RGB control system based on constant current circuit

Abstract

An RGB control system based on a constant current circuit is characterized in that an LED driver is arranged, a driving end group of the LED driver drives LED lamp beads to work through an LED driving circuit, a constant current control end of the LED driver is connected with an external constant current source circuit, and the external constant current source circuit is further connected with the LED driving circuit; a signal receiving and transmitting end group of the LED driver is connected with an upper computer through an LIN bus, the upper computer obtains a temperature signal of the LED driver and sends the temperature signal to the LED driver, and the LED driver adjusts PWM duty ratio output of a constant current control end according to the temperature signal. The LED driver has the advantages that the triode is used for building the external constant current source circuit, driving control over the LED lamp beads is achieved according to the temperature state of the LED driver, and loss of the temperature of the LED driver to peripheral components and structural parts is effectively reduced.

Description

Technical Field

[0001] This utility model relates to the field of LED control technology, and in particular to an RGB control system based on a constant current circuit. Background Technology

[0002] With the rapid development of LED display technology, LED displays have been widely used in various scenarios, such as advertising screens, video walls, and public information displays, offering advantages such as small size, low power consumption, and long lifespan. However, as a semiconductor light-emitting element, LEDs are susceptible to factors such as heat load and excessive current during prolonged use, leading to open circuits or short circuits, resulting in abnormalities or dead pixels on the display screen and severely affecting the display effect. Improving the stability of LED display control and implementing fault detection and response remains a current technical challenge.

[0003] When controlling lighting equipment, a constant voltage and constant current power supply is usually used to ensure the stability of the light emission.

[0004] Disadvantages of existing technology: Traditional LED circuits generally use built-in constant current sources, but when the LED brightness is high, the built-in constant current source will be limited by the size of the chip, resulting in excessively high local temperature of the chip, which will lead to the failure of the control circuit. Utility Model Content

[0005] This invention provides an RGB control system based on a constant current circuit, which can reduce the wear and tear on various components of the system caused by chip temperature.

[0006] To achieve the above objectives, this utility model provides an RGB control system based on a constant current circuit. The key features are: an LED driver is provided, the driving terminal of which drives the LED beads through the LED driving circuit, and the constant current control terminal of the LED driver is connected to an external constant current source circuit, which is also connected to the LED driving circuit.

[0007] The signal transceiver group of the LED driver is connected to the host computer via a LIN bus. The host computer acquires the temperature signal of the LED driver and sends the temperature signal to the LED driver. The LED driver adjusts the PWM duty cycle output of the constant current control terminal according to the temperature signal.

[0008] Through the above design, the overall control of the LED bead's on / off state is achieved by setting an external constant current source circuit. The host computer obtains the temperature signal of the LED driver and sends it to the LED driver. The LED driver realizes the derating and recovery control of the PWM duty cycle of the constant current control terminal according to the temperature signal, thereby reducing the wear and tear of temperature on the peripheral components and structural parts of the LED driver, improving system stability, and extending the system's service life.

[0009] Because the LED driver and the LED chips are close together, the temperature of the LED driver is the same as that of the LED chips. By obtaining the temperature of the LED driver, the temperature of the LED chips can be understood. The LED driver adjusts the PWM duty cycle output of the constant current control terminal, thereby regulating the temperature of the LED chips and preventing the LED driver and LED chips from overheating and causing damage to surrounding components and structural parts.

[0010] Preferably, the external constant current source circuit includes a resistor R5. The front end of resistor R5 is connected to the constant current control terminal of the LED driver, and the rear end is connected to the base of an NPN transistor Q3. The collector of transistor Q3 is connected to the LED driver circuit. The emitter of transistor Q3 is connected to ground via a resistor R7. The emitter of transistor Q3 is also connected to ground via a capacitor C6. The emitter of transistor Q3 is also connected to the base of an NPN transistor Q2A. The collector of transistor Q2A is connected to the base of transistor Q3, and the emitter of transistor Q2A is grounded.

[0011] The working principle of the external constant current source circuit is as follows:

[0012] When the constant current control terminal of the LED driver outputs a high level, transistor Q3 is turned on. The collector current of transistor Q3 equals the base current plus the emitter current. Since the base current of transistor Q3 is very small, the collector current and emitter current of Q3 are almost equal.

[0013] When transistor Q3 is turned on, transistor Q2A is also turned on. The voltage between the base and emitter of transistor Q2A is stable at 0.7V, and the voltage across R7 is also constant at 0.7V. Therefore, the current through R7 is constant at 0.7 / R7. The emitter current of transistor Q3 = the base current of transistor Q2A + the current through R7. Since the base current of Q2A is in the μA range, which is very small, the emitter current of transistor Q3 is approximately equal to the current through R7.

[0014] Therefore, the collector current of transistor Q3 is approximately equal to the current through R7, i.e., 0.7V / R7, so the current through the LED is constant.

[0015] Preferably, the driving end group of the LED driver includes an RLED driving end, a GLED driving end and a BLED driving end, and the LED beads include RLED beads, GLED beads and BLED beads.

[0016] The LED driving circuit is equipped with a resistor R2. The front end of the resistor R2 is connected to the GLED driving terminal, and the rear end of the resistor R2 is connected to the base of a PNP transistor Q1A. The emitter of the transistor Q1A is connected to the power supply. The emitter of the transistor Q1A is also connected to the anode of the GLED lamp bead, and the cathode of the GLED lamp bead is connected to the collector of the transistor Q1A.

[0017] The collector of transistor Q1A is also connected to the emitter of PNP transistor Q1B. The emitter of transistor Q1B is also connected to the anode of RLED lamp bead. The cathode of RLED lamp bead is connected to the collector of transistor Q1B. The base of transistor Q1B is connected to the RLED driving terminal via resistor R3.

[0018] The collector of transistor Q1B is also connected to the emitter of PNP transistor Q2B. The emitter of transistor Q2B is also connected to the anode of the BLED lamp bead. The cathode of the BLED lamp bead is connected to the collector of transistor Q2B. The collector of transistor Q2B is also connected to the external constant current source circuit. The base of transistor Q2B is connected to the BLED driving terminal via resistor R4.

[0019] With the above design, when the output of the driving terminal group of the LED driver is a high signal, transistors Q1A, Q1B, and Q2B are turned off, and current flows through the LED beads, resulting in the light being on; when the output of the driving terminal group of the LED driver is a low signal, transistors Q1A, Q1B, and Q2B are turned on, and the LED beads are short-circuited, resulting in the light being off.

[0020] The three RGB channels are controlled independently, and the turning off of all the lights is controlled by an external constant current source circuit.

[0021] Regardless of whether the LED is on or off, the power consumption of the entire driving circuit depends on the external constant current source circuit. When the host computer detects that the LED is off or has extremely low brightness, it needs to turn off the external constant current source circuit to reduce power consumption.

[0022] Preferably, a power protection circuit is also provided between the LED driving circuit and the power supply;

[0023] The power protection circuit includes a resistor R1. The front end of the resistor R1 is connected to the power supply. The front end of the resistor R1 is connected in series with capacitors C1 and C4 and then grounded. The rear end of the resistor R1 is connected to the anode of diode D1. The cathode of diode D1 is connected to the LED driving circuit. The cathode of diode D1 is connected in series with capacitor C3 and then grounded. The cathode of diode D1 is also connected to the power supply terminal of the LED driver.

[0024] The capacitors C1 and C4 are used for filtering, the diode D1 is used for reverse protection, and the resistor R1 is used for surge current protection.

[0025] Preferably, a filter circuit is provided between the LED driver and the host computer, and the filter circuit is provided with bidirectional Zener diode D2, bidirectional Zener diode D3, ferrite bead FB1, ferrite bead FB2, capacitor C2, capacitor C5 and resistor R6.

[0026] The front end of the magnetic bead FB1 is connected to the signal output terminal of the host computer. The front end of the magnetic bead FB1 is also connected in series with a bidirectional Zener diode D2 and then grounded. The rear end of the magnetic bead FB1 is connected to the signal receiving terminal IN of the LED driver. The rear end of the magnetic bead FB1 is also connected in series with a capacitor C2 and then grounded.

[0027] The front end of the magnetic bead FB2 is connected to the signal input terminal of the host computer. The front end of the magnetic bead FB2 is also connected in series with a bidirectional Zener diode D3 and then grounded. The rear end of the magnetic bead FB2 is connected to the signal transmitting terminal OUT of the LED driver. The rear end of the magnetic bead FB2 is also connected in series with a capacitor C5 and then grounded.

[0028] A resistor R6 is connected in series between the rear ends of the magnetic beads FB1 and FB2.

[0029] The filtering circuit is used to filter the interaction signals between the LED driver and the host computer to improve signal quality.

[0030] Preferably, the LED driver has a built-in temperature sensor, which sends a temperature signal to the host computer through the LED driver's signal transmitting terminal OUT.

[0031] The temperature sensor is used to acquire the temperature signal of the LED driver in real time.

[0032] The beneficial effects of this utility model are: using a transistor to build an external constant current source circuit, and realizing the driving control of LED beads according to the temperature state of the LED driver, effectively reducing the damage of the LED driver temperature to surrounding components and structural parts. Attached Figure Description

[0033] Figure 1 This is a structural block diagram of the present invention;

[0034] Figure 2 This is a circuit diagram of an external constant current source circuit and an LED driver.

[0035] Figure 3 Schematic diagram of LED driver;

[0036] Figure 4 Diagram of power protection circuit and filter circuit;

[0037] Figure 5 This is a flowchart illustrating the PWM duty cycle control of the LED driver in this embodiment. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific examples. The following embodiments or drawings are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0039] Example 1:

[0040] like Figure 1 As shown: An RGB control system based on a constant current circuit is provided, which is equipped with an LED driver. The driving terminal of the LED driver drives the LED beads to work through the LED driving circuit. The constant current control terminal of the LED driver is connected to an external constant current source circuit, which is also connected to the LED driving circuit.

[0041] The signal transceiver group of the LED driver is connected to the host computer via a LIN bus. The host computer acquires the temperature signal of the LED driver and sends the temperature signal to the LED driver. The LED driver adjusts the PWM duty cycle output of the constant current control terminal according to the temperature signal.

[0042] like Figure 2 , Figure 3 As shown: The external constant current source circuit is equipped with resistor R5. The front end of resistor R5 is connected to the constant current control terminal of the LED driver, and the rear end is connected to the base of NPN transistor Q3. The collector of transistor Q3 is connected to the collector of transistor Q2B. The emitter of transistor Q3 is connected to ground in series with resistor R7. The emitter of transistor Q3 is also connected to ground in series with capacitor C6. The emitter of transistor Q3 is also connected to the base of NPN transistor Q2A. The collector of transistor Q2A is connected to the base of transistor Q3, and the emitter of transistor Q2A is grounded.

[0043] The driving end group of the LED driver includes an RLED driving end, a GLED driving end and a BLED driving end, and the LED beads include RLED beads, GLED beads and BLED beads.

[0044] The LED driving circuit is equipped with a resistor R2. The front end of the resistor R2 is connected to the GLED driving terminal, and the rear end of the resistor R2 is connected to the base of a PNP transistor Q1A. The emitter of the transistor Q1A is connected to the power supply. The emitter of the transistor Q1A is also connected to the anode of the GLED lamp bead, and the cathode of the GLED lamp bead is connected to the collector of the transistor Q1A.

[0045] The collector of transistor Q1A is also connected to the emitter of PNP transistor Q1B. The emitter of transistor Q1B is also connected to the anode of RLED lamp bead. The cathode of RLED lamp bead is connected to the collector of transistor Q1B. The base of transistor Q1B is connected to the RLED driving terminal via resistor R3.

[0046] The collector of transistor Q1B is also connected to the emitter of PNP transistor Q2B. The emitter of transistor Q2B is also connected to the anode of the BLED lamp bead. The cathode of the BLED lamp bead is connected to the collector of transistor Q2B. The collector of transistor Q2B is also connected to the external constant current source circuit. The base of transistor Q2B is connected to the BLED driving terminal via resistor R4.

[0047] like Figure 3 , Figure 4 As shown: A power protection circuit is also provided between the LED driving circuit and the power supply;

[0048] The power protection circuit includes a resistor R1. The front end of the resistor R1 is connected to the power supply. The front end of the resistor R1 is connected in series with capacitors C1 and C4 and then grounded. The rear end of the resistor R1 is connected to the anode of diode D1. The cathode of diode D1 is connected to the emitter of transistor Q1A. The cathode of diode D1 is connected in series with capacitor C3 and then grounded. The cathode of diode D1 is also connected to the power supply terminal of the LED driver.

[0049] A filter circuit is provided between the LED driver and the host computer. The filter circuit includes a bidirectional Zener diode D2, a bidirectional Zener diode D3, a ferrite bead FB1, a ferrite bead FB2, a capacitor C2, a capacitor C5, and a resistor R6.

[0050] The front end of the magnetic bead FB1 is connected to the signal output terminal of the host computer. The front end of the magnetic bead FB1 is also connected in series with a bidirectional Zener diode D2 and then grounded. The rear end of the magnetic bead FB1 is connected to the signal receiving terminal IN of the LED driver. The rear end of the magnetic bead FB1 is also connected in series with a capacitor C2 and then grounded.

[0051] The front end of the magnetic bead FB2 is connected to the signal input terminal of the host computer. The front end of the magnetic bead FB2 is also connected in series with a bidirectional Zener diode D3 and then grounded. The rear end of the magnetic bead FB2 is connected to the signal transmitting terminal OUT of the LED driver. The rear end of the magnetic bead FB2 is also connected in series with a capacitor C5 and then grounded.

[0052] A resistor R6 is connected in series between the rear ends of the magnetic beads FB1 and FB2.

[0053] The LED driver has a built-in temperature sensor, which sends a temperature signal to the host computer through the LED driver's signal transmitting terminal OUT.

[0054] like Figure 5 As shown: The host computer establishes a derating task for periodic scheduling, determines the derating level by acquiring the temperature of the LED driver, obtains the PWM duty cycle value based on the derating level, and outputs it at the constant current control terminal.

[0055] The derating control logic in Example 1 is as follows:

[0056] When the detected temperature of the LED driver is <105℃, the derating level is 0, and the PWM duty cycle is 100%.

[0057] When the temperature of the LED driver is detected to be ≥105℃ and <110℃ for 5 seconds, the derating level is 1, at which point the PWM duty cycle is directly reduced from 100% to 80%.

[0058] When the temperature of the LED driver is detected to be ≥110℃ and <115℃ for 5 seconds, the derating level is 2, at which point the PWM duty cycle is directly reduced from 80% to 60%.

[0059] When the temperature of the LED driver is detected to be ≥115℃ and <120℃ for 5 seconds, the derating level is 3, at which point the PWM duty cycle is directly reduced from 60% to 40%.

[0060] When the temperature of the LED driver is detected to be ≥120℃ and lasts for 5 seconds, the derating level is 4, at which point the PWM duty cycle is directly reduced from 40% to 0.

[0061] The control recovery logic is as follows:

[0062] When the derating level is 4, if the temperature of the LED driver is detected to be ≥115℃ and <120℃ for 5 seconds, the derating level will be restored to 3. At this time, the PWM duty cycle will be restored directly from 0 to 40%.

[0063] When the derating level is 3, if the temperature of the LED driver is detected to be ≥110℃ and <115℃ for 5 seconds, the derating level will be restored to 2. At this time, the PWM duty cycle will be restored directly from 40% to 60%.

[0064] When the derating level is 2, if the temperature of the LED driver is detected to be ≥105℃ and <110℃ for 5 seconds, the derating level will be restored to 1. At this time, the PWM duty cycle will be restored directly from 60% to 80%.

[0065] When the derating level is 1, if the temperature of the LED driver is detected to be <105℃ for 5 seconds, the derating level will be restored to 0, and the PWM duty cycle will be restored directly from 80% to 100%.

[0066] Example 2:

[0067] Example 2 is based on Example 1, but differs in that:

[0068] The derating control logic in Example 2 is as follows:

[0069] When the detected temperature of the LED driver is <110℃, the derating level is 0, and the PWM duty cycle is 100%.

[0070] When the detected temperature of the LED driver is ≥110℃, the derating level is set to level 1. At this time, the PWM duty cycle gradually changes from 100% to 80% (the change time is set according to the user's change signal).

[0071] With derating level 1, when the temperature of the LED driver is detected to be ≥110℃ and lasts for 10 seconds, the derating level is 2, at which point the PWM duty cycle gradually changes from 80% to 60%.

[0072] With derating level 2, when the temperature of the LED driver is detected to be ≥110℃ and lasts for 10 seconds, the derating level becomes level 3, at which point the PWM duty cycle gradually changes from 60% to 50%.

[0073] With a derating level of 3, when the temperature of the LED driver is detected to be ≥110℃ and lasts for 10 seconds, the derating level becomes 4, at which point the PWM duty cycle gradually changes from 50% to 30%.

[0074] With a derating level of 4, when the temperature of the LED driver is detected to be ≥120℃, the derating level becomes 5, and the PWM duty cycle gradually changes from 30% to 0.

[0075] The control recovery logic is as follows:

[0076] When the temperature of the LED driver is detected to be ≤105℃, the recovery control logic is entered.

[0077] When the derating level is 5, if the temperature of the LED driver is detected to be ≤105℃ for one minute, the derating level is restored to 4, at which point the PWM duty cycle gradually changes from 0 to 30%.

[0078] When the derating level is 4, if the temperature of the LED driver is detected to be ≤105℃ for one minute, the derating level is restored to 3, at which point the PWM duty cycle gradually changes from 30 to 50%.

[0079] When the derating level is 3, if the temperature of the LED driver is detected to be ≤105℃ for one minute, the derating level is restored to 2. At this time, the duty cycle of the PWM gradually changes from 50 to 60%.

[0080] When the derating level is 2, if the temperature of the LED driver is detected to be ≤105℃ for one minute, the derating level is restored to 1. At this time, the duty cycle of the PWM gradually changes from 60 to 80%.

[0081] When the derating level is 1, if the temperature of the LED driver is detected to be ≤105℃ for one minute, the derating level is restored to 0, at which point the PWM duty cycle gradually changes from 80 to 100%.

[0082] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. An RGB control system based on a constant current circuit, characterized in that: An LED driver is provided, and the driving terminal group of the LED driver drives the LED beads to work through the LED driving circuit. The constant current control terminal of the LED driver is connected to an external constant current source circuit, which is also connected to the LED driving circuit. The signal transceiver group of the LED driver is connected to the host computer via a LIN bus. The host computer acquires the temperature signal of the LED driver and sends the temperature signal to the LED driver. The LED driver adjusts the PWM duty cycle output of the constant current control terminal according to the temperature signal.

2. The RGB control system based on a constant current circuit according to claim 1, characterized in that: The external constant current source circuit includes a resistor R5. The front end of resistor R5 is connected to the constant current control terminal of the LED driver, and the rear end is connected to the base of an NPN transistor Q3. The collector of transistor Q3 is connected to the LED driver circuit. The emitter of transistor Q3 is connected to ground via a resistor R7 in series. The emitter of transistor Q3 is also connected to ground via a capacitor C6 in series. The emitter of transistor Q3 is also connected to the base of an NPN transistor Q2A. The collector of transistor Q2A is connected to the base of transistor Q3, and the emitter of transistor Q2A is grounded.

3. The RGB control system based on a constant current circuit according to claim 1 or 2, characterized in that: The driving end group of the LED driver includes an RLED driving end, a GLED driving end and a BLED driving end, and the LED beads include RLED beads, GLED beads and BLED beads. The LED driving circuit is equipped with a resistor R2. The front end of the resistor R2 is connected to the GLED driving terminal, and the rear end of the resistor R2 is connected to the base of a PNP transistor Q1A. The emitter of the transistor Q1A is connected to the power supply. The emitter of the transistor Q1A is also connected to the anode of the GLED lamp bead, and the cathode of the GLED lamp bead is connected to the collector of the transistor Q1A. The collector of transistor Q1A is also connected to the emitter of PNP transistor Q1B. The emitter of transistor Q1B is also connected to the anode of RLED lamp bead. The cathode of RLED lamp bead is connected to the collector of transistor Q1B. The base of transistor Q1B is connected to the RLED driving terminal via resistor R3. The collector of transistor Q1B is also connected to the emitter of PNP transistor Q2B. The emitter of transistor Q2B is also connected to the anode of the BLED lamp bead. The cathode of the BLED lamp bead is connected to the collector of transistor Q2B. The collector of transistor Q2B is also connected to the external constant current source circuit. The base of transistor Q2B is connected to the BLED driving terminal via resistor R4.

4. The RGB control system based on a constant current circuit according to claim 3, characterized in that: A power protection circuit is also provided between the LED driver circuit and the power supply. The power protection circuit includes a resistor R1. The front end of the resistor R1 is connected to the power supply. The front end of the resistor R1 is connected in series with capacitors C1 and C4 and then grounded. The rear end of the resistor R1 is connected to the anode of diode D1. The cathode of diode D1 is connected to the LED driving circuit. The cathode of diode D1 is connected in series with capacitor C3 and then grounded. The cathode of diode D1 is also connected to the power supply terminal of the LED driver.

5. The RGB control system based on a constant current circuit according to claim 1, characterized in that: A filter circuit is provided between the LED driver and the host computer. The filter circuit includes a bidirectional Zener diode D2, a bidirectional Zener diode D3, a ferrite bead FB1, a ferrite bead FB2, a capacitor C2, a capacitor C5, and a resistor R6. The front end of the magnetic bead FB1 is connected to the signal output terminal of the host computer. The front end of the magnetic bead FB1 is also connected in series with a bidirectional Zener diode D2 and then grounded. The rear end of the magnetic bead FB1 is connected to the signal receiving terminal IN of the LED driver. The rear end of the magnetic bead FB1 is also connected in series with a capacitor C2 and then grounded. The front end of the magnetic bead FB2 is connected to the signal input terminal of the host computer. The front end of the magnetic bead FB2 is also connected in series with a bidirectional Zener diode D3 and then grounded. The rear end of the magnetic bead FB2 is connected to the signal transmitting terminal OUT of the LED driver. The rear end of the magnetic bead FB2 is also connected in series with a capacitor C5 and then grounded. A resistor R6 is connected in series between the rear ends of the magnetic beads FB1 and FB2.

6. The RGB control system based on a constant current circuit according to claim 5, characterized in that: The LED driver has a built-in temperature sensor, which sends a temperature signal to the host computer through the LED driver's signal transmitting terminal OUT.

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