Method for controlling a lighting and signaling module for a motor vehicle

Abstract

The invention relates to a method for operating a lighting module of a motor vehicle, the lighting module comprising at least one electroluminescent diode supplied with an electric current, characterized in that the intensity (I) of the electric current is varied sinusoidally at a constant voltage (U0) with an oscillation period (T0) of between 30 s and 60 s.

Description

Technical Field

[0001] The present invention claims priority from French application No. 1911633, filed on October 17, 2019, the contents of which (text, drawings and claims) are incorporated herein by reference. The present invention applies to the control of lighting and signal modules for motor vehicles.

[0002] More particularly, the present invention relates to a method for operating lighting and signal modules to reduce energy consumption. Background Art

[0003] Lighting and signal modules (headlights, daytime running lights, etc.) usually include an illumination light source (halogen lamp, xenon lamp, LED lamp) controlled by an electronic card (PCB) and associated with various optical components (lenses, reflectors, etc.), the whole of which is encapsulated in a housing.

[0004] Headlamps and vehicle lights with LEDs are usually powered and operated by electrical energy with constant power (stabilized current and constant voltage), the power (P) being determined by the product of the intensity (I) of the current and the voltage (U).

[0005] Furthermore, the energy consumption (E) of the electrical system is constant and is calculated using the formula (E) = power (P) x duration (T). However, today, the automotive industry is forced to drastically reduce vehicle energy consumption in order to reduce CO2 emissions, but does not agree to significantly restrict the performance and characteristics of lighting systems.

[0006] In particular, from patent applications FR2983143 and EP2261081 a method for reducing energy consumption is known which aims to reduce the intensity of the current while maintaining said current constant so that the resulting light variations continue to comply with regulatory thresholds without being perceived by the user of the vehicle.

[0007] Patent EP2741578B1 describes a control loop and a control method for controlling an LED, which are intended to transmit a signal for adjusting a reference current source so as to vary the voltage of an output current within a determined range.

[0008] In addition, in older generation vehicles, the alternator was not sufficiently stabilized, which led to variations in strength. However, these variations were neither intentional nor controlled and were not related to the unpopular optional goal of reducing electrical consumption.

[0009] Thus, in the present context, the object of the invention is to simultaneously achieve, in a cycle, optimal performance (lighting range, brightness perception, beam width, etc.) and a significant reduction in energy consumption taking into account the scope permitted by law, but without the user of the vehicle perceiving said changes being noticeable and without causing a degradation of safety conditions. Summary of the Invention

[0010] According to the invention, this object is achieved by means of a method for operating a lighting module of a motor vehicle, the lighting module comprising at least one light-emitting diode (LED) supplied with a direct current, characterized in that the intensity of the current is varied sinusoidally at a constant voltage with an oscillation period of between 30 and 60 seconds.

[0011] According to a preferred embodiment of the method of the present invention, the intensity of the current is varied according to a rule as a function of time: I = I0 - kI0sin 2 (2πt / T0), where k is the oscillation amplitude change of the current and T0 is the oscillation period.

[0012] According to an advantageous characteristic of the method, the intensity of the current is varied between 0.7A and 1.1A.

[0013] According to another feature, the oscillation amplitude varies by less than or equal to 20%.

[0014] According to a variant embodiment of the method, it is designed that at a constant voltage, the power of the current varies according to a rule as a function of time; P = I0U0 - kI0U0sin 2 (2πt / T0), where k is the oscillation amplitude change of the current and T0 is the oscillation period.

[0015] According to another characteristic of the invention, the reduction in electrical energy consumption E is given by the formula ΔE / E=k / 2, where k is the variation in the oscillation amplitude of said current.

[0016] Another object of the present invention is to provide a device for implementing the control method defined above based on a direct current delivered by an on-board battery, characterized in that the device comprises an electronic circuit that converts the direct current (DC) into an alternating current (AC) for powering the vehicle's lighting and signal modules.

[0017] A further object of the present invention is also to provide an energy-saving motor vehicle which is equipped with a lighting and signaling module which is actuated by means of the actuation method according to the invention.

[0018] The sinusoidal function of the intensity of the current (or the power of the current) is a simple function obtained by conventional AC / DC signal conversion methods, which is differentiable and continuous and does not cause noticeable changes in the visual appearance of the light beam to an observer.

[0019] The invention has significant technical and economical benefits, since energy savings of approximately 10% can be obtained due to the described manipulation method.

[0020] Moreover, due to the use of a sinusoidal function, the intensity of the current varies within a range of values that is smaller than the intensity of the stabilised current (typically 0.8 A), which makes it possible to reduce the number of LEDs and therefore the cost of the lighting module. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Other features and advantages of the present invention will become more apparent upon reading the following detailed description of the present invention and the accompanying drawings, in which:

[0022] - Figure 1 is a graph showing the stable electrical supply profile (current I0 and voltage U0) as a function of time t (in seconds).

[0023] - Figure 2 is a graph showing a sinusoidal power supply profile according to the method of the invention, said sinusoidal power supply profile being Figure 1 The same period T0 of time t has a varying intensity (I) and a maximum current reduction amplitude k (%).

[0024] - Figure 3 FIG. 4 is an overall schematic diagram of a device capable of implementing the method for operating a lighting module according to the present invention.

[0025] - Figure 4 An embodiment of an electronic circuit is shown which is capable of generating a sinusoidal control signal based on a DC current signal.

[0026] For greater clarity, the same or similar elements are identified by the same reference numerals throughout the drawings. DETAILED DESCRIPTION

[0027] Naturally, the embodiments of the method of the invention shown in the above-mentioned figures and described below are given only as non-limiting examples. According to the invention, it is expressly provided that different embodiments can be provided and combinations between these different embodiments can be made.

[0028] The method according to the invention serves to control lighting and / or signal modules of a motor vehicle in order to save energy.

[0029] Figure 3Such a module 3 (for example, a headlamp) shown schematically above generally comprises at least one light source, for example an electroluminescent diode (LED) powered by a stabilized direct current delivered by the vehicle battery 1. This current (whose voltage U is generally 12 V) has a Figure 1 The outline shown.

[0030] Therefore, the supply voltage U of the current is constant (referenced as U0) and the power P is determined by the product of the intensity of the current and the voltage of the current (P=U0xI). The energy consumption E of the lighting module is also constant and is calculated by the product of the power of the lighting module and the time (E=Pxt).

[0031] The control method of the present invention aims to modify the current profile of the lighting module by varying the intensity of the current sinusoidally with a long oscillation period (T0) between 30 and 60 seconds. Under these conditions, the power oscillations are neither noticeable nor disruptive to the driver of the vehicle or other vehicles.

[0032] The specific outline of the method according to the invention for the electrical power supply of the modules is given by Figure 2 This profile corresponds to the oscillations of the intensity I (in amperes) of the current, with a peak current drop of k = 0.2 (-20%). These oscillations are caused by the sinusoidal function (A) of the current: I(t) = I0 - kI0sin 2 (2πt / T0), where k is the oscillation amplitude change of the current and T0 is the oscillation period.

[0033] This change in the intensity of the current necessarily results in a change in power P (in Watts), which is governed by equation (B): P(t)=I0U0-kI0U0sin 2 (2πt / T0), where k is the oscillation amplitude change of the current and T0 is the oscillation period.

[0034] This power variation is within the permitted variation range from a regulatory point of view and can be obtained with the aid of, for example, a conventional oscillator.

[0035] and Figure 2 The power supply profile corresponding to the sinusoidal function of brings energy savings ΔE, which is given by equation (C) ( Figure 2 ) is given and expressed as a ratio (D): ΔE / E=k / 2.

[0036] Thus, a change in the current intensity with an amplitude of k=20% can save 10% of the energy in the selected period, this value being independent of the oscillation period, as shown in formula (C).

[0037] The sinusoidal profile of the current variation can be approximately synthesized by means of a mathematical function integrating polynomials, spline functions, etc., while bringing about a technical effect similar to that produced by the sine function (A).

[0038] The system capable of implementing the control method of the present invention is composed of Figure 3 The main power supply is formed by the vehicle's battery 1 , which delivers a regulated direct current (DC) with a voltage U0 of 12V.

[0039] The intensity of this current is converted into an alternating current signal (AC) by a converter 2 (or "driver"), which includes Figure 4 The converted signal is then sent to a lighting and signal module 3, in particular to a headlamp and a headlight 4 having an electroluminescent diode (LED), such as a Figure 3 and Figure 4 shown.

Claims

1. A method for operating a lighting module of a motor vehicle, the lighting module comprising at least one electroluminescent diode powered by an electric current, characterized in that The intensity I of the current is varied sinusoidally with an oscillation period T0 between 30s and 60s at a constant voltage U0, so that the intensity I of the current varies according to a rule that is a function of time; I=I0-kI0sin 2 (2πt / T0), where k is the oscillation amplitude variation of the current and T0 is the oscillation period, the current is delivered by the vehicle battery and the supply voltage of the current is constant, and the oscillation amplitude variation k is less than or equal to 20%.

2. The control method according to claim 1, characterized in that: The intensity I of the current was varied between 0.7A and 1.1A.

3. The control method according to claim 1 or 2, characterized in that: Under constant voltage U0, the power P of the current is varied according to a rule that is a function of time; P = I0U0 - kI0U0sin 2 (2πt / T0), where k is the oscillation amplitude change of the current and T0 is the oscillation period.

4. The control method according to claim 1 or 2, characterized in that: The reduction ΔE of the electrical energy consumption E is given by the formula ΔE / E=k / 2, where k is the change in the oscillation amplitude of the current.

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