switched off, is identical to the signal curve in area B, d. H. when diode 3 is switched on. The reason for this is the Zener diode 5, through which the pump circuit after the breakdown of the lamp in continuous operation is switched off.

FIG. 8 shows a variant of the embodiment in FIG. 4. Instead of The zero-order pump circuit in FIG. 4 is the circuit of FIG. 8 a second-order pump circuit. This means that between the diode 3 and the Zener diode 5 is connected in a cascade of diodes and capacitors. in the In this specific case, the diodes D1 to D5 are in series between the diode 3 and the Zener diode 5 switched. A capacitor C1 is located parallel to the diodes 3 and D1 a capacitor C2 to the diodes D1 and D2, a parallel to the diodes D2 and D3 Capacitor C3, a capacitor C4 parallel to the diodes D3 and D4 and parallel to the Diode D5 a capacitor C5. The components of a tier of the cascade are through the Areas I and II marked in Figure 8.

The zero-order cascade results in a peak voltage Û = U _SS -U _Z. After the first stage of the cascade, ie the first-order pump circuit, there is a peak voltage Û = 2x (U _ss -Uz). Finally, after the second stage of the cascade circuit, ie the second-order pump circuit, a peak voltage Û = 3x (U _ss -U _z ) arises. U _{ss means} the peak-to-peak value of the AC voltage on the secondary side of the transformer 2 and U _z the Zener voltage.

FIG. 9 shows the voltage curve at the gas discharge lamp 4 for the inventive Embodiments shown in Figures 2 to 5. After switching on, it turns the final pump voltage very quickly. After ignition, the pumping process switched off and the voltage drops to the burning voltage, as already related was explained with Figures 6 and 7.

In the case of a second-order pump circuit, which is shown in FIG. 8, the result in FIG Figure 10 reproduced voltage curve. In this case, the alternating voltage is with superimposed on a DC voltage, the value of which compared to the zero-order pump circuit is about twice as high. The final pump value is reached after about 4 ms. To the ignition also ends the pumping process and the lamp turns on Firing voltage as in Figure 9.

Finally, in FIG. 11, the voltage curve over time in a cascade connection is third Order reproduced. The achievable pump voltage is ideally appropriate higher, but the time constant with which this final pump voltage is reached is also significantly higher than for the second-order pump voltage according to FIG. 10. Also according to In this case the final pump value is not reached within 10 ms. For very high ignition voltages This means that this pump technology reaches its natural limit.

An advantage of the ignition circuit described is that it is generally essential lower breakdown voltage than is required for pulse ignitors because of the voltage time area is bigger here.

Claims (15)

Circuit device for operating a discharge lamp (4) with an alternating voltage generator or receiving device (1) for providing an alternating voltage and an ignition voltage generating device, which is connected to the alternating voltage generator or receiving device (1) and at the output of which the discharge lamp (4) can be connected, for generating an ignition voltage from the alternating voltage, characterized in that
the ignition voltage generating device comprises at least one diode (3) which is connected in parallel to the output of the ignition voltage generating device. The circuit device according to claim 1, wherein the ignition voltage generating device a cascade connection (D1 to D5, C1 to C5) of first or higher order in series to the diode (3) as a voltage pump circuit. Circuit device according to claim 2, wherein the cascade circuit (D1 to D5, C1 to C5) has two capacitors and two diodes per order. Circuit device according to one of claims 1 to 3, comprising a coil (7) connected between the output of the ignition voltage generating device and the diode (3) is to limit the current. Circuit device according to one of Claims 1 to 4, which is in series with the diode (3) a switch-off unit (5) for switching off the ignition voltage for the burning operation of the Discharge lamp (4). Circuit device according to claim 5, wherein the switch-off unit (5) is a Zener diode or has a TVS diode. Switching device according to claim 6, wherein the Zener voltage of the Zener diode is greater or is equal to the maximum operating voltage of the discharge lamp (4). Circuit device according to one of claims 1 to 7, wherein the ignition voltage generating device has a piezo transformer (2). Circuit device according to one of claims 1 to 7, wherein the ignition voltage generating device a magnetic transformer, on the secondary side a coupling capacitor (6) is connected. Method for operating a discharge lamp (4) Providing an AC voltage and Generating an ignition voltage from the AC voltage, characterized in that
the starting voltage is generated by means of a diode (3) which is arranged in parallel with the discharge lamp (4). The method of claim 10, wherein the ignition voltage is cascaded (D1 to D5, C1 to C5) first or higher order in series with the diode (3) as a voltage pump circuit is produced. The method of claim 10 or 11, wherein the current through the discharge lamp (4) is limited by a choke coil (7). Method according to one of claims 10 to 12, wherein the pumping of the ignition voltage automatically switched off based on a component characteristic after the ignition process becomes. Method according to one of claims 10 to 13, wherein the AC voltage by a Piezo transformer (2) is generated. Method according to one of claims 10 to 13, wherein the AC voltage by a magnetic transformer with a downstream coupling capacitor (6) generated becomes.

Images