Clone constant current LED driver circuit and usage method

Abstract

To provide a light emitting diode (LED) circuit having a plurality of LEDs each of which includes its own current path.SOLUTION: A controller may be included to control an LED. A first set of LEDs from among a plurality of LEDs is connected to a first set transistor and a first current sink to drive a constant current through each of LEDs which are the first set, and the first set of LEDs includes one or more LEDs, and the LED circuit may include at least one second set of LEDs from among the plurality of LEDs, connected such that a constant current in the first set of LEDs is replicated to at least one second set of LEDs, and the second set of LEDs includes one or more LEDs.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 091,511, filed October 14, 2020, the entire disclosure of which is incorporated herein by reference.

Background Art

[0002] Light - emitting diodes (LEDs) used in automobiles and other applications often need to be driven at a constant current to meet optical and / or electrical design specifications and other requirements. In particular, in automotive applications, a constant - current state allows control of the light output from the LEDs over the range of ambient and operating temperatures expected during vehicle operation. Moreover, in the case of a variable power supply voltage that can deviate significantly from the nominal 12 volts depending on the battery design and degradation state, a constant current can control the light output from the LEDs.

[0003] Existing LED products for automotive and other applications may not use any constant current at all, in which case their performance is inferior. Others use multiple integrated circuits to drive multiple LEDs or a dedicated integrated circuit capable of driving multiple LEDs, increasing the cost of the product.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, what is needed is a low - cost electronic circuit design that can drive multiple LEDs at a constant current and has an integrated - circuit controller (or other device, circuit, or component arrangement) that provides a constant current to drive one LED (or some LEDs) and allows the current in one (or a few) LEDs to be copied (cloned) for other LEDs.

Means for Solving the Problems

[0005] Disclosed herein are examples of red, green, and blue (RGB) light-emitting diodes (LEDs) modules for use in automotive and other applications. Further disclosed are exemplary circuits in which specific current paths for driving RGB LEDs are cloned for each additional RGB LED. The LED circuit may include, for example, multiple LEDs, each having its own current path. A controller and associated software may be used to control the multiple LEDs.

[0006] Further disclosed herein are methods for controlling an RGB module by interfacing the module with an electronic system in an automobile or other system in which it is integrated.

[0007] In one embodiment, the module includes a plurality of LEDs, each having its own current path, and each LED is adapted to output user-selectable white or non-white light. Electrical connections are used to connect the module to an external electrical system for power and, optionally, control. Software stored in a storage medium device may be used to control the electrical signals to the plurality of LEDs. A first set of LEDs among the plurality may be red, blue, and green (RGB) LEDs, and each is connected to its respective transistor and current sink to drive a constant current through each of the RGB LEDs. A second set of LEDs, at least one of the plurality, is also an RGB LED, and is connected so that the constant current in the first set of LEDs is cloned to at least one of the second set of RGB LEDs.

[0008] In another embodiment, the LED circuit includes a plurality of LEDs, each having its own current path, each adapted to output user-selectable white or non-white light. A controller is used to control the plurality of LEDs. The controller may include software stored in a storage medium device. As described above, a current sink may be used to drive a constant current through the plurality of LEDs.

[0009] In yet another embodiment, the circuit design utilizes only low-cost, general-purpose components, such as low-cost transistor and resistor sets, to provide additional LED drive.

[0010] In another embodiment, the circuit can be adapted to an integrated circuit that supplies current by inverting the topology and changing the polarity of the transistor to NPN.

[0011] In yet another embodiment, the scaling granularity of the circuit from one set of LEDs to multiple sets can be considered "perfect" in that any particular number of LEDs being cloned does not result in any disadvantage or advantage, since one additional resistor and transistor may be required for each additional LED.

[0012] In addition, a multi-clone LED drive can be combined to drive high currents through a single high-power LED instead of multiple LEDs.

[0013] In another embodiment, the illustrated and described modules and circuits may be used to drive multiple LEDs with a constant current in any product, including those found in transportation systems (e.g., automobiles, railroads, and space), industrial systems, consumer products (e.g., amusement devices and household appliances), and medical devices that output or require lighting. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram of an RGB LED integrated circuit showing a primary RGB LED constant current circuit and two clone RGB LED circuits. [Figure 2] This is a schematic diagram of an LED integrated circuit showing a primary LED constant current circuit and N clone LED circuits. [Modes for carrying out the invention]

[0015] Referring to Figure 1, illustrated is an integrated circuit LED driver (U1) having at least three current sink pins or connections (i.e., current is returned to ground or regulated as it sinks), resistors R1 to R9, corresponding transistors Q1 to Q9, and corresponding LEDs identified as LED1 to LED9. While U1 is illustrated to have at least three current sink pins to correlate with the three LED channels of an RGB LED, this depiction is equally applicable to cloning current from one or more LEDs or LED channels. Similarly, not all LED channels connected to U1 need to be cloned (described later). However, for the purposes of this example disclosure, all three available LED channels for RGB will be cloned. In addition, the current sink does not need to be an integrated circuit and could be one or more individually designed current sinks, but for illustrative purposes, the following description will utilize the example of an integrated circuit current sink.

[0016] LED driver U1 is suitable for driving RGB array LEDs. It precisely sets the current through LED1, LED2, and LED3. The current setting mechanism may be an external resistor to the integrated circuit LED driver, or the current sink may be software controlled by a processor included in the integrated circuit LED driver.

[0017] The LED driver U1 may have three sync pins or connections for controlling a single RGB LED or three different LED channels of separate red, green, and blue LEDs. However, it should be understood that other controllers with more or fewer pins may also be used, as long as the LED driver U1 contains at least the number of pins corresponding to the number of LEDs or LED channels that will be directly controlled by U1. Furthermore, each of the LED channels directly controlled by U1 can be cloned to control additional LEDs, as described below, so the final number of controlled LEDs is not limited by the number of pins or LED channels.

[0018] The LED driver U1 can be used to sink a constant current through resistors R1, R2, and R3, for example, to U1 pin 1, U1 pin 2, and U1 pin 3 (not shown), respectively. Even due to the constant current sinking capability of the low-cost U1 controller, a precise constant voltage is generated across resistors R1, R2, and R3, which is optional and can be varied using the PWM duty cycle capability of the LED driver U1 to compensate for circuit differences.

[0019] Due to the illustrated series circuit arrangement, the current sink of the integrated circuit LED driver can set the current passing through PNP sensing transistors Q1, Q2, and Q3 in addition to resistors R1, R2, and R3.

[0020] Since the sensing transistors Q1, Q2, and Q3 are connected with their collector and base terminals as shown, the net collector-emitter voltage is equal to the base-emitter junction voltage for those transistors with respect to their specific currents (i.e., the LED drive currents I1, I2, and I3 set by the controller).

[0021] The resistor and base-emitter voltage drops across resistors R1, R2, and R3, and transistors Q1, Q2, and Q3, respectively, are connected to additional driver transistors and resistors associated with additional, for example, cloned RGB LEDs. For example, resistors R4, R5, and R6, and transistors Q4, Q5, and Q6 can set the LED drive currents to I4, I5, and I6, respectively. For example, the base-emitter voltage drop of Q1 is "reverse-flowed" through the base-emitter of transistor Q4 to resistor R4. The same applies to other LED channels. If the transistors and resistors of the cloned channels have the same values ​​as the original channels (i.e., those directly connected to U1 (Q1, Q2, Q3)), then the voltage drops across R4, R5, and R6 will be the same as those of R1, R2, and R3, respectively, and finally the currents I4, I5, and I6 will be cloned to I1, I2, and I3, respectively. Similarly, resistors R7, R8, and R9, as well as transistors Q7, Q8, and Q9, can set the LED drive currents to I7, I8, and I9. Thus, the current set by the integrated circuit is copied (cloned) to those additional transistor circuits as a result of "applying" the specific voltages resulting from the set currents flowing through the resistors and transistors across additional transistors of the same type and value. 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 temperature-compensating and other environmental effects on the base-emitter voltage of each transistor. For example, regardless of changes in the base-emitter voltage of Q1, its effect will be mitigated / compensated by Q4 in establishing the voltage drop across R4.

[0022] In practice, it should be noted that the resistors associated with the sensing transistors, i.e., those of the clone channels, are slightly higher in value than those associated with the drive (or direct) transistors (Q1, Q2, Q3). This is to compensate for the base current loss in the drive transistors. As an example, in the case of a 27 mA design, the difference in resistance values is exactly one step in the Electronic Industries Alliance (EIA) E96 resistance value table (137 ohms for the sense transistor resistor versus 133 ohms for the driver transistor resistor).

[0023] As described above, the circuit design of FIG. 1 is compatible with PWM.

[0024] Due to the series topology, the clone current is used to drive additional LEDs beyond the pin capacitance of the controller. By copying the base-emitter voltage for a particular current and applying it to the same type of transistor, it compensates for the temperature-induced change in VBE (the voltage drop between the base and emitter). The voltage occurring across the emitter resistor in the drive transistor circuit serves to mask the VBE voltage differences seen between individual transistors of the same type.

[0025] FIG. 2 is similar to FIG. 1, but instead of using RGB LEDs or individual red, green, and blue LEDs, only a single primary or direct drive LED using current I1 is shown, and secondary LEDs between one (LED2) and N (LEDN) each having currents I2 to IN are shown. Six secondary LEDs are shown with clone currents (I2, I3, I4, I5, I6, IN), but FIG. 2 shows that it can be expanded to N LEDs as symbolized by the ellipsis.

[0026] In use, electrical signals, including the sense current, in the above circuit can be managed by embedded software stored in a suitable memory device, for example, on the same printed circuit board as the circuit or on one or more separate but electrically coupled circuit boards. The present circuit can interface with an external circuit of, for example, an automotive electrical system using one or more suitable electrical connectors, including industry standard pins and socket connectors. The embedded software can include one or more suitable algorithms that can receive signals from an external circuit representing an input from a user, such as a vehicle operator, intended to change one or more conditions of the LEDs (e.g., increase brightness, change color mixing, etc.). The memory device can include specific settings as input to the software that establish the state of the circuit and its LEDs when the device in which the circuit is installed is first turned on, turned off, or in a particular operating condition (e.g., a vehicle operating during nighttime conditions).

[0027] While specific elements, embodiments, and uses of the invention have been illustrated and described, it will be understood that the invention is not limited thereto since modifications can be made by those skilled in the art without departing from the scope of the disclosure, particularly in view of the foregoing teachings.

Description of the Reference Numerals

[0028] I1 to IN LED drive current Q1 to QN Transistors R1 to RN Resistors U1 Integrated circuit LED driver / current sink

Claims

1. Light-emitting diode (LED) lighting module, A plurality of LEDs, each having its own current path, and each of the plurality of LEDs being adapted to output user-selectable white or non-white light, Electrical connections for connecting the module to an external electrical system, The system comprises software stored in a storage medium device for controlling electrical signals to the plurality of LEDs, A first set of LEDs from the plurality of LEDs is connected to a transistor and a current sink to drive a constant current through each of the LEDs in the first set, and the first set of LEDs includes one or more LEDs. At least one of the plurality of LEDs in the second set of LEDs is connected such that the constant current in the first set of LEDs is replicated to the at least one of the second set of LEDs, and the second set of LEDs includes one or more LEDs. Each of the aforementioned transistors comprises a first set of transistor bases and a first set of transistor collectors, each of the first set of transistor bases and first set of transistor collectors being electrically connected to each other, each of the second set of LEDs being connected to each of the second set of transistors, each of the second set of transistors comprising a second set of transistor bases and a second set of transistor collectors, at least one of the first set of transistor bases being electrically connected to at least one of the second set of transistor bases, and each of the first set of transistor bases being electrically connected to each of the second set of transistor bases. Light-emitting diode (LED) lighting module.

2. Light-emitting diode (LED) circuit, A plurality of LEDs, each having its own current path, and each of the plurality of LEDs being adapted to output at least one of white or non-white light, The system includes a controller for controlling the aforementioned multiple LEDs, A first set of LEDs from the plurality of LEDs is connected to each of a first set of transistors and a first current sink to drive a constant current through each of the first set of LEDs, and the first set of LEDs includes one or more LEDs. At least one of the plurality of LEDs in the second set of LEDs is connected such that the constant current in the first set of LEDs is replicated to the at least one of the second set of LEDs, and the second set of LEDs includes one or more LEDs. Each of the first set of transistors comprises a first set of transistor bases and a first set of transistor collectors, each of the first set of transistor bases and first set of transistor collectors is electrically connected to each other, each of the second set of LEDs is connected to each of the second set of transistors, each of the second set of transistors comprises a second set of transistor bases and a second set of transistor collectors, at least one of the first set of transistor bases is electrically connected to at least one of the second set of transistor bases, and each of the first set of transistor bases is electrically connected to each of the second set of transistor bases, LED circuit.

3. The LED circuit according to claim 2, wherein the controller includes software stored in a storage medium device.

4. The LED circuit according to claim 2, wherein the second set of LEDs is connected to a second current sink different from the first current sink.

5. The LED circuit according to claim 2, wherein the first current sink is an integrated circuit LED driver.

6. The LED circuit according to claim 5, wherein the current in the second set of LEDs is the second set of LED current, and the sum of the constant current passing through each of the first set of LEDs and the second set of LED current is greater than the current sink of the first current sink.

7. The LED circuit according to claim 5, wherein the integrated circuit LED driver has a plurality of current sink pins.

8. The LED circuit according to claim 6, wherein the integrated circuit LED driver has three current sink pins, the first set of LEDs comprises a red LED, a green LED, and a blue LED, and the second set of LEDs comprises at least one second set of red LEDs, at least one second set of green LEDs, and at least one second set of blue LEDs.

9. The LED circuit according to claim 6, wherein the combined number of the first set of LEDs and the second set of LEDs is greater than the number of current sink pins.

10. The LED circuit according to claim 2, wherein each of the second set of transistors comprises a second set of transistor emitters, and the second set of transistor emitters is electrically connected to a voltage source through a sense transistor resistor.

11. The LED circuit according to claim 10, wherein each of the first set of transistors comprises a first set of transistor emitters, and the first set of transistor emitters are electrically connected to the voltage source through their respective driver transistor resistors.

12. The LED circuit according to claim 11, wherein the driver transistor resistor has a driver transistor resistance, the sense transistor resistor has a sense transistor resistance, and the driver transistor resistance is substantially the same as the sense transistor resistance.

13. The LED circuit according to claim 12, wherein the driver transistor resistor has a driver transistor resistor voltage drop, the sense transistor resistor has a sense transistor resistor voltage drop, and the driver transistor resistor voltage drop and the sense transistor resistor voltage drop are substantially equal.

14. The LED circuit according to claim 11, wherein the driver transistor resistor has a driver transistor resistance, and the sense transistor resistor has a sense transistor resistance, and the sense transistor resistance is higher than the driver transistor resistance.

15. The LED circuit according to claim 14, wherein the sense transistor resistance is approximately one step higher than the driver transistor resistance in the EIA E96 resistance table.

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