DE102018124376B4 - Multi-channel LED driver - Google Patents

Abstract

LED driver (1) for an LED lamp or luminaire with two or more LEDs (50), the LED driver (1) having:
a voltage input (11a, 11b) arranged to connect the LED driver (1) to an AC power source;
a rectifier circuit (12) for converting the alternating current received from the voltage input (11a, 11b) into a direct current to be supplied to the LEDs (50);
a switching component (40) connected between the rectifier circuit (12) and the LEDs (50) and comprising two or more switches (41), each switch associated with an individual LED (50) or a group of the LEDs (50) and set up to switch them;
a PWM component (30) which is connected to the switching component (40) and set up to generate a PWM signal for actuating the switches (41) of the switching component (40), wherein
the switching component (40) and the PWM component (30) are each designed as a multi-channel component.

Description

technical field

The invention relates to an LED driver for an LED lamp or luminaire with two or more LEDs, the LED driver having a voltage input which is set up to connect the LED driver to an AC power source, and a rectifier circuit for converting the Voltage input received AC voltage in a DC voltage to be supplied to the LEDs.

background

With the advent of LED bulbs or lights, efficient and durable means of lighting are available. Compared to other traditional lighting devices, such as fluorescent lamps, the materials of LED lamps are safer because, for example, no mercury is required.

Typically, LED lamps or luminaires include or are associated with an LED driver that converts the AC input power from a conventional power supply or electronic ballast (e.g. when used with conventional fluorescent lampholders) into appropriate ratings for driving the LEDs. Converts DC voltage and current.

Conventional LED drivers implement a two-tier topology to achieve high power factor (>0.9) and high current to be delivered to the LED strings. The first stage provides an AC/DC conversion, e.g. realized via a BUCK-PFC stage to get a suitable power factor, and the second stage provides a DC/DC conversion, e.g. via a BUCK-DC/DC -Stage realized to achieve required LED current. To enable applications that require the operation of multiple LED strings, such as mixing colors, switches can be provided in parallel with each LED string to control the current through each LED string.

Usually, the LED driver uses multiple DC/DC converters to drive multiple LED strings, and the number of DC/DC converters is equal to the number of LED strings. As a result, the structural complexity is considerable.

In addition, the two-stage implementation - AC/DC conversion and DC/DC conversion - also requires a number of electronic components. On the other hand, currently available multiple LED string drivers based on a single-stage topology are limited to supplying the same LED voltage to each LED string, which leads to limitations in LED design.

Furthermore, the voltage available for all LED strings is limited by the maximum output voltage of the second stage. This limitation is difficult to circumvent and poses a problem of low efficiency and a thermal problem due to the operation based on low voltage and high current.

the US 2011/0248640 A1 describes a lighting application with LEDs. the WO 2013/110052 A1 describes an LED lighting system with uniform brightness. the US 2015/0115816 A1 describes an LED lighting device and a method for operating the same. In the TEXAS INSTRUMENTS publication: "Power Factor Correction Using the Buck Topology - Efficiency Benefits and Practical Design Considerations. Texas Instruments Power Supply Design, Seminar 2011” describes the basics of step-down circuits with power correction.

Presentation of the invention

An object of the present invention is to provide an improved LED driver, in particular an LED driver that is compact and capable of realizing a wide range of possible input and output voltages.

The object is achieved by an LED driver according to claim 1. Preferred embodiments are defined in the dependent claims, the general description of the invention and the description of specific embodiments and the drawings.

The LED driver according to the invention is part of, or suitable for being connected to, an LED lamp or luminaire with two or more LEDs. The LED driver is capable of individually driving the multiple LEDs or groups thereof.

The LED driver has a voltage input configured to connect the LED driver to an AC power source and a rectifier circuit for converting the AC power received from the voltage input to DC power to be supplied to the LEDs. The LED driver also has a switching component that includes two or more switches. Each switch is associated with and configured to switch an individual LED or a group of the LEDs. The switching component is between the Connected or switched rectifier circuit and the LEDs. In other words, the switches are associated with a plurality of channels. Each channel can be connected to a single LED or a group of LEDs. The switching component receives the DC voltage provided by the rectifier circuit and the switches operate the channels, ie the LEDs, individually. The LED driver further includes a PWM component connected to the switching component and configured to generate a PWM signal for actuating the switches of the switching component.

The LED driver according to the invention integrates a multi-channel driver into an AC/DC converter, providing a compact single-stage driver that can individually address and drive multiple LEDs or LED groups. The LED driver can be set for different LED configurations, whereby each LED can be controlled individually, i.e. the voltages and/or currents for operating the LEDs can be selected and supplied individually. This is achieved by adjusting the PWM signal, preferably its duty cycle, to operate the switches. Furthermore, the LED driver implements a wide range of possible input and output voltages. In particular, the technical solution is able to deal with comparatively low DC voltages. The LED driver combines flexible design, precise current control, scalability in terms of channel count expansion, and adaptability to different applications.

The PWM component preferably comprises an ASIC and a bus line which connects the ASIC to the switches, the ASIC being set up to output the PWM signal to the bus line. This means that variable output voltages and currents can be implemented using a compact and cost-effective design.

Preferably, the ASIC is arranged to receive user input, preferably wirelessly, for determining the PWM signal, preferably the duty cycle thereof. Here, channel addressing and control is achieved by adjusting the PWM signal generated by the ASIC based on user input, thereby simplifying the operation of the LED driver.

The LED driver preferably also has a buck converter, which preferably contains the rectifier circuit. The use of a buck topology enables the LED driver to have a high power factor.

Preferably, only a single buck converter is switched or connected between the voltage input and the switching component, as a result of which a single-stage buck topology is implemented.

Preferably, the switches of the switching component are implemented by one or more transistors and/or relays, thereby minimizing and simplifying the driver topology.

Preferably, the switching component includes two or more capacitors connected in parallel with the LEDs to reduce a ripple current supplied to the LEDs. Preferably, the switching component further includes two or more diodes connected in series with the capacitors. Preferably, a set of a capacitor and a diode is connected in parallel with a corresponding switch.

character list

• the 1 12 shows a schematic diagram of a circuit structure of a single stage LED driver according to a first embodiment.
• the 2 12 shows a schematic diagram of a circuit structure of a single stage LED driver according to a second embodiment.

Detailed description of preferred embodiments

Preferred embodiments of the invention are described below with reference to the drawings. Here, elements that are identical or similar, have the same or similar effect, are provided with the same reference symbols in the figures. Where appropriate, the description of such elements has not been repeated in order to avoid a redundant description.

the 1 FIG. 1 shows a schematic circuit diagram of a single-stage LED driver 1 according to a first embodiment. The LED driver 1 has a buck converter 10 and a control unit 20 which includes a PWM component 30 and a switching component 40 . The LED driver 1 is connected or connectable to LEDs 50 or groups of LEDs 50 . In the following, the term "LED" is used to designate both an individual LED and a group or chain of LEDs. The LEDs 50 can form an LED load. The LEDs 50 are not necessarily part of the LED driver 1. In conjunction with the LEDs 50, the LED driver 1 forms an LED lamp or luminaire or illuminant.

The LED driver 1 can be connected to a power source that provides an AC voltage. For this purpose, the buck converter 10 receives alternating current via voltage inputs 11a and 11b. The inputs 11a, 11b can be connected or can be connected to a power supply, for example.

The buck converter 10 is set up to convert the AC voltage into a constant base current for the operation of the LEDs 50 . The buck converter 10 has a rectifier circuit 12 for this purpose. The rectifier circuit 12 can be implemented via a diode bridge, as in FIG 1 shown. The buck converter 10 also uses a switch 13 and a buck PFC control IC (Integrated Circuit) 14 to adjust the DC power output from the rectifier circuit 12 to achieve the desired power factor. The IC 14 may comprise or be implemented by a BPS233x series integrated circuit, for example. Gate of the switch 13 is connected to the IC 14. The drain of switch 13 may be connected to circuitry for outputting the desired direct current. Source of the switch 13 can be connected to GND (ground). The switch 13 may be an n-type field effect transistor. The switch 13 may comprise or be implemented by an NMOS, for example.

the 1 Figure 12 illustrates a particular example of a buck converter 10 implementation. However, modifications are possible. For example, the buck converter 10 can have and use an MCU (microcontroller) to record or detect and/or adjust the input voltage received via the inputs 11a, 11b. Furthermore, the rectifier circuit 12 can be implemented via a different topology. Any device that converts AC to DC and supplies a constant base current to drive the LEDs 50 can be used.

The controller 20 receives the direct current provided by the buck converter 10 and operates several channels C1 to CN individually. If the LED driver 1 is connected to LEDs 50, each channel C1 to CN can correspond to an LED 50 (or a group or chain of LEDs 50). The channels C1 to CN are operated or controlled individually via the PWM control.

For this purpose, the PWM component 30 according to the present embodiment comprises an ASIC (Application Specific Integrated Circuit) 31 arranged to receive a user signal indicating, for example, the channel C1 to CN to be served, i.e. which LED 50 on/off. should be switched off. The user signal may also indicate the brightness, dimming factor, etc. of the LED 50 to be operated. The ASIC 31 can be a module configured to receive the user inputs wirelessly. Furthermore, the ASIC 31 is set up to output a PWM signal with a specific duty cycle to a bus line 32 . The bus line 32 has several branches corresponding to the channels C1 to CN.

The bus line 32 is connected to the switching component 40 comprising a plurality of switches 41 which correspond to the channels C1 to CN. The switches 41 can be implemented by one or more transistors and/or relays, such as MOSFETs. The operation or actuation of the switching component 40 can be implemented in various ways, e.g. via an optocoupler or push-pull circuit. The switches 41 are actuated according to the PWM signal, thereby determining the target currents to be supplied to the LEDs 50 individually. In other words, the PWM signal provides a control scheme based on user input so that target currents are individually selected and applied to channels C1 through CN.

The switching component 40 may further include capacitors 42 connected in parallel with the LEDs 50 . A capacitor 42 is provided for each channel C1 to CN. Furthermore, the diodes 43 can be connected in series with the capacitors 42 . The combination of a capacitor 42 and a corresponding adjacent diode 43 is connected in parallel with a corresponding switch 41 .

The single stage buck topology described above implements an LED driver 1 that can achieve high power factor. The technical solution is able to deal flexibly with different DC voltages, such as DC voltages after the buck converter 10 from 125 V to 370 V when connected to a power supply of 100 V to 277 V. Variable output voltages and currents can be implemented. The LED driver 1 can be set for different configurations of the LEDs 50 . The LEDs 50 are connected in series, with each LED 50 being individually controllable, i.e. the voltages and/or currents for operating the LEDs 50 can be selected and supplied individually. This is accomplished by adjusting the duty cycle of the PWM signal generated by ASIC 31 based on user input.

the 2 FIG. 1 shows a schematic circuit diagram of a single-stage LED driver 1 according to a second embodiment. The second embodiment illustrates a different structure of the buck converter 10.

In summary it can be said that the LED driver 1, as described above and in the 1 and 2 shown, allow a wide range of possible input and output voltages. The LED drivers 1 combine flexible design, precise current control, scalability to expand the number of channels, and adaptability to different applications, even those that require high-quality light output. Furthermore, the LED drivers 1 are single-stage drivers, which reduces bill of materials (BOM) components. Thus, the LED drivers 1 are compact, efficient and inexpensive.

The invention is not limited by the description based on the embodiments. Rather, the invention includes every new feature and also every combination of features, in particular every combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.

Reference List

1

LED driver

10

buck converter

11a

Entry

11b

Entry

12

rectifier circuit

13

Switch

14

Buck PFC Control IC

20

control unit

30

PWM component

31

ASIC

32

bus line

40

switching component

41

Switch

42

capacitor

43

diode

50

LED or group of LEDs

Claims (11)

LED driver (1) for an LED lamp or luminaire with two or more LEDs (50), the LED driver (1) having: a voltage input (11a, 11b) arranged to connect the LED driver (1) to an AC power source; a rectifier circuit (12) for converting the alternating current received from the voltage input (11a, 11b) into a direct current to be supplied to the LEDs (50); a switching component (40) connected between the rectifier circuit (12) and the LEDs (50) and comprising two or more switches (41), each switch associated with an individual LED (50) or a group of the LEDs (50) and set up to switch them; a PWM component (30) which is connected to the switching component (40) and set up to generate a PWM signal for actuating the switches (41) of the switching component (40), wherein the switching component (40) and the PWM component (30) are each designed as a multi-channel component. LED driver (1) after claim 1 , in which the PWM component (30) comprises an ASIC (31) and a bus line (32) which connects the ASIC (31) to the switches (41), the ASIC (31) being set up to convert the PWM - Output signal to the bus line (32). LED driver (1) after claim 2 wherein the ASIC (31) is further configured to receive user input, preferably wireless, for determining the PWM signal, preferably the duty cycle. LED driver (1) according to one of the preceding claims, further comprising a buck converter (10), which preferably contains the rectifier circuit (12). LED driver (1) after claim 4 wherein the buck converter (10) comprises a buck PFC control IC (14) and a switch (13) arranged to adjust the power factor of the buck converter (10). LED driver (1) after claim 4 or 5 , in which only a single buck converter (10) is connected between the voltage input (11a, 11b) and the switching component (40). LED driver (1) according to one of the preceding claims, in which the switches (41) of the switching component (40) are implemented by one or more transistors and/or relays. The LED driver (1) of any preceding claim, wherein the switching component (40) comprises two or more capacitors (42), each connected in parallel with a respective LED (50). LED driver (1) after claim 8 wherein the switching component (40) further comprises two or more diodes (43) connected in series with the capacitors (42). LED driver (1) after claim 9 , in which a group of a capacitor (42) and a diode (43) is connected in parallel with an associated switch (41). LED lamp or luminaire comprising an LED driver (1) according to any one of the preceding claims and two or more LEDs (50) connected to the LED driver (1).

Images