EP4642164A1

EP4642164A1 - Led driver for supplying an led load with a dc voltage

Info

Publication number: EP4642164A1
Application number: EP24172042.4A
Authority: EP
Inventors: Miguel Philipp Schneider; Fabio Romano
Original assignee: Tridonic GmbH and Co KG
Current assignee: Tridonic GmbH and Co KG
Priority date: 2024-04-24
Filing date: 2024-04-24
Publication date: 2025-10-29

Abstract

Disclosed is an LED driver (1) for supplying an LED load (3) with a DC voltage. The LED driver (1) comprises a voltage sensing circuit (11) for sensing a voltage feedback signal representing the DC voltage; a current sensing circuit (12) for sensing a current sensing signal representing an output current of the LED driver (1); a first control circuit (13) for shifting the voltage feedback signal by an offset in accordance with the current sensing signal of the LED driver (1); and a second control circuit (14) for regulating the DC voltage in accordance with a constant setpoint for the DC voltage and the shifted voltage feedback signal.. This facilitates a deployment of more cost-efficient control circuits for regulation purposes.

Description

Technical Field

The present disclosure relates generally to the field of lighting technology, and in particular to an LED driver for supplying an LED load with a DC voltage, to a method of operating the LED driver, to a driver system comprising the LED driver, and to a lighting system comprising the driver system.

Background Art

There are various approaches of driving high-power LED loads by means of parallel-connected constant voltage LED drivers, such as "voltage droop control". Voltage droop may refer to an intentional loss in output voltage from a device as it drives a load. In other words, the output voltage of the respective driver depends on its output current (see FIG. 1). If all LED drivers have such an output characteristic, their output ports can easily be connected in parallel.
In typical ASIC-based control circuits used for closed-loop voltage regulation, voltage droop is implemented in by adjusting a setpoint of the regulation in accordance with the output current. The dependency of the setpoint of the output voltage on the output current may be provided as a lookup table or mathematical function, for example.
Cost-efficient control circuits do not allow for an adjustment of the setpoint and therefore do not facilitate "voltage droop control" of parallel-connected constant voltage LED drivers per se.

Summary

It is an object to overcome the above-mentioned and other drawbacks.
The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.
According to a first aspect, an LED driver is provided for supplying an LED load with a DC voltage. The LED driver comprises a voltage sensing circuit for sensing a voltage feedback signal representing the DC voltage; a current sensing circuit for sensing a current sensing signal representing an output current of the LED driver; a first control circuit for shifting the voltage feedback signal by an offset in accordance with the current sensing signal of the LED driver; and a second control circuit for regulating the DC voltage in accordance with a constant setpoint for the DC voltage and the shifted voltage feedback signal.
The offset may decrease the voltage feedback signal in accordance with an increase of the current sensing signal of the LED driver.
The first control circuit may comprise a microcontroller, µC.
The second control circuit may comprise an application-specific integrated circuit, ASIC.
The LED driver may comprise a transformer including primary and secondary windings for inductive coupling of a primary side circuit and a secondary side circuit.
The current sensing circuit may comprise a shunt resistor forming part of the primary side circuit.
The current sensing circuit may comprise a shunt resistor forming part of the secondary side circuit.
The transformer may further comprise an auxiliary winding. The voltage sensing circuit may comprise the auxiliary winding, a rectifier, a smoothing capacitor and a resistive voltage divider.
The voltage sensing circuit may further comprise a digital-analog converter, DAC, of the first control circuit; and an offset resistor being connected between the DAC and the resistive voltage divider. The first control circuit may be configured to apply the current sensing signal via the DAC to the offset resistor so as to shift the voltage feedback signal by the offset.
According to a second aspect, a driver system is provided for supplying an LED load with a DC voltage. The driver system comprises a plurality of LED drivers according to the first aspect. The plurality of LED drivers have parallel-connected output ports.
According to a third aspect, a lighting system is provided, comprising a driver system according to the second aspect, and an LED load connected to the parallel-connected output ports of the plurality of LED drivers of the driver system.
According to a fourth aspect, a method is provided of operating an LED driver for supplying an LED load with a DC voltage. The method comprises sensing a voltage feedback signal representing the DC voltage; sensing a current sensing signal representing an output current of the LED driver; shifting the voltage feedback signal by an offset in accordance with the current sensing signal of the LED driver; and regulating the DC voltage in accordance with a constant setpoint for the DC voltage and the shifted voltage feedback signal.
The method may be performed by an LED driver according to the first aspect.

Advantageous Effects

Adjusting the feedback signal instead of the setpoint is simple to implement and facilitates a deployment of more cost-efficient control circuits (ASICS) for regulation purposes.

Brief Description of Drawings

The above-described aspects and implementations will now be explained with reference to the accompanying drawings, in which the same or similar reference numerals designate the same or similar elements.
The drawings are to be regarded as being schematic representations, and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose become apparent to those skilled in the art.

FIG. 1 illustrates voltage droop control with reference to constant voltage control;
FIG. 2 illustrates an exemplary LED driver in accordance with the present disclosure;
FIG. 3 illustrates an exemplary driver system in accordance with the present disclosure; and
FIG. 4 illustrates a method of operating an LED driver in accordance with the present disclosure.

Detailed Descriptions of Drawings

In the following description, reference is made to the accompanying drawings, which form part of the disclosure, and which show, by way of illustration, specific aspects of implementations of the present disclosure or specific aspects in which implementations of the present disclosure may be used. It is understood that implementations of the present disclosure may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.
For instance, it is understood that a disclosure in connection with a described method may also hold true for a corresponding apparatus or system configured to perform the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units), even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary implementations and/or aspects described herein may be combined with each other, unless specifically noted otherwise.
FIG. 1 illustrates voltage droop control with reference to constant voltage control.
All electrical systems have some amount of resistance between a supply output and a load. At high currents, even a small resistance results in a substantial voltage drop between the supply and the load.
Under constant voltage control, sudden load changes will cause transient voltage spikes instead.
Under voltage droop control, sudden load changes simply result in the aforementioned voltage drop.
FIG. 2 illustrates an exemplary LED driver 1 in accordance with the present disclosure.
The LED driver 1 is suitable for supplying an LED load 3 (see FIG. 3) with a - regulated - DC voltage. Those skilled in the art will appreciate that this applies to various driver topologies, such as the depicted resonant converter topology.
In the example of FIG. 2, the LED driver 1 may comprise a transformer 15 including primary 151, L_prim and secondary 152, L_sec windings for inductive coupling of a primary side circuit and a secondary side circuit. The transformer 15 may further comprise an auxiliary winding 153, L_aux.
The LED driver 1 further comprises a current sensing circuit 12 for sensing a current sensing signal representing an output current of the LED driver 1.
According to a non-limiting example, the current sensing circuit 12 may comprise a shunt resistor forming part of the primary side circuit (see FIG. 2) or of the secondary side circuit (not shown).
The LED driver 1 further comprises a voltage sensing circuit 11 for sensing a voltage feedback signal representing the DC voltage.
According to a non-limiting example, the voltage sensing circuit 11 may comprise the auxiliary winding 153, L_aux, a rectifier 111, a smoothing capacitor 112 and a resistive voltage divider 113, R₂; 114, R₁.
The voltage sensing circuit 11 may further comprise a digital-analog converter, DAC 131, of the first control circuit 13; and an offset resistor 115, R_offset being connected between the DAC 131 and the resistive voltage divider 113, R₂; 114, R₁.
The LED driver 1 further comprises a first control circuit 13 such as a microcontroller, µC, for shifting the voltage feedback signal by an offset in accordance with the current sensing signal of the LED driver 7.
The offset may particularly decrease the voltage feedback signal in accordance with an increase of the current sensing signal of the LED driver ("voltage droop", see FIG. 1).
The first control circuit 13 may particularly be configured to apply the current sensing signal via the DAC 131 to the offset resistor 115, R_offset so as to shift the voltage feedback signal by the offset. Those skilled in the art will appreciate that this is one of a number of possibilities for implementing a voltage droop / decrease for an increasing current sensing signal.
In other words, the analog feedback signal V_sense (see FIG. 2) being provided at a center tap of the resistive voltage divider 113, R₂; 114, R₁ may be manipulated by means of the DAC 131 such that it assumes the "droop" characteristic. The DAC 131 generates the voltage offset across the offset resistor 115, R_offset. The higher the output current, the higher the offset applied to the feedback signal. In accordance with FIG. 1, zero offset will be applied for zero output current I_out, indicating a DC voltage of V_max, and a proportional offset will be applied for an increasing output current I_out.
The LED driver 1 further comprises a second control circuit 14 such as an application-specific integrated circuit, ASIC, in particular a cost-efficient ASIC having a constant setpoint, for regulating the DC voltage in accordance with the constant setpoint for the DC voltage and the shifted voltage feedback signal.
Note that for manipulation of the feedback signal the first control circuit 13 and the second control circuit 14 do not need to communicate.
In summary, the present disclosure proposes adaptation of the feedback signal of a regulation instead of its setpoint, such that "voltage droop control" can be realized also in connection with more cost-efficient control circuits having a constant setpoint.
FIG. 3 illustrates an exemplary driver system 2 in accordance with the present disclosure.
The driver system 2 is suitable for supplying an LED load 3 with a DC voltage and forms part of a lighting system 2, 3 further comprising the LED load 3.
The driver system 2 comprises a plurality of LED drivers 1 according to the first aspect having parallel-connected output ports, to which the LED load 3 is connected.
Without loss of generality, the driver system 1 of FIG. 3 comprises two LED drivers 1.
In particular, a total nominal power of the plurality of LED drivers 1 may correspond to a nominal power of the LED load 3.
According to the non-limiting example of FIG. 3, the total nominal power of the plurality of LED drivers 1 amounts to 2×100W=200W which corresponds to the nominal power of the LED load 3 of 200W.
The respective LED driver 1 is configured to regulate the DC voltage in accordance with a respective drooping output voltage curve as shown in FIG. 1, for example.
FIG. 4 illustrates a method 4 of operating an LED driver 1 in accordance with the present disclosure.
The method 4 is suitable for supplying an LED load 3 with a DC voltage.
The method 4 comprises sensing 41 a voltage feedback signal representing the DC voltage.
The method 4 further comprises sensing 42 a current sensing signal representing an output current of the LED driver 1.
The method 4 further comprises shifting 43 the voltage feedback signal by an offset in accordance with the current sensing signal of the LED driver 1.
The method 4 further comprises regulating 44 the DC voltage in accordance with a constant setpoint for the DC voltage and the shifted voltage feedback signal.
In particular, the method 4 may be performed by an LED driver 1 according to the first aspect.
The present disclosure has been described in conjunction with various implementations as examples. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed matter, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word "comprising" does not exclude other elements or steps and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Claims

An LED driver (1) for supplying an LED load (3) with a DC voltage, the LED driver (1) comprising
a voltage sensing circuit (11) for sensing a voltage feedback signal representing the DC voltage;

a current sensing circuit (12) for sensing a current sensing signal representing an output current of the LED driver (1);

a first control circuit (13) for shifting the voltage feedback signal by an offset in accordance with the current sensing signal of the LED driver (1); and

a second control circuit (14) for regulating the DC voltage in accordance with a constant setpoint for the DC voltage and the shifted voltage feedback signal.
The LED driver (1) of claim 1,
the offset decreasing the voltage feedback signal in accordance with an increase of the current sensing signal of the LED driver (1).
The LED driver (1) of claim 1 or claim 2,
the first control circuit (13) comprising a microcontroller, µC.
The LED driver (1) of any one of the claims 1-3,
the second control circuit (14) comprising an application-specific integrated circuit, ASIC.
The LED driver (1) of any one of the claims 1-4, comprising
a transformer (15) including primary (151, L_prim) and secondary (152, L_sec) windings for inductive coupling of a primary side circuit and a secondary side circuit.
The LED driver (1) of claim 5,
the current sensing circuit (12) comprising a shunt resistor forming part of the primary side circuit.
The LED driver (1) of claim 5,
the current sensing circuit (12) comprising a shunt resistor forming part of the secondary side circuit.
The LED driver (1) of any one of the claims 5-7,
the transformer (15) further comprising an auxiliary winding (153, L_aux);

the voltage sensing circuit (11) comprising the auxiliary winding (153, L_aux), a rectifier (111), a smoothing capacitor (112) and a resistive voltage divider (113, R₂; 114, R₁).
The LED driver (1) of claim 8,
the voltage sensing circuit (11) further comprising
a digital-analog converter, DAC (131), of the first control circuit (13); and

an offset resistor (115, R_offset) being connected between the DAC (131) and the resistive voltage divider (113, R₂; 114, Ri);

the first control circuit (13) being configured to apply the current sensing signal via the DAC (131) to the offset resistor (115, R_offset) so as to shift the voltage feedback signal by the offset.
A driver system (2) for supplying an LED load (3) with a DC voltage,
the driver system (2) comprising a plurality of LED drivers (1) according to any one of the claims 1-9;

the plurality of LED drivers (1) having parallel-connected output ports.
A lighting system (2, 3), comprising
a driver system (2) according to claim 10; and

an LED load (3) connected to the parallel-connected output ports of the plurality of LED drivers (1) of the driver system (2).
A method (4) of operating an LED driver (1) for supplying an LED load (3) with a DC voltage, the method (4) comprising
- sensing (41) a voltage feedback signal representing the DC voltage;

- sensing (42) a current sensing signal representing an output current of the LED driver (1);

- shifting (43) the voltage feedback signal by an offset in accordance with the current sensing signal of the LED driver (1); and

- regulating (44) the DC voltage in accordance with a constant setpoint for the DC voltage and the shifted voltage feedback signal.
The method (4) of claim 12,
being performed by an LED driver (1) according to any one of the claims 1-9.