Lighting module and LED driver circuit with cloned constant current

Abstract

A lighting module with light-emitting diodes (LEDs) comprising: several LEDs (LED1 to LED9), each having a corresponding current path, wherein each of the several LEDs is capable of outputting a user-selectable white or non-white light; an electrical connection for connecting the module to an external electrical system; and optionally, software stored in a storage device for controlling electrical signals to the several LEDs, wherein a first group of LEDs (LED1, LED2, LED3) of the several LEDs is connected to corresponding transistors (Q1, Q2, Q3) and a current sink (U1) for driving a constant current through each LED of the first group of LEDs, and the first group of LEDs comprises one or more LEDs, and wherein at least a second group of LEDs (LED4 to LED9) of the several LEDs is connected such thatthat the constant current in the first group of LEDs is duplicated in the at least one second group of LEDs, and the second group of LEDs comprises one or more LEDs, wherein each of the second group of LEDs is connected to corresponding transistors of the second group (Q4 to Q9), and each of the transistors of the second group comprises a transistor emitter of the second group, wherein the transistor emitter of the second group is electrically connected to a voltage supply (V_Supply) via a sampling transistor resistor (R4 to R9).

Description

CROSS-REFERENCE TO RELATED REGISTRATION

[0001] The present application claims priority pursuant to 35 USC §119(e) of the preliminary US patent application No. 63 / 091,511, which was filed on October 14, 2020 and is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION

[0002] Light-emitting diodes (LEDs) used in automotive and other applications often require constant current operation to meet optical and / or electrical design specifications and other requirements. Particularly in automotive applications, constant current operation can control the light output of LEDs across a range of ambient and operating temperatures expected during vehicle operation. Furthermore, constant current operation can control the light output of LEDs under fluctuating supply voltages, which can deviate significantly from the nominal 12 volts depending on the battery design and condition.

[0003] Existing LED products for automotive and other applications may not use constant current at all, resulting in lower performance. Others use multiple integrated circuits to drive multiple LEDs, or dedicated integrated circuits capable of driving multiple LEDs, increasing the product cost.

[0004] Therefore, a cost-effective electronic circuit design is needed that can drive multiple LEDs with a constant current and that includes a controller (or other device, circuit or component arrangement) with an integrated circuit that provides a constant current for driving one LED (or some LEDs) and allows the current in one (or some) LEDs to be copied (cloned) for other LEDs. SUMMARY OF THE INVENTION

[0005] Disclosed here are examples of red, green, and blue (RGB) light-emitting diodes (LEDs) in a single module for use in automotive and other applications. Also disclosed is an example circuit where a specific current path driving the RGB LEDs is cloned for corresponding additional RGB LEDs. The LED circuits can, for example, include multiple LEDs, each with its own corresponding current path. A controller and associated software can be used to control the multiple LEDs.

[0006] Methods for controlling the RGB module are also disclosed here, by connecting it to an electronic system of an automobile or another system in which the module is integrated.

[0007] In one aspect, the module features multiple LEDs, each with its own current path, and each LED is capable of outputting user-selectable white or non-white light. An electrical connection is used to link the module to an external electrical system for power and, optionally, control. Software stored on a storage device can be used to control electrical signals to the multiple LEDs. The first group of LEDs in the multiple LED array can consist of red, blue, and green (RBG) LEDs, connected to appropriate transistors and a current sink to drive a constant current through each of the RGB LEDs. At least a second group of LEDs in the multiple LED array can also consist of RGB LEDs, connected such that the constant current in the first group of LEDs is duplicated (cloned) in the second group of RGB LEDs.

[0008] In another aspect, the LED circuit features multiple LEDs, each with its own current path and capable of outputting user-selectable white or off-white light. A controller is used to manage the multiple LEDs. The controller may contain software stored on a storage device. A current sink, as described above, can be used to drive a constant current through the multiple LEDs.

[0009] In another aspect, the circuit design for providing additional LED drivers uses only inexpensive, standardized components, such as inexpensive groups of transistors and resistors.

[0010] In another aspect, the circuit can be adapted to integrated circuits that supply current by inverting the topology and changing the polarity of the transistors to NPN.

[0011] In another aspect, the scaling granularity of the circuit from one group to several groups of LEDs is considered "perfect" because an additional resistor and transistor may be required for each additional LED, so that there are no disadvantages or advantages for a given number of cloned LEDs.

[0012] Furthermore, multiple cloned LED drivers can be combined to drive a higher current through a higher-power LED instead of multiple LEDs.

[0013] In another aspect, the modules and circuits shown and described can be used to control multiple LEDs with constant current in any products, including those found in transport systems (e.g. in the automotive, railway and aerospace industries), in industrial systems, in consumer goods (e.g. in entertainment devices and household appliances) and in medical devices that emit or require lighting. List of characters Fig. Figure 1 is a schematic drawing of an integrated RGB LED circuit showing a primary RGB LED constant current circuit and two cloned RGB LED circuits. Fig. Figure 2 is a schematic drawing of an integrated LED circuit showing a primary LED constant current circuit and a number N of cloned LED circuits. DETAILED DESCRIPTION OF THE INVENTION

[0014] With reference to Fig. Figure 1 shows an integrated LED driver (U1) comprising at least three current-drawing pins or connections (i.e., the current is regulated when it is fed back to ground or dropped), resistors R1 to R9, corresponding transistors Q1 to Q9, and corresponding LEDs labeled LED1 to LED9. While U1 is shown with at least three current-drawing pins to correlate with the three LED channels of an RGB LED, this description is equally applicable to cloning current from one or more LEDs or LED channels. Likewise, not all LED channels connected to U1 need to be cloned (as described below). However, for the purposes of the present disclosed example, all three available LED channels for RGB are cloned, one at a time.Furthermore, the current sink does not have to be an integrated circuit, but can also be one or more discretely constructed current sinks; however, in the following discussion, the current sink with an integrated circuit is used as an example.

[0015] The LED driver U1 is suitable for controlling an RGB array of LEDs. It precisely regulates the current through LED1, LED2, and LED3. The current regulation mechanism can consist of resistors located outside the integrated LED driver, or the current sinks can be controlled via software by a processor integrated within the integrated LED driver.

[0016] The LED driver U1 can have three sink pins or connectors for controlling the three different LED channels of a single RGB LED or separate red, green, and blue LEDs. However, it is understood that other controllers with more or fewer pins can also be used, as long as the LED driver U1 has at least the number of pins corresponding to the number of LEDs or LED channels directly controlled by U1. As described below, the final number of controlled LEDs is not limited by the number of pins or LED channels, since each of the LED channels directly controlled by U1 can be cloned to control additional LEDs.

[0017] The sink pin of the LED driver U1 can be used to supply a constant current through resistors R1, R2, and R3, for example, to U1 pin 1, U1 pin 2, and U1 pin 3 (not shown). Since even an inexpensive U1 controller is capable of drawing a constant current, a precise constant voltage is applied across resistors R1, R2, and R3. This voltage can optionally be varied using the PDM duty cycle capabilities of the LED driver U1 to compensate for variations in the circuit.

[0018] Due to the series circuit arrangement shown, the current sinks of the integrated LED driver can adjust the current flowing through resistors R1, R2 and R3, as well as through the PNP sampling transistors Q1, Q2 and Q3.

[0019] The collector and base terminals of the sampling transistors Q1, Q2 and Q3 are connected as shown, so that the net collector-emitter voltages correspond to the base-emitter junction voltages for these transistors with this specific current (i.e. the LED drive current I1, I2 and I3 set by the controller).

[0020] The resistance and base-emitter voltage drops across resistors R1, R2, and R3, and across transistors Q1, Q2, and Q3, are connected to additional driver transistors and resistors assigned to additional, e.g., cloned RGB LEDs. Resistors R4, R5, and R6, and transistors Q4, Q5, and Q6 can, for example, adjust the LED driver current at I4, I5, and I6, respectively. The base-emitter voltage drop of Q1, for instance, is "inverted" via the base-emitter of transistor Q4 to resistor R4. This applies to the other LED channels. Assuming the transistors and resistors of the cloned channels have similar values ​​to the original channel (i.e., those directly connected to U1 (Q1, Q2, Q3)), then the voltage drops across R4, R5, R6 are each similar to those of R1, R2, R3, and ultimately the currents I4, I5, I6 are cloned to I1, I2, I3.Similarly, resistors R7, R8, and R9, along with transistors Q7, Q8, and Q9, can set the LED driver current in I7, I8, and I9. This "imprinting" of the specific voltage caused by the set current, which flows through the resistor and transistor via additional transistors of the same type and resistors of the same value, results in the current set by the integrated circuit being copied (cloned) in these additional transistor circuits. That is, I4 is a clone of I1, I5 is a clone of I2, and I6 is a clone of I3. This arrangement also has the effect of canceling out temperature and other environmental influences on the base-emitter voltage of the respective transistors. Regardless of any change in the base-emitter voltage of, for example, Q1, the effect is reversed / compensated by Q4 in setting the voltage drop across R4.

[0021] It should be noted that in practice, the resistors assigned to the sampling transistors, i.e., those of the cloned channels, have a slightly higher value than the resistors assigned to the driver transistors (or direct transistors) (Q1, Q2, Q3). This is to compensate for the loss of base current in the driver transistors. For example, in a 27 mA design, the difference in resistance values ​​is only one step in the Electronic Industries Association (EIA) E96 resistor table (137 ohms for the sampling transistor versus 133 ohms for the driver transistor).

[0022] As described above, the circuit design is in Fig. 1 compatible with PDM.

[0023] Due to the series topology, the cloned currents are used to drive additional LEDs above and beyond the pin capacitance of the controller. By copying the base-emitter voltage for a given current and applying this voltage to a transistor of the same type, temperature-related changes in VBE (base-emitter voltage drop) are compensated. The voltage that develops across the emitter resistors in the driver transistor circuits serves to mask the VBE voltage fluctuations observed between individual transistors of the same type.

[0024] Fig. 2 is Fig. Figure 1 is similar, but instead of using an RGB LED or discrete red, green, and blue LEDs, only a single primary or directly driven LED using current I1 is shown, with one (LED2) and N (LEDN) secondary LEDs using current I2 to IN. While six secondary LEDs with cloned currents (I2, I3, I4, I5, I6, IN) are shown, Figure 1 shows Fig. 2, that the number of secondary LEDs can be extended up to a number of N LEDs, as symbolized by the ellipse.

[0025] In use, electrical signals, including the measured current, in the circuit described above can be managed, for example, by embedded software stored in a suitable memory device on the same circuit board as the circuit or on one or more separate but electrically coupled circuit boards. The circuit can be connected to external circuits, such as an automotive electrical system, using one or more suitable electrical connectors, including standard industrial pin and socket connectors. The embedded software can include one or more suitable algorithms capable of receiving signals from the external circuits, representing user input, such as from a driver, to change one or more states of the LEDs (e.g., increasing brightness, changing color mixing, etc.).The memory device can contain specific settings as input to the software, which define a state of the circuit and its LEDs when the device in which the circuit is installed is first switched on, switched off, or is in a specific operating state (e.g., a vehicle driving at night).

[0026] While certain elements, embodiments and applications of the present invention have been shown and described, it is understood that the invention is not limited thereto, since modifications can be made by the person skilled in the art without deviating from the scope of the present disclosure, particularly in view of the preceding teachings. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 091511

[0001]

Claims

[1] Lighting module with light-emitting diodes (LEDs) comprising the following: multiple LEDs, each having a corresponding current path, each of the multiple LEDs being suitable for outputting a user-selectable white or non-white light; an electrical connection for connecting the module to an external electrical system; and optionally, software stored in a storage device for controlling electrical signals to the multiple LEDs, wherein a first group of LEDs of the multiple LEDs is connected to appropriate transistors and a current sink to drive a constant current through each LED of the first group of LEDs, and the first group of LEDs comprises one or more LEDs, and wherein at least a second group of LEDs of the multiple LEDs is connected such that the constant current in the first group of LEDs is duplicated in the at least one second group of LEDs and the second group of LEDs comprises one or more LEDs. [2] Light-emitting diode (LED) circuit comprising the following: several LEDs, each with a corresponding current path, each of the several LEDs being suitable for outputting white and / or non-white light; and a controller to control the multiple LEDs, wherein a first group of LEDs of the multiple LEDs is connected to a corresponding first group of transistors and a first current sink for driving a constant current through each LED of the first group of LEDs, and the first group of LEDs comprises one or more LEDs, and wherein at least a second group of LEDs of the multiple LEDs is connected such that the constant current in the first group of LEDs is duplicated in the at least one second group of LEDs and the second group of LEDs comprises one or more LEDs. [3] LED circuit according to claim 2, wherein the controller contains software stored in a storage media device. [4] LED circuit according to claim 2 or claim 3, wherein the second group of LEDs is connected to a second current sink which is different from the first current sink. [5] LED circuit according to one of claims 2 to 4, wherein each of the transistors of the first group has a transistor base of the first group and a transistor collector of the first group and each of the respective transistor bases of the first group and each of the transistor collectors of the first group are electrically connected to each other. [6] LED circuit according to one of claims 2 to 5, wherein each LED of the second group of LEDs is connected to corresponding transistors of the second group, wherein each transistor of the second group has a transistor base of the second group and a transistor collector of the second group, wherein at least one transistor base of the first group is electrically connected to at least one transistor base of the second group. [7] LED circuit according to one of claims 2 to 6, wherein the first current sink is an LED driver with integrated circuit. [8] LED circuit according to one of claims 2 to 7, wherein the current in the second group of LEDs is an LED current of the second group and the constant current through each LED of the first group of LEDs together with the LED current of the second group is greater than the current sink of the first current sink. [9] LED circuit according to one of claims 2 to 8, wherein the LED driver with integrated circuit has several current-drawing pins. [10] LED circuit according to any one of claims 2 to 9, wherein the LED driver with integrated circuit has three current-drawing pins and the first group of LEDs comprises a red LED, a green LED and a blue LED and the second group of LEDs comprises at least one red LED of the second group, at least one green LED of the second group and at least one blue LED of the second group. [11] LED circuit according to any one of claims 2 to 10, wherein the first group of LEDs and the second LED together exceed the number of current-drawing pins. [12] LED circuit according to one of claims 2 to 11, wherein each of the transistor bases of the first group is electrically connected to each of the transistor bases of the second group. [13] LED circuit according to one of claims 2 to 12, wherein each of the transistors of the second group has a transistor emitter of the second group and the transistor emitter of the second group is electrically connected to a voltage supply via a sampling transistor resistor. [14] LED circuit according to one of claims 2 to 13, wherein each of the transistors of the first group has a transistor emitter of the first group and the transistor emitter of the first group is electrically connected to the power supply via a corresponding driver transistor resistor. [15] LED circuit according to one of claims 2 to 14, wherein the driver transistor resistor has a driver transistor resistance value, the sampling transistor resistor has a sampling transistor resistance value and the driver transistor resistance value is approximately equal to the sampling transistor resistance value. [16] LED circuit according to one of claims 2 to 15, wherein the driver transistor resistor has a driver transistor resistor voltage drop and the sampling transistor resistor has a sampling transistor resistor voltage drop and the driver transistor resistor voltage drop and the sampling transistor resistor voltage drop are approximately equal. [17] LED circuit according to any one of claims 2 to 16, wherein the driver transistor resistor has a driver transistor resistance value, the sampling transistor resistor has a sampling transistor resistance value and the sampling transistor resistance value is higher than the driver transistor resistance value. [18] LED circuit according to any one of claims 2 to 17, wherein the sampling transistor resistance value is about one step higher in the EIA-E96 resistance table than the driver transistor resistance value.

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