Energy supply device for luminaire having matrix of LEDs, in particular LED motor vehicle headlamp

Abstract

The invention relates to a circuit arrangement (S) for a luminaire, comprising an input for connection to a power supply network (1), an adjustable voltage source (4), in which the input of the voltage source (4) is connected to the input of the circuit arrangement (S), a matrix of light-emitting diodes (LED1, LED2,..., LEDn), which is connected to the output of the voltage source (4), and-a control unit to which a control interface of the voltage source (4) is connected,-the circuit arrangement (S) has a series circuit formed by at least one light-emitting diode (LED1, LED2,..., LEDn) and an adjustable current source (I1, I2,..., In), -the series circuits are connected in parallel and thus form a matrix and-the voltage source (4) regulates its output voltage (Vddp) to a target voltage value provided at a control interface by a control unit having an input for reading-state information about the temperature in the matrix,-measured values (T) of the temperature of the light-emitting diodes (LED1, LED2,..., LEDn),-measured values (T) of the temperature of the light-emitting diodes (LED1, LED2,..., LEDn),-measured values (T) of the temperature of the light-emitting diodes (LED1, LED2,..., LEDn), and-measured values (T) of the temperature of the light-emitting diodes (LED1, LED2,..., LEDn). A measurement value (Vcs1, Vcs2,..., Vcsn) of the voltage across the current source (I1, I2,..., In); -a measured value of the voltage (Vddp) on the matrix and / or a measured value of the voltage (Vf1, Vf2,..., Vfn) on the light emitting diodes (LED1, LED2,..., LEDn) and / or a measured value of the current flowing through each series circuit, and the control unit determines a target voltage value or current value for controlling the interface from the state information and / or the measured values of the temperature, voltage and / or current (T, Vcs1, Vcs2,..., Vcsn, Vf1, Vf2,..., Vfn).

Description

Technical Field

[0001] The present invention relates to a circuit arrangement for a lamp, in particular an LED motor vehicle headlamp.

[0002] - comprises an input for connection to a power supply network, for example an onboard power supply of a motor vehicle,

[0003] - comprises a regulatable voltage source having an input, an output and a control interface, wherein the input is connected to the input of the circuit arrangement,

[0004] - comprises a matrix of light emitting diodes connected to the output of a voltage source, and

[0005] - comprises a control unit to which a control interface of the adjustable voltage source is connected,

[0006] - the circuit arrangement comprises a series circuit formed by at least one light-emitting diode and a controllable current source, by means of which the current flowing through the series circuit can be controlled,

[0007] - the series circuits are connected in parallel and the series circuits connected in parallel form a matrix and

[0008] The voltage source is designed to regulate its output voltage to a voltage value provided by the control unit at the control interface. Background Art

[0009] LED matrix circuit arrangements are often used in motor vehicle headlamps in order to generate different light modes and light settings. These LED matrix circuit arrangements are connected to one or more external supply voltage sources and have at least one adjustable voltage source, a control unit and a plurality of current sources connected in series with the LEDs. These series circuits form an LED matrix. The supply voltage level provided by the voltage source is controlled by the control unit. The control unit determines a duty cycle for each series circuit in order to dim the current flowing through the series circuit by pulse width modulation with the help of the current source. The duty cycle can be sent to the current source, which then adjusts the current corresponding to the dimming.

[0010] In the known LED matrix circuit arrangement, the supply voltage is adjusted so that sufficient voltage is provided for all series circuits to achieve the current with the desired current level required to generate the desired light. In order to reliably achieve this goal, that is, the desired current level, the supply voltage is usually provided by a voltage source, ensuring that the supply voltage is so large that the desired current level is achieved. So far, in such LED matrix circuit arrangements with current sources connected in series with LEDs, no attention has been paid to only providing the current source with the minimum voltage required to achieve the desired current level. This leads to high power loss in the voltage source, LED, current source and the associated components. The self-heating of the electronic components is high and the LED is thus in a hot environment. Higher LED temperatures lead to lower light efficiency, which must be compensated by dimming the LED less to generate more light when necessary.

[0011] At present, the power loss in the current source is not optimized. In order to prevent excessive heating of the components of the circuit arrangement, complex cooling concepts are developed and implemented. If necessary, particularly high-quality components must also be used, which would not be necessary for other reasons. Summary of the invention

[0012] The present invention is based on this.

[0013] The technical problem underlying the invention is to minimize the heating during lighting.

[0014] According to the invention, this problem is solved in that the control unit has an input,

[0015] - for reading out status information about the temperatures in or on the matrix, which can be assigned to the individual LEDs,

[0016] - measured values ​​for reading the temperature of the individual LEDs,

[0017] - a measurement for reading the voltage across the current source of each series circuit,

[0018] - for reading the measured values ​​of the voltage across the matrix and / or the measured values ​​of the voltage across the light-emitting diodes of each series circuit and / or

[0019] - for reading the measured value of the current flowing through each series circuit and

[0020] The control unit is suitable for

[0021] - determining a target voltage value from one or more of the read-in state information, the temperature, the read-in measured values ​​of the voltage and / or the current, which target voltage value can be provided at the control interface in order for the adjustable voltage source to be adjusted to this voltage value,

[0022] - determining a target amplitude for the current flowing through the series circuit from one or more of the read-in state information, the temperature, the voltage and / or the read-in measured value of the current, so that the current source regulates a current with this amplitude.

[0023] By evaluating status information, such as the LED temperature (high / medium / low) or the voltage on the current source or on the LED (forward voltage, high / medium / low) or by evaluating measured values, in particular the temperature or the voltage on the current source, the forward voltage or the measured value of the voltage on the series circuit, the regulation of the current source in each series circuit can be optimized. Compared with the prior art, the voltage on the current source and the current regulated by the current source can be further reduced. Unnecessary heat generation for light emission can be avoided.

[0024] New LED matrix components on the market provide status information of the LED current source voltage or even status information of the measured value. This makes it possible to optimize the status information and / or measured values ​​for optimizing the voltage provided by the voltage source, applied to the LED matrix and the current flowing through the series circuit. The voltage on the current source can also be reduced by the optimal voltage at the output of the voltage source, which is reduced relative to the conventional circuit arrangement structure, and the reduced current in the series circuit. By reducing the current source voltage to an absolute minimum, lower power loss in the voltage source and current source can be achieved. Therefore, lower self-heating of these electronic components is achieved and the LED is operated in a lower temperature environment, which leads to higher light efficiency.

[0025] The circuit arrangement can also have an input or a video data interface for reading a target brightness distribution or video data from a communication network.

[0026] For measuring temperature, voltage or current, the circuit arrangement according to the invention can have a temperature sensor, a voltage sensor and / or a current sensor for determining the measured values. No external sensors are then required to provide these measured values.

[0027] In the control unit of the circuit arrangement according to the invention, current-voltage characteristic curves of the current source and / or current-voltage characteristic curves of the LED can be stored for different temperatures. According to the invention, it is possible to determine a target voltage value based on measured values ​​and the characteristic curve or one of the characteristic curves. In the case where the temperature is known and the measured values ​​of the voltage on the current source and / or the forward voltage or the voltage on the series circuit or the current flowing through the series circuit are known, the optimal operating point of the current source can therefore be determined. By observing the optimal operating points of all current sources, the optimal voltage of the voltage source and the optimal current of the current source can then be determined, the voltage source supplying the voltage to the series circuit.

[0028] According to the invention, the characteristic curve of the LED and / or of the current source can be determined individually beforehand and stored in the control unit, in particular as a look-up table.

[0029] According to the invention, in order to determine the optimal target voltage value of the voltage source, it is possible, for example, to use the control unit

[0030] For each series circuit, a current which is required for operating the light-emitting diode, in particular for generating the desired light by means of the LED, and which flows through the series circuit can be determined.

[0031] For each series circuit, the voltage at the current source required for generating the required current through the series circuit can be determined using a characteristic curve of the current source of the series circuit stored in the control unit.

[0032] For each series circuit, the forward voltage can be determined from the temperature of the light-emitting diode or in the region of the light-emitting diode and the current required to flow through the series circuit using a characteristic curve of the light-emitting diode stored in the control unit.

[0033] For each series circuit the required voltage and the sum of the forward voltage can be determined and

[0034] The sums determined in this way are compared by means of a control unit and the largest sum can be used as a target voltage value.

[0035] In the circuit arrangement according to the invention, the control unit can be arranged such that

[0036] When all voltages on the current sources are above a first predetermined value, the target voltage value is reduced by a predetermined amount, and

[0037] When a voltage on the current source is lower than a first predetermined value, the target voltage value is increased by a predetermined amount,

[0038] And repeat these steps until all the voltages on the current sources are not lower than the first predetermined value and the lowest of the voltages on the current sources is higher than the first predetermined value by less than a predetermined amount.

[0039] According to the invention, the circuit arrangement can have an integrated circuit, for example an application specific integrated circuit (ASIC), which is connected between the control unit and the sensor. According to the invention, the integrated circuit can take over the above-mentioned functions of the control unit.

[0040] According to the invention, the control unit or the integrated circuit may be adapted to determine a duty cycle for the current source of each series circuit in order to dim the LED by pulse width modulating the current flowing through the series circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] An embodiment of a circuit arrangement structure according to the present invention for a lamp is described in detail with reference to the accompanying drawings. The accompanying drawings are as follows:

[0042] Figure 1 A highly simplified circuit diagram of a circuit arrangement according to the invention is shown. DETAILED DESCRIPTION

[0043] The circuit arrangement S is provided for a motor vehicle headlamp. The circuit arrangement has an input for connection to a motor vehicle onboard power supply 1, in which connection different sources for electrical energy, such as a battery or a generator, can be provided. The circuit arrangement S has an adjustable (controlled) voltage source 4. The voltage source is controlled by a control unit 3. The control unit provides a target voltage value to the voltage source 4, to which the voltage source is adjusted. The voltage source then provides a voltage Vddp. The circuit arrangement also has a video data interface (not shown), via which the control unit 3 can read brightness values ​​or video data.

[0044] The control unit 3 is connected to a memory 2 in which characteristic curves and voltage values ​​are stored and from which the control unit 3 can read them.

[0045] The circuit arrangement also has a lighting unit 5, which consists of a plurality of components. The lighting unit thus has an LED matrix, which is formed by a plurality of series circuits connected in parallel. Each series circuit has at least one light-emitting diode LED1, LED2, ..., LEDn and an adjustable current source I1, I2, ..., In connected in series. A forward voltage Vf1, Vf2, ..., Vfn drops across the light-emitting diodes LED1, LED2, ..., LED and a voltage Vcs1, Vcs2, ..., Vcsn drops across the current sources I1, I2, ..., In. The sum of the forward voltage of one of the LEDs and the voltage across the current source of the same series circuit is equal to the voltage Vddp provided by the voltage source 4.

[0046] The current flowing through the series circuit and thus through the light-emitting diodes LED1, LED2, ..., LEDn can be adjusted by means of controlled current sources I1, I2, ..., In. More precisely, the peak value I can be adjusted on the one hand, but also the average current, which is obtained by pulse width modulation of the current. Both the peak value I and the duty cycle d are predetermined by the control unit for the current sources I1, I2, ..., In. These two values ​​are decisive for the light emitted by the light-emitting diodes LED1, LED2, ..., LEDn, in particular for the color and brightness of the light.

[0047] The peak value î and the duty cycle d of the current sources I1, I2, ..., In are determined by the control unit 3. The brightness or the duty cycle d is here part of a video signal generated by the control unit 3. The duty cycle d is encoded in the video signal. The video signal is sent by the control unit 3 to the ASIC 51 of the lighting unit, which decodes the duty cycle d from the video signal and converts it into control instructions for the current sources I1, I2, ..., In, which are sent to the current sources I1, I2, ..., In. The peak value î of the current flowing through the series circuit or the light-emitting diodes LED1, LED2, ..., LEDn is sent by the control unit 3 via the communication channel Com to the ASIC 51, which generates control instructions for the current sources I1, I2, ..., In from this, which are sent to the current sources I1, I2, ..., In.

[0048] The lighting unit 5 has a temperature sensor, by means of which the temperature in the region of each light emitting diode LED1, LED2, ..., LEDn can be measured. These measured values ​​T of the temperature represent the temperature of the light emitting diodes LED1, LED2, ..., LEDn. The measured temperatures T are provided by the temperature sensor to the ASIC, which then transmits these values ​​to the control unit via the communication channel Com.

[0049] The lighting unit also has a voltage sensor, which determines the voltage on the current source. These measured values ​​Vcs1, Vcs2, ..., Vcsn or, if necessary, Vf1, Vf2, ..., Vfn are also sent to the ASIC, which transmits the measured values ​​Vcs1, Vcs2, ..., Vcsn or, if necessary, Vf1, Vf2, ..., Vfn to the control unit 3 via the communication channel com.

[0050] With the aid of the measured value T of the temperature of the light-emitting diodes and the measured value of the voltage at the current source, the voltage Vddp at the output of the voltage source 4 can now be optimized and an optimized target value for the amplitude î of the current flowing through the series circuit can be provided at the Com interface, in particular by reducing the target value to at least the required value so that the voltage at the current sources I1, I2, ..., In is as low as required, so that as little power as required has to be converted via the current sources, the light-emitting diodes and the power supply (Spannungsversorgung).

[0051] In order to optimize the voltage Vddp, the control unit uses the characteristic curves of the light-emitting diodes and the characteristic curves of the current sources stored in the memory 2. This can be a separate characteristic curve determined for the components used or a characteristic curve provided by the manufacturer for the type of components used. These characteristic curves can be stored in the memory as equations. But it is simpler to store a table in the memory 2 and interpolate the missing values ​​in the table when necessary. In particular, for the light-emitting diodes LED1, LED2, ..., LEDn and the current sources, temperature-dependent characteristic curves and tables are also possible.

[0052] In order to determine the optimal target voltage value of the voltage Vddp, the control unit can first determine the current flowing through the series circuit required for operating the light-emitting diodes LED1, LED2, ..., LEDn, with which the light-emitting diodes LED1, LED2, ..., LEDn generate the desired light. In particular, the peak value î and the duty cycle d are determined. The current or the amplitude î flowing through the series circuit is calculated from the desired brightness and the measured value T of the temperature of the light-emitting diodes LED1, LED2, ..., LEDn provided by the ASIC 51, and the brightness is read by the control unit 3 via the vehicle 1 via the input video data.

[0053] Then, for each series circuit, the voltage Vcs1, Vcs2, ..., Vcsn required for the current source to generate the current required to flow through the series circuit is determined by means of the characteristic curve of the current source I1, I2, ..., In. Then, for each series circuit, the forward voltage Vf1, Vf2, ..., Vfn on the light emitting diodes LED1, LED2, ..., LEDn is determined from the temperature T of the light emitting diodes LED1, LED2, ..., LEDn and the required current flowing through the series circuit by means of the characteristic curve of the light emitting diodes LED1, LED2, ..., LEDn. Then, for each series circuit, the sum of the required voltage Vcs1, Vcs2, ..., Vcsn on the current source I1, I2, ..., In and the forward voltage Vf1, Vf2, ..., Vfn can be formed. If the sum of these two voltages is applied to the series circuit, the optimal operating point will be achieved. However, since the same voltage Vddp is supplied to all series circuits, the sum determined in this way is compared by means of the control unit and the largest sum is used as the target voltage value. This ensures that all series circuits are supplied with sufficient voltage and that all current sources are operated as close as possible to their optimum operating point. Reference numerals list

[0054] S circuit layout

[0055] 1. On-board power grid

[0056] 2Memory

[0057] 3Control Unit

[0058] 4 Voltage Source

[0059] 5 Lighting units

[0060] 51ASIC

[0061] LED1, LED2, ...LEDn light emitting diodes

[0062] I1, I2, ..., In current source

[0063] The voltage at the output of the Vddp voltage source

[0064] Vf1, Vf2, ..., Vfn are the forward voltages of the light-emitting diodes

[0065] Voltages on Vcs1, Vcs2, ..., Vcsn current sources

[0066] The temperature on the LED

[0067] The magnitude of the current flowing through a series circuit

[0068] dDuty cycle

Claims

1. A circuit arrangement (S) for a lamp, in particular an LED motor vehicle headlamp, - comprises an input for connection to a power supply network (1), for example an onboard power supply network of a motor vehicle, - comprises a regulatable voltage source (4) having an input, an output and a control interface, and wherein the input is connected to an input of the circuit arrangement (S), - comprises a matrix of light emitting diodes (LED1, LED2, ..., LEDn), which is connected to the output of a voltage source (4), and - comprises a control unit to which a control interface of the adjustable voltage source (4) is connected, - the circuit arrangement (S) comprises a series circuit formed by at least one light-emitting diode (LED1, LED2, . . . , LEDn) and an adjustable current source (I1, I2, . . . , In), by means of which the current flowing through the series circuit can be adjusted, - the series circuits are connected in parallel and the series circuits connected in parallel form a matrix, and - the voltage source (4) is configured to adjust its output voltage (Vddp) to a target voltage value provided by the control unit at the control interface, It is characterized in that The control unit has an input terminal, the input terminal - for reading status information about the temperatures (in or on the matrix), which temperatures (T) can be assigned to the individual light-emitting diodes (LED1, LED2, ..., LEDn), - a measured value (T) for reading the temperature of the individual light-emitting diodes (LED1, LED2, ..., LEDn), - measured values ​​(Vcs1, Vcs2, ..., Vcsn) for reading the voltages across the current sources (I1, I2, ..., In) of each series circuit, - for reading the measured value of the voltage across the matrix (Vddp) and / or the measured value of the voltage across each light emitting diode (LED1, LED2, ..., LEDn) of the series circuit (Vf1, Vf2, ..., Vfn), and / or - a measurement for reading the current flowing through each series circuit, and The control unit is suitable for - determining a target voltage value from the read-in status information and / or from the read-in measured values ​​of temperature, voltage and / or current (T, Vcs1, Vcs2, ..., Vcsn, Vf1, Vf2, ..., Vfn), which target voltage value can be provided at the control interface so that the adjustable voltage source (4) is adjusted to this voltage value, - determining a target amplitude of the current flowing through the series circuit from one or more of the read-in state information, from the read-in measured values ​​of the temperature, voltage and / or current, so that the current source regulates a current with this amplitude.

2. The circuit arrangement (S) according to claim 1, characterized in that The circuit arrangement (S) has a temperature sensor, a voltage sensor and / or a current sensor for determining the measured values ​​(T, Vcs1 , Vcs2 , . . . , Vcsn, Vf1 , Vf2 , . . . , Vfn).

3. The circuit arrangement (S) according to claim 1 or 2, characterized in that The control unit stores a current-voltage characteristic curve of the current source and / or a current-voltage characteristic curve of the light-emitting diode (LED1, LED2, ..., LEDn) for different temperatures, and can determine a target voltage value based on the measured value (T, Vcs1, Vcs2, ..., Vcsn, Vf1, Vf2, ..., Vfn) and the characteristic curve or one of the characteristic curves.

4. The circuit arrangement (S) according to claim 3, characterized in that The characteristic curves of the light-emitting diodes (LED1, LED2, . . . , LEDn) and / or of the current sources are determined individually in advance and stored in the control unit, in particular as a look-up table.

5. The circuit arrangement (S) according to any one of claims 1 to 4, characterized in that - in order to determine the target voltage value, the control unit can determine for each series circuit a current which is required for operating the light-emitting diodes (LED1, LED2, . . . , LEDn) and which flows through the series circuit, - for each series circuit, the voltage (I1, I2, ..., In) required at the current source (I1, I2, ..., In) for generating the required current through the series circuit can be determined using the characteristic curve of the current source of the series circuit, - for each series circuit, the forward voltage can be determined with the aid of the characteristic curve of the light-emitting diode (LED1, LED2, ..., LEDn) from a measured value of the temperature (T) of the light-emitting diode (LED1, LED2, ..., LEDn) or in the region of the light-emitting diode (LED1, LED2, ..., LEDn) and the required current flowing through the series circuit, - For each series circuit, determine the sum of the required voltage and the forward voltage, and - The determined sums are compared with the aid of the control unit and the largest sum can be used as the target voltage value.

6. The circuit arrangement (S) according to any one of claims 1 to 4, characterized in that The control unit is configured such that: when all measured values ​​(Vcs1, Vcs2, ..., Vcsn) of the voltage on the current source (I1, I2, ..., In) are higher than a first predetermined value, the target voltage value is reduced by a predetermined amount, and when one measured value (Vcs1, Vcs2, ..., Vcsn) of the voltage on the current source (I1, I2, ..., In) is lower than the first predetermined value, the target voltage value is increased by a predetermined amount, and these steps are repeated until all measured values ​​(Vcs1, Vcs2, ..., Vcsn) of the voltage on the current source are not lower than the first predetermined value.

7. The circuit arrangement (S) according to any one of claims 2 to 6, characterized in that The circuit arrangement has an integrated circuit, for example an application specific integrated circuit (ASIC), which is connected between the control unit and the sensor.

8. The circuit arrangement (S) according to any one of claims 1 to 7, characterized in that The control unit or integrated circuit is adapted to determine a duty cycle (d) for the current source of each series circuit in order to dim the light emitting diodes (LED1, LED2, . . . , LEDn) by pulse width modulation of the current flowing through the series circuit.

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