EP2510750B1 - Driver circuit for an led - Google Patents

Description

The invention relates to a driver circuit for an LED according to the preamble of patent claim 1 and a method for driving an LED according to the preamble of patent claim 12.

Technical area

Such driver circuits are used in lighting systems to achieve a colored or flat lighting of rooms, paths or escape routes. Usually, the bulbs are driven by operating devices and activated as needed. For such illumination, organic or inorganic light emitting diodes (LED) are used as the light source.

State of the art

For lighting, instead of gas discharge lamps and incandescent lamps, light-emitting diodes are also increasingly being used as the light source. The efficiency and luminous efficacy of light-emitting diodes is being increased more and more so that they are already being used in various general lighting applications. However, light emitting diodes are point sources of light and emit highly concentrated light.

However, today's LED lighting systems often have the disadvantage that due to aging or by replacing individual LEDs or LED modules, the color output or the brightness can change. In addition, the secondary optics has an impact on the thermal management, as the heat radiation is hindered. In addition, it may be due to aging and Heat effect to a change in the phosphor of the LED come.

A change in brightness is often only possible with a complex control circuit, a simple connection to standard dimmers is not given, as it comes in conjunction with most dimmers to a flicker of light or dimmers do not work. In addition, the change in color and brightness is hardly possible separately.

The EP 1 871 144 A1 describes a driver circuit for LEDs. A current sensor detects a current and returns a current indicating signal via an optocoupler to a driver control.

The DE 102 39 449 A1 and the DE 10 2006 025 597 A1 disclose lights that are designed for touch control. A touch sensor is provided for detecting the touch.

The WO 2005/022963 A1 , which serves as a basis for the preamble of the independent claims, discloses a lighting device with a capacitive proximity sensor.

Presentation of the invention

It is the object of the invention to provide a luminous means and a method which enable a trouble-free and energy-saving operation by means of a luminous means with light-emitting diodes without the disadvantages mentioned above or with a clear reduction of these disadvantages.

This object is achieved according to the invention for a generic device and a method by the characterizing features of claim 1 and claim 12. Particularly advantageous embodiments of the invention are described in the subclaims.

The solution according to the invention for a device for operating LEDs (organic or inorganic light-emitting diodes) is based on the idea that a driver circuit for an LED has a connection for a mains voltage, a filter circuit and a rectifier, an inductance and a switch. The inductor is magnetized when the switch is closed, and the inductor is demagnetized when the switch is open, and at least during the demagnetization phase, the current through the inductor feeds the LED.

The solution according to the invention relates to a device comprising a driver circuit for at least one LED, comprising a connection for a mains voltage, a rectifier and a filter circuit, a latching element, an inductance and at least one switch, wherein the inductance is up-demagnetized by high-frequency clocking of the switch and the inductor feeds the LED, the switch is driven by a control circuit, the control circuit being coupled to a sensor device and the sensor device enabling non-contact control of the brightness and color of the driver circuit.

The solution according to the invention also relates to a method for controlling at least one LED, wherein the at least one LED is driven via a driver circuit, wherein sensorless contactless control of the brightness and the color of the LED is made possible by means of appropriate control via the driver circuit. The non-contact control can be done by an evaluation of a capacitive coupling, and depending on the capacitive coupling, the brightness and the color of the LED can be adjustable.

The solution according to the invention also relates to a luminous means for an LED, with a base for the use of the luminous means in a commercial lamp base, comprising a device according to the invention.

In this way, it is possible to achieve a very consistent and uniform illumination of a surface by a light source with light-emitting diodes, which is controllable in a simple manner in the brightness and color.

Description of the preferred embodiments

• Fig. 1 zeigt eine erste Ausgestaltung einer erfindungsgemäßen Vorrichtung.
• Fig. 2 zeigt eine zweite Ausgestaltung einer erfindungsgemäßen Vorrichtung.
• Fig. 3 und 4 zeigen weitere Ausgestaltungen einer erfindungsgemäßen Vorrichtung.
• Fig. 5 zeigt eine weitere Ausgestaltung einer erfindungsgemäßen Vorrichtung.

The invention will be explained in more detail with reference to the accompanying drawings.

• Fig. 1 shows a first embodiment of a device according to the invention.
• Fig. 2 shows a second embodiment of a device according to the invention.
• Fig. 3 and 4 show further embodiments of a device according to the invention.
• Fig. 5 shows a further embodiment of a device according to the invention.

The invention is based on a first embodiment according to Fig. 1 explained with a driver circuit for an LED.

The driver circuit for an LED has a connection for a mains voltage, a filter circuit and a rectifier, an inductance and a switch.
The inductor is magnetized when the switch is closed, and the inductor is demagnetized when the switch is open, and at least during the demagnetization phase, the current through the inductor feeds the LED.

The switch S1 is preferably opened only when the current through the switch S1 has reached a predetermined threshold.

The current through the switch S1 can be detected by means of a current detection Ip (for example, a current shunt). The turn-off duration of the switch S1 may be dependent on the detected amplitude of the current through the LED.

The switch-off duration of the switch S1 can be dependent on the degaussing current.

The inductance L2 can feed a smoothing circuit C2 during its demagnetization. The inductance L2 may have a secondary winding. The clocked inductor L2 of the driver circuit has a secondary winding L2s which is magnetically coupled to the primary winding L2p of the inductor L2.

The driver circuit can be designed as isolated flyback converter. The driver circuit can also be designed as a resonant and isolated half-bridge converter having two controllable switch.

Thus, a driver circuit for an LED is provided, comprising a connection for a mains voltage, a rectifier GR1 and a filter circuit L1, a latching element, an inductance L2 and at least one switch S1, wherein the inductance L2 is up-demagnetized by high-frequency clocking of the switch S1 and the inductor L2 feeds the LED, and the switch S1 is driven by a control circuit U1.

The control circuit U1 is coupled to a sensor device SV, and the sensor device SV allows a non-contact control of the brightness and / or the color by means of the driver circuit.

The contactless control of the sensor device SV is performed by an evaluation of a capacitive coupling. Depending on the capacitive coupling, the brightness of the driver circuit can be adjustable by changing the control signal of the switch S1 by the control circuit. The capacitive coupling takes place by a hand movement, preferably in the vicinity of the driver circuit or the LED lamp.

The sensor device SV may have a first capacitance, which may change its charge due to a capacitive coupling (to change the brightness). The sensor device SV evaluates the capacitive coupling based on a comparison measurement between the first capacitance and a reference capacitance.

The sensor device SV can output the capacitive coupling, which is dependent on the comparison measurement between the first capacitance and a reference capacitance, as an evaluation signal, which is evaluated by the control circuit U1.

Depending on the monitored evaluation signal of the sensor device SV, the control circuit (U1) can change the frequency and / or the duty cycle when the switch S1 is actuated. The sensor device SV evaluates by means of the evaluation of the capacitive coupling a detected hand movement as a control signal.

The detected hand movement can be evaluated in terms of its duration, and this period can be evaluated as information for the desired change in the brightness of the LED.

The detected hand movement is evaluated with regard to its intensity of the hand movement, and this intensity is evaluated as information for the desired change in the brightness and / or color of the LED. The change of color can also mean a change in the color temperature or the color location.

Thus, a light source for an LED can be constructed, with a base for the use of the light source in a commercially available lamp base, comprising a driver circuit and a sensor device SV according to the invention.

The non-contact control of the sensor device SV and thus the LED has the advantage that no contact of a control element such as a touch panel is necessary. This has the advantage that, on the one hand, the user can directly control the LED illuminant without running the risk of having to touch a hot light source; moreover, external controls can be dispensed with by integrating the sensor device SV into the illuminant. In addition, there is often the problem with bulbs that they are not directly accessible to the user, since they are installed in a lamp and due to an optics or a housing direct contact is not possible.

Non-contact control can also be used to specify or change configuration settings. For example, the non-contact control can also be used for address assignment, in that the illuminant is then assigned an address in an addressing mode when a non-contact control is detected there.

The recorded configuration settings can be stored in a memory and thus permanently available for use. In this way, certain scenes can be defined. For example, in a configuration mode, which is achieved by a certain predetermined hand movement, certain scenes can be defined, which can then be retrieved later by a corresponding hand movement. It can be done during the configuration, the setting of the scenes in several steps and thus by relatively complicated hand movements, while the subsequent scene call by a certain hand movement, but can be relatively simple and short, can take place.

Thus, a method for driving an LED is made possible, wherein the LED is driven by a driver circuit, wherein via a sensor device SV, a non-contact control of the brightness and / or the color is made possible by means of the drive via the driver circuit.

The non-contact control is performed by an evaluation of a capacitive coupling, and depending on the capacitive coupling, the brightness and / or the color by means of the driver circuit is adjustable.

The switch S1 can be driven, for example, by an integrated circuit for a power factor correction. The monitoring circuit U1 may include a power factor correction control circuit.

The inductance L2 may be a transformer L2p, L2s, which serves as a potential-separating member.

In this case, the primary winding L2p of the transformer is connected in series with the switch S1. The secondary winding L2s magnetically coupled to the primary winding L2p is connected to a rectifier D2 and a smoothing circuit C2 to which the LED can be connected. The rectifier D2 at the secondary winding L2s of the transformer can be formed by a diode D2 or by a full-wave rectifier.

The invention will be described below on the basis of further exemplary embodiments Fig. 2 . Fig. 3 . Fig. 4 and Fig. 5 explained with another driver circuit for an LED. Here, in addition to the contactless control (as based on the Fig. 1 explained) a network-based control by means of a dimmer done.

The driver circuit has a connection for a mains voltage, which is followed by a rectifier GR1 and a filter circuit L1 and a buffer element. This is followed by an inductance L2 and a switch S1.
The inductance L2 is magnetized when the switch S1 is closed, and the inductance L2 is demagnetized when the switch S1 is opened, and at least during the demagnetization phase, the current through the inductance L2 feeds the LED.

The driver circuit can be constructed as a boost converter circuit or as a flyback converter circuit. Advantageously, the flyback converter circuit or the boost converter circuit is designed to be isolated, ie, the clocked inductance L2 of the driver circuit has a secondary winding L2s, which is magnetically coupled to the primary winding L2p of the inductance L2.

A current detector, preferably a unidirectional decoupling element, is included between the rectifier GR1 and the latching element C1.

According to the examples of Fig. 2 and 3 For example, the decoupling element can be formed as a current detector by a diode D1. However, it is also possible to use a full-wave rectifier DV1 as decoupling element.

At the output of the rectifier GR1 there is a bypass circuit R40, Q4 which is deactivated when the current detector (for example the decoupler) passes a current.

Thus, a bypass circuit R40, Q4 is always activated when a current flows into the driver circuit for an LED. A current in the driver circuit for an LED always flows when a current flows through the rectifier GR1 via the inductance L2 and the switch S1 or into the intermediate storage element. The decoupling member thus acts as a current detector.

As soon as a current flows via the inductance L2 and the switch S1 or into the intermediate storage element via the rectifier GR1, a voltage drops across the decoupling element which is only slightly higher than the voltage across the intermediate storage element (ie the voltage behind the decoupling element). This voltage across the decoupling element can be monitored. This monitoring can be done by a monitoring circuit U1. This monitoring circuit U1 may be, for example, an integrated circuit. The monitoring circuit U1 can activate or deactivate the bypass circuit R40, Q4 as a current detector depending on the monitoring of the decoupling element.

The monitoring circuit U1 can detect, for example, only the voltage before the decoupling element or the voltage difference across the decoupling element (preferably by a respective voltage measurement in front of and behind the decoupling element). The monitoring circuit U1 can also control the switch S1.

The decoupling element as a current detector can be formed by a diode D1. However, it is also possible to use a full-wave rectifier DV1 as decoupling element.

The driver circuit may be connected to a commercially available dimmer, and the bypass circuit R40, Q4 may be activated during the phases in which the dimmer cuts off a portion of the phase to provide residual current through the bypass circuit R40, Q4 and the inductor L2 and the switch S1 to lead and thus burden the dimmer.

The buffer element can be replaced by a valley fill circuit ( Fig. 3 ) or else by a smoothing capacitor C1 ( Fig. 2 ) are formed.

The switch S1 can be switched on whenever a demagnetization of the inductance L2 is detected. However, a switch-on can always take place only when the inductance L2 is de-magnetized, and a certain period of time can also be between the time of demagnetization and the restarting.

The switch S1 can be driven, for example, by an integrated circuit for a power factor correction. The monitoring circuit U1 may include a power factor correction control circuit.

The inductance L2 may be a transformer L2p, L2s, which serves as a potential-separating member. In this case, the primary winding L2p of the transformer is connected in series with the switch S1. The secondary winding L2s magnetically coupled to the primary winding L2p is connected to a rectifier D2 and a smoothing circuit C2 to which the LED can be connected. The rectifier D2 at the secondary winding L2s of the transformer can be formed by a diode D2 or by a full-wave rectifier.

The on and / or off duration of the switch S1 may be dependent on the detected amplitude of the current through the LED. Preferably, however, the switch-on and / or switch-off duration of the switch S1 does not decrease to zero or close to zero. In a simple variant, for example, a limitation of the current through the LED can be done by limiting the duty cycle.

The inductance L2 can feed a smoothing circuit C2 during its demagnetization, this smoothing circuit C2 can be, for example, a capacitor C2 or an LC or CLC filter.

The bypass circuit R40, Q4 may be formed by a resistor R40 in series with a switch Q4.

However, the bypass circuit can also have a current source (constant current source) as a bridging circuit. An example of a current source (constant current source) is in Fig. 4 shown. In Fig. 4 only a section of the device according to the invention is shown.

The current detector is formed here by current monitoring element R34. Depending on the current flow through the current monitor R34, the monitor circuit U1 (formed by a transistor Q5 and a resistor R30 connected to an internal power supply Vcc) can activate or deactivate the bypass circuit. As soon as sufficient current flow through the current detector (ie current monitor R34) is detected, the bypass circuit is deactivated. The current flow through the current monitoring element R34 is the current which flows via the rectifier GR1 into the inductance L2 and the switch S1 or the buffer element.

In the example according to Fig. 4 is the monitoring circuit U1 discrete, but it can also as in the examples of Fig. 2 and 3 be designed as an integrated circuit. When using an integrated circuit as a monitoring circuit U1 further functions such as the control of the switch S1 can be integrated with.

The bypass circuit is according to Fig. 4 formed by a current source (constant current source).
The current source (constant current source) is formed in detail by the transistors Q4 and Q6 and the resistors R40, R27 and R29.

The bypass circuit may be as in Fig. 4 represented via a full-wave rectifier D3 via the filter circuit L2 to the terminal for a mains voltage, parallel to the rectifier GR1 be connected.

The rectifier, via which the bypass circuit R40, Q4 is connected to the connection for a mains voltage, can either be the same rectifier, via which a current flows into the inductance and the switch or the buffer element (ie the rectifier GR1, see FIG Fig. 2 and 3 ), or another rectifier D3 may be connected in parallel with this first rectifier GR1 (see Fig. 4 ) to be available.

Thus, a method for driving an LED is possible, wherein the LED is driven by a driver circuit, and wherein the driver circuit is fed from a terminal for a mains voltage via a filter circuit L1 and a rectifier GR1, and wherein the driver circuit comprises a latch element, an inductance L2 and a switch S1, and wherein a bypass circuit R40, Q4 provided at the output of the rectifier GR1 is deactivated when a current flows into the driver circuit via the rectifier GR1.

Thus, a light source for an LED can be constructed, with a base for the use of the light source in a commercial lamp base, comprising a device according to the invention.

In Fig. 5 Another driving option for a driver circuit for an LED is shown.

The driver circuit may be connected to a commercially available dimmer, and the switch S1 may be closed during the phases in which the dimmer cuts off a portion of the phase to pass a residual current across the inductor and the switch S1 and thus load the dimmer ,

The switch S1 can be switched on whenever a demagnetization of the inductance is detected. However, it is always possible to switch on only when the inductance has been de-magnetized, and it may also take a certain amount of time between the time of demagnetization and restarting.

The inductance may be a transformer which serves as a potential-separating member.

The predetermined threshold may depend on the current amplitude of the supply voltage. In a simple variant, for example, if the supply voltage exceeds a certain value, an increase of the threshold value can take place.

The inductance can feed a smoothing circuit during its demagnetization, this smoothing circuit can be, for example, a capacitor or an LC or CLC filter.

In this example, the switch S1 may always remain closed in the case of a control via a dimmer, as long as the current through the switch S1 has not reached a predetermined threshold, in addition there may be an activatable bypass circuit which is activated only when via the current detector sufficient current flow is detected.

In this way, the bypass circuit can be designed to produce little additional loss in its activation.

It can also be the embodiment of the Fig. 1 with those of Fig. 2 to 5 be combined.

The device may also comprise a driving circuit for an LED, comprising a connection for a mains voltage, a rectifier GR1 and a filter circuit, a latching element C1, an inductance L2 and a switch S1, wherein high-frequency clocking of the switch S1, energy via the inductance to the Illuminant can be transmitted, and at the output of the rectifier GR1, a bypass circuit R40, Q4 may be present, which is activated when the light-emitting diode LED is not in operation. This may be the case, for example, when no mains voltage is applied. The bridging circuit R40, Q4 can thus be designed so that it is only deactivated when an operation of the light source, so the LED is. In this way, a better compatibility with so-called Netzfreischaltern can be achieved. In addition, during operation of the light source, the bypass circuit R40, Q4 can be deactivated only in the phases when a current flow through the current detector is detected.

The basis of the Fig. 2 to 5 shown additional features can also be used as individual extensions to the embodiment according to the Fig. 1 be supplemented.

It can thus be formed according to the invention, a light source for an LED, with a base for use of the light source in a commercial lamp base, comprising a device according to the invention.

Claims (12)

1. A device for operating LEDs, comprising a driver circuit for at least one LED, wherein the device for operating LEDs comprises a sensor device (SV), to which a control circuit (U1) is coupled,
   wherein
   the driver circuit for the at least one LED has a rectifier (GR1) and a filter circuit (L1), an intermediate storage element, an inductance (L2) and at least one switch (S1), wherein
   the driver circuit is designed such that the inductance (L2) is magnetized and demagnetized by high-frequency clocking of the switch (S1) and the inductance (L2) supplies the LED,
   wherein the driver circuit has the control circuit (U1) for controlling the at least one switch (S1), characterized in that the sensor device (SV) is designed for the contact-free detection of a hand movement by capacitive coupling,
   that the driver circuit is designed, in order to carry out a change of the control of the at least one switch (S1) depending on an evaluation of the capacitive coupling, in order to change the luminosity and/or a color of the LED, and
   that the device is designed, in order to evaluate the detected hand movement in respect to an intensity of the hand movement and in order to evaluate the intensity of the hand movement as information for a desired change of the luminosity and/or the color of the LED.
2. A device according to Claim 1,
   characterized in
   that the sensor device (SV) is designed, in order to detect the hand movement close to the driver circuit by the capacitive coupling in a contact-free manner.
3. A device according to Claim 1 or Claim 2,
   characterized in
   that the sensor device (SV) has a first capacitance, the charge of which changes on the basis of the capacitive coupling.
4. A device according to Claim 3,
   characterized in
   that the sensor device (SV) is designed, in order to evaluate the capacitive coupling by means of a comparison measurement between the first capacitance and a reference capacitance.
5. A device according to Claim 4,
   characterized in
   that the sensor device (SV) is designed, in order to output an evaluation signal for the evaluation to the control circuit (U1) depending on the comparison measurement between the first capacitance and the reference capacitance.
6. A device according to Claim 5,
   characterized in
   that the control circuit (U1) changes the frequency and/or duty ratio when controlling the at least one switch (S1) depending on the monitored evaluation signal of the sensor device (SV).
7. A device according to any one of Claims 1 to 6,
   characterized in
   that the device is designed, in order to evaluate the detected hand movement in respect to the time period and in order to evaluate the time period as information for a desired change of the luminosity and/or the color of the LED.
8. A device according to any one of Claims 1 to 7,
   characterized in
   that the device is designed, in order to change both the luminosity as well as the color depending on the detected hand movement.
9. A device according to any one of Claims 1 to 8,
   characterized in
   that the driver circuit is configured as an isolating flyback converter.
10. A device according to any one of Claims 1 to 8,
    characterized in
    that the driver circuit is configured as a resonant and isolated half-bridge converter.
11. A lighting means with LEDs, with a base for the insertion of the lighting means into a commercially available lamp base, having a device according to any one of the preceding claims.
12. A method for the control of at least one LED, wherein the at least one LED is controlled via a driver circuit,
    wherein a sensor device (SV) detects a hand movement by evaluation of a capacitive coupling in a contact-free manner,
    characterized in
    that a luminosity and/or a color of the LED is changed depending on the evaluation of the capacitive coupling by means of the driver circuit,
    that the detected hand movement is evaluated in respect to an intensity of the hand movement and
    that the intensity of the hand movement is evaluated as information for a desired change of the luminosity and/or the color of the at least one LED.

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