WO2008028563A1

WO2008028563A1 - Dimmer circuit

Info

Publication number: WO2008028563A1
Application number: PCT/EP2007/007371
Authority: WO
Inventors: Winfried Zerbs
Original assignee: Schiederwerk Mbz Telekommunikation Gmbh & Co. Kg
Priority date: 2006-09-08
Filing date: 2007-08-22
Publication date: 2008-03-13
Also published as: DE202007018812U1

Abstract

A dimmer circuit (14) which produces little reaction on the power supply system for power regulation of an electrical load (5), in particular of a lamp, having a rectifier (2) which can be connected to a power supply system, having a half-bridge converter (3) which is fed by the rectifier (2), comprising two electrical switching elements (T1, T2), which are connected in series between the outputs of the rectifier (2), and a first connecting point (4) for the load (5) between the switching elements (T1, T2), and having a control component (7) which drives the switching elements (T1, T2) such that the connecting point (4) is connected alternately to one output and to the other output of the rectifier (2), by switching.

Description

Description dimmer circuit

The invention relates to a low-dimming network dimmer circuit for power control of an electrical load, in particular a lamp.

Such a dimmer circuit is known for example from DE 44 33 552 B4. In this case, the effect of non-sinusoidal consumer currents on the internal resistance (generator and lines) of the supplying network with the consequence of an undesired voltage distortion of the mains voltage is understood as a network feedback. The dimmer circuit described is characterized by a sinusoidal current consumption (low harmonic content) and by a high power factor.

The current three-phase networks are designed so that all 4 conductors L1, L2, L3 and N are laid with the same cross-section. The current in the neutral conductor is 0 in the case of ohmic loads (power factor 1) in a three-phase system. If many or very large consumers with a poor power factor are present in an installation, the N conductor may be overloaded. It is therefore desirable to have a power factor of more than 0.95. The power factor is the ratio of active power to apparent power.

Disadvantageously, with a dimmer circuit according to DE 44 33 552 B4, an electrical consumer with a low voltage requirement can only be controlled by means of a transformer having a loss.

The object of the invention is to provide a dimmer circuit, the netzrückwirkungs- poor, has a high power factor and is suitable for electrical loads with different voltage requirements.

This object is achieved by the feature combination of claim 1. Further advantageous embodiments can be found in the dependent claims. In particular, such a dimmer circuit allows a change and regulation of the load parameters. By changing the output voltage of the dimmer, the brightness of a halogen lamp can be controlled. When the input voltage changes, the dimmer keeps the voltage at the lamp constant. It is the use of lamps with different lamp voltage allows.

In this context, the term power control used herein means a control for influencing the power. In this respect, a power regulation also includes, in particular, a voltage regulation or a current regulation.

In this case, the half-bridge converter advantageously comprises two capacitors connected in series between the outputs of the rectifier and a second connection point arranged between the capacitors, so that the electrical load can be switched between the first and the second connection point. By the switching elements thus the voltage of the capacitors is alternately switched to the electrical load. In this case, the capacitors can be regarded as being connected in parallel by HF technology.

In principle, any switching elements such as Triac ^'s or the like can be used. As electrical switching elements, transistors, in particular MOSFETs, bipolar transistors or IGBTs, are preferably used. Here, an IGBT (Insulated Gate Bipolar Transistor) combines the advantages of a Biolartran sistor, namely good on-state behavior, high reverse voltage and robustness, with the advantages of a field effect transistor, namely a virtually powerless control.

If the first connection point is preceded by a throttle, a voltage-free or lossless switching of the switching elements can be realized. Thus, a dimmer circuit can be constructed with a very high efficiency.

With regard to the electromagnetic compatibility (EMC), it is also advantageous if the rectifier is preceded by a noise filter. In a further preferred embodiment of the dimmer circuit, the control component is designed for a clocked control of the switching elements with variable pulse width or variable frequency. In the case of a drive with a variable frequency, the switching elements are preferably always switched when the applied voltage is equal to zero. This means that switching is lossless.

For external control of the dimmer circuit, the control component is preferably connected to an interface for data or signal exchange with an external control device.

In a preferred application, the above-described dimmer circuit of a halogen lamp in a movable headlight, in particular for stage lighting, upstream and in particular designed as part of the headlamp. Such headlamps are commonly referred to as "moving heads" and allow targeted alignment of a particular colored light beam of variable intensity for stage lighting, and are used as an important part of lighting technology for shows, theater, presentations, concerts and the like.

The principle of operation and embodiments of the invention will become apparent from a drawing and the following description. Showing:

FIG. 1 shows schematically the structure of a dimmer circuit with a half-bridge converter,

FIG. 2 shows a simplified overall circuit diagram of the half-bridge converter,

Figure 3: in a graph different voltage waveforms at the half-bridge converter.

FIG. 4: an equivalent circuit diagram during the discharge of the capacitor, FIG. 5: an equivalent circuit diagram during the source function of a series-connected choke,

Figure 6: in a graph, the current flow through the load and

Figure 7 schematically a movable headlight In Fig. 1, the basic structure of an embodiment of the aforementioned dimmer circuit is apparent. To comply with a radio interference suppression, an EMC filter 1 is connected upstream of a rectifier 2 on the input side. The rectifier 2 is used to convert the AC voltage from the grid into a DC voltage. In the DC voltage circuit, a half-bridge converter 3 is connected, which comprises two series-connected electrical switching elements T1 and T2. Between these switching elements T1, T2 is a first connection point 4 for connection of an electrical load 5, here a halogen lamp.

The half-bridge converter 3 further comprises two capacitors C1 and C2 connected in series between the outputs of the rectifier 2. The electrical load 5 is in this case connected between the first connection point 4 and a second connection point 6 between the two capacitances C1, C2. About the half-bridge converter 3 for the electrical load 5, hereinafter also called load, desired voltage is generated. In series with the electrical load 5, a choke L1 and a current measuring resistor for current detection are also connected. The current detection can also be done via a current transformer.

For controlling and driving the switching elements T1 and T2, a control component 7 is further provided, which is provided with terminals for determining the load voltage UL and the load current IL. For external control interface interface 8 is provided to the user. To generate the internally required voltages, a DC / DC converter 9 is further arranged between the outputs of the rectifier 2.

In the exemplary embodiment, the two capacitances C1 and C2 were each selected to be 6.6 μF. As switching elements T1 and T2 respectively power MOSFET transistors were used. The inductor L1 had an inductance of 17 μH.

As an interface, an RS232 interface was implemented. On the one hand, the brightness of the lamp can be set externally via this interface. On the other hand, about this Interface also information about operating states of the load, in particular the lamp, or the lamp power are transmitted.

The invention is not limited to this embodiment. In principle, other components of other characteristics and other or any interfaces can be used.

During operation, the transistors T1 and T2 alternately switch the voltage from the capacitor C1 or C2 via the inductor L1 to the load 5. When the transistor T1 is turned on, the current flows from C1 via L1 to the load 5 and to the lamp, respectively. When the transistor T2 turns on, the current in the inductor L1 turns.

It flows in the load 5 and in the lamp an alternating current, which is for the life of halogen lamps advantage.

The capacitors C1 and C2 are HF - technically connected in parallel and can also be replaced by a capacitor. The control of the lamp voltage can be done by changing the pulse width of the drive signal or by changing the frequency. Regulating the frequency change, the transistors T1, T2 always turn on when the voltage across the transistors is zero. Thus, the switching is lossless (zero voltage switching). It can be used to build a dimmer with a very high efficiency. Turns off the transistor T2, drives the inductor L1, the current through the parasitic diode D1 from the transistor T1. Thus, then the voltage across the transistor is zero.

FIG. 2 shows an overall circuit diagram for the half-bridge converter 3 with input inductor L1.

It can be seen from this that the two capacitors are to be regarded as being connected in parallel by HF technology (equivalent circuit diagram). T1 is closed, C1 discharges. When T2 is closed, C2 discharges.

Normally, the capacitor C2 is designed so that it is charged to Ue / 2 on average and the voltage across it does not change during a switching period. From Fig. 3, various voltage waveforms on the half-bridge converter 3 can be seen. It can be seen the clocked control of the switching elements T1 and T2 by the voltage UG1 and UG2. The voltage curve in the half-bridge converter 3 has jumps, since the polarity of the throttle or load current IL changes. In this case, the choke L1 acts as a source during the time t _on i and drives the current through the parasitic diode of the switched switching element.

The boundary conditions apply to the calculation of the current profile in the load:

1. No significant voltage change on C ₂ for the duration of a switching period

2nd tone 1 + tone 2 = T / 2, U _c2 = U _e / 2

For the time W, the equivalent circuit diagram according to FIG. 4 applies.

The simple equivalent circuit diagram (ESB) can now be used to calculate the inductor current and thus the current through the load.

For the time toni the throttle becomes the source.

For the time from t> ton ₂ to toni, the equivalent circuit diagram according to FIG. 5 applies. The following applies:

With the initial condition for t = 0, i = 1 _ton2

Calculation of time t _on i

Substituting Equation 1 for 1 _ton2 gives:

The following applies to the calculation of the voltage at the load:

Since the load is an ohmic load, the voltage curve is equal to the current curve.

The mean over a period is:

_UR ^M _AV ^V

FIG. 6 shows the current profile in the inductor L1 and in the load or in the electrical load 5. FIG. 7 schematically shows a so-called moving head 10 which comprises a foot part 11 and a headlight 12 arranged movably thereon. For dimming the halogen lamp 13 or for setting the desired lamp intensity, a dimmer circuit 14 is arranged in the foot part 11, as shown in particular in FIG. 1 is shown.

LIST OF REFERENCE NUMBERS

EMC filters

rectifier

Half-bridge converter first connection point electrical load second connection point

control component

Interface / Interface

DC / DC converter

Moving Head

footboard

Headlamp halogen lamp

Claims

claims

1. Low-power dimmer circuit (14) for power control of an electrical load (5), in particular a lamp, with a connectable to a supply network rectifier (2), with a rectifier (2) fed half-bridge converter (3) comprising two in series between the outputs of the rectifier (2) connected electrical switching elements (T1, T2) and a first connection point (4) for the consumer (5) between the switching elements (T1.T2), and with a control member (7) which controls the switching elements ( T1, T2) in such a way that the connection point (4) is alternately connected in terms of circuit technology to one and the other output of the rectifier (2).

The dimmer circuit (14) according to claim 1, wherein the half-bridge converter (3) two in series between the outputs of

Rectifier (2) connected capacitances (C1.C2) and between the capacitances (C1.C2) arranged second connection point (6), so that the e- lectric consumer (5) between the first and the second connection point (4 or 6) is switchable.

3. dimmer circuit (14) according to claim 1 or 2, wherein the electrical switching elements (T1, T2) as transistors, in particular as MOSFET ^'s or as bipolar transistors, or as IGBT ^'s are formed.

4. dimmer circuit (14) according to any one of the preceding claims, wherein the first connection point (4) is connected upstream of a throttle (L1).

5. dimmer circuit (14) according to any one of the preceding claims, wherein the rectifier (2) an interference filter (1) is connected upstream.

6. dimmer circuit (14) according to any one of the preceding claims, wherein the control member (7) for dimming the switching elements (T1, T2) clocked with variable pulse width or variable frequency drives.

7. dimmer circuit (14) according to any one of the preceding claims, wherein the control member (7) is connected to an interface (8) for data or signal exchange with an external control device.

8. Movable headlight (12), in particular for stage lighting, with a halogen lamp (13) and with a halogen lamp (13) upstream dimmer circuit (14) according to one of the preceding claims.