WO2014187921A2

WO2014187921A2 - Assembly and a method for activating leds

Info

Publication number: WO2014187921A2
Application number: PCT/EP2014/060584
Authority: WO
Inventors: Erhard Müsch
Original assignee: Zentrum Mikroelektronik Dresden Ag
Priority date: 2013-05-23
Filing date: 2014-05-22
Publication date: 2014-11-27
Also published as: WO2014187921A3; TW201448663A

Abstract

The invention relates to an assembly and a method for activating LEDs. The problem addressed by the invention is that of specifying an assembly and a method by means of which LED lamps can be activated without flicker and in a dimmable manner, and the required circuitry complexity is reduced. Said problem is solved by the assembly in that the LED driver contains an active dampening unit, which provides an additional and activatable path for an additional current flow in the LED driver. The problem is solved by the method in that a path for an additional current flow in the LED driver is provided, which is connected after an occurrence of a switching edge in the phase control dimmer for a specified duration of time and a prevents a deactivation of a switch (triac) in the phase control dimmer by a thus increased current flow in the LED driver.

Description

Arrangement and a method for driving LEDs

The invention relates to an arrangement for driving LEDs, comprising a phase-cut dimmer, a

electronic transformer and an LED driver, which is connected to the LEDs for driving.

The invention also relates to a method for driving LEDs, in which by means of a phase-angle dimmer and an electronic transformer, a phasenangeschnit ^¬ tene voltage for driving the LEDs is generated.

The invention relates to a control for LEDs by means of a voltage from an electronic transformer for low-voltage halogen lamps, in particular with phase control dimming. Can be mentioned this as a prior art, a solution from Philips, which offers dimmable LED spotlights under the product name "Master LED Spot LV".

The usual electronic transformers for

Low-voltage halogen lamps require a minimum load for their perfect function. In particular, when operating with dimmers immediately after the edge of the phase gating a significant load on the output is required to prevent extinction of the triac in the dimmer.

Energy-saving LED lamps do not have a sufficiently high power consumption, so that additional circuitry is necessary to meet the conditions for a sufficient load on the output.

Thus, the object of the invention is a Arrangement and a method for controlling LEDs indicate with which LED lamps flicker-free and dimmable can be controlled and the necessary

Circuit complexity is reduced. According to the invention, the object is achieved in an arrangement for driving LEDs of the type mentioned above in that the LED driver includes an active damping unit, which provides an additional and controllable path for an additional current flow in the LED driver

provides.

According to the invention, after the occurrence of a

Switching edge, for example, of a triac in the phase gating dimmer for a short time increases the current consumption of the LED driver dynamically. This is done by means of a controllable additional current path in the LED driver. Thus, the extinction of the triac is prevented in the dimmer.

In one embodiment of the invention it is provided that the active damping unit is a semiconductor switch, which is connected to the control with a first control unit.

The damping unit according to the invention - also as

so-called "snubber" - can by a

Semiconductor switches, such as a transistor, are provided. The control of this semiconductor switch is effected by means of a first control unit. It is also planned to arrange the semiconductor switch in combination with other passive elements such as resistors.

In a further embodiment of the invention

provided that the LED driver has a second control unit and a switching power supply connected thereto, wherein by means of the second control unit, a dynamic increase of the current is controlled in the switching power supply. In the LED driver, a second control unit and a switching power supply are further arranged. The second control unit generates the control signals for the switching power supply. Thus, in addition to switching on an additional current path or independently of this, a dynamic increase of the

Stromes are controlled in the switching power supply. These measures lead to a further increase in the reliability of the arrangement.

According to the invention, the object is achieved in a method for driving LEDs of the type mentioned in that a path for an additional current flow in the LED driver is provided, which is switched on after an occurrence of a switching edge in the phase gating dimmer for a fixed period of time is and by an thus increased current flow in the LED driver an unwanted

Interruption in the voltage curve of the phase-cut voltage prevented.

Timed after the occurrence of a switching edge in the phase gating dimmer, a path for an additional current flow in the LED driver is switched on, wherein the

Switching is done in such a way that the switching state of the triac is obtained in the dimmer and predetermined limits,

for example, for a maximum current, not be exceeded. In a particular embodiment of the invention, it is provided that the fixed duration of the short-term additional current flow in the LED driver is a maximum of 100.

By way of example, the duration in the generation of the

additional current flow in the LED driver can be set to a maximum of 100. A restriction to this duration is not present in the present invention.

The invention will be described below with reference to an embodiment Example be explained in more detail. In the associated

Drawings shows

Fig. 1 shows a voltage-time course in the operation of a

Arrangement for driving LEDs with a phase control,

Fig. 2 is a block diagram of a phase gated dimmer with an electronic transformer and a

LED driver with active snubber according to the invention and dynamic current control and Fig. 3 shows an exemplary inventive

Input current curve of the LED driver as

Dynamic reaction to a switching edge during phase control in a current-time diagram.

In a method of driving LEDs is

suggested that

1. an active "snubber" briefly realizes a high load current and / or

2. a dynamic increase of the peak current in the

Switching power supply of the LED driver also realized an increased load current, however, in the

Rate of increase of the current is limited by the inductance of the converter.

Both measures can be used individually or advantageously together. The invention offers the advantage that even individual LED lamps can be controlled flicker-free and dimmable, from suitable for operation on phase control dimmers electronic transformers.

The line filter in the dimmer produces a resonant oscillation when the triac is switched on, which is instantaneous Increasing the voltage leads to the electronic transformer, as shown in the figure 1. These

Overvoltage is rectified and causes the transformer to take no current from the supply until the DC voltage falls below the instantaneous value of the supply

Mains voltage has dropped. This process must be done quickly to prevent the triac from shutting down. For this purpose, a correspondingly high load current at the output of the transformer is required. The invention prevents an unwanted shutdown of the triac and thus an unwanted course of the generated phase-cut voltage for controlling the LEDs.

FIG. 1 shows a sinusoidal course of a

Input or mains voltage in the representation of a dot-and-dot line. Also shown in each half-wave is a phase angle, ie the time to which

For example, a triac is switched in a phase gating dimmer 1.

In addition, a generated by means of rectification waveform of a pulsating DC voltage in the electronic transformer 2 in the form of a dash-and-dash line.

Below is a description of the arrangement in Figure 2, which shows an example arrangement for the invention described only with the essential elements. One

Phase gating dimmer 1 with a triac as a switch, has a line filter consisting of an inductor and a capacitor. When switching the triac, this filter generates a resonance oscillation, which is superimposed on the voltage applied to the input side and shown in FIG. At the load, there is a corresponding voltage increase.

Electronic transformers 2 ("e-transformers") for Halogen lamps convert the applied mains voltage

Rectification into a pulsating DC voltage from which in most cases a resonance converter is fed. Such a pulsating DC voltage is shown in FIG. The overvoltage at the input generates a rectifier behind the rectifier shown in FIG

Voltage that is higher than the instantaneous mains voltage, so that after the decay of the filter resonance, the capacitors in the e-transformer 2 must first be discharged to below this instantaneous voltage, before again power from the grid

is recorded. This process must be done very quickly to prevent extinction of the triac. For this it is necessary that the e-transformer 2 is heavily loaded on the output side. Energy-saving LED lamps do not have a sufficiently high power requirement. To solve it is therefore proposed, after the switching edge of the triac and the corresponding increase in the secondary voltage at the transformer for a short period of time to increase the power consumption dynamically. It is advantageous to increase the current of the converter that feeds the LEDs, but the current increase is due to its

Inductance limited and possibly not fast enough. An active damping unit 4 according to the invention ("active

Snubber ") therefore provides a spontaneous path for the

Current flow available. It is a semiconductor, possibly in combination with other passive elements, such as resistors and

Capacitors, is briefly actuated and the

Supply current increased. In principle, the snubber could be realized only with passive components, for example, in the known RCD (resistor, capacitor, diode) variant, but then the required capacitor and thus the space required very large. In particular, when it is to be dispensed with electrolytic capacitors for life reasons, the available space would be exceeded eg in the base of a GU5.3 lamp. Therefore, a realization of the active damping unit 4 by means of semiconductor devices is particularly advantageous.

In addition or as an alternative to this method, it is provided to increase its power consumption in terms of time and value by means of a dynamic control of the converter. Basically, the snubber alone the

required load current for the necessary time

However, this leads to an increase in

Power loss while the dynamic control of the

Converter is converted into a corresponding current for the LEDs.

An exemplary input current profile of the LED driver 3 as a dynamic response to a switching edge in

Phase angle is shown in FIG.

Shown is a spontaneous onset snubber stream as a dash-and-dash line. One through the inductance

Limited current of the converter is shown as a dot-dot line in its time course. The resulting sum current in the array is shown as a black solid line. The time range of the dynamic current increase is in an embodiment, for example, in the order of 100 ps. Arrangement and a method for driving LEDs

LIST OF REFERENCE NUMBERS

1. Phase cut dimmer

2. electronic transformer

3. LED driver

4. active damping unit

5. first control unit

6. second control unit

7. Switching power supply

Claims

Arrangement and a method for driving LEDs

1. Arrangement for driving LEDs, comprising a

Phase cut dimmer (1), an electronic

Transformer (2) and an LED driver (3), which is connected to the LEDs for driving, characterized in that the LED driver (3) includes an active damping unit (4), which provides an additional and controllable path for one

provides additional current flow in the LED driver (3).

2. Arrangement according to claim 1, characterized

characterized in that the active damping unit (4) is a semiconductor switch which is designed to be controlled by a first control unit (5).

connected is.

3. Arrangement according to claim 1 or 2, characterized

in that the LED driver (3) has a second control unit (6) and a switched-mode power supply unit (7) connected thereto, wherein a dynamic increase of the current in the switched-mode power supply unit (7) is controlled by means of the second control unit (6).

4. A method for driving LEDs, wherein by means of a phase gated dimmer (1) and a

electronic transformer (2) a

Phase-cut voltage for driving the LEDs is generated, characterized in that a path for an additional current flow in the LED driver (3) is provided, which is switched on after an occurrence of a switching edge in the phase gating dimmer (1) for a fixed period of time and by a thus increased current flow in the LED

Driver (3) an unwanted interruption in the

Voltage profile of the phase-cut voltage prevents. Experienced according to claim 4, characterized

characterized in that the fixed duration of the short-term additional current flow in the LED driver (3) is a maximum of 100.